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

本项目是对造山带地表流体循环的实地模拟与数值模拟相结合的研究。研究的重点是确定变质核杂岩的伸展拆离带，这些拆离带位于脆脆的上地壳和热的、通常部分熔融的下地壳之间。表面流体穿透地壳到达分离带，可能在分离特征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，沿着北美科迪勒拉的几个分离剖面进行了采样和分析，以进行微观结构，氧同位素比率和热年代学。这些结果被用于开发和测试上地壳和剥离带的渗透率模型。模型处理从地壳尺度到晶粒尺度的流体流动，其中流体循环是一种传热介质，其中流体与韧性变形过程相互作用。本研究评价了拆离带中流体-岩石相互作用的程度以及流体在造山带崩塌中的热力学作用。此外，了解地表流体的同位素组成有助于评估新生代北美科迪勒拉崩塌期间发生的地形和环境变化。谁会想到雨水能下降10英里进入地球？地壳?现在有充分的证据表明，在满足两个条件的地区就是这种情况：(1)地壳被构造力拉开，形成开放的裂缝和裂缝，使流体流动；(2)由于热岩石和岩浆的快速向上转移，该地区的地热梯度很高。这些条件促进了地表水的对流循环，就像散热器冷却液冷却汽车一样，从地壳中带走热量。年代引擎。今天，在美国西南部的大盆地等地区，对流水流很活跃，在那里，冷流体的补充和热流体的排放（温泉、矿化区）定义了热液系统。该项目探索了北美科迪勒拉地区新生代（过去5000万年）形成的化石热液系统的最深处，这些系统由于构造和侵蚀而被带到地表。对这些区域进行实地和模拟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，检索在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从雄伟的安第斯高原到解剖山脉的地形演变的信息。

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.