The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion

Within the southern part of the Sierra Pampeanas (the Sierra de San Luis, Argentina), a series of extensive intrusive bodies are regarded to post-date the Famatinian cycle but were emplaced during the Achalian, a period of heterogeneous deformation along crustal scale fault zones. The largest of tho...

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Detalles Bibliográficos
Autores principales: Siegesmund, S., Steenken, A., López de Luchi, M.G., Wemmer, K., Hoffmann, A., Mosch, S.
Formato: JOUR
Materias:
Geochronology
Granite emplacement
Pre-Andean margin of Gondwana
Sierras pampeanas orientales
Thermal modelling
batholith
crustal evolution
emplacement
geochronology
granite
numerical model
shear zone
Argentina
Sierras Pampeanas
South America
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_14373254_v93_n1_p23_Siegesmund
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_14373254_v93_n1_p23_Siegesmund
record_format dspace
spelling todo:paper_14373254_v93_n1_p23_Siegesmund2023-10-03T16:16:02Z The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion Siegesmund, S. Steenken, A. López de Luchi, M.G. Wemmer, K. Hoffmann, A. Mosch, S. Geochronology Granite emplacement Pre-Andean margin of Gondwana Sierras pampeanas orientales Thermal modelling batholith crustal evolution emplacement geochronology granite numerical model shear zone Argentina Sierras Pampeanas South America Within the southern part of the Sierra Pampeanas (the Sierra de San Luis, Argentina), a series of extensive intrusive bodies are regarded to post-date the Famatinian cycle but were emplaced during the Achalian, a period of heterogeneous deformation along crustal scale fault zones. The largest of those is the Las Chacras-Potrerillos batholith that is situated at the northern end of the transpressive, sinistral Guzmán shear zone. This composite pluton exhibits three sub-domains that comprise two granitoid sub-units each: The southern Potrerillos stock (muscovite-bearing red granite and biotitebearing red granite) and the central (biotite porphyritic granite and giant porphyritic granite) and northern domain (equigranular granite and porphyritic granite) of the Las Chacras stock. The crystallisation ages of the biotite porphyritic granite is around 381 Ma (U/Pb on zircons and Pb/Pb on sphene), while the host rock was already cooled below 350 °C at 420 Ma. Thermal modelling approaches favour a pulsed intrusion with a duration of 1.5 Ma. The emplacement was followed by rapid cooling below the muscovite cooling temperature. Biotite cooling ages in different sub-units reflect either a long-lasting cooling history of approximately 30 Ma (which is supported by the modelling) or a reheating effect at around 350 Ma. Devonian-age determinations on the fault rocks and granitoids point to a syn-tectonic emplacement of the batholith. The pluton is interpreted to be positioned at the crossover of sinistral shear zones. The origin of this NNE directed extensional setting in a transpressive regime seems to be related to the transfer of displacement along a secondary set of NNW-trending sinistral faults. The final emplacement is due to a subsequent ballooning of the batholith following the direction of space creation. This model is based on the relative timing of the emplacement sequence and macroscopically visible planar fabrics in the field as well as magnetic fabric data. Our results indicate that the emplacement is syn-kinematic with respect to the Achalian deformation event. © Springer-Verlag 2003. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_14373254_v93_n1_p23_Siegesmund
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Geochronology
Granite emplacement
Pre-Andean margin of Gondwana
Sierras pampeanas orientales
Thermal modelling
batholith
crustal evolution
emplacement
geochronology
granite
numerical model
shear zone
Argentina
Sierras Pampeanas
South America
spellingShingle Geochronology
Granite emplacement
Pre-Andean margin of Gondwana
Sierras pampeanas orientales
Thermal modelling
batholith
crustal evolution
emplacement
geochronology
granite
numerical model
shear zone
Argentina
Sierras Pampeanas
South America
Siegesmund, S.
Steenken, A.
López de Luchi, M.G.
Wemmer, K.
Hoffmann, A.
Mosch, S.
The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion
topic_facet Geochronology
Granite emplacement
Pre-Andean margin of Gondwana
Sierras pampeanas orientales
Thermal modelling
batholith
crustal evolution
emplacement
geochronology
granite
numerical model
shear zone
Argentina
Sierras Pampeanas
South America
description Within the southern part of the Sierra Pampeanas (the Sierra de San Luis, Argentina), a series of extensive intrusive bodies are regarded to post-date the Famatinian cycle but were emplaced during the Achalian, a period of heterogeneous deformation along crustal scale fault zones. The largest of those is the Las Chacras-Potrerillos batholith that is situated at the northern end of the transpressive, sinistral Guzmán shear zone. This composite pluton exhibits three sub-domains that comprise two granitoid sub-units each: The southern Potrerillos stock (muscovite-bearing red granite and biotitebearing red granite) and the central (biotite porphyritic granite and giant porphyritic granite) and northern domain (equigranular granite and porphyritic granite) of the Las Chacras stock. The crystallisation ages of the biotite porphyritic granite is around 381 Ma (U/Pb on zircons and Pb/Pb on sphene), while the host rock was already cooled below 350 °C at 420 Ma. Thermal modelling approaches favour a pulsed intrusion with a duration of 1.5 Ma. The emplacement was followed by rapid cooling below the muscovite cooling temperature. Biotite cooling ages in different sub-units reflect either a long-lasting cooling history of approximately 30 Ma (which is supported by the modelling) or a reheating effect at around 350 Ma. Devonian-age determinations on the fault rocks and granitoids point to a syn-tectonic emplacement of the batholith. The pluton is interpreted to be positioned at the crossover of sinistral shear zones. The origin of this NNE directed extensional setting in a transpressive regime seems to be related to the transfer of displacement along a secondary set of NNW-trending sinistral faults. The final emplacement is due to a subsequent ballooning of the batholith following the direction of space creation. This model is based on the relative timing of the emplacement sequence and macroscopically visible planar fabrics in the field as well as magnetic fabric data. Our results indicate that the emplacement is syn-kinematic with respect to the Achalian deformation event. © Springer-Verlag 2003.
format JOUR
author Siegesmund, S.
Steenken, A.
López de Luchi, M.G.
Wemmer, K.
Hoffmann, A.
Mosch, S.
author_facet Siegesmund, S.
Steenken, A.
López de Luchi, M.G.
Wemmer, K.
Hoffmann, A.
Mosch, S.
author_sort Siegesmund, S.
title The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion
title_short The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion
title_full The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion
title_fullStr The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion
title_full_unstemmed The Las Chacras-Potrerillos batholith (Pampean Ranges, Argentina): Structural evidences, emplacement and timing of the intrusion
title_sort las chacras-potrerillos batholith (pampean ranges, argentina): structural evidences, emplacement and timing of the intrusion
url http://hdl.handle.net/20.500.12110/paper_14373254_v93_n1_p23_Siegesmund
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