PETROCHEMISTRY OF AN UPPER PRECAMBRIAN METASEDIMENTARY BELT IN SOUTHERN BAHIA - THE SIGNIFICANCE OF CORDIERITE
PETROCHEMISTRY OF AN UPPER PRECAMBRIAN METASEDIMENTARY BELT IN SOUTHERN BAHIA - THE SIGNIFICANCE OF CORDIERITE
| dc.contributor | en-US | |
| dc.contributor | pt-BR | |
| dc.creator | SICHINOLFI, GIAN PAOLO | |
| dc.creator | GORGONI, CARLO | |
| dc.creator | SILVA FILHO, MARINHO ALVES DA | |
| dc.creator | OLIVEIRA, MARIA ALBA TANNER DE | |
| dc.date | 2018-08-22 | |
| dc.date.accessioned | 2023-06-19T15:37:18Z | |
| dc.date.available | 2023-06-19T15:37:18Z | |
| dc.identifier | https://ppegeo.igc.usp.br/index.php/rbg/article/view/12378 | |
| dc.identifier.uri | https://repositorioslatinoamericanos.uchile.cl/handle/2250/6693087 | |
| dc.description | Petrology and chemistry of an Upper Precambrian metasedimentary belt in Southern Bahia (Brazil) have been studied. The Belt consists essentially of muscovite-biotite gneisses and of sillimanite-grade rocks (kinzigites) containing lenses of acid-and sub-acid granulites, and pluton-like bodies of migmatitic-granitic rocks. Cordierite-bearing rocks are widely spread within the sillimanite-grade rocks. Cordierite appears always as the last paragenetic mineral and probably is formed through the reaction sillimanite+garnet+quartz = cordierite. Chemical data indicate that the original material for mica gneisses and sillimanite-grade rocks consisted of a misture of graywaekes and pelitic rocks. Comparison with modern pelagic sediments reveals low contents of metals (Fe, Mn, Ni, etc.), relatively mobile in marine environments, thus suggesting possible submarine leaching. Bulk chemistry (showing low alkali and silica contets) was found to control closely cordierite formation which is considered related to the removal of fractions of anatectic silicate liquids. The more general significance of cordierite in metasediments is discussed stressing the role of the partial H20 pressure in the metamorphic fluids. The presence of even small amounts of H20-undersaturated melts strongly reduces the molar H20 fraction and favours the stabilization of cordierite. Preservation of cordierite under more hydrous conditions depends on the further development of the P-T metamorphic regime. | en-US |
| dc.description | Petrology and chemistry of an Upper Precambrian metasedimentary belt in Southern Bahia (Brazil) have been studied. The Belt consists essentially of muscovite-biotite gneisses and of sillimanite-grade rocks (kinzigites) containing lenses of acid-and sub-acid granulites, and pluton-like bodies of migmatitic-granitic rocks. Cordierite-bearing rocks are widely spread within the sillimanite-grade rocks. Cordierite appears always as the last paragenetic mineral and probably is formed through the reaction sillimanite+garnet+quartz = cordierite. Chemical data indicate that the original material for mica gneisses and sillimanite-grade rocks consisted of a misture of graywaekes and pelitic rocks. Comparison with modern pelagic sediments reveals low contents of metals (Fe, Mn, Ni, etc.), relatively mobile in marine environments, thus suggesting possible submarine leaching. Bulk chemistry (showing low alkali and silica contets) was found to control closely cordierite formation which is considered related to the removal of fractions of anatectic silicate liquids. The more general significance of cordierite in metasediments is discussed stressing the role of the partial H20 pressure in the metamorphic fluids. The presence of even small amounts of H20-undersaturated melts strongly reduces the molar H20 fraction and favours the stabilization of cordierite. Preservation of cordierite under more hydrous conditions depends on the further development of the P-T metamorphic regime. | pt-BR |
| dc.format | application/pdf | |
| dc.language | eng | |
| dc.publisher | Sociedade Brasileira de Geologia | pt-BR |
| dc.relation | https://ppegeo.igc.usp.br/index.php/rbg/article/view/12378/11938 | |
| dc.rights | Direitos autorais 2018 Revista Brasileira de Geociências | pt-BR |
| dc.source | Revista Brasileira de Geociências; v. 9, n. 4 (1979); 267-275 | en-US |
| dc.source | Revista Brasileira de Geociências; v. 9, n. 4 (1979); 267-275 | es-ES |
| dc.source | Revista Brasileira de Geociências; v. 9, n. 4 (1979); 267-275 | pt-BR |
| dc.source | 0375-7536 | |
| dc.subject | en-US | |
| dc.subject | pt-BR | |
| dc.title | PETROCHEMISTRY OF AN UPPER PRECAMBRIAN METASEDIMENTARY BELT IN SOUTHERN BAHIA - THE SIGNIFICANCE OF CORDIERITE | en-US |
| dc.title | PETROCHEMISTRY OF AN UPPER PRECAMBRIAN METASEDIMENTARY BELT IN SOUTHERN BAHIA - THE SIGNIFICANCE OF CORDIERITE | pt-BR |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | pt-BR |