青藏高原腹地典型盆-山构造形成时代

Dating of Typical Basin and Range Tectonics in Central Tibetan Plateau

青藏高原腹地发育NE向、NW向与SN向不同方向的盆 山构造系统。应用热年代学与ESR测年方法 ,测定青藏高原腹地典型盆 山构造 地貌的形成时期。结果表明 ,羌塘地块南部NE向双湖 和平盆 山构造的形成时期为 0～ 5Ma ,拉萨地块中部NE向羊八井 当雄盆 山构造裂陷开始时代为 6 .8～ 8Ma,而拉萨地块中部NW向格仁错—申扎盆 山构造的形成时期为 0～ 6 .5Ma。青藏高原腹地典型盆 山构造 地貌初始形成时代相近 ,约为 5～ 8Ma ,对应于区域构造环境自近SN向挤压缩短向近EW向伸展裂陷的转变时代。

NE , NW and NS trending basin and range tectonics occurred in central Tibetan Plateau after the plateau surface reached a certain altitude and the regional tectonic setting transferred from north south crust shortening to east west crust extension. To determine age of typical basin and range tectonics and evolutionary time of the central Tibetan plateau, the authors employed thermochronologic method and ESR dating. The rapid uplifting of mountains on both sides and rifting of basins in the middle of the NE trending Yangbajain Danxung basin and range tectonics began in 6.8～8 Ma. The rapid uplifting of granodiorite in the Jiagang Mountains on the southern side of Shenza basin began at about 6.5 Ma, followed by the formation of the NW trending Gelinco Shenza basin and tectonics. The extensional boundary faulting of the northeast trending Shuanghe Heping basin and range tectonics has taken place since 5 Ma. These data reveal an important fact that the change of regional tectonic setting from north south crust shorte ning to east west crust extension in central Tibetan Plateau might have occurred in 5～8 Ma.