东昆仑南缘哥日卓托地区马尔争组沉积物源分析:碎屑锆石U-Pb年代学证据

摘要

为研究东昆仑南缘中下二叠统马尔争组沉积物源及沉积构造背景,对东昆仑南缘哥日卓托地区中下二叠统马尔争组进行了详细的沉积地层划分、沉积环境及碎屑锆石U-Pb年代学进行了研究.结果表明,马尔争组为一套形成于大陆斜坡半深海—深海环境的浊积岩系.碎屑锆石U-Pb年龄谱可明显划分为早古生代和新元古代两个主年龄谱及古、中元古代两个次级年龄谱.主年龄谱分别为396～573Ma和727～947Ma,峰值年龄分别为421Ma和862Ma.次级年龄谱分别为1117～1993Ma和2319～3063Ma,峰值年龄不明显.本文认为东昆仑南缘哥日卓托地区马尔争组物质来源较为复杂,显示早古生代、新元古代、中元古代和古元古代多个时代物源共同供给的特征.东昆仑造山带早古生代岩浆岩和新元古代岩浆岩为其提供了约60～65％的沉积物源,而古老的变质基底为其提供了仅约30～35％的沉积碎屑.综合区域资料认为马尔争组形成于相对稳定的被动大陆边缘沉积构造背景,该期阿尼玛卿古特提斯洋还未开始向北俯冲.%To study the sedimentary source and sedimentary tectonic setting of the lower Permian Maérzheng Formation in the southern margin of East Kunlun,detailed strata division,sedimentary environment and detrital zircon U-Pb geochronology were taken for the Lower Permian Maérzheng Formation in Gerizhuotuo area in the southern margin of East Kunlun in this paper.The results show that the Maérzheng Formation is a set of turbidite formed in bathyal-sea continental slope.Detrital zircon U-Pb age spectrum can be explicitly divided into Early Paleozoie and Neoproterozoic two main age spectrum and the Paleoproterozoic Mesoproterozoic secondary age spectrum.The main age spectra were 396～573 Ma and 727～947 Ma,the peak age was 421Ma and 862 Ma,respectively.The secondary age spectra were 1117～ 1993 Ma and 2319～3063 Ma,the peak age was not obvious.Combined with geological data in the study area and its adjacent area,it is considered that the sedimentary source of Maérzheng Formation in Gerizhuotuo area in the south margin of the East Kunlun is complex which shows characteristics of source supplied from multiple times,as Early Paleozoic,Neoproterozoic,Mesoproterozoic and Proterozoic.Early Paleozoic magmatic rocks and Neoproterozoic magmatic rocks in East Kunlun orogenic belt provide about 60～65 percent of sediment source and old metamorphic basement provides only about 30～35 percent of sedimentary debris for Maérzheng formation.Combined with previous data,we suggest that Maerzheng Formation formed in extensional system related to the passive continental margin tectonic setting,and the oceanic crust subducted from late Permian.