Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina

The upper Jurassic El Quemado Complex was sampled at 36 sites from five localities in the cordilleran foothills of southern Patagonia between Lago Argentino and Lago Posadas-Sierra Colorada, and the middle Jurassic Marifil Formation at 12 sites in the Somuncurá Massif near Camarones. The main lithol...

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Detalles Bibliográficos
Publicado: 2003
Materias:
Jurassic
Palaeomagnetism
Patagonia
Volcanic structure
igneous province
paleomagnetism
polar wandering
remanent magnetization
volcanism
Argentina
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0956540X_v154_n3_p599_IglesiaLlanos
http://hdl.handle.net/20.500.12110/paper_0956540X_v154_n3_p599_IglesiaLlanos
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_0956540X_v154_n3_p599_IglesiaLlanos2023-06-08T15:56:10Z Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina Jurassic Palaeomagnetism Patagonia Volcanic structure igneous province Jurassic paleomagnetism polar wandering remanent magnetization volcanism Argentina The upper Jurassic El Quemado Complex was sampled at 36 sites from five localities in the cordilleran foothills of southern Patagonia between Lago Argentino and Lago Posadas-Sierra Colorada, and the middle Jurassic Marifil Formation at 12 sites in the Somuncurá Massif near Camarones. The main lithology was ignimbrite, with minor tuff and lava. Petrographical and SEM observation show that the El Quemado rocks suffered an intense, high-temperature alteration which resulted in transformation of most primary Ti-magnetite in pseudobrookite, rutile and minor Ti-haematite and Fe hydrated oxides. A similar, less pronounced alteration occurred in the Marifil rocks. 40Ar/39Ar dating of El Quemado was possible for one sample from Sierra Colorada and yielded an age of 156.5 ± 1.9 Ma. Magnetic mineralogy measurements (isothermal remanence, hysteresis loop, Curie balance) show that the remanent magnetization is dominated by PSD low-Ti magnetite, often associated to a minor high-coercive mineral (haematite). Secondary magnetization components are usually absent or weak at El Quemado sites, strong at Marifil. They were completely erased by thermal and AF demagnetization and a characteristic remanence (ChRM) stable up to temperatures higher than 550°C or peak-field values of 100 mT was successfully isolated. The virtual geomagnetic pole (VGP) from the Marifil Formation (83°S, 138°E) is in agreement with the literature data for Jurassic rocks from stable South America. The El Quemado VGPs fall in two groups. The localities to the north of latitude 48°S (Lago Posadas, Sierra Colorada) yield a VGP (81°S, 172°E) close to that of Marifil, whereas those south of latitude 49°S (Lago San Martin, Lago Argentino) show a highly elongated VGP distribution consistent with counter-clockwise block-rotation about vertical axes. These rotations were likely caused by thrust sheets which were rotating counter-clockwise at the same time they were advancing towards the foreland. The amount of rotation varies according to the location of the sampling sites in the thrust and fold belt. 2003 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0956540X_v154_n3_p599_IglesiaLlanos http://hdl.handle.net/20.500.12110/paper_0956540X_v154_n3_p599_IglesiaLlanos
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Jurassic
Palaeomagnetism
Patagonia
Volcanic structure
igneous province
Jurassic
paleomagnetism
polar wandering
remanent magnetization
volcanism
Argentina
spellingShingle Jurassic
Palaeomagnetism
Patagonia
Volcanic structure
igneous province
Jurassic
paleomagnetism
polar wandering
remanent magnetization
volcanism
Argentina
Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina
topic_facet Jurassic
Palaeomagnetism
Patagonia
Volcanic structure
igneous province
Jurassic
paleomagnetism
polar wandering
remanent magnetization
volcanism
Argentina
description The upper Jurassic El Quemado Complex was sampled at 36 sites from five localities in the cordilleran foothills of southern Patagonia between Lago Argentino and Lago Posadas-Sierra Colorada, and the middle Jurassic Marifil Formation at 12 sites in the Somuncurá Massif near Camarones. The main lithology was ignimbrite, with minor tuff and lava. Petrographical and SEM observation show that the El Quemado rocks suffered an intense, high-temperature alteration which resulted in transformation of most primary Ti-magnetite in pseudobrookite, rutile and minor Ti-haematite and Fe hydrated oxides. A similar, less pronounced alteration occurred in the Marifil rocks. 40Ar/39Ar dating of El Quemado was possible for one sample from Sierra Colorada and yielded an age of 156.5 ± 1.9 Ma. Magnetic mineralogy measurements (isothermal remanence, hysteresis loop, Curie balance) show that the remanent magnetization is dominated by PSD low-Ti magnetite, often associated to a minor high-coercive mineral (haematite). Secondary magnetization components are usually absent or weak at El Quemado sites, strong at Marifil. They were completely erased by thermal and AF demagnetization and a characteristic remanence (ChRM) stable up to temperatures higher than 550°C or peak-field values of 100 mT was successfully isolated. The virtual geomagnetic pole (VGP) from the Marifil Formation (83°S, 138°E) is in agreement with the literature data for Jurassic rocks from stable South America. The El Quemado VGPs fall in two groups. The localities to the north of latitude 48°S (Lago Posadas, Sierra Colorada) yield a VGP (81°S, 172°E) close to that of Marifil, whereas those south of latitude 49°S (Lago San Martin, Lago Argentino) show a highly elongated VGP distribution consistent with counter-clockwise block-rotation about vertical axes. These rotations were likely caused by thrust sheets which were rotating counter-clockwise at the same time they were advancing towards the foreland. The amount of rotation varies according to the location of the sampling sites in the thrust and fold belt.
title Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina
title_short Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina
title_full Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina
title_fullStr Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina
title_full_unstemmed Palaeomagnetic study of the E1 Quemado complex and Marifil formation, Patagonian Jurassic igneous province, Argentina
title_sort palaeomagnetic study of the e1 quemado complex and marifil formation, patagonian jurassic igneous province, argentina
publishDate 2003
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0956540X_v154_n3_p599_IglesiaLlanos
http://hdl.handle.net/20.500.12110/paper_0956540X_v154_n3_p599_IglesiaLlanos
_version_ 1768544511422627840

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