Petrogenesis of the late Early Cretaceous granodiorite – Quartz diorite from eastern Guangdong, SE China: Implications for tectono–magmatic evolution and porphyry Cu–Au–Mo mineralization

Abstract

Comprehensive petrological, zircon U–Pb dating, Hf–O isotopes, whole rock geochemistry and Sr–Nd isotopes data are presented for the Xinwei and Sanrao intrusions in the eastern Guangdong Province, Southeast (SE) China, with an aim to constrain the petrogenesis, tectono-magmatic evolution and evaluate the implication for porphyry Cu–Au–Mo mineralization. The Xinwei intrusion is composed of granodiorite and quartz diorite, whilst the Sanrao intrusion consists of granodiorite. Zircon U–Pb ages show that both intrusions were emplaced at ca. 106–102Ma. All rocks are metaluminous to weakly peraluminous, high-K calc-alkaline in composition, and they are characterized by LREEs enrichment, depletion in Nb, Ta, P, and Ti, and strongly fractionated LREEs to HREEs. The initial 87Sr/86Sr ratios range from 0.7055 to 0.7059, and εNd(t) values range from −3.9 to −3.0. Together with the relatively high εHf(t) values (−3.2 to 3.3) and low δ18O values (4.9‰ to 6.6‰), these data suggest that the Xinwei and Sanrao intrusions were derived from a mixed source: including the mantle-derived mafic magmas and lower continental crustal magmas. Fractional crystallization played an important role in the magmatic evolution of the Xinwei and Sanrao intrusions. The elemental and isotopic compositions of the Xinwei and Sanrao intrusions, as well as the high water content and oxidation state of their parental magmas, are similar to those of the ore-bearing granodiorites of the Luoboling porphyry Cu–Mo deposit in the Fujian Province, neighbouring east to the Guangdong Province, indicating that the late Early Cretaceous granodioritic intrusions in the eastern Guangdong Province may also have Cu–Au–Mo mineralization potential. The late Early Cretaceous magmatic event is firstly reported in eastern Guangdong, and represents a positive response of large-scale lithosphere extension and thinning, triggered by the changing subduction direction of the Paleo-Pacific plate from oblique subduction to parallel to the continental margin during the Early Cretaceous.