Authors
1
Department of Geology, Faculty of Sciences, University of Zanjan
2
Department of Geology, University of Zanjan
Abstract
The Ipak polymetal deposit is located about 14 km south of Eshtehard (Alborz province) and is part of the Mardabad-Bouinzahra volcanic belt. Mineralization occurred as silica-sulfide zones (N90E/60-70N) hosted by early-middle Eocene tuff and lava units and has a close spatial relationship with the middle Eocene quartz monzodiorite-pyroxene quartz monzodiorite intrusion. The main ore zone is about 1 kilometer in length and up to 2 meters in thickness and is covered by a 3-to-0-meters1 intermediate argillic alteration halo. Pyrite, chalcopyrite, galena, sphalerite, pyrolusite, psilomelane, quartz, barite, calcite, and sericite-illite are the ore-forming minerals in the Ipak deposit. Cerussite, smithsonite, malachite, chalcocite, and goethite are formed during supergene processes. The ore minerals show disseminated, vein-veinlets, brecciated, crustiform, colloform, cockade, plumose, bladed, relict, vug infill, and replacement textures. Six stages of mineralization can be distinguished at Ipak, where Cu, Pb, and Zn mineralization occurred as quartz-pyrite-chalcopyrite-galena-sphalerite veins and breccias in the second stage. Hydrothermal alteration comprises silicification, carbonate, intermediate argillic, and propylitic alteration. Chondrite–normalized trace elements and REE patterns of ore samples, quartz monzodiorite intrusion, and host rocks (crystal tuff, and basaltic andesite lava) are comparable. This specifies that alteration and leaching of elements from the host volcanic rocks are involved in mineralization. Characteristics of the Ipak polymetal deposit are similar to the intermediate-sulfidation type of epithermal deposits.
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