Isotopic geochemistry, zircon U–Pb ages and Hf isotopes of A-type granites from the Xitian W–Sn deposit, SE China: Constraints on petrogenesis and tectonic significance. (1st June 2015)

• Record Type: Journal Article
• Authors: Zhou, Yun; Liang, Xinquan; Wu, Shichong; Cai, Yongfeng; Liang, Xirong; Shao, Tongbin; Wang, Ce; Fu, Jiangang; Jiang, Ying
• Is Part Of: Journal of Asian earth sciences. Volume 105(2015)
• Page Start: 122
• Page End: 139
• Publication Date: 2015-06-01
• Subjects: Geochemistry -- Zircon U–Pb dating -- A-type granite -- W–Sn deposit -- Southeast China; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2015.03.006
• Languages: English
• ISSNs: 1367-9120

Abstract

Highlights: Xitian granites give U–Pb age of ∼152 Ma. They belong to A-type granite. They are generated by crust–mantle interaction. Their formation is related with back-arc extension. The ore-forming materials and fluids are mainly produced by granitic magmatism. Abstract: Zircon U–Pb geochronological, geochemical and petrological analyses have been carried out on the Xitian granite emplaced in the middle part of Shi-Hang zone, which is closely related to the economically important Xitian tungsten–tin deposit in Hunan Province, Southeast China. LA-ICP-MS zircon U–Pb dating of two representative samples yielded weighted means 206 Pb/ 238 U age of 151.7 ± 1.2 Ma and 151.8 ± 1.4 Ma. These granites are comprised mainly of K-feldspar, quartz, plagioclase, Fe-rich biotite and minor fluorite, and are characterized by enrichments in Rb, Th, REEs (total REE = 159–351 ppm), and HFSEs (e.g., Zr and Y) but depletions in Ba, Sr, P, Eu and Ti. They are metaluminous to weakly peraluminous and show a clear A-type granite geochemical signature with high SiO2 (73.44–78.45 wt.%), total alkalis (Na2 O + K2 O = 2.89–8.98 wt.%), Fe2 O3 ∗ /MgO ratios and low P2 O5, CaO, MgO and TiO2 contents. In-situ zircon Hf isotope analysis suggests their ε Hf ( t ) values ranging from –7.43 to –14.69. Sr–Nd isotope data show their ε Nd ( t ) values in the range of –9.2 to –7.3, with corresponding T DM2 ages of 1.72–1.56 Ga. These characteristics indicate that the Xitian granite originated from partial melting of metamorphic basement rocks with a certain amount of mantle-derived materials. Combined with previous geochemical and isotopic data, it is derived that mantle–crust interaction was gradually enhanced from the early to late stages of magmatism. The ore-forming materials and fluids of the Xitian W–Sn deposit are mainly produced by the Early Yanshanian granitic magmatism, which is also responsible for the Late Jurassic (ca. 152 Ma) A-type granitic rocks that host the W–Sn polymetallic deposits distributed along the Shi-Hang zone, implying a significant Mesozoic extensional event in Southeast China likely caused by the subduction of the Paleo-Pacific plate.