Lewis Cliff 87223 meteorite, Lewis Cliff, Buckley Island quadrangle, Eastern Antarctica, Antarcticai

Regional Level Types
Lewis Cliff 87223 meteorite	Meteorite Fall Location
Lewis Cliff	Cliff
Buckley Island quadrangle	Quadrangle
Eastern Antarctica	Region
Antarctica	Continent

Anomalous Enstatite Chondrite (E3-an), weathered find, 110.3 g
LEW 87057 pairing group (LEW 87057, 87220, 87233, 87234, 87285, 87294)


Recovered in 1987 Lewis Cliff 87233 (LEW 87233) is the largest of a ‘pairing group’ of 6 enstatite-rich stones (mass 156 g) which could not be clearly classified as either an EH or an EL Enstatite Chondrite. Pairing groups are stones which are believed to be fragments of a single fall — stones which have been separated both by earth impact and by the vagaries of terrestrial residence (in this case, slow movements below the ice before eventual surface exposure). The LEW 87057 pairing group is listed under the name of the first stone recovered (in this case the smallest (.4 g) of a very small lot). While the various fragments have been weathered to slitely varying degrees and show the expected variability of unequilibrated type 3 chondrites, reported results indicate that LEW 87233 is a ‘fair’ sample of the entire group.

The stone is comprised mostly of chondrule-rich silicates (~61 wt%, predominantly Clinoenstatite), metal (~23%, mostly Kamacite), and sulfides (~12%, mostly troilite) plus an assortment of minor phases (~4%). Moderately large Chondrules, presence of Alabandite, and Si content of metal (~.5%) normally would be sufficient to mark this stone as an EL Enstatite Chondrite. And the presence of minor Olivine and pryroxene variability are among several indicators of the disequilibrium expected for a more precise classification as an EL3 chondrite. But other normally dependable indicators of proper classification are lacking. This particular chondrite is too rich in iron, exhibits various trace element irregularities, and lacks the expected perryite, sphalerite, and djerfisherite usually found in type 3 Enstatite chondrites.

There may be an adequate explanation for LEW 87233 in terms of conventional assumptions (e.g. Enstatite chondrites are fragments of one/two ‘parent bodies’). Perhaps the LEW 87057 pairing group was produced by an encounter of an L chondrite with the EL3 parent body. Perhaps. However, perhaps LEW 87233 is another indicator that the putative parent bodies of the Enstatite clan — like the multiple components found in the Kaidun and Almahata Sitta meteorites — were not such well defined homeworlds as the parent bodies of meteorites from the moon, Mars, and Vesta. Perhaps the homeworlds of the Enstatite chondrites and other Enstatite-rich meteorites were still exchanging materials as they began to travel on their separate orbital ways.

Other Regions, Features and Areas containing this locality

References