西天山温泉别珍套山阿克沙克组物源及沉积环境分析

Provenance and sedimentary environment of Akeshake Formation in Biezhentao Mountain,Wenquan,Western Tianshan

温泉别珍套山阿依尔朔克一带出露的下石炭统阿克沙克组沉积地层,是西天山石炭纪构造演化的重要物质记录。阿克沙克组下段以碎屑岩发育为特点,沉积韵律清晰,常形成砾岩-中细砂岩-粉砂岩或含砾中粗砂岩-细砂岩-粉砂岩的旋回层,反映出一系列海进、海退特征;上段以发育较多的碳酸盐岩为特点,含大量海相化石。阿克沙克组的物源区母岩为中酸性火山岩和少量沉积岩,碎屑颗粒沉积速度较快,属于近源沉积;蚀源区构造环境具活动性质,形成于未切割的大洋活动岛弧。碎屑岩颗粒分选多为中等,偏度上多为近对称,峰态为中等-尖锐;碎屑岩粒度概率累积曲线上跳跃组分比例均较大,多在90%以上,且多由2个次总体组成,水动力条件随机变化。总体上阿克沙克组下段为滨-浅海相沉积,上段为典型的浅海陆棚沉积。

Akeshake formation sedimentary strata,widespread in Ayiershuoke area of Biezhentao Mountain Wenquan county,is an important geological record for the study of the Carboniferous tectonic evolution of the western Tianshan.The lower Akeshake formation is characterized by more clastic rocks and clear sedimentary rhythm,which formed gyration of conglomerate-medium fine sandstone-siltstone or gravelly medium coarse sandstone-fine sandstone-siltstone conglomerate-fine sandstone-siltstone or conglomerate-coarse sandstone-fine sandstone-siltstone,reflected a series of transgressive and regressive characteristics.The upper Akeshake formation was characterized by more carbonate rocks,and contains a large number of marine fossils.The source rocks of Akeshake formation were intermediate-acid volcanic rocks and a small amount of sedimentary rocks,the clastic particles are deposited quickly,which belonged to near-source deposits.The tectonic environment of the source area was active and formed in the uncut oceanic active island arc.Clastic rock particle sorting was mostly medium,skewness was nearly symmetrical,kurtosis was medium-sharp;the percentage of jumping components on the probability cumulative curve of clastic rock particle size was larger,more than 90%,and mostly consists of two sub-collectivity,and hydrodynamic conditions change randomly.Generally,the lower Akeshake formation was Littoral-shallow marine facies sediments,and the upper Akeshake formation was typical shallow shelf sediments.