Nature, Source and Composition of Volcanic Ash in Surficial Sediments Around the Zhongsha Islands

• 作 者: YAN Quanshu SHI Xuefa WANG Xin
• 机 构: Key Laboratory of Marine Sedimentology and Environment Geology,Guangxi Institute of Geological Surve
• 出 处: 中国海洋大学学报（英文版）
• 发表日期: 2004年期
• 关键词: volcanic glass bimodal volcanic activity tectonic setting the South China Sea
• 基金项目: the Special Program for the Talented in Science and Technology in Qingdao;Special Project of Technical Foundational Work and Social Public Welfare Research

Volcanic detrital sediments are a unique indicator for reconstructing the petrogenetie evolution of submarine volcanic terrains. Volcanic ash in surficial sediments around the Zhongsha Islands includes three kinds of volcanogenic detritus, i.e., brown volcanic glass, colorless volcanic glass and volcanic scoria. The major element characteristics show that bimodal volcanic activity may have taken place in the northern margin of the South China Sea, with brown volcanic glass and colorless volcanic glass repre-senting the maric end-member and felsie end-member, respectively. Fractional crystallization is the main process for magma evolu-tion. The nature of the volcanic activity implies that the origin of volcanic activity was related to extensional tectonic settings, which is corresponding to an extensional geodynamie setting in the Xisha Trench, and supports the notion, which is based on geophysical data and petrology, that there may exist a mantle plume around the Hainan Island.