Crustal deformation processes in continental collision zones

大陆碰撞带形成广阔的山脉和高原。喜马拉雅山等山脉的急剧上升也影响全球气候和海洋地球化学，导致长期的环境变化和动物群灭绝。因此，为了了解这些全球变化的因素，必须限制主要山区增长事件的时间和机制。造山带研究中最重要的进展之一是认识到，山区是建立在一个薄弱的，部分熔融的中地壳层，是在造山带的核心挖出。虽然数值模拟强调了这一层对造山运动的重要性，但其构造演化仍然知之甚少。 这项研究建议的主要重点是研究在中地壳深度变质的高度变形岩石，这些岩石现在暴露在山区中心附近。喜马拉雅系统被选为这项研究的天然实验室，因为它提供了前所未有的中地壳层岩石暴露，以及提供了对构造板块配置，收敛速度和环境后果的良好控制。主要目的是确定中地壳的变形历史，并评估碰撞后变形过程中与其上覆未变质沉积岩的结构相互作用水平。这项研究还将评估造山带各段的增厚、地壳挤压和折返等过程的速度。 虽然喜马拉雅造山带激发了许多碰撞造山模型，但它也是最不完整的地图和理解之一。这项研究将导致更好地了解过程中涉及的折返活动造山带内的变质岩，更具体地说，在其早期阶段的演变。这项研究将提供关键的建筑控制，以完善山区的数值模拟，这反过来又会产生洞察到其他，更老，更深的暴露带，如中元古代格伦维尔或古元古代trans-Hudson造山带在加拿大的演变。

Continental collision zones form extensive mountain ranges and high plateaus. The dramatic rise of mountain belts such as the Himalaya also influences global climate and ocean geochemistry, leading to long-term environmental changes and faunal extinctions. To understand these agents of global change, it is therefore important to constrain the timing and mechanisms of major mountain growth episodes. One of the most significant advances in orogenic studies has been the realization that mountain belts are built on a weak, partially molten mid-crustal layer that is exhumed in orogenic cores. Although numerical modelling highlights the importance of this layer for mountain building, its tectonic evolution remains poorly understood.   The principal focus of this research proposal is the study of highly-deformed rocks metamorphosed at mid-crustal depths, which are now exposed near the centre of mountain belts. The Himalayan system is chosen as a natural laboratory for this study because it offers unprecedented exposure of rocks from this mid-crustal layer, as well as providing excellent controls on tectonic plate configuration, convergence rates, and environmental consequences. The main objectives are to determine the deformation history of the exhumed middle crust, and to evaluate the level of structural interactions with its overlying unmetamorphosed sedimentary rocks during post-collision deformation. The research will also evaluate the rates at which processes such as thickening, crustal extrusion, and exhumation take place in various segments of the orogen.   Although the Himalaya is the orogen that inspires many models of collisional orogenesis, it is also one of the most incompletely mapped and understood. This research will lead to a better understanding of processes involved in exhumation of metamorphic rocks within active orogenic belts, more specifically in their early stages of evolution. This research will provide key architectural control to refine numerical modelling of mountain belts, which in turn will yield insight into the evolution of other, older, more deeply exposed belts such as the Mesoproterozoic Grenville or the Paleoproterozoic Trans-Hudson orogens in Canada.