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Un polimorfo de SiO2 post-stishovita en el meteorito Shergotty: implicaciones para los eventos de impacto
T G Sharp1, A El Goresy, B Wopenka
1Department of Geology, Arizona State University, Tempe, AZ 85287, USA.
Science (New York, N.Y.)
|May 29, 1999
Resumen
El meteorito marciano Shergotty contiene una fase densa de SiO2, similar a la estructura post-stishovita del manto inferior de la Tierra. Este polimorfo de alta densidad puede servir como un indicador de las presiones de choque extremas en los cuerpos planetarios.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- La mineralogía es la Mineralogía.
- Ciencias planetarias Ciencias planetarias.
Sus antecedentes:
- Los meteoritos marcianos proporcionan información sobre la formación y evolución planetaria.
- Comprender las fases de alta presión de la sílice (SiO2) es crucial para los modelos interiores de la Tierra profunda y planetarios.
Objetivo del estudio:
- Para investigar la composición mineralógica del meteorito marciano Shergotty.
- Para identificar polimorfos de sílice de alta presión dentro de muestras extraterrestres.
- Evaluar el potencial de estos polimorfos como indicadores de eventos de choque.
Principales métodos:
- Se empleó microscopía electrónica de transmisión (TEM) para analizar la microestructura del meteorito Shergotty.
- Se utilizó la difracción de electrones para determinar la estructura cristalográfica de las fases identificadas.
Principales resultados:
- Se identificó en Shergotty. una fase de SiO2 ortorrómbico denso, estructuralmente análogo a la post-stishovita con una estructura alfa-PbO2, fue identificado en Shergotty.
- Esta fase representa un polimorfo de alta densidad de sílice.
- La presencia de este polimorfo en una acondrita conmocionada sugiere que se experimentaron presiones de choque extremas.
Conclusiones:
- El meteorito marciano Shergotty contiene un polimorfo de sílice de alta presión similar al esperado en el manto inferior de la Tierra.
- Las estructuras de SiO2 post-stishovita pueden utilizarse como indicadores confiables de presiones de choque extremas en meteoritos impactados y potencialmente en interiores planetarios.
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