Fluid Inclusions of Orogenic Gold Deposits in the Zhongchuan Area, Western Qinling and Their Geological Significance

摘要

Orogenically-derived gold deposits of the Zhongchuan area in the western Qinling are distributed in the exocontact thermal metamorphic zone. The country rocks hosting the deposits are predominantly of Devonian age with low-grade metamorphism and strong deformation with the ore deposits directly controlled by multi-level tectonic systems. Three types of inclusions from these deposits have been recognized: CO_2-H_2O, CO_2-rich, and aqueous. The ore-forming fluids were mainly CO_2-NaCl-H_2O type characterized by rich CO_2, low salinity, high temperature and immiscibility. Incorporated with earlier isotopic data, the regional geological setting and features of diagenesis and metallogeny, it can be concluded that the ore-forming fluids were derived from deep magma and mixed with meteoric and metamorphic water. The deposits formed during an intra-continent collisional orogeny, and some of the materials derived from the deep might have been involved in the ore-forming process.