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Los registros de sulfato asociado al carbonato de los neoarqueos muestran anomalías Δ33S positivas
G Paris1, J F Adkins2, A L Sessions2
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. gparis@caltech.edu.
Science (New York, N.Y.)
|November 8, 2014
Resumen
El análisis de isótopos de azufre de carbonatos neoarqueanos revela inesperadas señales positivas de fraccionamiento independiente de la masa (Δ(33) S), lo que desafía las suposiciones anteriores sobre la atmósfera y la composición de sulfatos de la Tierra primitiva.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Paleoclimatología Paleoclimatología
- Las condiciones de la Tierra primitiva.
Sus antecedentes:
- Los isótopos de azufre (Δ(33) S) en las rocas arqueas informan la composición temprana de la atmósfera y los eventos de oxigenación.
- Las hipótesis predicen Δ(33) S negativo para el sulfato de agua de mar del Arcaico, pero esto permanece en gran parte sin probar para la mayor parte del Eón Arcaico.
Objetivo del estudio:
- Para investigar las firmas Δ(33) S en carbonatos neoarqueanos.
- Para probar la hipótesis prevaleciente de Δ(33) S uniformemente negativo en el sulfato de agua de mar de Arqueo.
Principales métodos:
- Espectroscopia de absorción de rayos X para analizar el bajo contenido de sulfatos en carbonatos neoarqueanos.
- Espectrometría de masas para medir las firmas del isótopo de azufre (Δ(33) S.
Principales resultados:
- Se detectaron valores inesperados, grandes y muy extendidos de Δ(33) S positivo en carbonatos neoarqueanos.
- Estos hallazgos abarcan más de 70 millones de años y diversos entornos de deposición.
- El registro de sulfato no exhibe el esperado negativo Δ(33) S de fraccionamiento independiente de la masa de azufre atmosférico.
Conclusiones:
- El sulfato de agua de mar de Archean no lleva consistentemente la señal Δ(33) S negativa predicha.
- Esto desafía los modelos existentes del ciclo del azufre y la composición atmosférica en el Eón Neoarqueo.
- Se justifica la reevaluación de los procesos de fraccionamiento independientes de la masa de azufre en la atmósfera temprana de la Tierra.
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