Download The geology of the Bidjovagge mining field, western Finnmark, Norway

The geology of the Bidjovagge mining field, western
Finnmark, Norway
NILS B. HOLLANDER
Hollander, N. B.: The geology of the Bidjovagge mining field, western Finnmark, Norway. Norsk
Vol. 59, pp. 327-336. Oslo 1979. ISSN 0029-196X.
Geologisk Tidsskrift,
The Cu-mineralizations in Bidjovagge occur in the Caskias-Stuorajaure group which consists of green-,
hornblende-, and graphitic schists, greenstones, and plagioclase-carbonate rocks. Amphibolites and
diabases of presumably intrusive origin are common. The mineralizations are localized to feis and
carbonaceous schist in the limbs of an anticline striking N-S and dipping 15-30" north. The ore minerals
are chalcopyrite, pyrite, and pyrrhotite occurring as impregnation and in veins, occasionally with galena,
sphalerite, and magnetite. The best ore is C, consisting of three ore bodies with total reserves of
approximately 2.3 million ton ores with 1.5% Cu.
N. B. Ho/lander, Saga Petroleum a.s.
Bidjovagge copper mines are situated on the
Caskias mountain 69"17' N, 22°29' E, 700 ma. s. l.
(Fig. l) in Finnmark, north Norway.
The mineralizations occur in what is known
as the Caskias-Stuorajaure Group, which in­
cludes greenschists, homblendeschists, graphitic­
schists, greenstones, and plagioclase-carbonate
rocks. Amphibolites and diabases, which pre­
sumably represent rocks of intrusive character,
are common (Holmsen et. al. 1957, Mathiesen
195 7, 1959, 1967).
What is known of the discovery of the
mineralization dates back to the late 1940's or
early 1950's when two Lapps found sulphides on
the Caskias mountain. Some rumours, however,
indicate that it was known as early as in the
1920's. Whatever the truth, the claims were
staked in 1952. Boliden Mining Company, Swe­
den, started their field work the same year. The
application for a concession was, however, re­
jected.
In 1955 the Norwegian government made an
agreement with the owners of the claims, bought
the geological and geophysical reports from
Boliden, and started investigations. In 1954-195 6
Norges geologiske undersØkelse (NGU) made a
regional geological mapping. From 195 6 geologi­
ca! mapping, geophysical measurements, geo­
chemical sampling, and diamond drilling were
carried out by Kautokeino Kobberfelter Statens
UndersØkelser (KKSU), which was specially
formed for prospecting this area. The C­
mineralization was investigated in 1960-1962 by
mining and diamond drilling at 600 m a. s. l. In
&
co. , P.
O.
Box 550, N-1301 Sandvika, Norway.
1963 KKSU was taken over by NGU, which
continued the investigations in the next three
years resulting in the following estimates of the
tonnage of the mineralizations (i. e. Ingvaldsen,
Paulsen & Mathiessen 1966):
A:
B:
C:
D:
Total:
Proven
reserves
(ton)
% Cu
Probable
reserves
(ton)
302,000
253,000
2,065,000
360,000
2, 980,000
2. 10
1. 8 3
1. 8 4
1. 8 4
1. 80
100,000
5 0,000
250,000
200,000
600,000
In addition 1/2 ppm Au was indicated.
In 1967 A/S Bidjovagge Mining Company was
formed by AlS Bleikvassli Mining Company.
The plant was completed in 1970. Production
started the same year. In 1974 A/S Sydvaranger
bought A/S Bleikvassli Mining Company and
thereby also Bidjovagge. A systematic eva1ua­
tion of the mine and prospecting in the surround­
ings started in 1974. During 1974-1975 the author
was in charge of the geological work in the
mining field as well as the regional prospecting in
western Finnmark.
Due to the falling prices of copper and small
production the mine was closed down in mid1975.
328
N. B.
NORSK GEOLOGISK TIDSSKRIFT 4 (1979)
Ho/lander
Geology
General
From west to east the rocks around the C-mine
are carbonate-rich rocks, feis, amphibolite,
carbonaceous schist, diabase, alternating feis,
and carbonaceous schist locally very rich in
chalcopyrite and pyrite, and finally greenstone
with amphibolite and diabase (Figs. l and 2).
These rocks form part of the Caskias-Group
which represents a period of intense and wide­
spread rather basic volcanic activity in the
Karelic geosyncline. The present survey has,
however, been carried out in much greater detail
than the earlier ones. Generally, Mathiessen's
map (1970) compares well with the present one.
Rocks
Carbonate rich rocks. - These have only been
found in two outcrops but are recognized in
many cores west and southwest of the C-mine.
They are diffusely layered, light brown-grey,
slightly weathered, fine to medium grained rocks
consisting of dolomitic and ankeritic carbonate
minerals with some amphibole. Pyrite occurs as
an accessory mineral in the eastern limestone
(lying around 800 E south of profile 1100 S)
which is fairly dean. The western carbonate
rock (situated between 600 and 775 E) is rich in
hornblende and to some extent also biotite.
Locally it contains actinolite and is slightly
schistose.
Diabase (metadiabase).- The diabase stretches
from profile O in the north to the south and
southeast, forming the upper central part as well
as part of the eastern limb of the big anticline.
The upper central part of the fold is filled with
the above mentioned carbonate-rich rock and
the diabase.
It is massive greenish black, fine to medium
grained rock consisting mainly of hornblende
and quartz with _some plagioclase and magnetite.
The colour changes to dark grey and greyish
green as the feldspar content increases. Carbo­
nate veins and lenses occur as well as tremolite
and some chalcopyrite towards the contact with
the feis in the eastern limb.
Amphibolite. - Amphibolite occurs east as
well as west of the feis and carbonaceous schist
in the eastern limb. It is a massive, locally
slightly schistose, greenish black, fine grained
rock consisting of hornblende, biotite, quartz,
albite-rich plagioclase, carbonate, magnetite and
pyrrhotite, and some chlorite. Aggregates (1.5-.
10 mm) of hornblende are common.
Feis. - This name is introduced to describe a
felsic, fine grained, massive, metamorphic rock
consisting of albite, quartz, and calcite. It has a
diffuse layering and/or heterogeneous bedding
with < 5 mm thick bands, white to greyish white,
grey or redbrown with a grain size of 0. 14l. 3
mm. The main mineral is albite, quartz and
calcite occurring in smaller amounts. Horn­
blende and biotite exist in small quantities.
Muscovite has been found but is rare. Some­
times the quartz exists in 1/2 mm lenses. 1/2 mm
aggregates of sericite and pyrophyllite (probably
secondary after sericite) tale and small zircon
crystals were found in drillhole 1440 S, 915 E, at
477 m, a.s.l. The feis is locally very rich in
chalcopyrite, pyrite, and pyrrhotite. Magnetite is
usually an accessory mineral. Galena and sphal­
erite have been found. The feis is sometimes so
fine grained ( <0. 01 mm) that identification of the
minerals in thin sections becomes impossible.
The rock is cut by irregular veins (< 5 cm) filled
with calcite and dolomiie, some quartz and
albite, with accessory biotite and iddingsite.
They can locally be very rich in chalcopyrite.
The feis is very similar to the leptites found in
the Precambrian of northern and middle Swe­
den.
Carbonaceous schist. - Diffusely bedded to
homogeneously layered, only locally schistose or
even brecciated, black to greyish black with thin
light grey to greyish white hands. The dark
hands are less than 10 mm thick and the light
ones less than 2 mm. The difference in colours
depends on the relative amounts of light and
dark minerals. The rock is very fine grained
(< 0. 03 mm) containing graphite, plagioclase,
carbonate, and quartz. Aggregates (less than 30
mm) consisting of biotite, plagioclase, and
quartz up to 0. 06 mm in size as well as 5 mm big
spots of phlogopite, sulphides, plagioclase, and
quartz of up to 0. 2 mm size. Pyrrhotite and
pyrite occur as a fine impregnation, in thin layers
or in carbonate filling. The graphite which exists
as impregnation and thin layers is enriched in
concordant zones in the C-ore. Transition to the
l. Geological map of the Bidjovagge mining field, western
Finnmark, Norway: 200N-750 S.
Fig.
NORSK GEOLOGISK TIDSSKRIFT
4 (1979)
Bidjovagge mining field
329
330
N. B. Hollander
NORSK GEOLOGISK TIDSSKRIFT 4 (1979)
600E
800E
Legend
�
m
�
E:TI
B
�
�
IWlJ
�
/20
j
Metadiabase
Amphibolite
Limestone
Albite-fels
Black schist
Sedimentary
greenstone
Schistose
Cu-mineralisation at or near surface
Cu-mineralisation in depth
Strike and dip
Fold axis with dip
.,;-" Fault
_
% -Syn form
-�-
antiform
25
50
75
100m
1000E
Bidjovagge mining fleld
NORSK GEOLOGISK TIDSSKRIFT 4 (1979)
feis is continuous, the difference lying mainly in
the
amount
of
carbonaceous
material.
The
331
The A-mineralization is limited to the north by
a N 80°E striking fault, dipping 85° SSE. The
graphite, which probably was formed from or­
northern block was lifted as compared to the
ganic material, is too fine grained to be economi­
southern one. Southwards the mineralization
cally concentrated.
gradually disappears from profile 60 N. It was
on!y mined to proflle 50 N.
Sedimentary greenstone. - A homogeneously
Some poor mineralization was also found in
layered or diffusely bedded rock with 2-20 mm
the same rocks in the western limb where it
thick layers, dark green to greyish green, fine
extends southwards for some kilometres.
grained with biotite, chlorite, amphibole, and
white feidspar and traces of pyrite. Zones rich in
The
amphibole and layers of feis occur. The tran­
mineralization in the field - the C-ore - also Iies
sition to feis is continuous.
in the eastern limb of the big N-S-striking
Mineralizations
ore lying between 890 and 925 m east and a west
The mineralizations are localized to the feis and
northern end of the east ore Iies at profile l040 S
C-mineralization.
anticline (Fig.
2).
-
The
best
copper
It consists of a good eastern
ore between 850 and 880 m east (Figs. 3- 5). The
carbonaceous schist of the legs of an isocline.
and the southern one at 1200 S in the open pit
The amount of sulphides is varying and although
(650-{)70 m a.s.l.) On leve! 600 (m a.s.l.) in the
generally poor it increases rapidly in the faulted
mine the ore Iies between 1050 and 1260 S. It is
and brecciated areas.
known down to 480 m a.s.l. extending from
The best mineralizations in the field - c alled B,
approximately 1100-1160 S. The west ore is
A, D, and C- are situated around the profiles 900
between 1085 and 1220 S on this level. In the
N, 1 00 N, 450 S, and 1200 S respectively. The
southern part it combines with the east ore. The
present paper, however, does not consider the
northern limit on leveis between 650 and 670 is
B- and D-mineralizations.
indicated to 1070 S while the southern end Iies
The A-mineralization.- The main mineralization
north- and southwards in the eastern limb of the
occurs in feis and schist on the eastern limb of
fold, but are normally of very low grade.
around I180 S. The mineralizations extend both
the big anticline (Fig. l), where the feis and the
interstratified
carbonaceous
schist
form
a
slightly broken synform.
The mineralizations consist of chalcopyrite,
pyrite, and some pyrrhotite; they occur as im­
pregnation, in irregular coarse grained albite­
The ore minerals are chalcopyrite, pyrrhotite,
carbonate (ankerite and calcite) veins, and in
and pyrite, all of which occur as impregnation
irregular layers concordant to the diffuse layer­
and in carbonate veins mainly in the feis but also
ing of the albite feis. The carbonate veins also
in the adjacent parts of the schist. Accessory
contain some muscovite, chlorite, and actinolite.
minerals are magnetite, hematite, and complex
The west-ore is rich in pyrite. Magnetite occurs
in the westernmost parts. Chalcopyrite is found
Ti-V-minera1s (Mathiesen
1969).
The mineralization is fairly rich in gold; the
in varying amounts dose to the carbonaceous
analyses showed 2-7 ppm Au in ore giving
schist together with some pyrrhotite. The west
20-102 ppm in 23% copper concentrate. The
ore contains an impregnation of galena and
lying wall between 140 and 80 N showed the
sphalerite (max. 0.4% Pb and 1. 5% Zn per ton of
highest gold content.
ore).
Although the age relationships between the
Around 910 E the feis normally has only
minerals have not yet been studied, the prelimi­
pyrite. The east ore, however, also contains
nary observations showed that the sulphides of
pyrrhotite with galena and sphalerite (max. 0.4%
the veins are younger than the gangue minerals.
Ph
Most of the pyrite seems to be older than the
chalcopyrite. The central parts only contain
and
2.4%
Zn
per
ton)
together
with
chalcopyrite; pyrite is found in idiomorphic
traces of sphalerite and even less amounts of
crystals which are brecciated and replaced by
galena.
chalcopyrite.
The central
and
synclinal
feis is
rich in
chalcopyrite with pyrite, minor pyrrhotite, and
Fig.
2. Geological map of the Bidjovagge mining field, western
Finnmark, Norway: 750-1600 S.
magnetite. South and above the ore pyrrhotite
with magnetite is common.
332
N. B.
Hollander
NORSK GEOLOGISK TIDSSKRIFT 4 (1979)
600
500
O
10
20
30 40
SOm
Leg end
400
PROFILE
D
m
�
[2]
�
Metadiabase
�
Schistose
Amphibolite
Limes tone
Albite-fels
Black schist
Sedimentary
greenstone
1120 s
Fig. 3. Geological east-west profile of the Bidjovagge mining field: 1120 S.
The carbonaceous schist contains pyrrhotite
schist are dipping steeply towards east around
with some pyrite and chalcopyrite at the con­
915-925' E
tacts with feis.
The western part of the black schist (between
The sulphides are mainly found in the feis and
adjacent parts of the schist. In lower parts of the
and striking north to north
5o
west.
880-900 E in profile 1120 S at 636-level) strikes
north 5-10 o E. Dip is 60-S0° E. The black schist
mine good mineralization occurs in the underly­
forms a synclinal with the closure to the north.
ing schist in the copper-bearing synform around
The fold axis dips 20-30° S, the central part being
900 E. Fig. 5 on the level 636 in the mine shows
filled with partly mineralized feis.
that the eastern feis and its contact with black
Just south of the
C-ore there is another
Bidjovagge mining field
NORSK GEOLOGISK TIDSSKRIFT 4 (1979)
333
+
600
>>>
>>>>
>>>>
>>>>
·>>>>
'>>>>
..... >>>
>>>>
>>>
'>>>
>>
+
500
PROFILE 1200 S
Fig. 4. Geological east-west profile of the Bidjovagge mining field: 1200 S.
225,000
In addition there are
in the west ore. The reserves total approximately
probably corresponds to the west ore in the C
2.3
million tons with
1.5%
tons with
1. 4%
chalcopyrite mineralization. Lying on the west
side of the eastern carbonaceous schist this
Cu
Cu.
mine. It was found between approximately 1250-
1380 S from 600-500
to 560-490 m a.s. l.
m a. s. l. in the northern part
in the southern part. This
mineralization is probably connected with the
one observed between
500
and
vertical
480
1440-1480
S roofing at
m a. s. l. respectively and with a
extension
of
approximately
100
m.
Mineralogically and petrographically the se are of
the same type as the C-ore.
The ore reserves in the eastern C-ore are
estimated as follows:
Between 600-650 m a.s.l.
Between 54� m a.s.l.
Between 480-540 m a.s.l.
The
ore
estimates
Between 480-540 m a.s.l.
The rocks in the Bidjovagge area are dominated
by a generally north-south striking anticline (F 1 )
500 E in profile O to 650
l). The western limb
strikes north-south at 500 E, while the eastern
one stands from 700 to l ,000 E. North of profile
700 S the fold axis dips to the north (15-30° at
profile 0). The carbonaceous schist just north­
with a central part from
E
in profile
1400
S (Fig.
west of D forms a syncline dipping north. The
Cu
150,000 t with 1.3% Cu
100,000 t with 1.3% Cu
in
southern
C-ore
10° N to 10° S between 700 and
1000 S the dip gradually in­
25-30° around profile 1200 S. These
dip varies from
550,000 t with 1.5%
mentioned above) are:
Between 540-640 m a.s.l.
Tectonics
1000
S. South of
creases to
(as
changes are due to flat-lying east-west striking
foldaxes (F2) which exist in the Caskias region.
The folding has been very important for the
Cu
785,000 t with 1.6% Cu
515,000 t with 1.6%
localization of the sulphides. Both the feis and
carbonaceous schist are highly folded and often
334
N. B.
11805
Ho/lander
[•'•''
.•.!..
����
[2]
�
!?Æ.]
/10
t
Limes tone
Albite-fels
Black schist
Sedimentary
<Teenstone
Strike and dip
Fold axis with
-%-Synform
1220
636
m
NORSK GEOLOGISK TIDSSKRIFT
4 (1979)
Bidjovagge mining fl.eld
NORSK GEOLOGISK TIDSSKRIFf 4 (1979)
disrupted. This caused the main mobilization of
the sulphides - both laterally towards troughs
but especially the crests of the folds, and trans­
versely into cross-fractures. It appears that the
relative mobility increases in the sequence py­
rite-sphalerite-pyrrhotite-galena. The thickening
at the crests and troughs has been coupled with
thinning out along limbs. This mobilization has
resulted in increased copper values in strongly
folded beds as compared with their less de­
formed equivalents.
In addition it seems that faulting and fissuring
were of significant importance for improving the
ore grade, i.e. it was observed that as faulting
decreases the amount of ore minerals also de­
creases. The faulting has taken place after the
folding. The most prominent faults occur in N
40-50° E. Another system strikes N 45-55° W. In
addition there is a third one (very weakly shown)
in east-west. These represent a combination of
blockfaulting and fissuring. As noted above, the
A-mineralization is limited to the north by east­
west faulting. The C and D mineralizations Iie in
areas with movements in north-easterly direc­
tion. In many other parts the rocks are broken
with secondary chloritization along fractures but
with no signs of displacement.
The ore genesis
The original geological setting of the rocks in
Caskias was a sedimentary basin in which there
was a widespread volcanic activity. The feis
probably represents the volcanic ashes settling
in a reducing millieu of organic black clays
alternating with more carbonaceous material.
The sulphides could have come from submarine
syngenetic exhalations being precipitated in the
smaller depths in various amounts. Later folding
and faulting mobilized the sulphides and pro­
vided new space for deposition and concentra­
tion across the original sedimentary boundaries.
The author is indebted to AlS
Sydvaranger for permission to publish the data, and to the
director of the prospecting department, T. L. Sverdrup, for his
great interest and many fruitful discussions. Thanks are due to
Professor J. A. W. Bugge for valuable discussions and con·
structive criticism of this paper.
In the field the author bad great help from geologists H.
Delin and S. E. Bull. He is most grateful to the technical staff
at the laboratory of the mining office in Kirkenes for all
Acknowledgements.
335
chemical analyses, and to Saga Petroleum a. s. for the exten­
sive drafting.
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Fig. 5.
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336
N. B. Ho/lander
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NORSK GEOLOGISK TIDSSKRIFT 4 (1979)