Document Type : Original Research Paper
Authors
1 Geology Dept., Tarbiat Modarres University, Tehran, Iran
2 Petroleum Engineering Dept., Amir Kabir University of Technology, Tehran, Iran
Abstract
Ahmad-Abad Zn, Pb (Mo) deposit is located in Central Iran and Posht-e-Badam Block. This deposit is limited in dolomitic units of Shotori Formation (Middle Triassic) with lens type geometry parallel to layering Ahmad-Abad Zn, Pb (Mo) mineralization which is a stratabound ore deposit and sometimes vein type. The result shows that the ranges of Zn are 5-20% (average 9%), Pb 5-9% (average 5%) and Mo 83 ppm to 3.09% (average 0.7%). The study of lithogeochemical sections indicates that mineralization has occurred in a specific stratigraphic position related to special sedimentary facies including dolomitic Oosparite Ooide grainstone dolosparite facies. Faloric and texture of ores include laminated, disseminated, open-space filling, massive, brecciated, vein and veinlet, stylolite fishing and replacement. The presence of textures such as laminated, disseminated and stylolite type which is related to Ooide grainstone reveals that ore formation has occurred during diagenetic stage in a bar environment.
As a result of faults activing, formation of horst-graben structure and supergene processes in the region, ore minerals occur as non-sulfide (hemimorphite, cerussite, and wulfenite) and small amount of sulfides such as galena, sphalerite, wurtzite and pyrite. Fluorite, celestite and gypsum are also present in a minor amount. The lack of copper and silver is a significant characteristic of this deposit.
Characteristics features of Ahmad-Abad ore deposit, including carbonate host rock, disseminated and laminated texture, lens-type geometry parallel to bedding, predominance of Zn over Pb, lack of igneous bodies, lack of Cu-Ag mineralization, indicate that the deposit formed in a situation and condition similar to Bleiberg Zn-Pb (-Mo) deposit in Austria.
Keywords
(Iran) Beith. Geol. Jahb. Vol:51.
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