Geodynamics of Late Paleozoic to Early Mesozoic Magmatism in South China: Insights from the Genesis of the Late Permian S-Type Granites in the Yunkai Massif

IF 1.5 4区 地球科学 Q2 GEOLOGY
Journal of Geology Pub Date : 2020-04-06 DOI:10.1086/708465
Long Qing, Yao-Hui Jiang, Fo-Guang Du
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引用次数: 5

Abstract

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.
华南晚古生代至早中生代岩浆活动的地球动力学——从云开地块晚二叠世S型花岗岩成因看
华南地区晚古生代花岗岩的研究较少。本文首次对云南云开岩体中两个晚二叠世花岗质岩体(那蓬和石村)进行了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Hf同位素、全岩元素地球化学及Sr-Nd同位素的原位测年。此外,我们还评估了它们的起源及其与华南晚古生代至中生代早期岩浆活动的地球动力学关系。那蓬岩体由堇青石和/或含石榴石的黑云母花岗岩组成,石村岩体由两种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,这两个深成岩体均侵位于二叠纪晚期,并含有丰富的继承锆石,年龄分布广泛,包括新太古代-古元古代、新元古代-寒武纪、奥陶纪-志留系、泥盆纪、石炭纪和二叠纪早期。含堇青石和/或石榴石的黑云母花岗岩是强过铝质的,并且具有比变质沉积岩的实验熔体更高的镁铁质。这两种云母和白云母花岗岩也是强过铝质的,但与变质沉积岩的实验熔体具有相似的镁铁质。所有花岗岩都具有高的初始87Sr/86Sr、负的εNd(t)和εHf(t)(原位锆石)。所研究的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,是由古特提斯洋东部地幔区至大陆碰撞带正常下地壳深度内的俯冲海洋沉积物部分熔融形成的。我们的新数据表明,纳棚和石村花岗岩的起源可能标志着中印地块和华南地块之间的大陆碰撞的开始,同时在晚二叠世开始时东部古地中海的初步封闭。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Geology
Journal of Geology 地学-地质学
CiteScore
3.50
自引率
5.60%
发文量
0
审稿时长
3 months
期刊介绍: One of the oldest journals in geology, The Journal of Geology has since 1893 promoted the systematic philosophical and fundamental study of geology. The Journal publishes original research across a broad range of subfields in geology, including geophysics, geochemistry, sedimentology, geomorphology, petrology, plate tectonics, volcanology, structural geology, mineralogy, and planetary sciences. Many of its articles have wide appeal for geologists, present research of topical relevance, and offer new geological insights through the application of innovative approaches and methods.
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