Widespread Paleoproterozoic basement in the eastern Cathaysia Block : evidence from metasedimentary rocks of the Pingtan–Dongshan metamorphic belt, in southeastern China
Widespread Paleoproterozoic basement in the eastern Cathaysia Block : evidence from metasedimentary rocks of the Pingtan–Dongshan metamorphic belt, in southeastern China
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DOI：
10.1016/j.precamres.2016.09.017
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发表时间：
2016-10
影响因子：
3.8
通讯作者：
L. Shen;Jinhai Yu;S. O’Reilly;W. Griffin;Qin Wang
中科院分区：
文献类型：
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作者：
L. Shen;Jinhai Yu;S. O’Reilly;W. Griffin;Qin Wang
华南华夏地块以多期花岗质岩浆活动和世界级成矿作用而闻名，特别是W、Sn和稀土元素。虽然同位素资料表明广泛分布的火成岩起源于前寒武纪基底，但华夏地块基底岩石的露头很少。沿着中国东南沿海地区的平潭-东山变质带（PDMB）呈北东向，主要由大量的花岗岩和火山岩组成，少量为变质沉积岩。这些变质沉积岩被160-143 Ma花岗岩侵入或捕获。7个变质沉积岩的碎屑和变质锆石U-Pb定年结果表明，它们的原岩沉积时代为183 ~ 160 Ma，而不是以前提出的前泥盆纪。变质锆石定年表明，最重要的变质作用发生在约97 Ma，与A型花岗岩侵位和滨海地区镁铁质岩浆活动相一致，显示出拉张环境。相比之下，来自北方PDMB的碎屑锆石年龄谱显示出明显的新元古代和早古生代的年龄峰，以及晚古元古代和早中生代的，表明不同的物源。与华南造山带出露岩石的年龄和Hf同位素对比表明，这些沉积物中的陆源物质来自华夏陆块东部武夷山，东南华南造山带早古生代-晚中生代沉积岩的碎屑锆石年龄谱表明，中二叠世-早白垩世沉积岩中古元古代晚期（1.9- 1.8Ga）碎屑明显增加。与古元古代出露岩石锆石U-Pb-Hf同位素对比表明，华夏地块东部广泛存在古元古代基底。中二叠世以来抬升剥蚀，后被晚白垩世火山岩覆盖。古元古代基底的隆升可能是华夏地块东部晚古生代造山运动的结果。
The Cathaysia Block in South China Block (SCB) is famous for its polyphase granitic magmatism and world-class mineralization, especially W, Sn and REE. Although isotopic data suggest that widespread igneous rocks were derived from Precambrian basement, outcrops of the basement rocks are rare in the Cathaysia Block. Therefore, the distribution of the Archean-Paleoproterozoic basement beneath Cathaysia Block is still unclear.The northeastern-striking Pingtan–Dongshan metamorphic belt (PDMB) is located along the coastal region of southeastern China, and consists mainly of voluminous granites and volcanic rocks with minor metasedimentary rocks. These metasedimentary rocks were intruded or captured by 160–143 Ma granites. U–Pb dating of detrital and metamorphic zircons from seven metasedimentary rocks indicates that their protoliths were deposited between 183 Ma and 160 Ma, rather than pre-Devonian as previously proposed. Dating of metamorphic zircons suggests that the most important metamorphism took place atca97 Ma, consistent with emplacement of A-type granites and mafic magmatism in the coastal region, and implying an extensional setting.Age spectra of detrital zircons in samples from the middle and southern PDMB exhibit a bimodal distribution with abundant Late Paleoproterozoic and Early Mesozoic zircons. In contrast, age spectra of detrital zircons from the northern PDMB display pronounced Neoproterozoic and Early Paleozoic age peaks as well as Late Paleoproterozoic and Early Mesozoic ones, suggesting a different provenance. The comparisons of age and Hf-isotope with the exposed rocks of the SCB suggest that the terrigenous material in these sediments was sourced from the Wuyi terrane, in the eastern Cathaysia Block.The age spectra of detrital zircons from Early Paleozoic to Late Mesozoic sedimentary rocks in the SE SCB show that late Paleoproterozoic (1.9–1.8 Ga) detritus increases markedly in Middle Permian to Early Cretaceous sedimentary rocks. Comparison with zircon U–Pb–Hf isotopic data from exposed Paleoproterozoic rocks suggests that a Paleoproterozoic basement existed extensively beneath the eastern Cathaysia Block. It has been uplifted and eroded since Middle Permian time, and then covered by Late Cretaceous volcanic rocks. The uplift of the Paleoproterozoic basement was probably caused by the Late Paleozoic orogeny in the eastern Cathaysia Block.