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	Provedor de dados Anais da ABC (AABC) (2) Autor Beurlen,Hartmut (1) CHEMALE-JÚNIOR,FARID (1) Ferreira,Ana C.M. (1) HARTMANN,LÉO A. (1) Soares,Dwight R. (1) da-Silva,Marcelo R.R. (1) Mais... Palavra-chave Mineral chemistry (2) Borborema Pegmatitic Province (1) Cerro Mantiqueiras Ophiolite (1) Gahnite (1) Metamorphism (1) Neoproterozoic (1) Rare-element granitic pegmatites (1) Mais... Tipo do documento Info:eu-repo/semantics/article (2) Ano 2007 (1) 2003 (1) País Brazil (2) Idioma Inglês (2)		Ordenar por:  Relevância Autor Título Ano Registros recuperados: 2 Primeira ... 1 ... Última Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil Anais da ABC (AABC) HARTMANN,LÉO A.; CHEMALE-JÚNIOR,FARID. Valuable information is retrieved from the integrated investigation of the field relationships, microstructure and mineral compositions of harzburgites from the Neoproterozoic Cerro Mantiqueiras Ophiolite. This important tectonic marker of the geological evolution of southernmost Brazilian Shield was thoroughly serpentinized during progressive metamorphism, because the oldest mineral assemblage is: olivine + orthopyroxene + tremolite + chlorite + chromite. This M1 was stabilized in mid amphibolite facies - 550-600ºC as calculated from mineral equilibria. No microstructural (e.g. ductile deformation of olivine or chromite) or compositional (e.g. mantle spinel) remnant of mantle history was identified. A metamorphic event M2 occurred in the low amphibolite... Tipo: Info:eu-repo/semantics/article Palavras-chave: Mineral chemistry; Cerro Mantiqueiras Ophiolite; Metamorphism; Neoproterozoic. Ano: 2003 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652003000100012 Chemical composition of gahnite and degree of pegmatitic fractionation in the Borborema Pegmatitic Province, northeastern Brazil Anais da ABC (AABC) Soares,Dwight R.; Beurlen,Hartmut; Ferreira,Ana C.M.; da-Silva,Marcelo R.R.. Gahnite electron probe microanalyses from three pegmatites (Mirador, Capoeira and Quintos) of the Borborema Pegmatitic Province in northeastern Brazil allowed to determine molar compositions ranging from 86.22 to 95.41 mol% gahnite (ZnAl2O4), 1.51 to 6.62 mol% hercynite (Fe2+Al2O4), 0.11 to 5.89 mol% spinel (MgAl2O4), 1.48 to 2.74 mol% galaxite (MnAl2O4), and Zn/FeTotal atomic ratios ranging from 11.53 to 60.87. These data compared with gahnite compositions from albite subtype pegmatites from Cap de Creus, Spain (Zn/FeTotal between 10 and 60) and from the source granite of the Separation Rapids pegmatite field, Ontario, Canada (Zn/FeTotal =3.5) indicate a high degree of fractionation of the studied pegmatites. This interpretation agrees with conclusions... Tipo: Info:eu-repo/semantics/article Palavras-chave: Gahnite; Rare-element granitic pegmatites; Borborema Pegmatitic Province; Mineral chemistry. Ano: 2007 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000300005 Registros recuperados: 2 Primeira ... 1 ... Última

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