Economic Geology
Shayan Akrami; Mohammad Ali Aliabadi; Mohammad Reza Hazareh; Abbas Askari; Tayebeh Ramezani
Abstract
Nineh Pb-Zn deposit is located in the east of the Markazi province, in the Middle to Upper Jurassic rock units of the Malayer-Esfahan metallogenic belt. Stratified and epigenetic mineralization, in the form of veins, replacement and open spaces filling, including the main minerals of galena, sphalerite ...
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Nineh Pb-Zn deposit is located in the east of the Markazi province, in the Middle to Upper Jurassic rock units of the Malayer-Esfahan metallogenic belt. Stratified and epigenetic mineralization, in the form of veins, replacement and open spaces filling, including the main minerals of galena, sphalerite and barite accompanied by dolomite and siliceous alterations are observed. The microthermometry results of fluid inclusions in calcite and barite, display mean homogenization temperature of about 168.6°C and 127.3°C, and a mean salinity of 5.7 and 13.9 wt. % NaCl equiv., respectively, which indicates slight difference in their formation conditions. The homogenization temperature versus salinity diagram suggests a basinal brine fluid mineralizer and mixing and cooling processes for the mineralization. The values of δ34S in galena and sphalerite (7.5‰ to 21.5‰) of this deposit are similar to the values of δ34S in the upper Mississippi deposits, indicating the supply of sulfur during the process of thermochemical reduction of sulfate. The values of δ18OSMOW (-9.2 to -11.2‰) and δ13CPDB (0.1 to 0.5‰) of the calcite veins indicate a multi-origin of oxygen, and the origin of carbon from dissolved and remobilized marine carbonates. According to the evidence obtained during this study, the Nineh deposit can be classified as the Mississippi Valley type deposits, which was formed during the orogeny processes and the movement of basinal brine fluids.
Economic Geology
Zahra Akbari; ali yarmohammadi; Iraj rassa
Abstract
The Fe-Pb Ahangaran deposit, hosted by tuffaceous siltstone of the Early Cretaceous sedimentary sequence in the northern part of the Malayer-Esfahan Metallogenic Belt (MEMB), Iran. Ore mineralization occurred as stratiform and a widespread veinlet zone in the upper part of Lower Cretaceous terrigenous ...
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The Fe-Pb Ahangaran deposit, hosted by tuffaceous siltstone of the Early Cretaceous sedimentary sequence in the northern part of the Malayer-Esfahan Metallogenic Belt (MEMB), Iran. Ore mineralization occurred as stratiform and a widespread veinlet zone in the upper part of Lower Cretaceous terrigenous unit (Kc). Four different ore types can be distinguished in deposit include: (1) veinlet (feeder) zone, (2) sulfide-Fe- oxide stratiform ore (3) barite ore and (4) vein ore. Ore minerals in the different ore types are pyrite, siderite, magnetite, galena, barite, chalcopyrite and tetrahedrite and rare minerals are pyrrhotite, arsenopyrite, and freibergiteCarbonatization and silicification are the main hydrothermal alterations in this deposit. The orebodies in the Ahangaran deposit have been replaced by iron oxide minerals in supergene process and have been formed a thick gossan zone. The textural and mineralogical data provide evidence of three stages of mineralization (Early, main and late stage) in Ahangaran deposit. According to evidences such as tectonic setting, type of host rock, geometry of deposit, sulfide-Fe oxide ore types, textures and structures indicate that the Ahangaran deposit is compatible with a sub-seafloor replacement mineralization that has been suggested for some Sedex deposits.
M. Movahednia; E. Rastad; R. Rajabi; F. J. González
Abstract
The Ab-Bagh Zn-Pb deposit is located 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 ...
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The Ab-Bagh Zn-Pb deposit is located 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 massive ore,concordant with the host rock layering; Syn-sedimentary faults, half-graben basins and related anoxic environments, had an important role in formation of SEDEX-type Zn-Pb mineralization in the Ab-Bagh and deposition of sulfides. Sedimentary debris flows and syn-sedimentary braccia within host rocks of the Ab-Bagh deposit suggests activity of normal faulting simultaneously with sedimentation of host rock and consequently development of half- graben structures. Formation of half-graben structures is one of the most important factors of redox condition of ore forming environment. This structures led to development of deeper zones within the basin, where anoxic condition were occurred. Trace and rare earth elements geochemistry of host rocks, size of pyrite framboids and presence of organic matter in the host rocks, represent anoxic to euxinic paleo-redox condition of this basin, which is caused by microbial activities and depth of the basin,associated with normal syn-sedimentary fault. Comparison of syn-sedimentary normal faulting and anoxic formation environment of the Ab-Bagh deposit with other SEDEX deposit of Iran, indicates similarity of their formational environment.
