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首页> 外文期刊>Gondwana research: international geoscience journal >Differentiating advancing and retreating subduction zones through regional zircon Hf isotope mapping: A case study from the Eastern Tianshan, NW China
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Differentiating advancing and retreating subduction zones through regional zircon Hf isotope mapping: A case study from the Eastern Tianshan, NW China

机译：通过Zircon HF同位素测绘来区分推进和撤退俯冲区：北天山东部的案例研究

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摘要

Advancing and retreating subduction zones at convergent margins, primary sites of continental crust growth and loss, are the cornerstones of tectonic evolution of accretionary orogens. Yet, distinguishing the tectonic mode (advancing, retreating, or switching) of subduction zones in fossil orogens is not always straightforward due to the scarcity of strong evidence. As an alternative approach, we utilized zircon Hf isotope mapping of arc magmatism (previously-published data) from different tectonic units in the Eastern Tianshan and the northern Tarim, revealing that (a) an early Paleozoic (>= ca. 450 Ma) southward subduction of the Junggar oceanic plate (subduction zone advance) resulted in compression and crustal thickening in the northern Tarim (upper plate), as evidenced by increasingly more enriched zircon Hf isotopic compositions, and (b) a slab rollback/retreat of the Junggar oceanic plate probably since ca. 450-440 Ma (tectonic switching from subduction zone advance to retreat), as manifested by progressive increases in zircon epsilon(Hf)(t) values, induced crustal extension and opening of the South Tianshan back-arc basin in the northern Tarim, separating the Central Tianshan continental arc as a micro-continent sliver. This case study highlights the great potential of regional zircon Hf isotope mapping, besides traditional investigations, in helping reveal the enigmatic tectonic mode of subduction zones in ancient orogens. (C) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
机译：在收敛边缘的推进和撤回俯冲区，大陆地壳生长和损失的主要部位，是构造orgenary orgens的构造演化的基石。然而，由于强有力的证据稀缺，区分化石OROGens中的构造模式（推进，退回或切换）的俯冲区并不总是直截了当的。作为一种替代方法，我们利用了Zircon HF同位素映射来自天山和塔里木北部的不同构造单元，揭示了（a）早期古生代（> = Ca.450 ma）向南Junggar海洋板（俯冲区推进）的俯冲导致塔里木北部（上板）的压缩和地壳增厚，如越来越多的锆石英同位素组合物所证明，（B）Junggar海洋的平板回滚/撤退可能是因为加利福尼亚州。 450-440 MA（从俯冲区前进到退缩的构造切换），如锆石ε（T）值（T）值的渐进增加，诱导塔里木北部的南天山背弧盆地的地壳延伸和打开，分离天山中央大陆作为微陆单块。本案例研究突出了区域锆石HF同位素映射的巨大潜力，除了传统的调查，在帮助揭示古代奥古根的俯冲区的神秘构造模式。 （c）2019年国际巩膜研究协会。 elsevier b.v出版。保留所有权利。

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