Mantle deformation or processing artefact?

Article Abstract:

Researchers at GeoForschungsZentrum Potsdam (Germany) say that studies claiming to show seismic anisotropy in the mid-mantle between the Tonga-Kermadec subduction zone are likely in error, resulting from unsuitable experimental methodology. There is otherwise a lack of evidence for anisotropy in the mid-mantle, and the observed results could be explained in terms of anisotropy in the upper mantle. The original study authors (from the University of Leeds and the Universite Montpellier)respond that a reanalysis of their data still supports their conclusions, and that the critics have made some mistaken assumptions.

Germany, Tonga, Seismology

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Crustal rheology of the Himalaya and Southern Tibet inferred from magnetotelluric data

Article Abstract:

The Cenozoic collision between the Indian and Asian continents formed the Tibetan plateau and the 1400 km of convergence is accommodated by a combination of underthrusting of Indian and Asian lithosphere, crustal shortening, horizontal extrusion and lithospheric delamination. The inferred low viscosity of this layer is consistent with the development of climatically forced crustal flow in Southern Tibet.

China, India, Tibet, Himalaya Mountains, Lithosphere

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(sup)146Sm-(sup)142Nd evidence from Isua metamorphosed sediments for early differentiation of the earth's mantle.

Article Abstract:

The mean age of mantle differentiation is estimated to be 4,460 plus or minus 115 Myr as detemined by (sup)146Sm-(sup)142Nd chronometry applied to early Archaean rocks and ultraprecisely measuring Nd isotope ratios. Data suggest that the early Sm/Nd fractionation indicate that Earth's mantle differentiation may have occurred during the final stage of terrestrial accretion.

Earth Sciences, Methods, Analysis, Rocks, Sedimentary, Sedimentary rocks, Isotope geology

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