Estructura del complejo metamórfico Limón Verde, cordillera Domeyko, Norte Grande de Chile
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2022
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es
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Universidad Andrés Bello
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Resumen
Las rocas del Complejo Metamórfico Limón Verde (CMLV), ubicadas 10 km al suroeste de Calama, forman parte del basamento antiguo del Norte Grande de Chile, el cual tiene una historia evolutiva paleozoica compleja. El presente estudio pretende generar nuevos antecedentes petrográficos y estructurales en el CMLV para obtener un nuevo modelo evolutivo en el contexto de amalgamación de terrenos al margen occidental del Gondwana en tiempos paleozoicos. Para ello se realizará un mapeo a escala 1:5.000 junto con el análisis de cortes transparentes para establecer relaciones de deformación vs cristalización y el reconocimiento de aspectos geométricos de estructuras, para interpretar las vergencias de estructuras regionales, con el fin de plantear un nuevo modelo evolutivo para el CMLV durante la era paleozoica.
En la zona de estudio, las rocas del CMLV corresponden a filitas, esquistos verdes, esquistos micáceos, esquistos cuarzo micáceos y anfibolitas, clasificadas en zonas de predominancia litológica (zonas de esquistos, anfibolitas y filitas) y zonas de mezcla (zonas mixtas I y II).
El CMLV presenta 4 episodios de deformación. D1 está preservado en la zona de charnela de un pliegue en vaina de fase 2. D2 es el evento de deformación principal del CMLV, corresponde a una zona de cizalle milonítica dextral pre-pérmica, con desarrollo de un pliegue en vaina regional elongado en dirección NE/SW, vergente al NE que presenta un aumento del grado metamórfico y la deformación desde NW hacia SE. El evento D3 se reconoce en un clivaje de crenulación S3 asociado a un antiforme de eje NE/SW vergente al SE, relacionado al clímax deformacional del Paleozoico tardío. Finalmente, D4 es un evento de formación frágil provocado por efecto del sistema de falla Domeyko en el lugar.
Se plantea que la evolución del CMLV se relaciona con la colisión de la sub-placa de Atacama contra el margen occidental de Gondwana durante el Silúrico, en donde el CMLV representaría la sutura generada por la colisión.
The rocks of the Limón Verde Metamorphic Complex (LVMC), located 10 km southwest of Calama, form part of an ancient basement of the Norte Grande of Chile, which has a complex Paleozoic evolutionary history. The present study aims to generate new petrographic and structural antecedents in the LVMC to obtain a new evolutionary model in the context of terrane amalgamation on the western margin of Gondwana in paleozoic times. For this, a mapping will be carried out at a scale of 1:5,000 together with the analysis of thin section to establish relations of deformation vs. crystallization and the recognition of geometric aspects of structures, to interpret vergences of regional structures, in order to propose a new model. evolutionary for LVMC during the Paleozoic era. In the study area, the rocks of the LVMC correspond to phyllites, green schists, micaceous schists, quartz micaceous schists and amphibolites, classified in zones of lithological predominance (schist, amphibolite and phyllite zones) and mixing zones (mixed zones I and II). The LVCM presents 4 episodes of deformation. D1 is preserved in the hinge zone of a phase 2 sheath fold. D2 is the main deformation event of the VSMC, corresponding to a pre-Permian dextral mylonitic shear zone, with development of a regional elongated sheath fold in the direction NE/SW, vergent to the NE showing an increase in metamorphic grade and deformation from NW to SE. The D3 event is recognized in an S3 crenulation cleavage associated with an antiform with a NE/SW axis verging to the SE, related to the deformational climax of the late Paleozoic. Finally, D4 is a brittle formation event caused by the effect of the Domeyko fault system in place. It is suggested that the evolution of the LVMC is related to the collision of the Atacama sub-plate against the western margin of Gondwana during the Silurian, where the LVMC would represent the suture generated by the collision.
The rocks of the Limón Verde Metamorphic Complex (LVMC), located 10 km southwest of Calama, form part of an ancient basement of the Norte Grande of Chile, which has a complex Paleozoic evolutionary history. The present study aims to generate new petrographic and structural antecedents in the LVMC to obtain a new evolutionary model in the context of terrane amalgamation on the western margin of Gondwana in paleozoic times. For this, a mapping will be carried out at a scale of 1:5,000 together with the analysis of thin section to establish relations of deformation vs. crystallization and the recognition of geometric aspects of structures, to interpret vergences of regional structures, in order to propose a new model. evolutionary for LVMC during the Paleozoic era. In the study area, the rocks of the LVMC correspond to phyllites, green schists, micaceous schists, quartz micaceous schists and amphibolites, classified in zones of lithological predominance (schist, amphibolite and phyllite zones) and mixing zones (mixed zones I and II). The LVCM presents 4 episodes of deformation. D1 is preserved in the hinge zone of a phase 2 sheath fold. D2 is the main deformation event of the VSMC, corresponding to a pre-Permian dextral mylonitic shear zone, with development of a regional elongated sheath fold in the direction NE/SW, vergent to the NE showing an increase in metamorphic grade and deformation from NW to SE. The D3 event is recognized in an S3 crenulation cleavage associated with an antiform with a NE/SW axis verging to the SE, related to the deformational climax of the late Paleozoic. Finally, D4 is a brittle formation event caused by the effect of the Domeyko fault system in place. It is suggested that the evolution of the LVMC is related to the collision of the Atacama sub-plate against the western margin of Gondwana during the Silurian, where the LVMC would represent the suture generated by the collision.
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Tesis (Geólogo)
Palabras clave
Norte grande de Chile, Mapeos regionales, Rocas metamórficas, Estructrura y evolución geológica, Amalgamación de terrenos