新疆西昆仑独尖山地区黄羊岭组碎屑锆石U-Pb年龄及其对特提斯洋构造演化的指示

    Detrital zircon U-Pb age of Huangyangling Formation in Dujianshan area from West Kunlun, Xinjiang: implications for tectonic evolution of Tethyan Ocean

    • 摘要: 新疆西昆仑独尖山地区巴颜喀拉盆地北部发育黄羊岭组,岩性为一套灰色长石岩屑砂岩、灰白色石英砂岩、灰黑色粉砂岩等细碎屑岩组合,中部夹大量凝灰质成分,局部夹碳酸盐岩透镜体,含丰富的生物化石,指示时代为中二叠世。为进一步查明区域上黄羊岭组沉积时代及沉积区物质来源,在黄羊岭组一段顶底采集了2件碎屑岩样品,利用LA-ICP-MS对锆石U-Pb年龄及微量元素含量进行分析。其中,碎屑锆石206Pb/238U年龄主要集中于264~276Ma、292~317Ma、369~373Ma、500~503Ma、694~702Ma五个区间,最年轻的锆石峰值年龄为266.1±0.89Ma,表明该地区黄羊岭组开始沉积的时间为中二叠世中期。通过锆石微量元素判别图解对锆石的成岩类型进行判别,结合所取得的年龄数据,综合比对区内特提斯洋构造演化,认为264~276Ma碎屑锆石来源于海西运动中昆仑造山带内的花岗质岩石和基性火山岩,292~317Ma碎屑锆石来源于北侧喀什塔什地区石炭系—二叠系托库孜达坂岩组内的火山岩建造,500~503Ma碎屑锆石来源于古特提斯洋主体形成时的岩浆构造演化,694~702Ma碎屑锆石则来自于原特提斯洋北侧的塔里木陆块或大洋中的北羌塘微陆块,而369~373Ma的碎屑锆石来源于晚泥盆世古特提斯洋裂解初期小规模的火山活动。

       

      Abstract: Huangyangling Formation is developed in the northern part of the Bayankara Basin in the Dujianshan area,western Kunlun,Xinjiang,which is composed of a series of fine clastic rocks such as gray feldspar lithic sandstone,gray-white quartz sandstone and gray-black siltstone,and there are a lot of tuff and carbonate lens in the middle part,which are rich in fossils,indicating the Middle Permian age. In order to further identify the sedimentary age and material source of the Huangyangling Formation in the region,two clastic rock samples were collected from the top and bottom of the first member of the Huangyangling Formation,and the zircon U-Pb age and micronutrient content were analyzed by LA-ICP-MS. The 206Pb / 238U ages of detrital zircon are mainly concentrated in the five ranges of 264~276 Ma,292~317 Ma,369 ~ 373 Ma,500~503 Ma,694~702 Ma. The youngest zircon has a peak age of 266.1 ±0.89 Ma,indicating that the Huangyangling Formation began to deposit in the Middle Permian. Based on the zircon micronutrient diagram,the diagenetic types of zircons and the age data obtained,the tectonic evolution of the Tethys Ocean in the region is compared,and it is considered that the detrital zircon of 264~276 Ma originates from granitic rocks and basic volcanic rocks in the Kunlun orogenic belt during the Hercynian movement,the detrital zircon of 292~317 Ma originates from the volcanic formations in the carboniferous-permian Tuokuzidaban Formation in the Kashitashi area,the 500~503 Ma detrital zircon is derived from magmatic tectonic evolution during the formation of the Paleo-Tethys Ocean body,while the 694~702 Ma detrital zircon is derived from the Tarim Block on the northern side of the Proto-Tethys Ocean or the northern Qiangtang microblock in the ocean,the detrital zircon of 369 ~ 373 Ma is inferred to be from a small-scale volcanic activity during the early cracking of the Paleo-Tethys Ocean in the Late Devonian.

       

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