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Pruebas isotópicas de titanio para la corteza felsica y la tectónica de placas hace 3.500 millones de años

Nicolas D Greber¹, Nicolas Dauphas², Andrey Bekker^3,4

¹Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60615, USA. nicolas.greber@unige.ch.

Science (New York, N.Y.)

|September 23, 2017

Resumen

La tectónica de placas comenzó temprano en la historia de la Tierra, hace unos 3.500 millones de años, evidenciado por la composición uniforme de esquisto. Esta actividad temprana influyó en el suministro de nutrientes y los niveles de oxígeno.

Área de la Ciencia:

Geoquímica
Tectónica de placas
La historia temprana de la Tierra

Sus antecedentes:

La corteza terrestre muestra diferencias claras entre los continentes y los fondos oceánicos.
Comprender el origen de esta dicotomía es clave para la datación de la tectónica de placas y los cambios en el suministro de nutrientes.
El límite Arcaico-Proterozoico marca una transición significativa en la historia de la Tierra.

Objetivo del estudio:

Para determinar cuándo comenzó la dicotomía de composición entre los continentes y los océanos.
Para investigar el papel de la tectónica de placas temprana en la formación de la corteza terrestre.
Comprender los cambios en el suministro de nutrientes a los océanos y los niveles de oxígeno atmosférico.

Principales métodos:

Análisis de la composición isotópica del titanio (Ti) en pizarras de diferentes edades.
El uso de isótopos de Ti para inferir la composición química de la corteza continental expuesta.
Examinar los cambios en la abundancia de nutrientes (fosforo, níquel) a través de la frontera entre el arcaico y el proterozoico.

Principales resultados:

Las pizarras mostraron consistentemente una composición isotópica uniforme de titanio en todas las edades estudiadas.
Esta uniformidad indica una corteza continental predominantemente felsica (rica en sílice) desde hace 3.500 millones de años.
Un cambio notable en la abundancia de fósforo y níquel ocurrió en el límite Arcaico-Proterozoico.

Conclusiones:

La evidencia sugiere que la tectónica de placas se inició hace unos 3.500 millones de años.
La formación temprana de la corteza felsica y el posterior desgaste influyeron en la entrada de nutrientes oceánicos.
Los cambios en la disponibilidad de nutrientes pueden haber contribuido al aumento del oxígeno atmosférico.

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