Download deposition of a wide by the geotectonic intraplate - UvA-DARE

LEIDSE GEOLOGISCHE
Framework
and
MEDEDELINGEN, Deel
evolution of
Hercynian
52,
Aflevering
1,
pp.
mineralization in
23-56,
the
1-7-1981
Iberian
Meseta
BY
L.J.
G.
Schermerhorn
Abstract
The
Hercynian cycle, starting
deposition
of
Belt
Pyrite
The
a
wide
(Rio
Tinto
depositional
and
other
of
stage
magmatic activity, mostly
as
magmatism was
Framework and evolution
by
its
and
heat
and
mass
Metallogenetic provinces
and
direct
of
tin
Hercynian
volcanic
deposits
the dominant
palaeogeographicaland
plutonic
and nonmetallic
deposits),
the
palaeogeographical, sedimentary
stages felsic
times and terminated at the end ofthe Palaeozoic,
in Late Precambrian
of metallic
variety
tungsten
controls.
from
and
accumulation
of
During
and
magmatic-derived
mineralization
are
developmentduring
The most famous
(Panasqueira),
the
saw
resources.
agent of mineralization,
Hercynian
structural
and
cycle
mineral
fluids and
both for the
defined
the
after the
mercury
mineral
following orogenic
modified
sulphides
by regional
not
and local
from
resulting
epigenetic
important volcanogenic
by the geotectonic intraplate —
cycle,
deposits,
stage,
indirectly through thermal
more
in the Iberian Peninsula with
the base-metal
are
the
of the Iberian
(Almadén).
syngenetic
also
is associated
of these
minerals
activation
and for the
plate-margin
-
of
the
interplay
existing
plutonic
setting
rock. In both
mineral
deposits.
of the Meseta and
foremost among which
factors,
of
originated through
are
volcanic
transfer.
and
epochs
are
distinguished,
metallotects outlined,
and
possible
for the introduced
sources
ore
elements
discussed.
Contents
24
Introduction
(jcotcctonic and
structural
24
setting
Middle
Precambrian
Late
24
Precambrian
(?) copper
sulphides
Hercynian
Middle to
27
scheelite
Cambrian
lead-zinc
Cambrian
(?)
Cambrian
iron
Early
28
sulphides
chromium
Ordovician
37
Carboniferous
Upper
Hercynian
later
orogeny:
stratabound
29
Hcrcynian Younger
29
Autunian
tin
Autunian
beryl,
3D
Autunian
gold
and
31
Autunian
and
Autunian
phosphate
base-metal
Silurian
scheelite
sulphides
and
magnetite
Late
Late to
31
bismuth
32
Late
32
Devonian
Palaeozoic
to
Middle
Carboniferous
Early Carboniferous
Prof.
and
feldspar
.
44
45
gold
lead,
44
46
zinc and silver
47
chromium
48
and nickel
cobalt,
nickel and
48
48
Hercynian f'erromanganese
AuUinian
(?)
Autunian
(?) epigenetic
49
mercury
Autunian
fluorite
uranium
and
baritc
49
49
32
base-metal
sulphides:
the Iberian
Pyrite
Belt
Early
and
post-Hercynian epigenetic copper,
Remobilized
Early
later
lithium
silver
antimony
31
39
columbite-tantalite,
Ordovician
31
38
and tungsten
antimony
Almadén
38
fluorite
Granites
Autunian
Silurian
38
38
Autunian
30
mercury:
37
phases
Permian
29
iron
Silurian
37
Older Granites
Ordovician
Silurian
*)
talc
28
mercury
Palaeozoic
36
phase
24
Cambrian
Cambrian
the main
orogeny:
Westphalian
Late
36
Carboniferous
Hcrcynian
Synthesis
50
References
53
32
Carboniferous
Dr.
Universitàt
L.
J.
Berlin,
36
manganese
G. Schermerhorn,
Takustrasse
6.
Institut
D-1000
für
Berlin
Mineralogie,
33.
B.R.D.
Freie
24
INTRODUCTION
change from
within each
The Iberian
a
Peninsula
large part of which
is well
created
were
that is. the
geological cycle
tectonism
leading
minates
the cycle
Iberian Meseta,
the Peninsula,
deposits.
mineral
the
to
of the
queira
representative,
the most
as
East, and the
Two
I).
ter-
The
large part of
a
Hercynian
Three world-famous Iberian
Hercynian cycle spring
celebrated
which
orogeny
Palaeozoic (Fig.
mind: the base-metal sul-
to
Belt, with
the
belonging
ores
Rio
Tinto as their
tin-tungsten
with
belt,
most
Panas-
important tungsten mine outside
the
Far
of Almadén.
mercury
factors dominate the
of mineral
context
deposition
They
in
throughout,
The
was
and,
second, extensive granitic intrusion.
depositional
mineral
ranging
resources,
o r
deformed,
o
i
e n
g
géosynclinal rocks
served
genetic mineral deposits,
Iberian
tin
and
deposits
are
the
result
plutonic deposits
mineral
the
some
vastest
mercury
of epi-
to the
of
were
palaeogeographical.
the
thermal activation
a
great variety
massive
largest
and
directly
ol'
grand scale indeed: the
a
mine
Panasqueira
Europe,
and
the orogenic
produced
on
famed
mineral
géosynclinal
from magmatic activity,
of them
the
in
tungsten producer
The
were
deformed
range
barite and fluorite
contains
world,
During the
The
wide
a
indirectly through
or
Belt
Pyrite
in
to
controls, and
arose
iron-
sedimentary
sulphides.
of the interplay
materials. Thus
deposits,
Iberian
bodies
from
volcanic
postorogenic minerals
existing
sulphide
is
the
is
by
Almadén
largest
far
the
concentration known.
and North Africa is of
a
different type than the evolution of
Alpine and other orogens related
duction,
though
number
of
ultramafic
ophiolite,
this
however
difference
is
rocks
an
in
oceanic
to
endlessly
of which
and
is.
still
is undeniable
one
ways,
that
of nickel
different tectonic,
The
is
as
it
makes
the
crust
point.
The
Hercynian
yet
zonation
and chromium,
and
structural
been
less
stable
across
point
years
out
the
since it
that
2
-
this
(1974)
more
less
or
styles together
follows the
figure
of
and
Lotze's
original
Positive
time
one
of the
epeirogenic
turn
may
basement
after,
soon
consequence, formation thicknesses
in
1
(Fig.
on
or
the
underlying
in
region
a
and
so
all
on.
at
In
between
greatly
can vary
Moreover, volcanism took place
the Precambrian and Cambrian
more
uplifts, evidencing
movements
negative
to
multiplex,
a
was
of subsiding basins,
geanticlinal
pronounced vertical mobility
geosyncline.
Iberia
in
geosyncline
platforms
LATE
periods from
).
PRECAMBRIAN
the
absence
complexes. As
are rare
Hercynian cycle in the
a
the
palaeogeographical:
orogenic
was
in
a
of
true
result, the
a
very
as
the
Lotze's
first propounded.
Meseta
complex and
is
a
cleareut
well-known
has suffered little
sedimentary
begins
the
when
on
some
time during the Late
in
several places in the
Precambrian.
Upper Precambrian
Meseta.
Negra',
In the
strata
south they
crop
and lenses of black quartzites
and
wacke
locally
or
even
successions
Cambrian
volcanics
or
at
'Serie
la
vers
limestone.
some
top
is
of
the
conformable, discon-
unconformable. Similar
appear
elsewhere
the
in
probable Cambrian beds and
or
the
thin
the
at
appear
Lower Cambrian, and the junction
Ibrmable
as
1974). The Serie Negra is overlain by the
(Vegas,
sequence
generically
cherts, and
intermediate volcanics
Locally
out
known
are
slate-grcywacke succession containing
a
their top. Little
near
is
slate-grey-
Meseta
may
below
contain
known
felsic
yet of
as
the
between the Upper Precambrian successions and
relationship
the older schists and gneisses of
the
to the
crystalline basement
Hercynian geosyncline.
No syngenetic mineralizationshave
wacke lithology
the
been
recorded from the
deposits
orebodics
important
at
with
the
Arinteiro and
their
of
ores
known
slate-grey-
does
flysch-like
of synsedimentary
occurrence
are
called
often
Late
Precambrian (?)
The
A
i
r
deposits
n t e
near
tation since
i
r o
from
not
favour
importance.
any
the
of
possible exception
volcanic
the
copper
Fornás.
change
Julivert et al.
these
facies
zones
and
is
(
in
1974)
essentially
thicknesses
copper
and
sulphides
Fornás
cupriferous
1975,
with
are
metamorphosed sulphide
The
complex.
hornblende granulite facies,
rocks
were
lower
paragneiss
to
van
levels.
and
lenses
ores
underwent
and schist (mostly
Its
age
is
considered
black
pers.
the
to
suffering rétrogradation
The
in-
the polymeta-
to
the
Ordenes complex
original greywackes
Zuuren ( 1969)) enclosing amphibolites
Precambrian (E. Den Tex,
thin beds of
in
metamorphosed
amphibolitc facies (van Zuuren. 1969).
consists of
pyrrhotite
Galicia, in exploi-
garnetiferous amphibolites
polyphase deformation and
according
in
Santiago de Compostela
morphic Ordenes
trend.
significance of
Peninsula
floor of older Precambrian rocks,
Nor
in the Iberian Meseta.
unravelled. There
zones which
Iberian
Hercynian geosyncline formed and sedimentation started,
intercalations,
setting
completely
subdivision into six
the 34
al.
et
shifting assemblage
ceaselessly
sub-
itself fell
sedimentary, volcanic and tectonic history of the
not
Julivert
by
also
and magmatic
scarcity of Hercynian
particular
during the Precambrian and Palaeozoic is
has
constant
represent
zones
scheme).
terbedded
Geotectonic
to remain
facies but
metamorphic
with different mineralizations (Fig.
adaptation
This
lithosphère
debated
minerals associated with ultramafic magmatism. such
ores
tend
Upper Preeambrian (meta) sediments, and
Hercynian géosynclinal and orogcnic evolution in Europe
the
and sedimentary
stratigraphie
The
geosyncline
accumulation of
intruded.
hosts
as
tungsten lodes.
sedimentary and
of
and
metamorphosed
the
the earlier deposits
stage
e
the
from
volcanogenic polymetallic
to
subsequent
as
when
stage,
the setting for
syngenetic
another but
Precambrian times, with volcanism occurring
being filled, provided
stone
to
that is, along the strike. The
are,
first, the long-drawn evolution of the Hercynian geosyncline.
Late
zone
only different palaeogeographical domains and different
regions.
Iberian Peninsula during the Hercynian cycle.
starting in
not
oro-
great variety ofmetallic and nonmetallic
a
phides of the Iberian Pyrite
the
Hercynian
end
consolidated during the
was
resources,
the Hercynian cycle,
during
Hesperic Massif, occupying
or
It is the site of
geny.
the
mineral
of sedimentation, magmatism and
the
to
up
at
endowed with
one
zone,
to
comm.).
be
probably
in
The occurrence
quartzite (van Zuuren's
the
Late
of
graphite-bearing
25
Fig.
1.
Generalized
section
illustrating timing
and
evolution
of mineralization
in
the Iberian
Meseta.
26
Fig.
2.
schists) does in fact
Serie
in
Principal metallogenetic provinces
recall
the black
Negra (unless they
the Iberian
quartzites
Meseta.
and cherts of the
metamorphosed Silurian black
are
At
cherts).
At
Fornás three stacked
massive
together
enclosed
sulphides (pyrrhotite
30
thick
m
with
sharp
by
a
contacts
a
much
andjjyrite
of
an
disseminated
to
with chalcopyrite and
strike
bolite. They total 750,000
teiro is
lenses of
in
length
of about
fairly
pyrite),
200 m,
are
unmineralized garnet amphi-
tonnes
grading 1.02% Cu.
Arin-
larger orebody of pyrrhotite with chalcopyrite
disseminated in garnet amphibolite in the
anticlinorium.
The
west
flank
contains
east
a
flank
similar
Bama.
orebody.
in
places
this
Arinteiro and
level
particular
three
Sulphide mineralization
structure
of
as
well
sulphide deposits add
ore
reserves
Fornás
ore
is
20
den, pers.
much
30%
S
coram.),
minerals such
as
with little garnet
et
is
found
al..
Bama the mineralization
garnet amphibolite
copper
grading
(Chabod
up
to
almost 25
grading 0.66",, Cu
more
as
is
is
m
linked
thick.
million
(White.
to
a
The
tonnes of
1977a). The
S for Arinteiro (N. Rho-
still moderately diluted by
anthophyllite
(Ypma.
other
massive than Arinteiro and Bama.
against 5-7%
but
20-80
in
1976).
or
1966).
gedrite
and
gangue
other silicates,
27
From their
field
aspect and
sulphide with chalcopyrite
be
to
appear
their simple composition (iron
and
little else),
stratabound
syngenetic
original
in
pyrite mineralizations
submarine
sequent recrystallization
under
the
sulphides,
of
grain
coarse
depositional
the
and
structures
these
deposits
cupriferous
Sub-
mafic volcanics.
high-grade
conditions caused
destroying
and
textures,
original
any
the alteration
As
to
intermediate metavolcanics interbedded among
metasediments. the Fornás, Arinteiro and
be classified
may
genie
as
classification
deposit
to
belonging
mineralization
sulphide
Bamba deposits
the Besshi type of volcanodiscussion
(see
under Lower
of sulphide-
Carboniferous base-metal
sulphides).
the
and
Portugal
of
infilling
fossiliferous Cambrian
was
southwest
large,
a
fairly
of the northern
in
largely deposited
shallow
-
Spain)
and
basin.
deep
The
and southern Meseta
and
waters
it
shows
a
much
greater development of carbonates.
Characteristic for the
are thin
the ore-bearing amphibolites of the Ordenes complex
mafic
flysch-like (as also the fossiliferous Middle Cambrian
southeast-central
represent
to
pyrrhotite of original pyrite.
are
called
of
of rounded
black
and coeval
Beira Schists
formations
interbeds of quartz conglomerates made
pebbles
of
quartz and quartzite.
chert
quartzite and
Characteristic
and
too.
for correlation
with
clasts of
rare
Serie
from the
Negra.
like the quartz conglomerates useful
amphibole schists
are
purposes,
Garbenschiefer type.
derived
They
occur
thin beds of
as
of
metamor-
phosed impure calcareous sediments, consisting of quartz,
calcic plagioclase and
amphibole (often hornblende) poikil-
oblasts, frequently accompanied by garnet and other silicates.
CAMBRIAN
have
They
been
Beira
described from the
Schists in
Portugal
(Schermerhorn. 1956) and from similar successions
The Cambrian of
and
the
Iberian Meseta
Cambrian volcanism
Portugal
is well
a
in
the
Julivert
in
al..
et
Schmitz.
the
Meseta
Schmitz
1974;
felsic
or
the
near
important
&
volcanics
is
thick
Lower
in
Vázquez
are
also
several places. Less
occur
in
the
of
consists
and
and
slates
felsic volcanics.
some
Upper Cambrian (Potsdamian)
shows
south
south
Portugal,
and
Spain
northwest
addition, the Beira Schists and the Olio de Sapo
are
here
in
regarded,
Portuguese geologists,
The
Beira
Meseta. The
for short,
is
occupy
name
to
as
be
of
vast
Portugal
Beira Schist
preferred
in the
tracts
formation has
also
not
in Spain
Beira Schists
(Xistos
1907);
(such
as
unfossiliferous. but
equivalence
to,
(Schermerhorn,
García,
1973;
mably into
They
the
at
least, the
1955.
'xistograuváquico',
1956;
the
Valdelacasa
and the
upper
other arguments
Middle and
Bard
Ribeiro, 1974) and
basal Ordovician (A.
The
the fossiliferous
Beira
Schists (and
Lower
consist mostly of interbedded slates
like
and
the
are
their
Cambrian
Martínez
The
Olio
augengneisses
pers.
the
in
Spain
entirely similar
rocks are
1973:
to
Martínez
of interest because
mineralizations (see
de
is
Sapo
a
in
sequence
dominant, mostly
are
which
be-
volcanics. This formation is exposed
Spain. It is
rocks,
a
and
Sapo-like
extend
rocks
Olio
in
northwest and
lateral equivalent of Cambrian and
may
relationship
at
occur
Serie
the
to
into
levels
lower
is
Negra
de Sapo constitutes
a
too,
granites.
earlier
Its
into
deposition
the
during
went
of a
Olio
lithofacies largely
porphyritic
from the early Cambrian
on
de
their
though
always clear.
not
regional
Ordovician, indicating
this period
meta-
central
Beira Schist
the basal Ordovician.
made of the freshly eroded debris of Precambrian
tence
coarse
of metamor-
consisting
feldspathic sediments, with interbedded felsic
phosed
granitic
the
or
continuous exis-
source
area
within the
Hercynian geosyncline.
Thus
Hercynian
great
thickness
over
and clay,
the
tus
into
terrigenous
greywackes
Negra,
-
often
the
deposited during
of
the
Late
or
more
of the
the
Cambrian along the
Meseta.
Here
with
a
mostly
Precambrian and
basin configuration
Meseta. One
starts
elastics,
was
not
uniform
geanticlinal ridges
older Precambrian basement shed
attained great
feldspathic
detri-
conditions prevailed
northern
carbonate
and
southern
deposition
importance during part of the Lower Cam-
brian.
The Cambrian carbonate rocks and the associated mineralizations
the
are
economically important. Though very
terrigenous
Cambrian, the
Locally
Serie
sedimentation
géosynclinal
of
the basin, and shallow-water
during most
edges of
comra.).
uncertain.
extent
exposing
contain
chronostratig-
is still
rock
a
low).
confor-
pass
Negra and the Beira
Cambrian
equivalent),
show
1972;
they
Ribeiro,
Serie
Series,
Lower
al..
et
locally
raphical age of the junction between
or
an
coeval
Alcudiense)
overlie Serie Negra rocks, and the precise
Schists
this
in accordance with modern litho-
Villalba Series, the Porto Series
generally
and
western
stratigraphical nomenclature. The Beira Schists and
formations
1973); these
Cambrian. However,
or
shows
Martinez Carda.
scheelite
sand
and
since it has clear priority
as
Nicolau.
central
Formation,
become known
13):
fig.
and equivalent for-
das Beiras. Formaçâo Xistosa da Beira: Delgado,
equivocal designation
&
they host
5
fig.
Formation
Spanish
many
In
essentially Cambrian successions.
Schists
mations in Spain
with
common
out
Spain.
(his
Schermerhorn's
The
sandstone-slate lithology. Fossiliferous Cambrian
crops
in
&
Cambrian in northwest Spain.
Middle Cambrian (Acadian)
the
Walter
1971a;
(Guillou,
1955;
interbedded
locally
1976), and volcanics
sandstones and contains spilites
a
1974;
Walter.
carbonates, the Cándana Limestone,
Where still present,
is
(Schermerhom,
base of the Cambrian
lower part of the
sequence
part that
upper
1975). This carbonate level
mafic
sandy-slaty
south, thinning northwards and thick-
northern
Guzman & Fernández Pompa,
The
south
1969
(Capdevila,
García
is a
limestone-dolomitelevel in its
and continuous
found
in
and southwest Spain.
ening again
with
thick
very
developed, especially
The Lower Cambrian (Georgian)
with
is generally
elastics
Beira
syngenetic
the
making
up
Schists and
mineral
to
grades
the
deposits
quartz conglomerates
main (1971) refers
most
up
to
are
extensive,
of the fossiliferous
Olio
of
de
any
Sapo do
not
significance.
auriferous: Ta-
16 g/t Au in the Valle de
Alcudia in southern Spain. The slates, sandstones, schists and
gneisses
and
are
quarried
roadmaking
limestones
and
to some extent to
material,
marbles
but
that
it
are
is
provide local building
the
Lower
extensively
Cambrian
exploited
as
28
ornamental
and
stone
for industrial
in
purposes
south
Por-
tugal, northwest and southwest Spain.
Local
within
sedimentary differentiationto magnesium-rich rocks
the
mation
Spain.
Lower
Cambrian
of
several
The
largest
province)
m a
is
Here
belonging
to
origin (Doval
e
n
i
s
has led
Pacios
at
in
deposits
t e
the two active
the for-
to
northwest
Incio
near
(Lugo
mines
magnesite
in
the
the magnesite is associated with dolomites
the
et
carbonates
worked
and is one ol
Peninsula.
g
Cándana Formation
al.,
Pn-Zn
and
is
of
lagoonal
Portugal
belt
defined
been
amphibole
southwest
in
found disseminated
equivalent
Spain
western
to
as
Arribas
the
in
the
thin
layers of
quartzite of gneiss)
called
sequences,
(Pellitero,
Though formerly ascribed
where
such
as
granite
&
Saavedra.
1976).
ing 400
metres
reinterpretation
aureoles)
in
as
a
similar scheelite
be
occurrences
a
1956.
strike
length
77,
p.
537)
mineralization
syngenetic
will
hornblende schist (out-
over
(Schermerhorn.
sediments. This problem
later,
Castro Daire in northern Portugal
near
contact
the
epigenetic Sn-W minerali-
scheelite is found dispersed
side the
in
south of Salamanca
generated by the Hercynian granites, discussed
zation
occurrences
examined when
in
tain
magnetite
in
marly
the
lotect for Pb-Zn mineralization.
Upper
and
Lower
Georgian
In west and
northwest
limestones
carry
stratiform base-metal mineralizations
with antimony and
seur.
1977). These
traces
are
of
mercury
considered
brian
and
from
a
Lugo province),
is
found
in
where
at
least
12 million
tonnes
limb of
is
an
grading 8.1",,
3"„ Pb has also been quoted) with
dating
to
transported
not
yet
de
Serviço
Silurian
in
lacking
as
We
(or
at
the
Zinc
be
Belt
1976a).
Middle Cambrian
follow S.
will
F.
M.
metallogenetic province
a
from
different
ores
the
metamorphosed during
Late
have
have
epochs
been
Hercynian
strongly
orogeny.
Precambrian-Palaeozoic succession of the
Meseta:
it
is
marker
a
There
and
less
carbonates
south-
dint
by
of
its
metamorphosed
nearby in southwest
1965).
two
are
horizon
correlated with the
of
types
zation in this mineral belt.
at
con-
carbonate level, here mostly dolomitic, is unique in the
singularity reliably
Mon-
represent
the
1971a, b; Carvalho,
superposed. All rocks and
folded and
of
the
at
also
minerali-
sulphide
The most
type, found
frequent
Ficalho, Balsa and other prospects, consists of
Preguiça.
stratabound accumulations of marmatitic sphalerite, argenti-
discovery,
east
Belt
Lower
the
Middle and Upper Cam-
1971a).
Zinc
mineralizations
become
west
the
of
Lower
are
volcanism could
1972; Guillou,
fossiliferous Upper Georgian
a
zinc-lead
mine. The
silicified limestones
alternating with mudstone
layers, in the dragfolded
to others the
are
the top of
at
near or
of these volcanics is
the
et
continues into
part
opinion
al.,
et
Spain (Carvalhosa,
in northwest Spain (Piedrafita del Cebrero,
a recent
Ordovician
associated
weathered landmass.
Rubiales
ore
Spain.
(Guillou, 1971a;
marine concentrations of elements leached and
the
(Goinhas, 1971; Carvalho
According
1971; Carvalho
massive bodies
as
been
Fomento
volcanics which
geologists they
syngenetic
sometimes
by Guillou
Mineiro
de
Serviço
upper
age
the
In
Upper Ordovician), and
most
whole
important metal-
The
orebodies.
opinion and regard
reviewing
the
in
certainty.
lead
Cambrian lead-zinc sulphides
an
horizon
(Andrade,
Silurian calc-silicate rocks.
Lower Cambrian carbonates form
with
known
has
stratabound sulphide
Here
(Upper Georgian), and
Fomento
the
disseminations
as
base of disconformably overlying
known
Fig. 3)
1972; Goinhas.
(Guillou, 1971).
Spain
exceedto
lead-zinc-magnetite
This metallogenetic province
carbonate
The
The
J969,
the
near
Magnetítica Alentejana, also
e
thoroughly explored by
1971a, b).
Cambrian
schist (sometimes
Beira Schists and
and
the carbonates
southwest Meseta. In south
Zinc Belt, for short
or
Mineiro (Andrade,
al.,
in the
Lower Palaeozoic
(Faixa Zincífera
mineralizations occur
1977).
schee lite
Scheelite has
a
in
widespread
are
Faixa Zincífera,
as
the
Cambrian
sulphides
top of the Lower Cambrian
anticline.
Zn and
some
Reserves are
1.5% Pb(2.5-
Cu and Ag (White,
1977b).
ferous galena and pyrite
with
in siliceous metadolomite horizons,
the sulphides mostly forming
The
tures.
other
orebodies
Ruiva,
type,
discussed
under
Preguiça,
near
found
and
weathered, leached and
in
veloped
the
Tertiary. The
zinc
hydrozincite
along microfrac-
Silurian
massive
metallization.
At
Vila
elsewhere, primary sulphides
were
karst
surface
during
ore
Zn
veinlets
Algares, comprises
Cambrian carbonates, possibly
5
rcdeposited
on
of iron oxides
consists
silicates
oxides,
at
and
a
and calamine,
carbonates, such
as
dethe
that
is.
smithsonite,
(C0 3 ) 2 (OH) 6 and descloizite Pb (Zn, Cu)
(V0 4 ) (OH).
The
disseminated
Belt are
lated
thought
to
to
sulphides
volcanism.
bution of the
dolomites,
in
the
dolomites
of
the
Zinc
be synsedimentary mineralizations unreLater
sulphides in
accompanied
remobilization caused
veinlets following
by
silicification
redistri-
cracks
and
in
the
redolomiti-
zation.
In the continuation
same two
to
of the
Zinc
Belt in
southwest
types of sulphide mineralization
Guillou
(1971b) Pb
and
barite
occur
occur.
disseminated
Cambrian dolomites, accompanied by subordinate
little
tics)
Fig.
3.
(1971).
The
South-Portuguese zinc-magnetite
belt.
After
Goinhas
Cu, Ag, Sb, while the
contain
sulphide
overlying
lenses
the
Spain
According
Zn
in
and
volcanics (felsic pyroclas-
(pyrite
with
pyrrhotite,
mag-
netite, sphalerite, chalcopyrite and galena) associated with
carbonate
and chert
lenses. Guillou
concludes
to a
syngenetic
29
origin of both mineralizations: Cu, Pb, Sb. Hg and Ba
with
deposited
the
carbonates
Cambrian carbonate level,
weathered land
almost
where
-
lacking
with
while
masses,
is
the
at
the
top
metals
the
were
Lower
deriving
from
abundant, else-
- locally
Zn
of
volcanogenic.
mining,
in
and
layers and
all. the
difference
age
between
the
Middle
even
taken
two
Cambrian,
of
types
sufficiently
seems
mineralization
belong
must
Cambrian carbonates
carbonate
of
position
Cambrian
to
different
Lower
terrigenous-sedimentary
lead and zinc
dissipation of
been
could have
sea
sedimentary
of
the
environments.
favourable
instead
that,
different
two
sedimentation became
Concentration
or
occurrence,
metallotect for lead-zinc
are a
likely that the end of the period of
seems
Ordovician
significant
with their different modes of
together
periods of deposition and represent
n
Cambrian dolomites
Pb
and
ore,
Cambrian
for
and
the
de-
is
associated
with
the
iron
but
magma,
has
mercury
mine
panied by cinnabar veinlets; other
galena, chalcopyrite.
this
Pompa (1976)
related
barite
and
mineralization
the
postdating
was
working stratiform cinnabar impregnations
three horizons in Lower Cambrian limestones,
whether
Cambrian.
think
it
is
minerals
well
is
syngeneic
Vázquez
may
included
It
quartz.
be
accom-
certain
not
or
and
Guzman
pyrite,
also been
Hercynian
important
In
the
in
of pre-orogenic
age
and
to
h
Córdoba
i
of
northern and
central
considerableeconomic
assumes
signi-
to
of
1976).
In
contact
magnetite
a
south
this
belt
extends from
Cuzmán
Badajoz (Vázquez
continuing
in
Portugal in the Elvas
metallogenetical province
occur
aureoles
Lower
in
of
&
magnetite
Cambrian carbonates
Hercynian
granites
to
quartz
diorites.
Thus,
the
central
the Elvas region of
Alagada deposit
million
one
tonnes
Portugal,
near
Spain,
of stratiform magnetite bodies, totalling
at
40",, Fe,
12%
SiO,
and
0.73",, S,
is
enclosed in Lower Cambrian marbles, calcsilicate hornfelses
and
skarns
al.,
1971a: Carvalho.
In
in
contact
with
near
a
Hercynian granite (Carvalho
be
Jerez de
are
found in
los Caballeros,
sometimes hematiteand rarely siderite,
Fe, with sulphur and silica
over); the
The
phosphorus
most
million
can
of
In
favour of
minor iron
ore
Elsewhere there are
outside
limestone only.
pure
synge-
folded
as
strong
the formation
as
associated
number
Meseta
of
of
signs
mineral-
the
contact
More
is
study
the
as
content
of
reserves.
this belt
Monchi
and
ore
is
near
mafic
are
in
rare
that
serpentinites
and
the
1) the Early
groups:
and
rocks
in
paragneisses
massifs in the northwest
and extrusives of
these
northwest
are
Meseta
de Compostela
varying
ages
discussed
on
a
found
are
a
of the
corner
from Early
to
later page.
the
Cabo
mafics exposed),
(only
Bragança
consists
known
Here
over
a
is the Cabo
Ortegal.
Sobrado.
of amphibolite, granulite and
room-shaped intrusions and they
was
or
1967).
with
Moráis
are
seen
attended by
ultramafic rocks (lherzolite,
derived from the
mantle.
Little chromite
indicates
during
where
and
no
the last world
chrome
mitite deposits
mines
are
et
al.,
in these complexes,
the
Bragança massif has produced
ore
al.,
war.
1979).
and dunite) are
dating of
that intrusion took place
Calsteren
(van
ago
occurs
Portugal
et
diapirs
metamor-
Rb-Sr whole-rock isochron
Cabo Ortegal Iherzolites
about 500± 100 Ma
harzburgite
ultra-
mush-
are
mantle
as
high-grade
Por-
which
eclogite-facies
complexes
phism and various other effects (van Calsteren
The
mafic-
(northeast
Ortegal complex
mafics. mafics and paragneisses. These
1979).
most
Abessedo
some
are
working
small,
irregular
any
more,
the
of tonnes
was on a small
of
scale
chro-
for the
and mostly
in
perhaps
mine in
thousands
Extraction
rather
low-
grade.
chromitc
in
occurrences
(1947a). C'hromitite is present
hundred
magnetite associated
Trás-os-Montes
Bur-
principal impurities (1% S
is negligible (Doetsch,
in
complexes
48-52",,
and
Bragança-Vinhais)
(or
complexes
(San
magnetite,
averages
important deposit is Cala, with
tonnes
two
and 2) ultramafics occurring associated with
(Fig. 2),
Palaeozoic;
In
chromium,
peridotites
-
with
high-grade
intrusives
Santiago
of
source
divided into
Palaeozoic ultramafics
occur
The
mines
del Cerro, Cala, Teuler, etc.). The
guillos
et
1976a).
Spain several iron
Guillermo
origin
chromium
the
northeast
in
rather
whose emplacement
of skarn type
the
n
of the
sequences
the south.
region (Fig. 2).
ii
intruding
volcanic
or
(Doetsch. 1967).
granites.
Meseta. They
Late
iron mineralization is found in the Cambrian or
southwest Spain
deposits
uncertain.
from
deriving
carbonate horizon that
a
tugal). The best
Fernandez Pompa.
vv
belt is
Mellid and Lalin mafic-ultramafic complexes in Galicia, and
Meseta. However, iron
near
country rock
granite.
near
sulphides
occurrence
Ultramafic rocks,
Fernández
iron
in
with
The deposit
needed.
mafic
tectonism.
supposed Cambrian
ficance
the
defended
consists
ultramafic
No
forms
ore
(5-30 cm),
pyrometasomatic mode of formation,
a
of epigenetic mineralization, such
the
Cambrian
skarn,
syngenetic sedimentary
layers older than
epigenetic,
volcanism. with subsequent remobilization due
to
is banded
limestone-quartzite-slate
netic deposition is the
aureole
At Usagre in southwest
Spain (near Burguillos del Cerro)
mercury
underground
magnetite
mineralization in this
and
a
Early Palaeozoic
along
The
and palaeogeographical configurations.
Cambrian (?)
a
by opencast and
Cu.
modified by later metamorphism caused by granite intrusion
ized skarns
brought about by suitable
of the
The origin
Zn
the
in
with much
Many authors favour
sulphides.
in
and
rich in pyrite and chalcopyrite.
zones
interbedded
occurs
the overlying volcanics, whether Silurian,
worked
Fe
producing
conformable levels and lenses and
and
All
is
sulphides
copper
in
lenses
and
mine
worked
some
Portugal
the
Braganea and
Moráis
have been described by Cotelo
as
vaguely
Neiva
bounded pockets,
layers in peridotite and serpentinite. The Abessedo
pockets
chromitite pockets
yielded
up
to
1500
grading
t
40
ehromite.
48",,
In
Cr
these
2
0,;
ores
chromite is associated with
serpentinized olivine.
Platinum
Neiva.
occurs
1947a. b).
as
minute inclusions in chromite (Cotelo
30
ORDOVICIAN
During the Upper Cambrian
and
erosion,
Cambrian
the
over
disconformable
Lower
reach
This
developed
in
in
is
1956).
conformable,
different
localities.
with quartzites
that
so-called Armorican Quartzite,
central and
where
brian carbonates, and in north
out
thinning
Iberia but
west
southern Spain and Portugal,
In
the
thickness, locally underlain by
is the
level
in
generally begins
metres
1955,
(Schermerhorn,
unconformable
or
Ordovician
conglomerate.
well
transgressed
few hundred
a
affected
phase,
Cambrian-Ordovician junction
the
The
Sardic
considerable part of the Meseta, after which
a
Ordovician
Thus
phase of folding, tilting, uplift
a
the
called
often
in
Silurian overlies Camand northwest Spain.
Portugal
few places the quartzites enclose interbedded volcanics.
a
The
followed by
are
quartzites
a
of dark
sequence
trilobite
slates, and the Upper Ordovician contains slates, sandstones
limestones.
and locally
and mafic volcanism took place
Felsic
during the deposition of these
the
tectonic
Ordovician
mostly conformable,
the
and peralkaline massifs
often
even
granites
some
are
largest deposits
Coto
northwest
Marâo
in north Portugal. The
ore
siderite
in
this
overlying slates; the
Meseta
iron-ore de1971 ;
Rebelo,
in
northwest Spain
Moncorvo and
is mostly oxidic. sometimes
chamositic. Guadramil
of oolitic
&
mines) and
Wagner
northeast Portugal is
in
horizon. The
exploited magnetite interbedded
Marâo mine
quartzites
the
the top of
at
a
is metamorphic (Priem,
ore
the
By far
tonnes
in
and
the near
may
comm.)
be
is
limb of
the
km in
been
8
km
been
to be
high
the
content
long by
as one
grade
(0.4-0.5%)
km
is found in
a
since
million tpy
A.
(J.
tonnes
Rebelo,
is low (36% Fe) and
troublesome. The
wide and
A
Moncorvo synclinorium.
size,
1.5
a
exceed 550 million
reserves
billion
average
1
north-
intermittently worked
developed into
future. The
as
though
phosphorus
deposit
1
which has
in
isMoncorvo
occurrence
century and is
producer
the
largest
Portugal,
13th
in
occurs
main
north
the
smaller deposit,
0.5
by
syncline nearby. These deposits have
folded and suffered regional and contact
during the Hercynian orogeny. The
ore
metamorphism
is mainly hematitic.
including spéculante and martite, and rather siliceous. Below
a
depth
of
80-100
comm). Banded
orebodies
occur
Armorican
zites.
They
were
crossbedded
low
to
magnetite predominates (Rebelo,
m
ore/quartzite
as
distinct
alternations
levels
in
quartzite formation and
deposited
iron oxide
Ordovician iron
are
of Lower Ordovician ironstone
landmass
ironstone
in
the
northwest
hatched:
occurs;
Meseta.
land
probable
around
deposits
Stippled:
during
zone
in
Ordovician.
(1974).
proportions of
characterized
ores
medium
in
a
the
pass
shallow
sands (Thadeu,
of northwest
grade (up
to
Spain
are
frequent. The
part
upper
laterally
sea,
pers.
into
of
apparently
1952,
the
quartas
1965a). The
and north Portugal
55% Fe),
contain varying
siliceous
and
aluminous
by phosphorus
lophane, that
may
exceed
0.8",,
and
gangue,
in
contents,
apatite and
are
col-
1967; Carvalho.
(Doetsch,
1976a).
They show
shallow
sedimentary facies indicating deposition in
a
epicontinental
sea
and
their existence
owe
palaeogeographical configuration that
Upper Cambrian tectonic
northwest
landmass
remained
quartzite transgressed
strata. The
iron-ore
this
surround
Rebelo (1971)
which
a
(Sardic
to
as
and
( 1974), the
have
may
according
Lower
less eroded
Lower
to
The
emergent
an
or
deposits in the
landmass,
Ribeiro
they think
more
over
a
the
result of the
phase).
during the Ordovician while around it the
Ordovician
vician
arose as
movements
Meseta
of the
corner
Cambrian
1962).
pers.
Distribution
4.
emerged
which
Por-
1971; Ribeiro. 1974).
Ponferrada
near
Vivaldi,
the
the
their top (Ribeiro
(Coto
or
of
Campos Julia,
The
the
an
After Ribeiro
near or at
&
east
Fig.
al.. 1970).
et
quartzites
Armengot de Pedro
and in
though
or
east-central
in
stratabound marine-sedimentary
posits, especially
deposit
Ordovician
emplaced
were
Ordovician
enclose
sideritic
disconformable
of
and
iron
Lower
The
late
Galicia (Priem
western
Ordovician
be locally
can
unconformable. During
tugal and
uplift
caused local
Ordovician-Silurian junction,
the
and
emergence,
Towards the end
sequences.
movements
Ordo-
Ribeiro and
source area
for the iron
leached from weathered
been
mafic rocks (Fig. 4).
The
places
iron
as
precipitated
silicate
or
in coastal
carbonate,
cochemical conditions. After
local
became concentrated in
Spain has
large iron
no
France. Sweden
open
some current
on
as
ore
at
production
7,684,000
100
million
(50%
itself
production,
August
1977). Portugal
the
Marquesado
1977).
within the
with its
These
year
of
Fe.
Spanish
was
a
grading 55-56",,
decline in
produced
4.3",,
below
produced
in
output:
ore
in 1976, 10.8",, below
(Mining
1974
51,989
1977
iron
t
Mag.,
magnetite,
he-
(Bol. Minas (Lisboa),
figures illustrate the potential impor-
Iberian
enormous
per
reserves
matite and ferromanganese ore
December
ore
production, unlike for instance
tonnes
Fe)
the
transport,
accumulations.
Triassic' limestones, from
indicate
figures
t ore
in
oxides, in
local physi-
pit in the southeast, produces 3 million tonnes
estimated
tance
mostly
Russia. The largest mine,
or
hematite-goethite
1975
ore
waters,
dependent
context
reserves.
of the
Moncorvo
orebody
31
Ordovician
In
antimony
northwest Spain
small
associated
deposits
carbonate lenses.
This
in a
mineralization
and
redistributed
of the
with
releasing
with
is
mined
from
several
Upper Ordovician (Ashgill)
as
synsedimentary
a
shallow-marineenvironment, remobilized
The
the Hercynian orogeny.
during
during
redeposition along the
subsequent
coast
Silurian
sands
(Guillou. 1969, 1971a).
origin unlikely and
Silurian
the
highly
the
dark
Meseta
sandy.
volcanic,
Silurian
is
In
with
usually presents
slates
graptolite
often is
extrusives.
with
black
In south
chert
interbeds of
The
(lydite).
abundant levels
the Lower
of
mafic
and
Upper
into
and
felsic
the
and northwest Spain
A
the
1
Near
the base
of the
Silurian
volcanics.
important mercury, iron
occur
base-metal mineralizations. At higher levels stratabound
scheelite is found.
is
junction
generally
a
little
dis-
mine'
in
consisting
each about
'the
of
on
It
earth.
is
stratiform
a
three cinnabar-impregnated
10
m
thick, within
the
Hg
mineralization
quartzite
layers,
quartzite formation known
'cuarcita del criadero' (ore-deposit quartzite). This quart-
zite horizon is the host of the
smaller
The
grade
the
at
recently
Entredicho,
17
50",, cinnabar
1978,
in
occurrences
native mercury)
is
(i.e.
Arabic) is by far the largest and richest known
accumulation
as
Almadén
during
the
in some
(1975)
km
1940 it
was
mercury
mercury
Geol.
cinnabar
Almadén
grades.
Even
richer
of
deposit
El
consisting of
ore
Minero (Madrid), vol. 89,
and it is now
ever
was
ore
worked
Hg, around
8"„
Silurian (Valentian)
volcanism
started
before
is
approached these
for
accounts
by analogy
age.
the
In
18",,
of
considered
the Almadén
deposition
formation and continued afterwards
of
during
to
area,
this
be of
mafic
quartzite
the Silurian and
native
quicksilver and
sedimentary features indicating
troduction, before
direct genetic
rest
its
in the mineralized
that the
area,
set
some
early
in-
suggests
a
between the Hg mineralizationand
the Silurian volcanism which reached
volcanic activity
its
diagenesis (Saupé, 1976). Saupé
relationship
in the
sense
passes
worked
and
be
first
al..
et
Monges
million
1971;
some
of
mafic
pre-
meta-
in
most
1971
Carvalho,
known reached 30
been
Alvito,
Pedrógao,
Orada
was
(its original
reserves
were
1971, 1976a). Magnetite may
plentiful, and pyrrhotite
al..
et
The
1971a. b).
thickness by
m
has
south Portugal (Nogueirinha
important of which
Carvalho
1969;
massive lenses
as
metavolcanics and
mining ceased in
tonnes -
base
to
to
with sub-
(Andrade.
disseminated and
mafic
to
veinlets
Montemor-o-Novo,
near
where
orebody
largest
about
length of
a
m.
The
polymetallic
greenstones and the
the
the
at
a
dissemi-
a
1971a, b).
accompanied by pyrite, locally
250
depth, beneath
consists of banded
occur
galena
occurs
Orada and others) the
two
The
two
metallo-
Lower Cambrian dolomites containing
in several small mines
(Fig. 3)
in
with:
mineralization overlies
and
intermediate
up
calcareous
magnetite, sphalerite, barite, and
on
pyrite
green-
Portugal the
greenstones are
at
now
the
base
1976a; Carvalho
the
of
lenses
within
mostly regarded as syngenetic exhala-
deposits (Andrade,
tive-sedimentary
1971.
lenses
pyritic
magnetite-pyrite-pyrrhotite
et
al.,
1972; Carvalho,
1969.
1971a, b).
Maria
Morena
Luisa
is an old
for copper
with
of pyrite
with
mine
near
La
Nava
gold and silver
as
byproducts.
and
chalcopyrite
the metamorphic
to
(greenstone, jasper and schist).
greatest development
Lower
Silurian
into motion the convection of solutions
1974)
revealed
the
existence
mineralizations
magnetite
on
The ore
in
layering
the
of
syngenetic
which
an
diorite
originated
as
in
host rocks
com-
sulphide
and
epigenetic sulphides-
(with diopside, actinolite
Luisa
places
Guzman (1972,
has been superposed
by
consists
in
Detailed studies of the
type (re)crystallization
Maria
Sierra
concentrated
are
magnetite assemblage
caused
the
now worked
sphalerite, and
magnetite and pyrrhotite. The minerals
bands parallel
in
cupriferous pyrite exploitation
plex paragenetical relationships by Vázquez
The cinnabar, accompanied by
shows
the
The
ex-
world
Devonian.
pyrite,
or
around 1.5",,. No other
production.
The cuarcita del criadero
Early
richest lodes.
quarter of this century
Hg
(cinnabar and
grade of the Almadén
deposit anywhere has
rich
tremely
20",, Hg
Almadén, where
(Bol.
in
met
are
1971; Carvalho
(Carvalho.
discovered
average
still 6-7",,
and several much
Almadén
in the
places
from
occurs
first
ore at
area.
Almadén reached
188). The
p.
the
south
Silurian greenstones (intermediate
tuffs) which
with
enclosing
formation
associated with
prospect in
galena. These
Magnetite
deposit of
mercury
and
chalcopyrite
Almadén
mercury:
The celebrated
greenstones
are
orebodies made mostly of pyrite,
ordinate pyrrhotite,
Por-
massive
associated
occur
This
likewise
zinc
s
south
containing orebodies.
not
e
of
discussed,
metavolcanics)
calcschists.
mineralization.
massive
Goinhas,
Silurian
r
mafic
massive pyritic
a
gossan,
sphalerite,
transition.
a
g
belt
as
Cambrian carbonate level.
Portugal,
to
genetic belt (see above)
sumably
Silurian-Devonian
The
turbed
an
for the Hg.
source
types of sulphide mineralization characteristic of this
almost
and
rede-
magnetite
Spain,
Lower
south
metasediments but
nated Pb-Zn
and mafic
in
(intermediate
layers,
felsic
the
felsic metavolcanics,
Al
and
magnetite orebodies
overlying
type turbidites. greywackes and slates containing black chert
plentiful
volcanic
a
southwest
lenses of marbles and
Silurian is
thick eugeosynclinal facies of flysch-
a
as
monotonous
a
frequent
Portugal
northeast Portugal
developed
with
and
These volcanics,
sandstone, limestone and
Silurian
3)
tugal (Fig.
schists
of
proposes
base-metal sulphides
sulphide
SILURIAN
facies
Ordo-
and
trapped
was
mercury
lead-zinc-magnetite
volcanics
The Silurian of
the
where
in
it into overlying
transporting
posited by sulphidization. Maucher (1976) considers such
In
emer-
erosion
following
preconcentrated by adsorption
mercury
vician carbonaceous muds and
origin
in earlier Ordovician volcanism.
concentration
pedological
and
been
interpreted
Sb could be sought
gence,
has
antimony
through
and
skarn-
epidote)
intrusions.
and
other
submarine
occurrences
in
the
same
region
exhalative-sedimentary sulphide ac-
32
cumulations
locally
these
ores
volcanic
in
the
too
is uncertain
dated. They
horizons
since
associated
Middle
as
jaspers:
The
ore.
their host rocks have
regarded
were
and
contain manganese
jaspers
yet been
not
Upper Devonian by
to
Vázquez Guzman and Fernández Pompa (1976). Other
thors, such
Monseur
as
(1977), favour
since the syngenetic stratiform
clearly
volcanogenic
a
(or
Cambrian
a
of these
ores
Lower
a
Silurian
seems
age
However,
the
Cabo
thought
metasedimentsand
is
occurrences
are
Devonian
Silurian and, possibly,
1975;
van
been
be Precambrian, have recently
der
in
Mohr.
Meer
the
zone
same
In
1975).
occur
formerly
shown
to be
(Martinez Garcia
age
the
Moeche
difficult
moreover
sediments.
origin.
volcanics
in
the
for the Cambrian.
not so
the
explain
to
volcanic
or
contains
It
of syngenetic
preference
study is needed.
More
DEVONIAN
Over most
the
of
Meseta
the
Devonian presents
variable
a
epicontinental facies of interbedded sandstones, shales and
possible.
complex,
sedimentary
Silurian
sul-
In
volcanics surrounding
mafic-ultramafic
Ortegal
to
elsewhere
meta
of
the
vicinity of the scheelite beds, this is
carbonates
the
Galicia,
In
be
may
though
tungsten for marly
au-
phide-oxide mineralization,of the type found in the lead-zincmagnetite belt,
tin
panying
Still,
age.
least volcanic-associated)
at
of
age
et
of
al.,
and
area
small stratiform massive
to
not
attaining
northeast
Portugal
Devonian is
southwest
Devonian
of
and part
Meseta
shales
with
volcanism,
mineral deposits
Iberian
(the
mafic,
mostly
associated
are
and
it
consists
limestone
rare
is
and in the
sequence
Belt)
Pyrite
quartzite
Spain the
northwest
flysch-type greywacke-slatc
a
monotonous
great thickness.
any
No
rare.
of
beds.
important
with the Devonian.
disseminated orebodies containing pyrite, hematite and chalinterbedded
copyrite,
Silurian
among
metasediments and
EARLY
TO
MIDDLE
CARBONIFEROUS
metavolcanics.
After
Asbestos
been worked
has
(tremolite-actinolite)
small scale in the Arado do Castanheiro mine
south Portugal, in
with
associated
small
a
belonging
to
Silurian greenstone formation overlying
bonates
(Gaspar,
Portel
a
in
of serpentinized ultramafics
mass
metaspilites
near
on
1971; Carvalho
al.,
et
the
the
presumably
Cambrian
car-
Silurian scheelite
mentioned above,
As
cale-silicate interbeds
the
northern
Portugal and
Silurian
greywacke-slate
in
occurs
sequence
calc-silicate
facies
greywacke-slate
found
of the
in
impure
Beira Schists in
Spain. Similar tungsten mine-
western
the
are
schists: originally
(amphibole
marls) in
ralization
disseminations
scheelite
of
intercalations
northeast
in
the
Portugal and
economy.
mineralization
in
Beira Schists
group
unlike
aspect: they
the
range
amphibole schists of the
from
fine-grained, thinly
consisting of quartz, intermediate plagioclase
banded rocks
and varying
are
amounts
of garnet, actinolite-tremolite, epidote-
minerals, sulphides and other minerals such
(Sousa,
1975: Noronha, 1976)
Scheelite
may
be of wider
Silurian metamarly
posed. Carvalho
to
skarns
(L.
distribution
intercalations
(1971) refers
to
than
in
was
the
diopside
as
Ribeiro,
Cambrian
In
is
northeast
Portugal
of
occurrence
34 m
thick and
up to
(Sousa. 1975; Viegaset al., 1976). Provisional
by
surface sampling before drilling
1.43-3.2
ppm
It
W03 . that
kg/t
near
started
tenors
are
km
long
obtained
follows:
as
420-770
of
Carboniferous
some
two
The
Zones.
northern Spain and the
south
Portugal
flanking
block
troughs
This
the
are
and southwest Spain (Fig. 2).
that
block
is
the Ossa-
Cantabrian
Zone
These
were to
a
a
large
internal
here
in
external
extent
geanticlinal
composite, containing
though the Upper Palaeozoic sediments
the
englobes
and
South Portuguese
secondary geosynclines
the
block which
in which subsidence and
detritus from the central block,
by
central
Central Iberian
in
area.
The
large
central
Morena
are
a
flanking troughs
continued.
Zone
fed
to
Devonian-Carboniferous boundary
Asturian-Leonese, the
basins
rise
gave
importance in the Iberian
source
basins,
deposited do
not
reach the great thicknesses attained by contemporary strata in
in northern and southwest Iberia.
flanking troughs
As
a
result,
Westphalian
marine Carboniferous
strata
Chain and the
Chain
the
marine
mineral
hand,
of
resources.
conformable
shales
The
South
of the Pyrite
sequence
groups.
the
In
the
thin,
including
Cantabrian
Cantabrian
condensed
a
limestones
and
geosyncline
not
on
shales
and
bearing
the
here
other
a
into
laid down, divided
Devonian
are
very
and
in
Portuguese Zone,
Belt
was
Phyllite-Quartzite Group,
er
Zone.
and
to
up
represented
Carboniferous is
succession
eugeosynclinal
well
South Portuguese
Lower
is the site
is
thick
three
quartzites.
the
conformably overlain by Low-
Carboniferous volcanics and sediments of Tournaisian and
Early
Visean
hosts
the Pyrite
mably by
a
age,
thick
the
Belt
Volcanic-Siliceous
mineralization.
barren
flysch
wackes and shales, the Culm
sequence
deposition
was
is
then
A
turbidite
ranges
in
et
confor-
covered
south
brought
orogeny (Schermerhorn. 1971a: Carvalho
which
Complex
of
Group which
Upper Visean into the Westphalian
Géosynclinal
It
to
grey-
from the
Portugal.
an
end
by
al., 1971b. 1976).
Sn.
seems
likely that
syngenetic.
It
may
most
have
of
been
the
tungsten in these marls is
deposited
as
scheelite
or,
Noronha (1976) proposes, originally dispersed tungsten
have
the
three
over
2.5
1134-2538 ppm W. and
is
some
scheelite prospect
Mineralization extends
horizons up to
sup-
Portugal.
the Cravezes
being actively explored.
calc-silicate
and
previously
dispersed scheelite in Silurian calc-silicate hornfelses
old Orada iron mine in south
1971).
the
lull,
resources
the
sedimentation
However, the Silurian metacalcareous interbeds containing
this
At
and
emerged
the
Ribeiro, 1971).
adjacent Spain (L.
Devonian
Meseta became differentiated into
West
1971b).
the
extensive mineral
been
scheelite.
In
remobilized
either case
by
the
metamorphism
syngenetic
to
as
may
produce
tungsten and
accom-
Early Carboniferous base-metal sulphides:
the Iberian
Pyrite
Belt
The
Iberian Pyrite Belt (Fig. 5) is
polymetallic pyrite deposits,
nations,
some
copper
a
metallogenetic province of
copper
veins and
and copper-zinc dissemi-
manganese orebodies.
oc-
33
Fig.
5.
Geology
and
in
major pyritite deposits
the Iberian
Pyrite
Belt. Note
regular spacing
of the
large deposits. Adapted
from
Carvalho
et al.
(1976).
km
cupyingazone230
goes
metals,
a
since
1866
byproduct.
tonnes
this
new
figure.
The
and
important
while
three are
Belt contains
large
Aznalcóllar
In
workings.
Aljustrel,
will
The
(
p
section).
with
i
t
These
are
pyritic
i
are
Pyrite
Belt three
smaller
ones, are,
Sao Domingos and Lousal.
is
to
be
raised
from
t e
1976; Strauss
The
of the Iberian type of
are
(as discussed
stratiform, associated
composed
of
sphalerite,
deposits
with
pyrite
at the
with
small
galena and other
of this
and
other types
(Schermerhorn, 1970).
including prominent jaspers),
consists
sediments
felsic volcanics (largely quartz-
mafic volcanics (spilite lavas and tuffs and
al..
is
the geosyneline
of this
belt
shales,
they
overlie
felsic volcanics
as
at
or
sheetlike
fissures
was
flow
an
tuffs,
near
with
centre
and
When
two
shales
onto
overstep
be wholly enclosed in
centre
occurs
few
it
was
when the explosive
at one.
there
so
or
are
rarely
more,
present, each
Most
will
be
two
to
an
of sulphide
deposition varies between
Lower
Visean,
in
limestones permit
some
others where
dating,
as
at
In
levels.
pyritic
(Strauss
Madcl. 1974; Ramirez Copeiro del Villar. 1976). However,
relatively early, Tournaisian, in
the
eruptive
have its
levels
at
waned.
stratigraphie
ore
pyrite
produced
activity
may
sub-
mostly
generated
lavas and breccias.
the mineralization is related
felsic cycles
mineralization,
explosive, along submarine strike
the top of felsic piles:
eruptive cycle
mining
or
may
1976). and
(Schermcrhorn,
aqueous
or
Tharsis.
The felsic volcanism
each
lenticular
are
conformably interbedded among volcanics and/or
sediments:
end of
et
1977).
and siliceous slates (dust tuffs)
timing
of
el
pyrite deposits
bodies
occurs at or
area
Volcanic-Siliceous Complex
keratophyric tuffs),
production
addition there
In
some
Aljustrel
of chalcopyrite,
y r
enter
soon
Zarza
tonnes.
volcanism and
Massive
five large pyrite
mines, Tharsis, La
the Portuguese
together
of
ore
volcanogenic polymetallic pyritic deposits
consist of
the felsic volcanism in
to
deposits.
manganese
(Schermerhorn. 1971a; Strauss & Madel, 1974; Carvalho
million
minerals.
the
al..
of pyrite
The Iberian Pyrite Belt is the type
proportions
of
double
300.000
of this
genetically linked
ore
manganese
most
million
production
end
sulphide mineralization and
3
The annual
felsic
diabase sills), sulphide deposits and
The
to
have been, worked:
2
here
and noble
is 2.5
production
occurrences,
to
Mining
copper
with iron and other metals
Sotiel Coronada is still under study.
several smaller
or
sulphur,
Spanish Pyrite
and Rio Tinto,
km wide.
projects in Spain and Portugal aim
of which
occurrences
to 30
up
centuries, at first for
also for
Annual
but
long by
30
back for at least
centres:
&
the
it is
mines, and rather late.
microfossils
in
Sotiel Coronada.
associated
As a
result.
34
the
local
volcanic and
correlated from mine
stratigraphie columns
ore
to the west or
Tinto is quite differentfrom Tharsis
to
the
The orebodies
and
be
may
divided into
allochthonous
bodies enclosed in
Rio
which
Tinto,
stockwork
say
that
&
in
rare
Madel. 1974; Williams
the
on
the
Belt
Pyrite
during
transport
some
precipitation
seafloor
stratiform
The
feeders.
own
the
a
fine-grained pyritic
very
and redeposited by
is first
orifices
as
such
movement,
low-angle
gravity flow
at
as
precipitated
on
1970,
en-
led
downslopc
1971b).
The
water
pore
(seawater).
transformation causing
sulphide
mobilizationmechanism, and the gravity
the
gradient existing
instable
thest travelled,
orebodies
it
Belt
namely
t
a
t
or
Zarza
the
from
as
at
&
(Strauss
site
in
occur
eighteen
at
important
removed.
pyritite
and
it has
sense
All
was
1974) while
the
Lousal (Strauss &
left
in
erosion
had
It
Tinto
most
folded
been
Reconstitution by
unfolding yields
measuring approximately
up
to 80
m
of
et
4.5 km
al.,
in
to
the
at
Tharsis
anticline,
as a gossan
an
Pyrite
1976). Largest
are
the
Rio Tinto still has
of
pyritite
55
million
removed
tonnes.
that
in
of pyritite.
least
at
but
this
orefield
twice
area
that
are
very
to lie
at
prospect,
and
1977.
in
There
km
and
the
the
interval
Between
few
The
most
known
are
occurrences
next
Sao Domingos.
medium-sized
to
mineralization
is in
Spain and
deposits such
La
alignment joins Rio Tinto.
The
runs
sulphide
northerly alignment
third alignment
The
Sotiel, Tharsis and Aljustrel.
Portugal and
have
major deposits
deposits.
several small
Concepción.
strike
the
must
the Portuguese half of
in
small
four main alignments of
are
La Zarza and
across
the
only
were
over,
to
accumu-
generated in the Spanish Pyrite
were
a
an incentive
distance
original
as
comparable
large
km.
only but this is
and the
amount.
where only
along the strike. The
comprises
tonnes
was
that
seems
curiously enough
not
beside the four large
in
in
between
Pyrite Belt,
thus
million
small deposits
Belt
the
It
area.
20
distance
distances between 23 and 35
at
numerous
and
they
Neves-Corvo
a
isolated:
are
the same area
mineralization
strike
separated by 12
are
Very
approximately,
million
tonnes
has
as
Zarza
A/nalcóllar.
southernmost alignment is
Lousal and Neves.
through
present
the
known
pyritite
the following
sulphur
46
"„
iron
40
"„
copper
0.7%
zinc
2.9%
of 620
reserves
composition:
average
1.1%
lead
0.6%
0.8
gold
silver
g't
30
1.5
This
km
leads
and
with
on
its
Taking into
wide
to
of
remainder is
as
the
g/t
largely siliceous,
In
the
very
though zinc
a
in
exceeding 30 million
over
pyritite
the
copper
the Pyrite
tonnes,
or
0.7",, Cu. Higher
orebodies (up
to
shows,
ore
be relatively high,
law
geochemical
contain
sulphide
large deposits
can
chloritic and
content
high sulphur
this province is massive
up
of
2"„ Cu) and locally
Aljustrel
in
m
low. 0.3-0.7",,.
as
to
occur
be
bodies
pyritite
thickness, do
tenors
Guzman
(1976)
has
not
in smaller
oreshoots in
established
magnetite and hematite, together with
tonnes
that
40
in
pyritite
4-5",,. It appears
Belt
over
carbonate
high purity.
tenor is
to
copper
most
larger
masses.
Vázquez
an
tonnes.
620 million
reserves
The
gangue:
original pyritite
long by
Belt total
normal
strongly folded
a
been
the world.
(250 million tonnes) and Tharsis (130 million tonnes)
amount
in
La
or
folding
roughly three-quarter billion
in
reserves
(Carvalho
an
thick (Schermerhorn, 1971b).
original tonnage
Present
into
the
arsenic
original deposit has
the north and south limbs and
deposits
only discovered
was
significant
bodies elsewhere in
lations
be
Madel, 1974).
owing
of the
found in
km
the 230
allochthonous
accumulations
where
large pyritite
are
over
regular rather than
a
Aljustrel and Sao Domingos, which seemed twice
prospecting
large single
are
al., 1975)
presents
plot of the large deposits shows them
of
lack
as
pyritite
redeposited
clusters: five pyritite lenses
Rio
between
primary precipitation.
et
A
large blind orebody
large
that
then
may
other orebodics
apparent
precipi-
been
The
pattern.
tonnes.
enormous amount
Belt
Pyrite
billion
total
Belt will
the
Iberian Pyrite Belt contains several pyritite deposits of
subsequent uplift and
crest.
since
of
giant size, the largest sulphide
sheet
the
surface
Rio Tinto (Williams
Madel,
a
the
law.
applying Zipfs
roughly similar intervals (Fig. 5). The
sediment,
autochthonous pyritite bodies
deposits often
been
in
allochthonous pyritite
the
Far-
are
vents,
basin floor. Thus there
exhalative-sedimentary
transported
sheets,
North and
Most
the
the
sets
repeated,
distal pyritite deposits.
hydrothermal
a
Usually
The
is
on
to
laid down asa chemical
some distance
lenses
proximal
exhalative-resedimented
termed
at
pyritite
The
e.
sediments
from
originally
was
times
many
from the volcanic feeder
away
overlying
gradation
Pyrite
process,
the well-bedded allochthonous pyritite lenses.
produces
is a
liquefaction of
the slopes of submarine volcanoes
on
in motion. This
mass
where
the
much smaller.
the seafloor around exhalative
Thixotropic gel-sol
muds is
random
Sotiel
mobilized
masses
length of
2
over
distribution of this
small
sedimentary,
to
(Schermerhorn,
vents
have been somewhat
produced
and
be discovered, and
to
of sulphide deposited in the Iberian Pyrite
struc-
crossbedding
distance
some
sulphide gel containing
a
of internal
occurrence
recognition of allochthonous pyritic
pyritite
allochthonous
as
together with the varying lithological
feeder
is
has
pyritite
most
shortly after its original
vironmentof the orebodies. from volcanic
the
al.. 1975). This
et
elsewhere
sediment
cut-and-fill.
structures,
graded bedding,
from
now
autochthonous deposits overlying
frequent
denoting primary
to the
at
as
zones,
The pyritite is usually thinly and rhythmi-
deposits.
cally bedded, except in
slump
feeder
where
or
as
mud. subsequently consolidating
tures
the pyritite
autochthonous,
overlie
still
The
pipes strongly altered by chloritization and silicifi-
cation (Strauss
their
Aznalcóllar
and
amount
ignored.
Some of
are
they
be
Rio
at
autochthonous
deposits.
felsic volcanics
is to
relatively
suffered
been
This fact has sometimes
east.
cannot
mine: detailed stratigraphy
to
some
that
primary
siderite.
appear
small quantities in pyritite. especially in the northern part
the
Spanish
of
Pyrite Belt.
while
account
the
by erosion, extracted by mining
The
massive
nated
sulphides
may
be associated
with
dissemi-
sulphides constituting syngenetic (pre-folding)
35
epigenetic
or
pyritite
wall
or
stoekwork
(post-folding)
deposits,
or
ores
syngenetic stratabound
slates.
footwall tuft's and
These
ores
underlying
mixture
in
canism
contain
may
hanging
workable
proportions ofchalcopyrite. sphalerite and galena, and
tonnages. This type of mineralization
large
ted
by volcanic material
often
not
the
at
-
source
is
reach
sulphides diluthough
common
economic.
of
juvenile sulphur associated
and
of
Seawater circulating
submarine
the sulphate
sulphur
wide
for instance,
two
lithofacies that
C
1
h
o r
i
mostly of
ing
t i
a
and explorational interest
pyritite: chloritite and jasper.
accompany
named
first studied and
t e,
fine-grained
chlorite
disseminated sulphides
Aljustrel.
at
and
cleaved
it
deposits,
and
sometimes in the
or
reach
may
massive pyritite
50
is
orebody
hanging
thickness.
m
overlain by
may
wall
at
the periphery of
position,
an
generally beyond
higher stratigraphically,
ing
some
are
the
or
a
occurs
near
similar peripheral
jasper lenses, silica
black
a
boundary and slightly
ore
chlorite and pyrite but mostly
oxides, unlike the red
found
pyritite
tuffaceous chloritite
In
orebody.
be
of
At Aznalcóllar
carrying copper-zinc sulphides. Chloritite mostly
or
may
could be, and has
been, mistaken for black slate. Chloritite bodies
the footwall
it
sometimes carbonate;
rocks
unrelated
jaspers
contain-
lacking
poor or
to
in
is
mineralization.
Pyrite,
bodies of pyritite,
silica
intimately
are
chloritite and jasper,
interlaminated.This association is
even
constituting
over,
volcano
a
associated,
intergrown
or
widespread
genie
the
as
and
world
Chlorite and silica
autochthonous
the
pyritite and
autochthonous
and
in
as
the feeder
underneath
zones
surface deposits accompanying
allochthonous
and silicification of footwall rock
Chloritization
pyritite.
in alteration
pipes
is caused
or
vol-
sulphate.
convective
hy-
building
as
cassiterite. sometimes
either
too,
is
large volumes of
up
the
Moreover,
were
silica
and
the
too,
either directly
The
mafic
felsic
mafics
likely
from
or
vents
on
Fe
the
and
Si
Belt
mafic
in-
to
is completely distinct from
transitions.
no
be mantle-derived, such
to
fluids
solutions
be of volcanic origin
to
of the Pyrite
and diabases -
volcanism, showing
are
sulphides
indirectly.
or
volcanism
termediate spilites
pure
deposited, within the
likely
processes are
a
on
process
mineralizing
accompanied by
were
of
very
(primary chloritite and jasper). The Mg.
needed for these
end
discharging
(chloritization and silicification of footwall tuffs)
surface
from the
at the
deposited
without interruptions
chlorite and
of
source
directly
volcanism the hydrothermal
scattered.
are
an
by leaching from volcantes.
the sulphides
bringing
which
volcanic
active
take place
cannot
carries
ore
Picot. 1976). The
from hydrothermal solutions
seafloor and
produced
(Aye &
shows, pyritite
sulphides. During
the
Though
an
origin
seems
less probable for the felsic volcanics, and the few known initial
87
Sr/
the
sulphide precipitation both
accompany
subsurface replacements
in
component. The Iberian
stannite
geology
volcanic cycle,
8b
Sr ratios favour
1 f such
sulphide-
chlorite-silica association.
as
As the
the
chlorite and
felsic
the tuff piles building the
participating
widespread, occurring
magmatic residue
iron
sulphide
the
seawater
range of metals (Schermerhorn, 1971b): tin,
the metals would be
consists
aggregate generally contain-
grade into chloritic tuffs. When
in
are
water in
pore
and
with
from
drothermal systems driven by magmatic heat, would
supply
extremely
metallogenetic
as
volcanoes
accompanied by
Of considerable
derived
sulphur
the
is
case,
magma
been
have
or
crustal
either have
magmas
rocks,
a
origin (Schermerhorn, 1976).
then the sulphur and
an
metals
brought
remelted
in
origin
awaiting resolution. Either
existing sulphur-metals
tonnage of
Belt
Pyrite
by
transferred from mantle-derived mafic
ascending deep-crustal felsic magmas,
to
up
Precambrian
of
type
concentration,
to
a
problem
involves
source
a
the
explain
prevast
deposits.
by syngenetic hydrothermal activity around the feeder channels below the seafloor
on
which pyritite
was
deposited.
Such
replacement bodies show irregular, discordant
shapes. Chlo-
According
ritite and jasper
guished
muds
(they
along
with
may
deposited
grade
bodies.
mediately preceding,
the seafloor,
volcanogenic
as
into tuff) and transported
allochthonous
concordant
on
pyritite
Chloritite
masses,
deposits
and sometimes
sulphide precipitation,
while
the
are
jasper
downslope
metallic
stratiform,
(pyritite)
the phase of
represents
siliceous
precipitation occurring slightly later in
sequence, and
ling
farther
im-
formed
were
succeeding,
to
travel-
out.
The
1.
to
p y
show
emanations
and
of
interaction
that
seawater
the
on
here, between the
seawater
seawater
supplying
isotopic
1975)
gives
rise
seafloor
only
extremes
it
appears
constitution
to
c
whole
may
range
volcanic
heat
serving
chill
to
likely,
of sulphur
in
at
to
the
upwelling
hot
ore
precipitate pyritite.
light
of
data
on
at
Rio Tinto (Williams
et
is found in the mafic
type
the top of
o
p
h
i
1
o
i
t
The
outside
s
p
i 1i
-
deposits
have
sulphide
mineralization in
of the
most
is
linked
to
submarine
found along
3.
important pyritite deposits
including
space,
The
B
e
or
s
n
i
c
s,
Iberian Pyrite
h
i
along
or
is
type
and
mafic
it
through
This
fe 1
s
i
c
comprises
time
type
and
may
associated
with
be
o
n
-
vol-
within continental plates.
al.,
and small
tonnage. Briefly, the
Kuroko
n
intermediate
the Iberian type is sometimes called the
type, the kuroko
the
Belt.
and
within continental plates.
s
ophiolite
ca
the
an oceanic
continental plates.
Iberian type
Though
a
(
complexes.
c
The best known example is Cyprus and similar
the
and elsewhere, that the sulphur in pyritite represents
distin-
poly-
deposits, grading from massive
volcánica (often quartz
keratophyres)
the pre-
(pyritite
a
of
volcano-
all the components of pyritite.
solutions wholly of volcanic
origin,
However,
between
colloform gel textures). There is
of possibilities
only plus
and
an
colloidal sulphides
original
i
be
can
volcanogenic
been described from Newfoundlandand elsewhere. This
type
2.
of
t
represents polymetallic
Pyritite originates through
genie
i
r
Cyprus
lavas
tic)
of
types
disseminated.
environment,
cipitation
their volcanic environment there
three
ores
form
and
a
subtype
of
infrequent
Kuroko
occurrence
differences between
Iberian types
are
as
follows:
36
1. Kuroko-type
(Miocene in
the Archean
2.
Kuroko
mineralization is restricted in time and
space.
Japan), unlike the widespread Iberian type (from
on,
all
the world):
over
deposits
10
over
million
tonnes;
3.
is
Kuroko
black
little
of'
mostly
consisting
ore,
and barite. with
sphalerite,
pyrite and chalcopyrite:
base-metal-carrying pyritite such
this is
of
makes up the bulk
as
the Iberian type deposits:
4.
Oko, the yellow
ing
kuroko
most
often
In
pyritite.
most
transition
ore,
is less well
from a
be
than kuroko, is
developed
copper-rich lower
Abundantbarite and
even
(pyritite) underly-
ore
pyritite bodies of the Iberian type the
part of the deposit takes place
5.
gypsum
to
a
zinc-lead-rich
upper
kuroko and
accompany
important than
more
formed by
7.
with
associated
vent
explosions;
Belt
Pyrite
the
sulphides but
are
lavas
tuff is extremely
normal
are
Every lava dome in the
may
felsic rock,
great distances; kuroko
large deposits
flucence of
gravity and
ore are
manganese
form lenses strung
lation of
may
be
tuff breccias
is
in
its
province has
not
been
Belt
kuroko
transported
in
rarely found
very
the Pyrite
sited
veins
Copper
the Pyrite
where
black
a
even
very
shales.
they
veins containing chalcopyrite and
are
many
Culm
strata,
some
the youngest
well
mineralization could
in
places
and
other minerals, and
post-orogenic since they cut folded, cleaved and
phosed
of
at
crosscutting epigenetic quartz
are
Pyrite
Belt
have originated by
metamor-
This
group.
remobilization
cupriferous pyritite in depth.
in the
occurrences
but
less
million
mines
intensive
of
tonnes,
Where
Aljustrel.
than
from
in
few
the
manganese
was
much
in this belt
hundred
years
are
much
extensive
The
total
is about
occurrences.
The
5
quence,
rhodonite
manganese
in
slightly
pyritite.
younger
at
as
than
the
oxides, derived from rhodochrosite and
depth. They often
associated
are
with jasper
lenses.
The
cipitation
deposits originated through seafloor
probably
as
a
gel.
formed rhodonite,
Later
to
et
al..
1971b.
and
other
1976; Cra-
1976).
ralization
the pyritite
to
silica
depended
masses
manganese
are
associated
small in comparison
with
the
deposits elsewhere.
chemical sediments fed from
a
on
gels
mass
break
takes
place that separates
in
the Hercynian
same
Their
not
only
volcanism but
largely of epeirogenic character
movements
their influence felt
at various times
the
during
the Hercynian geosyncline. leaving their
of
more or
disconformitiesandunconformities. They
widespread
these
tectonic
phases,
emergence
As we
subsidence of the Cantabrian and South
This
geosynclines.
is
phase
to
orogenic phase. Succeeding phases
are
orogeny
epeirogenic
and
movements,
Visean of the
the
to
in the South
group
largely
of
the southwest part
the
Hercynian
the
of
external
nature
during
the
of
the
central
of the thick widespread
deposition
Portuguese
unit, after
sedimentary
the
and
with
first
not
seen,
of
equated
the
of
less
block
end
Meseta
for instance the uplift
area in
source
gave rise
as
be
did
have
Portuguese
sometimes
considered
Bretonian
the
at
acting
of the central
made
development
traces as
involve Meseta-wide orogenic deformation.
Zone, the second
the
Beira
Schists,
most
in
the
Meseta.
When
phase,
full-scale
orogeny
set
in
with
the
Hercynian
main
orogenic development superseded géosynclinal sedi-
mentation in
the
two
external
remnants
geosyncline, the Cantabrian and
The
main
the main
orogeny:
South
of the
Hercynian
Portuguese Zones.
phase
took
Hercynian folding
phalian (Schermerhorn,
is principally of
two
place during
the
formations
to
up
Visean and Namurian (where
present)
Carboniferous
West-
1956, 1971a). The evidence for this
kinds: firstly, everywhere in the Meseta
the older géosynclinal
and
strata
(mostly
the
including
were folded
before the
Upper Westphalian
to
Upper
and
Ste-
phanian). themselves deformed by later Hercynian phases.
Secondly, this folding
of cleavage
and
was
accompanied by
closely followed in
many
the
development
places by regional
metamorphism. migmatization and the emplacement of the
Older
diometrically
that is
as
Priem
source
1979).
deposition
volcanic-hydrothermal
se-
episodes.
widespread
The manganese orebodies
ako
metamorphic recrystalli-
braunite. spessartite
minerals (Thadeu, 1965; Carvalho
mer,
pre-
of volcanogenic manganese oxides, hydroxides and
carbonates,
zation
with
together
deposition of the continental coal-bearing Middle
manganese
deposits
Accumu-
and mainly syngenetic from mainly epigenetic mine-
Hercynian
of
sulphide mineralization. Most of them have been mined for
secondary
extensive beds
manganese
last
ago.
neighbourhood
deposits
more
mineralization.
produced
some
than sulphide
Belt though always
pyritite
ore
a
abandoned
found
more numerous
mineralization
manganese
were
far
thin
in-
complete
to
favourable horizon.
a
géosynclinal from orogenic evolution
extensive
Iberian Pyrite
manganese
amount
are
no
therefore have
must
under the
lead
not
CARBONIFEROUS
block that
manganese
Manganese ore deposits
smaller:
along
mineral gels,
manganese
MIDDLE
Culm
Early Carboniferous
did
entered
colloidal hydrosol.
sources
for
seawater,
a
not
was
iron, it
was
as
volcanic
sea currents
at
transport and settling in situ.
one
have been worked
Belt:
as
known. Rather, the
out
producing jasper,
Devonian, caused
near
from the
away
of
exhalative product,
dispersed, presumably
Transport
Tectonic
Kuroko
shale environment, unlike
the
In
rare.
rare;
deposit, and allochthonous kuroko has
over
be
an
else
or
sulphide accumulation.
precipitation,
sulphide
de-
pyritite
rare
lava domes and tuff breccias
true
tuff is the
and
infrequent
are
the available Mn.
seawater to
of
centres
Within the Westphalian the
is
Kuroko
Iberian
the
after
had ceased
-
gradually:
elsewhere;
6.
distance from
Because
environment,
oxidizing
an
under reducing conditions
dispersal by dilution with
pyrite-chalcopyrite
bounded against kuroko. and is coarser-grained
sharply
than
-
absorbed by
galena
not
place in
some
small, exceptionally
are
took
position
Granites.
approximately
et
al.,
Many
dated and their
Middle
1970; Leutwein
of
average
et
these
age is
Westphalian
al., 1970:
van
have been
around
300
(Mendes,
Calsteren
ra-
Ma.
1968;
et
al.,
37
how
The succession of Hcrcynian phases and
unfolded
the genesis
of
Without
from having
due
extent
into detail, it
the
time
horizons
between discrete phases.
of pre-main
extent
they
it
involved
laid
local earlier
some
block
It is
consolidated
or
by
to a
used
far
large
and
refolding
the
distinguish
to
therefore difficult
true
the main
orogenic
the
to assess
affecting
movements.
So far,
of
Meseta
structures
the
phase, possibly starting during
Later
folding.
movements
be
can
the large-scale fold
during
out
that
coaxial
is still
This is
out.
tectonic phases consisted of
that
crust
main-phase
folding,
had
been
already
cleavage,
the
their
folding in post-main phase sediments, and
earlier
formations
differential vertical
horst-and-graben
Pervasive
cleavage,
several
was
tightening
1970).
and
development of
in
Lower
Carboniferous and Upper
become
gneissose (Priem
al.,
et
Older Granites, associated with the main phase,
suffered
subjected
the
with
shearing,
similar tectonization,
later
to
they
though
Thus only
Hercynian phases.
phase deformation was forceful enough
to
the
shear and
suites in time: it
two
contains
group
ralogy,
the
tween
units
valid one
Granites
calcalkaline suite
Capdevila
Elsewhere,
Granites
main-
often
calcic
Also,
gneissify
north
the
to
(according
latter
but
diorite)
Older
to
León, the main talc
Namurian limestone, the 'caliza
transformed
into
metasomatism
when
silica
talc
derived
redistributed;
most
low-grade
regional
from adjacent
talc
is
Spain.
silica
biotite
to
the
few
talc
metamorphic
deposit
mineral
Peninsula. Moreover, since the
Westphalian
Hercynian
age.
this
is
the
may
with
be classified
deposits
in
the
as one
Iberian
regional metamorphism
age
of
the
talc
is of
too.
Older Granites
In
the
northwest
granodiorites
Hercynian cycle
(Mendes. 1968;
Priem
episodes during
et
al..
the
1970):
1.
Late Ordovician
2.
Early
3.
Westphalian
ca.
4.
Earliest
ca.
460
Tournaisian
ca.
Autunian
430
Ma
350
Ma
300
Ma
280
Ma
as
Westphalian
Older
and
and
Younger
distinction originally
later
Autunian
Granites
based
on
confirmed by radiometric
These
two
suites present
granites
are
different
1956).
a
relationships and
dating (Priem
as
alkaline, leucogranitc
an
and
moscovite.
Zone
in
the
the
are
Zone
lacking in the
granites (granodiorite
Spanish
Belt).
Pyrite
in
southwest
They
to
arc
late-syntcctonic
are
to
post-tectonic
areas
of medium
be associated
from
with
to
Meseta
migmati-
with
frequently
to
fine
arc
to
little
Yet
or
no
the southern Meseta.
mediumgrained
common
too.
and
an
contain
abundant.
andesine
in
quart/
They often show
common.
latter
found
are
granitic
albitic plagioclase. and they
the
(mostly
high-grade regional
with extensive
gabbroic
most
to
concordant
rock
two-mica
but sparsely
These
to
fully
granites often
arc
leucocratic, containing rather less dark constituents than the
Younger Granites, but
dark
varieties,
south
Spain
from
gabbros and
ages
the
Older Granites also include rather
only leucogranites.
not
much
occur
mafic
more
diorites
a
are
(tonalités) and
present
as
initial
Meseta
range
are
are
Radiometric
mostly around
younger
ranging
frequent
303
Ma
(280 Ma) rocks
well.
87
Sr,
86
mainly
Sr ratios
between
but higher values
are rare
most
granodiorites.
few older (about 360 Ma) and
The
south Portugal and
granites;
to
determined by Mcndes( 1968)
but
In
Older Granites
UPPER
are
the
in
0.709
not
Older Granites of the
and 0.711; lower
values
infrequent.
CARBONIFEROUS
distinguished
(Schermerhorn.
structural
in
plagioclasc
with
al. ( 1973) granites
and granites
MIDDLE TO
The
the
rich
arc
the width of the Hercynian
over
with oligoclasc
rocks
Older
in
labradorite(Schermerhorn, 1956).
also known, especially
quartz diorites
Granite plutonism took place in various
in
may
rocks
are
porphyritic
As such, this important
Older Granites
many
1970).
the
Moreover,
the Hercynian main phase, show
occur
a
central block.
muscovite.
and
contact
Rodas.
the
character,
muscovite
1973).
of
alkaline
was
&
in
diorite and granodiorite
sediments
(Galán-Huertos
rocks.
erroneous:
Granites
range
calcalkaline
the
near
later
in
et
as
1970;
(Floor,
Spain,
crosscutling relationships with their country
metamorphism
detrital
found
shales
Westphalian
overlying
in
montaña", has been locally
dolomitization and
by
during
de
producer
is
occur
abundant
The
zation, and
in
Meseta
South Portuguese
this
a
this chemical subdivision only
south
Capdevila
to
zone
quartz
most
Granites
in the Iberian Peninsula, from the Cantabrian
orogen
the
be-
is
shown.
Ing Soen,
Portugal and
even
mine-
alkaline suite,
an
northwestern
emplaced
were
Meseta has
Oen
to
serves
distinction
Younger
1969;
trend, containing abundant albite
schists), often
Lillo
the
Younger Granites show
many
not
that either
structure,
equated with
to
calcalkaline tendencies,
andesine and
as
the
over
calcalkaline
are
biotitc and show
with reference
talc
de
the
in south
as
but
1973)
in
metamorphism.
At Puebla
contrast
(Capdevila.
al..
et
applies locally
been
have
in
leucogranites.
as
arc
crosscutting relationships,
on
radiometric dating all
as
texture,
environment. The
suites, based
two
The Older
were
granite massifs.
Westphalian
and
rarer
be realized
must
in
varying
and
composition
Granites
which have
age
The
faulting and
to
This is illustrated by the deformationof the
subphases.
not
on
only associated with the main phase, possibly
pre-main phase granites of
have
rise
situate the
tectonics.
folding
was
Ordovician
effect
of main phase folds and
giving
movements
much
are
mineralization.
northwestern Meseta also
metamor-
phism and granite intrusion. These later phases only caused
true
with
The designation of Older and Younger Granites
deformationalepisodes and whether
phase
epeirogenic
that
appears
were
of
prevalence
vician and Toumaisian granites
associated
mineral deposits.
be mentioned that the
may
worked
satisfactorily
been
to
of
scarcity
epigenetic
the Hercynian
entering
history of the Hercynian folding phases
structural
affected
they
already consolidated regions is of importance in
or
et
al..
1970).
characteristics. The Ordo-
Géosynclinal sedimentation and the deposition of syngeneic
mineral
resources
orogeny.
course,
came toan
After the
with
main
end
with
the
onset
of Hercynian
Hercynian deformation had
widespread metamorphism
and
the
run
its
emplacement
38
of the
coal
consolidated
emerged
an
Meseta
the
ago,
massif
and
continental
characterized by
Carboniferous is
the
deposits and
were
with
facies,
coal
sequences
with
start
sandstones
in continental
The
ages
of these sequences mostly range
are numerous in
These basins
of them have been
important, with
Coalfield
Spanish
from
in
in
formations
are
itself
ments
that
from
themselves
Granites
Late
As
tectonic
and
terminal
a
the
Autunian
tectonic
Stephanian. Folded
deposition,
Upper
but
granitic rocks
the
metamorphosed;
and
Westphalian
However.
mode of
Hercynian
Lower
Older
including
West-
ranging
in
granitic,
but
Stephanian,
have
not
Younger
but
not
the
late-syntectonic
and
form
are
Older
most
megacrysts
granite
and
common
pegmatites
h
Granites
a
i
7.
in
the
with
i
of
o n
merhorn. 1956). This is
megacrysts
posed
is
the
vicinity
earlier
a
older
continental facies
much
being
unknown
basins
in
Portugal and
were
movements
Permian is
sediments,
the
Upper Permian
close
to
As
granite. They
increase
northern Asturia
ted
a
Carboniferous and
worked
most
in
several
a
result, the
unconformably by
of the
fluorite mineralization is found in
older
mines,
potash feldspar
1960) play
a
Spanish
strata.
fluorite
This
with
mineralization
vein
element
superimtexture
of
megacryst
density
adjacent Younger
Granite.
giving
rise
to
sparsely
porphyritie
abundance towards the adjacent
to which
the
proximal
or
facies
is developed. Apparently both
a
is
deposits, and
production (275.000
tonnes
deduced from chemical analyses:
(as
role.
Potash-feldspathization
in
and the
panying processes of decalcification of plagioclase
and muscovitization
folded, eroded and plana-
together
the
feldspar
analyses) and metamorphic rearrangement of already present
of the Hercynian cycle.
on
potash
epeirogenic
Two
developed
in
porphyritie granite
of highly
(Scher-
granites
process evidenced by
Moreover,
underlying Younger Granite next
by large intruding
Permotriassic basin
later
metasomatic introduction of potash (as deduced from modal
Autunian stratabound fluorite
In
potash- fe ld-
as
The
in Spain.
rare
movements.
disconformably
at the
is
themselves been deformed and
Hercynian
covered
very
though coal
formed by late-Hercynian
and have
folded by the latest
Triassic
intramontane basins,
Most of it is Lower Permian,
rarer.
Permian
block
in
deposition of
earlier
Younger
few and far between in the distal facies of
are
potash-feldspathization,
continues the
feldspar
Granites or
of porphyritie
by
secondary
granites.
Coarse
potash
homogeneous original consolidation
affected
be
may
development of potash
inhomogeneous fabric
an
as
the
on
and
aplites.
large batholiths.
distribution of newly crystallized
irregular
rich,in radioac-
1956)
abundant
forms
described
process
t
a
are
and
megacrysts in cquigranular Older
Granites,
t
usually
(Schermerhorn,
abundant
widespread phenomenon
A
feldspar
granodioritic and
andesine and the mica is mostly biotite
to
biotite
is
calcalkaline rocks,
to
commonly granitic. Their plagioclase is
are
Granites
with
porphyritic
phase
(zircon, monazite, xenotime, orthite) unlike
tive accessories
associated
post-tectonic
mostly crosscutting
largely
composition from gabbroic
they
to
deformational
intruded all kinds of earlier rocks,
Granites,
varies with the distance from the
Meseta
an
place just before the deposition of the
They
with less muscovite. These granites
spa
carry
are
massifs. The Younger Granites
The megacrysts
the
(1978) admits
for these fluorite deposits.
compression of Stephanian and older
took
Autunian).
PERMIAN
of
contained relatively
Iglesias
Upper Stephanian
caused
and
synclines
the
to
the
Permian
material and the fluorite
Younger Granites
Autunian.
The
minerali-
shallow-marine
on a
already
García
origin
Younger Granites
Younger
move-
Autunian conglomerates may
regionally
the
cut
separates
to
indicating
age.
orogenic conglomerates,
the
been
be
only
can
Similarly, the Autunian
age.
post-Autunian
metamorphic and
from
was
195,000
produced
formations, due
Stephanian
phalian, Stephanian
clasts
lignite)
have taken place shortly before their
during
fluorite.
generally oligoclase
folded and deformed,
of
the Palaeozoic sediments
much
phase
thick.
very
unconformity usually
earlier
fluorite. According
syngenetic
originated
age,
where
(this
folded and cleaved older Palaeozoic rocks
on
largely
must
is,
An
present.
Hercynian phase of
consists
is
deformation
stratabound
a
The clastic
shoreline.
a
Most
phases
Hercynian
Middle
on
which sandy
on
derive from the emerged Cantabrian hinterland in the south,
respect
large central Asturian
Portugal
basal breccia
a
other rocks,
impregnated by
are
zation of Lower Permian
with
where dated Carboniferous and Permian
of Early
Portugal lies
was
later
areas
with
starts
(1974) this is
Forster
to
some
1977.
later
Stephanian B/C
movements
for coal.
Carboniferous
1977.
in
orogeny:
out
mines, is the
Upper
tonnes
ages of the
worked
and Portugal and
being worked
still
are
the
of anthracite
Permian
sediments
overlying
The
Spain
from
Westphalian
Westphalian
are
and anthracite output (excluding
coal
Hercynian
but
or
many
where
million
tonnes
in
other
some
derives
6"„ of world fluorite output)
over
Lower
The
shelf along
paralic
to
1970; Wagner, 1971).
(Ortuño,
well
epigenetic
Upper Stephanian and Autunian; some
The
orogenic
also contain oil shales.
basins
11.9
in-
Some volcanism occurred locally. The
seams.
Puertollano coalfield in south-central Spain and
B
these
in
adjacent rising blocks and fur-
from
ther contain shales and
basins
post-orogenic
characteristically
derived
conglomerates
The
movements.
troughs
tramontane
or
limestones, dolomitesand sandstones follow. The breccia and
Per-
Upper Carboniferous and
laid down in isolated
block
1976
this district.
Carboniferous limestones and
Meseta
of the
most
strata
formed by
D to
had
Upper
measures.
Over
mian
Ma
Older Granites about 300
become
need
from
contact-metamorphic
masses
to
albite
effects exerted
of Younger Granites.
aspects of the mcgacrysl development in older granites
to
be
generates
type
are
Brink.
accom-
considered here.
porphyritic
primary,
First,
granites which
the
process
must
be
ultimately
distinguished
magmatic porphyritic granites. Second,
of megacryst production
Younger Granites
is
a
contact
in Older Granites
or
this
earlier
effect of neighbouringYounger
39
and
Granites
also
ascribed
86
Sr/
0.705
in
-
contrast
Older
mineralization which
he
vary
the Older Granites -
to
assimilation.
is
as
Spain,
cordierite-bearing granites assigned
on
&
(Ugidos
Bea,
mode
more aluminous
are
by their higher
out
1962), indicative of
the other hand, occur
whose high alumosilicate content is ascribed
middle crustal levels
seems to
the Younger Granites
to
Hence
dated
genetic link
a
belonging
as
which is
to
assimilation in
1976).
Later
garded
deduced and the
mineralization
1966;
deposits
For
the
Capdevila,
northeast
associated
were
re-
of
corner
claimed
two-mica
with
the Older Granite suite) emplaced into
to
of antiforms originated
These deposits
filling
tension fractures
during Westphalian
quartz veins and
are
normal to the
an
earlier
oro-
veins
aplite
some
antiform axis. However,
the supposed association of tin-tungsten lodes
indicating
was
granites
Trás-os-Montes, Ribeiro (1968)
geny.
Granites,
coarse
the consolidation period of the parent
Granites.
eastern
the
Granite suite.
relationship with two-mica
a
tin-tungsten
cores
with
Younger
say Autunian.
to
granites (belonging
the
was
to
Older
as
Portugal, in
that
spatial relationship
investigations in Galicia (Ypma,
indicated
1969)
close
a
and related granites of the
porphyritic
from
varied
different
or a
brought
(Priem,
contents
In western
Portugal indicated
granites,
Granites often
Granites
Younger
normative corundum
sialic
equigra-
higher values. Their abundant and
of generation. The
than the
minerali-
of
of megacryst develop-
two zones
tungsten
different source in deeper levels
a
Sn-W
area
Sr ratios in the Younger Granites
to
mineralization
indicate
which
of
large
a
buried Younger Granite.
a
87
about
in
sites
are
to
Initial
coincides with
Brink (1960) mapped
nular Older Granite
ment
often
such
as
zation. Thus
with
the Older
episode of mineralization, has
been criticized (Conde et al.. 1971;Thadeu. 1973. 1977) and
Autunian tin and
Historically
been
tungsten
the Iberian Peninsula has since pre-Roman times
important
an
date
tin
of
source
from lodes and
placers in
Galicia and northern Portugal.
Spain and Portugal
minor
tin
producers
concentrate
duced
369
1977
in
now:
427
(containing
However. Portugal
t W
Europe
is an
In
1974
10,0001 W.
or
Modem
350
Cotelo
granites,
t
tin
pro-
1977 the first
by
reserves,
W
t
in
to world
were
reserves
put
at
the U.S. Geological
Neiva
deposits
ore
Tin
(1944).
pegmatites, aplites,
is
found
and
greisens
in
hy-
post-Hercynian eluvial and alluvial deposits. The
are
main tin mineral
is
minerals
they
occur,
hydrothermal
bodies
nations
origin.
with
and
The
which
of
little
over
worked.
have
lodes
are
northern
(Fig.
Portugal
2), which is
Meseta
Julivert et
lound
Galicia,
by
a
rocks
granites
or
a
zone
and
to
stretching from
Spain
western
mostly
say,
al. (1974). Working mines
northern Portugal
outcropping
Beira
Except
in
this
Schists and
and
zone are
their
are
western
either
equivalents,
of other ages.
space
and
and tungsten deposits
time
are
with Hercynian granites
in
two
not
confuse
to
To answer
nature
and
the first place,
between
biotite granites,
of
much has
too
leading
in
of the
producing
care must
mineralizing
is a
made of
granites
the
to
even
(younger)
of Older Granites.
group
mineral occurring abundantly in
Granites, and muscovitization.
supposed
a
and
incorrect assignment
cases to
some
muscovite-bearing granites
Muscovite
been
two-mica
(older)
the
Younger
greisenization of Older
by Younger granites took place (Schermerhorn. 1956. p. 244).
the
two-mica
granites associated
deposits in northern Portugal
and
grained, mostly non-porphyritic
do
tures
249).
Medium-grained
among
textures,
both the Older and
an area
in
Younger
northernmost
(1972) showed
by
a
tectonic
the
phase
which
to
is
related
the
to
Firm evidence
Granites
associated
bearing
or
in
to
as
where they
Sn
and
their
W
radiometric
dating
equally
Farinha Ramos
older
and
non-
either cycle
alkaline rocks. Mineralization
as
age
is provided only by the
aplites,
occur
rock
Stephanian
greisens
and
and
Younger
consists
of
contact-
and
potash-feldspathized
(Schermerhorn,
Autunian age
available;
veins
quartz
1956).
of these Younger Granites (Priem
the
the
strata;
either within these granites
which
stanniferous Older Granites have
yet
not
al.
from
medium-grained
younger mineralizations. For the Older
is
et
identical succession
over
Granites
defines
same
study
a
granites.
sediments
Older
muscovitized
well
minerals
country
metamorphosed
an
p.
occur
granitic cycles separated
intrude folded
pegmatites,
confirmed by
fine-grained granites,
younger
granites
caused deformation in the
granites
porphyritic
porphyritic granites
two
tex-
1956,
Granites, and the
was
Portugal:
existence of
granites. Either cycle displays
coarse
but "similar
muscovite-bearing
goes for porphyritic granites. Such
of
medium-
signify similar ages" (Schermerhorn,
not
Sn-W
with
Galicia show
and
endogenic
tin-
epigenetic
this question
age
evidence
are
of
episodes
the northwest Meseta,
closely associated
of
these
Granites this
unfortunately
been
no
et
The
al..
slightly
kind
of
supposedly
dated by
a
Rb-Sr
isochron.
ores.
The
In
contrast
1970)
for the tin and tungsten placers and the stratabound
tin
been
granites.
into
the Central
lesser proportion of Ordovician and Silurian rocks, and
strata
scheelite, the
in
of syngenetic
tectonic subdivision of the Iberian
Asturia,
Spain. Most of the
some
be
dissemi-
have
contains calcalkaline as
Massif or
with
economic
as
scheelite
well
are
replacement
scheelite
may
found in
new
Hercynian
and
post-Hercynian eluvial and alluvial
occur
Iberian Zone of the
in
other rarer
significance.
W
southern Spain
seen
and
Tungsten deposits
stockworks
wolframite and
we
as
Sn and
Galicia
not
veins,
furthermore stratabound
There also
deposits
are
quartz
mostly,
minerals,
cassiterite; though stannite
there
deposits of identical aspect'?
be taken
to
been confirmed.
not
Secondly,
in the
drothermal quartz veins and stockworks, and derived from
these
Could
(metal content) in 1977.
of the tin and tungsten
with
starts
Hercynian
very
important tungsten producer, with
0.53",, of world
study
800
halfpercent of world output.
the Portuguese tungsten
Survey. Spain produced
Meseta
a
10 in the world, contributing 2.25",,
no.
are
was
tin metal) and Portugal
t
(metal contained in concentrates) in
and
output.
output
has
tungsten mineralization
(at 70",, Sn), together about a quarter
t concentrate
of British mine production and
1010
Spain's
it
age
of
mineralization
this
has
epigenetic
been
in
granite-bound
dispute.
Studies
tin-tungsten
in
northern
Conde
et
al.
(1971) point
characteristic of Sn-W
out
that
the
porphyritic granites
mineralization in
most
ol' northern
40
almost disappear in
Portugal
the
deposits
ore
the northernmost
associated
are
with
where
regions
mica alkaline granites surrounded by contact-metamorphic
aureoles.
the
Furthermore, de Boorder (1965) has shown
northern
mica
Portugal
a.
cassiterite pegmatites
in
b.
wolframite
III.
two-
medium-grained
granite.
Whether
Sn-W
veins
supposedly belonging
Westphalian
granite
parent
the
to
of the ore,
the
Second,
with
two-mica
Older Granites
on two
is
granite
of
really
are
for Older Granites often
spatially associated granite
be radiometrically
age must
As
long
as
this evidence is
older,
an
remains
Westphalian
not
forthcoming
of
episode
in
unconfirmed and,
the
Sn-W
of
light
the
ore
formationof economic
is
yet. This evidence
et
al.
not
or
or
their
since
Younger Granites
very
petrographical
characteristics,
(Schermerhorn.
Capdevila
tiated
et
this
on
basis.
the
be
an
ascer-
no
as
Conde
by later
widespread
very
et
al.
minera-
are
as
group
Ing Soen,
cannot
1970;
be differen-
(1971) and Thadeu
period
scheelite
V.
veins
with little
or
little
veins with little
or
or
of mineralization
addition,another argument supporting this view is that the
a.
scheelite
b.
wolframite-scheelite skarns
Excluded
scheelite
be
to
appears
the
are
skarns
Cambrian
(reaction
much
Tin
but
do not
tin has been concentrated in
in
segregated
it
pegmatites
been found
indicative
of
an
important mineralization associated with these granites.
entire rock
impregnated
The
two
but
there
abundant
more
metals mostly
also are
than
tin
in
deposits in which only
of the
Byproducts
columbite-tantalite) and
well.
I
1
m
e n
i
t e
alluvial
tin
concentrate
in
deposits
(50
Portugal
u
'
in
Hercynian granites
mineral (Schermerhorn,
Sn-W
lodes
are
Granites, notably the
as
of these
one
in
appearing
or
mines
include
niobium and
formerly
o
Ti0 2) in
however, this mineral derives
The
province.
trace
sufficient
extraction.
Ta
in
the rock,
quartz veinlets.
between
in
The
0.3-2 kg
comm.).
Thus,
some
bismuth and
not
which
(which
lithium
t
in
as
from
367
produced
1976 and 175
disseminated
almost the only oxidic
t
ore
associated especially
porphyritic
with the Younger
and related granites,
is discussed below. The Sn-W-bearing pegmatites, aplites,
greisens
and
quartz veins
contacts
of these
The deposits
granite
may
be
are
found
in
the
vicinity
of" the
massifs.
grouped according
and
rite,
per
type
as
they
tonne
associated
Golpejas
mineralizationsare known
in
pers.
Galicia)
worked
near
with
variable
Arribas,
is
other
is
ore
(A.
Nb-
disseminated
district,
1978)
several
economic
The Sn and
are
(Orense
mined and
follows:
muscovite
tourmaline, beryl,
amounts.
Wolframite is
wolframite but
Tin
no
pegmatites,
simple mineralogy,
with
a
which
Salamanca
occurrences
a
of
Spain (Arribas,
contain
in
trace
albite.
main
as
and
apatite
with
in
sulphides
however,
rare;
quartz,
minerals
a
few
potash
cassite-
accessory
pegmatites
carry
cassiterite.
as
distinct from
show
the minerals listed
minerals
very
barren
pegmatites of
accompanied by plentiful
above
amounts.
the
complex mineral assemblages,
rarer
Many of these pegmatites contain
fine-grained aplitic portions (pegmaplites of
authors).
some
The tin pegmatites have in the past been worked extensively
for cassiterite,
byproducts,
In
some
with
but
pegmatites
is
columbite-tantálite,wolframiteand other
exploitation
generally
tantalite-bearing
The tin
matites
has
lower
regions pegmatites
Arga (northern Portugal)
veins
pegmatite
Portugal
to
rarely has
warrant
found finely
cases
Penouta
pegmatites
feldspar
in
1956).
coarse
tin
to
occurs.
of this kind of tin
cassiterite
at
and only
aplogranites sometimes
or
kaolinized greisen granite" (Gumiel,
1977);
from the tin lodes but from
it is
deposits
cases
other
grade
frequent
Normally
masses.
dispersed cassiterite
are
of
are
masses.
late-stage fluids which became
Columbite-tantalitealso
minerals
through
copper,
tantalum (in
is recovered together with cassiterite
ilmenite
the
Sn-W
(both from chalcopyrite),
silver
Sn-W
metallization
1978).
jointly, forming Sn-W deposits,
occur
some
metals is present, with the other absent
amounts.
this
metamorphic
their
greisens
Late-stage fine-grained granites
Tin
Tungsten is
in
vein
and
cassiterite. At
detritus
Silurian
since
often constitute large
is
other
and
disseminations
occurrence
yields 0.4 kg/t
or
cassiterite
or
older.
similar granite
contain cassiterite
wolframite
skarns)
Westphalian and Stephanian conglomerates carrying clasts of
to
cassiterite
no
no
skarns
Older Granites and metamorphic rocks have
not
tungsten
no
skarns
Metasomatic
carry
Granites
Younger
deposits
Thus Conde
there
Oen
1970:
the Sn-W
( 1973) conclude in favour of a single
In
d.
and
pipes)
known as
cut
differences,
and
Older
Floor,
1956;
al., 1973)
structural
and
between
though
even
stock works
(with
veins
Quartz
breccia
frequently intrude Older Granites and
their country rock. Secondly,
logical.
the
wolframite aplites
wolframite veins with
pegmatites, aplites and other veins.
is strong negative evidence
cassiterite aplites
hypothesis
is
are
a.
b.
c.
to
Sn-W veins,
no
Older Granites,
to the
related
Younger Granites
out,
cassiterite
no
cassiterite-wolframite (and/or scheelite) veins
other evidence,
significance
tungsten
no
or
cassiterite
mineralization
the first place,
(1971) and Thadeu (1973) point
whether
This
In
the following.
or
a.
doubtful. Incidental mineralizationmay have occurred but
important
little
with little
tes
A pi i
IV.
with
pegmatites
b.
tained.
of
greisen
or
the
are hosts
must
muscovite granite
must
truly
from an underlying Younger
emanate
Older Granite, that is, its
granites
conditions. First there
associated
spatially
veins that in reality
Granite.
associated
depends
age
be evidence that the
ore
into
grade
may
in
Pegmatites
II.
that
large batholiths
granite forming
porphyritic
coarse
Disseminations
I.
cassiterite disseminated
two-
medium-grained
have
were
the grade
abundant,
as
in the Serra de
studied by Cotelo Neiva (1954).
described
0.1-0.3
as
where cassiterite and columbite-
fields of the Amarante
been
contained
are
mostly ceased,
than in veins.
wt
by
region
in northern
Maijer (1965);
% cassiterite.
these
peg-
41
Some pegmatites attain considerable dimensions: the Latin
gares
is
pegmatite (Cotelo
Nei va,
kilometre long and
one
0.09-0.1
Lagares
12
to
up
the
% cassiterite;
wt
1944;Schermerhorn. 1956)
thick. The
m
was
columbite-tantalite
2%
is
and 0.1",, wolframite.
subhorizontal vein system, Borralha has
a
scheelite vein system,
a
produced by the
concentrate
mine contained in addition
grade
of
and
tungsten
aplites
than tin pegmatites and do
been worked
on
a
similar sizes:
small scale only. These rocks
aplites generally bearing
wolframite and/or
sulphides:
aplites
some
frequent
they have
muscovite
are
and
tourmaline,
some
disseminated cassiterite occasionally
finely
only;
attain
not
less
much
are
they contain
accompanied by
carry
wolframite
aplites show greisenization (Schermerhorn, 1956).
some
developed
there exists
tin-bearing
contact to
Though
pegmatites and mineralized quartz
tungsten veins
inside
at
veins
known between
are
pegmatites
concentrates
concentrates;
and
is
veins
and scheelite constitute
1%
rule cassiterite-quartz
veins
cassiterite-wolframite veins
wolframite veins outside
exploited by
the
the
Thadeu (1973) points
zones.
pyrite
and
and
to
be
wolframite
pyrite
tant
tend
are
present
in the
jointly. Pyrite,
outer
too
become
but
zone
contact
pass
and these
dropped
chalcopyrite
t
centrate
Panasqueira
It
spotted
Panasqueira
to
steep
northern
are
dips.
somewhat
rare:
roof rocks
granite
accompany
arseno-
and chalcomore
where
impor-
marmatite
usually
than
the jointing and
Subhorizontal veins
Bejanca
at
as
occur
as
at
and
(Sn
W)
in greisens (Cotelo
in
Neiva,
1944).
Veining
was
in many
along
vein
the
cases
In
contacts.
greisen borders in the wall
rarely
seen,
as
accompanied
host rocks
rocks
distinguished
are
sedimentary
alterations
best
host
rocks
in
are more
where
common
the
preceded by
narrow
zones
development
of
of pegmatites and aplites is
from
developed
or
generally
contrast,
bodies. Greisen borders, often
zation,
in
internal greisens in
attended
granites,
by
some
much
these
minerali-
less
so
in
tourmalinization and other
(Schermerhorn, 1956; Thadeu,
1965b).
as
small bodies
zation (Thadeu &
The
three
Peninsula
(cassiterite and wolframite)
associated with vein minerali-
Aires Barros, 1973).
important
most
are
ore
locally
the
tungsten
vein
to
are not at all
alike:
producers
Panasqueira
veins.
underground workings
This
contact
The
a
is
mine-
3
cover
metamorphism
A
in
m
3.4
by
of
zone
due
the
Iberian
Panasqueira
presents
western
the
and
Spain.
peculiarity
greisen (greisenized
about
from
more
less
or
to
a
lerite
and a
massive
due
to
contraction of
The ore veins are
to
up
Less
muscovite,
is
quartz
granite.
of the
The
m
left
and
dips
thick,
cm
at
5-20°
locally.
occur
others. The
(Reis.
increases
display
in
and
marcasite,
apatite,
galena and
calcite.
include stannite. molyb-
quantities
arsenopyrite
of
by
wolframite, arsenopyrite.
tourmaline,
topaz,
veins
veins
15
the space
steep SE
are
cassiterite.
are
al.,
dome rock.
denite, bismuth, bismuthinite, cubanite,
content
by about
in
pyrrhotite, sphalerite (marmatite)
Minerals present in small
after
et
by the mineralized
long and average 30
to
unde-
an
They mostly dip gently
minerals
abundant
fluorite,
the
m
moderate
common
chalcopyrite, pyrite,
siderite.
200
metre.
one
NW:
or
cut
deposited
was
greisenized
to
chalcopyrite, spha-
greisen dome is capped
quartz which
sagging
belong
the
6). The
(Fig.
1964, 1970; Conde
little cassiterite and is itself
The
granite)
above
m
strongly
and
greisen carries arsenopyrite,
quartz veins.
120
much larger granite massif
a
range
dome of
diameter rises
muscovite-quartz greisen
The
1971).
freibergite
most
and other
abundant mineral
The
1971).
depth and
cassiterite
towards
the
muscovite-tourmaline selvages and
greisenized borders.
Greisenization preceded mineralization. Based
Ar
determinationsof muscovites from
age
sens and ore
concluded
greisenization and
in
a
brief
for
tin-tungsten
have been produced
from subvertical
the
pressure
consolidation. As
a
Clark
hydrothermal
period, possibly
less
flat-lying joints (Fig.
vein
as
K-
( 1970)
minerali-
than
one
has
6) which
subhorizontal fractures
mass
when it
been noted,
small protuberance
is
mineralization. These joints
release caused by
underlying large granite
dome,
four
years.
The veins follow
existing
unusual
on
Panasqueira grei-
veins which yielded identical results,
that
zation took place
may
deposits in
Borralha in Portugal and Barruecopardo in
They
t
quartz
formed post-tectonic massif (Clark,
million
Metasomatic replacement
occurs
concentrate
the
silver minerals, beryl
greisenization of the
1742 t),
was
wolf-
irregular roof of
to
the veins generally show moderate
Stockworks
Portugal
later
dips.
it
mineralization consists of subhorizontal
rarely exceeding
strikes and
very
in
150
SE
are
1975
58
con-
in boreholes.
roughly
most
they
in
and
few
concentrate
cassiterite
phyllites.
The
diverging
wolframite
t
(16"„ of Portuguese output).
SW,
too
1287
was
1960
4-5% during the last
to
of Portuguese output; however,
(75%
The veins often followexisting joints, especially
cross-joints
Often
1977
Production in
years.
(«(joints) and also cleavage planes in schistose country rock.
exhibit
1-2%, again rising
to
to
and tungsten
pyrrhotite
veins
a
decrease.
arsenopyrite
). Although the overall ratio is cassiterite
of wolframite output, the tin percentage has since
Beira Schist country, largely within
where cassiterite
zone
quantitatively
of wolframite
have been
large:
mines. As
most
tin-tungsten
concentrated in the
occur
cassiterite
t
lies
and
1962 also
concentrate
area is
that marmatite and
out
3.984
concentrate,
chalcopyrite
t
km.
wolframite
granite. Sulphides
this mineralization, especially in the
since
recovery of spha-
ralized
granite.
occurring inside granite
across
1971
and
the
two.
produces
buried granite whose roof has been intersected underground
cassiterite and/or
the ore
2,848
produced (Reis,
other
Mine statistics show that between 1934
wolframite
t
the
the
1973).
carrying
studied.
and
concentrate
and
Quartz
being
1970 56,960
like
central Portugal
ramite-cassiterite-sulphide-bearing
aplites
or
breccia pipes
the granite
into each other
grade
in
wolframite and cassiterite
pegmatites and/or
outside
distance outside
ore
quartz veins (Thadeu, 1965b,
tin
just
or
some
the different types of
transition is
no
zonation from
a
veins
quartz
veins
mine
argentiferous chalcopyrite
1176
Where both
wolframite
not
The Panasqueira
lerite
Tin
two
and is exceptionally rich in molybdenum, and Barruecopardo
on
resulting
slight sagging
of
contracted
during
the
greisen
shrinking
of
the roof of the main
granite
42
Fig.
6.
mass,
through
Section
left
a
that
space
formed
joints
the
vein
Panasqueira
system
and the
due
filled
was
to
release
until forced
here
as
suggested,
by overpressured
open
vein
solutions from which the
hydrothermal
The
by hydrolhermal quartz.
pressure
latent
possibly remained
minerals
were
deposited.
1967). According
the
inclusions in
(80-325
fairly
saline
for the
(3-10
in
sulphur
the
sulphur;
of
have
to
appear
deposition of
and
carbon;
been
km
were hot
of the
isotope
a
shallow
the
during
for late-
source
substantial
a
hydrothermal
pro-
fluids
predominantly magmatic during
the
deposition
of others
&
the
and
meteoric
(Rye
a
Kelly.
Fluid inclusions
in
zation indicate that
above
the
The
it
temperature
a
to
of 230-315
70
of the
3
11
vein
later
reveal
a
to
was
a
mentioned
or
°C)
",, equivalent
systematic
(siderite.
decline of
of mineralization entails
depth
turn
is
risen to less than
implies, first,
not
unusual
Beira Schists.
a
very
for
1.7 km
high level
the
and
Early
the Late
causing elevation of
denudation. The
tain
Beralt
Tin
Wolfram
and
truded
granite
a
thickness
preceding
sea
certainly exceeding
section,
level and
were
a
high
tectonic
erosion
differentiation
the
started.
As
at
central Iberian
After the
main
in
outside the basins
which
the
Stephanian conglomerates
the
in Portugal
con-
Older Granites
in-
schists
regional-metamorphic
an
rate
of erosion and denudation in the uplifted
of the Stephanian. It thus is perfectly possible for
source areas
Upper Westphalian-Stephanian
Beira
cate
Schists
a
at
kilometres of overlying
level
deep
level
stratigraphie-structural
The
B o
second
r
r
a
largest
centrates.
h
1
mine
a
scheelite
90%
of
and
tungsten
and
in
regarded
granite
the
as
in
argentiferous
that
scheelite)
adjoins
parent
The lodes, up
1.5
to
m
at
E to
at25
N,45-60 Nand50
extensive
the
Two
other
/one
veins
veins
et
al..
980
ppm
chalcopyrite) (F.
The
veins
pyrite and
(in
Mo
carry
very
blind,
breccia
are
rock
is
regular
pipes,
one
of
principal
rare
them
cemented by ore-bearing
molybdenite)
molybdenite, scheelite (and
some
dipping
veins
and
1300
415
ppm
ppm
Cu
(in
coram.).
wolframite and sulphides (mainly
as
this
near
N(Noronha, 1974:Noronha&
large
Noronha. pers.
pyrite)
of tin
granite
1971 ).
quartz. The recently discovered blind pipe contains
W.
the
con-
(with
Borralha. The country
ESE trending mineralized quartz
1975).
deep
for about
of porphyritic
thick, form an extensive,
system of
30
chalcopyrite
wolframite
to
a
Portugal,
accounts
cassiterite
magma;
worked
arc
it
An
massif
a
of Panas-
the Peninsula, produces
with Panasqueira
outwards
pass
shallowness
northernmost
Portuguese tungsten output.
veins
trun-
emplacement.
tungsten deposit
Together
to
removal of several
inconsistent with
not
of
surface
erosion
after
The
strata.
queira mineralization hence is
outcropping,
m.
tectonic
two
ensued, dur-
likewise formed shortly before, during the Westphalian. This
intruded
500
least
nature
laid down, hence strong erosion and
before and from
shortly
Saavedra,
this
at
Stephanian (Schermerhorn. 1956).
areas
detritus derived from
plentiful
Younger
Before erosion,
the beginning of the Carboniferous raised
above
280
overlain by Ordovician. Silurian and Devonian
combined
in
wl
at
minerals
and. second, strong denudation. The
sequence
block
the
ing
granite and Silurian schists (Conde
must have
that
into folded and cleaved
strata
(peaking
C.
underlying magma
emplacement but
granites
in
temperatures in
at
°C'
of about
salinity
below the surface. This in
of
deposited
was
others)
below
assessment
Kelly's
apatite accompanying the minerali-
fluid inclusions
Iluorite. calcite and
that the
the
range
from fluids showing
NaCl.
After
epeirogenic, block-faulting
an
wolframite,
1974).
slightly
(black).
the Westphalian.
orogenic phase during
phases of
indicates
con-
data indicate
minerals but mixtures of
some
during
magmatic
1.5
carbonates contain
organic
fluids
ore
the sulphides formed
the main stage of mineralization but
stage
various stages
"„ equivalent NaCI)
wt
place within
surface. Stable
temporaneous ground
in
place
(1974). study of the fluid
vein quartz shows that the
C) and
juvenile origin
took
Kelly
to
while mineralization took
portion
its quartz cap
Stephanian deposits
Hydrothermal mineralization
(Orey.
dome with
greisen-granite
S.A.R.L.
Portugal.
minerals,
chalco-
accompanied by
powellite). marmatite. arse-
43
other
nopyrite.
Study of fluid
admit
to
inclusions
lished
a
around
this
derived using the solid
this
Using
the
However.
figures pub-
Amossé
value
fluid
estimated
(1976)
has
of crystalli-
pressure
of
pressure
crystallization
that
the
to correct
inclusions
the
in
Borralha
at
at
Borralha.
homogenization temperature
the
quartz host
wolframite
temperatures between 325 and 430
of the
he
ore,
deposited
was
C, the temperature
at
gra-
dient being correlated with distance from a breccia pipe as 'hot
of mineralization.
centre'
load
place
would
pressure,
at
depth of
a
Further, according
a
is
deposits
ore
equivalent
20
the
overburden
the
years
not
appear
impossible
in
view
under
Saavedra
of
the
which
(1975)
at
C under a pressure of 4.5-5
17-19
the
separating
a
the
metamorphosed
km.
mctamorphism. it
at a
Given
means
time
rate
of
12
some
millimetre a
depth of
figures
of
that
meta-
of
14 km
400
a
700
m
Such does
year.
rather
high.
of breccia
presence
the
mineralization deduced
seems
wolframite
exceeding
overpressure
km.
tectonically active environment of
a
the
from the above pressure
in
the
years
less than
or
Still,
block-faulting.
5.7
respectively
were
removed by erosion,
was
took
depth of
a
if taken
pressure,
mineralization
time of mineralization
million
pressure
of
age
per
admitted,
to
30 million
morphism and
km,
Noronha and
to
Middle Westphalian
during
that
3.8
temperaturein the order of 650
kbar. This
for the
figures
indicate
roughly
Silurian host rocks of the
formed
lithostatic
that
pipes,
was
if it is
But
the
hydraulic
a
hence
pressure,
not
correlatable with depth, then the depth of mineralization was
even
less,
an even
or
say one
rate
greater
km
two
as at
and this entails
Panasqueira,
of erosion, almost
reaching
a
millimetrea
year.
Conde
emanated from
ger
a
Granite suite.
long
after the
al.
et
tend
(1971)
km
Borralha
or
over.
Younger
confirm
to
that
the
An Older Granite
veins
Hence
could
this
at
the Youn-
mineralization
too
its
run
the
have formed at
not
view
would have intruded
regional metamorphism had
ore
the
mineralization
porphyritic granite belonging to
when little erosion could have taken place
the
the
positive
is
not
course,
surface, but
a
depth
related
of 10
to
the
Granites and of Autunian age.
in
occurs
In
the
Spain
of
largest
the
correlation
tungsten
northwest of Salamanca,
occurrence
veins
litero
is
a
near the
0.5-15
cm
thick,
al.. 1975). This stockwork
wide and
100
the
scheelite
open-cast
frontier with Portugal.
m
deep (Arribas.
developed
between
itself
is
over
1978).
3 km
The
long by
underlying
the
older
lutions
granite
veins
are
minera-
lized by scheelite and arsenopyrite with subordinate ferberitic
potash feldspar
two-mica
al. (1975,
note
related
the
to
the
zation and difficult
to
ore.
from
the
replacement of
explain
unique, the
more
beds
in
the
is
linked
uniformly
was
granite
the
It
aureoles,
contact
size.
large
due
rock
such
of the
minerali-
epi'genetic
to
in Cambrian and
such
reaction
to
formerly
as
min-
of calcareous
occurrence
seen,
they
are
in-
Silurian
calc-
found outside
the occurrence
as
aureoles
contact
metamorphosed
abundant than
more
fact. Barruecopardo is
the
cited under
scheelite.
heading Cambrian
Within the
Because
hypothesis.
Silurian country
where
especially
of
presence
has recently become recognized that
tungsten exists
silicate beds,
the
to
regarded
troduction of tungsten.
syngenetic
In
of its
have
we
such
have
occurrences
skarns.
and
these
are
been
hard
distinguish from contact-metasomatic skarns (or tactites)
which
the
tungsten
scheelite
and
has'been
sedimentary
scheelite deposits
are poor
lime.
in
the
Covas
northwest
syngenetic
and lack wolframite
deposits
important
contain
both
sul-
the
in
the
extreme
them
Valdarcas,
being
are
very extensive skarn horizon developed
intrusive granites;
in
situated
Portugal, several scheelite deposits, the
among
a
of Ordovician
occur
district
mining
of
corner
associated with
lites)
in
introduced
the
Normally
sulphides
to
and wolframite.
phides
top
from
produced
while the metasomatic scheelite
In
in
so-
widespread in the Meseta
rather
and
Beira Schists
Younger Granites. As
zation
The
an
zones
scheelite-wolframite
Skarn-type
eralization
is
case.
because
so
either
on
be
to
the
also
unusual in this type of minerali-
plagioclase
is not
it
older by
an
mineralizing
granite.
younger
granites, scheelite ought
for
pathways
most
a
and
content
extracted
was
1976)
They
microclinization: scheelite
during
provided
microclinization of
quartzite
a
large anticline
barren aplitic
many
area.
in
near
on
two
pegmatites (pegmap-
The skarn consists of calcite, grossular-
rich garnet, diopside. vesuvianite. actinolite-tremolite. hornblende
and
other
minerals.
contain in
addition
scheelite),
wolframite,
the
zones
Conde
m
a
granite took place and that shear
younger
predominant scheelite is
This
200
et
process.
that potash-feldspathization of
possible
prefers
in granite (Pel-
as
plagioclase by microcline released calcium. However,
mine
system of parallel NNE-trending subvertical
averaging
et
is
producer
and Pellitero
place,
precipitated instead of wolframite because
apatite, fluorite,
Barruecopardo
granite described
a
they infer that the tungsten
seems
and
trace amounts.
tungsten mineralization to this
a
scheelite.
rich in
the
et
al..
in
100
m
long
much
labradorite).
to
pyrrhotite.
with
sulphides. Wolframite prefers
where scheelite is
at
Valdarcas
was a
that contained
ore
pyrrhotite) wolframite
The
zones
rare
and
scheelite
1968:
1971).
silicate-rich scheelite
scheelite.
other
skarn
which calc-silicates prevail (Bayer.
The orebody worked
and about
mineralized
ferberite (pseudomorphosing
quartz and
sulphides
zones
The
plagioclase (albite
little
arsenopyrite. pyrite and
stockwork
cassiterite
chalcopyrite;
some
which pronounced microclinization of biotite
plagioclase took
relate
most
These calculations incidentally
expressed by
stockwork
wolframite, which
Noronha's and Amossé's
as
The
adamellite in
and
present in
are
surrounding granite
be
can
equation. Thus Amossé arrived
state
molybdenite
hence
after anneal-
strain is measured by X-ray
remove
wolframite, pyrite
and
at.
value from
of 1500 bar for wolframite formation
pressure
of 280-
from this value and the compressibility coef-
ficient of wolframite the
of
the order
variation in wolframite beforeand
methods, and
a
1000
pressure
workers.
high temperature to
at
quartz led Noronha ( 1974)
vein
method of measuring the
new
zation: lattice
ing
the
in
pressure
Russian
by
evolved
a
estimated
Noronha
and
apatite
al. 1971; Noronha & Saavedra, 1975).
et
temperature of formation in
a
C under
350
tourmaline, white mica,
sulphides,
carbonates (Conde
lens
up
to 8 in
kinds of
two
ore:
thick
calc-
("skarn ore') and sulphidic (mainly
ore
with scheelite
and
sulphide ore formed the main
ferberite after
mass; calc-silicate
44
ore occurred
as
bed
a
1.5-2 m thick in
the
sulphide lens. The grade of
wolframite-scheelite
tonne
per
Bayer (1968) envisages the
Valdarcas
rock
eruptive
bolite
follows:
as
the
ore
0.18-0.25",,
of mineralization
metamorphosed
scheelite
volcanogenic
lava
and
arsenic existed.
the
the scheelite in
redeposited
In
to
in a
mafic lava
iron
sulphide
crystalline
to
Conde et
some
aplite-peg-
mobilized
was
zinc
and
pyrrhotite
in
part
al. ( 1971 ) consider the skarn
since
borings revealed its
limestone
mineralization which
wolframitic mineralization
is
its
by
normal
a
by the Covas granite.
generated
Thadeu (1973) further remarks that volcanics
this
vesu-
copper,
and
became
limestone, and this
channeled the
reactivity
Their
tungsten deposits
association
apart from
the
host
The
rocks.
unusual. The
lacking in
are
unique
are
Ordovician
in
the
Peninsula.
calc-silicates
scheelite orebodies in Cambrian
presence
aplitic pegmatites
occur
with
lack
of
vast
a
seems
the Covas
them
sets
Silurian
or
pyrrhotite
is
closely associated
very
curious, especially
near
of
amount
of cassiterite in the
in pegmatites
cassiterite does
as
maline
frequently
deposition, that
is.
parent granite (which need
rock)
and
during consolidation of
not be
the metalliferous fluids
tin-tungsten concentrations
eroded
or
their
move
actual
upwards,
with
granites
are
found
steep
contacts
not
sidewards,
the
richest
Deeply
contacts.
unfavourable
are
shal-
unexposed
over
the
host
granitic
Hence
gently dipping granite
over
characterized by-
are
accumulate in the roof of the pluton.
low granites
explo-
ration targets in contradistinction to contact-metamorphosed
sedimentary
or
older granite
areas
with
little
or
no
younger
granite outcropping.
Tin and tungsten became concentrated
nation
processes
in the granite
magmas
enriched hydrothermal fluids,
constituents,
stage
However,
together
extent
but not
When fissures
opening
at
high-grade
into
the
with
metallization
the
late-
greisenization.
is
linked
are
Apatite is
rocks
than
Tungsten
than
it
is.
Some
the
on
the
of
lodes
aplites
too in
and
widespread,
are
the tin
and
tour-
joint planes.
on
tungsten deposits.
to be
plentiful
more
for instance, in the lodes of Cornwall.
show enrichment
occurrences
the
Thus
rocks
wall
Borralha
molybdenum
compared
as
locally plentiful
Spain (see
in
other
to
cassiterite
in
is
deposit
tungsten
certain
rich
in
is
Lithium
occurrences.
for example
veins,
elements.
relatively
in
western
section).
next
Autunian
beryl, columbite-tantalite,
Minerals
containing Be, Nb-Ta and Li.
are
spar,
A
province.
freto
a
contact
are
tin
which
is
originates
less
mobile
within
or
the
the Iberian
setting
or
Golpejas
apart.
For
of
variety
great
phosphates occur in
the
with
together
Iberian
feld-
tin-tungsten
and
iron-manganese
other
of these pegmatites (Corrcia Neves.
many
I960).
products
and
of
columbite-tantalite
tin
or
but
mining
columbite-tantaliteand
Conde
al..
et
northern Portugal has
carried
a
Neves.
1971).
been
rich
pegmatites
for beryl
little cassiterite and iron,
and
it
lithium
and
manganese
in
appear
pegmatites and aplites
western
in
Spain. Moreover, amblyveins
oc-
Spain (Weibel. 1955).
western
of
in
feldspar;
1933).
minerals
Portugal produced
byproduct
1973.
1965.
gonite and montebrasite-bearing cassiterite-quarlz
locally in
or
little
Mangualdc pegmatite
worked
Galicia, north Portugal and
cur
by-
beryl
contain
Thadeu.
1960;
The
be
can
in
phosphates
manganese
cassiterite (Correia
no
1977;
lepidolite! 1.5",,
lOOOt
0)in 1977 asa
Li
2
feldspar exploitation (Bol. Minas (Lisboa). Dec.
1977).
is the
Usually lepidolite
(Conde et al..
common Li
minerals also
zone
600
veins
in
for
Henscn
occur.
wide by
m
15 km
but
to
0.2
wt
and
Pegmatites
t
quartz
feldspar
in
Portugal 28.000
t.
had
10,803
declined
to
have
some
1974
in
t
extensive
the
in
addition.
occurred.
important
Peninsula.
9 in
1977
been mostly mined
columbite-tantalite.
most
(no.
However, in
an
for beryl;
petalite),
furthermore the
and
feldspar
cassiter-
amblygonite and other
other minerals
many
are
pegmatites
of metalliferous pegmatite
"„) and
and
Li-minerals (spodumene
phosphates
in
(1967) described
long
micaschist in Galicia. These
cassiterite (up
-mineral
and lepidolite pegmatites, often
1971 ).
ite-bearing as well, are widespread,
this
the
disseminated low-grade high-
in western
tin-tungsten province
it
in
granite
because
deposits in greisenized granite,
in northwest Spain
in
from pegmatites
won
andfeldspar
lithium
world
source
Spain
of
pro-
production) and
Portuguese production
feldspar (and
103,565
t
quartz).
penetrates farther
in the absence of late-stage fissuring
characteristics
frequent
very
the
Among the sulphides, marmatite appears
duced 70,000
granite-wall rock
low-volume lodes.
volume cassiterite
lastly,
several other
inseparably.
crossing
earlier veins close,
nouta
halidc-
this late stage they become mineralized,
producing
wall
zone,
fractio-
mineralization
situation. Retention of stanniferous fluids
roof
by crystal
in volatile-rich
including those causing
greisenized granite lacking
quent, and greisenization and
certain
other
to
Tourmaline,
41).
p.
in
in quartz veins and
occurs
phosphates (Jesus.
granite.
tungsten lodes ofgranitic descent
apical
comparison
have formed. Also, unmineralized
may
tourmaline pegmatites and
Lithium
Tin and
in
rare
1971.
al.,
et
where tourmalinites
Beryl
Covas
distinctly
536. 560; Conde
p.
region.
The
is
wolframite in the sulphide lens.
metasomatizcd limestone,
passage
it
occur,
Hercynian tin-tungsten belts in Europe (Schermerhorn, 1956.
tuff: below this
or
containing
metamafic horizon
as
contradistinction.
be
garnet and
During metamorphism
matite emplacement the
and
amphi-
syngenetic origin, preconcentrated
submarine iron-sulphide
a
to the
at
mafic
or a
crystallization of diopside, hornblende,
vianite. The tungsten is of
does
other hand, is abundant, mostly
plagioclase and possibly also grossular-rich
as
WO,
W.
sequences
and
2.5-5 kg
was
intercalationof either marl
folded
was
with
facies
an
hanging wall of the
or
ore.
1968), that is 0.14-0.20",,
(Bayer,
the
Valdarcas
as
at
Pe-
Spain.
presents certain
instance,
though
topaz
Autunian
Gold
gold
and
silver
and silver, likecoppcr. tin and lead,
Iberian Peninsula
placer gold
anymore
were
since
exploited.
in Spain;
sulphide deposits
Belt
No
the
gold
these metals
products from other
Pyrite
before
and
accounts
ores
(gold
their
for
have been
Romans.
or
are
silver
Both
mines
still being
won
in the
vein
are
won
and
active
as
by-
and silver from cupriferous
gossans
(Cerro Colorado
90",, of Spanish
gold
in
the
output) and
45
silver
from
sulphide deposits; with
lead
of production of these
from these
too:
in
and 170
the
active
Portuguese
grading
Minas
gold-silver
mine
of
and
output
(Lisboa), December
formerly
In
Portugal.
y
r
Galicia
i
the
silver
to
671
Ag
a
is
The
by
Pedro
de
in
situated
Jales
Gold
veins
Brink
vein systems
Here
Beira
in
occur
gold-
Schists,
Ordovician, Silurian and Older Granite country rock, in
where this
area
plentiful
which
potash
is
no
have
megacrysts
porphyritic
longer in exploitation,
trend
WNW
and
northwards
occurrence
the
Minas
Tres
vein (Minas dos Mouros) which
NE
across
the
Beira Schists
are
and
are sited
in
of
disused
gold
1970
14g,tAuin
associated
with
with
1
m
produces gold
thickness.
ore
1971
(Portugal Ferreira.
with
sulphides
and the
the
same area
silver
is
of
was
). The gold is mostly
two or
contained
in
and
to
a
lesser
galena and
of
this
and
as
solutions
ore-bearing
silicification.
Another
which
also
caused
the highly
has
been
Brink attributes
muscovitization,
sulphidization and tourmalinization.
gold-silver veins of the northwest Meseta
are
regarded as Hereynian deposits but their precise
age
clear.
Some
related
the
to
authors (Cerveira.
the
presence
of wolframite
earlier,
to
the
quite
vein
the
scheelite
that there exists
separate
phase
Older Granites. He
Campo
also,
was
or
mineralizations: the
two
generally
is still
are deformed
wolframite
gold
of ore
no
and
veins
in
gold
on
mines. Brink's
well
account
the
Because
gold
by
potash
is
alterations
feldspathization
it
seems
more
genetically linked
to
the
(Harris, pers.
represented
by
duced
decreases.
Younger
associated
Granite
with
molybdenite and
mineralized rock,
Na
destroyed,
C0
and
traces
Mo
texture
and
This
and Si0 2 from the altered
occurrence
Salave mineralization
further that this type of
is
prospect and this
a
may prove
gold deposit
to
of
pro-
granodiorite
igneous
increase
2
age
arseno-
Peripheral molybdenite-bearing quartz veins
ferous bodies.
the
some
altered
represent remobilized
that
of
is
gold
zonation: from the unaltered
highly
progressively
Salave granodiorite stock in
galena. Alteration of the granodiorite
complex
a
towards the
of the
intrusion
stibnite,
and
sphalerite
described by Harris (1978) for
as
comm.). The
pyrite,
pyrite,
portions
Hercynian
is
mineralization
gold,
is
SiO,
may
auri-
means
be economic and
be present elsewhere
may
too.
Autunian
antimony
and
Antimoniferous veins
Spain and.
western
They
are most
km
lying
in
east
in
was an
northern
Portugal,
Portugal, northwest
veins, of which
been worked
poor
in
a
of Oporto
width of
a
up
in
south Portugal.
southeast-trending
that reaches
10 km.
to
the
largest
for
gold by
some 30
Here auriferous
the Alto do Sobrido
was
in
gold but rich
the
Romans.
stibnite and
The
the
veins
district
important antimony producer during the second half
of the last century;
The
northern
lesser extent,
and southeast
length by
have
in
to a.
abundant in the so-called 'antimony belt' (faixa
antimonifera)
zone
gold
occur
host rocks
it
is
now
inactive.
of the veins
are
Ordovician quartzites and slates,
mostly Beira Schists and
in
and Carboniferous conglomerates,
Granite
Kerreira
et
al..
The
age
1971).
and Pb-Zn-Ag vein
The Sbtrends,
Au
Sb-Au
(Portugal
In
this
rarely Silurian slates
more
the limbs of the
vein
mineralization
Ferreira,
area occur
1971;
of
Portugal
mineralizations..
frequently
wrench faults), that
is
furthermore Sb-Pb
mineralization occurs in quartz veins of
most
large
reach
ENE-WSW
2.5
m
(following
thickness. The
varying
dextral
mineralization
consists of stibnite, berthierite. gold, pyrargyrite. pyrite, and
silver
locally galena, sphalerite and arsenopyrite (Portugal Ferreira,
the older
belong
to
an
related
minerals in
the
1971).
The origin of
the younger minerals are not;
ascribed
the
activity
area
of
recurrence
connection between
deposition possibly
argued that
while
in
not
directly
see these veins as
affected
gold
Valongo anticline.
Hereynian tungsten mineralization, based
(1960) opinion
the
1952)
of
altered
a
Younger
The
minerals.
mineralization too
type
mine,
microcline
well:
older
could
underlying Younger Granite,
disseminated
were rather
plagioclase,
the
area
an
this
likely that
antimony
as-
metasomatic introduction of potash feldspar from the
to
in
occurs
generated by
three times gold
galena.
introduced into the schist wall rocks
of
deformation
tetrahedrite
The Older Granite wall rock of the Campo vein has suffered
microclinization
it
and
(chalcopyrite.
sphalerite). Jales production of silver is
sociated with
In the
pyrite
mineralization
during
dextral wrench
a
Ferreira (1971), and
It
Granite and
extracted from the Campo vein
arsenopyrite. also
younger
production
silver.
and
Older
small cassiterite deposits.
of the
grade
extent
an
Gralheira
schists. Somewhat more
between
contact
Beira Schists and reaches
The
it.
in Silurian schists. To the south is the long Campo
workings
trends
in
effects of
The
Granite.
Younger
basal Ordovician metaquartzites
is
developed
the contact-metamorphic
to
an
has been potash-feldspathized. that is.
feldspar
ascribed
underlying
veins,
granite
the
emplaced along
was
Portugal
movements
Asturia,
(I960) and Portugal Ferreira (1971).
to
in
mine in northern Portugal has been described
silver-arsenopyrite-quartz
minor
for
Campo vein
according
Younger Granites.
Campos Julia, 1971).
&
the
of the type generally caused by Younger Granites and because
bismuth and bismuthinite; silver is also present
chalcopyrite,
fault
posterior episode of vein dilation.
a
Still,
mine
gold and arsenopyrite in association with pyrite, pyrrhotite,
(Armengot
during
old
workings.
León) and northern
worked.
of
mineralization is clearly associated with wall rock
gold-silver-arse-
been
deposited during fracturing
were
(Bol.
within and around granitic plutons and contain
occur
ores
1977
very
Roman
district
Asturia and
have
is
the
of
concentrate
2,0211 in
was
This
extent
numerous
veins
sulphide
as
older
gold-bearing
the Older Granite, and the undeformed later minerals formed
6 t Au
produce
Iberian Peninsula, and
gold-silver
(Galicia,
this area
t e
1977).
enormous
important
northwest Spain
no p
gold
in
g/t Au and 377.8 g/t Ag
133.8
remarkable for the
A
mount
Ag in 1980). The Jales mine in northern Portugal is
t
only
will
Spain produced 320 kg Au and
sources
and expects (Prado Calzado, 1973)
1970
planned increase
the
gold and silver output
ores
show
no
signs
of
deformation. Brink therefore concluded that the cataclastic
or
the
to
and
to
volcanics.
the
mineralization
is
Younger Granites,
remobilization
uncertain: it has been
to
later
of antimony in
hydrothermal
older
sediments
46
Stibnite
the
local
veins
carrying
worked in
the Valle
de
gold and silver, emplaccd in
some
of the
equivalent
Beira
Schists,
have
southern
Alcudia in
been
also
Spain (Crespo.
Gumiel
al.
et
(1976) described
trending stibnite-scheelite
Antonio mine
authors assigned
this
to
veins
an
in
in
Albuquerque
near
belt
the
traversing
direction from Oporto
Other
vein
antimony
southern
to
and
Portugal
110
with
these
to
antimoni-
an
in
NW-SE
a
Valdepeñas.
mineralizations
Spain
western
Morena:
Sierra
in
northern
much
are
and
less impor-
Quartz-stibnite
veins
containing
amounts are
fairly frequent
been
on
mined
small
a
elsewhere, and locally
in
in
sulphides
some
trace
in
Ciudad
Real
and
province
in northwest Spain.
several
galena
and
zinc
from
in
widespread
the Meseta. Their
in
is
age
part argentiferous,
The richest and
most
argentiferous lead veins, that have been
times
area
Meseta is
Morena of central southern
2). Here metalliferous lodes, especially
Spain (Fig.
found
are
north and
in the
of
east
Los
it.
lead and
worked since
At
1971).
present three
field
t
in the world
lead
ore
veins
of
North
(60-80% Pb)
Linares
still
are
granite
a
veins of great
and
pyrite
extent
chalcopyrite in
vertical
A
150-300
zonation
massif
in
the
12 km
(
for the
a
the
in
rich
zone very
lead
100
present;
lead:
150
300
m:
La
in the
small Fontanosas stock,
andesine
diorite (containing
been dated
0.7099
age
known;
not
10
302 ±
at
(Leutwein
et
Ma
late
a
and
with
50 km
some
post-tectonic
or
initial
87
Sr/
isotope
ratios
The
some
Los
tin
nor
the
central part
and the
mined
of the
in
former
veins,
(Ovtracht &
to the
Carolina extends
a
mineralized
west,
first,
the Los
especially in its
along
side
only
some
wolframite,
tungsten
the southern
a
outcrops.
a
large number of
part, and
a lesser number
170-250 g/t
Ag).
copper
veins)
of lead
Lead veins
following
batholith. Along the
tracht
&
are
veins
more
contact
occur
Bi-
the
granite (Crespo,
lized
carbonate
El
central
Soldado-Las
and
abundant
part
Morras
ESE to E-W
of
(Crespo,
the
1972).
batholith
orefield,
a
vein
directions; only the
is
system
NE
veins
El
trending
rock
contact-
the
ore,
accompanied by
(Ov-
gangue
Valle de Alcudia, all these mineralizations
north
de
ofthe
Valle de
1972). The veins trend
and
vein
system, is in
Alcudia, far from
E-W
and
are
minera-
to
3500 g/t Ag), black
in
quartz
gangue
barite (Ovtracht
rare
very
important lead field,
an
Calatrava)
&
with
Tamain.
Ovtracht and Tamain ( 1973), as
does
Crespo ( 1972), relate
the Cu, Pb and Sb mineralizations in the Sierra Morena
a
particularly
more
porphyritic biotite granite (rather
desine
exceeds
potash
zation is zoned,
out.
Sn and
These
covered
with
the
deposits),
1973).
&
the
with
W are
are
late
Cu nearest
related
to
be
1971).
associated
La
Santa
granodiorite,
The
the granite
to
and
Carolina
Elena
an-
Pb farther
fine-grained two-mica granite.
The
and
as
minerali-
sediments (Tamain,
with
the
to
of its phases,
Hercynian mineralizations: the
Arguelles.
to
a
a
one
in amount).
feldspar
by barren Triassic
Santa Elena,
are
consisting
NNE
quartz-ankerite-barite
by highly argentiferous galena (up
Schists)
NE
the
Alcudian country rock
broad plain where the Alcudiense (Beira
the
and
San Quintín (Villamayor
thought
of
constitutes
Ag)
associated with granite: however,
Valle de
lead veins
to it
&
Tamain. 1973).
extends the
Here
g/t
Except for
are
cárate
batholith and parallel
the
south
important
the
1500
to
sphalerite, pyrite
in
contact
poor zone;
area
Silurian country
sphalerite, pyrite and somechalcopyrite
veins.
Ni-Co-Ag-Au
North of
of
(up
Los Pedroches batholith,
encloses
eastern
Ordovician
rare
in the Lower Carboniferous slates and greywackes
on the north
Just
also
in silver:
poor
Alcudia,
scheelite.
cross
greisens,
west
m
zone:
Guindos deposits and then the
found in
chalcosite-chalcopyrite-carbonate-quartz
(
frequent
farther
are
Tamain, 1973).
The batholith
(galena
massif;
Cassiterite-
days.
cassiterite
part of the massif has
east
places accompanied by
veins
neither
result
100
metamorphosed by underlying granite. Argentiferous galena
the
Pedroches batholith contains several tungsten and
occurrences,
wolframite-arsenopyrite-quartz
occurs
with
for Older
veins in the area!
ore
wolframite pegmatites and scheelite pegmatites
the
has
Sr ratio of
measured
Granites elsewhere in the Meseta. However, this
dates the Los Pedroches rocks
86
well
al.. 1970). This age accords
and initial strontium
grano-
cordierite) that
some
an
the north is
to
gangue.
lo
Santa Elena granite (the Santa Elena
or
precise age is
carry
again (Ovtracht
lead veins
Its
veins
barren
a
400 m: a
increases
tenor
con-
to NNE
of sphalerite,
from the surface down
of intrusive granite and
Tamain,
eastern
amounts
ESE. respectively
&
the
Arrayanes vein,
Centenillo deposits, where
granodiorite (Ovtracht
in
worked
being
the La Carolina field (Ríos
quartz-barite-carbonate
a
exists:
copper are
m:
North of
pre-
large
output
Tamain. 1973).
and
very
m:
400
below
the
1905. this
ore
of the richest lead veins known anywhere). The
batholith
a
in
lead
was
U.S.A.),
tinuationof the Los Pedroches batholithcontainsNE
of veins
is
the
(after
1907; Azcárate & Arguelles.
in
and three others
the
Carolina
1977).
Aragües.
Pedroches batholith and
This
La
elongated. WNW-trending massif composed of various types
the
&
most
end of
east
beginning of the century, when Spain
1300 mines
(Ahlburg,
some
depth lead and
famous lead province of the
Sierra
eastern
Roman
are
always evident and
certainly post-Hercynian.
are
and
galena (with 160-250g/t Ag) and lesser
not
and 1920 the
the
at
supplied nearly half of the Spanish
trending
and silver
Epigenetic lead and lead-zinc veins,
1973).
kilometers
and sphalerite,
quartz (Ovtracht
1875
lies
Linares
with for instance 265.500
one
Autunian and later lead,
At the
orefields.
southern Spain where they have
scale
the
second largest lead producer
Linares
in the
of
carbonates
productive leadfield in the world,
region
tant.
the
pyrite, chalcopyrite,
reach
they
consists
The richest lead district, between
-
Hercynian origin
Meseta
western
Spain;
western
late
juvenile epigenetic,
a
of
occurrence
Devonian limestone, the
mineralization, which they related
ferous
some
mineralized and
length. The mineralization
Tamain, 1973).
1972).
San
richly
are
Linares
the
are
Az-
mineralization
Linares
neighbouring
granite (Tamain,
veins
1968:
is
granite, and the
mineralizations
1968; Ovtracht
&
Tamain. 1973).
In
northern
Portugal
mineralization of different ages
are
two
types
of
distinguished:
lead-zinc
the
first
47
in
occurs
type
the
southeast
area
of Oporto
mines worked argentiferous lead-zinc
mostly
Terramonte
is
This type
(see hereafter).
Beira
metamorphic
in
emplaced
known of these is the
Schists.
silver
tenors,
a
complex
of
presence
is
high-temperature ferriferous sphalerite (marmatite) which
earlier in
paragenetical
common presence
of cataclastic
of late Hercynian
age.
The second type, occurring
has
Portugal,
not
later
display deformed
it
is
in
sake
this
northern
shows
low
sequences
silver
and does
although the mineralization
1977).
For
complete-
is
post-Hercynian.
though
type,
in
area
be
of post-Hercynian, probably
mostly Mesozoic, age (Thadeu, 1973,
ness'
is considered to
large
a
than galena
textures
follows faults;
generally
textures; it
over
the
galena, and by
simple mineral assemblage,
a
has sphalerite
tenors,
than
sequence
briefly
re-
viewed afterwards.
The
first
exemplified
the
by
Terramonte
deposit southeast of Oporto, worked between 1966 and the
middle of
1973.
The
orebody
NE
steep
a
was
thick, and much faulted and brecciated due
At first the
movements.
1 SO
Zn
100
and
The ore
was
of
amounts
bearing
in
marcasite,
on
years
to
Zn
and
2.0 ",, Pb.
arsenopyrite.
and
jamesonite
as
and argentite (Gaspar.
sulphur isotope ratios determinedon
indicating
sulphur, Gaspar (1967) suggested
bou-
a
juvenile
a
plutonic
with
1967).
some
galena
for the
source
hydrothermal
this deposit.
for
at
of
type
to
Younger
Granite
Because
younger.
they
in
an
dating
tungsten-tin
veins of
infer
lead veins
that
the
would
150
have
related
are
Alpine
Baixa region of northern
are either
in
Ma)
reheated
the
been
thermal
followed
event
by
the
lead
mineralization with
Jurassic event to
the
history of
with
of
opening
the
continentalstretching,
this initial period
was
who concluded that
are
numerous
Portugal, emplaced
rifting
in
the Beira
The old
barite
quartz,
Silver contents were
events
too
are
during
very
the
early
and
the
be
to
C
e
i
NNE
f
Here
ENE
NE and
to
mine
e
worked
a
NE
faults and
vertical
to
steep
a
to
crush
zone in
mineralized with the development of four
90 m
was
long,
These stockworks
and small
some
No
of
N
S
have
and
been
barite,
quartz
at
ENE
(Thadeu. 1951).
of
Kelly
gas
was
Schists
et
system (
Late
al., 1978). The
Wagner
and
stockworks.
over
by
Wagner
liquid
in
arc cut
the
lenses
in
have begun
age
of
al. (1978)
Early
to
generation
of oceanic
Ma
crust
These
ago.
the fission-track
Fig.
Dolerite intruded,
Messejana
2) emplaced
by multiple
a
intrusion
event recorded
Jurassic
and
by Kelly
be correctable with later dolerite activity; also,
may
especially
along
the
Atlantic
in
might well date from this time.
100
m
of
the
More
and
coast,
of
interior
study
is
the
post-
Meseta
needed.
veins such
native silver and
H
i
e
n
one
d e
silver
1
a
silver
vein
e
n
Seville
c
enrichment, the
those of Guadalcanal
and
yielded important quantities of
sulphides.
consisted
system
i
as
leadmines in
many
to supergene
n a.
about
90
of
km
true
NE
of
silver
Madrid
ore:
at
(Fig. 2).
veins in gneiss and schist have been mined; they
contained silver sulphosalts such
and
argyrite
in
a
1907; Cávala
(Ahlburg.
as
freieslebenite. miargyrite,
gangue
y
of barite,
quartz and
Laborde. 1953).
deep.
gouge
in
Autunian phosphate
Epigenetic
western
and
sphalerite
fluid inclusions
important byproduct of
parts of lead
siderite
undeformed
galena and
an
Cazalla northeast of
The
by later faults
fault
was
stephanite
( 1977) estimated from the
the
The
et
during the late Cretaceous much igneous activity took place in
was
dolomite, calcite and
Panasqueira
containing
and
and
Beira
present (Thadeu, 1951).
WSW.
rifting.
early
started
mainly during the Early and Middle Jurassic (Schermerhorn
three
near Penamacor
slightly
pyrite,
mineralized
dolomite-calcite-ankerite
proportion
and
fractures
formed by veinlets chiefly of galena
tungsten-tin veins
trending
breccia
20 m wide
were
amounts
sphalerite.
The
None
E.
vein
lead
and
correlated with
stage, the
spreading
long dyke
Only
follow
The
timings of lead vein emplacement. However, somewhat later
end.
in north Portugal.
largest
carbonate
low.
large and exploitation has long since
was
they relate the late
started during the Early Jurassic, about 180
upper
mainly trending
mild
times.
Cretaceous
Atlantic Ocean
well
may
and
with
chalcopyrite,
gangue (Thadeu. 1951. 1977).
veins
above
times. Continental separation accompanied
Silver
The
event
second
a
late
or
in Beira Schists
everywhere present ) and varying
deposits
the
would
event
the Atlantic'.
fracturing
Spain, rarely in Portugal. Owing
an
this
or
in
while
North
small amounts
to
or
apatite in
discussed by Schermerhorn
seafloor spreading
by
it,
granite host rocks. They consist of galena and sphalerite
these
the
temperatures
C)
the 'early rifting of
latter not
come
to
150
and
of
of
cooling and
rapid
Permian
are
Jurassic thermal
a
apatite
exceeding
(not
to
post-
are
late Jurassic ( 152 Ma)
C followed by slow steady cooling
have
veins
Kelly and Wagner (1977)
Either
age.
fault
linked
not
by Thadeu (1951). From
history
Panasqueira.
(the
and
the
they
in
place
is
regional fracturation
to
age
of the thermal
fission track
Cretaceous (79
that
age. meaning
they
assigned
were
mineralization is
regional system and
a
deposited
were
C.
took
granites (Thadeu. 1951. 1973). Evidently
Portugal,
Lead-zinc veins of the second type
pyrite
they
100
deposition
ore
Hercynian lead mineralization
of
that
above
hydrothermal
epigenetic
belonging
zones
temperatures
controlled:
tectonically
Middle Triassic
freibergite and pyrargyrite
were
and sphalerite samples,
origin
%
with carbonates. The main silver-
gangue
minerals
miargyrite, polybasite
Based
m
wrench fault
to
Pb, 3.35
chalcopyrite.
such
sulphosalts
quartz
a
14
zinc concentrate) accompanied by minor
pyrite,
ore
6
g/t Ag (Portugal Ferreira, 1971).
the
bournonite and
langerite
vein,
mostly galena and sphalerite (marmatiterich in
Cd: 3 kg/t Cd in
some
%
4.16
graded
ore
Ag but these values decayed in later
t
g
3.0 %
This
veins
dolomite of these
Kelly and Wagner prefer the last interpretation and correlate
is
type
and
quartz
from hot fluids
best
recently
very
the
by
extent,
The
until
mine, active
characterized by
mineral assemblage, by high
where several
veins of small
the
central
phosphate
Spain
deposits
Portugal
(Alto
Alentejo
madura. between Cáceres
been worked since
was
and
1864 until
Aldea Moret. There
fine-grained
occur
(Estremadura) and
apatite
many
areas
Beira Baixa).
places
of
In
in
east-
Estre-
Logrosán. these deposits have
fairly recently;
occur
(often
and
in
adjacent
the largest mine
quartz veins mineralized by
called phosphorite,
lophane. essentially cryptocrystalline apatite)
in
that is.
granite,
colslate
48
limestone host rocks,
or
limestones
veins
bodies in
pipe-like
cassiterite-bearing
1955) have been mined; these
(Weibel,
the tin
and furthermore
Cacera
(near
amblygonite
the
of
stones
Morena
Belmez coalfield in the Sierra
to
clearly belong
paragenesis). Farther southeast, the Namurian
lime-
northwest
of Córdoba contain phosphorite-calcite veins and pockets (no
which
quartz)
have been exploited
during
the
second
half of
the last century.
The
a
Aldea
(Weibel.
12
I
to
As
4
km
these
width;
was
swarms.
6
clase.
Neiva
muscovite,
authors
propose
Schneider
NE-
and
known
are
or
(1951)
is
the
to
From
describe
and
vein.
to
cut
other
Hercynian
veins
such
minerals.
pegmatitie.
fact
In
the
These
of
apatite
is
that
hand. Ahlburg (1907)
other
the alteration and
refers
metalliferous
Epigenetic
by
1971).
to occur
in the
mineralizations are of economic
less
or
well-defined
deposits
are
are most
nickel
cobalt,
copper,
and
common
the
following
Hercynian
show
They frequently
to occur in
granite and they tend
to
unaffected
replacements
often
Meseta.
metalliferous provinces.
Pb,
no
more
and Cu
Zn
frequent. Co-Ni-Bi-quartz-carbonate veins
found along the borders of
pneumathe
and
the
Los Pedroches batholith
in
southern Spain (Crespo. 1972: Arribas. 1978). Veins carrying
to
directly
in
widespread
are
veins
deformation and
exogenic
arsenides
in
to
the
finding
of
the Constanza vein,
of the granite
of
occurrence
phosphate
nodules in slates associated with the limestones in the Cáceres
district.
In
his
opinion the phosphate mineralization
is
very
in
Galicia
and
elsewhere
considered
are
Hercynian granite magmatism.
Co-Ni-Cu veins and replacement
limestones
Namurian
villamaninite (Cu,
Villamanin in this
minerals
seems
to
me
that
circulation
have immobilized and
of meteoric
redeposiled apatite
when erosion and planation had
at some
down
cut
waters
in
Ni,
León,
Co.
deposits
Fe)
(S.
in
dolomitized
mined,
formerly
contain
named
Se) 2 ,
after
together with chalcopyrite. linnaeite.
area,
veins
to
the
Iberian Pyrite
later
instance
date,
the
and
nickel
discussed
smaller
under
ultramafic
Meseta.
Carboniferous
and
Spain.
slates
some
found
are
nickel
minerali-
Small ultramafic bodies,
et
al.,
Upper Palaeozoic,
contain
an
and
several
Aparis
copper
the
Early
occur
1971).
and
the
Iberian
Lower
Pyrite
as
Palaeozoic
(Cambrian and Silurian) spilites in the southwestern
of the
Meseta
Carboniferous spilites and
Belt
(Strauss
et
some
pyrite
accom-
of quartz and carbonate. In
veins have been exploited, for
occurrence,
a
system of
slates.
veins
The fissures
and
following
were filled
calcite). quartz
rich
in
arsenic
and
minor
in
Copper
central
veins
and
containing
arsenopyrite.
other
minerals
uranium minerals
southern Spain
1907:
(Ahlburg,
1978).
These veins
remains
be
in
by galena and
or
marcasite, sphalerite, galena and
1968).
known
Arribas,
Late
postdate
so
are
the
main
folding and regional
post-Westphalian.
but
then
meta-
exact
age
unknown.
al.,
1977).
Hercynian ferromanganese
Southwest of the Pyrite
large
serpentinized,
among
are
may
or
Their
pages.
chlorite. The mineralization consists of chalcopyrite
pyrrhotite,
(Gaspar.
Portugal
alignment of
diabases: the
1976).
mostly
differentiation products
diabases
the
morphism.
disseminated chromite. magnetite
and pentlandite (Crousilles
(Caspar.
as
and
rocks.
serpentinite bodies associated with spilites
serpentinites contain
and
chro-
west, southwest
of these
some
North of Córdoba in southern
Lower
the
Unimportant chromium
associated with
Palaeozoic
Early
in
Galicia
in
occurrences
differentiatesof mafic rocks locally
possibly
chalcopyrite
consists
gangue
Portugal
some
with
mafic-ultramafie complexes
Trás-os-Montes.
are
previous
on
by carbonates (mainly dolomite, ankerite
Late Palaeozoic chromium
mium, much
discussed
simple:
is
south
in the Los Pedroches batholith
shear faults in greywackes and
and
Apart from
as
Belt,
mineral assemblage
in
widespread especially
panied by pyrite, by tennantite/tetrahedrite
south
the level of the
al.. 1968; Arribas. 1978).
et
are
and southwest Spam,
could well
primary veins.
zations
(Ypma
Copper
sphalerite; the
young.
local
these
post-Hercynian epigenetic
to
Co-Ni
tin-tungsten
to the
impregnation by apatite
rocks of the veins, and
south
known
(NE
pyrite, bravoite. niccolite and other sulphides and secondary
the
phosphorite-encrusted bone breccias
It
Late
related
a
a
re-
veins.
wall
into
Portugal
Galicia (Armengot de Pedro & Campos
of
None
magmas.
formation of
favour
in
ortho-
perthitic
Hercynian granite
veins.
the
area in
obvious relationship
distinguished
apatite-quartz
east-central
furthermore
are
peri-
gabbro intrusive
the frontier with Spain (Gonçalves.
near
Nickeliferous veins
related
paragenesis.
the
in
occurs
derive from
to
Pyroxenile.
1976).
with
dimite associated
Cabo Ortegal
al..
significance.
younger age.
mineral in the Younger Granite pegmatites and
to
Alentejo)
considered
arc
et
Beira Schists
pegmatitic-hydrothermal origin from
granite-related origin
On
and
faults
and hydrothermal phases during
tolytic
Portuguese
dotitc
of the quartz-apatite veins
al. ( 1952)
et
sidual fluids derived from
Also.
ultramafics (Batista
leached
this
copper
bismuth
Spain
many
arsenopyrite
a
in
swarm
be of Autunian
must
their
of
C'otelo
and
Portugal
little doubt that
because
Portugal,
Logrosán
a
km long.
hydrothermal origin
granites
Near
of the veins, the Constanza
one
over
veins in
can be
and nickel mineralizations that
In
serpentinites.
occur
folded Upper Devonian limestones show minor
Julia. 1971).
thick,
m
of
are
limestone
Beja eruptive complex in south
mainly of gabbros and diorites with volcanic
rocks; associated with these rocks
area
The vein.
1955).
Younger Granites, they
There
m.
Devonian
cut
SW quartz-apatite (phosphorite) vein
0.60-7
180
depth of
a
thick,
m
Elsewhere the veins formed
reached
worked
Moret mine southwest of Cáceres
and
long
m
of the
part
consists
Cambrian carbonates
large quartz-apatite vein down
800
southern
The
Portugal
structure,
the
Belt
in south
proper
Cereal anticlinorium
lies
Portugal
(Fig.
5),
in
a
Lower
Carboniferous volcanics and sediments much like the Volcanic-Siliceous
Complex of
the Iberian
Pyrite Belt. Here
large number of ferromanganese veins, of
being worked. These veins reach 18
and they follow NE
SW fractures
m
which
thick by
dipping
up to
40
occur
two are
70
5 km
a
still
long
SE. They
49
consist of quartz with iron-manganese oxides
and
from
superficial oxidation
The
grade is 8"„
average
barite and
carry
which
mostly)
pyrolusite
primary
Mn
and
the veins
well.
as
In
Mn. 40.5",, Fe) and 5901
(7.7%
U
is ascribed
magmatic activity
(Carvalho
al..
et
late
to
1971b: Car-
0
3
8
OECD
OECD,
Paris).
Portugal
uranium
reserves.
In
the
Asturian
Pola
coalfield
formerly
de
Lena,
several
mined,
of
south
small
mercury-
found
are
Oviedo.
as-
sociated with realgar, orpiment, arsenopyrite (in considerable
arsenic
amounts:
other
and
Westphalian
coal
and carbonate
sulphides
fractures
seams.
These
and
joints
quartz
or
along
occur
gangue
in
impregnations
as
al..
0.2
grades averaged
of which
occurrences,
et
also
this field), various
mostly
sandstones, conglomerates, limestones and
Ore
mineralization, form
(Anger
in
formerly produced
was
U
Hg and 0.5
„
the most
NNE
a
Their
1968).
important
alignment
age
and
is
As.
16 km
long
uncertain.
t
201
in
0
U
Autunian (?) epigenetic fluorite and barite
8
132
rich
in
fluorite
fluorite mine
El
Spain exploits
two
found
Chaparral
and 060
granite and the surrounding
sphalerite
with
with
the
other
southern
Cerro
near
gneiss
pyrite, galena and
in
some
m
rock.
The
south
run
They
in
are
sulphides, mainly
little chalcopyrite: barite is
a
lacking.
in
most
abundant
central
in
the
southern
mines
small
Meseta
but
likewise
are
also
occur
in
and northwest Spain.
These veins
Hercynian
hence
their
deformed
cut
is
age
late
strata
and
Hercynian
category
plus
Uranium
are
Portugal
In
in
deposits
in
numerous
and
west
1907 the
eastern
and south
rocks
Meseta
of the Iberian
of
parts
north and
world
in northern Portugal
was
uranium
when
extraction
Systematic prospecting
took
the discovery of nearly
about
sive
one
promising
has
uranium
t
to
U reasonably assured
U)
state
minable
at
at
up
up
to
1955
organization, leading
resulted
in
In
the
Spain
exten-
discovery
of
to
U
uranium ore reserves
0
3
)
8
reserves
$80/kg
$80/kg
were
(at
U
assessed
a
at
recoverable
91501
cutoff grade of
($30/lb
U 0
3
8
U by in situ leaching
),
of
U
at
The
at
another
850
ppm
t
U
worked-
is
207
state
a
mines
6800
t
8500
the
in
08
1976
and
3
Empresa
company.
1977
produced
has
Rodrigo (which
belonging
t
ore reserves
the
in
U
U
Spanish
the
to
de
Junta
-
at up to
cost
$80/kg
U
reasonably assured
estimated
U; for the
t
additional
re-
$80-l-30/kg
range
U
Resources, Production and
Nuclear
Energy Agency
has
Like Portugal. Spain
of
0.4%
the
Meseta
are
Younger Granites. The intragranite
and the
contact
generally
a
the
around
deposits
aureoles,
are
granites,
veins and
dissemi-
clear tectonic control in that the
As
the
for
an
Pb-Zn
'Alpine'
be Alpine
to
too.
The
main
the
fracturation
mineralization
that is. Tertiary.
from
It now seems
northern
have
con-
likely
age.
and
Spain into southern Spain
batholith
been
central
(where
been worked)
up
impor-
Portugal
deposits
to
the
over
in
the
Guadal-
fault.
quivir
The
U
r g e
deposit is
this
i
r
i
now
method
grading
mine in north Portugal exploited
ç a
0.5
discovered
"„ U,0 8
were
the
to
winter
ENE wrench
fault
leaching (the applicability
when 5000
stockpiled
70%
in
the
along this
gangue
with
Portugal Ferreira,
The
Ni
sa
7.5 km
long
with
zone
of
ore
during four
of the contained uranium
a
over
some
pyrite
or
a
an
thick.
crush zone 1 -10 m
and consists mainly of
distance of
pitchblende
in
marcasite (Cameron, 1960:
1971).
prospect, discovered in
survey, is by far the largest
consists of
tonnes
open
rains). Mineralization is controlled by
Workable uranium mineralizationextends
m
uran-
extraction has ceased and
ore
worked solely by
was
when it had lost about
years,
meter
has
was
of uranium deposits of economic
zone
stretches
this
veins
and
age
that it is largely of Mesozoic
It
Junta
in
being stockpiled.
U
t
uranium deposits of the
near
veins,
are
assigned
1300
mines
and disseminations follow shears, faults and shatter
zones.
due
several
total output of 87.61 U in
1977. OECD
of the
or
nations. There is
the
the
the hands of
Ciudad
given (Uranium
within
mostly
of
a
was
near
from
stems
majority
deposits
(6800
425
and
(Matos Dias,
reserves.
jasper
deposits.
S 130/kg U ($50/lb
recoverable
1976).
four hundred deposits of which
likewise
In 1977 the Portuguese
up
a
hundred offer economic potential.
prospecting
Dias,
(Matos
for uranium in Portugal began in
by the Junta de Energia Nuclear,
to
over
total
deposits;
reserves
entities exploit uranium mines
iferous jasper veins in granite;
discovered and it was worked for radium from 1913 until 1944
of the
10,000 t). The remainder of
) stood
situated within
central
Spain.
Urgeiriça deposit
8
were
Pedroches
Hercynian
the
mine
of
IAEA, OECD, Paris).
tance
uranium
112
production
state
totalling 15,300
figures
western
Remobilized Autunian
its
Demand, December
or
possibly post-Hercynian.
0
3
and
the
the Spanish uranium
1977
($30/lb U
sidered
undeformed and
are
granites,
embrace
IAEA,
world's
Nuclear.
Energía
In
with
areas,
production
excess
uranium output
veins
Barite veins formerly worked in
the
Uranio S.A. (Enusa) which in
U 3 0 8 from
t
reserves
thick and
The veins
country
much fluorite and
sulphides
Meseta.
Muriano
respectively.
,
quartz veins
in
long steep veins reaching 30
110 -120
trending
are
is in
operates
The main producer is
Spain.
no
Quartz veins carrying sphalerite, galena and
Demand,
of
0.4%
U reserves
which
1977. Two
in
3
Nacional del
is the M ieres
some
origin
even
1.2",,
holds
27.7",, of the
or
in 1977;
t
uranium
Spanish
sources,
and
Nuclear
1976 and 66.3
between
Cinnabar
thus
Portugal uranium extraction
Energía
Urgeiriça and Guarda
occurrences,
Mieres and
U
t
($50/lb
1976).
In
Central
Production and
deposits contribute 80",,
1884
Nisa, has
one,
U
SI 30/kg
to
grading less than 425
Nuclear Energy Agency and
The 68001
15
at up
ores
Resources.
(Uranium
December 1977.
de
Autunian (?) mercury
exploitable
) by leaching of low-grade
U)
ppm
1976a. b).
arsenic
U
mines, and 15001
out
however, only
epigenetic paragcnesis
This hydrothermal
valho.
siderite.
manganiferous
Fe. In addition
43",,
by
produced.
were
Hercynian
derive
to
places base-metal sulphides
in
1977, 30,2501 ferromanganese
barite
(lepidocrocite
thought
are
irregular
1957
uranium
during a
scintillo-
deposit in Portugal.
disseminations along crush
zones
contact-metamorphosed Beira Schist wall rock of the
in the
coarse
50
porphyritic Nisa granite,
several
crush
other
Younger Granite, which contains
a
extend
zones
to
and
pitchblende
rare
of
depth
a
predominates, accompanied by
and
U
uranium deposits. The uraniumorebodies in the
25
black
Autunite
metres.
uranium
other
thods) of
type
same
the
are
orebodies in
the
Ciudad
concentration
in
Spain. The principal
blende, accompanied by
pyrite
some
and
a
its
mineral is pitch-
ore
alteration
products (gummite.
of quartz, jasper,
consisting
gangue
barite, calcite and fluorite (Arribas.
chalcedony,
Fernández Polo,
The
1960, 1975;
of
of
deposition
these
uranium
deposits has been diversely interpreted. Originally regarded as
Hercynian endogenic hydrothermal mineralizations it
realized that
Matos
Dias and
Soares de
uranium
Portuguese
factors
exogenic
ore
deposits;
consisted of
make
posits
the
Dias,
vein
minerals
rock.
NE
trends.
impregnate
Wall rock
limonitization)
In
veins
deposit
lacustrine
embrace
and smoky
with the
weathered mafic
gangue,
dykes;
or
hematization and
Energía Nuclear,
This classification
to
The
as
applicable
the
have
may
suffered desilicification too (Junta de
deposits
they
metasedimentary wall
characteristic. Hematized granite
seems
with
veins
quartz
dissemination deposits uranium
altered granite
1968).
Spanish Meseta
well.
pitchblende,
are
thus
is
source
deposits
black
oxides,
finite, gummite and diverse coloured silicates such
Soares de Andrade,
None
depth,
of the known
not even
U
appear
are
cof-
uran-
as
mineralizations
pitchblende
the
uranium
(max. 50
old planation
they
are
surfaces
controlled
tectonized
Matos
Various
any
display
a
with Younger
relationship
iferous
Soares
de
Andrade (1970) present
uranium
was
on
Mesozoic
solutions
leached
by
these
deposited uranium minerals in
to
content
open
(stated
are
Afterwards
preconcentrations
rich
to
in
uran-
infiltrated
the bedrock and
have been
concentration of
the skarn
1.
Morena
the
leaching
of
the
deposition
of
the
in Mesozoic times, their
Younger
Granites; hence these
Autunian
outlined
uranium.
provinces
in
elements
ore
the
a
d
n
foregoing; especially
(Fig. 2):
are
these
2.
iron province of the
deposits
the
in
Zone,
epigenetic.
be
may
these
-
magnetite
syngenetic.
Ordovician
belt
in
the
Cambrian carbonates
metasomatic
as
Lower
Lower
Ossastated,
as
reaction skarns, and/or
as
skarns.
marine-sedimentary
vince in the northwest Meseta,
fringing
an
ironstone
pro-
emergent landmass
syngenctic deposits.
are
3.
the
in
south Spain
Lower Silurian
volcanogenic
or
mercury
province
syngenetic
a
have
may
a
deposit
of the Almadén
that
sedimentary
be
may
source
area
wholly
with
de-
position activated by volcanic heat.
the
the
Lower
Carboniferous polymetallic pyritite province of
Iberian Pyrite
Belt
in
the
Meseta -
southwest
syngenetic
massive sulphides.
volcanogenic
the Lower Permian tin-tungsten province
of the
northwest
mostly epigenetic granite-bound de-
posits.
Permian
the
south
-
Spain
In
of
a
terms
varying
the eastern
lead province of
Sierra Morena
in
epigenetic lead-zinc veins.
quarter of the
average about 47
ppm
of tectonic
settings
of
environment
mineralization.
The
we
iron
find
much
of
ore
magnetite belt, if syngenetic, would have been deposited
Lower
Cambrian carbonate shelf,
in
the
covering
clastic
the
infilling
Meseta.
mulated in shallow
a
Silurian platform
Pyrite Belt
central
sional
block,
in
the
movements
The lead-zinc
veins
along
an
major
a
Cambrian
coastline
mercury
early
volcanism.
second
was
major
geosyncline
ores
accu-
the end of
deposited
orefield developed
the
during
at
a
the
on a
a
on
episode of mafic volcanism. The
southwestern
felsic and mafic
associated with the
developed during
the
Almadén
during
the only
is
of
The Lower Ordovician iron
water
transgression phase. The
intense
spaces.
calculations, removal
uranium
the
circulat-
1960) and accumulated in
planation surfaces.
from
to
long phase of
a
significant and productive because of exceptionally strong
lull
joints, fractures, breccias and mafic dykes
original
to
in central and northern Portugal and
model:
down
cut
generally).
m
meteoric waters from the Younger Granites which
soil
great
by shears, faults and fractures marked by
Días and
while
etallogenetic
m
epochs
6.
extends to
association
also
in radioactive elements (Cameron,
the
and
zones.
following genetical
ing
deposits
amounts
infrequent.
Apart from their close spatial
Granites
in minor
in
be sought
to
that
largely place
consist of remobilized
and central Meseta
other sulphides
two
Ferreira.
Portugal
erosion
favourable for prolonged
were
likely
appears
5.
frequent,
in
planation occurred during the Cretaceous.
sulphates (uranopilite and zippeite). Pyrite and/or marcasite
calcite and other carbonates
1970;
times strong
Hercynian granites, and during
ophane, phosphates (autunite, torbernite. sabugalite etc.) and
are
me-
resulted
pitchblendes
SYNTHESIS
4.
uranium minerals
208
/'Pb
and dissemi-
associated
are
alteration (sericitization,
is
the
disconcordant de-
are
deposits
with milky
quartz-limonite breccias and
show mainly
in
207
and
Ferreira.
Portugal
1960). Radiometric
and Pb
20 Ma, 83 ±8 Maand 190±10Ma, and
uranium orebodies took
evenly distributed between
reserves
1976) and
The
gangue, veins
they
classify
concordant
phosphate impregnations
Portuguese
Granites.
Younger
to
known
235
role.
a
concordant
as
Urgeiriça region. The
the remainder:
Matos
two
jasper
the
up
nations (with
according
far the only
so
uranium
in
sandstones
Andrade (1970)
occurrences
disconcordant (discordant
have played
must
Portuguese
post-Hercynian
erosion and
was
/U
redistribution of uranium. Another major episode
Il
mode
207
Pb
,
planation conditions
and
238
Upper Cretaceous and Triassic planation periods
the
expose
7U
biotite would
for the uranium
deposits
to account
alteration (Cameron,
20<
of
and the breakdown
and Fe
80 +
ages:
the
In
1971).
1970).
and
origin
1971)
this fits
Pb
(Matos Dias &
Spain, which represent the largest economic uranium
western
U
some
of
groups
Of the
sericitization
dating (using
oxides (Portugal Ferreira.
Rodrigo region (Mina Fé, Mina Esperanza and others) in
soon
O s ) by
and the wall rock
phosphates
1971).
etc.),
3
release enough
outside
geosyncline, when
Carboniferous
The
tin-tungsten
the
ten-
set
off
ores
are
episode of major granite intrusion.
followed
late- to
post-orogenic shear faults.
51
There is
obvious
no
distribution of
immense
these
variety of
explained by
collision,
metallogenetic zonation, and
major
minor
deposits,
Local
etc.
history
of the
Meseta
and crustal
ments
and
ranging from
their
mafic
tension. The
Meseta
of the
clines
foredeeps flanking
with
the
well-developed
the
move-
in
symmetrical
outer
two
geosyn-
large rising central block, in
a
central block)
produce
in
the
abundance of
pattern consistent
a
intraplate environment where orogenic evolution is
an
controlled by
their
that find
vertical tectonics and
in
origin
framework
is
with the
of
the
great magmatic activity
underling
mantle.
The broad
Hercynian mineralization
within-plate,
not
uplift of the central block eventually gave rise
result,
folds spilling
to the
is
vergence
Though
Most
mainly of the
was
of the
through
the Hercynian
cycle is indicated by strong volcanicity in almost
trom
the
granitic
Late
Precambrian
magmas,
and
by
on.
periods
intrusion of
repeated
by tectono-sedimentary
all
differentiation
of
The
of
ascent
hot
I
in
the
below the Hercynian
orogen
Mantle upwellings
terms.
following
affected the
volcanic and plutonic
came to
the
pierce
plexes of
the
through
rose
Some mantle diapirs
the mafic-ultramafic com-
forming
crust,
the northwest
magmas.
by producing
crust
uplifts and by generating fractionates that
as
of the Meseta (van Calsteren,
corner
1977).
resulting
in
the
of
period
and
uplift
related
tectonism
towards the end of the Cambrian. Over
Cambrian
folded. It
became
seems
mantle activity:
from this time,
and
its
Early
variably eroded;
likely
that
this
the ultramafic
as
does the
emergence
the
over
locally
later.
to
anatexis,
and
crustal
and
of this
origin
the
to
ascent
they
were
corner
of the Meseta
in
vast
offsets
and
occur
stresses
set
the
in the
movements
opened
new
granite
a
deposited,
a
facies
the
emerged
fractionated
facies dominant elsewhere
in
contrasting
the
As
magmas
zone
with the
platform
Peninsula.
crust
This completes
Meseta. Now
in
sources
marginal
a
central block with rising tendencies and
basins.
coincides with
at ca.
felsic
The emergence of the central
the emplacement of
350 Ma and
volcanism
Iberian
the Tournaisian
eruption of the extensive Pyrite
during the
Visean. The central block
granite intrusion. This
the
was
appears
magma underneath this block,
Tournaisian and
the site of'
to
earliest
the
let
of the
crustal
slab
Meseta,
fractured. No
from
arose
in
mantle. Thus
and
strata
uneven
slight
to
response
large
channelways
were
a
precipitated,
some
of them of granitic
by near-surface recycling.
produced
broad outline of framework and evolution
during the Hercynian cycle
us
look
some
at
in
deposits and
the Iberian
their
possible
detail.
more
First the part
metamorphism
The
as
geosynclines of the Cantabrian and South Portuguese
Zones
1
o
c
a
Meseta,
is
in metallic sulphide,
s m
in the
the
massive
sulphides
that
occur
northwest and south-
not
obviously related
base-metal sulphides
to
of the
For the Pb-Zn mineralizations of the northwest
as
Rubiales, Guillou (1971a) infers
the metals,
on
an
adjacent
an
exogenic
weathered continent. The
explanation may also hold for the lead-zinc belt in south
the southwest
ore
tary.
i
obscure since they are
Portugal, though
The
n
of the Cambrian lead-zinc
origin
voleanism, unlike
P)
v
and oxide mineralization.
disseminations in carbonates
west
may
and
it
may
Meseta
be noted that voleanism took place in
the deposition of the carbonates.
during
of the magnetite belt,
well
its
amounts
if
Cambrian and synsedimen-
be volcanogenic. as its composition (high S,
association
does
not
with
favour
a
copper
sulphides
in
low
economic
purely sedimentary origin.
The other stratiform base-metal
sulphide mineralizations
of
adjacent secondary
played by
sulphide-oxide
and
indicate the slow rise
while
faulted and
underlying
of mineralization
same
the beginning of" the Carboniferous the Meseta became
differentiated into
the
radioactive minerals and by
faults probably
rigid
vein minerals
epigenetic
source of
was
magma
rock:
country
post-granitic hydrothermal solutions from which
to
flysch
subsided.
in
consolidated
was
the
in
up
Meseta, such
granites
a
their
distinguished from the Older
are
content
massifs,
granitic
pyritite type.
Belt
higher
much
sufficient concentration.
and
granites
afterwards
Shortly
4). Thus the
mantle convection.
of
Older
somewhat
their mineralization.
subsided
block
The
levels
from heightened
of the northwest date
continued in the northwest, the surrounding
two
metamorphism,
Granites associated with
elements
ore
earlier
a
a
that the crustal level where they
means
Younger Granites which
Granites by
At
magmas.
riseofgeotherms
derive from migmatization and
none
the Older
are
intruded the
crust
important mineral deposits of metamorphic
no
nor
lower
migmatization and anatexis.
to
known
are
strongly, and the Upper Ordovician, Silurian and Devonian
At
the
crust,
upper
mantle domes originated regional
passing
Almost
origin
the
middle crustal levels,
to
Granite magmas gained the higher
place
Meseta the
equivalents)
locally
deposits laid down around
their
owe
mantle diapirism
uplift
and
resulted
diapirs
took
of the
the Ordovician (Fig.
during
Ordovician iron
ultimately
area
(including Beira Schists
strata
and
emerged
most
and
wrench-faulting
of the Older Granite
generation
higher level, in the middle
derivation, the others
One
Westphalian.
composed of folded and variably metamorphosed
interpret this
crust
took place
folding
mantle material into
caused extensive remelting of lower
into a mosaic of subsiding, stable and rising palaeogeographical units.
a
to
occurred afterwards, later
nature
Twenty million years later, however,
below the Meseta all
and
block-faulting.
originated lacked
Mantle activity
folding,
Meseta
during the
phase,
folding and refolding
some
mineralization. This
plate-margin.
north in the northern
the southwest in the southwest.
tectonism
to
into the marginal troughs. As
over
during the main orogenic
tectono-sedimentary facies
folds and thrusts and
verging
in
granites
(as
The
the
subduction,
characterize
control plus the
expressed
structure
outwards
as
felsic.
the
block-faulting,
and indicate differential vertical
palaeogeographical
or
well
as
to
alone
adequately
involving
strong subsidence,
geanticlinal uplift and emergence,
volcanism
be
cannot
plate-margin tectonics
arcs
let
provinces,
ore
the
in
Late
Galicia,
Precambrian
the
Silurian
(or
Silurian)
deposits
in
the
copper
sulphides
northwestern and
southern Meseta and the Lower Carboniferous Iberian Pyrite
Belt
were
deposited during important volcanic episodes and
52
submarine
are
The
ores.
the
seafloor and
marine
(and
exhalativc-sedimentary
volcanism
resedimented)
attended by hydrothermal activity
was
sulphides
sub-
precipitated around
were
on
The Late Precambrian deposits in Galicia and the Silurian
much
the
with
associated
are
volcanism
in
taking place
mafic
these
the
canism. and
an
related
are
Even
though
smaller part of the sulphur in these sulphides
from seawater
the
sulphate,
I
origin.
contemporaneous
metals
must
felsic and mafic
mineralization
occurs
episodes during
a
are
during only
one
were
all that
redistribute metals contained in
volcanics
raneous
would be
centrated
must
in
concentrated
have
a
or
at
On
a
between
so
only
is
scale,
most
to
is
needed
seawater.
the
basement rocks,
level in
a
few
few of
a
mobilize
to
in contempo-
resulting
highly
not
ore
con-
Hence
particular place.
one
and have become
deep-seated origin
particular
one
entirely
between
smaller
a
through the volcanics.
particular
at one
the metals
in
or
dispersed
or
The other rocks in the volcanic piles
barren. If volcanic heat
and
On
epoch.
any one
volcanic period and is linked
volcanics.
erupting
derived
volcanics.
nearly
or
or
but their metalliferous potential
magmas
different in
be
may
contrast
and barren
ore-bringing
felsic
to
phase, by differen-
magma
tiation.
their
with
of
role
p
Cabo Ortegal
u
suites:
constitutes
only
to
the
but
Granites
they
metasomatic introduction of
in
that
still
be
the
Brag-
or
more
(the
Hercynian
magnetite
deposits
ore
skarns
are
minerali-
endogenic
not
generated by
elements from the
ore
are
belt
granitic
age
of this possible granite-bound
age
of
the
granites, and this
age
is
unknown).
The
can
the
area
metallization would
most
if the iron
case:
the
be
divided
elements
into
the
endogenic
following
groups: Sn-W and related
zation derives from these granites.
and the associated
First,
and
the
the
their
and
their
recycled middle
on
ores.
crust,
source
If
are
material
they
the
was
not
a
volatiles (especially F and CI
Younger
the
or.
Younger Granite
undersaturated. it
Granites
can
Younger
regards
as
This
Granites
ultimately,
one.
as
may
The
that
provides
of the
region
Older
to act
as-
indicates
magma
dry
hardly
of this
im-
Younger
represent
derive
must
from the mantle.
have
ore
been
water-
elements
tin carrier ions)
and
in the
be explained by assimilation
rocks
the
so
supports
mafic
an
Younger Granites
mafic
the
as can
The
it
or
in ore
heat
700
600
a
assimilated
this
view,
crustal
the
Next,
blisters
magma
on
may
leading
It
in the
be
deep
source
that
appears
as
group.
regional
to
vast
the
such
mantle
ascending into the
Granite
seen
scale of
vast
on a
magma,
mantle
of
from
the width of
a
Older
to
more
unlikely
of the Sn-W
magma,
then
be
from
materials such
introducing heat caused melting
are
and
magma
contamination.
over
mantle
suite,
mafic
including grei-
the
considered
requires
above it. thus generating the
large
magmas.
later
as
con-
slowly growing
The
crust.
Younger
derivation,
including
material.
of the
source
puted. Notably the main
the
is
transfer
km
from
range
have constituted the
elements
derived mafic
Younger Granites
upper
so?
by partial melting
may
taminated fractionates of the mafic
into
we
diverse
very
crustal
granite intrusion
only be provided by the
and
the
through which
crystallization
significant
poor
enormous
orogen
crust
a
intermediate crustal
too
material, possibly
crust
fractional
latter possibility
or
metamorphism and
Meseta
also
(which
if the Older
do
alkaline granites,
mantle
upper
The
crust.
Besides,
are
have been derived
may
basalts would be
the
and
origin by
ultramafic
lower
levels
Granites
than the Older Granites, and
material without
because
and
-
basement
indicates strong differentiationin
This material
the
crustal
overlying
to calcalkaline
This
sens.
crust
their
these elements from their parent
not extract
from the
more
rocks
and
how could the Younger
Second,
much
levels, since the Older Granites
middle
these constituents. Besides,
in
poor
or
rose,
accompanying
source
metals
has
metals, which has
been dis-
of the tin and tungsten and of
been
sought
in
sedimentary
preconcentration in géosynclinal sediments, with the intrud-
ing granite
ing the
magmas extracting, concentrating and redeposit-
metals.
Thus Ypma (1966) suggested
metals would have been present
the
crust,
matter
is
the
entering
more
in
ascending
in
the
for
Meseta:
tin
it
tin
phic marly
their
beds
extent;
are
since
seems
sedimentary
skarn-type pockets.
mechanical sediment of placer type,
else it
the
metamor-
regional metamorphism
or
tungsten remains problematical:
or
that
likely
syngenetic stratiform deposits, because of
later contact
local concentration into
this
and other
formations in
For tungsten the
magmas.
complicated than
known
that
sedimentary
tungsten disseminations in Cambrian and Silurian
deposits,
the
then the Younger Granites
from still deeper crustal levels
Though
source
elements?
different.
the
minerali-
this metallization
is
between
Granites
are
constraints
U
and the
Why
mineralization
sources
Granites
ore
contrast
Older
sociated
portant
too.
the Younger Granites and what is the
to
magma
mineralization
(Nb, Ta, Mo. Be. Li): Au-Ag: Sb-Au. Part of the Pb-
Zn-Ag mineralization belongs here
linked
crust
tungsten is
Younger-Granite-bound
rcmelted
detritus in the geosyncline). that is, the
Granites could
mafic-ultramafic complexes
of the four
one
epigenetic,
Leaving aside
m.
s
other
Younger
doubtful
a
syngeneic
magmas
i
t o n
minor chrome deposits,
zation is linked
granite
1
and
crustal
upper
of'
its
from
Granites,
Next the
anca.
and
consist
Hercynian géosynclinal
vol-
greater
a
be largely
deduce this from the
larger scale there is contemporaneity
the
felsic
to
evolution from mafic
ore-element carriers.
as
completely
felsic
contemporaneous mafic volcanism is practi-
cally barren. There is thus
of juvenile
the
epochs is barren. However, the
manganese) of the Pyrite Belt
magmas
and
volcanics.
important Lower Carboniferous sulphides (and
more
which
know
vents.
sulphides
from middle
may
have
The
the scheelite
eroded
formed as
an
from
induced
source
may
of
be
a
pre-existing
exhalative product,
trapped in marly sediments.
Cambrian and Silurian syngeneic tungsten has been
posed
as
a
preconcentrated
deposits associated
through
strata
anatexis
to
yield
a
with
the
source
for
mineralized
latter
say,
with
are.
When the
granites have
been
magma
(Noronha,
tin
not
Younger
or
or
Silurian
1976).
associated with
Granites
tin
breaking
and tungsten associated with
deposited
in
the ore-bearing Younger Granite has
Cambrian
pro-
epigenetic
Hercynian granites, for instance
However, Older Granites are mostly
through them
later
of tungsten-bearing Cambrian
and tungsten mineralization but
the
the
Silurian sediments
granite
not
-
been
then
that is
to
in contact
these
metals
53
must
[f
derive from
certainly
the
Younger Granites
derived
than
even
the middle
could
the
of
do
to
exception
metals too
related elements
On
note
the
sum
the
-
crust
deposits
elements
ore
up,
ing, leaching
other
or
this was
have
been derived
exogenic
Ag
and
eral
of Ordovician
the
in
age
large ironstone
northwest
possibly of the Cambrian lead-zinc
Meseta and
volcanic
2) by
ores:
Plutonic heat from pre-existing rocks in the
crust
upper
this is the
or
this
-
lineaments
likely that
very
Almadén
from
lower
base-
for the
case
in the
Meseta
-
setting
weakness
by
province.
instrumental in
that acted
have been exerted -
may
crustal
deep
control
to
is
of the
considered that
associated with mafic
Belt
and
the
of Almadén is
the
related
are
is clear that felsic
role than mafic
important
more
the mercury
province
it
volcanism and plutonism.
the
deposits.
major, economically important
volcanism, while metals of
tin-tungsten
ore
in
pronounced
of the late Hercynian and post-Hercynian vein
[fit
this
and
magmas
became
in
structural
of
zones
channelways
as
structural
deposits of the Peninsula only
a
Sn-W
were
mineralization. Overall structural control of min-
deposits
intraplate
1) by weather-
the
probably the origin of
seems
solutions. Local
from the surface of
processes
the
magmas
mineralization of the
granite-bound
It
case
To
mantle levels -
upper
localizing
Cam-
direct from the
up
plutonic
or
Carboniferous age, for the volcanogenic iron deposits, and for
conclude this section.
we
or
for
possible origin
a
as
volcanic
by
the
have
must
that represents
brought
have been
may
this heretical
proposed
3)
metal sulphide deposits of Late Precambrian. Silurian and
stratabound scheelite deposits.
syngenetic
crustal
made for that
must be
been
elements
of the Sn, W, Nb, Ta, Mo. Be, Li. U, Au,
most
mantle.
an
these
then
so,
minderalization
tungsten
brian and Silurian
Still,
ore
have been collected from crustal rocks, because
not
mantle source. Evidently
part
Sn and associated
has
mercury;
from fractionated mantle-
stem
and if the
magma,
Older Granites failed
a
deeper levels
where the Older Granites originated by anatexis.
crust
Pyrite
felsic
to
magmas
played
magmas.
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