Magma underplating and Hannuoba present crust-mantle transitional zone composition: Xenolith petrological and geochemical evidence |
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Authors: | Email author" target="_blank">Qicheng?FanEmail author Hongfu?Zhang Jianli?Sui Mingguo?Zhai Qian?Sun Ni?Li |
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Institution: | 1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;Institute of Geology, China Seismological Bureau, Beijing 100029, China 2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 3. Institute of Geology, China Seismological Bureau, Beijing 100029, China |
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Abstract: | 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. |
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Keywords: | magma underplating xenolith petrology geochemistry cust-mantle boundary constituent Hannuoba |
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