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La composición isotópica del cloro del manto de la Tierra
M Bonifacie1, N Jendrzejewski, P Agrinier
1Equipe de Physico-Chimie des Fluides, Géologiques, Institut de Physique du Globe de Paris (IPGP) and Université Paris, Diderot (UPD), CNRS-INSU-Unité Mixte de Recherche (UMR) 7154, 75251 Paris Cedex 05, France. bonifaci@gps.caltech.edu
Science (New York, N.Y.)
|March 15, 2008
Resumen
La mayoría de las lavas oceánicas muestran contaminación por cloro, con proporciones de isótopos (delta37Cl) que revelan la influencia del agua de mar o la salmuera. Las fuentes de manto no contaminadas tienen valores de delta37Cl significativamente más bajos que los depósitos de superficie.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Geología de Isótopos Geología de Isótopos.
- Petrología Petrología.
Sus antecedentes:
- Las composiciones de isótopos estables de cloro (Cl) (delta37Cl) en los basaltos de la cresta oceánica media (MORB) proporcionan información sobre los procesos del manto.
- Comprender las fuentes de CI y el ciclo es crucial para descifrar el inventario volátil de la Tierra.
Objetivo del estudio:
- Para investigar la relación entre el contenido de Cl y delta37Cl en MORBs.
- Para determinar la firma delta37Cl del manto de la fuente MORB no contaminada.
- Para evaluar el grado de contaminación de la corteza en las lavas oceánicas.
Principales métodos:
- Análisis de las composiciones de isótopos estables del cloro (delta37Cl) en 22 muestras MORB.
- Correlación de los valores de delta37Cl con el contenido de Cl a granel.
Principales resultados:
- Existe una correlación positiva entre el delta37Cl y el contenido de Cl en MORBs.
- Los basaltos altos en delta37Cl y ricos en Cl están contaminados por materiales ricos en Cl como el agua de mar o las salmueras.
- Los basaltos bajos en delta37Cl y pobres en Cl representan magmas menos contaminados derivados del manto.
Conclusiones:
- La mayoría, si no todas, las lavas oceánicas están contaminadas hasta cierto punto.
- El manto de la fuente MORB tiene un delta 37Cl significativamente más bajo (-1,6 por mil) en comparación con los depósitos de superficie (~0 por mil).
- La diferencia isotópica sugiere fraccionamiento isotópico neto de Cl durante la historia de la Tierra o una adición volátil enriquecida con 37Cl tardía.
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