Minerals of spinel- and garnet-facies mantle xenoliths entrained in Cenozoicbasalts from eastern China (North China, Northeastern China and Southeastern China coastal area)contains lots of melt inclusions. Studies on these melt inclusions show that the glass inclusionsare rich in SiO_2 (60%—68%) and alkalis (K_2O+Na_2O = 5%—11%, especially for K_2O) as well asvolatiles such as H_2O and CO_2 (2%—7%), which belong to dacites and andesites of the high-K calcicalkali series rocks with few shoshonites. High Al and Ca diopside in melt inclusion is the productof melt crystallization at high temperature and pressure, rather than the product ofdevitrification. Results show that these K-rich (in general K_2O > 3%) intermediate-acidic silicatemelt inclusions have characteristics of continent without a genetical link to host basalts and theirphenocrystic minerals. Thus, these trapped melt inclusions represent melts of Mesozoic lithosphericmantle-crust interaction and imply that the continental lithospheric mantle beneath eastern Chinahad undergone fragmentation and recreation processes during the Mesozoic and Cenozoic periods. Thisresult undoubtly provides important implication for the evolution of sub-continental lithospherebeneath eastern China. We propose that these Si- and alkalis-rich melts should be responsible forthe mantle chemical heterogeneity underneath eastern China.
FAN Qicheng1, SUI Jianli2, XU Ping2, LI Ni1, SUN Qian1 & WANG Tuanhua1 1. Institute of Geology, China Seismological Bureau, Beijing 100029, China
