Economic Geology
S. Maghfouri; M. R. Hosseinzadeh; A. Rajabi; A. M. Azimzadeh
Abstract
Darreh-Zanjir Zn-Pb deposit is located at the south of Taft city. Sulfide minerals in this deposit include sphalerite, galena and pyrite. Replacement, open space filling, vein-veinlet, breccia and massive are the typical textures in the Darreh-Zanjir deposit. Mineralization is associated with normal ...
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Darreh-Zanjir Zn-Pb deposit is located at the south of Taft city. Sulfide minerals in this deposit include sphalerite, galena and pyrite. Replacement, open space filling, vein-veinlet, breccia and massive are the typical textures in the Darreh-Zanjir deposit. Mineralization is associated with normal fault. Gange mineral is dolomite and dolomitization is related to mineralization. Three types of dolomite have been recognized in the Darreh-Zanjir region: 1- Regional dolomite, formed during diagenesis of micritic limestone of the Taft formations and is exposed in whole region. It has dark gray color and fine crystals. 2- Thrusting dolomite, formed during compression and thrusting of the Taft formation on the Darreh-Zanjir formation, this dolomites are located at the vicinity of thrust fault.3- Mineralization and dolomitization occur adjacent to normal fault. This dolomite is known as hydrothermal dolomite (DH) and it decreases away from of sulfide mineralization. Geochemical studies suggest that high content of cadmium in sphalerites represents low temperature for ore forming fluid. Supergene and oxidation process caused change of sulfide minerals to non-sulfide minerals. Non-sulfide minerals of the Darreh-Zanjir deposit are smithsonite, hemimorphite, hydrozincite, cerrusite and Fe-oxides and hydroxides. The most important characteristics of mineralization at the Darrh-Zanjir deposit such as tectonic setting, post compression of normal fault controlling mineralization, host rocks, mineralogy, metal content as well as wall textures, show similarities with Mississippi Valley-type (MVT) Zn-Pb deposits.
Economic Geology
S. Amani Lari; I. Rassa; A. Amiri
Abstract
Ahmadabad Zn-Pb deposit is one of the Pb-Zn deposits in the Kouhbanan-Bahabad metollogeny Belt, which is located 10th Km northwest of Bahabad City in the Posht-Badam Block in Centeral Iran Zone. Ore deposits consist of Zn, Pn, Mo and Sr non-sulfide minerals with large amount of Fe oxide-hydroxide ...
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Ahmadabad Zn-Pb deposit is one of the Pb-Zn deposits in the Kouhbanan-Bahabad metollogeny Belt, which is located 10th Km northwest of Bahabad City in the Posht-Badam Block in Centeral Iran Zone. Ore deposits consist of Zn, Pn, Mo and Sr non-sulfide minerals with large amount of Fe oxide-hydroxide minerals occurred in dolomitic host rock of the Shotori Formation. A quartz-calcite vein accompanies ores in the host rock. This study is focused on C-O isotopic variation in the host rock, quartz-calcite vein and hydrozincite. Isotopic variation of C indicates that the source of carbon is different in the host rock and quartz-calcite vein. The most important source of carbon for hydrozincite formation was carbonate rocks of the area and regarding this aspect this deposit is different from others Zn-Pb non-sulfide deposits that studied in the world. According to oxygen isotopic variation, the temperature for hydrozincite formation was between 14-44˚C. The oxygen isotopic variation suggests marine basin water as the source of quartz-calcite vein. The dolomitic host rock was formed in equilibrium with fluids of a mixture of marine and magmatic waters, based on oxygen isotopic variation.
Economic Geology
R. Amirkhani; M. Ebrahimi; M. A. A. Mokhtari; A. M. Azimzadeh
Abstract
The study area which is introduced as Homeijan magnetite- apatite mineralization in this paper, is a part of the Posht-e-Badam block in the Central Iranian Zone and is located at ~12Km southwest of Behabad. This area is composed of volcano-sedimentary rocks and acidic- basic intrusions of Precambrian ...
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The study area which is introduced as Homeijan magnetite- apatite mineralization in this paper, is a part of the Posht-e-Badam block in the Central Iranian Zone and is located at ~12Km southwest of Behabad. This area is composed of volcano-sedimentary rocks and acidic- basic intrusions of Precambrian and Cambrian age. Magnetite- apatite mineralizations are present as lenses near the southwestern part of the Homeijan village, which are hosted by acidic- intermediate tuffaceous rocks and dolomites. Magnetite, oligist (hematite), pyrite and chalcopyrite are the main ore minerals and apatite, pyroxene, tremolite- actinolite, calcite and quartz are as gangue minerals in the Homeijan Fe mineralization. Based on field and mineralogical studies, this mineralization texturally includes massive, brecciated, vein- veinlets and replacement textures. Chemical analyses of samples indicate that the mineralization has high concentrations of REEs up to 2.5 % in the apatite crystals. Geochemical studies demonstrate that Fet have high negative correlation with P2O5, SiO2 and ∑REE while there is a high positive correlation between ∑REE and P2O5. SEM-EDS qualitative analyses of apatite crystals indicate two REE bearing minerals including monazite and allanite as inclusions within the apatites. Furthermore, this study demonstrates that the apatite crystals are flour- apatite. Fluid inclusion studies within the apatite crystals indicate that main salinity varies between 7.86-13.9 wt.% NaCl and homogenization temperature is between 240-370°C. Comparing of REE patterns of Homeijan magnetite- apatite mineralization with other iron oxide- apatite mineralizations of Posht-e-Badam Block and Kiruna- type iron ores indicate similarities between these patterns. Generally, based on field and geochemical studies, the Homeijan magnetite- apatite mineralization classified as Kiruna- type Fe deposit.
Economic Geology
A. Baharvandi; M. Lotfi; M. Ghaderi; M. R. Jafari; H. A. Tajeddin
Abstract
Shekarbeig barite deposit is located 46 km southwest of Mahabad in northwestern part of the Sanandaj-Sirjan zone. The outcropped rock units in the area are Late Protrozoic metamorphosed volcano-sedimentary rocks, equivalent to Kahar Formation. The main ore mineral occurs as stratiform barite lenses in ...
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Shekarbeig barite deposit is located 46 km southwest of Mahabad in northwestern part of the Sanandaj-Sirjan zone. The outcropped rock units in the area are Late Protrozoic metamorphosed volcano-sedimentary rocks, equivalent to Kahar Formation. The main ore mineral occurs as stratiform barite lenses in three horizons accompanied by sulfide minerals as massive and/or parallel bands within metamorphosed rhyolitic tuffs (metatuff). The deposit footwall is composed of phyllite and slate crosscut by silicic and sulfide-bearing barite veins and veinlets (stringer zone). Primary minerals in the ore are mainly barite, pyrite, marcasite, chalcopyrite and bornite and secondary minerals are chalcocite, covellite, malachite, siderite, goethite, hematite and other iron hydroxides. Gangue minerals include quartz, sericite, calcite, dolomite, feldspar and chlorite. In terms of metallic ores, the Shekarbeig deposit does not vary much having only pyrite and chalcopyrite. Types of fluid inclusions in the Shekarbeig deposit are two-phase liquid-vapour (LV), mono-phase vapour and mono-phase liquid; two-phase liquid-vapour being the dominant type in both stringer and stratiform parts. Sulfur isotope data indicate that seawater was the main mineralizing fluid for Shekarbeig mineralization. These data suggest that complete reduction of recent seawater sulfate and the rate of mixing of hydrothermal solution with cold waters in deep parts of the basin may result in precipitation of large amount of sulfides in the stringer and stratifrom zones. On the other hand, partial reduction of recent seawater sulfates provided required sulfur for the deposition of barite. Geological evidence, evaluation, lithostratigraphy, mineralization geometry and the results of fluid inclusion and sulfur isotope studies for samples from the Shekarbeig deposit indicate derivation of the hydrothermal fluids of low salinity and moderate temperature from seawater and circulation and upward movement by a heating source (probably subvolcanic intrusions) and finally cooling and deposition of the fluids as sulfate and sulfide on the sea floor due to mixing with seawater, similar to massive sulfide Kuroko-type deposits.
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).
