FURTHER SIGNS OF AN ENRICHED MANTLE SOURCE UNDER THE NEOPROTEROZOIC ARAÇUAÍ-RIBEIRA MOBILE BELT
FURTHER SIGNS OF AN ENRICHED MANTLE SOURCE UNDER THE NEOPROTEROZOIC ARAÇUAÍ-RIBEIRA MOBILE BELT
| dc.contributor | en-US | |
| dc.contributor | pt-BR | |
| dc.creator | LUDKA, ISABEL PEREIRA | |
| dc.creator | WIEDEMANN-LEONARDOS, CRISTINA MARIA | |
| dc.date | 2017-04-13 | |
| dc.date.accessioned | 2023-06-19T15:34:53Z | |
| dc.date.available | 2023-06-19T15:34:53Z | |
| dc.identifier | https://ppegeo.igc.usp.br/index.php/rbg/article/view/10919 | |
| dc.identifier.uri | https://repositorioslatinoamericanos.uchile.cl/handle/2250/6693042 | |
| dc.description | Isolated small bodies of Neoproterozoic coronitic gabbros crop out in the states of Espírito Santo (Jacutinga and Itaoca) and Rio de Janeiro (Amparo), in the central portion of the Araçuaí-Ribeira Mobile Belt. The rocks from Jacutinga and Itaoca are mainly gabbronorites and show a wide range of modal/textural varieties recording crystal-setting processes normally found in layered intrusions. The Amparo intrusion is formed by a coronitic rock, also present as layers in Jacutinga and Itaoca. The primary mineral assemblage consists of olivine, opx, cpx, plagioclase, ilmenite, Ti-magnetite and sulphides. Coronitic overgrowths related to the olivine-plagioclase reaction form concentric rims of opx, amphibole and simplectitic amphibole-spinel around olivine cores. They are all very similar in shape and composition pointing towards similar physical-chemical crystallization conditions. Different geothermometric measurements yielded crystallization temperatures around 800°C, which are close to those calculated for primary opx-cpx pairs (800/940°C). The absence of regional deformational and metamorphic paragenesis is compatible with their intrusion into the middle/ lower crust during a late collisional phase. A long lasting cooling environment at a late magmatic stage induced the sub-solidus reactions. Low K sub-alkaline signatures with clear enrichment in some incompatible elements such as Ba, Sr and LREE associated with high 87Sr/86Sr initial ratios (around 0.706-0.708) are anomalous chemical characteristics of these gabbros. Enriched mantle types (EM1, EM2 and HIMU) with high Sr-initial ratios are frequently found in the Southern Hemisphere. The chemical anomalies obtained in this study could be related to largescale phenomena, similar to the Dupal anomaly. | en-US |
| dc.description | Isolated small bodies of Neoproterozoic coronitic gabbros crop out in the states of Espírito Santo (Jacutinga and Itaoca) and Rio de Janeiro (Amparo), in the central portion of the Araçuaí-Ribeira Mobile Belt. The rocks from Jacutinga and Itaoca are mainly gabbronorites and show a wide range of modal/textural varieties recording crystal-setting processes normally found in layered intrusions. The Amparo intrusion is formed by a coronitic rock, also present as layers in Jacutinga and Itaoca. The primary mineral assemblage consists of olivine, opx, cpx, plagioclase, ilmenite, Ti-magnetite and sulphides. Coronitic overgrowths related to the olivine-plagioclase reaction form concentric rims of opx, amphibole and simplectitic amphibole-spinel around olivine cores. They are all very similar in shape and composition pointing towards similar physical-chemical crystallization conditions. Different geothermometric measurements yielded crystallization temperatures around 800°C, which are close to those calculated for primary opx-cpx pairs (800/940°C). The absence of regional deformational and metamorphic paragenesis is compatible with their intrusion into the middle/ lower crust during a late collisional phase. A long lasting cooling environment at a late magmatic stage induced the sub-solidus reactions. Low K sub-alkaline signatures with clear enrichment in some incompatible elements such as Ba, Sr and LREE associated with high 87Sr/86Sr initial ratios (around 0.706-0.708) are anomalous chemical characteristics of these gabbros. Enriched mantle types (EM1, EM2 and HIMU) with high Sr-initial ratios are frequently found in the Southern Hemisphere. The chemical anomalies obtained in this study could be related to largescale phenomena, similar to the Dupal anomaly. | 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/10919/10375 | |
| dc.rights | Direitos autorais 2017 Revista Brasileira de Geociências | pt-BR |
| dc.source | Revista Brasileira de Geociências; v. 30, n. 1 (2000); 095-098 | en-US |
| dc.source | Revista Brasileira de Geociências; v. 30, n. 1 (2000); 095-098 | es-ES |
| dc.source | Revista Brasileira de Geociências; v. 30, n. 1 (2000); 095-098 | pt-BR |
| dc.source | 0375-7536 | |
| dc.subject | Mantle geochemistry; Gabbro-norites; Olivine coronas. | en-US |
| dc.subject | Mantle geochemistry; Gabbro-norites; Olivine coronas. | pt-BR |
| dc.title | FURTHER SIGNS OF AN ENRICHED MANTLE SOURCE UNDER THE NEOPROTEROZOIC ARAÇUAÍ-RIBEIRA MOBILE BELT | en-US |
| dc.title | FURTHER SIGNS OF AN ENRICHED MANTLE SOURCE UNDER THE NEOPROTEROZOIC ARAÇUAÍ-RIBEIRA MOBILE BELT | pt-BR |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | pt-BR |