Petrologic and geochemical Characters of the nanmulin intrusive Rock mass in the Cuoqin basin tectonic Implication

摘要

Th Nanmulin intrusive rock mass is exposed south of Nanmulin in the Cuoqing basin. It is a composite one. Its main part is quartz monzonite, but there are amphibole quartz syenite and biotite quartz orthophyre as small intrusives to intrude into quartz mononite. All rocks constitute a meta-alkaline magma association of monzonite, syenite and orthophyre. The geochemical study shows that this rock mass belongs to the "T" type granite and is a product of differentiation of basic magma. As a component of an island arc, it was formed at the early stage of the Himalayan movement, and its formation might be related to the northward subduction of the new Tethys oceanic crust along the Yarlung Zangbo River fault.