Most of the grains are silicates (86 % ) with the remainder consisting of oxides (8 % ), three silica grains and two ¡®composite¡¯ grains composed of multiple subgrains with different elemental compositions. The elemental compositions of the silicates are similar to those found in other studies, with a predominance of non-stoichiometric compositions and high (up to 44 at. % ) Fe concentrations. A comparison of isotopic and elemental compositions for all presolar silicates shows that olivine compositions are overabundant in Group 4 grains compared to grains from Groups 1 and 2. This may reflect injection of presolar material from a nearby supernova into the early solar nebula and incorporation into parent bodies before alteration of compositions through irradiation and sputtering in the interstellar medium, as is likely to have occurred for the Group 1 and 2 grains from more distant AGB stars.
The matrix material in ALHA77307 contains abundant carbonaceous hotspots with excesses in 15N. However, unlike CR chondrites, the insoluble organic matter (IOM) in ALHA77307 does not have a bulk N isotopic anomaly, consistent with Raman evidence that it has experienced more processing than IOM from CR chondrites. Nevertheless, secondary processing has clearly not been so pervasive as to lead to complete destruction of N isotopic anomalies in this meteorite. Moreover, presolar silicate abundances and elemental compositions show little evidence for thermal processing, indicating a decoupling of the effects of metamorphism on organic matter and matrix silicates.