Gold Occurrence of the Micro-Disseminated Gold Deposits in Zhen’an-Xunyang Basin, South Qinling Orogenic Belt

Objective‌ The Zhen’an-Xunyang basin, an Early Paleozoic rifted basin situated in the central part of the South Qinling tectonic belt, has seen the discovery of several disseminated gold deposits, like Xiaohe, Huijiagou, and Wangzhuang in recent years. Understanding the occurrence state of gold in these deposits is crucial for uncovering the regional gold mineralization enrichment mechanism.

Methods This study focuses on two fine-disseminated gold deposits, Wangzhuang and Laojunmiao, by carrying out the systematic microscopic identification and EPMA analysis.

Results and Conclusion These gold deposits exhibit low-grade and metallic sulfide-hosted mineralization. Three types of pyrite closely associated with gold mineralization are identified in the region: arsenic-free pyrite (Py1, Py2), arsenic-bearing pyrite (arsenopyrite) (Py3, Apy), and arsenic-poor pyrite (Py4), with gold enrichment mainly observed after Py2. The Co/Ni ratios of the ore-forming pyrite during the mineralization period typically fall between 1 to 10, indicating a hydrothermal origin linked to the influx of arsenic-bearing hydrothermal fluids. Furthermore, based on the Au-As relationship, it is tentatively suggested that gold elements in the fine-disseminated gold deposits in the area are primarily present in lattice gold form within pyrite and arsenopyrite.