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Movie : Animated gif of acoustic emission location time series.
Phase transformations of metastable olivine might trigger deep-focus earthquakes (400 to 700 kilometers) in cold subducting lithosphere. To explore the feasibility of this mechanism, Schubnel et al. performed laboratory deformation experiments on germanium olivine (Mg2GeO4) under differential stress at high pressure (P = 2 to 5 gigapascals) and within a narrow temperature range (T = 1000 to 1250 kelvin). A. Schubnel, F. Brunet, N. Hilairet, J. Gasc, H.w. Green II, “Deep-Focus Earthquake Analogs Recorded at High Pressure and Temperature in teh Laboratory,” Science, (2013):341 (6152), 1377-1380, DOI: 10.1126/science.1240206
►RESEARCH USING GSECARS 13-IDD AND XSD 3-IDB BEAMLINES RULES OUT POSSIBILITY OF A PURE BRIDGMANITE LOWER MANTLE COMPOSITION.
The high-pressure equations of state for 13% Fe and Fe-free bridgmanite
are incorporated into an ideal lattice mixing model enabling the estimation
of thermophysical properties for a large range of ferrous iron compositions. Using this mixture model, we examine the range of plausible values in
temperature composition space relevant to the deep mantle. Through this analysis, we demonstrate that there is no combination of temperature
and composition capable of matching the Earth’s bulk properties near the base of the mantle, ruling out the possibility of a pure bridgmanite lower mantle composition. Click
A group of researchers, lead by Oliver Tschauner, University of Nevada, Las Vegas, have described and named the mineral which constitues 38% of the Earth. Examining natural Bridgmanite, named after Percy Bridgman, the 1946 Nobel laureate who pioneered work in high pressure research, using x-ray diffraction at GSECARS the group examined the highly shocked Tenham L6 chrondrite.
Northwestern University geophysicist Steve Jacobsen and University of New Mexico seismologist Brandon Schmandt with a team of researchers have found evidence of a long-term H2O trap in the transition zone.
Illustration shows S0-mediated Fe(lll) reduction under alkaline conditions. Figure courtesy of Ted Flynn / Science.