An experimental study of the grain-scale processes of peridotite melting: implications for major and trace element distribution during equilibrium and disequilibrium melting

摘要: The grain-scale processes of peridotite melting were examined at 1,340°C and 1.5 GPa using reaction couples formed by juxtaposing pre-synthesized clinopyroxenite against orthopyroxenite or harzburgite in graphite platinum-lined molybdenum capsules. Reaction between the clinopyroxene orthopyroxene-rich aggregates produces a melt-enriched, orthopyroxene-free, olivine + clinopyroxene reactive boundary layer. Major trace element abundance vary systematically across layer with compositional trends similar to published core-to-rim variations bulk lherzolite partial studies conducted P–T conditions. growth takes place expense is consistent that involve dissolution, precipitation, reprecipitation, diffusive exchange interstitial melt surrounding crystals. An important consequence dissolution–reprecipitation during crystal-melt interaction dramatic decrease reequilibration time coexisting minerals melt. This effect especially for high charged, slow diffusing cations melt-rock reaction. Apparent clinopyroxene-melt partition coefficients REE, Sr, Y, Ti, Zr, measured from reprecipitated layer, approach their equilibrium values reported literature. Disequilibrium models based on volume diffusion solid limited mechanism are likely significantly underestimate rates which major elements residual reequilibrate