Lower crustal xenoliths from Junan,Shandong province and their bearing on the nature of the lower crust beneath the North China Craton
会议名称：《中国科学院地质与地球物理研究所第十届(2010年度)学术年会》
会议日期：2011年
学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学]
基 金：supported by the National Natural Science Foundation of China(40534022) the Ministry of Science and Technology(2009CB825005) the Chinese Academy of Science(KZCX2-YW-103)
关 键 词：Granulite xenoliths Lower crust Petrology Geochemistry North China Craton
摘 要：Geochronological,petrological and geochemical studies were performed on the granulite xenoliths from a Late Cretaceous basaltic breccia dike in Junan,Shandong province,eastern *** xenoliths show close similarities to the Nushan granulite xenoliths from the southern margin of the North China Craton(NCC)and the Archean granulite terrains in terms of mineralogy and bulk rock compositions,but are quite different from the Hanuoba mafic granulite xenoliths from the northern ***-situ zircon U-Pb age and Hf isotopic analyses,together with geochemical data reveal that the protolith of these xenoliths was formed around 2.3 Ga ago,through assimilation-fractional crystallization of a mafic magma.P-T conditions of these xenoliths suggest that the lower crust beneath the Junan region reaches to a depth of 35 km,which agree well with the result deduced from various geophysical *** consistent petrological and seismic Moho depths,the observed velocity structure and calculated velocity of these xenoliths imply the absence of underplating induced crust-mantle transition zone,which was well formed in the northern *** to 40-50 km depth of the lower crust in Early Jurassic,the lower crust beneath Junan extended to a depth of 30 km in Late Cretaceous,suggesting that the lower crust of NCC was significantly thinned during Late Mesozoic.