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Stishovite en el límite cretáceo-terciario, ratón, Nuevo México
Science (New York, N.Y.)
|March 3, 1989
Resumen
La stishovita, una fase de sílice densa, indica impactos terrestres. Los investigadores confirmaron su presencia en muestras del límite Cretácico-Terciario utilizando RMN y difracción de rayos X de silicio-29 MAS, distinguiéndolo de la sílice volcánica.
Área de la Ciencia:
- Geología Geología Geología.
- La mineralogía es la Mineralogía.
- La geoquímica es la geoquímica.
Sus antecedentes:
- La stishovita, un polimorfo de sílice de alta presión, es un indicador clave de los eventos de impacto terrestre.
- Aunque se encuentra en los sitios de impacto, la stishovita no se ha identificado en lugares volcánicos.
- Comprender la ocurrencia de la stishovita ayuda a distinguir el impacto de los registros geológicos volcánicos.
Objetivo del estudio:
- Para investigar la presencia y la naturaleza de la stishovita en muestras de la capa límite Cretácico-Terciario.
- Para confirmar la stishovita como un marcador de eventos de impacto en el sitio de Raton, Nuevo México.
- Para caracterizar la stishovita utilizando técnicas analíticas avanzadas.
Principales métodos:
- Espectroscopia de resonancia magnética nuclear giratoria de ángulo mágico de silicio-29 en estado sólido (Si-29 MAS NMR).
- Análisis por difracción de rayos X (XRD). análisis.
- Tratamiento térmico de muestras para identificar la estabilidad de la stishovita.
Principales resultados:
- La RMN Si-29 MAS reveló una resonancia característica a -191,3 ppm, lo que es indicativo de silicio octaédrico, confirmando la estishovita cristalina.
- Esta resonancia desapareció al calentarla a 850°C, en consonancia con la conocida transición de fase de la stishovita.
- El análisis XRD de los residuos de ácido fluorhídrico mostró numerosos picos, incluidos ocho característicos de la stishovita, junto con minerales comunes como el cuarzo y el circón.
Conclusiones:
- La stishovita está presente en granos minerales cristalinos dentro de la capa límite entre el Cretácico y el Terciario en Raton, Nuevo México.
- Los hallazgos apoyan el papel de la stishovita como un indicador confiable de los eventos de impacto terrestre.
- La combinación de RMN y XRD proporciona pruebas sólidas para la identificación de la stishovita.
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