Abstract
We determined Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U, and Zn by RNAA in two kinds of material from the Bholghati howardite: a carbonaceous chondrite clast (BH-4) that originated by primary nebular condensation/accretion processes; whole-rock samples and clasts resulting from parent-body processes, especially igneous differentiation. The trace element pattern for clast BH-4 is inconsistent with its petrologic characteristics that suggest a CM classification. Trace elements are at chondritic levels in BH-4: some exceed C1 (&z.tbnd;CI) levels, others are in the C2 (&z.tbnd;CM) range, while still others are at C3 (&z.tbnd;CO, CV) levels. The pattern observed will not conform to a C2-one even if thermal devolatilization or enrichment is invoked. Either CM chondrites are chemically heterogeneous at the 3-mg size level or BH-4 is carbonaceous chondrite material different from those of discrete meteorites. How many other CM clasts classified petrologically in >40 meteorites would be corroborated as CM by trace element or oxygen isotopic study? Trace element contents in Bholghati whole-rock (matrix) samples and/or white eucritic clasts in it are high for an achondrite, and variable. These characteristics are indicative of random condensation of volcanic emanations admixed with pre-existing eucrite, diogenite, and howardite layers in the HED parent body. Other HED samples show similar patterns, and the conclusion that these reflect extensive volcanism in an asteroidal-sized object is supported by other Consortium noble gas and cosmochronologic measurements.
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