Carbon dioxide-dominated fluids and relationship with mineralization

二氧化碳是地壳中流体的一种常见成分。一般来说，它的丰度比H2O低得多，但在包括矿藏在内的某些地质环境中，它可能会变得比H2O更富有并变得更重要。某些类型的矿化，特别是在造山过程中形成的金矿(称为造山型金矿)，几乎总是与富含二氧化碳的流体有关。这种金属-二氧化碳结合的性质还不是很清楚，因为二氧化碳不是一种很好的金属运输剂。在其他矿藏中也发现了富含二氧化碳的流体，包括稀有金属(锡、钨)和贱金属(铜、锌、铅)矿床。在拟议的研究中，我们通过研究两个大型采矿营地-红湖金矿区(安大略省西部)和兰坪贱金属区(云南省，中国)的流体包裹体来解决金属-二氧化碳组合问题。流体包裹体是包裹在矿物中的微小(几微米)液滴，代表与成矿有关的古老流体。世界级金贝尔-红湖金矿床流体包裹体具有特殊性，主要由CO2组成，不含H2O。兰坪金顶超大型铅锌矿床还含有以二氧化碳为主的流体包裹体。据信，在坎贝尔红湖和金顶矿床的形成过程中，以二氧化碳为主的贫水流体分别负责大量金和锌的输送。我们计划对以二氧化碳为主的流体包裹体进行详细的地球化学研究，旨在揭示二氧化碳与金和一些贱金属矿床的相互作用机制。这项研究涉及使用各种分析技术测量流体包裹体中的挥发物和溶质。将进行高压-高温实验，以评估金和贱金属在以二氧化碳为主的流体中是如何运输的。研究成果将对成矿理论有所贡献，有助于矿产勘查。

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.