Variaciones composicionales del magmatismo andino oligoceno-mioceno a lo largo del frente cordillerano en Chile central (33°-36°S) y sus implicancias tectónicas
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2019
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es
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Universidad Andrés Bello
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A lo largo del Frente Cordillerano de Chile Central afloran las formaciones Abanico y Colbún, las cuales han sido consideradas como parte del relleno de la Cuenca de Abanico, principalmente en el Oligoceno, y cuya extensión abarcaría la región de la Cordillera Principal comprendida entre 28° y39°S. Este estudio corresponde a un análisis de la información geoquímica disponible sobre una base recopilada, de tres localidades de la porción Occidental de la Cordillera Principal donde afloran estas formaciones: (i) el área del Cerro Abanico,a ~33° S, (ii) sector entre los valles de los ríos Tinguiririca y Lontué,a 34°45’-35°10’S, y(iii) el área de Colbún, a 35°35’-36°S. Además de esta distinción por sector, los datos fueron analizados considerando cuatro periodos: G1 (36 a 25 Ma), G2 (25 a 22 Ma), G3 (22 a 18 Ma) y G4 (18 a 15 Ma). A través del análisis de la información geoquímica y petrológica, se infieren en este trabajo variaciones en la evolución contemporánea de las tres regiones. La confección de distintos diagramas de elementos mayores y trazas ha permitido detectar variaciones en el tiempo en cada uno de estos sectores. Se presenta evidencia que coincide con estudios anteriores, los cuales indican que,en las regiones norte y centro de este estudio, se produjo un engrosamiento cortical progresivo que favoreció un ambiente magmático a mayor profundidad y a condiciones de mayor presión. Además, procesos como contaminación por fluidos y fundidos proveniente de la losa de subducción, que no se produce en el sector sur con la misma magnitud. De esta forma, en base a las características geoquímicas y petrogenéticas que dieron origen a las Unidades Inferior y Superior de la Formación Colbún, las cuales habían sido correlacionadas con las formaciones Abanico y Farellones, respectivamente, se concluye que la Formación Colbún no comparte los mismos procesos, ni comparte un origen común con las rocas ubicadas al norte de este sector.
Along the Andean Front or western flank of the Principal Cordillera in central Chile the Abanico and Colbún formations are exposed, All these formations are considered to correspond to the Abanico basin fill, mostly in Oligocene time, which extended from 28° to 39°S. S. The current study is a geochemical analysis of a compiled information from three areas of the western portion of the Principal Cordillera: (i) Cerro Abanico, at ~33° S, (ii) between the valleys of the Tinguiririca and Lontué rivers, at 34°45’- 35°10’S, and (iii) Colbún, at 35°35’-36°S. Additionally, the geochemical information has been analyzed according to four different periods: G1 (36 to 25 Ma), G2 (25 to 22 Ma), G3 (22 to 18 Ma) and G4 (18 to 15 Ma); which, besides the recognition by sector, facilitates the detection of variations through time for the different diagrams of major elements and traces. Evidence is presented that coincides with previous studies, which indicate that in the northern and central regions of this study, there was a progressive cortical thickening that favored a magmatic environment at greater depth and at higher pressure conditions. In addition, processes such as contamination by fluids and melts from the subduction slab, which does not occur in the southern sector at the same magnitude. Based on the geochemical and petrogenetic characteristics that originated the Lower and Upper units of the Colbún Formation, which had been correlated with the Abanico and Farellones formations respectively, it is concluded that the Colbún formation does not share the same processes, nor does it share a common origin with the rocks located north of this sector.
Along the Andean Front or western flank of the Principal Cordillera in central Chile the Abanico and Colbún formations are exposed, All these formations are considered to correspond to the Abanico basin fill, mostly in Oligocene time, which extended from 28° to 39°S. S. The current study is a geochemical analysis of a compiled information from three areas of the western portion of the Principal Cordillera: (i) Cerro Abanico, at ~33° S, (ii) between the valleys of the Tinguiririca and Lontué rivers, at 34°45’- 35°10’S, and (iii) Colbún, at 35°35’-36°S. Additionally, the geochemical information has been analyzed according to four different periods: G1 (36 to 25 Ma), G2 (25 to 22 Ma), G3 (22 to 18 Ma) and G4 (18 to 15 Ma); which, besides the recognition by sector, facilitates the detection of variations through time for the different diagrams of major elements and traces. Evidence is presented that coincides with previous studies, which indicate that in the northern and central regions of this study, there was a progressive cortical thickening that favored a magmatic environment at greater depth and at higher pressure conditions. In addition, processes such as contamination by fluids and melts from the subduction slab, which does not occur in the southern sector at the same magnitude. Based on the geochemical and petrogenetic characteristics that originated the Lower and Upper units of the Colbún Formation, which had been correlated with the Abanico and Farellones formations respectively, it is concluded that the Colbún formation does not share the same processes, nor does it share a common origin with the rocks located north of this sector.
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Tesis (Geólogo)
Palabras clave
Magmatismo, Rocas Magmáticas, Tectónica de Placas