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

该项目是对造山塌陷区表面流体循环的基于现场和数值模拟的综合研究。该研究的重点是伸展脱离区，这些脱离区定义了变质核复合体，位于脆性的上地壳和炽热且通常部分熔融的下地壳之间。表面流体渗透地壳直至脱离区，并可能在表征脱离的传热和变形局部化中发挥重要作用。对北美科迪勒拉山脉（从不列颠哥伦比亚省到亚利桑那州）的几个分离部分进行了采样并分析了微观结构、氧同位素比和热年代学。这些结果被用作开发和测试上地壳和滑脱带渗透率模型的输入。模型解决了从地壳尺度（流体循环是传热剂）到颗粒尺度（流体与延性变形过程相互作用）的流体流动问题。这项研究评估了滑脱带中流体-岩石相互作用的程度以及流体在造山塌陷中的热力和机械作用。此外，了解地表流体的同位素流体成分有助于对新生代北美科迪勒拉山脉塌陷期间发生的地形和环境变化进行评估。谁会想到雨水可以深入地壳10英里？现在有充分的证据表明，在满足两个条件的地区，情况就是如此：（1）地壳被构造力拉开，导致开放的裂缝和裂缝，从而疏导流体； (2)该地区地温梯度较高，因为热岩石和岩浆从下方快速向上转移而受热。这些条件促进了地表水的对流循环，当散热器冷却液冷却汽车发动机时，地表水会带走地壳的热量。今天，在美国西南部的大盆地等地区，对流水流很活跃，其中冷流体的补给和热流体的排出（温泉、矿化区域）定义了热液系统。该项目探索了北美科迪勒拉山脉新生代时期（过去 5000 万年）形成的化石热液系统的最深处区域，并通过构造和侵蚀带到了地表。对这些区域进行现场和建模相结合的研究有助于了解流体循环如何影响热收支和地壳变形。此外，检索新生代不同时期起源于地球表面的水的成分，可以提供有关科迪勒拉山脉地形演化的信息，该山脉从雄伟的类似安第斯山脉的高原演化为被分割的山脉。

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.