Characteristics of volcanic ash in surficial sediments around Zhongsha islands(Macclesfield Bank):re

• 作 者: YanQuan-Shu;ShiXue-Fa;Liuji-hua;
• 机 构: Key laboratary of Marine Sedimentology and Environment Geology,State Oceanic Administration,Qingdao
• 出 处: 2007全国博士生学术论坛——海洋、水产领域
• 发表日期: 2007年期

　　Volcanic ash in surficial sediments around Zhongsha Islands,the South China Sea,mainly include three kinds of volcanogenic detritus,for example,brown volcanic glass,colorless volcanic glass and volcanic scoriaTAS diagram for these three kinds of volcanogenic detritus mentioned above,combined with variation diagram for Al2O3 FeO*、MgO、CaO Na2O、K2O vs SiO2,shows that there may be exist birnodal volcanic activity in the northern margin of the South China Sea,brown volcanic glass and colorless volcanic glass represent basic end member and acidic end member respectively,and crystallization differentiation is the main process for magma evolution.The bimodal volcanic activity implies that the origin of volcanic activity lies in continental extensional setting,supports that Xisha trench is a phenomena for ongoing or activating extensional geodynamics setting,and affirms that there exists Hainan plume which is put forward based on geophysical data.