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的综合地震和岩石学研究，探索地幔动力学和岩浆活动之间的联系。对于岩石圈伸展、水合作用、加热和对流去除过程中导致融化的原因，存在许多假设，但对于这些过程中哪一种在美国西部占主导地位，甚至在哪里发生融化，目前还没有达成共识。来自Earthscope/USArray的新地震数据提供了前所未有的上地幔结构视图。瑞利波反演技术的发展，使我们能够最好地分辨出200公里深处相速度的横向和垂直变化。然而，对于地震速度和衰减的解释，对于地幔温度、水和熔体含量的相对重要性仍然存在争议。解决这些变量的最佳方法是获得该地区年轻幔源岩浆和捕虏体的独立约束条件。初步数据首次显示了来自美国西部地幔的岩浆和捕虏体含水量的巨大变化。通过将这些观测结果与其他岩石学和地震对地幔温度和熔融深度的预测相结合，我们的目标是确定1)岩石圈/软流圈的边界，2)熔融区域的形状，以及3)大陆岩石圈地幔和B&amp；R下面的软流圈的含水量。该项目包括三个综合活动：1)表面波速度、衰减和各向异性的反演；2)熔融包裹体研究中岩浆含水量的测量；3)地幔捕虏体的研究，包括热气压测量、地震速度和含水量。该项目的结果将通过网络界面与EarthScope和GeoSwath社区、NavDat数据库以及感兴趣的公众共享。

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.