STUDY ON THE BASIC IGNEOUS EVENT IN CENTRAL QIANGTANG, TIBET

摘要

It bas been considered that large|scale basic igneous activities are related to results of the break|up of paleo|continent. Basic magmatism could record the dynamics information for orogenic process. Thus, studying it can help us to reconstruct the forming and evolution process of continental orogenic zone.The basic igneous zone in the central part of Qiangtang, Tibet, starts at the Sino|Indian border in the west and ends at Shuanghu region in the east, being over 800km long and several to more than 100km wide. Based on published data, there are coeval basic magmatic activities with similar features in Sanjiang region, Western Yunnan and Thai|Malaysian Peninsula. the basic dykes from Boyamalong to Qomu in central Qiangtang occur in swarms with E|W trending and are more than one thousand in number. Single or composite igneous body is 1 to 7 km long and 0.3 to 3 km wide, being of the area of 0.3 to 20km+2 . The total exposed area of the dykes is more than 400km+2 . The country rocks of the intrusives are the upper Carboniferous Mushirbuka group, which consists of rift|type deposits containing glaciomarine petromictic conglomerates.No basic dyke has been found in the strata since late Permian (Mokou Period)