Shaw meteorite: water-poor and water-rich melt inclusions in olivine and enstatite

During the petrological examination of a double polished thick section of the light-colored lithology of the Shaw meteorite, small melt inclusions, typically with diameters between 10 and 35 μm, were discovered in olivine and orthopyroxene crystals. These inclusions represent two different types of melt inclusions, one low in water (0.57% (g/g)) and the other with extremely high concentrations (15% (g/g)). Extremely water-rich inclusions were also found in olivine, which showed bulk water concentration is between 12 and 13% (g/g). Given the high D₂O-concentration of (556 ± 47) ppm and a D/H ratio of (337 ± 32 × 10⁻⁶) in the glass phase of the water-rich melt inclusions terrestrial contamination can be excluded. Given the bulk water concentration of the Shaw meteorite is about 1%, typical of L-group chondrites, we propose that the high water concentrations found in some melt inclusions was injected into the melt from a melted projectile during an impact event. As the projectile a Cl-type chondrite with high water concentration is highly probable.