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

流体流动在变质核杂岩冷却史中的作用明尼苏达大学的Christian Teyssier和印第安纳州大学的Mark Person本项目的目的是利用一个包含地壳变形运动学的热液模型来量化流体流动对变质核杂岩折返过程中热历史的影响。 该数值模型的约束，广泛的结构，变质和热年代学数据的基础上的Shuswap变质核杂岩，不列颠哥伦比亚省的实地研究。 该模型可以定量比较热传递与岩石热年代学和流体岩石同位素交换Shuswap系统内。 该模型有助于测试流体流动的灵敏度断层几何形状，运动学，渗透性在上地壳（地垒和地堑，多米诺骨牌式块，铲式系统），以及韧性流动和参加热平流在下地壳。 该模型还评估了流体流动对拆离带下方的热分布和地热梯度的影响，这对理解核杂岩中的变质分区具有一定的意义。 定量研究结果与我们在不列颠哥伦比亚省Shuswap变质核杂岩中开发的大型热年代学数据库进行了比较;这种类型的通用建模可直接导出到其他变质核杂岩以及裂谷带。为此，我们正在进行详细的热年代学研究的裂变径迹和（U-Th）/He方法的基础上的两个横截面横跨哥伦比亚河拆离和断层系统，界定变质核杂岩的东部。 在同一地区，我们通过分析脉、断层岩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。 这部分的研究限制了流体的性质，流体通道的范围，地表流体渗透变质地壳的程度，流体古温度，也可能是流体通量。 我们正在构建一套数值实验，以代表同位素流体-岩石相互作用，以及在这个较小规模的框架内的热年代学数据，以更好地了解流体流动在剥离/正断层系统。 详细的现场工作和地球化学结果也作为地面实况，对模拟结果进行了测试。对流体流动作为主要热传递机制的定量分析将有助于改进地质学家利用冷却速率确定折返速率的方法。

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.