Major element compositions of garnet, clino-pyroxene, orthopyroxene and spinel in the garnet-bearing lower crust and upper mantle xenoliths from Hannuoba, North China craton are analyzed by the electron microprobe (EM...Major element compositions of garnet, clino-pyroxene, orthopyroxene and spinel in the garnet-bearing lower crust and upper mantle xenoliths from Hannuoba, North China craton are analyzed by the electron microprobe (EMP). The pressure-temperature estimates reveal the in-creasing temperature and pressure from core to rim for granulites. In contrast, mantle xenoliths with core tempera-ture > 930℃ recorded a history of decrease in temperature and pressure. However, those with core temperature < 930℃ show a negligible change. The final pressures recorded by these xenoliths cluster at 0.9—1.5 GPa. The presence of high- Na2O cpx in granulite xenoliths suggests that they are prod-ucts of the transition from granulite to eclogite metamor-phism corresponding to the increasing temperature and pressure. Together with previous studies, it is suggested that the P-T changes preserved in the xenoliths are related to lithospheric thickening and subsequent thinning prior to their eruption in the Cenozoic.展开更多
基金co-supported by the National Natural Science Foundation of China(Grants Nos.40133020 and 40003004)the Ministry of Science and Technology of China(Grant No.G1999043202)+1 种基金the State Key Lab for Mineral Deposits Research,Nanjing Universitythe Key Laboratory of Continental Dynamics,Northwest University.
文摘Major element compositions of garnet, clino-pyroxene, orthopyroxene and spinel in the garnet-bearing lower crust and upper mantle xenoliths from Hannuoba, North China craton are analyzed by the electron microprobe (EMP). The pressure-temperature estimates reveal the in-creasing temperature and pressure from core to rim for granulites. In contrast, mantle xenoliths with core tempera-ture > 930℃ recorded a history of decrease in temperature and pressure. However, those with core temperature < 930℃ show a negligible change. The final pressures recorded by these xenoliths cluster at 0.9—1.5 GPa. The presence of high- Na2O cpx in granulite xenoliths suggests that they are prod-ucts of the transition from granulite to eclogite metamor-phism corresponding to the increasing temperature and pressure. Together with previous studies, it is suggested that the P-T changes preserved in the xenoliths are related to lithospheric thickening and subsequent thinning prior to their eruption in the Cenozoic.
