SGER: Interactions Of Hotspots and the Lithosphere: An Integrated Study of the Newberry Hotspot

全球地球科学中一个关键且悬而未决的问题是热点与它们下面地幔中发生的过程的关系。最流行的热点形成模型是地幔热柱模型(静止的深部地幔源区)，因此，以前的许多研究都集中在经典的热柱位置上。PI将解决俄勒冈州纽伯里热点轨迹的原因，该轨迹不可能是静止的地幔来源的产物。纽伯里热点形成的三种端元构造模式是：(1)克拉通或与羽流有关的物质沿大陆岩石圈底部的重力流；(2)与胡安德·富卡板块俯冲有关的逆流；(3)盆地和山脉北部边界的渐进式岩石圈断裂。初步的地震数据表明，沿着纽伯里热点的长度没有地幔物质流动。相反，东西向的横波分裂观测与火山进程倾斜，是地区性观测的。这些观察表明，要么假设(1)和(2)需要修正，要么岩石圈过程(假设3)发挥主导控制作用。PI将利用现有的七个地震台网的数据集来调查该地区的岩石圈和软流圈结构。地幔的层析成像将把远震体波旅行时间与当地面波约束结合起来。初步的地震各向异性研究将扩大到包括更多的台站和正在变得可用的更大的数据集。该提议的最终目标是描述纽伯里热点下的岩石圈和软流圈过程。这些过程可以作为地幔热柱模型的补充假设，以便客观地评估其他热点。对俄勒冈州现有数据集的拟议分析将提供一种机制，通过规划未来的实验来优化地球观测资源，以配合美国阵列移动阵列的存在和多国组织设备抵达该地区。

A crucial and unsolved question in global earth science is the relationship of hotspots toprocesses that occur in the mantle beneath them. The most prevalent model for the formation of hotspots is the mantle plume model (stationary deep-mantle source) and, consequently, many previous studies have focused on classic plume locations. The PI will address the cause of the Newberry hotspot track in Oregon which cannot be the product of a stationary mantle source. The three end-member tectonic models for the formation of the Newberry hotspot are: (1) gravitational flow along the base of the continental lithosphere due to the edge of the craton or plume related material, (2) counterflow associated with subduction of the Juan de Fuca plate, and (3) progressive lithospheric faulting at the northern boundary of the Basin and Range. The preliminary seismic data suggest that there is no flow of mantle material along the length of the Newberry hotspot. Rather, E-W oriented shear wave splitting observations, oblique to the volcanic progression, are observed regionally. These observations suggest that either hypotheses (1) and (2) need modification or that lithospheric processes (hypothesis 3) exert thedominant control. The PI will utilize datasets from seven existing seismic networks to investigate lithospheric and asthenospheric structure in the region. Tomographic imaging of the mantle will integrate teleseismic body-wave traveltimes with local surface-wave constraints. The preliminary seismic anisotropy study will be extended to include more stations and the larger datasets that are becoming available. The ultimate goal of the proposal is to characterize the lithospheric and asthenospheric processes beneath the Newberry hotspot. These processes can then be used as a complementary hypothesis to the mantle plume model, in order to objectively evaluate other hotspots. The proposed analysis of the existing data sets in Oregon will provide a mechanism to optimize Earthscope resources through planning of future experiments to coincide with thepresence of the USArray transportable array and the arrival of PBO equipment in the region.