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Evidencia de la supervivencia del más antiguo depósito del manto terrestre

Matthew G Jackson¹, Richard W Carlson, Mark D Kurz

¹Department of Earth Sciences, Boston University, 675 Commonwealth Avenue, Boston, Massachusetts 02215, USA. jacksonm@bu.edu

|August 13, 2010

Resumen

El material primitivo del manto, trazado por isótopos de helio en las lavas de la isla de Baffin y el oeste de Groenlandia, revela edades de fuentes antiguas. Estas lavas proporcionan evidencia del depósito de manto accesible más antiguo de la Tierra, que data de hace 4.55 a 4.45 mil millones de años.

Área de la Ciencia:

La geoquímica es la geoquímica.
Geología de Isótopos Geología de Isótopos.
Ciencias de la Tierra Ciencias de la Tierra Ciencias de la Tierra

Sus antecedentes:

Los isótopos de helio (3He/4He) son trazadores clave para el material primitivo del manto terrestre.
Los basaltos de las islas oceánicas con altas proporciones de 3He/4He sugieren depósitos de manto sin gas.
Estudios anteriores carecían de composiciones primitivas de isótopos de plomo para confirmar las edades antiguas de formación del manto.

Objetivo del estudio:

Para investigar la composición isotópica de la lava del Cenozoico de la isla de Baffin y el oeste de Groenlandia.
Para determinar si estas lavas albergan composiciones isotópicas primitivas de plomo.
Para establecer la edad de formación de la fuente del manto para estas antiguas lavas.

Principales métodos:

Análisis de las proporciones de helio (3He/4He), isótopo de plomo y isótopo de neodimio (143Nd/144Nd) en las lavas.
Comparación de datos isotópicos con modelos para la formación temprana del manto terrestre.
Interpretación geocronológica de las firmas isotópicas.

Principales resultados:

Las lavas de la isla de Baffin y el oeste de Groenlandia exhiben las proporciones más altas de 3He/4He entre el manto terrestre.
Estas lavas poseen relaciones primitivas de isótopos de plomo, lo que indica una antigua edad de la fuente del manto de 4.55 a 4.45 mil millones de años.
Las lavas también muestran proporciones de 143Nd/144Nd consistentes con un depósito del manto terrestre de unos 4.500 millones de años.

Conclusiones:

Los datos isotópicos combinados sugieren que las lavas de la isla de Baffin y el oeste de Groenlandia se originan en el depósito de manto accesible más antiguo de la Tierra.
Este antiguo depósito puede ser el padre de todos los depósitos modernos del manto volcánico.
Los hallazgos proporcionan una fuerte evidencia de la preservación de material formado temprano dentro del manto de la Tierra.

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