PETROLOGIC CHARACTERIZATION OF A SAHARA METEORITE

This study examines a 294 gram unclassified stony meteorite from the Sahara Desert. Compilation of both petrologic and chemical data, this meteorite was classified as an ordinary chondrite LL6, S5-6.

Preliminary exterior examination revealed a heavily fractured surface comprising a regmaglypt covered fusion crust with well defined areas of varying maturation resulting from partial disintegration during rapid deceleration through the atmosphere. The specimen is also moderately magnetic, characteristic of many meteorites.

A cut and polished interior uncovers a brecciated and highly fractured surface containing a network of metallic shock-veins throughout the meteorite. Back scattered electron (BSE) imaging reveals multiple cross-cutting relationships which provide evidence that the meteorite experienced at least three distinct impacts prior to its arrival on Earth. BSE imaging and electron dispersive analysis (EDS) further reveal a small number of well preserved chondrules composed of either barred olivine or pyroxene, many of which are cross-cut by the shock-veins. The lack of chondrules is likely the result of both thermal metamorphism and brecciation.

A whole rock analysis was obtained by averaging the results of a 20 x 62 grid of EDS spot analyses. Total iron content is approximately 19 wt. %, placing the meteorite in the low metal-low iron class, LL, of ordinary chondrites. The extent of metamorphism leaves few distinguishable chondrules, making it a petrologic type 6. The highly brecciated character indicates a shock value of S5 to S6.