Soils from the Soviet Luna 24 mission to Mare Crisium contain fragments of ferrobasalt and ferrogabbro. The ferrobasalt is very low in Ti content (~1.0 wt.% TiO2), similar to very low Ti ''VLT'' basalts from Apollo 17. It is characterized by Mg/(Mg+Fe) ~0.3--0.4, Al2O3~13%, CaO~13%, and Cr2O3~0.2--0.3%. Brown glasses and micropoikilitic fragments similar to the ferrobasalt occur in the Crisium soils, and green glasses similar to the Apollo 17 VLT basalt have been found. There is growing evidence that very low Ti basalts may be an abundant mare basalt type; there is a possibility that this suite may be derived by crystal fractionation from magma similar to green glass in composition. |