Field and Numerical Analyses of the Thermal, Mechanical, and Fluid Evolution of Extensional Detachment Zones

伸展脱离带的热、机械和流体演化的现场和数值分析

• 批准号: 0838541
• 负责人: Christian Teyssier
• 金额: $ 35万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-01 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838541&HistoricalAwards=false
• 关键词: Field; Numerical; Analyses; Thermal; Mechanical

This project is a combined field-based and numerical modeling study of the circulation of surface fluids in zones of orogenic collapse. The study focuses on extensional detachment zones that define metamorphic core complexes and are located between the brittle upper crust and the hot and commonly partially molten lower crust. Surface fluids penetrate the crust down to the detachment zones and likely play a major role in the heat transfer and deformation localization that characterize detachments. Several detachment sections along the North American Cordillera, from British Columbia to Arizona, are sampled and analyzed for microstructures, oxygen isotopic ratios, and thermochronology. These results are used as input to develop and test permeability models of the upper crust and detachment zones. Models address fluid flow from the crustal scale, where fluid circulation is a heat-transfer agent, to the grain scale where fluids interact with ductile deformation processes. This study evaluates the degree of fluid-rock interaction in detachment zones and the thermal and mechanical role of fluids in orogenic collapse. In addition, knowing the isotopic fluid composition of surface fluids promotes an evaluation of the topographic and environmental changes that took place during the collapse of the North American Cordillera in Cenozoic time.Who would think that rain water can descend 10 miles into the Earth?s crust? There is now ample evidence this is the case in regions that meet two conditions: (1) the crust is being pulled apart by the forces of tectonics, resulting in open cracks and fractures that canalize fluids; and (2) the region has a high geothermal gradient because it is heated from below by the rapid upward transfer of hot rocks and magma. These conditions promote the convective circulation of surface waters that remove heat from the crust as a radiator coolant fluid cools a car?s engine. Convective water flow is active today in regions such as the Great Basin in the southwestern United States where recharge of cool fluids and discharge of hot fluids (hot springs, mineralized areas) define hydrothermal systems. This project explores the deepest regions of fossil hydrothermal systems that formed during Cenozoic time (last 50 million years) in the North American Cordillera and that have been brought to the surface by tectonics and erosion. A combined field and modeling study of these regions helps understand how fluid circulations influence the thermal budget and the deformation of the crust. In addition, retrieving the composition of water that originated at the Earth surface at different times during the Cenozoic gives information on the topographic evolution of the Cordillera that evolved from a majestic Andean-like plateau to a dissected mountain range.

该项目是造影膜塌陷区域中表面流体循环的基于田间和数值的联合建模研究。该研究的重点是定义变质核心复合物的延伸脱离区，位于脆性上皮和通常部分熔融下层外壳之间。表面流体将外壳渗透到脱离区域，并可能在表征脱离的传热和变形定位中起主要作用。从不列颠哥伦比亚省到亚利桑那州的北美山脉沿线的几个支队进行了采样，并分析了微观结构，氧同位素比和热团学。这些结果用作开发和测试上地壳和脱离区域的渗透率模型的输入。模型解决了从地壳尺度的流体流动，其中流体循环是一种传热剂，到晶粒尺度，流体与延性变形过程相互作用。这项研究评估了脱离区域中流体 - 岩石相互作用的程度以及流体在造山学崩溃中的热和机械作用。此外，了解表面流体的同位素流体组成可以促进对北美山内兰山脉崩溃期间的地形和环境变化的评估。现在有充分的证据在符合两个条件的地区是这种情况：（1）构造力的力量将外壳拆开，导致开放的裂缝和裂缝，使液体流动； （2）该地区具有高地热梯度，因为它通过热岩石和岩浆的快速向上转移从下方加热。这些条件促进了地表水的对流循环，这些散热器冷却液液会冷却汽车发动机，从而从外壳中除去了热量。当今，对流水流活跃在美国西南部的大盆地等地区，在那里充电凉爽的液体和排放热流体（温泉，矿物化区域）定义了水热系统。该项目探讨了北美山脉在北美山内科（Corsillera）在新生代时代（最近5000万年）形成的化石热液系统的最深区域，并被构造和侵蚀带到了表面。这些区域的联合田地和建模研究有助于了解流体循环如何影响热预算和外壳的变形。此外，在新生代期间，在不同时间检索起源于地球表面的水的成分提供了有关山羊皮列拉（Cordillera）的地形演变的信息，这些进化从雄伟的安第斯（Andean）像安第斯（Andean）的高原发展为解剖的山脉。