| چکیده انگلیسی مقاله |
The Aregijeh and Emarat Pb-Zn deposits are hosted by clastic-carbonate sequences of the Early Cretaceous in south Arak. These deposits formed in the northern Sanandaj-Sirjan zone within an intracontinental rift setting. The main stratabound Pb-Zn mineralization horizon occurs in the upper part of thick-bedded Orbitolina-bearing limestones (Aptian-Albian), underlying shales and marls with intercalated thin-bedded limestones. Mineralization appears as banded, brecciated, laminated, veined, and disseminated comprising sphalerite, galena, and pyrite, with minor chalcopyrite, and Ag-Sb-Cu sulfosalts, accompanied by quartz, dolomite, calcite, barite, and siderite as gangue minerals. Silicification and carbonatization represent the dominant alteration types. The unusual abundance of fine-grained quartz, anhedral dolomite, and framboidal pyrite provides evidence of early diagenetic stages, while mineralization was completed by the precipitation of coarse-grained quartz, euhedral dolomite, siderite, and hydrothermal sulfides. Ore formation occurred in a submarine anoxic environment shortly after sedimentation. Microthermometric results of fluid inclusions reveal similar homogenization temperature ranges (125–207°C in Aregijeh vs. 130–217°C in Emarat) in both deposits. However, calculated salinities (7.59–13.72 wt.% NaCl equiv. in Aregijeh vs. 7.59–19.84 wt.% NaCl equiv. in Emarat) are higher in the Emarat deposit. Textural relationships, mineralogical properties, and fluid inclusion data suggest mineralization formed from basinal brines during diagenesis in a reduced environment, consistent with Irish-type deposits.
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