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Orogen-parallel deformation of the Himalayan midcrust: Insights from structural and magnetic fabric analyses of the Greater Himalayan Sequence, Annapurna-Dhaulagiri Himalaya, central Nepal

机译:喜马拉雅中地壳的造山带平行变形:来自尼泊尔中部Annapurna-Dhaulagiri喜马拉雅山大喜马拉雅层序的结构和磁性织物分析的见解

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摘要

The metamorphic core of the Himalaya (Greater Himalayan Sequence, GHS), in the Annapurna-Dhaulagiri region, central Nepal, recorded orogen-parallel stretching during midcrustal evolution. Anisotropy of magnetic susceptibility and field-based structural analyses suggest that midcrustal deformation of the amphibolite facies core of the GHS occurred under an oblate/suboblate strain regime with associated formation of low-angle northward dipping foliation. Magnetic and mineral stretching lineations lying within this foliation from the top of the GHS record right-lateral orogen-parallel stretching. We propose that oblate strain within a midcrustal flow accommodated oblique convergence between India and the arcuate orogenic front without the need for strain partitioning in the upper crust. Oblate flattening may have also promoted orogen-parallel melt migration and development of melt-depleted regions between km(3) scale leucogranite culminations at similar to 50-100km intervals along orogen strike. Following the cessation of flow, continued oblique convergence led to upper crustal strain partitioning between orogen-perpendicular convergence on thrust faults and orogen-parallel extension on normal and strike-slip faults. In the Annapurna-Dhaulagiri Himalaya, orogen-parallel stretching lineations are interpreted as a record of transition from midcrustal orogen-perpendicular extrusion to upper crustal orogen-parallel stretching. Our findings suggest that midcrustal flow and upper crustal extension could not be maintained simultaneously and support other studies from across the Himalaya, which propose an orogen-wide transition from midcrustal orogen-perpendicular extrusion to upper crustal orogen-parallel extension during the mid-Miocene. The 3-D nature of oblate strain and orogen-parallel stretching cannot be replicated by 2-D numerical simulations of the Himalayan orogen.
机译:尼泊尔中部安纳布尔纳峰-道拉吉里峰地区喜马拉雅山的变质核(大喜马拉雅层序,GHS)记录了中地壳演化过程中造山带平行伸展。磁化率的各向异性和基于场的结构分析表明,GHS的两闪石相岩心的中地壳形变发生在扁形/亚扁形应变状态下,并伴有低角度向北浸入叶状体的形成。从GHS顶部到该叶内的磁性和矿物伸展线记录了右侧造山带平行伸展。我们提出,中地壳流动内的扁形应变适应了印度和弧形造山带锋面之间的倾斜会聚,而无需在上地壳中进行应变分配。扁圆形扁化还可能促进了造山带平行熔体迁移和km(3)级白云母高潮之间熔体贫化区域的发展,沿着造山带走向的间隔约为50-100km。随着水流的停止,持续的斜向收敛导致上地壳应变在推力断层的造山带垂直收敛与正断层和走滑断层的造山带平行延伸之间分配。在Annapurna-Dhaulagiri喜马拉雅山中,造山带平行伸展线被解释为从中地壳造山带垂直挤压到上地壳造山带平行伸展的过渡记录。我们的研究结果表明,中地壳流动和上地壳伸展不能同时维持,并支持整个喜马拉雅山脉的其他研究,该研究提出在中新世中期从中地壳造山带垂直挤压到上地壳造山带平行伸展的整个造山带过渡。扁形应变和造山带平行伸展的3D性质无法通过喜马拉雅造山带的2D数值模拟来复制。

著录项

  • 来源
    《Tectonics》 |2016年第12期|2515-2537|共23页
  • 作者单位

    Univ Leeds, Sch Earth & Environm, Leeds, W Yorkshire, England|Geol Survey Canada, NRCan, Vancouver, BC, Canada;

    Southern Illinois Univ, Dept Geol, Carbondale, IL USA;

    Virginia Polytech Inst & State Univ, Dept Geosci, Blacksburg, VA 24061 USA;

    Univ Leeds, Sch Earth & Environm, Leeds, W Yorkshire, England;

    Univ Leeds, Sch Earth & Environm, Leeds, W Yorkshire, England;

    Univ Oxford, Dept Earth Sci, Oxford, England;

  • 收录信息
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Himalaya; Tibet; orogen-parallel deformation; AMS; rock magnetism; channel flow;

    机译:喜马拉雅山;西藏;造山带平行变形;AMS;岩石磁性;通道流;
  • 入库时间 2022-08-18 03:34:33

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