攀西层状岩体成矿氧逸度研究

项目名称： 攀西层状岩体成矿氧逸度研究

项目编号： No.41473051

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 天文学、地球科学

项目作者： 陶琰

作者单位： 中国科学院地球化学研究所

项目金额： 95万元

中文摘要： 本项目以峨眉山大火成岩省攀西层状岩体岩浆演化及成矿过程氧逸度测算为重点，辅助开展氧逸度约束下的熔融实验研究。氧逸度测算包括层状岩体主要岩相带及矿层的各类岩矿石矿物组合，同时开展有关苦橄岩、玄武岩岩浆氧逸度测算，界定原始岩浆、成矿母岩浆及主要成矿阶段的岩浆氧逸度，分辨攀西地区氧逸度可能存在的区域性特色及原因。熔融实验以获得不同温度和氧逸度下钛铁氧化物饱和的液相线岩浆成分为目的，建立钛铁氧化物饱和状态下的液相线岩浆成分与温度、氧逸度的关系；利用温度和氧逸度的测算结果，对攀枝花岩体成矿母岩浆可能的组成进行评估、并讨论成矿岩浆的形成和演化。这些研究致力于探讨攀西层状岩体成矿机理研究中的3个突出问题：①攀西层状岩体是否为高氧逸度成矿；②攀西层状岩体成矿岩浆氧逸度是否具有宏观背景并对构成对区域性成矿作用的约束；③岩浆不混熔与成矿。其研究有助于攀西层状岩体成岩成矿理论研究的深入。

中文关键词： 钛铁氧化物矿床；氧逸度；攀西层状岩体；攀枝花；峨眉山大火成岩省

英文摘要： This project is to investigate the oxidation states during magma evolution and ore formation in the Fe-Ti-V oxide ore-bearing layered intrusions of the Panxi region, the Permian Emeishan Large Ignious Province, and to perform anhydrous one atmosphere melting experiments on the mixtures of ores and associated gabbros from the Panzhihua intrusion. The oxidation states of the magmatic systems will be determined using silicate and oxide mineral assemblages in the Permian layered intrusions in the Panxi region including Panzhihua, Hongge and Xinjie. The pre-eruption oxidation states of the coeval picrites and basalts, which are complientary to the studies of the intrusive rocks, will be determined using suitable phenocrysts in the lavas. Selected oxybarometers will include those that are based on titanomagnetite-ilmenite equilibria, ferrous-ferric ratios in minerals, multivalent element distributions in mineral pairs, and intrinsic oxygen fugacity measurements by electrochemical experiments. The relationship between liquid composition, temperature and oxygen fugacity in the magmatic systems saturated with Fe-Ti oxides will be determined by the melting experiments. The data from this study for the Panzhihua intrusion will be used to constrain the nature of the parental magma for this intrusion and the controls on ore formation in the intrusion. Ultimately, all of the data from this study will be used to address three outstanding important questions: (1) whether or not Fe-Ti oxide saturation in the magma was due to a sudden change in oxidation state (i.e., dramatic increase in fO2); (2) what is the most impotant factor to controll the oxidation state of ore-forming parental magma; (3) wether or not liquid immiscibility played a critical role in the formation of the Panzhihua Fe-Ti oxide deposit. More broadly, this study will improve our understanding of metallogeny associated with mantle plume activity in a continental setting.

英文关键词： Fe-Ti oxide deposit;Oxygen fugacity;Panxi layered intrusion;Panzhihua;Emeishan Large Ignious Provice