Wb. Hsu, GEOCHEMICAL AND PETROGRAPHIC STUDIES OF OLDHAMITE, DIOPSIDE, AND ROEDDERITE IN ENSTATITE METEORITES, Meteoritics & planetary science, 33(2), 1998, pp. 291-301
In Qingzhen (EH3), oldhamite contains numerous types of inclusions and
intergrows with other phases; but in equilibrated enstatite chondrite
s and aubrites, it usually occurs as individual grains. I suggest that
oldhamite in unequilibrated enstatite chondrites (UECs) crystallized
from a melt, probably during chondrule formation. Subsequent thermal m
etamorphism on the parent bodies further modified the oldhamite occurr
ences in enstatite chondrites. This suggestion is consistent with the
results of melting experiments on UECs and aubrites and with the volat
ile element enrichments in this mineral. I analyzed minor and trace el
ement abundances in diopside from two aubrites. These data and petrogr
aphic observations suggest that diopside formed by igneous crystalliza
tion. I report the first known occurrence of roedderite in an aubrite
and its major, minor, and trace element concentrations. This mineral i
s rich in alkalis but is depleted in siderophile and refractory lithop
hile elements. A negative Sm anomaly was noted in albite from equilibr
ated enstatite chondrites and aubrites.