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

Abstract

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 ⁸⁷Sr/⁸⁶Sr ratios (I_Sr = 0.7087–0.7148), low ε_Nd(t) values (–11.2 to –10.1) and a variety of zircon ε_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, ε_Nd(t) values of –7.92 to –5.28 and zircon ε_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 ε_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 ∼7.03 km/s.