Economic Geology
M. Movahednia; E. Rastad; A. Rajabi; F. Choulet
Abstract
The Ab-Bagh Zn-Pb deposit is located in the central part of the Sanandaj-Sirjan zone (SSZ) and at the southeastern part of the Malayer-Esfahan metallogenic belt. This deposit is hosted by Upper Jurassic-Lower Cretaceous sedimentary sequence. Zinc and lead mineralization occurred within two horizons. ...
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The Ab-Bagh Zn-Pb deposit is located in the central part of the Sanandaj-Sirjan zone (SSZ) and at the southeastern part of the Malayer-Esfahan metallogenic belt. This deposit is hosted by Upper Jurassic-Lower Cretaceous sedimentary sequence. Zinc and lead mineralization occurred within two horizons. The ore horizon 1 is hosted by Late Jurassic-Early Cretaceous black shale and siltstone. The ore body displays a wedge-like shape and is located close to syn-sedimentary fault. The ore horizon 2 occurs in lower Cretaceous carbonates and includes a massive ore facies that is concordant with host rock layering. It is also underlain by a stockwork facies. Weathering processes led to a supergene ore stage at Ab-Bagh deposit in parts toward the surface. Based on geology, mineralogy and geochemistry, two types of non-sulfide ore were distinguished: the white ore and the red ore. The white ore is a wall-rock replacement mineralization that contains high Zn, low Fe and a very low concentration of Pb. To the opposite, the red ore formed after the direct replacement of sulfide protore and it typically contains low Zn, high Fe and medium Pb± As concentrations. Supergene ore consists of smithsonite and hydrozincite. Minor cerussite, Zn-rich clays, greenockite, covellite and Fe-Mn oxides were also identified. The supergene part of the Ab-Bagh deposit formed as a consequence of long time weathering of a SEDEX-type sulfide protore. Oxidation of sulfide minerals (mainly pyrite and sphalerite), carbonate buffering reactions and precipitation of secondary Zn-bearing minerals are the main geochemical process involved. The REE patterns of the white non-sulfide ore are similar to that recorded in the host rocks but REE patterns of red ore, is similar to sulfide ore. The comparison with other major non-sulfide Iranian deposits suggests that Ab-Bagh deposit is very similar to Kolahdarvazeh and Mehdiabad deposits; it also shows lots of similarities with other worldwide examples (e.g. Moroccan non-sulfide ore deposits).
Z Miriyan; M Lotfi; A.A Shabani; M.A.A Mokhtari; E Haj Molla Ali
Abstract
The Kharengun area is located in the Yazd province, Central Iran, 130 km east of Yazd city and 65 km northeast of Bafq city. Mineralization in Kharengun area occurred within calcic and dolomitic units of the Rizou Formation (equivalent to Soltaniyeh Formation) of upper Precambrian- lower Cambrian age. ...
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The Kharengun area is located in the Yazd province, Central Iran, 130 km east of Yazd city and 65 km northeast of Bafq city. Mineralization in Kharengun area occurred within calcic and dolomitic units of the Rizou Formation (equivalent to Soltaniyeh Formation) of upper Precambrian- lower Cambrian age. The ore minerals of this deposit includes smithsonite and hemimorphite, that is stratabound and formed epigenetically along layers and laminations of carbonate host rocks. The maximum grade of zinc in samples taken from the study area exceeds 36% and geochemical studies indicate significant absence of Pb along with Zn in this area. Therefore, the Kharengun mineralization is a monomineral Zn zone.The fluid inclusion microthermometry investments explain the role of meteoric waters in generation of this deposit. The homogenization temperatures and salinity of the inclusions show the similarity between these fluids and the solutions responsiblefor the development of epithermal deposits.The Zn mineralization present in this zone belongs to the nonsulfide supergene deposit class, and a mixture of wallrock replacement and direct replacement subclasses.
N. Fatehi Gelab; H Mirnejad; R Mathur
Abstract
The Darrehzar and Parkam deposits in Kerman province are two examples of porphyry type copper deposits in the Cenozoic Urumieh- Dokhtar magmatic arc. Volcanic rocks in the study areas are dominantly composed of andesite, trachyandesite and basalt. The Darrehzar quartzmonzonite stock consists of phenocrysts ...
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The Darrehzar and Parkam deposits in Kerman province are two examples of porphyry type copper deposits in the Cenozoic Urumieh- Dokhtar magmatic arc. Volcanic rocks in the study areas are dominantly composed of andesite, trachyandesite and basalt. The Darrehzar quartzmonzonite stock consists of phenocrysts of plagioclase, hornblend, quartz and biotite, andconstituent minerals of diorite-microdiorite porphyry in Parkam include plagioclase, alkali-feldspar, amphibol, biotite and quartz. The thickness of oxide zone in Darrehzar deposit is few meters and in many well cores it cannot be obsereved at all, while the the thickness of leached zone varies between 2 and 80 m. Supergene zone in the center of this deposit has the greatest thickness (120 m). The depth of hypogene zone from Darrehzar is 400 m. The thickness of leached zone from Parkam is around 20 m. The average thickness of supergene zone in this deposit is 15 m and its maximu depth is 64 m. The depth of hypogene zone in some cores is around 500 m. Evalutating the Cu isotope ratios from leached, supergene and hypogene zones in these two deposits show that the magnitude of Cu isotopic fractionation and Cu concentrations are mainly controlled by the weathering processes. The average δ65Cu values of copper in the leached, supergene and hypogene zones in Darrehzar deposit are, respectively, -6.16‰, +2.52‰ and +0.79‰, and those in the Parkam are -4.33‰, +4.82‰ and +0.34‰. Therefore, weathering of Cu sulfide minerals generated isotopically lighter residual minerals and dispersed the heavy isotope to the percolating groundwaters. It is thus expected that the copper isotope ratios of the leached zones in various porphyry copper deposits to be linked with the extent of leaching and the supergene enrichment processes. Microscopic studies and mineralogical studies shows that hematite in the Darrehzar’s leached zone in more abundant than that in the Parkam, while Parkam’s leached zone contain higher goethite content relative to that of the Darrehzar. The amount of chalcosite, and pyrite–chalcopyrite in the supergene and hypogene zones, respetively, from Darrehzar, are more abundant compared to those in the equivalent zones in Parkam.
