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地震和岩石学综合研究，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是什么驱动熔融存在许多假设，但对于美国西部哪些过程占主导地位，甚至在哪里发生熔融，还没有达成共识。Earthscope/USAray新的地震数据提供了前所未有的上地幔结构视图。瑞利波反演方面的发展使相速度的横向和垂直变化的最佳分辨率达到~ 200 km的深度。然而，对于地幔温度、水和熔体含量的相对重要性，地震速度和衰减的解释仍有争议。解决这些变量的最佳方法是从该地区年轻的幔源岩浆和捕虏体中获得独立的约束。初步数据首次显示，来自美国西部地幔的岩浆和捕虏体的含水量变化很大。通过将这些观测结果与其他岩石学和地震学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/软流圈边界，2）熔融区的形状，3）B R之下大陆岩石圈地幔和下伏软流圈的含水量。 该项目包括三项综合活动：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含水量，3）地幔捕虏体研究，包括热压测量、地震速度和含水量。该项目的成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分享。

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.