Key points are not available for this paper at this time.
A new thermodynamic model is presented for calculating phase relations in peridotite, from 0 001 60 kbar and from 800 C to liquidus temperatures, in the system NCFMASOCr. This model system large enough to simulate phase relations and melting of natural peridotite and basaltic liquids. in the program THERMOCALC illustrate mantle phase relationships and melting conditions, for the peridotite composition KLB-1. The garnet–spinel transition zone intersects solidus at 21 4–21 7 kbar, where both Fe3þ and Cr increase spinel stability, expanding the width the transition. Orthopyroxene is lost at the solidus at 42 kbar in KLB-1, although this pressure is sensitive to bulk composition. Calculated oxidation states are in excellent agreement with log fO2 for xenolith suites with mantle Fe2O3 contents in the range 0 1–0 3wt %. It that mantle oxidation state is not just a simple function of P and T, but depends on phase, and may vary in a complex way within a single assemblage. The liquid model well, such that calculated solidus, melt productivity and liquid compositions compare with those of experimental studies, permitting its use in interpolating between, and from, experimental P–T conditions. Experimentally challenging but geologically regimes can be explored, such as subsolidus samples and very low melt fractions, with to both mantle xenoliths and the origin of basalt.
Jennings et al. (Fri,) studied this question.