CHEN Chen¹, WANG Cheng-hui^1*, WANG Deng-hong¹, QIN Jin-hua^1,2, LU lei^1,3, DANG Xiao-liang⁴, FAN Xi-yin⁴, CHEN Xiao-rong⁴, ZHANG Wei⁴

(1. Key Laboratory of Metallogeny and Mineral Assessment, Ministry of National Resources, Institute of Mineral Resource, CAGS, Chinese Academy of Geological Sciences, Beijing 100037, China;
2. School of Earth Science and Resources, China University of Geoscience (Beijing), Beijing 100083, China;
3. School of Resources and Environmental Engineering, Hefei University of Technology, Anhui 230009, China;
4. The Seventh Geological Brigade of Zhejiang Province, Lishui 323000, China)

Abstract: In recent years, a large-scale ion-absorption type REE deposit has been discovered for the first time in the southern Zhejiang. This has further broaden the spatial distribution area of this type of REE deposits in the southern China. In order to intensively study the metallogenic characteristics of the Qingyuan ion-adsorption type REE deposit in the southern Zhejiang, eastern part of the Nanling orogenic belt, the U-Pb dating and Hf isotope analysis of zircons from the biotite monzogranite porphyry of the deposit have been undertaken in this paper. The results suggest that zircons of biotite monzogranite porphyry from the surface sample ZJLT have an age of 135.18±0.18 Ma (n=19, MSWD=0.25), εHf(t) values varying from -15.19 to -8.84, and model ages of two stages (TDM2) ranging from 2423 Ma to 2991 Ma; The zircons of biotite monzogranite porphyry from the core sample ZJLTZK havean age of 135.46±0.16 Ma (n=18, MSWD=2.0), εHf(t) values varying from -15.21 to -9.75, and model ages of two stages (TDM2) ranging from 2504 Ma to 2993 Ma. These indicate that the biotite monzogranite porphyry was formed in the early Cretaceous. The features of εHf(t)<0, TDM2 >>t(U-Pb), and plotting dots are above the crust line in the t-εHf(t) diagram for zircons of the biotite monzogranite porphyry indicate that the magma could be mainly derived from the partial melting of ancient upper crust materials in the south China. Combined with geological setting and study results, it is a considered that the biotite monzogranite porphyry, parent rock of the Qingyuan ion-adsorption type REE deposit, could be formed in the border area between Zhejiang and Fujian provinces during the late Yanshanian tectonic active movement via the recycling of magma derived from the partial melting of upper crust caused by the underplating of the basaltic magma due to the subduction of the Pacific plate into the underneath of the South China block.

Keywords: REE deposit; zircon U-Pb age; Hf isotope; Qingyuan in Zhejiang

ACTA MINERALOGICA SINICA Vol. 40, No.1, 2020, page 58-72