Comments on: "A Comparison of Recent Experimental Data on the Gabbro-Garnet Granulite-Eclogite Transition"

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Abstract
We are delighted that Green and Ringwood are in close agreement with our recently published experimental results on the details of the transition of gabbro to garnet granulite to eclogite. Our apparent disagreement is in the extrapolation of the data and interpretation of the results. In our view, the seismic discontinuity in the mantle between velocities of 7.5 km/second and 8.2 km/second may well represent the transition from garnet granulite to eclogite. In addition, we believe that where an intermediate velocity zone with of about 7.5 exists in the mantle, this zone may well be made of garnet granulite and we suggest that its upper limit is that of a rate process boundary. We know of no evidence, either field or laboratory, that confirms their view that "eclogite mineralogy is stable in dry basaltic rocks along normal geothermal gradients throughout the continental crust in stable or shield regions."