铜在不混溶高硅熔体和成矿流体体系分配行为的实验岩石学研究

“小岩体成大矿”理论对斑岩铜矿成因的解释一直饱受争议，主要原因在于中酸性岩体规模小且含铜量低。深入研究表明岩浆晚期出溶流体以及熔体-流体分配行为，而非岩浆体系，控制了铜的溶解、萃取、活化和富集过程。然而现存研究对流体出溶时共存熔体成分变化存在明显不足，无法确定铜在高度演化的熔体中是否发生预富集，因而无法对铜在熔体-流体不混溶体系的分配行为进行科学判断。申请人拟采用实验岩石学方法模拟过渡阶段铜在熔体和流体相容性的变化，联合使用高温高压釜和人工合成包裹体技术，试图捕获并保存高温高压下共存的熔体和流体，拟利用电子探针、激光拉曼和激光剥蚀质谱仪分析熔体和流体成分，以期精确限定铜在共存熔体-流体两相间的分配系数，进而揭示中酸性岩浆演化晚期的成矿潜力与斑岩铜矿成因的联系。

The genetic relationship between small-scale granitic magma and large-tonnage porphyry Cu deposits has been strongly debated, mainly because these intermediate to felsic porphyritic intrusions are not usually rich in copper and are volumetrically small. More evidences show that fluid exsolution and fluid-melt partitioning, rather than magma itself, play a vital role in sequestering, transport and enrichment of copper. Fluid-melt unmixing is an inherently fugitive phenomenon and the transition from near magmatic solidus to hydrothermal fluids has proved extremely difficult to document and understand, largely because of the complicated, transient, reactive nature of melt and aqueous phases at this stage. It is worth noting that there is a lack of systematic study of melt composition variation along fluid exsolution at transition stage. Hence, it is not certain whether Cu can be concentrated in highly evolved melt, which could lead to spurious determination of Cu partitioning data. This research attempts to precisely determine Cu partitioning data between coexisting fluid and evolved melt phases. RH/RQ Ar-CSPV, IHPV and synthetic fluid inclusion technique are used to ensure the co-trapping of fluid as well as melt phases at run conditions. EMPA, LA-ICPMS and Raman spectroscopy are used to quantitively and qualitatively acquire the elemental compositions in corresponding phases. These data provide information about Cu partitioning, complexation and enrichment along the magmatic-hydrothermal processes. More importantly, Cu partitioning data is a key stone in understanding whether economic porphyry copper mineralization can be generated by intermediate to felsic magma, as well as in exploring potential metal repositories.