Origin of SNC kaersutitic amphibole: Experimental data

The SNC meteorites, a group of cumulus textured, fine grained diabases, pyroxenites, and dunites, appear to have crystallized at relatively shallow depths on the same SNC parent body. Hydrous minerals generally are not present among the cumulus and intercumulus minerals in these meteorites except for some iddingsite alteration of olivine. The presence of hydrous magmatic amphibole in the SNC melt inclusions indicates that crystallization of the melt inclusions had to take place at significant pressure, probably greater than 1 kb based on previous amphibole stability data. If experimental data for kaersutite amphibole were to be obtained, it should be possible to estimate this pressure more precisely then previously, and to estimate the volatile (H2O) content of the parent magma. At this point, the factors controlling the chemistry and stability of high TiO2, kaersutitic amphiboles are not known. In an attempt to determine the factors which control the stability and chemistry of TiO2-rich amphibole, data was refined and extrapolated from four experimental studies of amphibole-melt equilibria recently completed. At the same time, hypothermal experiments were performed on a composition considered to be an early melt in the Shergotty magma liquid line of descent. The latter experiments were an attempt to reproduce crystallization of the amphibole-bearing melt inclusions.