GOBABEB, A NEW CHONDRITE: THE COEXISTENCE OF EQUILIBRATED SILICATES AND UNEQUILIBRATED SPINELS

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Abstract
Gobabeb, an ordinary chondrite, was found near Gobabeb, South West Africa in 1969. Chemically and petrographically it belongs in the H4 group. But, in addition to almost homogeneous silicates and chromites, it contains rare, non‐opaque spinels that vary greatly in composition from grain to grain. A similar association in an “almost equilibrated” portion of the Mezö‐Madaras chondrite has been interpreted as evidence against the hypothesized metamorphic homogenization of ordinary chondrites. A comparison of the chromites and variable spinels from Mezö‐Madaras and Gobabeb suggests, instead, that cation exchange is simply slower in the variable spinels than in the chromites. Based on the evidence to date, the survival of these highly variable spinels is not incompatible with a metamorphic episode for both these meteorites.