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Volatile/mobile trace elements in Bholghati howardite

Journal Article · · Geochimica et Cosmochimica Acta; (USA)
OSTI ID:6147281

The authors 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 ({triple bond}CI) levels, other are in the C2 ({triple bond}CM) range, while still others are at C3 ({triple bond}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.

OSTI ID:
6147281
Journal Information:
Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 54:8; ISSN GCACA; ISSN 0016-7037
Country of Publication:
United States
Language:
English