Carbon dioxide-dominated fluids and relationship with mineralization

点击翻译按钮获取中文摘要

CO2 is a common component of fluids in the earth's crust. It is generally much less abundant than H2O, but in some geologic environments including mineral deposits, it may be enriched and become more important than H2O. Certain types of mineralization, particularly gold deposits formed in mountain-building processes (called orogenic type gold deposits), are almost always associated with CO2-enriched fluids. The nature of such metal-CO2 association is not well understood because CO2 is not a good metal-transporting agent. CO2-enriched fluids have also been found in other mineral deposits, including rare metals (Sn, W) and base metals (Cu, Zn, Pb) deposits. In the proposed research, we tackle the metal-CO2 association problem by studying fluid inclusions from two large mining camps, the Red Lake gold district (western Ontario) and the Lanping base metal district (Yunnan Province, China). Fluid inclusions are tiny (a few microns) droplets of fluids entrapped in minerals and represent ancient fluids related to mineralization. The fluid inclusions in the world-class Campbell-Red Lake gold deposit are special because they are mainly composed of CO2, with no detectable H2O. The superlarge Jinding Zn-Pb deposit in the Lanping district also contains CO2-dominated fluid inclusions. The H2O-poor, CO2-dominated fluids are believed to be responsible for the transport of large amounts of gold and zinc in the formation of the Campbell-Red Lake and Jinding deposits, respectively. We plan to carry out detailed geochemical studies of the CO2-dominated fluid inclusions with an aim to unravel the mechanism of the association between CO2 and gold and some base metal deposits. The study involve measurements of volatiles and solutes in the fluid inclusions using various analytical techniques. High pressure - high temperature experiments will be done to evaluate how gold and base metals were transported in CO2-dominated fluids. The research results will contribute to mineralization theories, which can help mineral exploration.