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

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.

Keywords


Epithermal; low sulfidation; Fluid inclusions; Qaleh-Zari; Iran

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References


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