Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina

Abstract We carried out magnetic analyses on a sequence of Cretaceous alkaline-transitional subaerial basalts of Córdoba Province, Argentina, which have high-Ti magnetite as the main opaque phase. Three different groups are identified based on the degree of high-temperature oxidation during the lava...

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Autores principales: Geuna, S.E., Lagorio, S.L., Vizán, H.
Formato: SER
Materias:
basalt
breccia
Cretaceous
lava flow
magnetic field
magnetic property
magnetic susceptibility
oxidation
remanent magnetization
titanomagnetite
Argentina
Cordoba [Argentina]
Sierra Chica de Cordoba
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_03058719_v396_n_p239_Geuna
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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_03058719_v396_n_p239_Geuna2023-10-03T15:22:03Z Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina Geuna, S.E. Lagorio, S.L. Vizán, H. basalt breccia Cretaceous lava flow magnetic field magnetic property magnetic susceptibility oxidation remanent magnetization titanomagnetite Argentina Cordoba [Argentina] Sierra Chica de Cordoba Abstract We carried out magnetic analyses on a sequence of Cretaceous alkaline-transitional subaerial basalts of Córdoba Province, Argentina, which have high-Ti magnetite as the main opaque phase. Three different groups are identified based on the degree of high-temperature oxidation during the lava extrusion, combined with superimposed maghemitization and hematization. In the first group, titanomagnetites are optically homogeneous or exhibit coarse intergrowths with ilmenite. The magnetic susceptibility and its variation with temperature and magnetic field point to Ti-poorer compositions than those indicated by electron microprobe, which is interpreted as due to low-temperature oxidation with subsolvus microexsolution. The second group of basalts suffered moderate high-temperature oxidation, with crowded exsolved ilmenite laths within a Ti-poor magnetitess host, followed by maghemitization and hematite replacement. The third group shows a strongly advanced degree of low-temperature alteration, with the virtual disappearance of magnetite. Based on magnetic properties and field tests applied to the magnetic remanence, we interpret that maghemitization and hematization must have been responsible for the acquisition of a stable magnetic remanence, in the presence of hydrothermal fluids coeval with volcanism. The most advanced degree of alteration, typical of highly porous amygdaloidal lava flows and volcanic breccias, occurred later, probably due to weathering. © 2015 The Geological Society of London. Fil:Geuna, S.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Lagorio, S.L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Vizán, H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. SER info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_03058719_v396_n_p239_Geuna
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic basalt
breccia
Cretaceous
lava flow
magnetic field
magnetic property
magnetic susceptibility
oxidation
remanent magnetization
titanomagnetite
Argentina
Cordoba [Argentina]
Sierra Chica de Cordoba
spellingShingle basalt
breccia
Cretaceous
lava flow
magnetic field
magnetic property
magnetic susceptibility
oxidation
remanent magnetization
titanomagnetite
Argentina
Cordoba [Argentina]
Sierra Chica de Cordoba
Geuna, S.E.
Lagorio, S.L.
Vizán, H.
Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina
topic_facet basalt
breccia
Cretaceous
lava flow
magnetic field
magnetic property
magnetic susceptibility
oxidation
remanent magnetization
titanomagnetite
Argentina
Cordoba [Argentina]
Sierra Chica de Cordoba
description Abstract We carried out magnetic analyses on a sequence of Cretaceous alkaline-transitional subaerial basalts of Córdoba Province, Argentina, which have high-Ti magnetite as the main opaque phase. Three different groups are identified based on the degree of high-temperature oxidation during the lava extrusion, combined with superimposed maghemitization and hematization. In the first group, titanomagnetites are optically homogeneous or exhibit coarse intergrowths with ilmenite. The magnetic susceptibility and its variation with temperature and magnetic field point to Ti-poorer compositions than those indicated by electron microprobe, which is interpreted as due to low-temperature oxidation with subsolvus microexsolution. The second group of basalts suffered moderate high-temperature oxidation, with crowded exsolved ilmenite laths within a Ti-poor magnetitess host, followed by maghemitization and hematite replacement. The third group shows a strongly advanced degree of low-temperature alteration, with the virtual disappearance of magnetite. Based on magnetic properties and field tests applied to the magnetic remanence, we interpret that maghemitization and hematization must have been responsible for the acquisition of a stable magnetic remanence, in the presence of hydrothermal fluids coeval with volcanism. The most advanced degree of alteration, typical of highly porous amygdaloidal lava flows and volcanic breccias, occurred later, probably due to weathering. © 2015 The Geological Society of London.
format SER
author Geuna, S.E.
Lagorio, S.L.
Vizán, H.
author_facet Geuna, S.E.
Lagorio, S.L.
Vizán, H.
author_sort Geuna, S.E.
title Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina
title_short Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina
title_full Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina
title_fullStr Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina
title_full_unstemmed Oxidation processes and their effects on the magnetic remanence of Early Cretaceous subaerial basalts from Sierra Chica de Córdoba, Argentina
title_sort oxidation processes and their effects on the magnetic remanence of early cretaceous subaerial basalts from sierra chica de córdoba, argentina
url http://hdl.handle.net/20.500.12110/paper_03058719_v396_n_p239_Geuna
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AT lagoriosl oxidationprocessesandtheireffectsonthemagneticremanenceofearlycretaceoussubaerialbasaltsfromsierrachicadecordobaargentina
AT vizanh oxidationprocessesandtheireffectsonthemagneticremanenceofearlycretaceoussubaerialbasaltsfromsierrachicadecordobaargentina
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