Chondrules, matrix and coarse-grained chondrule rims in the allende meteorite: origin, interrelationships and possible precursor components

Journal Article · Wed Jul 01 04:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90182-7· OSTI ID:6996620

Rubin, A E; Wasson, J T

Bulk compositions of 20 chondrules, 13 coarse-grained chondrule rims and two composite samples of matrix material from CV3 Allende were determined by instrumental neutron activation analysis. Three rare nonporphyritic CV chondrules (from Allende, Leoville and Vigarano) were analyzed by broad-beam electron microprobe analysis. Chondrule precursor components deduced from chondrule compositions are characterized by: (1) refractory and semi-refractory lithophiles with low FeO, (2) common siderophiles and chalcophiles, (3) common to slightly volatile lithophiles (Si, Cr, Mn), and modal pyroxene with moderately high FeO/(FeO + MgO), (4) moderately volatile siderophiles and (5) alkalies. These precursor components can be explained by plausible processes occurring in the solar nebula. In general, the compositions of coarse-grained rims are more similar to the mean chondrule composition than to those of the chondrules they enclose. Several chondrules and rims have fractionated rare-earth patterns and may have been affected by metamorphism. The enclosure of some coarse-grained rims by fine-grained matrix-like rims indicates that coarse-grained rims were also formed in the nebula. Two matrix samples are similar in composition to some coarse-grained rims, suggesting that matrix was derived from similar compositional reservoirs of nebular dust. Chondrules with coarse-grained rims were reheated in space following the accretion of dusty coatings.

• Research Organization: Univ. of California, Los Angeles (USA)
• OSTI ID: 6996620
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:7; ISSN GCACA
• Country of Publication: United States
• Language: English

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ACTIVATION ANALYSIS
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INCLUSIONS
METAMORPHISM
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ORIGIN
PETROGRAPHY