西藏羌塘地体中生代中—晚期不整合事件及其构造意义

不整合事件对于认识陆陆碰撞具有重要意义。羌塘-拉萨地体碰撞时间一直存在争议，其主要原因是"碰撞时间"定义不同，就不整合事件发生时间来说存在两种定义；一是与碰撞缝合带有关的区域性不整合的时间，早白垩世末(100 Ma)；二是洋壳消失，大陆之间陆壳初始的接触时间，盆地边缘不整合事件，即中侏罗世晚期(166 Ma)。针对上述问题，选取2种不同定义下的羌塘盆地内不整合面:北雷错西南与安多114道班地区不整合面进行研究。114道班地区下伏安山岩岩浆锆石U-Pb年龄为77 Ma，结合国内外学者对羌塘-拉萨地体碰撞时间的研究成果，认为羌塘-拉萨地体碰撞，发生强烈相互作用的初始时间为早白垩世末100 Ma，持续时间范围100~75 Ma。北雷错西南陆相地层最大沉积年龄为94 Ma，综合年代学、沉积学以及地层产状，认为该地层为新生代康托组，而非前人中侏罗世晚期"毕洛错组"的认识，进而认为羌塘-拉萨地体之间陆壳初始的接触时间不可能为166 Ma，但是一定早于100 Ma。 

Unconformable event and its tectonic significance at Middle-Late Mesozoic of Qiangtang terrane,Tibet

Uncomfortable event is significant to continent collision.Collision timing of Qiangtang-Lhasa terrane has always been controversial, because of the different definition of collision time.There are two definitions of collision time in terms of timing of uncomfortable event.One is connection with regional angular unconformity of collision suture zone at late Early Cretaceous(100 Ma), and the other is connection with angular unconformity in the basin edge with disappeared oceanic crust and initial touch of crust between continents at late Middle Jurassic(166 Ma).Focusing on the issue, this study researched unconformity of two difference definitions in Qiangtang Basin and they are Daoban 114 unconformity in Anduo area and southwest Beileicuo unconformity.U-Pb age of anshanite magmatic zircon is 77 Ma, combined with the collision timing of Qiangtang-Lhasa terrane research result, and we think strong interaction time between Qiangtang and Lhasa terrane was at late Early Cretaceous(100 Ma), continuous range 100-75 Ma.The maximum depositional age of continental stratum in Beileicuo area is 94 Ma.Synthesizing sedimentology, geochronology and attitude stratum, we think the strata deposited after 94 Ma and it was not late Middle Jurassic Biluocuo Formation but Cenozoic Kangtuo Formation.And then, initial touch of crust between Qiangtang-Lhasa terrane was not 166Ma but before 100 Ma.