晚三叠世—中侏罗世羌塘盆地的形成与演化

The formation and evolution of the Qiangtang Basin during the Late Triassic-Middle Jurassic period in northern Tibet

晚三叠世—侏罗纪是羌塘盆地大型海相沉积盆地形成时期,是研究羌塘盆地形成过程、判别盆地性质的重要时期。本文通过区域构造、盆地充填建造和岩相古地理分析,提出了该时期的羌塘盆地并非晚三叠世前陆盆地(或弧后盆地)和侏罗纪弧后盆地(前陆盆地),而是晚三叠世早期(肖茶卡期)的陆表海盆地和晚三叠世诺利期—中侏罗世巴柔期(那底岗日期-雀莫错期)的坳陷-裂陷盆。肖茶卡期内陆盆地主要受可可西里—金沙江活动带的控制,沉积期后出现的海退事件可能与冈瓦纳大陆与欧亚大陆的碰撞作用有关;那底岗日期—索瓦期羌塘盆地的强烈拉张断陷可能反映冈瓦纳大陆边缘的总体构造背景。

The major marine sedimentary facies basin formed during the Late Triassic and Middle Jurassic period is very important in studying the genetic process and type of Qiangtan Mesozoic basin. Based on lots of stratigraphic secting data, this paper made an analysis of regional tectonics, basin-filling sequences, hthofacies palaeogeography and thickness of the ore deposits formed during this period and, on such a basis, suggests that, instead of a foreland basin or a back-arc basin formed in Late Triassic and Jurassic period, the basin was an epicontinental basin formed in early Late Triassic （called Xiaochaka Phase） and also a depression-rifting basin formed in an extensional background from Norian Age to Middle Jurassic （called Nadigangri-Quemocuo Phase）. During the Xiaochaka Phase, the basin was impacted by the Hoh Xil-Jinshajiang active belt, and the regression event in the early stage of this period might have resulted form the collision between the Eurasian continent and the Gondwana land. During the Nadigangri-Quemocuo Phase, the strong extension and rifting event occurred, which probably reflects the extensional background of the margin of the Gondwana land.