Crust–mantle interaction during Early Jurassic subduction of Neo-Tethyan oceanic slab: Evidence from the Dongga gabbro–granite complex in the southern Lhasa subterrane, Tibet
Crust–mantle interaction during Early Jurassic subduction of Neo-Tethyan oceanic slab: Evidence from the Dongga gabbro–granite complex in the southern Lhasa subterrane, Tibet
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早侏罗世新特提斯洋板俯冲过程中的壳幔相互作用——来自西藏拉萨地南部东嘎辉长岩杂岩体的证据
DOI：
10.1016/j.lithos.2017.09.018
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发表时间：
2017-11
期刊：
影响因子：
3.5
通讯作者：
Jiao-Long Zhao
中科院分区：
文献类型：
--
作者：
Rui-Qiang Wang;Jian-Sheng Qiu;Si-Bin Yu;Jiao-Long Zhao
在活动大陆边缘形成的辉长岩-花岗岩杂岩为研究酸性岩浆和基性岩浆之间的成因关系提供了极好的机会，并为壳幔相互作用提供了重要的见解。本文通过对拉萨南缘东嘎辉长岩-花岗岩杂岩的岩石学、矿物学、全岩地球化学、Sr-Nd同位素、锆石U-Pb和Hf同位素研究，阐明了东嘎辉长岩-花岗岩杂岩的岩石成因，揭示了与新特提斯洋片向北俯冲有关的壳幔相互作用过程。东嘎杂岩主要由英云闪长岩和花岗闪长岩组成，含有丰富的镁铁质微粒包体和少量角闪辉长岩。LA-ICP-MS锆石U-Pb定年结果表明，角闪辉长岩的结晶年龄为178.0 ± 1.5Ma和192.3 ± 1.5Ma，英云闪长岩和MMEs的结晶年龄分别为178.1 ± 1.7Ma和178.8 ± 1.8Ma。辉长岩具有低SiO2、低Na 2 O + K2 O和高Mg#值的地球化学特征。这些辉长岩富含大离子亲石元素（LILE;例如，Ba、K、Pb和Sr）和轻稀土元素（LREE），并且贫高场强元素（HFSE;例如，Nb、Ta、P、Zr和Hf）。英云闪长岩是亚碱性和metaluminous的，也具有富集LILE和LREE和HFSE亏损的特点。的MME是二氧化硅穷人和碱丰富，并具有广泛的相似的微量元素签名的主机英云闪长岩。辉长岩、英云闪长岩和MMEs具有相似的初始87 Sr/86 Sr比值（ISr）（0.7035-0.7036）和正εNd（t）值（+5.3-+6.8）。角闪辉长岩的锆石εHf（t）值（+ 14.0 ~+ 18.2）略高于英云闪长岩的ε Hf（t）值（+ 11.4 ~+ 15.0），但与混合微细粒岩的ε Hf（t）值（+ 14.4 ~+ 18.2）相近。东嘎辉长岩-花岗岩杂岩的岩石学、地球化学和同位素特征表明，拉萨南部早侏罗世处于活动大陆边缘环境。辉长岩是由俯冲的新特提斯洋板释放的含水流体交代的亏损地幔楔的含水部分熔融形成的。英云闪长岩和MMEs是由与辉长岩有关的镁铁质岩浆和新生下地壳重熔产生的长英质岩浆混合而成。幔源岩浆的底侵作用以及由此产生的地壳熔融和岩浆混合作用发生在早侏罗世新特提斯洋板俯冲过程中。幔源岩浆不仅为下地壳的熔融提供了大量的热量，而且与壳源岩浆混合形成了花岗岩类和MMEs。
Gabbro–granite complexes that form in active continental margins provide an excellent opportunity to investigate the genetic relationships between acid and basic magmas and offer important insights into crust–mantle interaction. In this paper, we present detailed petrographic, mineralogical, whole-rock geochemical, Sr–Nd isotopic, zircon U–Pb, and Hf isotopic data for the Dongga gabbro–granite complex of the southern Lhasa subterrane, with the aim of elucidating the petrogenesis of these rocks and gaining insights into the processes of crust–mantle interaction associated with the northward subduction of the Neo-Tethyan oceanic slab. The Dongga complex consists predominantly of tonalite and granodiorite with abundant mafic microgranular enclaves (MMEs) and lesser amounts of hornblende gabbro. LA–ICP–MS zircon U–Pb dating yields crystallization ages of 178.0 ± 1.5 Ma and 192.3 ± 1.5 Ma for the hornblende gabbros, and 178.1 ± 1.7 Ma and 178.8 ± 1.8 Ma for the tonalites and MMEs, respectively. Geochemically, the gabbroic rocks have low SiO2and Na2O + K2O concentrations and high Mg# values. These gabbroic rocks are enriched in large ion lithophile elements (LILEs; e.g., Ba, K, Pb, and Sr) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, P, Zr, and Hf). The tonalites are subalkaline and metaluminous and are also characterized by an enrichment of LILEs and LREEs and a depletion of HFSEs. The MMEs are silica poor and alkali rich and have broadly similar trace element signatures to those of the host tonalites. The gabbroic rocks, tonalites, and MMEs have similar initial87Sr/86Sr ratios (ISr) of 0.7035–0.7036 and positive εNd(t) values of + 5.3 to + 6.8. However, zircon εHf(t) values from the hornblende gabbros (+ 14.0 to + 18.2) are somewhat higher than those of the tonalites (+ 11.4 to + 15.0) but are similar to the MMEs (+ 14.4 to + 18.2). The combined petrological, geochemical, and isotopic features of the Dongga gabbro–granite complex suggest that the southern Lhasa subterrane was located in an active continental margin setting during the Early Jurassic. The gabbroic rocks were generated by the hydrous partial melting of a depleted mantle wedge metasomatized by aqueous fluids released from the subducted Neo-Tethyan oceanic slab. The tonalites and MMEs were produced by the mixing of mafic magmas related to the gabbroic rocks and felsic magmas derived from the remelting of the newly formed juvenile lower crust. The underplating of mantle-derived magmas and the resulting crustal melting and magma mixing occurred during the Early Jurassic subduction of the Neo-Tethyan oceanic slab. The mantle-derived magmas not only provided substantial heat to melt the lower crust but also mixed with the crust-derived magmas to form granitoids and MMEs.
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影响因子：
3.5
作者：
Lin Ma;Qiang Wang;Zheng‐Xiang Li;D. Wyman;Zi-qi Jiang;Jin-Hui Yang;Guo-Ning Gou;H. Guo
通讯作者：
Lin Ma;Qiang Wang;Zheng‐Xiang Li;D. Wyman;Zi-qi Jiang;Jin-Hui Yang;Guo-Ning Gou;H. Guo
影响因子：
6.1
作者：
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通讯作者：
Yuanku Meng;Zhiqin Xu;M. Santosh;Xuxuan Ma;Xijie Chen;G. Guo;Fei Liu
影响因子：
64.8
作者：
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通讯作者：
Charles E. Lesher
重温泽东地体：新特提斯洋内的洋内弧还是亚洲活动大陆边缘的一部分？
影响因子：
3
作者：
Chuan-Zhou Liu;Fu-Yuan Wu;Wei-Qiang Ji;Jian-Gang Wang
通讯作者：
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影响因子：
3.5
作者：
J. Clemens;V. Wall
通讯作者：
J. Clemens;V. Wall