On the basis of mineral assemblage,mineralogy,petrology,and major,trace ele-mental and isotopic geochemistry of the underplated granulite-and eclogite-facies accumulate,peridotite and pyroxenite xenoliths entrained in...On the basis of mineral assemblage,mineralogy,petrology,and major,trace ele-mental and isotopic geochemistry of the underplated granulite-and eclogite-facies accumulate,peridotite and pyroxenite xenoliths entrained in Hannuoba Cenozoic basalts,this work con-strained the petrological constituents for the crust-mantle transitional zone,which is supported by the results of high-temperature and pressure velocity experiments on rocks and geophysics deep survey.Present lower part of lower crust is mainly composed of granulite-facies mafic accumu-lates(dominantly plagioclase websterite)and crust-mantle transitional zone dominantly com-posed of eclogite-facies pyroxenites with or without garnet and spinel lherzolites;Archaean ter-rain granulite is only nominally early lower crust.Magma underplating in the crust-mantle boundary led to the crustal vertical accretion and the formation of the crust-mantle transitional zone,which is a significant mechanism for the chemical adjustment of the crust-mantle boundary since the Phanerozoic.展开更多
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 thes...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.展开更多
基金the Chinese Academy of Sciences(Gant No.KZCX1-07)the National Natural Scince Foundation of China(Grant No.40234050)
文摘On the basis of mineral assemblage,mineralogy,petrology,and major,trace ele-mental and isotopic geochemistry of the underplated granulite-and eclogite-facies accumulate,peridotite and pyroxenite xenoliths entrained in Hannuoba Cenozoic basalts,this work con-strained the petrological constituents for the crust-mantle transitional zone,which is supported by the results of high-temperature and pressure velocity experiments on rocks and geophysics deep survey.Present lower part of lower crust is mainly composed of granulite-facies mafic accumu-lates(dominantly plagioclase websterite)and crust-mantle transitional zone dominantly com-posed of eclogite-facies pyroxenites with or without garnet and spinel lherzolites;Archaean ter-rain granulite is only nominally early lower crust.Magma underplating in the crust-mantle boundary led to the crustal vertical accretion and the formation of the crust-mantle transitional zone,which is a significant mechanism for the chemical adjustment of the crust-mantle boundary since the Phanerozoic.
基金supported by the National Natural Science Foundation of China(Grant No.40372044).
文摘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.
