A Discussion on the Two‐stage Mineralization of the Baguamiao ‐Shuangwang Gold Orefield, Shaanxi Province, China

Abstract  The gold orefield studied is located on the south border of the underthrust‐collision zone of the Qinling microplate and the North China microplate in the Indosinian epoch. The main ore deposits localized in the area where the WNW‐trending compression‐shear type fault of the Indosinian epoch intersected the NE‐trending tenso‐shear type fault of the Yanshanian epoch. The orebody appeared in a chambered or wedged form. The mineral composition is relatively complex. On the southeastern border of the orefield there have developed intermediate‐acid anatectic magmatites of the Mesozoic Era. Three‐phase inclusions (Lco2, Vco2 and LNaCl‐H2O) comprise over 50%, associated with vapor phase consisting of H2O, CO2, CO, CH4, N2 and H2. The ore‐forming fluids can be divided into 2 stages (the early and the late). The samples are projected in the area of mixture of initial magmatic and meteoric water on the δD‐δ18O diagram, suggesting two types of mineralization, i.e. the re‐equilibrated magmatic‐hydrothermal type and the circulating geothermal water type of a meteoric water source. The mineralization occurring in this orefield might be a superimposition of 2 tectono‐magmatic activities (the Indosinian and Yanshanian movements). Therefore, it is considered a superimposed B‐S type gold orefield.