Anhydrous partial melting of a fertile and depleted peridotite from 2 to 30 kb and application to basalt petrogenesis

<p>Reversal experiments have been performed to check the method of Jaques & Green (1980) to determine equilibrium partial melts from peridotite compositions. Reversals of the Jaques & Green (1980) calculated equilibrium partial melt (CEPM) compositions have been carried out in two ways: (1) By running CEPM compositions at original P and T conditions and testing for multiple saturation in residual phases of the original experiments. (2) By sandwich/mixed experiments using the CEPM composition plus peridotite (either Hawaiian pyrolite or Tinaquillo lherzolite). </p> <p>The glass (liquid) compositions from the first series of experiments show that the CEPM compositions of Jaques & Green (1980) are too olivine-rich. The glass (liquid) compositions from the second series of experiments define new olivine+orthopyroxene±clinopyroxene cotectics in a molecular normative tetrahedron. The new cotectics plot towards the Qz apex of the tetrahedron, away from the cotectics defined by the CEPM compositions of Jaques & Green (1980). Partial melt compositions have also been determined at 20 and 30 kb, using both the sandwich technique and the approach by modal analysis and mass balance. </p> <p>The results of the experimental study are used to evaluate the petrogenesis of mid-ocean ridge basalts, Hawaiian tholentes and primary magmas in intraoceanic convergent margin settings.</p>