摘要
本文在分析冈底斯中北部及邻区侏罗系—下白垩统内部的角度不整合,以及该时期沉积环境、变形变质和岩浆活动特点的基础上,首次提出冈底斯中北部弧盆系发育时限为早—中侏罗世;中侏罗世中晚期—早白垩世早期,羌南地块与冈底斯地块碰撞,班公湖—怒江带、狮泉河—嘉黎带强烈冲断,并形成前陆盆地;早白垩世中晚期,研究区进入后造山演化阶段,地幔物质上涌,形成叠加在中北冈底斯—南羌塘南缘碰撞造山带之上的伸展盆地,并发生强烈的深成岩浆活动;此种盆地经历的早期火山断陷和晚期拗陷等2个演化阶段,分别与地幔物质的早期上涌、晚期冷却回沉等深部地质过程对应。这些成果对研究青藏高原南部中生代地质构造演化具有重要意义。
Based on the analysis of the unconformity internal Jurassic to Lower Cretaceous,the characteristics of sedimentary,deformation metamorphism and magmatic activity at that time in the North—Central Gangdese and its adjacent area,the paper first proposes that the North— Central Gangdese was being arc basin system in Early—Middle Jurassic,Southern Qiangtang block collided with the Gangdese terrane from Middle Jurassic to the early stage of Early Cretaceous,thrust activities took place strongly and produced foreland basins in Bangong—Nujiang zone and Shiquanhe—Jiali zone at the same time. The North—Central Gangdese and its adjacent area was being postorogenic environment in Middle—Late Cretaceous,meanwhile,mantle material upwelling and convection,producd extensional volcano—sedimentary basins which superimposed on the North—Central Gangdise—southern Qiangtang collisional orogenic belt,magma intrusion activities was strongest than before. The superimposed basin recorded the two evolution stages of early volcano rift and late depression,they resulted respectively form mantle material upwelling and its cooling depression. The conclusion has important significance for the Mesozoic tectonic evolution of Southern Xizang(Tibetan) plateau.