Source of ore Forming Materials and Genesis of Zhupogou Gold Deposit in West Qinling Mountains

Zhupogou gold deposit is located at the turning end of the anti "s" shaped structure of the Yuanyang town Guanzi town Ophiolitic Melange belt in the north of the West Qinling Mountains. The gold deposit is hosted in the early Paleozoic Liziyuan group. The occurrence of the ore body is controlled by NW and NE trending ductile faults and their secondary structures, and the shape of the ore body is vein. The inclusions in quartz in the main metallogenic stage of the hydrothermal period of the deposit are mainly gas-liquid two-phase inclusions and three-phase inclusions containing daughter crystals. The freezing point temperature range of three-phase inclusions containing daughter crystals is −4.8～−4.3 ℃; The freezing point temperature of gas-liquid two-phase inclusions ranges from −5.3 to −0.1 ℃. At this stage, the homogenization temperature of three-phase inclusions containing daughter crystals is in the range of 141.3～198.6 ℃, with an average of 160.7 ℃; The gas-liquid two-phase inclusions are in the range of 128.9～285.3 ℃, with an average of 174.1 ℃. The homogenization temperature of ore-forming fluid is 130～170 ℃, and the peak range is wide. Fluid salinity is 1.40%～8.28% Nacleqv, average 5.84% NaCleqv. It has the characteristics of medium low temperature and low salinity; quartz δ¹⁸O_H2O is −3.29‰～4.42‰, δD is −110.1‰～−86.6‰, and the ore-forming fluid comes from primary magma water. In the process of magmatic differentiation and mineralization, the content of atmospheric precipitation gradually increases. Pyrite and arsenopyrite in the main metallogenic stage δ³⁴S value is 10.7‰～11.5‰, and the minerals are derived from magmatic rocks and strata respectively; Pb isotopic composition is similar, mainly from the orogenic belt, with some upper crust lead and mantle lead added. The metallogenic material comes from the two end elements of magmatic rock and stratum. Comprehensive analysis shows that the genetic type of Zhupogou gold deposit belongs to the tectonic altered rock type gold deposit of sedimentary metamorphism post magmatic hydrothermal superimposition.