西藏林周盆地中侏罗统却桑温泉组碎屑锆石U-Pb年代学及地质意义

Detrital zircon U-Pb chronology and geological significance of the Middle Jurassic Quesang Hot Spring Formation in Linzhou Basin,Tibet

林周盆地位于冈底斯板块中部,对其进行盆地分析将为理解冈底斯板块构造演化过程提供重要的沉积学证据。本文以林周盆地中侏罗统却桑温泉组为研究对象,开展岩石学和碎屑锆石U-Pb年代学研究,结果显示却桑温泉组岩屑石英砂岩最年轻碎屑锆石年龄为169Ma,存在620~540Ma,1220~1055Ma等年龄峰值,其中最年轻碎屑锆石年龄是对特提斯洋壳俯冲引发的岩浆事件的响应。碎屑锆石区域对比研究表明却桑温泉组物源主要来自冈底斯中部唐加-松多造山带,为特提斯洋向北俯冲、向南增生过程的沉积记录。

The Linzhou Basin is located in the middle of the Gangdese Plate.Basin analysis of the Linzhou Basin will provide important sedimentological evidence for understanding the tectonic evolution process of the Gangdese Plate.This paper takes the Middle Jurassic Quesang Hot Spring Formation in the Linzhou Basin as the research object,and conducted petrology and detrital zircon U-Pb chronology.The results show that the youngest detrital zircon age of the lithic quartz sandstone of the Quesang Hot Spring Formation is 169 Ma,with age peaks such as 170-200 Ma,540-620 Ma,and 1055-1220 Ma.The youngest detrital zircon age is the response to a magmatic event triggered by the subduction of the Tethys oceanic crust.Regional comparative studies of detrital zircons show that the source of the Quesang Hot Spring Formation is mainly from the Tanga-Songduo orogenic belt in central Gangdese,which is a sedimentary record of the northward subduction and southward accretion of the Tethys Ocean.