[1] Teleseismic traveltime data are inverted for mantle Vp and Vs variations beneath a 1400 km long line of broadband seismometers extending from eastern New Mexico to western Utah. The model spans 600 km beneath the moho with resolution of 50 km. Inversions show a sharp, largemagnitude velocity contrast across the Colorado PlateauGreat Basin transition extending 200 km below the crust. Also im...

[1] Rayleigh wave phase and amplitude data are analyzed to provide new insight into the velocity structure of the upper mantle beneath the Slave craton, in the northwestern Canadian Shield. We invert for phase velocities at periods between 20 s–142 s (with greatest sensitivity at depths of 28–200 km) using crossing ray paths from events recorded by the POLARIS broadband seismic network and the ...

Ultramafic xenoliths from southeastern Arizona, USA, provide evidence for Cu-isotope heterogeneity in the lithospheric mantle. We report new data on Type I (Cr-, Mg-rich) peridotites, but also first Fe-Ti-Al-rich II pyroxenite (±amphibole) xenoliths. Whole rock ?65Cu values of pyroxenites and cryptically metasomatized lherzolites range to isotopically heavier compositions than asthenospheric ma...

The subsidence of the sea floor is generally considered a consequence of its passive cooling and densifying since its formation at the ridge and is therefore regarded as a function of lithospheric age only. However, the lithosphere is defined as the thermal boundary layer of mantle convection, which should thus determine its structure. We examined the evolution of the lithosphere structure and ...

[1] Three-dimensional models of the uplift of Beta Regio caused by a mantle plume satisfy constraints on gravity, topography, rheology, and the uplift rate substantially better than two-dimensional models. In particular, the uplift time of Beta Regio is reduced to an acceptable 800 million years. Three-dimensional models give the plume formation depth around 3000 km, which approximately corresp...

Earth is the only terrestrial planet in our solar system where an oceanic plate subducts beneath an overriding plate. Although the initiation of plate subduction requires extremely weak boundaries between strong plates, the way in which oceanic mantle rheologically weakens remains unknown. Here we show that shear-enhanced hydration reactions contribute to the generation and maintenance of weak ...

Abstract Geoid anomalies offer crucial information on the internal density structure of Earth, and thus, its constitution dynamic state. In order to interpret geoid undulations in terms depth, magnitude lateral extension lithosphere upper mantle, effects lower mantle need be removed from full (thus obtaining residual ’upper geoid’). However, how achieve this seemingly simple filtering exercise ...

We examine two prominent upper mantle velocity anomalies in the southwest Pacific, the Tonga slab anomaly and the corresponding ov. erlying mantle wedge anomaly, using data collected during a combined land-sea deployment of temporary seismometers. The linear geometry and small interstation spacing of the instruments yield high-resolution data along a cross section of the Tonga subduction zone, ...