Geochemistry, geochronology, and zircon Hf isotopic compositions of felsite porphyry in Xiangshan uranium orefield and its geological implication

• Published in: Acta geochimica 2021-10, Vol.40 (5), p.773-786
• Main Authors: Tian, Mingming, Li, Ziying, Nie, Jiangtao, Zhong, Jun, Wang, Jian, Cao, Jianhui
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Anomalies; Cretaceous; Crystallization; Dating; Drilling; Earth and Environmental Science; Earth Sciences; Felsite; Field strength; Geochemistry; Geochronology; Geochronometry; Hafnium; Isotopes; Lead; Lithology; Metamorphic rocks; Original Article; Petrogenesis; Petrology; Plates; Plates (tectonics); Radiometric dating; Rhyolite; Rhyolites; Silica; Silicon dioxide; Subduction; Subduction (geology); Tectonics; Uranium; Volcanic rocks; Zircon; Zirconium
• ISSN: 2096-0956; 2365-7499
• DOI: 10.1007/s11631-021-00465-3

Recently, a new kind of volcanic rock, felsite porphyry, has been revealed by drilling in Xiangshan area, Jiangxi Province, China. To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-intrusive complex, we studied systematic petrology, geochemistry, LA-ICP-MS zircon U–Pb dating, and Hf isotope results of the felsite porphyry. Results show that the felsite porphyry has similar geochemical characteristics to the porphyroclastic rhyolite, which is the predominant lithology of Xiangshan uranium orefield. Felsite porphyry and porphyroclastic rhyolite have high SiO 2 , Al 2 O 3, and K 2 O contents, low Na 2 O, and MgO contents, and slightly negative Eu anomalies. Moreover, these rocks are relatively depleted in large ion lithophile elements (K, Ba, and Sr) and are enriched in high field strength elements (Th, Zr, and Hf). LA-ICP-MS zircon U–Pb dating of the felsite porphyry yielded a crystallization age of 132.2 ± 0.9 Ma, which is coeval to that of the porphyroclastic rhyolite. These ages signified that Xiangshan volcanic-intrusive complex formed in the Early Cretaceous, during which the entire South China was in the back-arc extension tectonic setting related to the subduction of the Pacific Plate under the Euroasian Plate. In-situ zircon Hf isotope data on a felsite porphyry sample show ε Hf ( t ) values from − 8.82 to − 5.11, while the Hf isotope two-stage model age ( T DM2-Hf ) ranges from 1513 to 1747 Ma. Combined with petrological, mineralogical, geochemistry, and geochronology results of the felsite porphyry, it is concluded that the felsite porphyry in Xiangshan might be originated from the partial melting of the Mesoproterozoic ancient metamorphic rocks, with possible input of small amounts of mantle materials.