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Universidad Andrés Bello Facultad De Ingeniería Carrera De Geología Uso Universidad Andrés Bello Facultad de Ingeniería Carrera de Geología Uso de edades U-Pb de circones detríticos de rocas Paleozoicas para evaluar la existencia de Chaitenia Memoria para optar al Título de Geólogo Damián Ignacio Donoso Tapia Profesor guía: Francisco Enrique Hervé Allamand Miembros de la comisión: Mauricio Calderón Nettle Reynaldo Charrier González Santiago de Chile 2019 RESUMEN DE LA MEMORIA PARA OPTAR AL TÍTULO DE: Geólogo Por: Damián Ignacio Donoso Tapia Fecha: 25 de Noviembre de 2019 PROFESOR GUÍA: Francisco Enrique Hervé Allamand USO DE EDADES U-PB DE CIRCONES DETRÍTICOS DE ROCAS PALEOZOICAS PARA EVALUAR LA EXISTENCIA DE CHAITENIA Se analizan edades SHRIMP U-Pb de circones detríticos de rocas Paleozoicas de complejos acrecionarios distribuidos a lo largo y ancho de Chile y agrupados en siete segmentos, entre los ~27° y 55°S, con el fin de reconocer, caracterizar y comparar los espectros de edades con los asignados a Chaitenia, además de establecer los potenciales límites geográficos de este terreno. Los segmentos de complejos acrecionarios son: Norte Chico (dividido en tres subgrupos), Zona Central (Serie Oriental y Serie Occidental), Chaitenia, Complejo Metamórfico Chonos, Complejo Duque de York, Complejo Metamórfico Andino Oriental y Complejo Metamórfico Cordillera Darwin. A partir de 4051 edades U-Pb de circones detríticos de 67 muestras, los resultados muestran tres subgrupos que habrían tenido una evolución geotectónica similar siguiendo ambientes tectónicos de subducción, colisión y uno intermedio entre subducción y colisión. La parte sur de la Serie Occidental, que empieza al sur del lineamiento de Lanalhue (~38°30’S) tiene una proporción de circones Devónicos y signatura detrítica similares a las de Chaitenia, tomando como signatura tipo una muestra con contenido fósil de trilobites. Esta signatura se extiende hasta los ~44°S, por lo que estos serían los límites norte y sur de este terreno. Se propone que el lineamiento de Lanalhue corresponde a la zona de sutura entre Chaitenia y Chilenia, y que las rocas metamórficas que afloran hacia el sur, serían parte del prisma de acreción generado por la subducción en la parte occidental de Chaitenia. Los circones precámbricos de todos los segmentos (incluyendo subgrupos) indican una evolución geotectónica similar de las fuentes durante el Proterozoico. Además, existe una signatura precámbrica común, con un gap entre los ca. 650 y ca. 1000 Ma, y peaks a los ca. 550-600 Ma y ca. 1050-1100 Ma. Esta signatura también se encuentra en rocas de las Tasmanidas en el este de Australia y Nueva Caledonia, por lo que se infiere una posible correlación temporal entre los basamentos. USE OF U-PB AGES OF DETRITAL ZIRCONS FROM PALEOZOIC ROCKS TO EVALUATE THE EXISTANCE OF CHAITENIA SHRIMP U-Pb detrital zircon ages of late Paleozoic accretionary complexes along the coastline of Chile between ~27° and 55°S are analyzed in order to recognize, distinguish and compare their age spectra with those assigned to Chaitenia, with the purpose of establishing the possible geographic boundaries of this exotic terrane. Said accretionary complexes have been grouped into seven segments, from north to south: Norte Chico (Subdivided into three groups), Zona Central (Eastern Series and Western Series), Chaitenia, Chonos Metamorphic Complex, Duque de York Complex, Eastern Andes Metamorphic Complex and Cordillera Darwin Metamorphic Complex. From 4051 U-Pb detrital zircon ages of 67 samples, the results show that the segments can be divided into three subgroups that may have had a similar geotectonic evolution through different tectonic settings: subduction, collision and an intermediate setting between subduction and collision. The southern part of the Western Series, which starts south of the Lanalhue lineament (~38°30’S) has a proportion of Devonian zircons and a detrital fingerprint similar to that of Chaitenia, based on a sample with trilobite fossil content. This detrital fingerprint extends until ~44°S, which may indicate the northern and southern boundaries of this exotic terrane. It is proposed that the Lanalhue lineament may indicate the suture between the Chaitenia and Chilenia terranes, and that the metamorphic rocks that outcrop in this area, possibly represent the accretionary prism formed by the subduction on the western side of Chaitenia, after its collision with the continental margin of the Gondwana supercontinent. Precambrian zircons of all segments (including subgroups) indicate a similar geotectonic evolution of their sources during Proterozoic times. It is also reported that the Precambrian detrital fingerprint is almost identical for all segments, with a gap between ca. 650 and ca. 1000 Ma, and peaks at ca. 550-600 Ma and ca. 1050-1100 Ma. This Precambrian detrital fingerprint can be also found in the Tasmanides in eastern Australia and New Caledonia, which allows inferring a possible synchronism between the Precambrian basement rocks of Chile and part of Oceania. Agradecimientos Primero, agradezco al profesor Francisco Hervé por darme la oportunidad de trabajar bajo su tutela con un tema tan interesante que tiene un tremendo potencial. Al profesor Reynaldo Charrier, por ser una gran fuente de motivación, al profesor Mauricio Calderón por su apoyo tanto dentro como fuera de la sala de clases, y finalmente, al profesor Francisco Fuentes, por despertar mi interés en la geoquímica y la petrología a través de los proyectos que me proponía para que trabajáramos, incluyendo el de mi memoria. A mis amigos, quienes me han apoyado cuando estaba pasando por los momentos más duros y también en los momentos más alegres, Daniel, Zárate, Filete, Joaquín, Queque, Diego. Y de paso a todas aquellas amistades a distancia que han sido tremendamente importantes, Tim, Bradley, Jacob, Chris, Nicolás. Todos ustedes me han ayudado a dejar atrás mis miedos e inseguridades. A la gente de los Laboratorios, a Flor y Jean Baptiste, por ser quienes me recibieron con brazos abiertos y me apoyaron desde que llegué a la Universidad y lo siguen haciendo hasta el día de hoy, me hicieron sentir como en casa desde el día 1. Agradezco a mi familia por estar presente en cada paso que he dado y su apoyo incondicional, no ha sido un camino fácil de recorrer, pero han sido una inspiración para no bajar los brazos y seguir adelante, siempre con la cabeza arriba. Tabla de contenidos 1. Introducción .......................................................................................................................... 1 1.1. Formulación del estudio ................................................................................................. 1 1.2. Hipótesis de trabajo ........................................................................................................ 5 1.3. Objetivos ........................................................................................................................ 5 1.3.1. Objetivo General ...................................................................................................... 5 1.3.2. Objetivos específicos ............................................................................................... 5 1.4. Metodología ................................................................................................................... 6 1.4.1. Trabajo de recopilación de bibliografía .................................................................... 6 1.4.2. Trabajo de análisis estadístico y comparativo ......................................................... 6 1.5. Ubicación de la zona de estudio .................................................................................... 8 2. Marco Geológico ................................................................................................................. 10 2.1. Marco Geotectónico – Ciclo Gondwánico .................................................................... 10 2.1.1. Acreción de terrenos ................................................................................................. 10 2.1.2. Evolución geológica en territorio chileno ................................................................... 11 2.2. Unidades Morfoestructurales ....................................................................................... 12 2.3. Geología Local ............................................................................................................. 14 2.3.1. Rocas metamórficas .................................................................................................. 15 2.3.1.1. Complejos acrecionarios del Paleozoico tardío del norte de Chile (26 – 34°S) (Carbonífero – Triásico?) ................................................................................................. 15 2.3.1.2. Serie Oriental (Carbonífero - Mississippiense) ................................................... 16 2.3.1.3. Serie Occidental (Carbonífero – Mississippiense/Pennsylvaniense?) ................ 16 2.3.1.4. Complejo Metamórfico Bahía Mansa (CMBM) (Carbonífero – Triásico?) ........... 16 2.3.1.5. Complejo Colohuincul (Mesoproterozoico?) ....................................................... 17 2.3.1.6. Complejo Metamórfico Chonos (Triásico Superior?) .......................................... 18 2.3.1.7. Complejo Duque de York (Carbonífero – Pérmico Temprano?) ......................... 18 2.3.1.8. Complejo Metamórfico Andino Oriental (Devónico Tardío – Carbonífero?) ........ 19 2.3.1.9. Complejo Metamórfico Cordillera Darwin (Devónico Tardío – Carbonífero?) ..... 19 2.3.2. 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