A test of laboratory based rheological parameters of olivine from an analysis of late Cenozoic convective removal of mantle lithosphere beneath the Sierra Nevada, California, USA

We use the apparent change in mantle structure beneath the Sierra Nevada since ca. 10 Ma, which suggests convective removal of eclogite-rich mantle lithosphere, and scaling laws developed for Rayleigh-Taylor instability to place constraints on the average viscosity coefficient of the mantle lithosphere. By treating the lithosphere as a non-Newtonian fluid obeying power-law creep with an exponent of n = 3.5, we may compare the inferred values of viscosity coefficient with those obtained from laboratory experiments on olivine and eclogite. The values that we obtain overlap those predicted by laboratory-based flowlaws for the range of geotherms implied by heat flux measurements within the Sierra Nevada and by metamorphic geothermometry and geobarometry of xenoliths in volcanic rock erupted in the Sierra Nevada at ca. 10 Ma. Thus, this comparison offers support for laboratory-derived flow laws, and specifically for the high stress limit suggested by Evans & Goetze (1979). Conversely, this agreement shows that the high strength of cold mantle minerals does not prohibit its removal by convective instability.