花岗岩熔体中钛铁矿的溶解度和微量元素分配实验研究：了解花岗岩和金属矿床形成机制的新工具

钛铁矿是火成岩和变质岩中常见的副矿物, 具有复杂的化学组成，含较多微量元素(Mn，Cr，Mg，W，Sn，Mo，Zn，Nb，Ta，U，V)。钛铁矿的结晶会影响花岗岩中微量元素的行为及其形成稀有金属矿床的能力, 但至今我们仍缺乏关于钛铁矿在熔体中的溶解度，组成和微量元素分配系数等的可靠数据，尤其是对于花岗岩熔体。为此，本项目旨在通过开展一系列与花岗岩岩浆形成和结晶有关条件下钛铁矿的溶解和合成实验，对痕量元素分配至钛铁矿及其在花岗岩体系中的溶解度进行全面的实验研究。由于钛铁矿包含多种对氧逸度敏感的元素，因此实验的氧化还原条件将通过缓冲液组合进行控制，并使用钛铁矿的独特特性作为”氧压计” 来估算。本项目将通过现代分析技术（例如电子探针和LA-ICP-MS）分析实验合成产物，并将其用于建立钛铁矿的溶解度和微量元素分配模型。研究结果将增进我们对地壳岩浆分异作用和对经济至关重要的多种类型矿床形成的理解。

Ilmenite is one of the most common accessory minerals in wide range of igneous and metamorphic rocks. It has complex composition with dominant solid solutions between ilmenite (FeTiO3) and hematite (Fe2O3) and contains many trace elements including Mn, Cr, Mg, W, Sn, Mo, Zn, Nb, Ta, U, V and others. Deposits of ilmenite are important sources of Fe, Ti, V and Cr in China and worldwide. Crystallisation of ilmenite affects behaviour of trace elements in granitic rocks and their ability to form rare metal deposits. Despite the importance of ilmenite, reliable data on its solubility in melts, composition and trace element partitioning into ilmenite are absent, especially for granitic liquids. This project aims to conduct a comprehensive experimental study of trace element partitioning into ilmenite and its solubility in granitic systems by conducting ilmenite dissolution and synthesis experiments over range of conditions relevant for formation and crystallisation of granitic magmas. As ilmenite contains several elements sensitive to oxygen fugacity, the redox conditions of the experiments will be controlled by buffer assemblages and estimated using unique properties of ilmenite as oxybarometer. The experimental charges will be analysed by modern analytical techniques such as microprobe and LA-ICP-MS and used for development of models for solubility and partitioning of ilmenite. The results of the study will advance our understanding of crustal fractionation and formation of multiple ore deposit types crucial for economy.