The Role of Fluid Flow in the Cooling of Metamorphic Core Complexes

流体流动在变质岩心复合体冷却历史中的作用明尼苏达大学christian Teyssier mark Person这个项目的目的是利用一个包含地壳变形运动学的热液模型，量化挖掘过程中流体流动对变质岩心复合体热历史的影响。数值模型受到基于广泛的构造、变质和热年代学数据的实地研究的约束，这些数据来自于不列颠哥伦比亚省Shuswap变质核杂岩。该模型允许对Shuswap系统内的传热与岩石热年代学和流体-岩石同位素交换进行定量比较。该模型有助于测试流体流动对断层几何形状、运动学和上地壳（地堑和地堑、多米诺式块体、链状系统）渗透率的敏感性，以及下地壳中韧性流动和伴随的热平流的敏感性。模拟还评价了流体流动对拆离带下方热分布和地温梯度的影响，这对理解岩心杂岩的变质分带具有重要意义。定量结果与我们在不列颠哥伦比亚省Shuswap变质核杂岩中建立的大规模热年代学数据库进行了比较；这种类型的一般建模可以直接导出到其他变质岩心杂岩和裂谷带。研究还揭示了舒斯瓦普变质核杂岩拆离带的流体-岩石相互作用系统和热历史。为此，我们基于裂变径迹和(U-Th)/He方法，对哥伦比亚河分离和断裂系统的两个断面进行了详细的热年代学研究，这些断层系统将变质核杂岩边界向东延伸。在同一地区，我们通过分析矿脉、断层岩石和未破裂岩石中的稳定同位素特征和流体包裹体来研究流体-岩石相互作用。这部分研究限制了流体的性质、流体路径的范围、表面流体穿透变质地壳的程度、流体的古温度，以及可能的流体通量。我们正在构建一套数值实验来表示同位素流体-岩石相互作用以及在这个较小尺度框架内的热年代学数据，以便更好地了解滑脱/正断层系统中的流体流动。详细的野外工作和地球化学结果也作为检验模型结果的基础事实。流体流动作为一种主要的热传递机制的定量分析将有助于改进地质学家使用冷却速率来确定挖掘速率的方法。

The role of fluid flow in the cooling history of metamorphic core complexesChristian Teyssier, University of MinnesotaMark Person, Indiana UniversityThe aim of this project is to quantify the effects of fluid flow on the thermal history of metamorphic core complexes during exhumation using a hydrothermal model that incorporates the kinematics of crustal deformation. The numerical model is constrained by field studies based on extensive structural, metamorphic, and thermochronologic data for the Shuswap metamorphic core complex, British Columbia. The modeling allows for quantitative comparison of heat transfer with rock thermochronology and fluid-rock isotopic exchange within the Shuswap system. The modeling helps to test the sensitivity of fluid flow to fault geometry, kinematics, and permeability in the upper crust (horst and graben, domino-style blocks, listric systems), as well as ductile flow and attending heat advection in the lower crust. The modeling also evaluates the effect that fluid flow has on heat distribution and geothermal gradients below the detachment zone, which has implications for the understanding of metamorphic zoning in core complexes. Quantitative results are being compared to the large-scale thermochronology database we developed in the Shuswap metamorphic core complex, British Columbia; this type of generic modeling is directly exportable to other metamorphic core complexes as well as rift zones.The research also sheds light on the systematics of fluid-rock interactions and thermal history in the detachment zones of the Shuswap metamorphic core complex. Towards this end, we are conducting a detailed thermochronologic study based on the fission-track and (U-Th)/He methods on two transects across the Columbia River detachment and fault system that bounds the metamorphic core complex to the east. In the same regions, we are examining fluid-rock interaction by analyzing the stable isotope signature and fluid inclusions within veins, fault rocks, and unfractured rock. This part of the study constrains the nature of the fluids, the extent of fluid pathways, the degree to which surficial fluids penetrate the metamorphic crust, the fluids paleo-temperatures, and possibly also fluid fluxes. We are constructing a suite of numerical experiments to represent isotopic fluid-rock interactions as well as thermochronologic data within this smaller-scale framework in order to better understand fluid flow in detachment/normal fault systems. The detailed field work and geochemical results also serve as ground truth against which the modeling results are tested. The quantitative analysis of fluid flow as a major heat transfer mechanism will help to refine the method in which geologists use cooling rates to determine exhumation rates.