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¿Un soplo de oxígeno antes del gran evento de oxidación?
Ariel D Anbar1, Yun Duan, Timothy W Lyons
1School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA. anbar@asu.edu
Science (New York, N.Y.)
|September 29, 2007
Resumen
Los primeros océanos de la Tierra contenían oxígeno más de 50 millones de años antes del Gran Evento de Oxidación, indicado por el enriquecimiento de molibdeno y renio en esquisto antiguo. Esto sugiere oxígeno atmosférico temprano, impactando nuestra comprensión de los entornos Arqueos.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- La paleoceanografía es la paleoceanografía.
- Las condiciones de la Tierra primitiva.
Sus antecedentes:
- El Gran Evento de Oxidación (GOE) marcó un aumento significativo en el oxígeno atmosférico.
- Las condiciones ambientales que precedieron al GOE no se comprenden completamente.
- Los metales sensibles a los redox pueden servir como sustitutos para la química oceánica antigua.
Objetivo del estudio:
- Para investigar la presencia de metales sensibles al redox en el esquisto de la montaña McRae del Arcaico tardío.
- Para determinar el origen y el momento del enriquecimiento de metales.
- Para evaluar las implicaciones para los niveles de oxígeno atmosférico de la Tierra temprana.
Principales métodos:
- Quimiostratigrafía de alta resolución para analizar las concentraciones de metales.
- Correlación con el carbono orgánico para inferir fuentes metálicas.
- La geocronología del renio/osmio para fechar la característica sedimentaria.
Principales resultados:
- Enriquecimiento de molibdeno y renio descubierto en el Monte McRae Shale.
- Enriquecimiento metálico correlacionado con carbono orgánico, indicando el origen del agua de mar.
- La datación por renio/osmio sitúa el enriquecimiento en 2501 +/- hace 8 millones de años.
- La evidencia sugiere que los metales fueron suministrados por el desgaste oxidativo de los sulfuros.
Conclusiones:
- El Monte McRae Shale registra un episodio temprano de enriquecimiento de metales a partir del agua de mar.
- Este enriquecimiento es anterior al Gran Evento de Oxidación por más de 50 millones de años.
- Los hallazgos indican la presencia de oxígeno localizado en el entorno del Arcaico tardío.
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