MINERALOGY, FLUID INCLUSION MICROTHERMOMETRY, AND THE GENESIS OF ORE-BEARING FLUIDS IN THE WEST OF QALEH-ZARI (CU-AU-AG MINE) ANOMALY ZONE, KUDKAN MINERALIZATION, KHORASAN, IRAN

Sakineh Amraei Shojaodin niroomand

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Abstract:

The Kudkan mineralization is one of the promising areas for Cu-Mo porphyry and related epithermal mineralization in north part of Lut Block in the Central Iran. Based on surficial geochemical studies in this area, there are four anomalous zones. The most important zone is zone 1 that is located in the west of Qaleh-zari mine. In this district gold, silver, and base-metal mineralization occurs in breccia and veins associated with Tertiary volcanic host (andesitic, trachyandesitic, basaltic andesite and related tuff) of Eocene age. Microthermometric measurements on quartz-hosted fluid inclusions indicate that mineralization formed between 109 - 429°C, from a weak to moderately saline hydrothermal fluid (0.2–9.7wt. %NaCl equiv). First ice-melting temperatures were determined to be between (−0.2 and−6.3 °C) indicate that the fluids mostly contained NaCl and KCl. Coexisting liquid-rich and vapor-rich fluid inclusions in quartz provide evidence for boiling in ore-stage breccia and veins, consistent with the presence of hydrothermal breccia and chalcedonic quartz. Metal (base and likely precious) deposition in this zone is inferred to have been largely caused by boiling, although fluid mixing and/or wall rock reactions may also have occurred. After rising to a depth of between (1510- 189 m), the fluid boiled causing deposition of fine-grained quartz and sealing of the hydrothermal conduit. Episodic boiling in response to alternating silica sealing and hydraulic brecciation was responsible for ore deposition. Pressure for mineralization is estimated to be between <20- 350 bar, with a density of fluids of 0.86 -0.91 g/cm3. Main alteration types consist of sericitization, argillization, and silicification. Hydrothermal alteration zones are well-developed and zoned around mineralized veins and host rocks with abundant sulfide. Metals may have precipitated due to the destabilization of bisulfide and chloride complexes, caused by boiling-off of H2S to vapor, whereas the dilution and/or cooling of hydrothermal fluids led to the precipitation of base metals. Results show that the source of mineralization is mixed magmatic-meteoric fluids and thus represents later stages of hydrothermal activity. Mineralization in this district are low to intermediate sulfidation systems, rich in Cu-As-Pb-Zn-Fe-S and locally Au-Ag assemblages related to intrusive Cu-Mo bodies postulated at depth.

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Breccia

Ore genesis

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Geological and Geochemical Analysis

Geochemistry and Geologic Mapping

Mineralogy and Gemology Studies

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Fluid inclusion and stable isotope constraints on ore genesis of the Zajkan epithermal base metal deposit, Tarom–Hashtjin metallogenic belt, NW Iran

Ore Geology Reviews (2019)

Hossein Kouhestani Mir Ali Asghar Mokhtari Kezhang Qin Junxing Zhao

Sericite

Magmatic water

Sulfide Minerals

Breccia

10.1016/j.oregeorev.2019.05.014

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Citations (28)

Hydrothermal alteration, mineralization and fluid inclusions in the Pista and Fofão prospects: implications for the genetic model of the Coringa polymetallic deposit, SE Tapajós Mineral Province, Amazonian Craton, Brazil

Journal of the Geological Survey of Brazil (2020)

Rafael Guimarães Corrêa Lima Evandro Luiz Klein

Pista and Fofao are prospects located near the main orebodies of the Coringa polymetallic deposit, in southeastern Tapajos Mineral Province of the Amazonian Craton. In both prospects, the mineralization is hosted in an Orosirian alkali feldspar granite, which is associated with coeval volcanic rocks at Pista. The paleo-hydrothermal system comprises an early post-magmatic stage, characterized by albite and K-feldspar alterations. Silicified and brecciated zones, sericitization of wall-rocks, both with adularia, as well as carbonatization (siderite and Mn-siderite rich stage) are the proximal ore alteration zones. Chlorite – hematite – rutile – epidote veinlets represent weak and distal zones of hydrothermal alteration. The mineralization is polymetallic (Au and subordinate Ag, Zn, Pb, and Cu) and occurs as dissemination and filling fissure veinlets. Gold occurs predominantly as Au-Ag-tellurides included in pyrite, and as free gold in association with pyrite, sphalerite and hematite within quartz veinlets. Fluid inclusions trapped in quartz veinlets show H2O, H2O-CO2-NaCl and CO2-only inclusions. Microthermometric data indicate an H2O-CO2-NaCl fluid, likely of magmatic derivation, with low-salinity (5.4 ± 1.3 wt. % NaCl equiv.) and moderate density (0.36-0.94 g/cm3) trapped between 264 and 370oC, and a low-salinity aqueous fluid (≤11.2 wt % NaCl equiv.) trapped at 280 to 360oC, possibly evolved from effervescence followed by isothermal mixing with an external heated H2O-NaCl fluid, probably meteoric. After this, the fluids were continuously diluted and cooled. This stage is represented by the liquid-rich H2O-NaCl fluid inclusions of low salinity (up to 5.3 wt. % NaCl equiv.) and relatively low trappingtemperature (177 to 113°C). The petrographic and fluid inclusions data suggest that the Au, Ag and base metals precipitation resulted from fluid mixing and dilution, which led to the breakdown of Au(HS)2−. We interpret the Pista and Fofao prospects as part of a magmatic-hydrothermal mineralized system, with some characteristics compatible with those of low- to intermediate-sulfidation epithermal systems, despite the absence of some typical textures from these systems.

Chalcedony

Ankerite

Paragenesis

Tourmaline

10.29396/jgsb.2020.v3.n1.3

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Timing and genesis of ore formation in the Qarachilar Cu-Mo-Au deposit, Ahar-Arasbaran metallogenic zone, NW Iran: Evidence from geology, fluid inclusions, O–S isotopes and Re–Os geochronology

Ore Geology Reviews (2018)

Hossein Kouhestani Mir Ali Asghar Mokhtari Zhaoshan Chang Holly J. Stein Craig A. Johnson

Molybdenite

Magmatic water