Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan

Autores
Tibaldi, A.M.; Otamendi, J.E.; Cristofolini, E.A.; Vujovich, G.I.; Martino, R.D.
Año de publicación
2009
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
A sequence of plutonic mafic rocks inter-stratified with both mafic- and metasedimentary-derived migmatites is found along the San Juan valley in the center of the Sierra de Valle Fértil. This natural example shows the transition from igneous to metamorphic petrologic processes which occurred during the crystallization of mafic magmas and the subsequent partial melting of crystallized gabbroic rocks. This work studies the mineralogical changes associate to this petrologic transition. Thermobarometric estimates based on amphibole-plagioclase indicate that the mafic magmas crystallized at around 1100°C and 5 ± 0.5 kbar. The conditions under which gabbroic rocks were partially melted are estimated using two pyroxenes ther-mometry and amphibole-plagioclase thermobarometry. Similar physical conditions in the range between 740 and 840°C and 5 to 6.5 kbar are recovery from mineral assemblages in the mesosomes and leucosomes of mafic migmatites. The main mineral compositional changes that accompanied the partial process of the gabbroic rocks are: 1) depletion of aluminium content and Mg# ratio in pyroxenes; 2) depletion of anorthite mole fraction of the plagioclases; and 3) depletion of the Mg# ratio in amphiboles. These mineral compositional variations are consistent with those found by experimentally melting mafic protoliths. Experimental results showed that the temperature for promoting amphibole-dehydration melting in mafic proto-liths is of around 850°C, whereas the addition of an aqueous fluid would lower the melting temperature to around 800°C. Combining field relationships, textural features, mineral compositional variations and thermo-barometric estimates with experimental results, we demonstrated that the transition from igneous mafic rocks to mafic migmatites was due to isobaric cooling. Moreover, repetitive intrusion of mafic magmas sustained the sequence at granulite-facies conditions, so avoiding rapid cooling. The natural case from the centre of the Sierra de Valle Fértil is interpreted to expose an example of the plutonic-me-tamorphic core of the Famatinian magmatic arc, where the abnormally high metamorphic gradient provide evidence that large volume of mafic magmas reached and emplaced at paleodepths of between 16 and 20 kilometres.
Fil:Vujovich, G.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fuente
Rev. Asoc. Geol. Argent. 2009;65(3):487-503
Materia
Famatinian arc
Mafic migmatites
Mafic rocks
Magmatic metamorphism
Thermobarometry
amphibole
chemical composition
cooling
crystallization
emplacement
gabbro
mafic rock
metamorphism
migmatite
partial melting
petrology
phase transition
plagioclase
Argentina
San Juan [Argentina]
Sierra de Valle Fertil
Sierras Pampeanas
Nivel de accesibilidad
acceso abierto
Condiciones de uso
http://creativecommons.org/licenses/by/2.5/ar
Repositorio
Biblioteca Digital (UBA-FCEN)
Institución
Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
OAI Identificador
paperaa:paper_00044822_v65_n3_p487_Tibaldi

id BDUBAFCEN_63cf6fa1e92adccc761d16d991e0e890
oai_identifier_str paperaa:paper_00044822_v65_n3_p487_Tibaldi
network_acronym_str BDUBAFCEN
repository_id_str 1896
network_name_str Biblioteca Digital (UBA-FCEN)
spelling Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan Tibaldi, A.M.Otamendi, J.E.Cristofolini, E.A.Vujovich, G.I.Martino, R.D.Famatinian arcMafic migmatitesMafic rocksMagmatic metamorphismThermobarometryamphibolechemical compositioncoolingcrystallizationemplacementgabbromafic rockmetamorphismmigmatitepartial meltingpetrologyphase transitionplagioclaseArgentinaSan Juan [Argentina]Sierra de Valle FertilSierras PampeanasA sequence of plutonic mafic rocks inter-stratified with both mafic- and metasedimentary-derived migmatites is found along the San Juan valley in the center of the Sierra de Valle Fértil. This natural example shows the transition from igneous to metamorphic petrologic processes which occurred during the crystallization of mafic magmas and the subsequent partial melting of crystallized gabbroic rocks. This work studies the mineralogical changes associate to this petrologic transition. Thermobarometric estimates based on amphibole-plagioclase indicate that the mafic magmas crystallized at around 1100°C and 5 ± 0.5 kbar. The conditions under which gabbroic rocks were partially melted are estimated using two pyroxenes ther-mometry and amphibole-plagioclase thermobarometry. Similar physical conditions in the range between 740 and 840°C and 5 to 6.5 kbar are recovery from mineral assemblages in the mesosomes and leucosomes of mafic migmatites. The main mineral compositional changes that accompanied the partial process of the gabbroic rocks are: 1) depletion of aluminium content and Mg# ratio in pyroxenes; 2) depletion of anorthite mole fraction of the plagioclases; and 3) depletion of the Mg# ratio in amphiboles. These mineral compositional variations are consistent with those found by experimentally melting mafic protoliths. Experimental results showed that the temperature for promoting amphibole-dehydration melting in mafic proto-liths is of around 850°C, whereas the addition of an aqueous fluid would lower the melting temperature to around 800°C. Combining field relationships, textural features, mineral compositional variations and thermo-barometric estimates with experimental results, we demonstrated that the transition from igneous mafic rocks to mafic migmatites was due to isobaric cooling. Moreover, repetitive intrusion of mafic magmas sustained the sequence at granulite-facies conditions, so avoiding rapid cooling. The natural case from the centre of the Sierra de Valle Fértil is interpreted to expose an example of the plutonic-me-tamorphic core of the Famatinian magmatic arc, where the abnormally high metamorphic gradient provide evidence that large volume of mafic magmas reached and emplaced at paleodepths of between 16 and 20 kilometres.Fil:Vujovich, G.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.2009info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfhttp://hdl.handle.net/20.500.12110/paper_00044822_v65_n3_p487_TibaldiRev. Asoc. Geol. Argent. 2009;65(3):487-503reponame:Biblioteca Digital (UBA-FCEN)instname:Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturalesinstacron:UBA-FCENenginfo:eu-repo/semantics/openAccesshttp://creativecommons.org/licenses/by/2.5/ar2025-09-29T13:43:09Zpaperaa:paper_00044822_v65_n3_p487_TibaldiInstitucionalhttps://digital.bl.fcen.uba.ar/Universidad públicaNo correspondehttps://digital.bl.fcen.uba.ar/cgi-bin/oaiserver.cgiana@bl.fcen.uba.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:18962025-09-29 13:43:10.449Biblioteca Digital (UBA-FCEN) - Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturalesfalse
dc.title.none.fl_str_mv Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
title Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
spellingShingle Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
Tibaldi, A.M.
Famatinian arc
Mafic migmatites
Mafic rocks
Magmatic metamorphism
Thermobarometry
amphibole
chemical composition
cooling
crystallization
emplacement
gabbro
mafic rock
metamorphism
migmatite
partial melting
petrology
phase transition
plagioclase
Argentina
San Juan [Argentina]
Sierra de Valle Fertil
Sierras Pampeanas
title_short Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
title_full Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
title_fullStr Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
title_full_unstemmed Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
title_sort Physical conditions for the formation of gabbros and migmatites derived from mafic rocks in the center of Sierra de Valle Fértil, San Juan
dc.creator.none.fl_str_mv Tibaldi, A.M.
Otamendi, J.E.
Cristofolini, E.A.
Vujovich, G.I.
Martino, R.D.
author Tibaldi, A.M.
author_facet Tibaldi, A.M.
Otamendi, J.E.
Cristofolini, E.A.
Vujovich, G.I.
Martino, R.D.
author_role author
author2 Otamendi, J.E.
Cristofolini, E.A.
Vujovich, G.I.
Martino, R.D.
author2_role author
author
author
author
dc.subject.none.fl_str_mv Famatinian arc
Mafic migmatites
Mafic rocks
Magmatic metamorphism
Thermobarometry
amphibole
chemical composition
cooling
crystallization
emplacement
gabbro
mafic rock
metamorphism
migmatite
partial melting
petrology
phase transition
plagioclase
Argentina
San Juan [Argentina]
Sierra de Valle Fertil
Sierras Pampeanas
topic Famatinian arc
Mafic migmatites
Mafic rocks
Magmatic metamorphism
Thermobarometry
amphibole
chemical composition
cooling
crystallization
emplacement
gabbro
mafic rock
metamorphism
migmatite
partial melting
petrology
phase transition
plagioclase
Argentina
San Juan [Argentina]
Sierra de Valle Fertil
Sierras Pampeanas
dc.description.none.fl_txt_mv A sequence of plutonic mafic rocks inter-stratified with both mafic- and metasedimentary-derived migmatites is found along the San Juan valley in the center of the Sierra de Valle Fértil. This natural example shows the transition from igneous to metamorphic petrologic processes which occurred during the crystallization of mafic magmas and the subsequent partial melting of crystallized gabbroic rocks. This work studies the mineralogical changes associate to this petrologic transition. Thermobarometric estimates based on amphibole-plagioclase indicate that the mafic magmas crystallized at around 1100°C and 5 ± 0.5 kbar. The conditions under which gabbroic rocks were partially melted are estimated using two pyroxenes ther-mometry and amphibole-plagioclase thermobarometry. Similar physical conditions in the range between 740 and 840°C and 5 to 6.5 kbar are recovery from mineral assemblages in the mesosomes and leucosomes of mafic migmatites. The main mineral compositional changes that accompanied the partial process of the gabbroic rocks are: 1) depletion of aluminium content and Mg# ratio in pyroxenes; 2) depletion of anorthite mole fraction of the plagioclases; and 3) depletion of the Mg# ratio in amphiboles. These mineral compositional variations are consistent with those found by experimentally melting mafic protoliths. Experimental results showed that the temperature for promoting amphibole-dehydration melting in mafic proto-liths is of around 850°C, whereas the addition of an aqueous fluid would lower the melting temperature to around 800°C. Combining field relationships, textural features, mineral compositional variations and thermo-barometric estimates with experimental results, we demonstrated that the transition from igneous mafic rocks to mafic migmatites was due to isobaric cooling. Moreover, repetitive intrusion of mafic magmas sustained the sequence at granulite-facies conditions, so avoiding rapid cooling. The natural case from the centre of the Sierra de Valle Fértil is interpreted to expose an example of the plutonic-me-tamorphic core of the Famatinian magmatic arc, where the abnormally high metamorphic gradient provide evidence that large volume of mafic magmas reached and emplaced at paleodepths of between 16 and 20 kilometres.
Fil:Vujovich, G.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
description A sequence of plutonic mafic rocks inter-stratified with both mafic- and metasedimentary-derived migmatites is found along the San Juan valley in the center of the Sierra de Valle Fértil. This natural example shows the transition from igneous to metamorphic petrologic processes which occurred during the crystallization of mafic magmas and the subsequent partial melting of crystallized gabbroic rocks. This work studies the mineralogical changes associate to this petrologic transition. Thermobarometric estimates based on amphibole-plagioclase indicate that the mafic magmas crystallized at around 1100°C and 5 ± 0.5 kbar. The conditions under which gabbroic rocks were partially melted are estimated using two pyroxenes ther-mometry and amphibole-plagioclase thermobarometry. Similar physical conditions in the range between 740 and 840°C and 5 to 6.5 kbar are recovery from mineral assemblages in the mesosomes and leucosomes of mafic migmatites. The main mineral compositional changes that accompanied the partial process of the gabbroic rocks are: 1) depletion of aluminium content and Mg# ratio in pyroxenes; 2) depletion of anorthite mole fraction of the plagioclases; and 3) depletion of the Mg# ratio in amphiboles. These mineral compositional variations are consistent with those found by experimentally melting mafic protoliths. Experimental results showed that the temperature for promoting amphibole-dehydration melting in mafic proto-liths is of around 850°C, whereas the addition of an aqueous fluid would lower the melting temperature to around 800°C. Combining field relationships, textural features, mineral compositional variations and thermo-barometric estimates with experimental results, we demonstrated that the transition from igneous mafic rocks to mafic migmatites was due to isobaric cooling. Moreover, repetitive intrusion of mafic magmas sustained the sequence at granulite-facies conditions, so avoiding rapid cooling. The natural case from the centre of the Sierra de Valle Fértil is interpreted to expose an example of the plutonic-me-tamorphic core of the Famatinian magmatic arc, where the abnormally high metamorphic gradient provide evidence that large volume of mafic magmas reached and emplaced at paleodepths of between 16 and 20 kilometres.
publishDate 2009
dc.date.none.fl_str_mv 2009
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
http://purl.org/coar/resource_type/c_6501
info:ar-repo/semantics/articulo
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/20.500.12110/paper_00044822_v65_n3_p487_Tibaldi
url http://hdl.handle.net/20.500.12110/paper_00044822_v65_n3_p487_Tibaldi
dc.language.none.fl_str_mv eng
language eng
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by/2.5/ar
eu_rights_str_mv openAccess
rights_invalid_str_mv http://creativecommons.org/licenses/by/2.5/ar
dc.format.none.fl_str_mv application/pdf
dc.source.none.fl_str_mv Rev. Asoc. Geol. Argent. 2009;65(3):487-503
reponame:Biblioteca Digital (UBA-FCEN)
instname:Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
instacron:UBA-FCEN
reponame_str Biblioteca Digital (UBA-FCEN)
collection Biblioteca Digital (UBA-FCEN)
instname_str Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
instacron_str UBA-FCEN
institution UBA-FCEN
repository.name.fl_str_mv Biblioteca Digital (UBA-FCEN) - Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
repository.mail.fl_str_mv ana@bl.fcen.uba.ar
_version_ 1844618740282425344
score 13.070432