Zircon U-Pb Dating for Paragneiss in the Xinxian Area in the Dabie–Sulu Orogenic Belt and Its Geochemical Characteristics

Zhu Shaogong,Li Zian,Zhang Yuquan,Liang Yingjie

doi:10.3389/feart.2021.778377

Abstract

In order to understand the subduction of the Yangtze block and its collision with the North China Craton, we performed the elements analysis and zircon U-Pb dating on paragneiss from Xinxian area, which located along the west edge of the Dabie-Sulu ultrahigh-pressure (UHP) metamorphic belt. The major elements analysis showed SiO2, Al2O3, and K2O were enriched and the rare-earth element (REE) analysis showed the paragneiss had a high content of REEs, especially light rare Earth elements (LREEs). The elements analysis suggest that the protolith of paragneiss may be formed by terrestrial materials. As reflected by cathode luminescence (CL), zircon in rocks was metomorphic and had a core-edge microstructure. The edge of zircon was dated by LA-ICP-MS at 233 ± 24 Ma, which suggests that the paragneiss was formed later than the Triassic. The inherited zircon had a large age range of 456–1,727 Ma, mainly in the range of 705–811 Ma. The wide range of ages suggests that the protolith of paragneiss was sedimentary rocks formed no earlier than the Paleozoic. And the paragneiss from Xinxian area were generated in the Dabie-Sulu ocean basin or abortive ocean basin in the Paleozoic era.

Highlights

As one of the largest UHP metamorphic belts in the world, the Dabie-Sulu belt, located between the northern margin of the Yangtze Craton and the southern margin of the North China Craton, has received much attention
Our work suggests that the edge of metamorphic zircon is consistent with the data reported by previous researchers, providing further evidence that paragneiss in Xinxian county experienced ultrahigh-pressure metamorphic events during the Triassic
1) Paragneiss in the Qianhe and Chengbei areas of Xinxian county experienced a metamorphic event during 233 ± 24 Ma, suggesting that the rock was formed later than the Permian

Summary

Introduction

As one of the largest UHP metamorphic belts in the world, the Dabie-Sulu belt, located between the northern margin of the Yangtze Craton and the southern margin of the North China Craton, has received much attention. It has been widely investigated since the discovery of coesite and microgranular diamond in its eclogite (Okay et al, 1989; Wang et al, 1989; Shutong et al, 1992; Shu-tong et al, 2003). Other studies found that the protolith contained Paleoproterozoic and Archean

Methods

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Discussion

Conclusion