High-pressure experiments on magnesian eucrite compositions - Constraints on magmatic processes in the eucrite parent body

Melting experiments were conducted on synthetic analogs of two magnesian eucrite clasts from howardites, Kapoeta clast rho and Yamato 7308 pigeonite-eucrite clast 1, at 1 atm and 1-kbar pressure at oxygen fugacities in the range of iron-wuestite (IW) to iron-quartz-fayalite (IQF). The compositions of liquids and coexisting minerals (olivine-low-Ca pyroxene-plagioclase spinel) were used to constrain possible melting and crystallization processes in the parent bodies of eucrite basalts. In agreement with previous studies, the experimental results at 1 atm indicate that the olivine-low-Ca pyroxene-plagioclase-spinel-liquid and olivine-low Ca pyroxene-spinel-liquid boundaries are reaction boundaries involving olivine. At 1 kbar, however, the olivine primary-phase volume shrinks, and the reaction relationship involving olivine disappears for both boundaries. The maximum pressure attained in a Vesta-sized eucrite parent body (EPB) is about 1 kbar, and these results provide important constraints on models relating the howardite-eucrite-diogenite (HED) meteorite association through melting and differentiation processes.