Geochemistry Characteristics of Eocene Volcanic Rocks in Sanshui Basin, Guangdong

Guangdong Sanshui basin developed with extreme volcanic activities. Eruptions from Paleocene to Eocene were concentrated on Xinzhuang, Buxin, Baoyue and Huayong formations. For research of the relationship between various kind of rocks, geochemistry analyses such as multi-element and rare-earth element determination were launched on basalt, trachyte and rhyolite samples from the research area. Geochemistry diagrams suggest that: REE distribution of basalt followed as mid-plate alkali basalt mode, while their trace element spider diagrams act as continental alkali basalt with Nb, Ti rich and Sr loss. REE distributions of trachyte and rhyolite are similar, which indicate the same crystallization separation process. S-B diagram and pearce diagram show that: granites were partially melted from source region, while trachyte in ZMY and rhyolite in LBS originated from the same source region, and occurred with the process of crystallization separation with plagioclase adventage. Southeast China performed continental rift environment as Red Sea, and its magma may came from lithospheric mantle source. The magmatic activities suspended after 42 Ma because of regional extrusion, while breaking up of South China Sea (SCS) later may be a mixed effect of two functions.