Discovery of the Mid-Late Jurassic Songmuguo strongly peraluminous granite belt in the southern part of Nyima County, Tibet, and its significance
LU Shu-wei, REN Jian-de, BAI Guo-dian, YANG Jun-feng, LU Ji-gen (Henan Institute of Geological Survey, Zhengzhou 450051, Henan, China)
A strongly peraluminous (SP) granites belt, extending over 100 km from east to west, is distributed 800 - 100 km south of the Bangong Co -Nujiang junction zone. It consists of several intrusions such as the Songmuguo intrusion and Yangxiongle intrusion. The intrusions are emplaced on both south and north sides of the Ngangze Co-Sereba fault and involve five intrusion events. They all belong to high-K, calk-alkaline, SP granites and are post-collisional SP granites of Mid-Late Jurassic age. Study suggests that the formation of the belt is related to the southward subduction and closing of the Nyima segment of the Bangong Co-Nujiang junction zone before the Middle Jurassic. The limited length of the SP granite belt and its earlier regional emplacement time show that the Meso-Tethys is composed of multiple blocks and closed in different times.