Carbon dioxide-dominated fluids and relationship with mineralization

二氧化碳是地壳中流体的常见成分。它通常比H2O少得多，但在某些地质环境中，包括矿床，它可能会富集并变得比H2O更重要。某些类型的矿化，特别是造山过程中形成的金矿床（称为造山型金矿床），几乎总是与富CO2流体有关。这种金属-CO2缔合的性质还没有很好地理解，因为CO2不是一种良好的金属运输剂。在其他矿床中也发现了富CO2流体，包括稀有金属（Sn、W）和贱金属（Cu、Zn、Pb）矿床。在拟议的研究中，我们解决了金属-CO2协会的问题，通过研究流体包裹体从两个大的采矿营地，红湖金矿区（西部安大略）和兰坪基地金属区（云南省，中国）。流体包裹体是包裹在矿物中的微小（几微米）流体液滴，代表与成矿作用有关的古老流体。世界级坎贝尔-红湖金存款矿床的流体包裹体以CO2为主，未检出H2O，具有特殊性。兰坪金顶超大型锌铅存款矿床也含有以CO2为主的流体包裹体。贫H_2O、CO_2为主的流体分别在坎贝尔-红湖和金顶矿床的形成过程中搬运了大量的金和锌。我们计划开展详细的地球化学研究的CO2为主的流体包裹体，旨在揭示CO2与金和一些贱金属矿床之间的关联机制。该研究涉及使用各种分析技术测量流体包裹体中的挥发分和溶质。将进行高压-高温实验，以评估金和贱金属如何在CO2占主导地位的流体中迁移。研究成果将有助于成矿理论的发展，为矿产勘查提供理论依据。

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.