Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published September 1978 | Published
Journal Article Open

Search for ^(26)Al effects in the Allende Fun Inclusion C1


The Mg isotopic composition in plagioclase from the Allende inclusion C1 has been measured to correlate excess ^(26)Mg^* with isotopic anomalies for elements of higher atomic number. No large ^(26)Mg^* excesses were observed in samples with ^(27)Al/^(24)Mg up to 165. The inferred initial ^(26)Al/^(27)Al is 5 × 10^(−6) which is a factor of ten less than previously observed in other Allende inclusions. The low ^(26)Al abundance may be the result of late formation of C1 (by 2.5 m.y.) or due to the non-uniform addition of ^(26)Al to the solar system. The major mineral phases in C1 which are Mg rich and the bulk alteration products all have a uniform Mg isotopic composition with 30‰ per mass unit fractionation and δ^(26)Mg≈ −1.6‰. The plagioclase data show variable Mg isotopic fractionation which ranges from 0 to 30‰ per mass unit. Isotopic homogeneity was demonstrated for the major mineral phases rich in Mg both in macroscopic samples and in microscopic individual crystals. The detailed correlation of ^(26)Al with the more general isotopic anomalies and its use as a chronometer marking the production and introduction of isotopically anomalous material into the solar system remains an open question.

Additional Information

© 1978 American Geophysical Union. Received June 13, 1978; accepted July 17, 1978. We thank A. L. Albee for ready access to the electron microprobe facility and R. L. Lewis for generous assistance in the use of the scanning electron microscope. The paper benefited greatly from constructive detailed reviews by J. H. Reynolds and L. E. Nyquist T. L. thanks the Enrico Fermi Institute of the University of Chicago and the Robert R. McCormick Trust for allowing him the freedom to complete the final phase of this work at Caltech. This work was supported by NASA NGL 05-002-188 and NSF 76-83685. This is contribution 3106 (277) of the Division of Geological and Planetary Sciences.

Attached Files

Published - grl850.pdf


Files (423.4 kB)
Name Size Download all
423.4 kB Preview Download

Additional details

August 19, 2023
October 25, 2023