Melt evolution of crustal anatexis recorded by the Early Paleozoic Baiyunshan migmatite-granite suite in South China
Melt evolution of crustal anatexis recorded by the Early Paleozoic Baiyunshan migmatite-granite suite in South China
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华南早古生代白云山混合岩-花岗岩套记录的地壳深熔熔融演化
DOI：
10.1016/j.lithos.2019.02.020
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发表时间：
2019-05
期刊：
影响因子：
3.5
通讯作者：
Wu-Bin Yang
中科院分区：
文献类型：
--
作者：
Pengpeng Yu;Yuzhi Zhang;Yongzhang Zhou;Roberto F. Weinberg;Yi Zheng;Wu-Bin Yang
摘要 华南地块早古生代造山运动伴随着地壳深熔作用，大量的花岗岩和混合岩表明。我们报道的白云山新元古代黑云母片麻岩中的混合岩-花岗岩套，直接记录了深熔熔体的形成、分凝和萃取过程。混合岩中隐色体的结晶年代约为 100 年。通过锆石 U-Pb 分析，侵入混合岩的花岗岩脉的年代约为 438 Ma。第433章岩石学和地球化学数据表明，深熔作用是由于黑云片麻岩在低温和低压条件下（约 650–700 °C 和约 4–6 kbar）的流体熔融所致。隐色体主要由斜长石+钾长石+石英组成，具有正Eu异常（Eu/Eu* = 1.70–2.89），这归因于长石堆积。这意味着一些熔体已经从混合岩中提取出来，并且花岗岩脉很可能代表这些提取的熔体，因为它们具有与无色体相似的微量元素组成和锆石Lu Hf同位素。通过质量平衡计算揭示了产生混合岩和花岗岩脉的部分熔融和化学分异程度。计算表明，初级熔体可能是白云山黑云片麻岩约 40 wt% 熔融的结果，而分馏熔体（约 24–26 wt%）是从更深的部分提取出来的，形成了侵入岩脉。结合区域测年结果，武夷-云开造山带地壳深熔开始时间不晚于465 Ma，持续时间>55 Myr。花岗岩和混合岩的产生是水熔熔融的结果，并与提供给中下地壳的地幔岩浆的额外热量有关。
Abstract The Early Paleozoic orogeny in the South China Block was accompanied by crustal anatexis, as indicated by the voluminous granites and migmatites. Here we report on the migmatite-granite suite within the Neoproterozoic biotite gneiss of the Baiyunshan Domain, which has directly recorded the process of anatectic melt formation, segregation and extraction. The crystallization of leucosome in migmatite was dated at ca. 438 Ma by U–Pb analysis of zircon, and the granitic vein that intruded the migmatite was dated at ca. 433 Ma. Petrological and geochemical data suggest that anatexis resulted from fluid-present melting of the biotite gneiss at low temperature and pressure conditions (~650–700 °C and ~4–6 kbar). The leucosome mainly consists of plagioclase + K-feldspar + quartz and has positive Eu anomaly (Eu/Eu* = 1.70–2.89), which is attributed to feldspar accumulation. This means that some melt has been extracted from the migmatite, and the granitic veins are likely to represent these extracted melts since they have similar trace element compositions and zircon Lu Hf isotopes to the leucosomes. The degree of partial melting and chemical differentiation to generate the migmatite and the granitic veins are revealed by mass balance calculations. Calculations suggest that the primary melt could be a result of ~40 wt% melting of the Baiyunshan biotite gneiss, and fractionated melt (~24–26 wt%) was extracted from the deeper sections to form the intrusive veins. Combined with regional dating results, it is suggested that the crustal anatexis in the Wuyi-Yunkai orogen started no later than 465 Ma with a duration of >55 Myr. Generation of the granitoids and migmatites are a result of water-fluxed melting and linked to extra heat from mantle magmas provided to the middle-lower crust.
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影响因子：
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作者：
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DOI：
10.1007/s11430-008-0078-4
发表时间：
2008-07
期刊：
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影响因子：
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作者：
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DOI：
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发表时间：
2007
期刊：
Geological Journal of China Universities
影响因子：
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