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Sistemática de los isótopos de renio-osmio de las condritas carbonáceas
Science (New York, N.Y.)
|January 27, 1989
Resumen
El análisis de isótopos de renio-osmio (Re-Os) revela diferencias entre la condrita y los meteoritos de hierro. Las condritas muestran distintas edades de cierre de Re-Os, lo que sugiere variadas historias de formación en la nebulosa solar temprana.
Área de la Ciencia:
- Cosmoquímica es la cosmoquímica.
- Geocronología Geocronología.
- La geoquímica de los isótopos es la geoquímica de los isótopos.
Sus antecedentes:
- El sistema de isótopos de renio-osmio (Re-Os) es una herramienta poderosa para la datación de la formación de meteoritos.
- Estudios previos establecieron un isócrono para los meteoritos de hierro, proporcionando una referencia para las edades de cierre de Re-Os.
Objetivo del estudio:
- Para determinar las concentraciones de Re y Os y las composiciones isotópicas de Os en varios condritas y meteoritos de hierro.
- Para comparar la sistemática de isótopos Re-Os entre las condritas y los meteoritos de hierro para inferir historias de formación.
Principales métodos:
- Se empleó la espectrometría de masas de ionización por resonancia (RIMS) para la determinación precisa de las concentraciones de Re y Os y las composiciones isotópicas.
- Análisis de ocho condritas carbonáceas, una condrita ordinaria (Semarkona LL3) y dos meteoritos de hierro.
Principales resultados:
- Las proporciones de Re-Os y de isótopos de Os de los meteoritos de hierro se alinean con el isócrono del meteorito de hierro establecido.
- La mayoría de los datos de la condrita trazan un 1-2% por encima del isócrono del meteorito de hierro, lo que indica diferentes edades de cierre de Re-Os o materiales precursores.
- Las condritas específicas (Semarkona LL3, Murray C2M) se ubican significativamente más altas, lo que sugiere una posible pérdida de Re a través de la alteración acuosa o la heterogeneidad isotópica primordial.
Conclusiones:
- Las condritas y los meteoritos de hierro probablemente se formaron a partir de materiales precursores con historias químicas distintas.
- Las variaciones isotópicas observadas en algunas condritas pueden reflejar procesos de posformación como la lixiviación acuosa o las heterogeneidades isotópicas en la nebulosa solar temprana.
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