Role of deep-Earth water cycling in the growth and evolution of continental crust: Constraints from Cretaceous magmatism in southeast China
Role of deep-Earth water cycling in the growth and evolution of continental crust: Constraints from Cretaceous magmatism in southeast China
复制标题
地球深部水循环在大陆地壳生长演化中的作用：中国东南部白垩纪岩浆作用的制约
DOI：
10.1016/j.lithos.2017.12.028
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发表时间：
2018
期刊：
影响因子：
3.5
通讯作者：
Yang Xuemei
中科院分区：
文献类型：
--
作者：
Li Zhen;Wang Xuan-Ce;Wilde Simon A.;Liu Liang;Li Wu-Xian;Yang Xuemei
中国东南部晚中生代火成岩省为认识控制显生宙大陆地壳生长演化的过程提供了极好的机会。本文报道了中国东南部平潭和通安杂岩中花岗岩类和伴生辉长岩的岩石学、全岩地球化学和同位素数据，以及锆石U-Pb-Lu-Hf同位素数据。结果表明，早白垩世岩浆岩以幼年Nd-Hf同位素为主，而晚白垩世岩浆岩则表现出较弱的放射性Nd-Hf同位素特征。Nd-Hf同位素系统与含水矿物丰度降低和锆石饱和温度升高有关。整理的锆石Hf - o数据表明，117 ~ 116 Ma花岗岩锆石δ18O值从地幔值（接近5.3‰）到低至3.9‰不等，但初始εHf（εHf(t)）值以正为主。105 ~ 98 Ma岩石的锆石δ18O值在类地幔（6.5‰~ 4.5‰）范围内，但以负εHf(t)值为主。约87 Ma岩石的锆石颗粒εHf(t)值为正（+ 9.8 ~ + 0.7），δ18O值范围较大（6.3‰~ 3.5‰）。Hf-Nd-O同位素组成的变化与岩浆含水量丰度的下降有关，说明水熔融作用产生了大规模的花岗质岩浆活动。地球深部水循环为含水玄武岩底板、大陆地壳熔融和岩浆分异提供了一种替代或额外的机制，以提供挥发物（例如H2O）。
The late Mesozoic igneous province in southeast China provides an excellent opportunity to understand the processes that controlled the growth and evolution of Phanerozoic continental crust. Here we report petrological, whole-rock geochemical and isotopic data, andin situzircon U–Pb–Lu–Hf isotopic data from granitoids and associated gabbros in the Pingtan and Tong'an complexes, southeast China. Through combining the new results with published datasets in southeast China, we show that the Early Cretaceous magmatic rocks are dominated by juvenile Nd–Hf isotopic compositions, whereas the Late Cretaceous ones display less radiogenic Nd–Hf isotope signatures. Furthermore, Nd–Hf isotope systematics are coupled with decreasing abundance of hydrous minerals and an increase of zircon saturation temperatures. Compiled zircon Hf–O data indicates that the 117–116 Ma granites have zircon δ18O values ranging from mantle values (close to 5.3‰) to as low as 3.9‰, but with dominantly positive initial epsilon Hf (εHf(t)) values. Zircon grains from 105 to 98 Ma rocks have δ18O values plotting within the mantle-like range (6.5‰ − 4.5‰), but mainly with negative εHf(t) values. Zircon grains from ca. 87 Ma rocks have positive εHf(t) values (+ 9.8 to + 0.7) and a large range of δ18O values (6.3‰ − 3.5‰). The variations in Hf–Nd–O isotopic compositions are correlated with decreasing abundance of magma water contents, presenting a case that water-fluxed melting generated large-scale granitic magmatism. Deep-Earth water cycling provides an alternative or additional mechanism to supply volatiles (e.g., H2O) for hydrous basaltic underplating, continental crustal melting, and magmatic differentiation.