Abstract Variation in the effective strength of lithosphere allows for active plate tectonics and is permitted by different deformation mechanisms operating crust upper mantle. The dominant are debated, but geodynamic models often employ grain-size-independent or evaluate a single grain size. However, observations from nature rock experiments suggest transition to grain-size-dependent due reduc...

[1] While several mechanisms have been suggested to explain the evolution of the Tibetan Plateau, observational constraints on the deep lithospheric processes have been sparse, and previous seismic studies were mostly along profiles perpendicular to the collision front of the Indian and Eurasian plates. In this study, we show tomographic evidence for the delamination of the mantle lithosphere b...

We investigated calcite veins in two spinel-garnet peridotite xenoliths from the sub-Sierra Nevada mantle. These peridotites represent samples of the lithospheric mantle wedge beneath the Mesozoic California magmatic arc, as indicated by radiogenic isotopic ratios measured on clinopyroxenes separates (Sr/Sr8 Ma= 0.7058-0.7061, Nd/Nd8 Ma= 0.512538-0.512601). Mineral chemistry of the peridotite m...

[1] Lineaments in the gravity field and associated chains of volcanic ridges are widespread on the Pacific plate but are not yet explained by plate tectonics. Recent studies have proposed that they are warps and cracks in the plate caused by uneven thermal contraction of the cooling lithosphere. We show that the large thermoelastic stress produced by top-down cooling is optimally released by li...

Seismic anisotropy in the upper mantle beneath continental interiors is generally complicated, with contributions from both the lithosphere and the asthenosphere. Previous studies of SKS splitting beneath the eastern United States have yielded evidence for complex and laterally variable anisotropy, but until the recent arrival of the USArray Transportable Array (TA) the station coverage has bee...

We use 1-D thermal history models and 3-D numerical experiments to study the impact of dynamic thermal disequilibrium and large temporal variations of normal and shear stresses on the initiation of plate tectonics. Previous models that explored plate tectonics initiation from a steady state, single plate mode of convection concluded that normal stresses govern the initiation of plate tectonics,...

[1] We investigate numerically the evolution of crustal and lithospheric thickness, thermal structure, topography, and strain rate of the Tibetan Plateau through time, using the thin viscous sheet approach. We show that lithospheric mantle must have been removed from beneath Tibet to explain the present surface elevation and lack of regional surface slope. In the absence of this removal, the mo...

Some insights into the origin of cratonic mantle can be gained from “eclogite” (loosely defined here as an assemblage containing garnet and any pyroxene) xenoliths hosted in kimberlites erupted through Archean (~2.5­3.5 Gy) cratons. One subset of Archean eclogite xenoliths, the low MgO Archean xenoliths, is presently believed to represent metamorphosed fragments of ancient altered oceanic crust...