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
- Institución
- Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
- OAI Identificador
- paperaa:paper_00044822_v65_n3_p487_Tibaldi
Ver los metadatos del registro completo
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 |