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EID-05 Mantle petrology
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Magma underplating and Hannuoba present crust-mantle transitional zone composition: Xenolith petrological and geochemical evidences
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Qicheng Fan, Institute of Geology, China Earthquake Administration (China)
Jianli Sui, Institute of Geology, China Earthquake Administration (China)
Ni Li, Institute of Geology, China Earthquake Administration (China)
Qian Sun, Institute of Geology, China Earthquake Administration (China)
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On the basis of mineral assemblage, mineralogy, petrology, and major, trace elemental and isotopic geochemistry of the underplated granulite- and eclogite-facies accumulate, peridotite and pyroxenite xenoliths entrained in Hannuoba Cenozoic basalts, this paper constrained 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 mafic granulite-facies accumulates (dominantly plagioclase websterite) and crust-mantle transitional zone dominantly composed of eclogite-facies pyroxenites with or without garnet and spinel lherzolites. Archaean terrain granulites is only nominally early lower crust. Magma underplating in 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.
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