Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil

The Serra Branca pegmatite in northeastern Brazil is unique because of its megacrysts of bluish-green amazonite currently exploited for ornamental purposes and as high-quality gemstones. Here we analyze microtextural, spectroscopic, and geochemical data on specimens from two magmatic generations of...

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Autores: Lira Santos, Glenda, de Brito Barreto, Sandra, Belo de Albuquerque e Souza, Igor Manoel, Ferreira de Araújo Neto, José, Sánchez-Muñoz, Luis, Montefalco de Lira Santos, Lauro Cézar
Tipo de documento: artigo
Estado:Versão publicada
Data de publicação:2022
País:España
Recursos:Consejo Superior de Investigaciones Científicas (CSIC)
Repositório:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/286821
Acesso em linha:http://hdl.handle.net/10261/286821
Access Level:Acceso aberto
Palavra-chave:Serra Branca amazonite pegmatite
Anorogenic pegmatite
Twin evolution
Spectroscopy
Geochemistry
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spelling Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern BrazilLira Santos, Glendade Brito Barreto, SandraBelo de Albuquerque e Souza, Igor ManoelFerreira de Araújo Neto, JoséSánchez-Muñoz, LuisMontefalco de Lira Santos, Lauro CézarSerra Branca amazonite pegmatiteAnorogenic pegmatiteTwin evolutionSpectroscopyGeochemistryThe Serra Branca pegmatite in northeastern Brazil is unique because of its megacrysts of bluish-green amazonite currently exploited for ornamental purposes and as high-quality gemstones. Here we analyze microtextural, spectroscopic, and geochemical data on specimens from two magmatic generations of amazonite from this pegmatite in order to characterize their mineralogy and propose a schematic evolution diagram for twinning during their development. The amazonite consists of intergrowths of the low microcline and low albite XRD varieties that evolved according to a twin coarsening process, in which the first generation (I-tg) of ± A/P twinning developed at the monoclinic-triclinic transformation, whereas the second generation (II-tg) gave rise mainly to ± A twins. The bluish-green color of the amazonite was preserved during the process of microcline twinning. In addition to the irrational II-tg twinning, which is typically found in microcline from anorogenic settings, the serra branca amazonite crystals also show elevated contents of Rb, Pb, Fe, Cs, and Tl in both generations, whereas albitic intergrowths present high concentrations of Fe, Pb, Sr, and Ga. Finally, our chemical and spectroscopic results are compatible with the hypothesis that Pb-water centers account for the bluish green color in amazonite.We thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for the scholarship granted to Glenda Lira Santos, Igor Manoel Belo de Albuquerque e Souza, and José Ferreira de Araújo Neto during this research.Peer reviewedSociedade Brasileira de GeologiaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil)Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]202320232022info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Publisher's versioninfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/10261/286821reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Ingléshttps://doi.org/10.1590/2317-4889202220210072Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/2868212026-05-22T06:33:51Z
dc.title.none.fl_str_mv Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
title Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
spellingShingle Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
Lira Santos, Glenda
Serra Branca amazonite pegmatite
Anorogenic pegmatite
Twin evolution
Spectroscopy
Geochemistry
title_short Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
title_full Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
title_fullStr Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
title_full_unstemmed Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
title_sort Microtextural, spectroscopic, and chemical characterization of amazonite from the Serra Branca Pegmatite, Northeastern Brazil
dc.creator.none.fl_str_mv Lira Santos, Glenda
de Brito Barreto, Sandra
Belo de Albuquerque e Souza, Igor Manoel
Ferreira de Araújo Neto, José
Sánchez-Muñoz, Luis
Montefalco de Lira Santos, Lauro Cézar
author Lira Santos, Glenda
author_facet Lira Santos, Glenda
de Brito Barreto, Sandra
Belo de Albuquerque e Souza, Igor Manoel
Ferreira de Araújo Neto, José
Sánchez-Muñoz, Luis
Montefalco de Lira Santos, Lauro Cézar
author_role author
author2 de Brito Barreto, Sandra
Belo de Albuquerque e Souza, Igor Manoel
Ferreira de Araújo Neto, José
Sánchez-Muñoz, Luis
Montefalco de Lira Santos, Lauro Cézar
author2_role author
author
author
author
author
dc.contributor.none.fl_str_mv Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil)
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Serra Branca amazonite pegmatite
Anorogenic pegmatite
Twin evolution
Spectroscopy
Geochemistry
topic Serra Branca amazonite pegmatite
Anorogenic pegmatite
Twin evolution
Spectroscopy
Geochemistry
description The Serra Branca pegmatite in northeastern Brazil is unique because of its megacrysts of bluish-green amazonite currently exploited for ornamental purposes and as high-quality gemstones. Here we analyze microtextural, spectroscopic, and geochemical data on specimens from two magmatic generations of amazonite from this pegmatite in order to characterize their mineralogy and propose a schematic evolution diagram for twinning during their development. The amazonite consists of intergrowths of the low microcline and low albite XRD varieties that evolved according to a twin coarsening process, in which the first generation (I-tg) of ± A/P twinning developed at the monoclinic-triclinic transformation, whereas the second generation (II-tg) gave rise mainly to ± A twins. The bluish-green color of the amazonite was preserved during the process of microcline twinning. In addition to the irrational II-tg twinning, which is typically found in microcline from anorogenic settings, the serra branca amazonite crystals also show elevated contents of Rb, Pb, Fe, Cs, and Tl in both generations, whereas albitic intergrowths present high concentrations of Fe, Pb, Sr, and Ga. Finally, our chemical and spectroscopic results are compatible with the hypothesis that Pb-water centers account for the bluish green color in amazonite.
publishDate 2022
dc.date.none.fl_str_mv 2022
2023
2023
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
Publisher's version
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/286821
url http://hdl.handle.net/10261/286821
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv https://doi.org/10.1590/2317-4889202220210072
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
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 reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15.81155

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