How and why is deformation localised in continental crust?

变形如何以及为何局限于大陆地壳？

• 批准号: 2500058
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2500058
• 关键词: How; why; deformation; localised; continental

In this project the student will make and use geological field investigations of the exhumed lower crust to constrain models of strain localisation, and compare these against modern geodetic data from the India-Asia collision. Over the last few years, geodetic observations of strain from the continents have revealed two modes of behaviour. At fault zones such as the Himalayan Frontal Thrust, Altyn Tagh and Xianshuihe Faults in the India-Eurasia collision zone high geodetic strain rates are observed at the faults themselves. In other regions, including Western Tibet and Mongolia, present-day deformation is diffuse, with little evidence for localisation on the major structures (e.g. Zheng et al., 2017). The underlying reasons for this bi-modal behaviour remain unclear and are highly debated. Understanding processes responsible for the presence or absence of strain localisation in the continents is important for diverse problems ranging from seismic hazard to the distribution of resources.To address the question of strain localisation, the student will make new observations from exhumed lower-crustal rocks in Greenland, where bi-modal behaviour also appears to be present, and use the geological and geodetic observations to assess proposed mechanisms for strain (de-)localisation in continental crust by running numerical models.The Nagssugtoqidian Orogen in SW Greenland is characterised by geological "blocks" that differ in whether strain localization is present or absent. These exhibit striking similarities to areas of different behaviour seen in the present day India-Eurasia collision zone. Compilation of structural and metamorphic data from over 20 years of mapping in the area allow identification of areas of interest that represent the areas of strain localization, largely undeformed regions and areas of diffuse strain. Using this unique dataset, freely available to us, as a guide, the student will conduct additional targeted field work to investigate the rheological, chemical and pre-deformation properties of the rocks outcropping today. They will use the results to build models that test whether the metamorphic, deformation and igneous history of areas involved in present day collisions is a deciding factor in the rheological behaviour of the whole orogen.The latest geodetic strain rate models for the India-Eurasia collision zone are built from more than 2500 individual GPS velocities (Zheng et al., 2017). Work by COMET scientists at Leeds (http://comet.nerc.ac.uk) is using InSAR observations to increase the spatial density of observations (e.g. Wang and Wright, 2012; Wang et al., 2019), but even from the GPS data it is clear that different regimes operate within the India-Eurasia collision zone. The student would refine and improve geodetic models for the India-Eurasia collision zone using the latest observations. We would expect the student to interrogate the data to critically assess the degree of strain localisation that can be observed and how it varies in space (laterally and vertically), potentially also utilizing data derived from ambient noise topography (e.g. Jiang et al. 2014)For the geological part of the project, the student will interrogate the available data from geological mapping campaigns over the last 20 years available from the Geological Survey of Denmark and Greenland to identify field areas of interest. These areas will then be investigated in detail using latest techniques to infer rheological behaviour of different rock units, field analysis and microstructural work (e.g. Svahnberg & Piazolo, 2010) to derive physico-chemical properties.

在这个项目中，学生将对被挖掘的较低地壳进行地质现场调查，以限制应变定位模型，并将这些模型与印度亚洲碰撞的现代大地测量数据进行比较。在过去的几年中，对大陆的应变观察结果揭示了两种行为方式。在印度 - 欧亚碰撞区域中的高大地测量应变率中的喜马拉雅额叶等断层区域，例如，阿尔蒂·塔格（Altyn Tagh）和武道断层。在包括西藏西部和蒙古在内的其他地区，当今的变形是分散的，几乎没有证据表明主要结构的定位（例如，Zheng等，2017）。这种双模式行为的根本原因尚不清楚，并且是有争议的。了解负责在非洲大陆存在应变定位的过程对于从地震危害到资源分布的各种问题至关重SW Greenland中的nagssugsugtoqidian造1基因的数值模型的特征是地质“块”，在菌株定位是否存在或不存在。这些表现出与当今印度 - 欧亚碰撞区域不同行为区域的惊人相似之处。从该区域进行20多年映射的结构和变质数据的汇编允许识别感兴趣的区域，这些区域代表了应变定位的区域，在很大程度上未呈现的区域和弥漫性菌株的区域。使用这个独特的数据集，作为指导，我们可以自由使用，该学生将进行其他有针对性的现场工作，以调查当今岩石算起的流变，化学和预染色的特性。他们将使用结果来构建模型，以测试当今碰撞中涉及的地区的变质，变形和火成岩历史是否是整个造成造成的流变行为的决定性因素。印度 - 欧洲碰撞区的最新测量型应变率模型是由2500个以上的单个GPS速度（Zheng等人）建立的（Zheng et al。，2017年）。彗星科学家在利兹（http://comet.nerc.ac.uk）的工作正在使用内部观测来提高观察的空间密度（例如Wang和Wright，2012; Wang等，2019），但即使从GPS数据中，也很明显，不同的政权在印度 - Euurasia cillisia cillision cillision colisision cormision colisision incem in of India-Euurasia cillision collision Zone。该学生将使用最新的观察结果来完善并改善印度 - 欧洲碰撞区域的大地测量模型。我们希望学生询问数据，以批判性地评估可以观察到的应变定位程度，以及它在空间方面的变化（横向和垂直），也可能利用从周围环境噪声形态得出的数据（例如，Jiang etal。2014）（例如，该项目的地质学部分，学生都可以从GENOLIGATION中审查Den Maggogigation vere of Den Mapping Spects vere of Den Mapping Specips of Endogical of Den of den Mapping of den of the Engrappen的范围的数据，从而确定了den of的范围。 兴趣。然后，将使用最新技术来详细研究这些领域，以推断不同岩石单元，现场分析和微观结构工作的流变性行为（例如Svahnberg＆Piazolo，2010），以得出物理化学性质。