A tomographic image of the upper mantle beneath central Tibet from INDEPTH data has revealed a subvertical high-velocity zone from approximately 100- to approximately 400-kilometers depth, located approximately south of the Bangong-Nujiang Suture. We interpret this zone to be downwelling Indian mantle lithosphere. This additional lithosphere would account for the total amount of shortening in t...

First arrivals of seismic waves were recorded along the Kamchatka arc using broadband seismic stations deployed for one year in 1998–1999. Cross correlation methods were used from a high resolution data set for tomographic inversion of body waves. The P-wave teleseismic tomography shows evidence of slab shoaling along the northern terminus of the Kamchatka subduction zone. Tomographic anomalies...

Summary The lithosphere and asthenosphere are fundamental to plate tectonics many other earth processes. Vertical motions can be measured quickly accurately by the satellite Global Positioning System, GPS, methods. This paper describes a new analytic method for inferring elastic viscous properties of upper mantle from uplift rate history an area that has been subjected past surface load changes...

Komatiites (ultramafic volcanic rocks) are common among Archean terrains, but rare or absent among rocks< 2.8 Ga old, which implies that the Archean upper mantle was fundamentally different from the modem one. The magma( s) parental to a certain group of lunar samples appear to have formed by exceptionally high-degree partial melting, like the magmas parental to komatiites: The Mg-rich suite of...

The Cenozoic Hannuoba basaltic province, 200 km northwest of Beijing, China, is composed of intercalated tholeiitic, transitional and alkalic basalts. Although the alkalic basalts contain abundant upper mantle xenoliths, they range in MgO content from 5.7 to 10.6% MgO. Most of the major and trace element abundance variations in the alkalic basalts can be explained by segregation of a clinopyrox...

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Minerals recovered from the deep mantle provide a rare glimpse into deep Earth processes. We report the first discovery of ferric iron-rich majoritic garnet found as inclusions in a host garnet within an eclogite xenolith originating in the deep mantle. The composition of the host garnet indicates an ultrahigh-pressure metamorphic origin, probably at a depth of ~200 km. More importantly, the fe...

This paper tests two hypotheses for the influence of thick lithosphere (the tectosphere) upon plate motion. The first is that the tectosphere reaches down into high-viscosity regions of the asthenosphere, effectively slowing the motion of continental plates. The second is that he tectosphere reaches down below the slow-moving convective boundary layer into regions of rapid mantle convection and...

The deformation at the core-mantle boundary produced by the 2004 Sumatra earthquake is investigated by means of a semi-analytic theoretical model of global coseismic and postseismic deformation, predicting a millimetric coseismic perturbation over a large portion of the core-mantle boundary. Spectral features of such deformations are analysed and discussed. The time-dependent postseismic evolut...