The Xigaze ophiolite: fossil ultraslow-spreading ocean lithosphere in the Tibetan Plateau
The Xigaze ophiolite: fossil ultraslow-spreading ocean lithosphere in the Tibetan Plateau
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日喀则蛇绿岩：青藏高原超慢速扩张海洋岩石圈化石
DOI：
10.1144/jgs2020-208
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发表时间：
2020-11
影响因子：
2.7
通讯作者：
Yang Xu
中科院分区：
文献类型：
--
作者：
Tong Liu;Chuan-Zhou Liu;Fu-Yuan Wu;Henry J. B. Dick;Wen-Bin Ji;Chang Zhang;Wei-Qi Zhang;Zhen-Yu Zhang;Yang Xu
蛇绿岩（古海洋岩石圈）和现代海洋的地壳和地幔是非常多样的。超低速扩张洋脊的沿轴形态和下地壳增生与快速扩张洋脊的沿轴形态和下地壳增生有着根本的不同，这对于理解地壳增生如何随扩张速率和岩浆供应而变化至关重要。超低速扩张的山脊提供了蛇绿岩的类似物，以确定那些可能在类似条件下形成的山脊。因此，对现代海洋岩石圈和蛇绿岩的平行研究可以为两者的起源和成因提供独特的信息。本文报道了青藏高原日喀则蛇绿岩的构造和岩石学研究结果，并与超低速扩张的西南印度洋脊的形态和深钻结果进行了对比。日喀则蛇绿岩具有完整但横向不连续的地壳，离散的闪长岩脉和岩床切割地幔和下地壳。辉长岩单元较薄（c. 350米），并显示向上循环的化学变化，支持幕式和间歇性的岩浆供应。 这些特征与现代超低速扩张海脊的高度集中的岩浆活动和低岩浆预算相当。因此，我们认为日喀则蛇绿岩代表了超低速扩张海洋岩石圈的陆上类似物。补充资料：矿物主量元素成分单点分析及平均成分（wt. %）关于吉顶辉长岩剖面、日喀则蛇绿岩的详细资料，请访问www.example.com
The crust and mantle both in ophiolites (fossil ocean lithosphere) and in modern oceans are enormously diverse. Along-axis morphology and lower crustal accretion at ultraslow-spreading ocean ridges are fundamentally different from those at faster-spreading ridges, and are critical to understanding how crustal accretion varies with spreading rate and magma supply. Ultraslow-spreading ridges provide analogues for ophiolites, to identify those that may have formed under similar conditions. Parallel studies of modern ocean lithosphere and ophiolites therefore can uniquely inform the origin and genesis of both. Here we report the results of structural and petrological studies on the Xigaze ophiolite in the Tibetan Plateau, and compare it with the morphology and deep drilling results at the ultraslow-spreading Southwest Indian Ridge. The Xigaze ophiolite has a complete but laterally discontinuous crust, with discrete diabase dykes and sills cutting both mantle and lower crust. The gabbro units are thin (c. 350 m) and show upward cyclic chemical variations, supporting for an episodic and intermittent magma supply. These features are comparable with the highly focused magmatism and low magma budget at modern ultraslow-spreading ridges. Thus we suggest that the Xigaze ophiolite represents an on-land analogue of ultraslow-spreading ocean lithosphere. Supplementary material: Single-spot analysis and average compositions for mineral major element compositions (wt.%) of the Jiding gabbro section, Xigaze ophiolite are available at https://doi.org/10.17632/dtzpmwkscp.1
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通讯作者：
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