Geological characteristics, fluid inclusion, and isotope systematics of the Zhongshangou gold deposit, northern margin of the North China Craton: A comparative study with the Dongping deposit and implications for regional mineralization

Abstract

The Zhongshangou deposit, located in the Zhang-Xuan ore concentration area, Hebei Province, China, is a representative Te-rich gold deposit related to alkaline intrusion. For the purpose of revealing the ore-forming characteristics, a comprehensive study was conducted on the ore deposit geology, fluid inclusions, laser Raman spectroscopy, and isotopes of H, O, C, S, and Pb. Fluid inclusion data and laser Raman spectroscopy indicate that the fluids responsible for Au–Te mineralization belong to a H₂O-CO₂-NaCl system, characterized by medium temperatures and low salinities. The hydrogen (δD = −98.1 ‰ to −78.7 ‰) and oxygen (δ¹⁸O_SMOW = −7.5 ‰ to 12.5 ‰) data suggest that the ore fluids of Zhongshangou were originally magmatic sourced. The δ¹³C_V-PDB values of calcite samples (0.7 ‰ to 1.9 ‰) overlap with those of igneous carbon, and the δ¹³C_V-PDB values of CO₂ extracted from fluid inclusions also show similar characteristics to mantle-derived fluids (−16.9 ‰ to −13.2 ‰). The δ³⁴S values of mineralization-associated sulfides have a large range of variations (−19.1 ‰ to −5.3 ‰), implying that the physical and chemical conditions for mineralization have undergone drastic changes. These abrupt fluctuations in ore-forming geochemistry are conducive to anomalous gold enrichment and its coexistence with tellurium. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of mineralization-associated sulfides are 17.24 to 18.08, 15.42 to 15.64, and 37.17 to 38.55, respectively, overlapping with those of deeply sourced alkaline rocks. Similar ore-hosting rocks, mineral assemblages, fluid inclusion types, and comparable stable isotope compositions suggest that the Dongping and Zhongshangou deposits have a common origin and formed in a simultaneous magmatic hydrothermal system.