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Calibración del reloj de lutecio-hafnio
E Scherer1, C Munker, K Mezger
1Institut für Mineralogie, Universität Münster, Corrensstrasse 24, 48149 Münster, Germany. escherer@nwz.uni-muenster.de
Science (New York, N.Y.)
|July 28, 2001
Resumen
Nuevas mediciones refinan la constante de desintegración del lutecio-176 (λ176Lu), lo que tiene un impacto en la geocronología. Esta constante revisada sugiere que la Tierra es la Tierra.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Geocronología Geocronología.
- Geología de Isótopos Geología de Isótopos.
Sus antecedentes:
- Las constantes de desintegración radiactiva son cruciales para la geocronología y la comprensión de la diferenciación planetaria.
- Las constantes de desintegración exactas son esenciales para la datación de rocas y minerales antiguos.
Objetivo del estudio:
- Para determinar con precisión la constante de desintegración del lutecio-176 (λ176Lu) a través de la calibración con esquemas de desintegración de uranio y plomo.
- Reevaluar las edades del lutecio-hafnio (Lu-Hf) y las composiciones isotópicas iniciales del hafnio utilizando la nueva constante de desintegración.
Principales métodos:
- Se realizaron cuatro nuevas determinaciones de la constante de desintegración del lutecio-176 (λ176Lu).
- La calibración se llevó a cabo en contra de los esquemas de desintegración de uranio-plomo establecidos.
- La nueva constante de desintegración se aplicó para calcular las edades de Lu-Hf y las composiciones isotópicas iniciales de Hf.
Principales resultados:
- Se determinó un nuevo valor medio para la constante de desintegración del lutecio-176 (λ176Lu) como 1.865 ± 0.015 x 10-11 años-1.
- Este valor se alinea con los experimentos recientes de conteo de desintegración, pero difiere de los valores utilizados anteriormente.
- Las edades de Lu-Hf calculadas con la antigua constante son aproximadamente un 4% más jóvenes que las derivadas de la nueva constante.
Conclusiones:
- Las edades de Lu-Hf calculadas anteriormente son sistemáticamente demasiado jóvenes.
- Las composiciones iniciales de isótopos de hafnio de antiguos materiales terrestres son menos radiogénicas de lo que se pensaba anteriormente.
- La existencia de hafnio no radiogénico en los circones del Hadeano y el Arcaico Temprano indica una diferenciación temprana de la corteza hace 4.300 millones de años, lo que requiere revisiones a los modelos de diferenciación de la Tierra temprana.
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