Isotopic fractionation of silicon in Allende inclusionsThe variations of Si-30/Si-28 and Si-29/Si-28 in Allende inclusions are large, and are due predominantly to mass-dependent fractionation effects. Gas-soild or gas-liquid condensation processes at high temperatures have sufficiently large fractionation factors to account for the heavy-isotope enrichments in coarse-grained inclusions. Heavy isotope depletions are found in some Allende samples, and apparently result from a late-stage condensation. Thus, the silicon isotopic compositions may be useful for determining the sequence of events in forming the Allende meteorite. The peculiar Allende inclusion, Cl, has a very large mass-fractionated enrichment of Si-30/Si-28, and in addition, perhaps a small nuclear enrichment of Si-29. Olivine from the unusual pallasite, Eagle Station, has normal silicon isotope abundances even though it has a large O-16 excess.
Document ID
19790055153
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Clayton, R. N. (Chicago Univ. Chicago, IL, United States)
Mayeda, T. K. (Chicago, University Ill., United States)
Epstein, S. (California Institute of Technology Pasadena, Calif., United States)