Geochronology, Geochemistry and Sr-Nd-Pb Isotopes of the Early–Middle Jurassic Highly Fractionated Granites in Southern Jiangxi, and their Implications for the Rare-Earth Mineralization: Examples from the Muzishan, Xiahu, and Zudong Deposits

Abstract

The pervasively distributed granitoids in South China contributed greatly to regional polymetallic mineralization, including tungsten, tin, copper, gold, rare metals, and rare earth elements (REEs). To ascertain the dynamic backgrounds, rock types and genesis of the parent rocks related to the Early–Middle Jurassic ionic rare earth mineralization, typical deposits at Muzishan, Xiahu, and Zudong were investigated by conducting petrographic, geochronologic, whole-rock geochemical, and Sr-Nd-Pb isotope analyses, which found that the parent rocks from the Muzishan deposit were the A1-type K-feldspar granite (~195 Ma), from the Zudong deposit were the A2-type monzogranite (~171 Ma), and from the Xiahu deposit were the I-type monzogranite (~167 Ma). All the three granitic rocks underwent different degrees of fractionation, with the Xiahu granite experiencing the highest degree, followed by the Zudong granite, and the Muzishan granite undergoing the lowest degree. The Muzishan granite was concluded to be formed under an intraplate extensional tectonic regime influenced by the hotspots or the mantle plume. The Zudong granite was formed in a post-arc extensional setting related to subduction–collision–rollback of the paleo-Pacific Plate, which caused upwelling of the asthenosphere, thinning of the lithosphere, and partial melting of crustal materials. The Xiahu granite was generated under a transitional tectonic setting of extension and compression, triggered by delamination and rollback of the paleo-Pacific Plate.