Genesis of Harizha Ag–Pb–Zn deposit in the eastern Kunlun Orogen, NW China: Evidence of fluid inclusions and C–H–O–S–Pb isotopes

Abstract

The Harizha Ag–Pb–Zn deposit is located in the eastern part of the eastern Kunlun Orogen, NW China. Two episodes including five paragenetic stages of vein mineralization has been recognized for the Harizha Ag–Pb–Zn deposit through petrographic observation: quartz + pyrite + arsenopyrite (Stage I), quartz + pyrite + chalcopyrite + pyrrhotite (Stage II), quartz + pyrite + chalcocite + pyrrhotite + sphalerite + galena + pyrargyrite (Stage III), quartz + calcite + pyrite + tetrahedrite + pyrolusite (Stage IV), and calcite + covellite + malachite + goethite + graphite (Stage V). In the quartz or calcite three types of fluid inclusions (FIs) were identified: L‐type, C‐type, and S‐type. The S‐type inclusions are only found in quartz in the wall rocks. The C‐type inclusions occur in quartz from early episodes (Stage I and II). The FIs from the early episodes homogenized at 240–320°C, with salinities of 9–12 wt.% NaCl equivalent. The ore‐forming fluids at the early episodes belong to an H2O–CO2–CH4–NaCl system. The FIs from late episodes (Stage III and IV) homogenized at 140–240°C, with salinities of 2–8 wt% NaCl equivalent. The ore‐forming fluids from the late episodes are dominated by an H2O–NaCl fluid system. The HO and CO isotopic compositions of quartz and calcite indicate that the ore‐forming fluids were derived from a primary magmatic‐hydrothermal system, with subsequent meteoric water involvement at a later stage. Sulfides have δ34S values of −3.7 to –1.0‰, and 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios ranging from 18.381 to 18.425, 15.661 to 15.683, and 38.498 to 38.677, respectively. These likely suggest a magmatic sulfur affinity combined with the ore features, mineral associations, alteration characteristics, ore‐forming environment, and fluid evolutionary process. We conclude that the Harizha Ag–Pb–Zn deposit is a typical medium‐low temperature hydrothermal deposit.