Publication Abstract [View Article (PDF)]

Bina, C. R., and B. J. Wood, The eclogite to garnetite transition -- Experimental and thermodynamic constraints, Geophysical Research Letters, 11, 955-958, doi:10.1029/GL011i010p00955, 1984.

Abstract. We have found that the forms of the experimentally determined phase diagrams for pyroxene-garnet transformations require the volume changes for these reactions to be much smaller at 130 kbar (400 km) than at 1 atm. Using these volume data we calculated the width of the eclogite-garnetite transition in natural quartz tholeiite and alkali olivine basalt compositions taking account of mixing in multicomponent pyroxene and garnet phases. We find that the eclogite-garnetite transition does not exhibit any discontinuity in bulk sound velocity in the pressure range 110 to 230 kbar. In addition, this velocity, when plotted as a function of pressure, possesses a curvature which is in the opposite sense to that given by the Preliminary Reference Earth Model (PREM). This phase transition, therefore, does not appear to be a satisfactory model for the 400 km seismic discontinuity.

Copyright © 1984 American Geophysical Union
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