Geological Characteristics and Ore-Controlling Factors of the Shuidegou Gold Deposit in the Mianlue Tectonic Belt

The Mianlue tectonic belt, a crucial plate suture zone within the Qinling Orogen, hosts significant gold deposits. This study focuses on the newly discovered Shuidegou medium-sized gold deposit, systematically analyzing its geological features, ore quality, and ore-controlling factors to elucidate the differential mechanisms of tectonic-fluid coupling on gold mineralization. The orebodies are hosted in the Neoproterozoic Qiaozigou Volcanic Formation and belong to altered rock-type gold deposits. Gold occurs primarily as fracture-hosted grains in fragmented pentagonal dodecahedral pyrite, with high exposure rates and excellent metallurgical recoverability. High-grade mineralization is exclusively associated with silicification-pyritization-albitization assemblages, which represent the dominant ore-fluid type, whereas quartz lenses and chloritized zones exhibit low gold endowment. Tectonic controls vary distinctly with tectonic stages: early nearly EW-trending thrust shears govern the overall scale and distribution of main orebodies, forming thick, large-volume orebodies with low grades; in contrast, later NE-trending extensional-shear strike-slip faults overprint the earlier structures, wherein a sharp pressure drop triggers rapid gold precipitation and produces high-grade but small-scale orebodies. The metallogenetic evolution comprises two stages: Neoproterozoic volcanic-sedimentary pre-enrichment and Indosinian-Yanshanian tectono-magmatic superimposed main mineralization. Accordingly, three priority targets are proposed for further exploration: zones with superimposed silicification, albitization, and pentagonal dodecahedral pyritization within the Qiaozigou Formation; concealed EW-trending structures beneath NE-trending high-grade mineralization zones; and surface areas where limonitization coincides with geochemical gold anomalies. This alteration assemblage is identified as the key prospecting indicator.