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Hossein Kouhestani

Hossein Kouhestani, Mir Ali Asghar Mokhtari, Zhaoshan Chang
Fluid inclusion and stable isotope constraints on the genesis of epithermal base metal veins in the Armaqan Khaneh mining district, Tarom–Hashtjin metallogenic belt, NW Iran
Abstract


Rashtabad, Aqkand, and Jalilabad are neighbouring epithermal base-metal deposits in the Armaqan Khaneh mining district (AKMD) of the Tarom-Hashtjin metallogenic belt (THMB), northwestern Iran. Mineralised veins in these deposits consist of pyrite, chalcopyrite, galena, sphalerite with lesser bornite and minor amounts of specular hematite. The gangue mineralogy includes quartz, chlorite, and calcite in ore veins and sericite/illite, and sericite–epidote–chlorite–calcite in vein haloes. At Rashtabad and Jalilabad, primary LV fluid inclusion assemblages homogenise into liquid at 150–285 °C and 120–342 °C, respectively. The corresponding salinities, respectively, vary between 7.4–12.9 and 7.8–13.5 wt% NaCl equiv. At Aqkand, LV inclusions show Th(total) of 229–353 °C and salinities of 7.4–9.8 wt% NaCl equiv. Calculated δ18Owater values of quartz samples at Rashtabad, Aqkand, and Jalilabad are +9.6‰ to +1.0‰ VSMOW, signifying that the ore-forming fluid progressed from magmatic to meteoric water. Sulfur isotopic values of sulfides range from –6.0‰ to –2.2‰ VCDT (averaging −3.7‰),indicate sulfur was derived from a rather homogeneous magmatic source that was oxidised by meteoric water through fluid mixing. Our data suggest that Rashtabad, Aqkand, and Jalilabad are intermediate-sulfidation type of epithermal mineralisation formed from a well-mixed source that experienced extensive fluid mixing and boiling.

 

 

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