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 εNd(t), and εHf(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.

中文翻译：

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华南晚古生代至早中生代岩浆作用地球动力学——从云开地块晚二叠世S型花岗岩成因看

晚古生代花岗岩在华南地区鲜见报道。我们提供了第一个详细的锆石激光烧蚀电感耦合等离子体质谱 (LA-ICP-MS) U-Pb 定年和原位 Hf 同位素和全岩元素地球化学和 Sr-Nd 同位素数据，用于两个晚二叠世花岗岩岩体（那鹏和石村）最近在华南云开地块发现。此外，我们评估了它们的起源和与华南晚古生代至早中生代岩浆作用的地球动力学的关系。那鹏岩体由含堇青石和/或含石榴石的黑云母花岗岩组成，石村岩体由二云母花岗岩和白云母花岗岩组成。详细的 LA-ICP-MS 锆石 U-Pb 定年表明，这两个岩体都在晚二叠世就位，并且都含有丰富的具有年龄分布的遗传锆石，包括新太古代-古元古代、新元古代-寒武纪、奥陶纪-志留纪、泥盆纪、石炭纪和早二叠纪。含堇青石和/或石榴石的黑云母花岗岩具有强烈的过铝质并且比变质沉积岩的实验熔体具有更高的镁铁质。双云母和白云母花岗岩也都是强过铝质的，但与变沉积岩的实验熔体具有相似的镁铁质。所有花岗岩具有高初始 87Sr/86Sr、负值 εNd(t) 和 εHf(t)（原位锆石）。所研究花岗岩的详细岩石学和地球化学特征表明它们是S型花岗岩，是由东古特提斯洋俯冲大洋沉积物在大陆碰撞带的地幔区域到正常下地壳深处的部分熔融形成的。