Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina

Middle Jurassic volcanism is a major magmatic event in the evolution of Patagonia. In the southwestern corner of the North Patagonian Massif at Sierra de Mamil Choique, basic to intermediate, ca. 170 Ma dykes are widespread. In this article, new chemical data from the dykes are presented, analyzed,...

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Autores principales: López De Luchi, M.G., Rapalini, A.E.
Formato: JOUR
Materias:
Dyke swarms
Middle Jurassic
Patagonia
Petrology of basic to intermediate volcanism
dike swarm
geochemistry
magmatism
petrology
tectonic setting
volcanism
Argentina
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_08959811_v15_n6_p625_LopezDeLuchi
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_08959811_v15_n6_p625_LopezDeLuchi2023-10-03T15:42:34Z Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina López De Luchi, M.G. Rapalini, A.E. Dyke swarms Middle Jurassic Patagonia Petrology of basic to intermediate volcanism dike swarm geochemistry magmatism petrology tectonic setting volcanism Argentina Middle Jurassic volcanism is a major magmatic event in the evolution of Patagonia. In the southwestern corner of the North Patagonian Massif at Sierra de Mamil Choique, basic to intermediate, ca. 170 Ma dykes are widespread. In this article, new chemical data from the dykes are presented, analyzed, and compared with regional information about Jurassic volcanism. The dyke swarms are composed of an alkaline and a subalkaline series. Fractionating phases that controlled the magmatic evolution were plagioclase (andesine) + clinopyroxene with clinoamphibole (for compositions of SiO2 > 60%) in the subalkaline series and clinoamphibole + plagioclase (oligoclase) ± magnetite in the alkaline series. The source of both series could be an enriched lithospheric mantle or lower crust. Although crustal contamination or enrichment by subduction-derived fluids cannot be demonstrated from the available data, a subduction-enrichment process of the magma source is suggested for the subalkaline rocks. Different volatile composition, water content and perhaps temperature at the melting site would control the higher Zr content of the alkaline series and would allow low melt fractions to leave their sources. Absolute values for Ba/Nb (60-160), La/Nb (4-5), and K/Nb (>2000) in both series indicate a significantly LIL-enriched crustal component. Nd/Th of approximately 4 for the alkaline rocks argues against a primitive mantle, supported by the low MgO, Cr, and Ni and high LILE contents. In contrast, Nd/Th between 15 and 27 in the subalkaline rocks is similar to a mantle source. Crustal components are indicated by the higher La/Yb and Na2O and lower CaO in the alkaline rocks. Regional, structural, and, to a certain extent, petrological evidence for the Middle Jurassic dyke swarms of the Sierra de Mamil Choique point to an extensional intracontinental tectonic setting in which older structures controlled the development of the volcanism. © 2002 Elsevier Science Ltd. All rights reserved. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_08959811_v15_n6_p625_LopezDeLuchi
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Dyke swarms
Middle Jurassic
Patagonia
Petrology of basic to intermediate volcanism
dike swarm
geochemistry
magmatism
petrology
tectonic setting
volcanism
Argentina
spellingShingle Dyke swarms
Middle Jurassic
Patagonia
Petrology of basic to intermediate volcanism
dike swarm
geochemistry
magmatism
petrology
tectonic setting
volcanism
Argentina
López De Luchi, M.G.
Rapalini, A.E.
Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina
topic_facet Dyke swarms
Middle Jurassic
Patagonia
Petrology of basic to intermediate volcanism
dike swarm
geochemistry
magmatism
petrology
tectonic setting
volcanism
Argentina
description Middle Jurassic volcanism is a major magmatic event in the evolution of Patagonia. In the southwestern corner of the North Patagonian Massif at Sierra de Mamil Choique, basic to intermediate, ca. 170 Ma dykes are widespread. In this article, new chemical data from the dykes are presented, analyzed, and compared with regional information about Jurassic volcanism. The dyke swarms are composed of an alkaline and a subalkaline series. Fractionating phases that controlled the magmatic evolution were plagioclase (andesine) + clinopyroxene with clinoamphibole (for compositions of SiO2 > 60%) in the subalkaline series and clinoamphibole + plagioclase (oligoclase) ± magnetite in the alkaline series. The source of both series could be an enriched lithospheric mantle or lower crust. Although crustal contamination or enrichment by subduction-derived fluids cannot be demonstrated from the available data, a subduction-enrichment process of the magma source is suggested for the subalkaline rocks. Different volatile composition, water content and perhaps temperature at the melting site would control the higher Zr content of the alkaline series and would allow low melt fractions to leave their sources. Absolute values for Ba/Nb (60-160), La/Nb (4-5), and K/Nb (>2000) in both series indicate a significantly LIL-enriched crustal component. Nd/Th of approximately 4 for the alkaline rocks argues against a primitive mantle, supported by the low MgO, Cr, and Ni and high LILE contents. In contrast, Nd/Th between 15 and 27 in the subalkaline rocks is similar to a mantle source. Crustal components are indicated by the higher La/Yb and Na2O and lower CaO in the alkaline rocks. Regional, structural, and, to a certain extent, petrological evidence for the Middle Jurassic dyke swarms of the Sierra de Mamil Choique point to an extensional intracontinental tectonic setting in which older structures controlled the development of the volcanism. © 2002 Elsevier Science Ltd. All rights reserved.
format JOUR
author López De Luchi, M.G.
Rapalini, A.E.
author_facet López De Luchi, M.G.
Rapalini, A.E.
author_sort López De Luchi, M.G.
title Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina
title_short Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina
title_full Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina
title_fullStr Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina
title_full_unstemmed Middle Jurassic dyke swarms in the North Patagonian Massif: The Lonco trapial formation in the Sierra de Mamil Choique, Río Negro province, Argentina
title_sort middle jurassic dyke swarms in the north patagonian massif: the lonco trapial formation in the sierra de mamil choique, río negro province, argentina
url http://hdl.handle.net/20.500.12110/paper_08959811_v15_n6_p625_LopezDeLuchi
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