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La evidencia de isótopos de oxígeno de antiguos zircones para el agua líquida en la superficie de la Tierra hace
S J Mojzsis1, T M Harrison, R T Pidgeon
1Department of Earth and Space Sciences and IGPP Center for Astrobiology, University of California Los Angeles, 90095-1567, USA. Steve.Mojzsis@lasp.colorado.edu
Nature
|February 24, 2001
Resumen
Los antiguos zircones de Australia Occidental sugieren que la Tierra primitiva tenía agua superficial. Estos restos minerales de 4.300 millones de años indican la presencia de una hidrosfera que interactúa con la corteza continental durante las etapas de formación del planeta.
Área de la Ciencia:
- Geología Geología Geología.
- La geoquímica es la geoquímica.
- Ciencias planetarias Ciencias planetarias.
Sus antecedentes:
- Las exposiciones más antiguas de la corteza continental tienen entre 3,8 y 4,0 mil millones de años.
- La comprensión de las primeras condiciones de la superficie de la Tierra requiere el análisis de rocas o restos minerales de más de 4 mil millones de años.
Objetivo del estudio:
- Para investigar las condiciones de la superficie de la Tierra hace más de 4 mil millones de años.
- Para limitar la edad y la composición de las antiguas fuentes de circón.
- Para proporcionar información sobre la naturaleza de la superficie de la Tierra temprana.
Principales métodos:
- La datación in situ con uranio y plomo (U-Pb) de los zircones detritales.
- Análisis del isótopo de oxígeno (delta18O) de los zircones detritales.
- Análisis de circones encontrados dentro de rocas cuarcíticas de 3 mil millones de años de antigüedad en Australia Occidental.
Principales resultados:
- Los circones fechados tienen entre 3.910 y 4.280 millones de años.
- Los valores de isótopos de oxígeno (delta18O) variaron entre el 5,4 ± 0,6% y el 15,0 ± 0,4%.
- Circones de aproximadamente 4.300 millones de años probablemente se formaron a partir de magmas con una corteza continental significativamente reelaborada.
Conclusiones:
- La presencia de agua cerca de la superficie de la Tierra está indicada por la composición isotópica de los antiguos zircones.
- Estos hallazgos apoyan la existencia de una hidrosfera que interactúa con la corteza hace ya 4.300 millones de años.
- El estudio proporciona evidencia de la evolución temprana de la corteza terrestre y la presencia de agua superficial en la Tierra primordial.
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