地质样品Ce4+/Ce3+比值分析及其应用：以藏东玉龙斑岩铜矿为例研究岩浆相对氧化还原状态与斑岩矿床形成关系

现有研究表明，斑岩型Cu-Au(Mo)矿床有关岩浆多为高氧逸度岩浆，但直接反映岩浆相对氧化还原状态的岩浆岩和岩浆锆石Ce4+/Ce3+比值的测定方法还未见报道。本项目将以抗物理化学风化的岩浆锆石为代表物，通过实测锆石Ce4+/Ce3+比值，分析岩浆的相对氧化还原状态。基于Ce4+和Ce3+的不同化学行为，采用溶剂萃取或无机共沉淀手段，在HNO3/H2SO4介质中，实验分离Ce4+和Ce3+，建立实测地质样品Ce4+和Ce3+的分析方法。并以藏东玉龙斑岩铜矿为研究对象，测定其岩浆岩、锆石中的Ce4+和Ce3+含量，获得实测Ce4+/Ce3+比值。对比玉龙斑岩铜矿富矿岩体和贫矿岩体锆石Ce4+/Ce3+比值，分析岩浆氧逸度高低与斑岩铜矿形成关系，建立成矿岩体指标，提供找矿理论，指导找矿实践。

Previous studies have revealed the formation of porphyry Cu-Au(Mo) deposits is related to the magmas with high oxygen fugacity. As a redox indicator, however, the Ce4+/Ce3+ ratios in magmatic rock and zircon have not been directly determined. In this study, zircon as an ideal proxy for resistant to hydrothermal alteration and physical/chemical weathering will be determined for its Ce4+/Ce3+ ratio and be employed for investigating the relative oxidation states of magmas. According to the different behaviors between Ce4+ and Ce3+, experiments will be carried out for their separation in HNO3/H2SO4 medium, developing a method for determination of Ce4+and Ce3+ in geological samples. This method will be applied to Yulong porphyry copper deposits in eastern Tibet, the concentration of Ce4+ and Ce3+ in zircon and magmatic rocks will be determined, and Ce4+/Ce3+ ratio also will be obtained. The Ce4+/Ce3+ ratios in zircon compared between ore-bearing porphyry and barren porphyry will give an insight into a relationship of magmatic oxygen fugacity with the formation of porphyry copper deposits for establishing mineralization index for porphyry, providing scientific basis for exploration of ores and guiding exploration of ores in practice.