关键词: 峨眉山大火成岩省, 玄武岩, 水含量, 空间分布

Abstract: Recent research on the water content and mantle potential temperature of komatiites and picrites has found that the genesis of both Archaean and Phanerozoic large igneous provinces is related to hydrous mantle plume. The Late Permian Emeishan large igneous provinces (ELIP) is located in the western margin of the Yangtze craton in SW China, which is also considered as the effect of mantle plume. ELIP was divided into western zone, middle zone and eastern zone based on the work of geology and geochemistry in previous study. The previous study on the water contents for the picrites and basalts from Dali and Binchuan demonstrated that the water content in the mantle source in the western zone is higher than 2500×10^-6. However, the water content of source in other zones is still not clear, which makes it difficult to understand the role of water in the genesis of ELIP. Here, we estimated the water content of the mantle source of the high-Ti basalts in the lower part of Ertan sesstion, in the middle zone of ELIP, by the mothed of clinopyroxene phenocrysts. The result shows that the H2O content of clinopyroxene phenocrysts is 76×10^-6-424×10^-6, and the H2O content of the corresponding melt is 3.01 wt%. Considering the effect of fractional crystallization of minerals, the H2O content of primary magma is estimated to be 2.71±0.95 wt%, which is slightly lower than that of Dali picrites, and similar to that of Binchuan picrites. The estimated H₂O content in mantle source of Ertan high-Ti basalts is 1357×10^-6, which is lower than that of Dali and Binchuan picrites, but significantly higher than that of mid-ocean ridge basalts and ocean island basalts. The high H2O content of basalts and picrites in different areas in ELIP thus indicates that water plays an important role in both the genesis and the evolution of ELIP.

Key words: Emeishan Large Igneous Province, basalts, water content, spatial distribution