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Mg isotopic anomalies in the Allende Meteorite and correlation with O and Sr effects
Author(s) -
Lee Typhoon,
Papanastassiou D. A.
Publication year - 1974
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl001i006p00225
Subject(s) - allende meteorite , meteorite , chondrite , fractionation , isotope , analytical chemistry (journal) , isotopes of oxygen , geology , mineralogy , chemistry , radiochemistry , environmental chemistry , geochemistry , astrobiology , physics , organic chemistry , quantum mechanics
Mg isotopic anomalies were determined on inclusions in the Allende meteorite. Measured Mg isotopic ratios were corrected for mass fractionation by normalizing to the terrestrial (normal) 25 Mg/ 24 Mg. Relative to normal Mg, Allende samples show distinct isotopic anomalies which correspond to enrichment of 24 Mg or 26 Mg of up to 3 per mil or depletion of 25 Mg of up to 1.5 per mil. One sample shows a depletion of 24 Mg or 26 Mg by 1.7 per mil or an enrichment of 25 Mg by 0.85 per mil. These anomalies are smaller by a factor of ten than found for the oxygen isotopes. Samples with large oxygen effects (up to 5%) yield normal Mg indicating a lack of correlation between the O and Mg effects. A Ca‐Al rich chondrule with primitive 87 Sr/ 86 Sr and normal 84 Sr/ 86 Sr has a significant Mg anomaly. The Mg anomalies do not correlate with Al/Mg and do not appear to be due to 26 Al decay. The anomaly in the only sample depleted in 26 Mg cannot be due to 26 Al decay. The isotopic composition of Mg in a sample of the total meteorite is normal. These results accentuate the important character of Allende inclusions but do not uniquely identify the nuclear processes responsible for the Mg and O effects.