Geochemistry and fluid-inclusion microthermometry of the Farsesh barite deposit, Iran
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Date
2014-09
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Publisher
Instytut Geologii UAM
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Abstract
The Permian carbonate-hosted Farsesh barite deposit is located southeast of the City of Aligudarz in the prov -ince of Lorestan, Iran. Structurally, this deposit lies in the Zagros metallogenic belt and the Sanandaj-Sirjan Zone.
Barite mineralisations occur as open-space filling veins, and as massive and replacement ores along fractures,
faults and shear zones of the Permian carbonate host rocks. In order to determine the structure, in addition to pe -trographic and fluid-inclusions studies, an ICP-MS analysis was carried out in order to measure the major as well
as the trace and rare earth elements. The Farsesh barite deposit has a simple mineralogy, of which barite is the
main mineral, followed by calcite, dolomite, quartz, and opaque minerals such as Fe-oxides. Replacement of bar -ite by calcite is common and is more frequent than space-filling mineralisation. Sulphide minerals are minor and
mainly consist of chalcopyrite and pyrite, which are altered by weathering to covellite, malachite and azurite.
Petrographic analysis and micro-thermometry were carried out on the two-phase liquid/vapour inclu -sions in ellipsoidal or irregularly shaped minerals ranging in size from 5–10 µm. The measurements were
conducted on fluid inclusions during the heating and subsequent homogenisation in the liquid phase.
The low homogenisation temperatures (200–125°C) and low to moderate salinity (4.2–20 eq wt% NaCl) in -dicate that the barite had precipitated from hydrothermal basinal water with low to moderate salinity.
It appears from the major and trace elements that geochemical features such as Ba and Sr enrichment in the barite
samples was accompanied by depletion of Pb, Zn, Hg, Cu and Sb. The geochemistry of the rare earth elements, such
as low ΣREE concentrations, LREE-enrichment chondrite-normalised REE patterns, the negative Ce and positive Eu
anomalies, the low Ce/La ratio and the positive La and Gd anomalies, suggest that the Farsesh barite was deposited
from hydrothermally influenced sea water. The Farsesh deposit contains low-temperature hydrothermal barite. The
scatter plots of the barite (close to sea water) in different areas on the CeN/SmN
versus CeN/YbN diagram support the
possibility that the barite was formed from seawater-bearing hydrothermal fluids.
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Keywords
hydrothermal barite, ICP-MS analysis, geochemistry, fluid inclusions, Sanandaj-Sirjan Zone, Iran
Citation
Geologos, 2014, 20, 3, s. 201-214
Seria
ISBN
978-83-232187-4-6
ISSN
1426-8981