Norberto Dani
Universidade Federal do Rio Grande do Sul
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Norberto Dani.
Anais Da Academia Brasileira De Ciencias | 2007
Marisa Terezinha Garcia de Oliveira; Sandra Maria de Arruda Furtado; Milton Luiz Laquintinie Formoso; Richard A. Eggleton; Norberto Dani
Kaolin at Campo Alegre Basin, Santa Catarina State, Brazil was formed from alteration of volcanic acid rocks. Halloysite clays dominate the clay fraction of the matrix of the kaolin body, whereas a poorly crystalline kaolinite is abundant in veins. Some primary blocky structures have high amounts of illite, in one mine, but in general, only low contents of illite-smectite, illite, chlorite-vermiculite, vermiculite and quartz were identified in the clay fraction of the samples. Toward the top of the mines, hematite and lepidocrocite appear in horizontal red and ochre colored levels and the amount of kaolinite increases compared to halloysite. The vertical zoning of alteration levels, the changes in mineralogy, the positive correlation between depth and Cation Exchange Capacity of the clays, the preservation of different types of rock textures in the kaolin bodies, the dominant tube morphology of the halloysite clays indicate a supergene genesis for the deposits. Criteria to distinguish between supergene and hypogene kaolin are discussed. Transmission Electron Microscopy of the cross sections of halloysite tubes showed polygonal forms that are ascribed to be transitional between kaolinite and halloysite. It is proposed that some of the kaolinite of these deposits be inherited from the dehydration of halloysite tubes.
Clay Minerals | 2008
J. De Bona; Norberto Dani; João Marcelo Ketzer; L. F. De Ros
Abstract Fluvial and aeolian sandstones of the Sergi Formation are the most important reservoirs of the Recôncavo Basin, Brazil. Optical and scanning electron microscopy, X-ray diffraction and infrared spectroscopy revealed the occurrence of dickite, a clay mineral indicative of deep burial conditions (T >100ºC), in the shallow Buracica (630−870 m) and Água Grande (1300−1530 m) oilfields. Vermicular dickite replaces K-feldspar and plagioclase grains, and fills intra- and inter-granular pores. Its vermicular habit is a product of pseudomorphic kaolinite transformation during burial. The presence of dickite is in accordance with the intensity of compaction, post-compactional quartz cementation and δ18 O values of calcite cements (T up to 109ºC). These petrological features of deep burial, as well as apatite fission-track analyses, indicate that uplift and erosion of at least 1 km, and probably >1500 m, affected the central part of the Recôncavo Basin and possibly the entire region. This uplift has not been detected previously by conventional structural and stratigraphic models.
Anais Da Academia Brasileira De Ciencias | 2005
Andre Sampaio Mexias; Gilles Berger; Marcia Elisa Boscato Gomes; Milton Luiz Laquintinie Formoso; Norberto Dani; José Carlos Frantz; Everton Marques Bongiolo
A geochemical modeling of gold deposition was performed using the EQ3/EQ6 software package using conditions inferred from geological, petrographic, geochemical and fluid inclusion data from the Bloco do Butiá gold mine, Lavras do Sul, RS. Gold in the mine occurs only in the pyrite structure (invisible gold). The pyrite occurs associated with white mica (phengite) in the zone of phyllic alteration. The process of gold deposition showed to be related to temperature and pH decrease. The pH decrease was fundamental to gold deposition by destabilization of sulfur species [Au(HS)2- , HAu(HS)2(0) and Au(HS)0] dissolved in the aqueous solution, being Au(HS)0 the main gold transporting complex. The addition of KCl is hard to accept as cause of gold precipitation because no Cl- was detected in phengite. However, the geochemical mass balance calculation resulted in the gain of some potassium in the zone of phyllic alteration. The precipitation of pyrite (+/- auriferous) may have been strongly influenced by iron availability resulting from dissolution of ferrous chlorites by the fluids responsible for phengite deposition. The low salinity in quartz grain fluid inclusions from the propylitized wall rock also indicates the little importance of chlorine as gold transporting agent. Sulfur, and not chlorine, compounds must have dominated the gold transporting complexes in the Bloco do Butiá gold area.
Clays and Clay Minerals | 2001
Norberto Dani; Milton Luiz Laquintinie Formoso; Alain Decarreau; Alain Meunier
Nordstrandite from Lages represents the first occurrence of this mineral in an oxisoil that does not involve the influence of a calcareous substrate. This is also the first reported occurrence in Brazil. Nordstrandite occurs near the city of Lages only in the weathered bedrock facies, mostly where the circulation of meteoric water is restricted. There is also a close association between nordstrandite and the weathering of modified pseudoleucite structures. The interaction of meteoric water and feldspathic alkaline country rock with uncommon texture and mineralogy (rich in nepheline, sodalite, nosean, analcime and natrolite) promotes the development of solutions enriched in alkaline ions with basic pH, necessary to form nordstrandite. A detailed study by X-ray diffraction (XRD) and infrared (IR) spectroscopy in natural or chemically leached samples was performed to identify the Al(OH)3 polymorphs of gibbsite and nordstrandite.
Geologia USP. Série Científica | 2014
Thamy Lara de Souza; Marcus Vinicius Dorneles Remus; Norberto Dani
This work investigates the processes controlling the mobility and concentration of nickel in serpentinized ultramafic rocks of the Sul-Riograndense Shield (ESrg). Four ultramafic units were selected: Serrinha Complex, Cerro Mantiqueira Sequence, Pedras Pretas Massive and Cambaizinho Complex. Conventional techniques allow to chemically classify the rocks and to relate rock texture with the intensity and degree of the different events that contributed to changes in the mineralogy of the protholiths. Electron microprobe analysis of olivine and serpentine allowed determining the concentrations of nickel and its variations in all of the investigated units. The nickel-bearing minerals were identified, and established the relationship between geological events, element mobility and element concentration. The olivine of Pedras Pretas Massive contain lower levels of nickel with a range of 0.08 to 0.29%, and an average value of 0.17%, while olivines of Cerro Mantiqueiras Sequence contain higher NiO levels (maximum 0,44%), with an average value of 0.35%. The olivine composition of Pedras Pretas Massive and Cerro Mantiqueiras Sequence are homogeneous, while those of Cambaizinho Complex have a slightly higher range of variation with composition ranging between Fo92 and Fo84, but with NiO amounts between 0.17 e 0.30%. In Serrinha Complex, the olivine was not identified probably due to the intense serpentinization. Cambaizinho Complex and Cerro Mantiqueiras Sequence have serpentine minerals with a tendency to higher concentrations of nickel in relation to values obtained in the olivines, but some serpentines have lower values in the last sequence. By comparing the concentrations of nickel in each ultramafic unit, the olivines of Cerro Mantiqueiras Sequence have the highest NiO values, while Pedras Pretas Massive has the lowest values among the investigated ultramafic rocks. It is important to mention that the NiO concentration in the studied ultramafic units show equivalent values when compared to the other ultramafics around the world.
Geography Department, University of Sao Paulo | 2002
Jorge Arigony Neto; Jefferson Cardia Simões; Ulisses Franz Bremer; Norberto Dani
Este trabalho descreve o uso inicial de um sistema de informacoes geograficas (SIG) para auxiliar no gerenciamento da AreaAntartica Especialmente Gerenciada (AAEG) da baia do Almirantado, exemplificado mediante os resultados preliminares obtidos. Seguindorecomendacoes do Protocolo ao Tratado Antartico sobre Protecao ao Meio Ambiente (Protocolo de Madrid), foi utilizada informacao geoespacialintegrada em SIG para demarcar os limites da AAEG. A area foi recalculada em 362 km2 (antes fora estimada em 370 km2). Combase na sobreposicao de informacoes na peninsula Keller (no norte da baia do Almirantado), foi representado espacialmente o local onde,seguindo as definicoes do Protocolo de Madrid, havia sido detectado impacto ambiental menor ou transitorio no trabalho de campo. Apossibilidade de utilizacao do SIG recem-implantado no gerenciamento ambiental da baia do Almirantado cresce a medida que surge anecessidade de escolha de areas aptas a ocupacao humana, bem como da avaliacao do impacto ambiental causado pelas atividades na area.
Archive | 2004
Jefferson Cardia Simões; Norberto Dani; Ulisses Franz Bremer; Francisco Eliseu Aquino; Jorge Arigony-Neto
Sedimentology | 2005
J. Marcelo Ketzer; L. Fernando De Ros; Norberto Dani
Brazilian Journal of Geology | 2000
Sergio Rebello Dillenburg; Luciano Laybauer; Andre Sampaio Mexias; Norberto Dani; Eduardo Guimarães Barbosa; Claudio Netto Lummertz
Brazilian Journal of Geology | 2008
Marcus Vinicius Dorneles Remus; Rogério Schiffer de Souza; José Antônio Cupertino; Luiz Fernando De Ros; Norberto Dani; Maria Lidia Vignol-Lelarge
Collaboration
Dive into the Norberto Dani's collaboration.
Marcus Vinicius Dorneles Remus
Universidade Federal do Rio Grande do Sul
View shared research outputsMilton Luiz Laquintinie Formoso
Universidade Federal do Rio Grande do Sul
View shared research outputs