Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes

The Ushuaia pluton (UP) and the Ushuaia Peninsula Andesites (UPA) are intrusive units of a Late Cretaceous rear-arc in the Southernmost Andes. We report new LA-ICP-MS zircon ages from ∼71 to 75 Ma for the UP, and of ∼84 Ma for the UPA, which allow to differentiate these two magmatic events; consiste...

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Autores principales: González Guillot, M., Ghiglione, M., Escayola, M., Martins Pimentel, M., Mortensen, J., Acevedo, R.
Formato: JOUR
Materias:
Fuegian Andes
Late Cretaceous
Magma diversification
Pluton growth
Regional tectonics
Cretaceous
emplacement
geochemistry
inductively coupled plasma method
magma
mass spectrometry
petrography
pluton
tectonic setting
zircon
Andes
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_08959811_v88_n_p497_GonzalezGuillot
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_08959811_v88_n_p497_GonzalezGuillot2023-10-03T15:43:41Z Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes González Guillot, M. Ghiglione, M. Escayola, M. Martins Pimentel, M. Mortensen, J. Acevedo, R. Fuegian Andes Late Cretaceous Magma diversification Pluton growth Regional tectonics Cretaceous emplacement geochemistry inductively coupled plasma method magma mass spectrometry petrography pluton tectonic setting zircon Andes The Ushuaia pluton (UP) and the Ushuaia Peninsula Andesites (UPA) are intrusive units of a Late Cretaceous rear-arc in the Southernmost Andes. We report new LA-ICP-MS zircon ages from ∼71 to 75 Ma for the UP, and of ∼84 Ma for the UPA, which allow to differentiate these two magmatic events; consistent with their distinct petrography and geochemistry. The UP is a composite, incrementally assembled pluton in upper crustal levels. Successive injections of magma batches define two main sections, each in turn constructed by several smaller pulses: an early ultramafic-mafic section consists mainly of hornblende pyroxenite, hornblendite and gabbro/diorite with reverse concentric zonation, and a later intermediate section built up mainly by monzodiorite. Mingling and layering between mafic and intermediate facies along the contact point to simultaneous emplacement at the end of one main pulse and the beginning of the other. Mineralogy and geochemistry suggest the rock sequence in the UP is cogenetic. In part it resulted by in-situ magmatic processes that included crystal-melt fractionation during injection of magma mushes, mingling, local melt segregation and mixing with crustal partial melts. The country rock is affected by penetrative ductile deformation and regional metamorphism developed during mid-Cretaceous Andean main orogenic phase. It also shows an overimposed pluton-margin parallel foliation and a post-kinematic contact metamorphic aureole. On the other hand, the UP has a concentric igneous foliation parallel to pluton margins interpreted as a primary magmatic feature. The above evidences, along with absence of subsolidus fabrics and metamorphism, indicate the pluton post-date peak regional metamorphism and ductile structures in the country rock. The new zircon ages constrain the top age of early Andean deformation, as well as the magmatic gap registered for the end of the Cretaceous, and confirm an emplacement during a recorded compressive regime that transmitted shortening to the foreland. © 2018 Elsevier Ltd JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_08959811_v88_n_p497_GonzalezGuillot
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Fuegian Andes
Late Cretaceous
Magma diversification
Pluton growth
Regional tectonics
Cretaceous
emplacement
geochemistry
inductively coupled plasma method
magma
mass spectrometry
petrography
pluton
tectonic setting
zircon
Andes
spellingShingle Fuegian Andes
Late Cretaceous
Magma diversification
Pluton growth
Regional tectonics
Cretaceous
emplacement
geochemistry
inductively coupled plasma method
magma
mass spectrometry
petrography
pluton
tectonic setting
zircon
Andes
González Guillot, M.
Ghiglione, M.
Escayola, M.
Martins Pimentel, M.
Mortensen, J.
Acevedo, R.
Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes
topic_facet Fuegian Andes
Late Cretaceous
Magma diversification
Pluton growth
Regional tectonics
Cretaceous
emplacement
geochemistry
inductively coupled plasma method
magma
mass spectrometry
petrography
pluton
tectonic setting
zircon
Andes
description The Ushuaia pluton (UP) and the Ushuaia Peninsula Andesites (UPA) are intrusive units of a Late Cretaceous rear-arc in the Southernmost Andes. We report new LA-ICP-MS zircon ages from ∼71 to 75 Ma for the UP, and of ∼84 Ma for the UPA, which allow to differentiate these two magmatic events; consistent with their distinct petrography and geochemistry. The UP is a composite, incrementally assembled pluton in upper crustal levels. Successive injections of magma batches define two main sections, each in turn constructed by several smaller pulses: an early ultramafic-mafic section consists mainly of hornblende pyroxenite, hornblendite and gabbro/diorite with reverse concentric zonation, and a later intermediate section built up mainly by monzodiorite. Mingling and layering between mafic and intermediate facies along the contact point to simultaneous emplacement at the end of one main pulse and the beginning of the other. Mineralogy and geochemistry suggest the rock sequence in the UP is cogenetic. In part it resulted by in-situ magmatic processes that included crystal-melt fractionation during injection of magma mushes, mingling, local melt segregation and mixing with crustal partial melts. The country rock is affected by penetrative ductile deformation and regional metamorphism developed during mid-Cretaceous Andean main orogenic phase. It also shows an overimposed pluton-margin parallel foliation and a post-kinematic contact metamorphic aureole. On the other hand, the UP has a concentric igneous foliation parallel to pluton margins interpreted as a primary magmatic feature. The above evidences, along with absence of subsolidus fabrics and metamorphism, indicate the pluton post-date peak regional metamorphism and ductile structures in the country rock. The new zircon ages constrain the top age of early Andean deformation, as well as the magmatic gap registered for the end of the Cretaceous, and confirm an emplacement during a recorded compressive regime that transmitted shortening to the foreland. © 2018 Elsevier Ltd
format JOUR
author González Guillot, M.
Ghiglione, M.
Escayola, M.
Martins Pimentel, M.
Mortensen, J.
Acevedo, R.
author_facet González Guillot, M.
Ghiglione, M.
Escayola, M.
Martins Pimentel, M.
Mortensen, J.
Acevedo, R.
author_sort González Guillot, M.
title Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes
title_short Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes
title_full Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes
title_fullStr Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes
title_full_unstemmed Ushuaia pluton: Magma diversification, emplacement and relation with regional tectonics in the southernmost Andes
title_sort ushuaia pluton: magma diversification, emplacement and relation with regional tectonics in the southernmost andes
url http://hdl.handle.net/20.500.12110/paper_08959811_v88_n_p497_GonzalezGuillot
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