Collaborative Proposal: Relation of Exhumation to Lithsopheric Architecture Along a Steep Continental Margin, Idaho-Oregon

该项目的目的是确定地形抬升、侵蚀和折返、先前存在的地质边界和驱动变形的下伏地幔动力学之间的联系。油田区域是爱达荷州西部的Salmon River缝合带，这是爱达荷州大部分地区下垫面的前寒武纪北美和俄勒冈州蓝山年轻(显生界)附着地体之间的边界。爱达荷州的岩基完全形成于这条边界的北美一侧。碰撞后和持续变形对区域不同部分的影响不同，代表了先前存在的地质结构和/或深层驱动力的差异。不同山脉的时间、速率和抬升幅度将与目前的地下几何结构有关--利用地震数据确定--以识别在区域尺度上抬高地形的地球-S地壳和地幔的运动。这项工作需要结合地震数据分析，以提供详细的地下结构和热年代学，以确定岩石从深处隆起和折返的时间和当前地形的发展。工作跨越三个主要研究区，并包括最终项目综合：1)记录爱达荷州岩基亚特兰大瓣的折返路径，以确定它是否被较年轻的岩浆活动抬升；2)评估横穿爱达荷州岩基的横穿查利斯断裂带的潜在差异折返；以及3)记录蓝山的折返，以便将其历史与邻近的北美进行比较。一个特别的焦点是，后哥伦比亚河玄武岩延伸是否重新激活了萨蒙河缝合带。将热年代学和地震结果与最近的地质学、地质年代学和地球化学研究相结合，将可以合成区域构造演化，并可以阐明继承的岩石圈结构和活动构造过程之间的关系。佛罗里达大学和弗吉尼亚理工大学的两名研究生和两名本科生直接得到了这项工作的支持。构造综合将涉及所有三个机构的研究生，其中几个由其他来源资助。

The aim of this project is to determine the link between topographic uplift, erosion and exhumation, pre-existing geologic boundaries, and the underlying mantle dynamics that drive deformation. The field area is the Salmon River suture zone of western Idaho, which is the boundary between Precambrian North America underlying most of Idaho and younger (Phanerozoic) accreted terranes of the Blue Mountains in Oregon. The Idaho batholith formed exclusively on the North American side of this boundary. Post-collision and ongoing deformation affect different parts of the region differently, representing differences in pre-existing geologic structure and/or in deep driving forces. The timing, rates, and amounts of uplift of the various mountain ranges will be related to the current subsurface geometry -- determined using seismic data -- to identify motions in the Earth?s crust and mantle that elevated topography on regional scales. The work entails a combination of seismic data analyses, to provide a detailed sub-surface architecture, and thermochronology, to determing the timing of uplift and exhumation of rocks from depth and the development of the current topography.The work spans three main study areas and includes a final project synthesis: 1) Documentation of the exhumation path of the Atlanta lobe of the Idaho batholith to determine if it was uplifted by younger magmatism; 2) Evaluation of potential differential exhumation along the trans-Challis fault zone that cross-cuts the Idaho batholith; and 3) Documentation of exhumation in the Blue Mountains, in order to compare its history to that of adjacent North America. A particular focus is whether the Salmon River suture zone was reactivated by post-Columbia River Basalt extension. The combination of the thermochronology and seismic results with recent geology, geochronology, and geochemistry studies will allow synthesis of a regional tectonic evolution and can illuminate the relationship between inherited lithospheric structures and active tectonic processes.Two graduate and two undergraduate students at the University of Florida and Virginia Tech are directly supported by this work. Tectonic synthesis will involve graduate students at all three institutions, several of whom are funded by other sources.