Thermochronology and Geochemistry of Lower Crustal Xenoliths, Central Mongolia: Formation and Evolution of the Deep Crust in an Intracontinental Setting

蒙古中部下地壳包体的热年代学和地球化学：陆内环境中深部地壳的形成和演化

• 批准号: 1426857
• 负责人: Peter Zeitler
• 金额: $ 8.29万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1426857&HistoricalAwards=false
• 关键词: Thermochronology; Geochemistry; Lower; Crustal; Xenoliths

One thing we do not yet understand about Earth is why and how high elevations can form far from the boundaries of the tectonic plates. Within one such region of anomalous topography, young lavas from Tariat. Mongolia carry in them rare samples of the lower crust in the form of what are called ?xenoliths?. These xenoliths can help answer questions about how changes in the lower crust might in turn control surface topography. The formation and destruction of high topography can serve as a control on the evolution of ecosystems and biodiversity, and can alter climate patterns. In particular, understanding when high topography formed in Mongolia has significant ramifications for understanding northern-hemisphere paleoclimate evolution because high-elevation regions in central Mongolia are currently important for the nucleation of northern-Pacific storms.To understand the timing, formation and thermal evolution of the lower continental crust in central Mongolia this multidisciplinary project of Tariat, lower-crustal xenoliths will use thermobarometry, geochronology, thermochronology, and major-element, trace-element, and isotope geochemistry. Thermobarometry will be used to constrain the equilibration temperatures pressures of the xenoliths. Abundant zircon observed in the samples will be dated by U-Pb laser ablation ICP-MS and ID-TIMS to determine the timing of lower-crustal formation and any metamorphism. To the extent that the Hangay region is supported by a crustal root, constraining the age of the root will help place constraints on the timing of rock uplift and, by inference and by modeling, surface uplift. Whole-rock major- and trace-element geochemistry as well as Sr, Nd, Hf, and Pb isotope analyses will help constrain what processes formed the lower-crust. The post-orogenic, long term thermal evolution of the lower crust will be assessed using U-Pb analyses of a number of trace phases likely to be present in these samples, including monazite and apatite. Together with ongoing studies of Mongolian geodynamics, this work, which is part of a Ph.D. dissertation, will determine the timing and evolution of the high topography in central Mongolia, and more broadly, advance our knowledge about geodynamic processes that can produce high topography in continental interiors.

我们尚不了解地球的一件事是，为什么以及高程与构造板的边界形成远。在一个异常地形的一个区域内，来自Tariat的年轻熔岩。蒙古以所谓的“ xenoliths？这些异种石可以帮助回答有关下层外壳变化的问题反过来又可能控制表面地形。高地形的形成和破坏可以控制生态系统和生物多样性的演变，并可以改变气候模式。特别是，理解在蒙古形成的高地形时，在理解北部山脉的古气候进化方面具有重大影响，因为目前，蒙古中部的高海拔区域对于北太平洋风暴的成核很重要，以了解蒙古人中部蒙古人的低大陆分类的时机，地层和热进化，以下是蒙古人的较低大陆。热体计量学，地质学，热团学和主要元素，痕量元素和同位素地球化学。热压法将用于限制异种石的平衡温度压力。在样品中观察到的丰富锆石将通过U-PB激光消融ICP-MS和ID-TIMS来确定低壳形成和任何变质的时间。在一定程度上，hangay区域由地壳根部支撑，限制根的年龄将有助于将约束放在岩石隆起的时机上，并通过推理和建模，表面隆起。全摇滚主要和痕量元素地球化学以及SR，ND，HF和PB同位素分析将有助于限制哪些过程形成较低的壳。将使用对这些样品中可能存在的许多痕量相的U-PB分析来评估下地壳的长期长期热演化，包括独居石和磷灰石。这项工作是对蒙古地球动力学的持续研究，这是博士学位的一部分。论文将确定蒙古中部高地形的时间和演变，更广泛地促进我们对地球动力学过程的了解，这些过程可以在大陆室内室内产生高地形。