Petrogenesis Of Late Mesozoic Granitoids And Evalution Of Metallogenic Potential In Eastern Guangdong,Coastal Area Of SE China

The eastern Guangdong Province is located at southwestern of the continental margin of South China,and is characterized by widespread Late Mesozoic magmatism and mineralization,especially W–Sn and Cu–Au–Mo deposits.For lack of fundamental geological research,many comprehensive study work needs to be done,such as the timing of magmatic events,petrogenesis,and tectonic setting.In this study,we present precise zircon U–Pb ages,Hf–O isotopes,trace elements,together with whole–rock element geochemistry and Sr–Nd isotopes of the Donggang,Liuzhoushan,Xinwei,Sanrao felsic intrusions,and Zhongqiuyang volcanic rocks to constrain their petrogenesis and crust-mantle interaction,and evaluate the implication for Cu-Au-Mo mineralization.In combination with previous studies,we proposed a geodynamic model for Late Mesozoic magmatic events in the Southeast Coastal magmatic belt aiming to reconstruct the Late Mesozoic tectono-magmatic evolution in South China.The following achievements and conclusions have been obtained:1)Redefinition of the Late Mesozoic magmatic events of Eastern Guangdong,and first recognize the late Early Cretaceous magmatism?102¹06 Ma?in the Eastern Guangdong Province.2)The Xinwei and Sanrao intrusions are similar to the Luoboling ore-bearing granodioritic porphyries in time and space as well as similar elemental and isotopic characteristics,indicating that the late Early Cretaceous granodioritic intrusions may have Cu–Mo–Au mineralization potential in the eastern Guangdong Province,southwestern of the Southeast Coastal metallogenic belt.3)The Zhongqiuyang rhyolitic tuffs are affinitive to A-type granite with zircon U-Pb age of 164.7±1.3 Ma,which is nearly coeval with the metallogenic age of the Zhongqiuyang copper polymetallic deposit,suggesting that the Middle Jurassic porphyry Cu polymetallic deposits in Eastern Guangdong formed in the subduction-related tectonic setting.4)Geochemical and Sr–Nd–Hf–O isotopic data indicate that the granitoids were derived from a hybridization source:basaltic magmas derived from depleted mantle underplated beneath lower continental crust,and contributed as both a heat source inducing crustal melting and a source of materials that mixed with the local crustal magmas in increasing proportions over time.All of the studied rocks show Nd-Hf-O isotopic features from isotopic enrichment to depletion with increasing?_Nd?t?and?_Hf?t?values and decreasing?¹⁸O values over time,revealing the gradual intensive process of crust-mantle interaction.5)The late Early Cretaceous magmatic event in eastern Guangdong represents a positive response of large-scale lithosphere extension and thinning.Mantle and crustal derived magmas mixing gradually increase northeastward,and a wide of granitic intrusions and related deposits controlled by pull-apart basins along the continental margin in SE China,which is likely triggered by the changing subduction direction of the Paleo-Pacific plate from oblique subduction to parallel to the continental margin during the Early Cretaceous.