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Mesozoic Basalt and Mineral Chemistry of the Mantle-Derived Xenocrysts in Feixian, Western Shandong, China: Constraints on Nature of Mesozoic Lithospheric Mantle

PEI Fu-ping, XU Wen-liang, WANG Qing-hai, WANG Dong-yan   

  1. College of Earth Sciences, Jilin University, Changchun 130061, China
  • Received:2004-03-20 Revised:2004-03-20 Online:2004-03-20 Published:2004-03-20

Abstract: Mesozoic basalt in Feixian, western Shandong, is composed of alkaline basalt with K-Ar age of 119 Ma. Abundant mantle-derived xenocrysts such as olivine, orthopyroxene and clinopyroxene can be found in the basalt. The circle cracks occur in the olivine xenocrysts. The Mg# values of the olivine xenocrysts range from 90.0 to 93.0(ave. 91.5). The typical reaction rims can be found between pyroxene xenocrysts and host rock. The Mg# values of the orthopyroxenes and clinopyroxenes are 88.0~93.5(ave. 90.4)and 86 0~91.7(ave. 88.4), respectively. The mineral compositions of the xenocrysts are similar to those of the mantle-derived peridotites in Cenozoic basalts of eastern China, which implies that they should be the fragments of the mantle peridotite carried by the host magma and represent a new accreted lithospheric mantle. Petro-geochemical data of Feixian basalt indicate that this is characteristic of mantle-derived primary magma. High Isr, 1ow εNd(t)and depletion of high field strength elements (HFSE)in the basalt could be related to the mixed melting of the broken-off subducted slab(the eclogites in the Su-Lu orogen)and the material from the asthenosphere.