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La evidencia de neodimio-142 para la corteza máfica del Hadeano
Jonathan O'Neil1, Richard W Carlson, Don Francis
1Earth and Planetary Sciences Department, McGill University, 3450 University Street, Montreal, Quebec, H3A 2A7, Canada. oneil_jo@eps.mcgill.ca
Science (New York, N.Y.)
|September 27, 2008
Resumen
Los investigadores descubrieron antiguas rocas en Canadá con firmas únicas de isótopos de neodimio. Estos hallazgos sugieren que las rocas se formaron poco después de la formación de la Tierra, representando potencialmente la corteza más antigua del planeta.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Geología de Isótopos Geología de Isótopos.
- Estudios de la Tierra Temprana Estudios de la Tierra Temprana
Sus antecedentes:
- Las anomalías del isótopo del neodimio-142 (142Nd) proporcionan información sobre la diferenciación planetaria temprana.
- El cinturón de piedra verde Nuvvuagittuq en Quebec, Canadá, es un sitio clave para el estudio de antiguas rocas de la corteza terrestre.
Objetivo del estudio:
- Para investigar la composición isotópica de las rocas del cinturón de piedra verde Nuvvuagittuq.
- Determinar la edad y el origen de material cortical potencialmente antiguo.
Principales métodos:
- Análisis de las proporciones de isótopos de neodimio (Nd) y samario (Sm) (142Nd/144Nd y Sm/Nd) en muestras de rocas.
- Datación radiométrica mediante el método isocrón 146Sm-142Nd.
Principales resultados:
- Algunas rocas de Nuvvuagittuq exhiben proporciones más bajas de 142Nd/144Nd que el estándar terrestre (epsilon142Nd = -0.07 a -0.15).
- Se observó una correlación positiva entre las relaciones 142Nd/144Nd y Sm/Nd dentro de una unidad de anfibolita máfica.
- Se determinó una edad isocrónica de 146Sm-142Nd de 4,280 ± 53 millones de años para esta unidad.
Conclusiones:
- Las rocas analizadas representan material enriquecido con elementos incompatibles formado muy temprano en la historia de la Tierra.
- Estos hallazgos sugieren que el cinturón de piedra verde Nuvvuagittuq puede preservar la sección de corteza más antigua de la Tierra.
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