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Late Paleozoic granites have rarely been reported in South China. We present the first detailed zircon laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating and in situ Hf isotopic and whole-rock element geochemical and Sr-Nd isotopic data for two late Permian granitic plutons (Napeng and Shicun) recently identified in the Yunkai massif, South China. In addition, we assess their origin and relationship to the geodynamics of late Paleozoic to early Mesozoic magmatism in South China. The Napeng pluton consists of cordierite- and/or garnet-bearing biotite granites, and the Shicun pluton is composed of two-mica granites and muscovite granites. Detailed LA-ICP-MS zircon U-Pb dating shows that both plutons were emplaced in the late Permian and contain abundant inherited zircons with a spread of ages, including Neoarchean-Paleoproterozoic, Neoproterozoic-Cambrian, Ordovician-Silurian, Devonian, Carboniferous, and early Permian. The cordierite- and/or garnet-bearing biotite granites are strongly peraluminous and have higher maficity than experimental melts of metasedimentary rocks. Both the two-mica and muscovite granites are also strongly peraluminous but have similar maficity to experimental melts of metasedimentary rocks. All the granites have high initial 87Sr/86Sr, negative ε Nd(t), and ε Hf(t) (in situ zircon). Detailed petrographic and geochemical characteristics of the studied granites suggest that they are S-type granites and were formed by partial melting of subducted oceanic sediments of the eastern Paleo-Tethys Ocean within the depth of mantle region to normal lower crust in the continental collision zone. Our new data suggest that the origin of the Napeng and Shicun granites might mark the onset of the continental collision between the Indochina and South China Blocks with the initial closure of the eastern Paleo-Tethys Ocean at the beginning of the late Permian. [ABSTRACT FROM AUTHOR]

A-type granites are widespread in most orogenic belts, and their petrogenesis has played an important role in reconstructing orogenic events. However, their sources, even today, are a subject of considerable controversy. At least four models have been proposed for their formation, namely, melting of a previously melted source, fractionation of basaltic magma, anatexis of crustal igneous sources, and magma mixing. Here we present Early Jurassic A-type granites in southeast (SE) China as an example of a shallow (ca. 15-20-km depth), igneous, crust-derived A-type granite. We present detailed laser ablation ICP-MS zircon U-Pb dating and major- and trace-element and Sr-Nd isotopic data for these granites and assess their origin and relationship to the geodynamics of the late Mesozoic extensive magmatism in SE China. The associated granites include the Zhaibei, Keshubei, Zhulanbu, and Guangze plutons, which were emplaced during the interval 191-188 Ma and occur in a northeast-trending belt, parallel to the present coastline. They consist mainly of syenogranite and alkali-feldspar granite, with minor monzogranite, in which biotite and amphibole are anhedral and interstitial to both feldspar and quartz. The granites have high SiO2 (71.3-78.4 wt%) and K2O + Na2O and low Al2O3 and CaO contents, with high (K2O + Na2O)/Al2O3 ratios. They are enriched in rare earth elements (except Eu) and depleted in Ba and Sr. They display 10,000Ga/Al > 2.6 and Zr + Nb + Ce + Y > 350 ppmand have high zircon saturation temperatures (up to 900°C). Their Sr-Nd isotopic compositions (initial 87Sr/86Sr ranges from 0.7070 to 0.7283 and #949;Nd(T) ranges from 0.1 to -10.2) are variable but consistent with those of the early Paleozoic granitoids in SE China. Geochemical data suggest that the Early Jurassic A-type granites were derived by dehydration melting of early Paleozoic hornblende- and biotite-bearing granitoids in the middle crust (ca. 15-20 km), induced by intraplating of mantle-derived basaltic magmas. We further suggest that they formed in an extensional tectonic regime caused by slab break-off of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]