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...
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2011
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paper:paper_08959811_v32_n3_p183_Zaffarana2023-06-08T15:48:34Z Reassessment of the volume of the Las Aguilas mafic-ultramafic intrusives, San Luis, Argentina, based on an alternative geophysical model Zaffarana, Claudia Beatriz Geuna, Silvana Evangelina Poma, Stella Maris Patiño Douce, Alberto Emilio 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. 2011 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v32_n3_p183_Zaffarana 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, Claudia Beatriz Geuna, Silvana Evangelina Poma, Stella Maris Patiño Douce, Alberto Emilio 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. |
| author |
Zaffarana, Claudia Beatriz Geuna, Silvana Evangelina Poma, Stella Maris Patiño Douce, Alberto Emilio |
| author_facet |
Zaffarana, Claudia Beatriz Geuna, Silvana Evangelina Poma, Stella Maris Patiño Douce, Alberto Emilio |
| author_sort |
Zaffarana, Claudia Beatriz |
| 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 |
| publishDate |
2011 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v32_n3_p183_Zaffarana http://hdl.handle.net/20.500.12110/paper_08959811_v32_n3_p183_Zaffarana |
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