Economic Geology
Amir Pakizeh; Fardin mousivand; Abdorrahman Rajabi; Sajjad Maghfouri
Abstract
The Nohkuhi copper deposit located at 40 Km Northwest of Kerman, occurred in the Central Iran structural zone (Bafq- Posht-e- Badam block), within Late Precambrian-Early Cambrian volcano-sedimentary sequences. Host sequence of mineralization consists of dominantly black shale, sandstone and dacitic lava ...
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The Nohkuhi copper deposit located at 40 Km Northwest of Kerman, occurred in the Central Iran structural zone (Bafq- Posht-e- Badam block), within Late Precambrian-Early Cambrian volcano-sedimentary sequences. Host sequence of mineralization consists of dominantly black shale, sandstone and dacitic lava of Rizu Series. Mineralization occurred as stratabound (vein-veinlets) and stratiform (bedded) in the three copper- and two iron-manganese horizons. The mineralization in the Nohkuhi area involves four ore facieses including stringer, vent complex, bedded, and hydrothermal-exhalative banded iron and manganese-rich sediments. This mineralization contains primary pyrite, chalcopyrite, sphalerite, hematite and pyrolusite. Wallrock alterations are dominated by chloritic and carbonatic-sericitic- silicic. Metal zonation was observed in the deposit. Based on characteristics of mineralization, such as tectonic setting, host rocks, ore textures and structures, mineralogy, metal and alteration zonation, and comparison with main characters of the volcanogenic massive sulfide (VMS) deposits, the mineralization shows most similarities with the siliciclastic felsic or Bathurst- type deposits.
Economic Geology
Pouria Mahmoodi; Ebrahim Rastad; Abdorrahman Rajabi; Mehran Moradpour
Abstract
The Early Cretaceous Eastern Haft-Savaran Zn-Pb (Ba) deposit situated in the Arak mining district and occurred within the extentional back-arc of Malayer-Esfahan basin. Mineralization occurred in two horizons in the Estern Haft-Savaran deposit. First horizon is major horizon that formed within the most ...
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The Early Cretaceous Eastern Haft-Savaran Zn-Pb (Ba) deposit situated in the Arak mining district and occurred within the extentional back-arc of Malayer-Esfahan basin. Mineralization occurred in two horizons in the Estern Haft-Savaran deposit. First horizon is major horizon that formed within the most upper portion of the massive limestone and second horizon occurred in the thin limestone which is alternate with shale and marl. Textures of the mineralization in this deposit are replacement, massive and vein- veinlets, and main alterations are silisification, dolomitization and calcitization. Sphalerite, galena, chalcopyrite, tetrahedryte, pyrite, bornite, chalcosite and covelite are the sulfide minerals and quartz, calcite, dolomite and sericite are gangue minerals in the ore deposit. Cathodoluminescence study in this deposit indicates three dolomites and one calcite generations. First generation of dolomite associated with weak mineralization and second generation of dolomite is Fe-rich and associated with main mineralization. Third generation of dolomite is late dolomitization and formed with calcite and cross-cutted the mineralization. Presence of framboidal pyrite with galena and sphalerite in its matrix and fine-grain euhedral barite suggest mineralization began during sedimentation and early diagenesis stage near seafloor. In continuum, main ore is identified as replacement occurrence of first generation sulfides by second generation coarse-grained sulfides under seafloor. With regarding to the formation of the Eastern Haft-Savaran deposit in the extentional tectonic setting, massive limestone as the host rock, and mineralization formation as replacment during diagenesis of the host rock under the seafloor, this deposit would be classified as Irish type deposit.
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
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).
A. Rajabi; E. Rastad; N. Rshidnejad Omran; R. Mohammadi Niaei
Abstract
Chahmir Zn-Pb deposit is one of several sediment-hosted Zn-Pb deposits (e.g., Koushk, Zarigan, Dareh Dehu & Cheshmeh Firuzeh) located in southeast of Bafq basin hosted within a Early Cambrian volcano-sedimentary sequence, simultaneous with global Cambrian ocean anoxic event, forming in a rift environment. ...
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Chahmir Zn-Pb deposit is one of several sediment-hosted Zn-Pb deposits (e.g., Koushk, Zarigan, Dareh Dehu & Cheshmeh Firuzeh) located in southeast of Bafq basin hosted within a Early Cambrian volcano-sedimentary sequence, simultaneous with global Cambrian ocean anoxic event, forming in a rift environment. The host rock units of the Chahmir Zn-Pb deposit includes organic-rich black siltstones with intercalations of tuff and silty tuff overlain by green carbonaceous tuffs. Based on nature of sulfide mineralization, mineralogy and textures of sulfide minerals, the Chahmir deposit can be divided into four different facies. Based on their situation towards the vent of mineralization fluid, these facies include: 1) A massive ore facies (Vent Complex) forms the thicker part of generally massive higher grade ores in east of the deposit. This facies includes two subfacies: the sulfide-silica-carbonate subfacies in center of massive ore and sulfide-carbonate subfacies around it. Sulfide minerals are observed as massive, replacement, vein-veinlets and brecciated colloform textures. 2) Vein-veinlets facies (Feeder Zone) includes sulfide veins and silica that form as a scissors of host rocks under the massive ore facies. Vein-veinlets and replacement textures form main features of this facies. 3) Bedded ore facies which is thinner than the massive ore facies and is characterized by layered and banded feature and low grade ore. This facies occurs as stratiform laminated and banded sulfides contemporaneous with the formation of the host rocks. 4) Distal facies is formed at west of the deposit which is actually a sedimentary equivalent of bedded ore facies. Main characteristics of this facies are presence of disseminated pyrite, banded chert and barite. The most important characteristics of mineralization at the Chahmir deposit such as tectonic setting, host rocks, mineralogy, diffrent facies, show similarities to siltstone and shale hosted Zn-Pb Sedex type deposits. Accordingly, Chahmir is regarded as a Selwyn-Type (Vent Proximal) SEDEX deposit.
