Collaborative Research: Mantle Dynamics and Magmatism Across the Basin and Range

该项目通过对美国西部盆地和山脉进行综合的地震和岩石学研究，探索地幔动力学和岩浆作用之间的联系。对于岩石圈伸展、水化、加热和对流移除过程中是什么驱动熔化，存在着许多假说，但对于这些过程中哪一种是主导的，甚至在哪里发生熔化，还没有达成共识。来自Earthcope/US阵列的新的地震数据提供了一个前所未有的上地幔结构的视角。瑞利波反演的进展使相速度横向和垂直变化的最佳分辨率达到了约200公里的深度。然而，关于地幔温度、水和熔体含量的相对重要性，对地震速度和衰减的解释仍然存在争议。解决这些变量的最好方法是从该地区年轻的地幔岩浆和捕虏体中获得独立的约束条件。初步数据首次显示，来自美国西部地幔的岩浆和包体的水含量变化很大。通过将这些观测与地幔温度和熔融深度的其他岩石学和地震预测相结合，我们的目标是确定1)岩石圈/软流圈边界，2)熔融区的形状，以及3)大陆岩石圈地幔和B&amp；R之下的下伏软流圈的水分含量。这个项目涉及三个综合活动：1)面波速度、衰减和各向异性的反演，2)从熔融包裹体研究中测量岩浆的水含量，以及3)地幔包体研究，包括温度气压、地震速度和水含量。该项目的结果将通过网络界面与EarthScope和GeoSwath社区、NavDat数据库和感兴趣的公众共享。

This project is exploring the link between mantle dynamics and magmatism through an integrated seismic and petrologic study across the Basin and Range of the Western US. Many hypotheses exist for what drives melting during lithosphere extension, hydration, heating and convective removal, but there is as yet no consensus on which of these processes is dominant in the western US, nor even where melting occurs. New seismic data emerging from Earthscope/USArray are providing an unprecedented view of upper mantle structure. Developments in the inversion of Rayleigh waves are allowing the best resolution of lateral and vertical variations in phase velocities to depths of ~ 200 km. The interpretation of seismic velocity and attenuation, however, is still debated as to the relative importance of mantle temperature, water and melt content. The best approach to resolving these variables is to obtain independent constraints from young mantle-derived magmas and xenoliths from the region. Preliminary data show for the first time large variations in the water content of magmas and xenoliths derived from the mantle of the western US. By integrating such observations with other petrologic and seismic predictions of mantle temperature and melting depth, our goals are to determine 1) the lithosphere/asthenosphere boundary, 2) the shape of the melting region, and 3) the water content of the continental lithospheric mantle and underlying asthenosphere beneath the B&R. This project involves three integrated activities: 1) inversion of surface waves for velocity, attenuation and anisotropy, 2) measurement of the water content of magmas from melt inclusion studies, and 3) study of mantle xenoliths, including thermobarometry, seismic velocities, and water content. Results from this project will be shared with the EarthScope and GeoSwath communities, the NavDat database, and the interested public with a web interface.