Strongly peraluminous granites of Mesozoic in Eastern Nanling Range,southern China: Petrogenesis and implications for tectonics

The strongly peraluminous granites (SPGs) of Eastern Nanling Range (ENR) are a characteristic of all bearing highly aluminous minerals, such as muscovite Alrich biotite tourmaline garnet, and lack of cordierite. In respect of petrography, geochemistry, Nd isotope, and single grain zircon U-Pb dating, the representative granite bodies of them are studied. The research shows that these granites were emplaced in two stages, namely 228–225 Ma BP and J_2–3 159–156 Ma BP, belonging to Indosinian and early Yanshanian periods, respectively, and they have low? ε _Nd(t) values (?10.6-?11.1), high A/CNK, Rb/Sr ratios and t_DM values (1887–1817 Ma), and REE’s tetrad effect (TE_{1, 3}=1.13–1.34). In comparison with related geology, petrology and chronology of granites in adjacent regions, it is suggested that Indosinian SPGs of ENR formed in the circumstance of post-collisional extension 20 Ma after the major collision of Indosinian Movement (258-243 Ma BP) in Indo-China Peninsula, and early Yanshanian SPGs formed in the background of back-arc extension setting controlled by paleo-Pacific tectonic domain, and J₁, the interval of two stages, is the interim from Tethyan to Pacific tectonic domains in South China. These SPGs have similar geological and geochemical characteristics, because they all crystallized from the magma of partial melting of early Proterozoic metasedimentary rocks when the thickened crust (≤50 km) became thinning, decompression, and transmitting of water.