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Influencia atmosférica del ciclo de azufre más antiguo de la Tierra
1Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA. E-mail: jfarquha@ucsd.edu (J.F. ); hbao@ucsd.edu (H.B.); and MHT@chem.ucsd.edu (M.T.).
Science (New York, N.Y.)
|August 5, 2000
Resumen
El ciclo del azufre del Precámbrico cambió significativamente entre hace 2090 y 2450 millones de años. Antes de este período, las reacciones atmosféricas, no la actividad microbiana, dominaban el ciclo del azufre debido a los bajos niveles de oxígeno.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Paleoclimatología Paleoclimatología
- Geología de Isótopos Geología de Isótopos.
Sus antecedentes:
- El ciclo del azufre es un indicador crítico de las primeras condiciones de la Tierra.
- Las firmas isotópicas de azufre independientes de la masa (delta(33) S, delta(34) S, delta(36) S) proporcionan información sobre los procesos atmosféricos.
- Comprender el ciclo del azufre del Precámbrico es clave para reconstruir la composición atmosférica temprana y la actividad biológica.
Objetivo del estudio:
- Para investigar la evolución del ciclo del azufre durante la era precámbrica.
- Para determinar el momento de un cambio significativo en los mecanismos del ciclo del azufre.
- Para evaluar la influencia de la química atmosférica frente a los procesos biológicos en los isótopos de azufre.
Principales métodos:
- Análisis de las firmas isotópicas independientes de la masa (delta(33) S, delta(34) S, delta(36) S) en sulfuro y sulfato de las rocas del Precámbrico.
- Modelado geoquímico para interpretar datos isotópicos en el contexto de las transformaciones atmosféricas y biológicas del azufre.
Principales resultados:
- Evidencia de un cambio importante en el ciclo del azufre entre hace 2090 y hace 2450 millones de años (Ma).
- Antes de 2450 Ma, las reacciones atmosféricas de la fase gaseosa influyeron significativamente en el ciclo del azufre.
- Se dedujeron bajas presiones parciales de oxígeno atmosférico, lo que limita la intemperie oxidativa y el ciclo de azufre microbiano.
Conclusiones:
- El ciclo del azufre del Precámbrico experimentó una transición fundamental, pasando del dominio de la reacción atmosférica a otros procesos.
- La química atmosférica temprana, no la actividad microbiana, controlaba principalmente la fraccionamiento de isótopos de azufre antes de 2450 Ma.
- La fraccionamiento atmosférico debe ser considerado al interpretar los isótopos de azufre para entender la vida microbiana temprana y la historia de la Tierra.
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