MAGOMBEDZE - A NEW H-CHONDRITE WITH LIGHT-DARK STRUCTURE

Magombedze is a light-dark structured H-chondrite breccia that fell in Zimbabwe on 1990 July 2 at 15:30 GMT. White clasts are moderately sho cked and have equilibrated mafic silicates (pyroxene Fs16-18, olivine Fa18-19) together with clear optically-recognizable plagioclase of var iable composition (An9-13 found); chondrules are distinct but contain no trace of preserved glass. The darker surrounding material contains a higher proportion of fine-grained metal and sulfide than the white c lasts, and many of its constituent grains show little evidence of shoc k. Mafic silicates in the dark lithology are distinctly less-equilibra ted (pyroxene Fs5-21, olivine Fa11-20) than those in the white clasts, and many chondrules preserve brown devitrified glass; some metamorphi c plagioclase of variable composition (An11-22 found) is present. Some monoclinic pyroxene occurs in both fractions, but it is relatively co mmon in the dark fraction. The white clasts are classified as H5, and the enclosing dark material is H3-5.