藏南康马奥陶系及其底砾岩的发现并初论喜马拉雅沉积盖层与统一变质基底的关系

Discovery of the Ordovician and its basal conglomerate in the Kangmar area, southern Tibet-with a discussion of the relation of the sedimentary cover and unifying basement in the Himalayas

摘要: 藏南北喜马拉雅拉轨岗日带康马岩体西南侧,奥陶系及其底砾岩覆盖于前奥陶系拉轨岗日群(POL)之上,后者被515～485Ma拉轨岗日构造穹隆带花岗岩侵入,沿不整合面又被泛非运动最晚期的基性脉岩侵入。奥陶系与前奥陶系的接触关系为伸展不整合,与喜马拉雅甚至冈底斯带有关剖面完全可以对比。这一不整合面即是冈瓦纳大陆北缘统一变质基底和沉积盖层的分界。冈瓦纳大陆统一变质基底的形成始于震旦纪末的“泛非运动”,其终止时间在喜马拉雅及以北地区可以延续至寒武纪—奥陶纪之交,表现为区域上不断的伸展—拉张—裂解的构造环境。由此可以认为伸展构造亦是控制统一变质基底与沉积盖层的形成机制之一。

Abstract: In southern Tibet, Ordovician and its basal conglomerate cover the pre-Ordovician Lhagoi Kangri Group on the southwest side of the Kangmar rock body in the Lhagoi Kangri belt of the North Himalaya, the latter is intruded by the 515-485 Ma old granite of t