Subduction Underplating and Uplift in a Young Accretionary Complex

这项研究包括对奥林匹克岩芯（位于华盛顿西北部奥林匹克山脉的一个新生代增生复群）中暴露的俯冲、基底、韧性增厚和隆起过程进行实地研究。地质和地球物理证据表明，东核岩石是在距离海沟至少50公里的吸积楔下被吸积的。因此，该地区提供了一个独特的机会，可以直接研究一个富含沉积物的增生杂岩中更靠陆和更深的部分的变形过程。该研究将结合构造地质学、变质岩石学和裂变径迹测年技术来确定(1)底板的作用过程，无论是由叠瓦状断裂作用还是由大规模流动作用；(2)利用有限应变测量和变形织构分析加积后韧性应变的数量和性质；(3)以变质峰级标示的最大构造埋藏深度；(4)利用裂变径迹测年测定隆升的时间和速率。潜在的贡献包括：(1)更好地理解增生楔是如何生长的以及高压变质岩是如何返回地表的；(2)楔形体内部流动机制的直接信息，这对楔形体的地质力学建模至关重要；(3)古俯冲杂岩填图解释的新工具和新概念。

The research involves a field-based study of the processes of subduction underplating, ductile thickening and uplift as exposed within the Olympic Core rocks, a Cenozoic accretionary complex in the Olympic Mountains of NW Washington. Geological and geophysical evidence indicates that the eastern Core rocks were accreted beneath the accretionary wedge at a distance of at least 50 km from the trench. Therefore, this area provides a unique opportunity to directly study deformational processes within the more landward and deeply seated part of a sediment-rich accretionary complex. The study will combine techniques of structural geology, metamorphic petrology and fission- track dating to determine (1) the process of underplating, whether by imbricate faulting or by wholesale flowage; (2) the amount and nature of post-accretion ductile strain using finite-strain measurements and deformational textures; (3) the maximum depth of structural burial as indicated by peak metamorphic grade; and (4) the time and rate of uplift using fission-track dating. Potential contributions include: (1) a better understanding of how accretionary wedges grow and how high- pressure metamorphic rocks are returned to the surface; (2) direct information about flow mechanisms within the wedge, which is critical to geomechanical modelling of wedges; and (3) new tools and concepts for mapping and interpretation of older subduction complexes.