Proterozoic
Mostrando 1-12 de 39 artigos, teses e dissertações.
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1. Geochronological systematics of the Huayna Potosí, Zongo and Taquesi plutons, Cordillera Real of Bolivia, by the K/Ar, Rb/Sr and U/Pb methods
Abstract The Huayna Potosi, Zongo and Taquesi are Triassic plutons located at the core of the Real Cordillera of Bolivia. In this paper, several Rb-Sr and K-Ar ages obtained in the past at the São Paulo Geochronology Laboratory, yet unpublished, will be presented, along with newer U-Pb Sensitive High-Resolution Ion Microprobe (SHRIMP) determinations made in
Braz. J. Geol.. Publicado em: 01/07/2019
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2. Cretaceous carbonatites of the southeastern Brazilian Platform: a review
ABSTRACT: This paper reviews general aspects of alkaline-carbonatitic rocks of Brazilian, Paraguayan and Bolivian terrains. Although 30 such occurrences are known in literature, only the major ones have been thoroughly investigated. The carbonatites are of Cretaceous age, with two well-defined Lower Cretaceous and Upper Cretaceous generation episodes. A clea
Braz. J. Geol.. Publicado em: 2018-06
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3. Survey and study of graphite occurrences in the Aracoiába-Baturité graphite bearing District, CE / Levantamento e estudo das ocorrências de grafita do Distrito Grafitífero Aracoiába-Baturité, CE
The Aracoiába-Baturité Graphite-bearing District has graphitic gneiss deposits (disseminated ore) and vein (solid ore) with different genetic origins and their own physical characteristics and geological environments. The graphite gneiss ore is of sedimentary, syngenetic origin, with 1.5% to 8% C content, which is distributed along two long parallel belts,
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 23/03/2011
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4. Micropaleontolgy applied to the stratigraphic and paleoclimatic interpretation of the transition between the Paranoá Group and São Francisco Supergroup (Neoproterozoic, Cabeceiras, Goiás) / Micropaleontologia aplicada na interpretação estratigráfica e paleoclimática da transição entre o Grupo Paranoá e o Supergrupo São Francisco (Neoproterozóico, Cabeceiras, GO)
The Proterozoic record of the Fazenda Funil, near Cabeceiras, GO, includes three sedimentary units: carbonate at the top of Paranoá Group, diamictite of the Jequitaí Formation, and a succession of shale, marl-shale rhythmites, and carbonate of the Sete Lagoas Formation. Microfossiliferous chert occurs in these three units in the form of lenses in the Paran
Publicado em: 2010
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5. GEOLOGIA ESTRUTURAL DO SUPERGRUPO SÃO FRANCISCO AO LONGO DA SEÇÃO REGIONAL COROMANDEL - TRÊS MARIAS CONSELHEIRO MATA, MG
The São Francisco Supergroup is an Upper Proterozoic Sedimentary sequence deposited over the São Francisco Graton and, less frequently, over instable marginal areas, where the Brazilian fold belts developed later. Due to situation, the São Francisco Supergroup is strongly deformed by the Brazilian Cycle in the margins of the basin (São Francisco Basin),
Publicado em: 2009
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6. Petrography and mineral chemisty from Indaiá I and Indaiá II intrusions, western Minas Gerais State / Petrografia e química mineral das intrusões Indaiá I e Indaiá II, oeste do Estado de Minas Gerais
An integrated petrographic and mineral chemistry study has been carried out on ultramafic, potassic to ultrapotassic and silica-undersaturated rocks of kimberlitic affinity of the Indaiá I and Indaiá II intrusions, Western Minas Gerais State, Brazil. These rocks outcrop at the Alto Paranaíba Igneous Province (PIAP), within a N30W-trending, elongated area,
Publicado em: 2008
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7. Datação química U-Th-Pb de minerais dos albitidos uraniferos da região de Lagoa Real (BA) por microssonda eletrônica
Different works in literature have used U-Th-Pb electron microprobe analyses for the chemical dating of U-Th-Pb system closing episodes in minerals. These episodes could have either metamorphic, thermal, and weathering nature or could be related to natural fission processes. Different thorium and uranium-bearing minerals which contain radiogenic lead have be
Publicado em: 2008
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8. Cráton do São Franscisco, kimberlitos e diamantes
The São Francisco Craton is a large stable area in the eastern portion of South America. Its basement comprises Archean terrains that were reworked and amalgamated during Paleoproterozoic tectonic events and later on affected marginally by the Neoproterozoic Brasiliano orogeny, during the amalgamation of West Gondwana. In this work the geological evolution
Publicado em: 2007
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9. Produção de mapas de vulnerabilidade de solos e aqüíferos à contaminação por metais pesados para o estado de Minas Gerais / Production of soils and aquifers vulnerability maps to heavy metals contamination for the State of Minas Gerais, Brazil
The study of environmental vulnerability to chemicals nowadays is an important tool to make decisions refering to the use, occupation and management of soils and aquifers. In humid tropical systems where the weathered mantle is depth and well developed, the soil reactivity becomes more important than its permeability. In this way, it is being proposed in thi
Publicado em: 2007
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10. Geocronology, isotopic geochemistry and geochemical of the dioritic-granitic plutonism between Lavras and Conselheiro Lafaiete: implicatins to paleoproterozoic evolution of Mineiro Belt central part / Geocronologia, geoquímica isotópica e litoquímica do plutonismo diorítico-granítico entre Lavras e Conselheiro Lafaiete: implicações para a evolução paleoproterozóica da parte central do Cinturão Mineiro
The study area is located in the southern border of the São Francisco Craton, Mineiro Belt. This portion comprises part of the Sul Mineira Province. In this context occurs medium to high metamorfic grade Archean and Paleoproterozoic terrains mosaic and granite-greenstone associations. The plutonic bodies, studied in this work, make part of volumous paleopro
Publicado em: 2007
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11. As rochas alcalinas de Cananéia, litoral sul do Estado de São Paulo: estudos mineralógicos, geoquímicos e isotópicos / Alkaline rocks of Cananéia, south coast of the state of São Paulo: mineralogy, geochemistcal and isotopical studies
The alkaline occurrence of Cananéia, SE Brazil, lying in the southern part of the homonymous island, is a subcircular intrusion 1.8 km² in area (Morro de São João) and 137 m high. A small and petrographically similar satellite body (Morrete) is found in the adjacent Ilha Comprida. Geomorphologically, it belongs to the Cananéia-Iguape Coast Plain. It is
Publicado em: 2007
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12. Caracterização das rochas vulcânicas e plutônicas félsicas e intermediárias do Alvo Estrela (Cu-Au), Serra de Carajás, Pará
The Estrela Cu-Au deposit is situated in the Serra do Rabo, at the easternmost part of Carajás shear zone, at the Serra dos Carajás region. It is hosted by altered andesites and gabbros and rhyolites of the Grão Pará Group, Itacaiunas Supergroup, formed at 2.76 Ga (Sm-Nd isochronic age) cut by Paleoproterozoic porphyritic quartz diorite, orthoclase-albit
Publicado em: 2006