西藏冈底斯当惹雍错-许如错南北向地堑的特征及成因  

Characteristics and Mechanism of the Dangra Yun Co and Xuru Co NS-Trending Graben in the Gangdese,Tibet

作　　者：曹圣华[1,2] 李德威[3] 余忠珍[2] 徐祖丰[2] 唐峰林[2] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]江西省地质调查研究院,江西南昌330030 [3]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学（中国地质大学学报）》2009年第6期914-920,共7页Earth Science-Journal of China University of Geosciences

基　　金：国家重大基础研究前期研究专项(No.2005CCA05600);国家自然科学基金项目(No.40572113);中国地质调查局项目(No.20001300000141)

摘　　要：当惹雍错-许如错南北向地堑位于青藏高原冈底斯中部,由一组南北向高角度正断层与夹其中间的当穹错、当惹雍错、许如错等3个湖泊盆地构成.地堑发育于中新世晚期,一直活动到全新世.沿着地堑边缘分布中新世碱性火山岩.白榴石响岩的K-Ar年龄为12.6Ma,其岩石化学特征显示出陆内伸展构造环境.地堑内部发育晚更新世至全新世的湖相沉积物.当惹雍错-许如错地堑是在青藏高原板内构造隆升过程中,层流加厚的下地壳热垫作用导致上地壳发生伸展作用,随着青藏高原地壳物质的东流,南北向伸展作用转向东西向伸展作用,形成近南北走向的地堑.The Dangra Yun Co and Xuru Co NS-trending graben located at central section of the Gangdese, is controlled by NS- trending high-angle normal faults and consists of the Dangqung Co, Dangra Yun Co and Xuru Co. Miocene alkali volcanic rock distributed along the graben indicates an intraplate extensional tectonic environment by its petrochemical and geochemical analyses. A 12.6 Ma age is determined for leueite phonolite by the K-Ar method, and it is found that graben occurred at the late time of Miocene （about 13 Ma）, and remained active until Holocene. There are Middle Pliocene to Holocene lacustrine deposits in the graben. The Dangra Yun Co and Xuru Co graben, as well as other NS-trending grabens, is the results of extension of upper crust driven by the thermal upderplating of the lower crust flowing and thickening. S-N extension became E-W extension with the change of flow direction in the lower crust.

关 键 词：南北向地堑 构造地质 晚新生代 当惹雍错一许如错 青藏高原. 

分 类 号：P542[天文地球—构造地质学]