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La corteza continental temprana de la Tierra se formó a partir de magmas de arco húmedos y oxidantes
Rong-Feng Ge1, Simon A Wilde2, Wen-Bin Zhu3
1State Key Laboratory for Mineral Deposits Research, Institute of Continental Geodynamics, Frontiers Science Center for Critical Earth Material Cycling, School of Earth Sciences and Engineering, Nanjing University, Nanjing, People's Republic of China. gerongfeng@nju.edu.cn.
Nature
|September 27, 2023
Resumen
La corteza continental de la Tierra primitiva se formó a través de la subducción, evidenciada por magmas oxidantes y ricos en agua similares a los arcos modernos. Esto sugiere la tectónica de placas temprana y el comienzo de la subducción hace unos 4.000 millones de años.
Área de la Ciencia:
- Ciencias de la Tierra
- Petrología
- Tectónica
Sus antecedentes:
- La formación de la corteza continental temprana de la Tierra es una cuestión geológica fundamental.
- Comprender la formación temprana de la corteza es clave para los recursos y la evolución planetaria.
- Los modelos anteriores se debaten debido a los desafíos en el análisis de rocas metamórficas antiguas.
Objetivo del estudio:
- Determinar la fugacidad del oxígeno magmático (fO2) y el contenido de agua (H2O) de la corteza continental temprana.
- Para probar el papel de la subducción en la formación temprana de la corteza.
- Para investigar el momento del inicio de la subducción.
Principales métodos:
- Se utilizaron dos oxíbarómetros de circón para medir simultáneamente el contenido magmático de fO2 y H2O.
- Analizó los granitoides arcaicos, que dominan la corteza continental temprana.
- Propiedades magmáticas correlacionadas con las profundidades estimadas de formación de magma.
Principales resultados:
- Los magmas granitoides arqueos eran significativamente más oxidantes que los magmas derivados del manto ambiental.
- Estos magmas poseían altos contenidos magmáticos de H2O (6-10 por ciento en peso) y altas proporciones de H2O/Ce (> 1.000).
- El fO2 magmático, el contenido de H2O y las relaciones H2O/Ce se correlacionan positivamente con la profundidad de la formación de magma.
Conclusiones:
- Las características magmáticas observadas apoyan fuertemente un modelo impulsado por la subducción para la formación temprana de la corteza.
- Estos hallazgos son difíciles de conciliar con los modelos de no subducción.
- Un aumento en el contenido magmático de fO2 y H2O entre hace 4.0 y 3.6 mil millones de años sugiere el inicio de la subducción.
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