Continued Experimental Studies of Mantle Melting

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9804913JohnstonIn this continuation of an earlier project (EAR-9506045) at 10 kbar pressure, we will study experimentally the melting systematics of the Earth's mantle at 20 kbar pressure, using natural minerals as starting materials and layers of vitreous carbon spheres as a melt sinks within our graphite-lined Pt capsules. Our goal is to assess the effects of variable mode and compositional fertility on the solidus temperatures of different types of mantle, the near-solidus melt compositions, and the rates of melt productivity with increasing temperature. We will study eight starting materials constructed from hand-picked mineral separates: four from a fertile spinel lherzolite xenolith and four others from an compositionally intermediate spinel lherzolite. Modes will approximate "average" mantle, and mantle that is enriched in clinopyroxene, orthopyroxene, or Cr-spinel.