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Deposición de formaciones de hierro de 1.88 mil millones de años de antigüedad como consecuencia del rápido
Birger Rasmussen1, Ian R Fletcher, Andrey Bekker
1Department of Applied Geology, Curtin University, Kent Street, Bentley, Western Australia 6102, Australia.
Nature
|April 28, 2012
Resumen
La reaparición de las formaciones de hierro hace alrededor de 1.88 mil millones de años estuvo relacionada con el aumento de la actividad del manto y el vulcanismo. Esto liberó hierro, creando temporalmente condiciones oceánicas ferruginosas a pesar del aumento de los niveles de oxígeno atmosférico.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- La sedimentología sedimentológica.
- La paleoceanografía es la paleoceanografía.
Sus antecedentes:
- Las formaciones de hierro (rocas sedimentarias químicas) requieren agua marina anóxica y rica en hierro.
- Su deposición cesó después de que el oxígeno atmosférico aumentó hace ~ 2.32 mil millones de años.
- Una reaparición ~500 millones de años después presenta un rompecabezas científico.
Objetivo del estudio:
- Para investigar la causa de la formación tardía de deposición de hierro en el Paleoproterozoico.
- Para determinar si las formaciones de hierro australianas eran contemporáneas con las norteamericanas.
- Para vincular la deposición de la formación del hierro a los eventos geológicos globales.
Principales métodos:
- Datamiento con circón de capas de tufo dentro de la Formación Frere, Australia Occidental.
- Análisis geoquímico de las capas de roca.
- Correlación con datos globales de actividad geológica y del manto.
Principales resultados:
- La datación confirmó que las formaciones de hierro australianas tienen ~1.88 mil millones de años, contemporáneas con las formaciones norteamericanas.
- Esta deposición contemporánea sugiere que la química oceánica global influyó en la formación de hierro.
- El evento coincidió con picos en la actividad del manto, la formación de la corteza y la formación de sulfuro masivo volcanogénico.
Conclusiones:
- El vulcanismo submarino mejorado y la actividad hidrotermal liberaron hierro, oxidantes abrumadores del océano.
- Esto causó un retorno temporal de las condiciones ferruginosas, desacoplando los estados redox atmosféricos y oceánicos.
- La posterior disminución de las formaciones de hierro probablemente refleja la disminución de la actividad del manto y el flujo de hierro hidrotermal.
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