An example of Phanerozoic continental crustal growth: The West Junggar Orogenic Belt, Northwest China
An example of Phanerozoic continental crustal growth: The West Junggar Orogenic Belt, Northwest China
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DOI：
10.1016/j.lithos.2020.105745
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发表时间：
2020-12
期刊：
影响因子：
3.5
通讯作者：
Bo Zheng;Bao-Fu Han;Zeng-Zhen Wang;Bo Liu;L. X. Feng
中科院分区：
文献类型：
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作者：
Bo Zheng;Bao-Fu Han;Zeng-Zhen Wang;Bo Liu;L. X. Feng
一般认为，大陆地壳生长主要发生在前寒武纪，而中生代的生长似乎微不足道。西准噶尔造山带是中亚造山带的重要组成部分，在中生代经历了显著的地壳生长。683个全岩Sr-Nd同位素数据的汇编表明，WJOB具有不同的地壳结构和/或从邻近地区的组成。WJOB岩浆岩具有亏损Sr-Nd同位素特征，初始87 Sr/86 Sr比值为0.7022 ~ 0.7060，εNd（t）值为+3.0 ~+9.2，Nd模式年龄为0.9 ~ 0.3Ga。这些特征明显不同于南邻天山造山带（天山）和北邻阿尔泰造山带（阿尔泰）的Sr-Nd同位素大幅度变化。西太平洋陆壳的生长是在西太平洋南部埃迪卡拉-奥陶纪唐巴勒-玛依勒弧、西太平洋北方志留纪-泥盆纪Boshchekul-Chingiz弧和早石炭世Zharma-Saur弧的洋壳向南俯冲过程中，先存的幼年地壳和地幔楔的转化的结果。随后在晚石炭纪至二叠纪期间，在整个WJOB的后碰撞环境中加入了幔源物质，很少或根本没有前寒武纪地壳的参与。这种陆壳生长的模式在WJOB是显着不同的相邻的天山和阿尔泰，以及海西造山带在法国地块中央，其中前寒武纪地壳物质的参与。因此，WJOB可能是世界各地中生代大陆地壳生长的一个很好的例子。
It is generally accepted that continental crustal growth occurred principally during Precambrian, whereas the Phanerozoic growth seems insignificant. However, the West Junggar Orogenic Belt (WJOB), a key part of Central Asian Orogenic Belt in NW China, underwent significant crustal growth during Phanerozoic. A compilation of 683 whole-rock Sr–Nd isotopic data shows that WJOB has different crustal structures and/or compositions from adjacent areas. All igneous rocks in WJOB are characterized by depleted Sr–Nd isotopes, with initial87Sr/86Sr ratios from 0.7022 to 0.7060, εNd (t) values from +3.0 to +9.2, and Nd model ages from 0.9 to 0.3 Ga. These features are obviously different from the large variations in Sr–Nd isotopes in adjacent Tianshan Orogenic Belt (Tianshan) to the south and Altay Orogenic Belt (Altay) to the north. The continental crustal growth in WJOB resulted from the transformation of pre-existing juvenile crust and mantle wedge during the successively southward subduction of oceanic lithosphere beneath the Ediacaran to Ordovician Tangbale-Mayile arc in southern WJOB, the Silurian to Devonian Boshchekul-Chingiz arc and Early Carboniferous Zharma-Saur arc in northern WJOB, followed by the addition of mantle-derived materials in a post-collisional setting throughout WJOB during Late Carboniferous to Permian, with little or no involvement of Precambrian crust. Such a pattern of continental crustal growth in WJOB is significantly different from those of the adjacent Tianshan and Altay as well as the Hercynian Orogenic Belt in French Massif Central, where Precambrian crustal materials are largely involved in. Thus, WJOB would probably be a good example of Phanerozoic continental crustal growth around the world.