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Metamorphism of the H-group chondrites - Implications from compositional and textural trends in chondrulesThe paper discusses element bulk compositions of 373 chondrules from 18 H3 to H6 chondrites determined by broad-beam electron probe analysis. Bulk chondrule FeO and Al2O3 amounts increase and TiO2 and Cr2O3 decrease with increasing petrologic type; normative faylite, albite, and plagioclase amounts increase through the petrologic sequence. Chondrule diameters correlate with phenocryst sizes in porphyritic chondrules of type 3 chondrites, but this correlation is diminished in the higher petrologic types. The compositional trends in chondrules through the petrologic sequence are attributed to diffusion and equilibration among chondrules, and between chondrules and matrix in response to increasing degrees of thermal metamorphism. It is suggested that H-group chondrites are formed by accretion of high-temperature (chondrules) and low-temperature (matrix) materials. Internal reheating of the parent materials to different temperatures caused compositional equilibration, grain coarsening, and reduction of FeO to Fe(0) by carbon.
Document ID
19800056699
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Lux, G.
(New Mexico Univ. Albuquerque, NM, United States)
Keil, K.
(New Mexico Univ. Albuquerque, NM, United States)
Taylor, G. J.
(New Mexico, University Albuquerque, N. Mex., United States)
Date Acquired
August 10, 2013
Publication Date
June 1, 1980
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 44
Subject Category
Lunar And Planetary Exploration
Accession Number
80A40869
Funding Number(s)
CONTRACT_GRANT: NGL-32-004-064
Distribution Limits
Public
Copyright
Other

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