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Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
Most of the Turkish iron ore production comes
from central-eastern Anatolia, and the iron
deposits in the Sivas–Malatya region account
for about 61% of the country’s production. The
Akdag deposit, located in the vicinity of Divrigi
region in southeastern Sivas, Turkey, is a
chemical sedimentary type iron deposit. Iron
deposit was formed concordantly to the
bedding within the Bozbel Formation which is
composed of sandstone with ore pebbles and
Nummulitic limestone-marl alternation.
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Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
In this study, depositional environment of the Akdag iron deposit is discussed in
regard to mineralogical, geochemical and isotopic data. In the Akdag iron deposit,
magnetite is the primary ore mineral, whereas goethite and hematite are secondary
ones. XRD patterns and ore microscopy studies indicate that sedimentation also
played an important role in deposition.
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Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
During the deposition process, iron was transported to the marine environment where
it was deposited in aqueous and also fragmental form. Stable isotope data (δ18O) on
hematite samples yield that the ore is not associated with the hydrothermal fluids and
δ18O values resemble those of the banded iron formations (BIF) indicating a
sedimentary precipitation.
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Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
As a result of studies, Akdag iron mineralization is of chemical sedimentary type
and was deposited in a shallow marine environment (hdyrogenetic). Iron is most
likely transported to this environment in detritic, adsorbsive, absorbtive, colloidal
or/and gel state from the older iron deposit or underlying ultramafic rocks.
Karstification developed within fault zones remobilized the ore. By this way, the
iron deposit took its present shape and character.
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Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
Iron
deposit
was
formed
concordantly to the bedding within
the Bozbel Formation which is
composed of sandstone with ore
pebbles and Nummulitic limestonemarl alternation. As a result of postdepositional
processes,
the
mineralization
was
tectonically
emplaced within the host rocks.
Based on fossil assemblage, the
deposit is of Cuisian age.
There are debates about the
occurrence of the deposit and
according to some researchers
(Öztürk 2005) primary ore which is
developed in limestone with intrusion
by hydrothermal fluids was formed
along
a
serpentinite-limestone
through karstic processes. There are
also other studies stating that the ore
deposit is either tectonically situated
within
the
limestone
and
demonstrates
sedimentary
(conglomeratic) bedding properties
(Ünlü and Stendal 1986, 1989).
Moreover, this deposit is interpreted
to have been deposited in a shallow
marine environment (Yılmaz et al.,
2005).
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
In the Akdag iron deposit, magnetite is the primary, hematite
and goethite are secondary ore minerals.
In ore microscopy, two types of hematite and goethite are
discriminated:
The first type hematite is transformed from euhedral
magnetite which partly shows sign of transportation and
has been martitized along the relicts.
The second type hematite occurs replacing the sedimentary
grains revealed by typical ringförmig and colloidal
structures.
The first type goethite is formed by alteration of hematite.
The second type goethite settles down in a later stage and
fill the space between magnetite grains.
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
Ore Microscopy and SEM images
Pinkish-gray magnetite stains
and relict textures in completely
hematized magnetites; white
parts are martite (sample No:
19)
Hematited magnetite and
goethite mineral dissolution in
edge-crack (sample No: 46)
Layer
surface
Hematite layers
(Sample No: 46)
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Kalsitin boşalttığı
hacimce yerleşen
1, Taner Ünlü1
Ece Varol
hematitler,
küresel
oluşumlar (Örnek
1Ankara University
No:42)
Spherical
hematite
a) Hematite forming a
"ringförmig" structure, b)
Goethite substituting
hematite, cement grains and
gangue (Sample No: 14)
a) Hematite
replaces
carbonate gangue
(at the right side
approx.75°-angle
romboeder
shapes) and
gangue is
substituted by
hematite b) The
hematite is
substituted along
a crack by a
young gangue
(Sample No:42)
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
1st Group
XRD Patterns
In the first group ores, calcite and dolomite
contents are higher but iron minerals are in
relatively low abundance.
2nd Group
In the second group ores, calcite and dolomite
contents are low but iron minerals are dominated.
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
Trace element geochemistry
REE’s of ore samples are found to be enriched 10- to
100-fold with respect to PAAS and NASC. In comparison
with chondrite, LREE’s are enriched 1 to 50-fold whilst
HREE’s remained unchanged. This indicates that ore
composition is close to marine characteristics. Weak Ce
and Eu negative anomalies are hardly visible in the same
graph.
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
Detritic iron derived from weathering of terrestrial
units may be transported to the marine
environment. Relations between major, trace and
rare earth elements indicate that in the course of
deposition of Akdağ iron ore, iron (detrital) was
dissolved in the seawater and partly preserved its
primary ore form. Such ores deposits within the
aqueous environment called “hydrogeneous” type.
(Hren et al., 2006)
(Nicholson, 1992)
(Wonder et al., 1988)
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
Fe2O3 values of ore samples are divided into two groups.
Values of the first group are between 70-93 %, whereas those
of second group range from 90 to 94 %.
In the studied iron deposit, Eu/Eu*, (La/Yb)n and Ce/Ce* ratios
are 1.63 (average), 1 and 0.75-1.06, respectively. The average
HREE and LREE values are 0.15 and 1.25. La/Ce and Y/Ho
ratios are 0.5-1 and 10-36.
Low La/Ce and high Y/Ho ratios and HREE enriched patterns
encourage that the Akdag iron deposit was precipitated in a
shallow marine environment.
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
δ18O and δ13C Isotope composition of
calcite and dolomite (carbonate host rocks)
According to stable isotope studies conducted on
calcite and dolomite samples of the carbonate host
rocks, δ13C values (VPDB) are -5.91 to +3.52 permil
for calcites and -1.01 to +5.68 permil for dolomites
and δ18O values (VSMOW) are +21.94 to +27.27
permil for calcites and +25.39 to +29.55 permil for
dolomites.
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
In dolomite samples increasing MgO and CaO
concentrations with enrichment of heavy oxygen
(18O) and carbon (13C) isotopes of the carbonate
host rocks is explained by evaporation and/or
diagenesis. It is determined that Sr concentration
of dolomites is reduced as the δ18O and δ13C
values are lowered. It can be said that dolomites in
study area most are likely interacted with fluids
which have different Sr concentrations. Without Sr
isotope data, it is hard to speculate that fluids are
of metamorphic or magmatic origin.
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
δ18O Isotope composition of hematite
δ18O values of hematite samples are between -2.49 and -0.01 ‰.
Mineralogical, Geochemical and Isotopic Investigation of the
Akdağ (Divriği-Sivas) Iron Deposit, Turkey
Ece Varol1, Taner Ünlü1
1Ankara University
Hematite
Magnetite
In diagrams where δ18O values are
plotted against SiO2, MgO and Fe2O3, a
positive
correlation
between
concentrations of these elements and
heavy oxygen isotope (18O) in hematite
samples might indicate a magmatic
and/or metamorphic source.
Hematite
Magnetite
Hematite
Magnetite
In δ18O values plotted against SiO2, MgO
and Fe2O3 diagrams,
hematite and
magnetite samples fall into different areas
because magnetite has I-18O index grater
than that of hematite.