柴西北地区碎屑锆石裂变径迹年龄记录的阿尔金山早新生代隆升事件

Early Cenozoic Altyn Mountains Uplift Recorded by Detrital Zircon Fission Track Age in Northwest Qaidam Basin

阿尔金山新生代隆升历史一直倍受关注,大量热年代学数据显示,渐新世（40～30 Ma）以来发生阶段性隆升,而新生代初期隆升的热年代学记录极少。柴达木盆地西北地区（柴西北地区）新生界碎屑锆石裂变径迹年龄研究表明,其物源区单一且在新生代早期古新世-中晚始新世（65～50 Ma）发生快速隆升剥露,为该区提供陆源碎屑。前人通过物源分析发现,柴西北时期的碎屑物主要来源于阿尔金山。同时,该区路乐河组-下干柴沟组沉积地层残余厚度及沉积相特征表明,此时（65～50 Ma）阿尔金山存在一次短暂抬升,但幅度较小,与盆地高差不大,使柴西地区地形东高西低、北高南低。结合前人研究成果,本研究锆石裂变径迹热年代学数据以及沉积学指标所记录的阿尔金山东段65～50 Ma构造隆升事件,是对新生代印度-欧亚板块碰撞的最初响应,也为青藏高原新生代隆升具有南北同步性提供了新的证据。

The Cenozoic uplift of Altyn Mountains has been closely concerned.A large number of thermochronology dates show that Altyn Mountains have periodically uplifted since Late Eocene（40-30Ma）.However,the thermochronology records of the early Cenozoic uplift of Altyn Mountains are rarely documented.The Cenozoic detrital zircon fission track age in the northwestern Qaidam basin shows thatthe detrital zircons came from the same source which did rapid uplift and exposed to the air in Early Cenozoic Paleocene-Middle Eocene（65-50 Ma）,and provided the terrene clast.The previously reported analysis results suggested that the source of the western Qaidam basin were from Altyn Mountains.In consideration of the residual thickness of the sedimentary strata and sedimentary facies of LuleheXiaganchaigou Formations in the western Qaidam basin,a brief and small-scale uplift of Altyn Mountains occurred in Early Cenozoic;which resulted in the small elevation difference between the mountains and the basin.Under the influence of the uplift,Qaidam terrain is high at southeast and low at northwest.The uplift represents the response of Altyn Mountains to the initial stage of collision between India and Eurasian plates.The zircon fission track thermal chronology data recorded the tectonic events of the middle-east part of Altyn Mountains in 65-50 Ma,which indicates the Cenozoic synchronicity uplifts of Tibetan plateau throughout south to north.