Crustal deformation processes in continental collision zones

大陆碰撞带形成了广阔的山脉和高原。喜马拉雅山脉等山脉的戏剧性上升也影响了全球气候和海洋地球化学，导致了长期的环境变化和动物灭绝。因此，要了解全球变化的这些动因，重要的是要限制主要山区增长时期的时间和机制。造山学研究中最重要的进展之一是认识到，山带是建立在造山运动核心中出土的脆弱的、部分熔融的地壳中层上的。尽管数值模拟强调了这一层对于造山的重要性，但它的构造演化仍然知之甚少。因此，这项研究建议的主要重点是研究在中地壳深处变质的高度变形的岩石，这些岩石现在暴露在山带中心附近。喜马拉雅系统被选为这项研究的天然实验室，因为它提供了来自这一地壳中层的前所未有的岩石暴露，以及对构造板块构造、会聚速度和环境后果的良好控制。主要目的是确定折返的中地壳的变形历史，并评价碰撞后变形过程中与其上覆未变质沉积岩的构造相互作用程度。这项研究还将评估造山带不同部分发生增厚、地壳挤压和折返等过程的速率。尽管喜马拉雅造山带启发了许多碰撞造山模式，但它也是最不完全绘制和理解的造山带之一。这项研究将有助于更好地了解活动造山带内变质岩折返的过程，更具体地说，是在其演化的早期阶段。这项研究将提供关键的建筑控制，以完善山脉带的数值模拟，这反过来又将深入了解其他更古老、更深暴露的带的演化，如加拿大的中元古代格伦维尔或古元古代跨哈德逊造山带。

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.