NOBLE GASES IN THE UNIQUE CHONDRITE, KAKANGARI

Abstract

The Kakangari chondrite has a cosmic‐ray exposure age of 5.4 m.y. and a K‐Ar age near 4 g.y. Its high cosmogenic 3He/21Ne ratio of 7.5 indicates a small preatmospheric mass. The He and Ne are largely of solar‐wind origin, presumably implanted during exposure in the regolith of its parent body. The heavy gases Ar, Kr, Xe are largely of planetary origin. Taken together, the low 129Xe/132Xe (1.07), low 36Ar/132Xe (225), and high 132Xe content (45 × 10−10 cc STP/g) are more similar to the values for unequilibrated ordinary chondrites or even C1, C2 chondrites than to enstatite chondrites, and suggest that Kakangari has the same gas‐bearing mineral assemblage as the former, in spite of its high degree of reduction (Fa4.9).