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This work was supported by funds from the National Natural Science Foundation of China (Grant Nos. 42172067, 41972064, U1906207) and the SDUST Research Fund. We are grateful to Dr. Yang Wenqiang for his help with mineral chemical analyses at the Northwest University, China. Thanks are due to the editor and three anonymous reviewers for their constructive comments, that greatly helped to improve this manuscript.

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    Abstract:

    Gneisses with anatectic characteristics from the Liansan island in the Sulu UHPM (ultra-high pressure metamorphic) belt were studied for petrography, titanite U-Pb dating and mineral geochemistry. Three origins of garnets are distinguished: metamorphic garnet, peritectic garnet and anatectic garnet, which are formed in the stages of peak metamorphism, retrograde anatexis and melt crystallization, respectively. The euhedral titanite has a high content of REE and high Th/U ratios, which is interpreted as indicating that it was newly-formed from an anatectic melt. The LA-ICP-MS titanite U-Pb dating yields 214–217 Ma ages for the titanite (melt) crystallization. The distribution of trace elements varies in response to the different host minerals at different stages. At the peak metamorphic stage, Y and HREE are mainly hosted by garnet, Ba and Rb by phengite, Sr, Nb, Ta, Pb, Th, U and LREE by allanite and Y, U and HREE by zircon. During partial melting, Y, Pb, Th, U and REE are released into the melt, which causes a dramatic decline of these element contents in the retrograde minerals. Finally, titanite absorbs most of the Nb, U, LREE and HREE from the melt. Therefore, the different stages of metamorphism have different mineral assemblages, which host different trace elements.

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SONG Lihao, CAO Yuting, XIE Tianhe, CHEN Yuyao, GAO Yuan, WANG Songjie, LI Xuping.2023.[J]. Acta Geologica Sinica(),97(6):1640-1656

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History
  • Received:February 11,2023
  • Revised:August 02,2023
  • Online: December 25,2023
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