地幔超高压矿物及其形成环境和构造意义

Diamonds were discovered before in podiform chromite ores in the Luobusa ophiolitie, southern Tibet. This project aims to find other mantle minerals associated with the diamonds by (1) observation of large number of thin sections and (2) separation of mineral from a big sample (1500kg) of original chromite massive ore. Over 70 sorts of unusual mineral have been identified in this study, including PGE minerals, alloys and sulfides, as well as about 20 grains of diamond ( ～0.7mm in diameter). Besides, some fine inclusions were found in the metal minerals, including alloys, oxides, sulfides and native element minerals. Talc and serpentine were founded as inclusions in the diamonds, which proved that the Luobusa diamonds are native but artificial..A series of pressure-dependent minerals were discovered, including coesite, kyanite, diamond, Si-rutile and Si-spinel, suggesting the minerals formed in a range of depth from upper mantle (about 100 km) to the lower mantle (2900 km). A mineral assemblage of Fe, FeO, SiO2, Si, Mg, FexSiy and silicate discovered in this study is comparative to the experiment results from a chemical reaction at boundary between outer core and lower mantle (Jeanloz and Knittle, 1989; Knittle and Jeanloz, 1991). We propose that some unusual minerals included within chromite ore were originated from the lower mantle, which were probably brought to a shallower depth in mantle by an upwelling superplume from the core-mantle boundary. During the arising, a series of pressure-dependent minerals were formed by chemical reaction between melts and silicates. The micro-explosion structure of the hydrous magnesium silicate found in this study probably can be explained by abrupt phase change of hydrous minerals during upwelling of the superplume..

用人工重砂和薄片研究相结合的方法，研究西藏蛇绿岩和江苏东海石榴石二辉橄榄岩的超高压（包括金刚石）矿物组合和新矿物。探索古大洋缝合带橄榄岩与大陆-大陆碰撞橄榄岩形苫肪澈颓治换啤