Two Magmatic Belts of the Neoproterozoic in the Qinling Orogenic Belt

Abstract

The magmatic belts of the Neoproterozoic in the Qinling Orogen can be divided into the North and South ones. The north belt is mainly developed within the distributed area occupied by the Qinling supracrusts. It is made up of the early Neoproterozoic granitoids, which are affected by strong metamorphism and deformation. The plutonic rocks demonstrate arc-related geochemical characteristics and formed between 950~840Ma. The south one is distributed in the south Qinling Range and around Hannan area with near EW direction. The magmatic belt is composed of bi–modal volcanics, gabbro bodies, basic dyke swarms, A–type granite and plutons within plates. In contrast to strong deformation of the plutons in the north belt, the rocks show weak deformation with dominant massive and weak gneiss structure, and formed between 810~710Ma. The belt took place a extension tectonic regime, which is response to initial rifting among Australia, Tarim–Yangzi and Laurentia continents in the western Rodinia.