Geological characteristics and enrichment mechanisms of the Huayagou-Jinchanggou Au Deposit: Implications for ore genesis in the Baguamiao-Jiutiaogou anomaly belt

Abstract

Significant breakthroughs have recently been made in the Huayagou-Jinchanggou area of the Western Qinling Orogen (WQO), with estimated Au reserves of 20 t. However, the genetic relationship between magmatism and mineralization, as well as the mechanisms responsible for ore enrichment, remain unresolved. The Jinchanggou Au deposit, characterized by super-rich ores and multiphase magmatism, provides a valuable opportunity to clarify these issues. In this study, we investigated mineralization-related diorite dykes through zircon LA-ICP-MS U-Pb dating, mineralogical geochemistry, EPMA analyses, and elemental mapping of bismuth minerals in auriferous quartz veins. The results show that the diorite dyke was emplaced at ca. 211.8 Ma and is characterized by moderately high oxygen fugacity and water content, consistent with magma mixing as indicated by the abundance of acicular apatite. Multiple episodes of such intrusions released magmatic-hydrothermal fluids that contributed to gold enrichment. The quartz-vein-type ores at Jinchanggou, particularly late-stage gently dipping veins, differ from the regionally common disseminated-type ores and display features of orogenic gold systems with a magmatic-hydrothermal overprint, comparable to deposits such as Val-d’Or (Canada) and Shuangqishan (China). Combined with geophysical and metallogenic data, these features suggest that mineralization is linked to Yanshanian metallogeny, a rare event in the WQO. This study provides new evidence for multi-pulsed magmatic contributions to mineralization and highlights the potential for deeper mafic dyke-related gold mineralization along the Baguamiao-Jiutiaogou anomaly belt.