Geoquímica y petrogénesis del volcanismo triásico superior aflorante ubicado entre los 34° Y 37°S, Chile
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Fecha
2023
Autores
Facultad/escuela
Idioma
es
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Universidad Andrés Bello
Nombre de Curso
Licencia CC
Licencia CC
Resumen
La evolución tectonomagmática del borde suroccidental de Godwana durante el
Ciclo Pre-Andino ha sido objeto de múltiples estudios sin tener certeza aún de las
condiciones que lo gobernaron. En Chile, entre los 34° y 37° se han reconocido 3 unidades
Triásicas en depocentros marino-continentales que contienen una serie de lavas de
carácter subalcalino: Crucero los Sauces (cuenca Vichuquen-curepto-Hualañe), Estratos
de Pocillas (cuenca de Pocillas) y miembro Santa Juana (formación Santa Juana). Los
datos geoquímicos muestran que Formación Crucero los Sauces y Estratos de Pocillas
exhiben típicas firmas de ambientes de arco mientras que Santa Juana exhibe firmas afines
a la presencia de un slab break-off. La diferencia entre las signaturas de estas unidades, la
ausencia de un arco documentado para el ciclo pre-Andino y el alto contenido de sílice en
las rocas de formación Crucero los Sauces y estratos de Pocillas pone en duda la existencia
de subducción a estas latitudes durante el Mezosoico. Los resultados obtenidos sugieren
que los magmas que dieron origen a las rocas de estas tres formaciones se formaron en
condiciones similares, con diferentes grados de contaminación cortical durante su ascenso,
que incluye, en el caso de Estratos de Pocillas y Crucero los Sauces, contaminación con
corteza Paleozoica con firmas de subducción. Este proceso les habría heredado las firmas
de arco documentadas. Por su parte, el magma que dio origen a las rocas de formación
Santa Juana no se habría contaminado con esta corteza durante su ascenso conservado
su signatura original de un ambiente slab break off. Esto sugiere que las cuencas formadas
en el periodo pre-Andino fueron depocentros aislados y no continuos como se creía
anteriormente y que existió una segmentación N-S a lo largo del margen durante el
Mesozoico.
The tectonomagmatic evolution of the southwestern edge of Godwana during the Pre-Andean Cycle has been the subject of multiple studies without being certain of the conditions that governed it. In Chile, between 34° and 37°, three Triassic units have been recognized in marine-continental depocenters containing a series of subalkaline lavas: Crucero los Sauces (Vichuquen-curepto-Hualañe basin), Estratos de Pocillas (Pocillas basin), and Santa Juana member (Santa Juana formation). The geochemical data show that the Crucero los Sauces Formation and Pocillas Strata exhibit typical signatures of arc environments, while Santa Juana exhibits signatures related to the presence of a slab breakoff. The difference between the signatures of these units, the absence of a documented arc for the pre-Andean cycle, and the high silica content in the rocks of the Crucero los Sauces formation and the Pocillas strata cast doubt on the existence of subduction at these latitudes during the Mesozoic. The results obtained suggest that the magmas that gave rise to the rocks of these three formations were formed under similar conditions, with different degrees of cortical contamination during their ascent, including, in the case of Estratos de Pocillas and Crucero los Sauces, contamination with Paleozoic crust with subduction signatures. This process would have inherited the documented arc signatures. For its part, the magma that gave rise to the Santa Juana formation rocks would not have been contaminated with this crust during its ascent, preserving its signature of a slab break off environment. This suggests that the basins formed in the pre-Andean period were isolated and not continuous depocenters, as previously believed, and that there was a N-S segmentation along the margin during the Mesozoic.
The tectonomagmatic evolution of the southwestern edge of Godwana during the Pre-Andean Cycle has been the subject of multiple studies without being certain of the conditions that governed it. In Chile, between 34° and 37°, three Triassic units have been recognized in marine-continental depocenters containing a series of subalkaline lavas: Crucero los Sauces (Vichuquen-curepto-Hualañe basin), Estratos de Pocillas (Pocillas basin), and Santa Juana member (Santa Juana formation). The geochemical data show that the Crucero los Sauces Formation and Pocillas Strata exhibit typical signatures of arc environments, while Santa Juana exhibits signatures related to the presence of a slab breakoff. The difference between the signatures of these units, the absence of a documented arc for the pre-Andean cycle, and the high silica content in the rocks of the Crucero los Sauces formation and the Pocillas strata cast doubt on the existence of subduction at these latitudes during the Mesozoic. The results obtained suggest that the magmas that gave rise to the rocks of these three formations were formed under similar conditions, with different degrees of cortical contamination during their ascent, including, in the case of Estratos de Pocillas and Crucero los Sauces, contamination with Paleozoic crust with subduction signatures. This process would have inherited the documented arc signatures. For its part, the magma that gave rise to the Santa Juana formation rocks would not have been contaminated with this crust during its ascent, preserving its signature of a slab break off environment. This suggests that the basins formed in the pre-Andean period were isolated and not continuous depocenters, as previously believed, and that there was a N-S segmentation along the margin during the Mesozoic.
Notas
Memoria (Geóloga)
Palabras clave
Geoquímica, Petrogénesis, Vulcanismo