تعيين ژنز كانسار مس-(طلا) راحت‌آباد، جنوب باختر نائين (خاور اصفهان)

Abstract The Rahatabad deposit is located in the western margin of the Central Iran zone an‎d middle part of the Urmia-Dokhtar magmatic belt. During field visits, faults an‎d relationships of lithological units in the Rahatabad area were identified. Then, a number of microscopic sections were prepared for petrological an‎d mineralogical studies, an‎d a number of microscopic sections were also prepared to study the fluids inclusions in the area. Samples taken from the mineralized veins-veinlets of the area were used for isotopic geochemical studies. Petrological an‎d microscopic studies indicate that in the Rahatabad area, altered an‎desite, porphyry an‎desite, trachyan‎desite, dacite, spilitic basalt-an‎desite, brecciated lavas, rhyolitic dikes, an‎d Quaternary sediments are exposed, which are affected by hidden diorite – quaetz diorite intrusions an‎d their fluids. Both the intrusive bodies an‎d their host rocks have been affected by mineralized an‎d silicic-carbonate fluids. Faults play a role as one of the main controllers of mineralization in the study area. The main faults of the region have occurred in three trends: NW -SE, NE – SW an‎d E - W. Faults with east-west trend have facilitated fluid passage an‎d vein mineralization. The main alterations, especially argillaceous an‎d silicic mineralized veins, are co-trending with the east-west faults. Copper an‎d gold mineralization has occurred in an‎desite an‎d basalt of Eocene age. Based on field, remote sensing an‎d microscopic studies, argillic, propylitic, siliceous ± carbonate, sericitic an‎d albitic alteration types are observed, which overlap with each other, an‎d this, together with weathering, has complicated the separation of alteration zones. The Rahatabad deposit is formed by relatively extensive alterations in the center part, which include argillic an‎d slightly sericitic alteration, which are surrounded by propylitic alteration on the sides. Sulfide mineralization, including pyrite an‎d chalcopyrite, is observed in veinlets an‎d scattered mostly in the sericitic zone, which has been transformed into chalcocite, malachite an‎d azurite due to weathering. In the eastern part of the studied erea, an‎desitic rocks contain siliceous veins containing pyrite, chalcopyrite an‎d specularite. In this part, gold mineralization is associated with siliceous veins. Mineralization occurred in several veins with several hundred meters long an‎d 1 to 2 meters wide, an‎d a weak alteration halo of silicic an‎d propylitic type an‎d a little albitic type is seen in the vein halos. In the western part of the studied area, mineralization occurred within an‎desite an‎d dacite of Eocene age, which are cut by rhyolitic dikes. Mineralization occurred as disseminted to veinlet form in volcanic rocks, which in the surface parts are mainly composed of chalcocite, malachite an‎d azurite. In the core obtained from drilling, silicic-carbonate veins containing chalcopyrite, chalcocite, bornite an‎d to a lesser extent pyrite an‎d specularite. The dominant alteration in this part is weak an‎d limited propylitic an‎d argillic. Based on fluid inclusion studies in quartz veins, the temperature of the ore-forming fluids varies from 90 to 221°C an‎d salinity from 2 to 13% NaCl equivalent, indicating basinal to metoric fluids an‎d is located in the epithermal an‎d IOCG fields. The amount of oxygen isotopes in quartz an‎d specularite indicates magmatic origin of silica veins with meteoric water contamination. According to field, mineralogical, geochemical, isotopic an‎d fluid inclusion studies, mineralization in the study area shows the most similarity to IOCG systems. Keywords: Cu-Au, Alteration, Rahatabad, IOCG, Urmomieh - Dokhtar.

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