Analysis of X-Ray Fluorescence Spectroscopy and Plasma Mass Spectrometry of Pangxidong Composite Granitoid Pluton and Its Implications for Magmatic Differentiation
1. Guangxi Geological Survey Institute, Nanning 530023, China 2. School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China 3. Guangdong Provincial Key Laboratory of Mineral Resources & Geological Processes, Guangzhou 510275, China 4. Key Laboratory of Mineral Resource, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Abstract：Pangxidong composite granitoid pluton located in the southwestern margin of Yunkai massif. The metamorphic grade of this pluton increases from outside to inside, that is, banded-augen granitic gneisses, gneissoid granites and granites distribute in order from edge to core. X-Ray Fluorescence Spectroscopy and Plasma Mass Spectrometry are conducted to study the geochemical characteristics of the three types of rocks. The result shows that all the three types of rocks are peraluminous rocks and their contents of main elements and rare earth elements change gradually. From granitic gneisses to granites, the contents of Al2O3, CaO, MgO, TiO2, total rare earth elements and light rare earth elements increase, but the contents of SiO2 and heavy rare earth elements decrease. It is suggested that the phylogenetic relationship exists between granitic gneisses, gneissoid granites and granites during the multi-stage tectonic evolution process. Furthermore, the remelting of metamorphosed supracrustal rocks in Yunkai massif is probably an important cause of granitoid rocks forming. The evolutionary mechanism is probably that SiO2 and heavy rare earth elements were melt out from the protolith and gradually enriched upward, but Al2O3, CaO, MgO, TiO2 and light rare earth elements enriched downward.
Key words：Pangxidong pluton;Yunkai massif;Magmatic differentiation;X-ray fluorenscence spectroscopy;Plasma mass spectrometry
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