Genesis of Hg-Sb deposit controlled by strike-slip structures in Qinling orogenic belt: A case study of the Qingtonggou ore deposit, Shaanxi, China

Abstract

The Qingtonggou deposit is the largest Hg-Sb deposit in the Qinling orogenic belt, but the deposit genesis remains unclear. Fluid inclusion study indicates that the homogenization temperature range from 139.9 °C to 217 °C and the salinities vary from 0.7 to 2.1 wt% (NaCleq). The δ13C value in ore-stage calcite is from-7.6 ‰ to −7.1 ‰, and the δ18OSMOW value is between 13.6 ‰ and 15.3 ‰. The δ18OV-SMOW value in hydrothermal quartz is from 21.5 ‰ to 24.8 ‰, and the δD value is between −138 ‰ to −99 ‰. The δ34SV-CDT value range from 4 ‰ to 11.6 ‰, the 206Pb/204Pb values range from 18.0351 to 18.5080, the 207Pb/204Pb values range from 15.6390 to 15.6672, and the 208Pb/204Pb values range from 38.1586 to 38.4128. The hydrothermal calcite Sm-Nd isochron age for ore-stage calcite is 98.02 ± 0.42 Ma. The Hg-Sb mineralization is controlled by tectonic space formed by the left strike-slip fault, the ore-forming fluid has the characteristics of medium–low temperature, low density, and supergene mineralization, the ore-forming fluid comes from meteoric water and formation water, the ore-forming material comes from the stratum and basement of Yaolinghe group and Lower Cambrian, the Hg-Sb mineralization occurred at early Late Cretaceous. The complete metallogenic process is that the Yaolinghe Group and Lower Cambrian in this area are the source areas for Hg-Sb mineralization, the subsequent high background values Hg and Sb strata which received the denudation deposit of the source bed all contributed ore-forming materials, with the Qinling collision orogeny and extrusion in the Indosinian period and the continuous contraction of the Paleozoic basin, porous meteoric water and formation water extracted the ore-forming materials in source bed, formed ore-forming fluids, during the strike-slip process in intracontinental environment, deep and large faults provide a channel for the upward discharge of ore-forming fluids, with the decrease of fluid temperature, sulfide precipitation occurs in secondary fracture.