沉积与特提斯地质2024，Vol.44Issue(4)：757-772,16.DOI:10.19826/j.cnki.1009-3850.2024.07003
藏东地区左贡地块寒武系和奥陶系的新发现及其大地构造意义
New discovery and tectonic significance of Cambrian and Ordovician strata in the Zuogong Block,eastern Xizang
摘要
Abstract
The lack of a definitive discovery of Early Paleozoic sedimentary cover in the Zuogong Block is one of the reasons for controversy over the division of stratigraphic system and the structural framework in eastern Xizang.This paper reports the results of detrital zircon U-Pb dating and regional stratigraphic correlation of two newly identified shallow metamorphic rock series,originally classified as Triassic strata,in the Cuoga and the Guoxuepu areas of the Zuogong Block,and further discusses the structural attributes of the Zuogong Block.Mica quartz schist,mica schist,marble,and meta quartz sandstone assemblages have been identified in the original Upper Triassic Guoxuepu Formation(Adula Formation)in the Cuoga area.The mica quartz schist exhibits a youngest clastic zircon age of 548 Ma,indicating a Cambrian sedimentary age according to regional stratigraphic lithology and age correlation.The original Upper Triassic Guoxuepu Formation(Jiapila Formation)in the Guoxuepu area consists of slate and metaquartz sandstone assemblages,with its sedimentary age revised to the Early Ordovician,based on the youngest clastic zircon age of 491 Ma in the meta quartz sandstone.The difference in the youngest age components of the detrital zircons from the two newly identified strata reflects changes in the sedimentary source areas between the Cambrian and Ordovician.Based on regional data,it is believed that the Zuogong Block is comparable to the South Qiangtang and Baoshan Blocks in terms of Early Paleozoic strata,Early Paleozoic magmatic events,and Late Paleozoic glacial-marine diamictite,in addition to Pan-African detrital zircons.During the Prototethys evolution stage,the Zuogong Block was part of the northern margin of the Gondwana continent and served as a link between the South Qiangtang and Baoshan Blocks.This result indicates that the extension of the Longmuco-Shuanghu suture zone in eastern Xizang lies between the Zuogong Block and the Changdu Block.关键词
藏东/左贡地块/寒武系/奥陶系/碎屑锆石Key words
eastern Xizang/Zuogong Block/Cambrian/Ordovician/detrital zircon分类
天文与地球科学引用本文复制引用
刘函,苟正彬,吴义布,郝学辉,张士贞,李俊,张予杰,高睿..藏东地区左贡地块寒武系和奥陶系的新发现及其大地构造意义[J].沉积与特提斯地质,2024,44(4):757-772,16.基金项目
地质调查项目"冈底斯-藏南成矿带区域地质调查"(DD20240032),"西南重大工程地质安全调查与评价"(DD20221811) （DD20240032）
国家自然科学基金项目"措勤—改则地区木纠错组时代厘定:对拉萨地块晚二叠世—三叠纪沉积演化的制约"(42002032) （42002032）
科技部青藏科考项目"深时特提斯生物与环境演变"(2019QZKK0706) （2019QZKK0706）
