Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model

In the Sierra de San Luis, Central Argentina, a belt of small and discontinuous lenses of mafic-ultramafic rocks intrude a polydeformed basement and are thought to be the cause of a local increase of the metamorphic grade from amphibolite to granulite facies conditions. This assumption was especiall...

Descripción completa

Guardado en:
Detalles Bibliográficos
Autores principales: Zaffarana, C., Geuna, S., Poma, S., Patiño Douce, A.
Formato: JOUR
Materias:
Gravimetric model
Mafic-ultramafic rocks
Thermal effect
Virorco
amphibolite facies
basement rock
deformation
emplacement
geophysical method
granulite facies
gravimetry
gravity anomaly
igneous intrusion
mafic rock
magma
temperature effect
ultramafic rock
Argentina
Las Aguilas
San Luis
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_08959811_v32_n3_p183_Zaffarana
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_08959811_v32_n3_p183_Zaffarana
record_format dspace
spelling todo:paper_08959811_v32_n3_p183_Zaffarana2023-10-03T15:43:00Z Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model Zaffarana, C. Geuna, S. Poma, S. Patiño Douce, A. Gravimetric model Mafic-ultramafic rocks Thermal effect Virorco amphibolite facies basement rock deformation emplacement geophysical method granulite facies gravimetry gravity anomaly igneous intrusion mafic rock magma temperature effect ultramafic rock Argentina Las Aguilas San Luis In the Sierra de San Luis, Central Argentina, a belt of small and discontinuous lenses of mafic-ultramafic rocks intrude a polydeformed basement and are thought to be the cause of a local increase of the metamorphic grade from amphibolite to granulite facies conditions. This assumption was especially based on forward modelling of a huge gravity anomaly centered over the Sierra de San Luis, which lead some workers to think that a vast volume of mafic-ultramafic rocks lay in shallow levels. Here, we propose an alternative model to explain this anomaly, in which the mafic-ultramafic intrusion is not the ultimate source. Therefore, there is no need to propose a bigger size than that observed in outcrops for the mafic-ultramafic bodies. The thermal effect of the emplacement of mafic-ultramafic sills and dikes on the host rocks was estimated applying a simple analytical solution (error function) for heating of a semi-infinite half space (the country rocks) in contact with a hotter sheet of finite thickness (the mafic-ultramafic intrusion). Results indicate that the effect of the intrusion of these hot mafic magmas is local, because beyond a few hundred meters from the contact zone temperatures never exceed 600 °C, and a few km from the intrusion they barely increase 50 °C relative to the initial temperature. These results, together with the preservation of primary igneous characteristics (such as rhythmic layering) being overprinted by metamorphic textural changes, indicate that the intrusion occurred before regional deformation. It is suggested that the thermal anomaly in the Pringles Metamorphic Complex could have been mainly caused by factors inherent to their geodynamic setting. © 2011 Elsevier Ltd. Fil:Zaffarana, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Geuna, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Poma, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Patiño Douce, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_08959811_v32_n3_p183_Zaffarana
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Gravimetric model
Mafic-ultramafic rocks
Thermal effect
Virorco
amphibolite facies
basement rock
deformation
emplacement
geophysical method
granulite facies
gravimetry
gravity anomaly
igneous intrusion
mafic rock
magma
temperature effect
ultramafic rock
Argentina
Las Aguilas
San Luis
spellingShingle Gravimetric model
Mafic-ultramafic rocks
Thermal effect
Virorco
amphibolite facies
basement rock
deformation
emplacement
geophysical method
granulite facies
gravimetry
gravity anomaly
igneous intrusion
mafic rock
magma
temperature effect
ultramafic rock
Argentina
Las Aguilas
San Luis
Zaffarana, C.
Geuna, S.
Poma, S.
Patiño Douce, A.
Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model
topic_facet Gravimetric model
Mafic-ultramafic rocks
Thermal effect
Virorco
amphibolite facies
basement rock
deformation
emplacement
geophysical method
granulite facies
gravimetry
gravity anomaly
igneous intrusion
mafic rock
magma
temperature effect
ultramafic rock
Argentina
Las Aguilas
San Luis
description In the Sierra de San Luis, Central Argentina, a belt of small and discontinuous lenses of mafic-ultramafic rocks intrude a polydeformed basement and are thought to be the cause of a local increase of the metamorphic grade from amphibolite to granulite facies conditions. This assumption was especially based on forward modelling of a huge gravity anomaly centered over the Sierra de San Luis, which lead some workers to think that a vast volume of mafic-ultramafic rocks lay in shallow levels. Here, we propose an alternative model to explain this anomaly, in which the mafic-ultramafic intrusion is not the ultimate source. Therefore, there is no need to propose a bigger size than that observed in outcrops for the mafic-ultramafic bodies. The thermal effect of the emplacement of mafic-ultramafic sills and dikes on the host rocks was estimated applying a simple analytical solution (error function) for heating of a semi-infinite half space (the country rocks) in contact with a hotter sheet of finite thickness (the mafic-ultramafic intrusion). Results indicate that the effect of the intrusion of these hot mafic magmas is local, because beyond a few hundred meters from the contact zone temperatures never exceed 600 °C, and a few km from the intrusion they barely increase 50 °C relative to the initial temperature. These results, together with the preservation of primary igneous characteristics (such as rhythmic layering) being overprinted by metamorphic textural changes, indicate that the intrusion occurred before regional deformation. It is suggested that the thermal anomaly in the Pringles Metamorphic Complex could have been mainly caused by factors inherent to their geodynamic setting. © 2011 Elsevier Ltd.
format JOUR
author Zaffarana, C.
Geuna, S.
Poma, S.
Patiño Douce, A.
author_facet Zaffarana, C.
Geuna, S.
Poma, S.
Patiño Douce, A.
author_sort Zaffarana, C.
title Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model
title_short Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model
title_full Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model
title_fullStr Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model
title_full_unstemmed Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model
title_sort reassessment of the volume of the las aguilas mafic-ultramafic intrusives, san luis, argentina, based on an alternative geophysical model
url http://hdl.handle.net/20.500.12110/paper_08959811_v32_n3_p183_Zaffarana
work_keys_str_mv AT zaffaranac reassessmentofthevolumeofthelasaguilasmaficultramaficintrusivessanluisargentinabasedonanalternativegeophysicalmodel
AT geunas reassessmentofthevolumeofthelasaguilasmaficultramaficintrusivessanluisargentinabasedonanalternativegeophysicalmodel
AT pomas reassessmentofthevolumeofthelasaguilasmaficultramaficintrusivessanluisargentinabasedonanalternativegeophysicalmodel
AT patinodoucea reassessmentofthevolumeofthelasaguilasmaficultramaficintrusivessanluisargentinabasedonanalternativegeophysicalmodel
_version_ 1782030432776224768

Ejemplares similares