Geología de Bahía Esperanza y zonas adyacentes, Lago O'Higgins, Región de Aysén, Chile (~48.4° Lat. S.)
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Archivos
Fecha
2023
Autores
Gutiérrez-Órdenes, Joan Matías
Facultad/escuela
Idioma
es
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Editor
Universidad Andrés Bello
Nombre de Curso
Licencia CC
Licencia CC
Resumen
El Complejo Metamórfico Andino Oriental (CMAO), situado en los Andes Patagónicos, se
caracteriza por su metamorfismo de bajo grado y su polimorfismo en sus cuatro etapas de
deformación estudiadas. No obstante, persisten debates con relación al ambiente de depositación
inicial y ambiente tectónico en el cual sufrió la deformación, ya que las características de presión
y temperatura y proveniencia de los sedimentos aún no han permitido deducir su evolución de
manera concluyente.
Bahía Esperanza, ubicada en una de las zonas más remotas del Lago O´Higgins, cuenta con
escasos estudios directos sobre su geología, lo cual ha brindado solo indicios preliminares de la
composición geológica del área, lo cual de forma generalizada se asigna que esta zona pertenece
al CMAO. Por lo tanto, ante la falta de información detallada en esta región, surge la interrogante
de que si las rocas de Bahía Esperanza presentan similitudes en su composición, grado
metamórfico y estructuras en comparación con el CMAO descrito en otras localidades. Siendo lo
anterior el propósito final de este estudio, aportando nueva información detallada para la zona,
contribuyendo a la geología regional del Lago O’Higgins.
Considerando los antecedentes expuestos, en este trabajo se utilizaron datos petrológicos y
estructurales de trabajo de campo en la zona, para posteriormente ser caracterizados en base a
toda la información recolectada y comparándola con otros autores. Además, dentro del CMAO se
presentan diversos registros que caracterizan a este complejo como una zona con intenso
vetilleo, especialmente de cuarzo. Esto también se aplica a las rocas expuestas de Bahía
Esperanza, donde existen diversas configuraciones de vetas, siendo sus composiciones también
altamente ricas en sílice. En este estudio son divididas en tres tipos de asociaciones de vetas. La
primera familia (V1), corresponden a rectas erráticas, alojadas principalmente en unidades de
metaareniscas cuarcíferas. En segundo lugar, se encuentra el grupo de vetas syn-tectónicas (V2),
definidas así por su estrecha relación genética con los eventos deformativos ocurridos en el
CMAO debido a que su geometría sinuosa, es correlacionable con la de las foliaciones presente,
particularmente la foliación principal (S2). La última asociación de vetillas descrita es la de rectas
paralelas (V3) atisbando un proceso posterior al tectónico, que pueden ser producto de los
intrusivos posteriores que intruyen al basamento Paleozoico, siendo algunos con alto contenido
de sílice (Hipabisales Riodacíticos).
El trabajo de campo ha permitido dilucidar que la geología del CMAO en Bahía Esperanza y
alrededores coincide con la descrita por diversos autores en otras áreas del complejo, siendo
divididas en dos unidades principales en alternancia, metapelitas y metaareniscas cuarcíferas,
además de nueva información de unidades levantadas en este trabajo. Estas unidades muestran
un desarrollo tectónico estructural similar durante los cuatro eventos de deformación consecutivos
observados en terreno, siendo el principal un evento deformativo D2, dentro del cual se presenta
la foliación regional (S2), teniendo una orientación preferencial NE-SW
The Eastern Andean Metamorphic Complex (EAMC), located in the Patagonian Andes, is characterised by low-grade metamorphism and polymorphism in the four stages of deformation studied. However, debates persist regarding the initial depositional and tectonic environment in which it underwent deformation, as the pressure and temperature characteristics and sediment provenance have not yet allowed to conclusively deduce its evolution. Esperanza Bay, one of the most remote areas of Lake O'Higgins, has few direct studies on its geology, which has provided only preliminary indications of the geological composition of the area, which is generally assigned to the EAMC. Therefore, in the absence of detailed information in this region, the question arises as to whether the rocks of Esperanza Bay present similarities in composition, metamorphic grade, and structures in comparison with the EAMC described in other localities. This being the final purpose of this study, providing new detailed information, contributing to the regional geology of Lake O'Higgins. Considering the above, petrological, and structural data from field work in the area were used in this work, to be subsequently characterised based on all the information collected and compared with other authors. Furthermore, within the EAMC there are several records that locate this complex as an area with intense veining, especially of quartz. This also applies to the exposed rocks of Esperanza Bay, where there are several vein configurations, their compositions also being highly rich in silica. In this study they are divided into three types of vein associations. The first family (V1), corresponds to erratic straights, hosted mainly in quartz meta-sedimentary units. Secondly, there is a group of syn-tectonic veins (V2), so defined because of their close genetic relationship with the deformational events that occurred in the EAMC because their sinuous geometry is correlatable with that one of the foliations present, particularly the regional foliation (S2). The last association of vein described is parallel straight lines (V3), showing a post-tectonic process, which may be the product of later intrusives intruding the Paleozoic basement, some of which have a high silica content (Rhyodacitic subvolcanic magma). Field work has allowed us to elucidate that the geology of the EAMC in Esperanza Bay and surrounding areas coincides with that described by several authors in other areas of the complex, being divided into two main alternating units, metapelites and quartziferous meta-sandstones, in addition to new information from units collected in this work. These units show a similar structural tectonic development during the four consecutive deformation events observed in the field, the main one being a D2 deformation event, within which the regional foliation (S2) is present, having a preferential NE-SW orientation.
The Eastern Andean Metamorphic Complex (EAMC), located in the Patagonian Andes, is characterised by low-grade metamorphism and polymorphism in the four stages of deformation studied. However, debates persist regarding the initial depositional and tectonic environment in which it underwent deformation, as the pressure and temperature characteristics and sediment provenance have not yet allowed to conclusively deduce its evolution. Esperanza Bay, one of the most remote areas of Lake O'Higgins, has few direct studies on its geology, which has provided only preliminary indications of the geological composition of the area, which is generally assigned to the EAMC. Therefore, in the absence of detailed information in this region, the question arises as to whether the rocks of Esperanza Bay present similarities in composition, metamorphic grade, and structures in comparison with the EAMC described in other localities. This being the final purpose of this study, providing new detailed information, contributing to the regional geology of Lake O'Higgins. Considering the above, petrological, and structural data from field work in the area were used in this work, to be subsequently characterised based on all the information collected and compared with other authors. Furthermore, within the EAMC there are several records that locate this complex as an area with intense veining, especially of quartz. This also applies to the exposed rocks of Esperanza Bay, where there are several vein configurations, their compositions also being highly rich in silica. In this study they are divided into three types of vein associations. The first family (V1), corresponds to erratic straights, hosted mainly in quartz meta-sedimentary units. Secondly, there is a group of syn-tectonic veins (V2), so defined because of their close genetic relationship with the deformational events that occurred in the EAMC because their sinuous geometry is correlatable with that one of the foliations present, particularly the regional foliation (S2). The last association of vein described is parallel straight lines (V3), showing a post-tectonic process, which may be the product of later intrusives intruding the Paleozoic basement, some of which have a high silica content (Rhyodacitic subvolcanic magma). Field work has allowed us to elucidate that the geology of the EAMC in Esperanza Bay and surrounding areas coincides with that described by several authors in other areas of the complex, being divided into two main alternating units, metapelites and quartziferous meta-sandstones, in addition to new information from units collected in this work. These units show a similar structural tectonic development during the four consecutive deformation events observed in the field, the main one being a D2 deformation event, within which the regional foliation (S2) is present, having a preferential NE-SW orientation.
Notas
Memoria (Geólogo)
Financiamiento: Dir. Enrique Zamora M. Instituto Chileno de Campos de Hielo (ICCH), Subprograma Ciencia Joven 2022. Dr. Manuel Suárez Dittus Proyecto FIC Aysén BIP 40000501-0
Financiamiento: Dir. Enrique Zamora M. Instituto Chileno de Campos de Hielo (ICCH), Subprograma Ciencia Joven 2022. Dr. Manuel Suárez Dittus Proyecto FIC Aysén BIP 40000501-0
Palabras clave
Geología, Chile, Región de Aysén