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Mémoire de Maîtrise
DOI
10.11606/D.44.1993.tde-28082015-143236
Document
Auteur
Nom complet
Rosely Aparecida Liguori Imbernon
Adresse Mail
Unité de l'USP
Domain de Connaissance
Date de Soutenance
Editeur
São Paulo, 1993
Directeur
Jury
Oliveira, Sonia Maria Barros de (Président)
Granato, Celso Henrique Fernandez
Toledo, Maria Cristina Motta de
Titre en portugais
Evolução geoquímica e mineralógica dos produtos de alteração intempérica sobre as rochas do complexo alcalino-carbonatítico de Catalão I, Goiás
Mots-clés en portugais
Geoquímica
Resumé en portugais
O Complexo Alcalino-Carbonatítico de Catalão I situa-se no estado de Goiás, a aproximadamente 280 km ao sul de Brasília. Constitui-se num corpo semi-circular com cerca de 6 km de diâmetro. Compõe, juntamente com os complexos de Araxá, Catalão II, Salitre I e II e Tapira, um grupo de complexos alcalinos pertencentes à província do Alto Paranaíba, que intrudiram em metassedimentos proterozóicos do Grupo Araxá. As rochas frescas são principalmente glimmeritos cortados por veios carbonatíticos, podendo ocorrer restritos corpos de piroxenito e peridotito. Anastásio, vermiculita, minerais de terras raras, apatita e pirocloro são os principais minerais de interesse econômico relacionados à intrusão carbonatítica. A ação do intemperismo foi bastante intensa sobre o complexo. O relevo do maciço foi mantido graças à resistência das rochas quartzíticas fenitizadas que o circundam, o que permitiu o aprofundamento dos perfis de alteração que podem chegar a mais de 100 metros de espessura no centro do complexo. É um processo tipicamente laterítico que gerou concentrações residuais de apatita e pirocloro nos níveis intermediários do perfil de alteração. Esses minérios são atualmente explorados. Os ETR foram concentrados pelo hidrotermalismo, constituido por materiais silicificados ricos em monazita. Também o intemperismo concentrou esses elementos na forma de fosfatos aluminosos secundários do grupo da plumbogumita e florencita. A intensa silicificação observada no complexo é em sua grande parte de origem hidrotermal. Ocorre, localizadamente, silicificação intempérica em certos horizontes do perfil de alteração.
Titre en anglais
Not available.
Mots-clés en anglais
Not available.
Resumé en anglais
The Alkaline-Carbonatie Complex of Catalão I is located in the state of Goiás, approximately 280 km south of Brasília. Together with the Araxá, Catalão II, Salitre I and II, and Tapira alkaline complexes within the Alto Paranaíba alkaline province. Catalão I is a semi-circular body 6 km in diameter which intruded Proterozoic metasediments of the Araxá Group in the Cretaceous. Principal rock types are glimmerites cut by carbonatites veins. Restricted bodies of pyroxenite and peridotite may also occur. Anatase, vermiculite, REE-bearing minerals, apatite, and pyrochlore are the main minerals of economic interest related to this carbonatitic intrusion. Although intensely weathered, the complex is dome-shaped, its relief sustained by the resistence of the surrounding, fenitized quartzitc rocks, which also permited weathering profiles to reach more than 100 meters in depth. Typical lateritic processes generated residual concentrations of apatite and pyrochlore at intermediate levels of the weathering profile. These are presently being exploited. Rare earth elements are concentraded in monazite in hydrothermally silicified horizons and in secondary aluminous phosphates of the plumbogummite and florencite groups by weathering. Most of the silicification observed in the complex is of hydrothermal origin. Weathering silicification occurs locally in alternation levels. It's a semi-circular body with 6 km of diameter. Put together with the Araxá, Catalão II, Salitre I and II and Tapira complexes, a group of alkalin complexes wich belong to Alto Paranaíba province, wich intruded in proterozoics metassediments of the Araxá Group. The fresh rocks are essentialy glimmerites crossed by carbonitites veins, piroxenites and peridotites restricted bodies may also occur. Anatase, vermiculite, REE bearing minerals, apatite and piroclore, are the main minerals of economic interest related to carbonatitic intrusion. The weathering action was intensive over the complex and the massive relief was sustained by the resistence of the fenitized quartzitcs rocks wich surround it, what permited the deepening of the weathering profiles wich can reach more than 100 meters of thickness in the complex centre. It's a typical lateritic process wich generate residual concentrations of apatite and piroclore in the intermediary levels of the weathering profile, wich constitute natural deposits and are presently explorated. Minerals bearing REE are concentrated with monazite, associated at silicified horizons, and secoundaries aluminous phosphates of the plumbogumite and florencitew group. The great silicification observed in the complex is mostly of hydrothermal origin. Weathering silicification occurs locally in alternation levels.
 
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2015-08-31
 
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