Petrogenesis and Tectonic Implications of the Kwangsian Orogen: Constraints from Geochemistry and Sr-Nd-Hf Isotopic Compositions of the Early Paleozoic Peraluminous and Aluminous Granitoids in Northern Guangdong, SE China

This study presents whole-rock major, trace elements and Sr-Nd-Hf isotopic compositions, as well as zircon U-Pb geochronological data, for the peraluminous and aluminous granitoids in northern Guangdong Province, South China, in order to investigate their petrogenesis and tectonic implications. The Qingzhou granodiorites (458.5-455.4 Ma) are peraluminous (A/CNK = 1.05-1.96). They have relatively high initial Sr-87/Sr-86 ratios (I-Sr = 0.7087-0.7148), low epsilon(Nd)(t) values (-11.2 to -10.1) and a variety of zircon epsilon(Hf)(t) values in the range -13.4 to +4.81. By contrast, the Damaoshan granodiorites (458.1 Ma) are metaluminous (A/CNK = 0.79-0.94) in composition, with I-Sr values of 0.7083 to 0.7110, epsilon(Nd)(t) values of -7.92 to -5.28 and zircon epsilon(Hf)(t) values of -8.69 to -2.06. The Gaoshou quartz diorites (449 Ma) are metaluminous-peraluminous. Their I-Sr values vary from 0.7104 to 0.7111 with epsilon(Nd)(t) values from -9.64 to -8.63. Geochemical data and Sr-Nd-Hf isotope compositions indicate that the Qingzhou, Damaoshan and Gaoshou intrusions are primarily derived from the partial melting of metagreywackes, tonalitic rocks and amphibolite, respectively. The crustal materials in northern Guangdong, from top to bottom, consist of Paleozoic sequences, metasediments with a V-p of < 6.0 km/s, metaigneous rocks with a V-p of 6.3-6.7 km/s and amphibolite with a V-p of similar to 7.03 km/s.