Uso de edades U-Pb de circones detríticos de rocas paleozoicas para evaluar la existencia de Chaitenia
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2019
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es
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Universidad Andrés Bello
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Resumen
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.
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.
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.
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Tesis (Geólogo)
Palabras clave
Geología, Investigaciones