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Isolated olivines in the Yamato 82042 CM2 chondrite: The tracing of major condensation events in the solar nebula

 

作者: G. Kurat,   M. Mayr,   Th. Ntaflos,   A. L. Graham,  

 

期刊: Meteoritics  (WILEY Available online 1989)
卷期: Volume 24, issue 1  

页码: 35-42

 

ISSN:0026-1114

 

年代: 1989

 

DOI:10.1111/j.1945-5100.1989.tb00939.x

 

出版商: Blackwell Publishing Ltd

 

数据来源: WILEY

 

摘要:

Abstract—Yamato 82042 is an unusual CM2 chondrite consisting mainly of phyllosilicates, a few olivines and carbonates, very minor sulphides and trace metal. Olivine occurs: (1) as isolated grains dispersed in the phyllosilicate matrix, (2) as constituents of mineral aggregates or accretionary fragments associated with abundant phyllosilicates and minor sulphides, and (3) as objects which resemble barred olivine chondrules also associated with phyllosilicates. Olivine, from all occurrences, ranges in composition from 0.26 to 22.6 weight % FeO, but generally contains less than 1.25 wt.% FeO. Minor element contents, particularly Ca, Al, and Cr, are relatively high and are generally correlated, as reported for olivines in other carbonaceous chondrites. However, we report here uncorrected trends for the same minor elements which occur in distinct areas (volumes) within the same olivines. These compositional trends may be due to condensation of olivine from a vapor of non‐solar composition and partial mobilization of Ca during later annealing. If this is the case, the data may be used to trace changes in the Ca/Al ratio of the parent medium during the formation of these olivines, provided that it is possible to distinguish the effects of any post‐formation annealing which could have redistributed the minor elements. Some isolated olivines show distinctive minor element zoning which severely limits the possibility of any post‐formation redistribution of these elements. Accordingly, these isolated olivines indeed retain evidence of early condensation processes in the solar nebula, though non‐classic conditions are implied for their

 

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