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.

该项目是对造山带塌陷区地表流体循环的实地和数值模拟相结合的研究。该研究的重点是伸展拆离带，这些拆离带界定了变质核杂岩，位于脆性上地壳和炎热且通常部分熔融的下地壳之间。地表流体穿透地壳向下到达拆离带，并可能在表征拆离带的热传递和变形局部化中发挥主要作用。几个拆离剖面沿着北美科迪勒拉，从不列颠哥伦比亚省到亚利桑那州，采样和分析的显微结构，氧同位素比值，和热年代学。这些结果用作开发和测试上地壳和拆离带渗透率模型的输入。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，到颗粒尺度的流体与韧性变形过程相互作用。本研究评估了拆离带中流体-岩石相互作用的程度以及流体在造山塌陷中的热作用和力学作用。此外，了解地表流体的同位素流体组成有助于评估新生代北美山脉崩塌期间发生的地形和环境变化。谁会想到雨水可以下降10英里进入地球？面包皮怎么样？现在有充分的证据表明，在满足两个条件的地区，情况就是这样：（1）地壳被构造力拉开，导致开放的裂缝和裂缝，使流体流通;（2）该地区具有高地热梯度，因为它是由热岩石和岩浆的快速向上转移从下面加热的。这些条件促进了地表沃茨的对流循环，当散热器冷却液冷却汽车时，水从地壳中带走了热量。s发动机。对流水流今天在美国西南部的大盆地等地区活跃，其中冷流体的补给和热流体（温泉，矿化区）的排放定义了热液系统。该项目探索了北美科迪勒拉新生代（过去5000万年）形成的化石热液系统的最深区域，这些系统已被构造和侵蚀带到地表。对这些地区进行实地和模拟研究有助于了解流体循环如何影响地壳的热收支和变形。此外，在新生代的不同时间，在地球表面起源的水的成分检索提供了信息的安第斯山脉，从一个雄伟的安第斯高原的地形演变的解剖山脉。