CHONDRITE MELTING EXPERIMENTS: CAN ANGRITE LEW87051 BE PRODUCED BY PARTIAL MELTING OF A CV OR CM CHONDRITE? A.J.G Jurewicz

Introduction: LEW2 consists of abundant, coarse subhedral to euhedral olivine crystals (-FOG()90, typical grainsize -0.5mm) set in a fine-grained intergranular groundmass composed primarily of plagioclase, olivine, and Ca-A1 pyroxene [eg. 1,2]. The groundmass clearly represents a crystallized melt [3,4]. McKay et al. [6] proposed that this interstitial groundmass melt was produced by fractional crystallization of the large olivine crystals from a more olivinerich melt. They created a "reverse fractional crystallization" model, using major and minor element partition coefficients from phase-equilibria experiments on a synthetic LEW2 analog, to calculate the compositions of liquids along the fractional crystallization path leading to the LEW2 groundmass, and the compositions of the resulting olivine phenocrysts. The model reproduced the Cr and Ca zoning patterns of the largest LEW2 olivines, with the exception of small cores. McKay et al.J6] proposed a specific composition for the olivine-rich parent melt, with a liquidus near 1320 C.