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La evidencia del isótopo de hafnio para una transición en la dinámica del crecimiento continental hace 3,2 Gyr
T Næraa1, A Scherstén, M T Rosing
1Geological Survey of Denmark and Greenland, GEUS, Øster Voldgade 10, 1350 Copenhagen K, Denmark. tomn@geus.dk
Nature
|June 5, 2012
Resumen
Tierra temprana de la Tierra temprana.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- La tectónica es la tectónica.
- Geología de Isótopos Geología de Isótopos.
Sus antecedentes:
- La litosfera de la Tierra evolucionó hacia la tectónica de placas moderna debido a los cambios de temperatura del manto.
- El crecimiento de la corteza continental disminuyó con el tiempo, con la mayor parte extraída por el eón Arcaico.
- Los ciclos de los supercontinentes influyeron en el crecimiento de la corteza terrestre y su reelaboración después de tres mil millones de años.
Objetivo del estudio:
- Investigar el inicio de regímenes tectónicos modernos en la corteza temprana de la Tierra.
- Analice los datos de isótopos de circón de las rocas del sótano del suroeste de Groenlandia.
- Determinar el momento de las transiciones en la dinámica de la litosfera.
Principales métodos:
- Análisis in situ de isótopos de uranio y plomo de los zircones.
- Análisis in situ del isótopo de hafnio de los zircones.
- Análisis in situ de isótopos de oxígeno de circones.
Principales resultados:
- Los patrones de tiempo isotópico del hafnio revelan cambios en las características del protolito magmático.
- Rocas de 3.9-3.5 mil millones de años (Gyr) derivadas de una fuente condrítica a agotada.
- Las rocas menores de 3.2 Gyr muestran adiciones de material empobrecido juvenil, similar a los orógenos del Fanerozoico.
Conclusiones:
- Un período de transición (3,5-3,2 Gyr hace) marca un cambio de la antigua evolución de la corteza terrestre a la moderna tectónica de placas.
- La corteza temprana (3.9-3.5 Gyr) se formó bajo un régimen diferente a la tectónica de placas moderna.
- La generación de la corteza post-3.2 Gyr involucró procesos tectónicos de placas y la formación de la corteza juvenil.
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