Continental Lithospheric Mantle Characteristics Of North Chain And South China

There are distributed a great number of Cenozoic basalts and mantle derived xenoliths in North China and South China. For understanding the materials constitutes, evolution, mantle metasomatism, and inhomogeneity of the Lower crust and Upper mantle, there is a must of doing some research on these host basalts and the xenoliths.Based on the study of correlativity of Ol-Opx-Cpx contents in North China and South China, it shows that some peridotite xenoliths from Hannuoba, Pingquan, Nvshan, Puning, Qiongbei, and Niutoushan area may represent the older mantle material compositions, and some peridotite xenolith from Ximeng, Penglai, Linqu, Quzhou, Mingxi, and Liuhe area may represent the younger mantle material compositions.Through the REE charactheristics being studied, it suggests that the xenoliths from Hannuoba, Ximeng, and Puning area have no the trend of LREE enrichment, which ratios of LREE/HREE approximate 1. Therefore,, it is not different from Archean lithospheric mantle.On the basis of the study on the petrology, Trace element, and isotopic geochemistry, the primary magma of volcanic rocks can be divided into two series according to their originated rocks and degree of partial melting. One is the basanite-alkaline basalt-Olivine tholeiite magma series, which are generated by partial melting from spinel Iherzolite; the other is nephelinite magma-alkaline picritic basalt magma, which are generated by partial melting of the garnet Iherzolite.According to the Sr-Nd isotopic characteristics of peridotite xenoliths and their host basalts, it indicates that xenoliths in Hannuoba, Puning area may represent source area of the host basalt because of the xenoliths and host rocks being in the same plot; however, the xenoliths is not directly related to their host rocks of the others area for the xenoliths plot out of the range of their host basaltic rocks.Thermal dynamics calculation shows that the peridotite xenoliths are formed in the condition of pressure of 9.45-25kb and temperature of 945-1281 .