Surface and sub-surface studies on geology and characteristics of ore-forming fluids in the Niaz porphyry copper prospect, west of Meshginshahr

Document Type : علمی -پژوهشی

Authors

Earth Sciences Department, University of Tabriz

Abstract

The Niaz copper prospect is located in west of Meshginshahr, east of Gharehdagh mineralization zone. The lithologic units in this area include intermediate igneous sub-volcanic (granodiorite, quartz monzonite, quartz monzo-diorite) and pyroclastic rocks. In terms of magmatic series, the igneous units in this area have high-K calc-alkaline to shoshonitic characteristics. Tectonically, the igneous units in this area lie in collision (subduction) particularly post-collision zone. Based upon mineralogy and paragenetic sequence, at least five types of veinlets (A, B, C, D, and E) are recognizable in surface and subsurface rock samples at Niaz. The hypogene alterations at Niaz include potassic, propylitic, phyllic, and argillic types. The hypogene mineralization occurred as dissemination, veinlet, stockwork, and brecciation. The hypogene opaque mineral assemblage includes chalcopyrite, pyrite, molybdenite, and lesser amounts of galena, sphalerite, bornite, and magnetite which formed during at least three stages. The principal supergene mineral assemblage includes iron oxy-hydroxides, malachite, azurite, and tenorite in the oxidized zone and covellite and chalcocite in the reduced zone. Studies on fluid inclusions (FI) within the quartz crystals showed that there are four types of FI in room temperature, (1) mono-phase vapor, (2) liquid-rich 2-phase, (3) vapor-rich 2-phase, and (4) multi-phase solid containing daughter solid phases (chiefly halite and hematite) in the Niaz area. The homogenization temperatures (Th) of the studied  multi-phase solid and 2-phase FI have  240-540°C and 170-530°C range, respectively. The Th range of FI in the potassic, propylitic, and argillic alteration zones are 180-500°C, 180-560°C, and 170-330°C, respectively.

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