Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results

Detalhes bibliográficos
Autor(a) principal: Moraes,Renato
Data de Publicação: 2015
Outros Autores: Nicollet,Christian, Barbosa,Johildo Salomão Figueiredo, Fuck,Reinhardt Adolfo, Sampaio,Antônio Rabelo
Tipo de documento: Artigo
Idioma: eng
Título da fonte: Brazilian Journal of Geology
Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892015000500517
Resumo: In southern Bahia, there are outcrops of migmatites and granulites in the Jequitinhonha Complex, which is part of the northern portion of the Araçuaí Orogen. Migmatites (garnet-cordierite diatexite) dominate the metamorphic rocks and host lenses and layers of felsic garnet granulite. The conditions of temperature and pressure of metamorphism were calculated using conventional thermobarometry and the software THERMOCALC. Values around 850 °C and 7 kbar were obtained with THERMOCALC. The calculations for the garnet-cordierite diatexite were made considering aH2O equal to 1, but the best results of calculations for the granulites are obtained with aH2O values of 0.3. Pressure values obtained with GAPES resulted in consistent values with THERMOCALC, but the pair garnet-orthopyroxene always produces low values for temperature and high ones for pressure. The results are consistent with the presence of the pair garnet and cordierite in diatexite and orthopyroxene in felsic granulite. From the tectonic point of view, the setting in which metamorphism of these rocks occurred requires high heat flow with a thermal anomaly in mid continental crust, as indicated by values of 7 kbar. Recent studies have favored the closure of a back-arc basin for this tectonic setting, but it does not solve the problem that the time span between metamorphic peak and the end of granite intrusions, involving large bodies of charnockite, is more than 80 million years. The model of tectonic switching is suggested here as it can explain the maintenance of high temperatures for a more extended interval of time.
id SBGEO-1_a5290f84bc2632439e953098b0833f92
oai_identifier_str oai:scielo:S2317-48892015000500517
network_acronym_str SBGEO-1
network_name_str Brazilian Journal of Geology
repository_id_str
spelling Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current resultsAraçuaí OrogenGranuliteMigmatiteThermobarometryIn southern Bahia, there are outcrops of migmatites and granulites in the Jequitinhonha Complex, which is part of the northern portion of the Araçuaí Orogen. Migmatites (garnet-cordierite diatexite) dominate the metamorphic rocks and host lenses and layers of felsic garnet granulite. The conditions of temperature and pressure of metamorphism were calculated using conventional thermobarometry and the software THERMOCALC. Values around 850 °C and 7 kbar were obtained with THERMOCALC. The calculations for the garnet-cordierite diatexite were made considering aH2O equal to 1, but the best results of calculations for the granulites are obtained with aH2O values of 0.3. Pressure values obtained with GAPES resulted in consistent values with THERMOCALC, but the pair garnet-orthopyroxene always produces low values for temperature and high ones for pressure. The results are consistent with the presence of the pair garnet and cordierite in diatexite and orthopyroxene in felsic granulite. From the tectonic point of view, the setting in which metamorphism of these rocks occurred requires high heat flow with a thermal anomaly in mid continental crust, as indicated by values of 7 kbar. Recent studies have favored the closure of a back-arc basin for this tectonic setting, but it does not solve the problem that the time span between metamorphic peak and the end of granite intrusions, involving large bodies of charnockite, is more than 80 million years. The model of tectonic switching is suggested here as it can explain the maintenance of high temperatures for a more extended interval of time.Sociedade Brasileira de Geologia2015-12-01info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersiontext/htmlhttp://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892015000500517Brazilian Journal of Geology v.45 n.4 2015reponame:Brazilian Journal of Geologyinstname:Sociedade Brasileira de Geologia (SBGEO)instacron:SBGEO10.1590/2317-4889201520150026info:eu-repo/semantics/openAccessMoraes,RenatoNicollet,ChristianBarbosa,Johildo Salomão FigueiredoFuck,Reinhardt AdolfoSampaio,Antônio Rabeloeng2015-12-21T00:00:00Zoai:scielo:S2317-48892015000500517Revistahttp://bjg.siteoficial.ws/index.htmhttps://old.scielo.br/oai/scielo-oai.phpsbgsede@sbgeo.org.br||claudio.riccomini@gmail.com2317-46922317-4692opendoar:2015-12-21T00:00Brazilian Journal of Geology - Sociedade Brasileira de Geologia (SBGEO)false
dc.title.none.fl_str_mv Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
title Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
spellingShingle Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
Moraes,Renato
Araçuaí Orogen
Granulite
Migmatite
Thermobarometry
title_short Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
title_full Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
title_fullStr Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
title_full_unstemmed Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
title_sort Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results
author Moraes,Renato
author_facet Moraes,Renato
Nicollet,Christian
Barbosa,Johildo Salomão Figueiredo
Fuck,Reinhardt Adolfo
Sampaio,Antônio Rabelo
author_role author
author2 Nicollet,Christian
Barbosa,Johildo Salomão Figueiredo
Fuck,Reinhardt Adolfo
Sampaio,Antônio Rabelo
author2_role author
author
author
author
dc.contributor.author.fl_str_mv Moraes,Renato
Nicollet,Christian
Barbosa,Johildo Salomão Figueiredo
Fuck,Reinhardt Adolfo
Sampaio,Antônio Rabelo
dc.subject.por.fl_str_mv Araçuaí Orogen
Granulite
Migmatite
Thermobarometry
topic Araçuaí Orogen
Granulite
Migmatite
Thermobarometry
description In southern Bahia, there are outcrops of migmatites and granulites in the Jequitinhonha Complex, which is part of the northern portion of the Araçuaí Orogen. Migmatites (garnet-cordierite diatexite) dominate the metamorphic rocks and host lenses and layers of felsic garnet granulite. The conditions of temperature and pressure of metamorphism were calculated using conventional thermobarometry and the software THERMOCALC. Values around 850 °C and 7 kbar were obtained with THERMOCALC. The calculations for the garnet-cordierite diatexite were made considering aH2O equal to 1, but the best results of calculations for the granulites are obtained with aH2O values of 0.3. Pressure values obtained with GAPES resulted in consistent values with THERMOCALC, but the pair garnet-orthopyroxene always produces low values for temperature and high ones for pressure. The results are consistent with the presence of the pair garnet and cordierite in diatexite and orthopyroxene in felsic granulite. From the tectonic point of view, the setting in which metamorphism of these rocks occurred requires high heat flow with a thermal anomaly in mid continental crust, as indicated by values of 7 kbar. Recent studies have favored the closure of a back-arc basin for this tectonic setting, but it does not solve the problem that the time span between metamorphic peak and the end of granite intrusions, involving large bodies of charnockite, is more than 80 million years. The model of tectonic switching is suggested here as it can explain the maintenance of high temperatures for a more extended interval of time.
publishDate 2015
dc.date.none.fl_str_mv 2015-12-01
dc.type.driver.fl_str_mv info:eu-repo/semantics/article
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.uri.fl_str_mv http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892015000500517
url http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892015000500517
dc.language.iso.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv 10.1590/2317-4889201520150026
dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv text/html
dc.publisher.none.fl_str_mv Sociedade Brasileira de Geologia
publisher.none.fl_str_mv Sociedade Brasileira de Geologia
dc.source.none.fl_str_mv Brazilian Journal of Geology v.45 n.4 2015
reponame:Brazilian Journal of Geology
instname:Sociedade Brasileira de Geologia (SBGEO)
instacron:SBGEO
instname_str Sociedade Brasileira de Geologia (SBGEO)
instacron_str SBGEO
institution SBGEO
reponame_str Brazilian Journal of Geology
collection Brazilian Journal of Geology
repository.name.fl_str_mv Brazilian Journal of Geology - Sociedade Brasileira de Geologia (SBGEO)
repository.mail.fl_str_mv sbgsede@sbgeo.org.br||claudio.riccomini@gmail.com
_version_ 1752122398381965312