MANTLE SOURCE AND TECTONIC SETTINGS FOR THE VOLCANIC ROCKS FROM DANZHOU GROUP IN LONGSHENG AREA, NORTHERN GUANGXI
Danzhou group in Longsheng area formed at late Proterozoic era (820～760 Ma), and its Hetong formation is composed of spilite and rhyolite which constitute the bimodal rock association. The source magma of spilite deserved from enriched lower lithospheric mantle which had ever been metasomatized by fluid from subducted slab. Rhyolite and spilite are the products of cogenetic magma through the process of crystallization and differentiation. Bimodal volcanic rocks formed at an extensional setting of continental lithospheric thinning, and related to the activities of mantle plume, which led to the breakup of late Proterozoic Rodinia supercontinent.