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    四川昭觉—美姑地区峨眉山玄武岩古火山机构的发现及其喷发旋回的确定

    Discovery of Paleo-volcanic edifice and determination of its eruptive circles of Emeishan basalt in Zhaojue-Meigu Area, Sichuan Province

    • 摘要: 四川昭觉—美姑地区峨眉山玄武岩古火山机构的发现及其喷发旋回的确定提要:野外地质调查发现,扬子西缘昭觉—美姑一带存在多处峨眉山玄武岩组古火山机构,为研究其火山喷发旋回与方式提供了良好窗口。古火山机构的岩石类型主要由巨厚玄武岩以及少量的火山碎屑岩和火山碎屑熔岩组成,且均具火山颈爆发相、溢流相和火山洼地相堆积构造特征。系统的地质剖面研究表明,峨眉山玄武岩组存在3次快速喷发亚旋回及25个火山韵律,亚旋回之间不存在火山间歇期。其中,第一亚旋回和第三亚旋回的喷发方式均以爆发相与溢流相为主,而第二亚旋回则以溢流相为主。峨眉山玄武岩组古火山机构的系统厘定和研究,揭示了峨眉山大火成岩省的火山喷发方式和旋回韵律特征,为研究与峨眉山玄武岩组相关的成矿成藏作用提供了重要地层资料。

       

      Abstract: The geological survey revealed that several paleo-volcanic edifices related to Emeishan basalt were identified in the Zhaojue-Meigu area on the western margin of Yangtze Block, which provides an excellent window for studying their eruption cycles and modes. The rock types of paleo-volcanic edifices are mainly composed of thick basalts, small amounts of pyroclastic rocks and volcanic clastic lavas. They have the characteristics of explosive facies, lava overflow facies and volcanic depression facies. Systematic geological profile suggest that there are three rapid eruption cycles (without any interval) and 25 volcanic rhythms during the formation of the Emeishan basalt Formation. Among them, the eruption patterns of the first and third cycles are dominated by the explosive facies and lava overflow facies, while the second cycle is dominated by the overflow phase. The systematic confirmation and study of the paleo-volcanic edifices reveal the volcanic eruption pattern and cycle rhythm characteristics of Emeishan large igneous province, which provides important data for the further study of the Wupo copper deposits in the western margin of Yangtze Block.

       

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