Hot Paleocene-Eocene Gangdese arc: Growth of continental crust in southern Tibet
Hot Paleocene-Eocene Gangdese arc: Growth of continental crust in southern Tibet
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热古新世-始新世冈底斯岛弧：藏南大陆地壳的生长
DOI：
10.1016/j.gr.2017.12.011
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发表时间：
2018-10
影响因子：
6.1
通讯作者：
Qu Wen-Jun
中科院分区：
文献类型：
--
作者：
Zhou Li-min;Wang Rui;Hou Zeng-qian;Li Chao;Zhao Hong;Li Xin-Wei;Qu Wen-Jun
冈底斯岩浆带全长1600公里，发育广泛的古新世—始新世I型侵入岩和同时代火山岩序列，可分为I组（-69~53 Ma）、II组（-53~49 Ma）、III组（-49~43 Ma），分别对应新特提斯板片回退、新特提斯板片断裂和正在进行的印度-亚洲碰撞。这三组岩浆在地球化学和同位素组成方面表现出显着的变化，这提供了藏南大陆地壳生长的信息。冈底斯带最丰富的岩浆活动发生在53-49Ma期间。高锆石饱和温度（高达800℃）和锆石中Ti温度（高达980℃）估计表明在53-49 Ma期间存在一段热异常时期。从～53Ma开始，岩浆K20含量增加，锆石Th/U比值、Y、Yb含量下降。第 11 族锆石具有最异质的 Lif 同位素组成（ε Hf-(t) = 5.3 至 15.1）。这些都是弧内软流圈地幔进入、广泛的地壳熔化和岩浆混合的证据。这一时期的岩浆底侵作用是大陆地壳生长的主要机制。随着印度-亚洲碰撞的进行，III组岩浆显示出较高的Th/Y和La/Yb比值和IC20含量，但Tzr和T(ti-zr)值明显较低(大多低于750 CC)。这些特征表明早期弧残渣的水熔熔融发生在大陆地壳生长的晚期。此阶段地壳已增厚并接近成熟。这项研究对于认识造山带大陆地壳的生长具有重要意义。 (C) 2018 年国际冈瓦纳研究协会。由 Elsevier B.V. 出版。保留所有权利。
The 1600 km-long Gangdese magmatic belt features extensive Paleocene-Eocene I-type intrusive rocks and coeval volcanic successions, which can be divided into Group I (-69-53 Ma), Group II (-53-49 Ma), and Group Ill (-49-43 Ma), corresponding to Neo-Tethyan slab rollback, Neo-Tethyan slab breakoff, and ongoing Indian Asian collision, respectively. The magmas from these three groups show significant variations in geochemical and isotopic compositions, which provide the information of the growth of continental crust in southern Tibet. The most voluminous magmatism in the Gangdese belt occurred during-53-49 Ma. High zircon saturation temperature (up to 800 C) and Ti in zircon temperature (up to 980 C) estimations suggest there is a period of thermal anomaly during-53-49 Ma. Starting from-53 Ma, magmas have increased K20 contents, and their zircons have decreased Th/U ratios, and Y and Yb contents. Zircons from Group 11 have the most heterogeneous lif isotopic compositions (epsilon Hf-(t) = 5.3 to 15.1). These are evident of ingress of asthenosphere mantle in the arc, extensive crustal melting, and magma mixing. Magma underplating during this time is the main mechanism for the growth of continental crust. With the Indian-Asian collision going on, the magmas in Group Ill show high Th/Y and La/Yb ratios and IC20 contents, but significantly low Tzr and T(ti-zr) values (mostly below 750 CC). These features suggest the water-fluxed melting of early arc residues occurred in the late stage of growth of continental crust. The crust has been thickened and nearly mature at this stage. This study has great implication on understanding of growth of continental crust in orogenic belts. (C) 2018 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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6.1
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影响因子：
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