DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
Navegar
53 resultados
Resultados da Pesquisa
Item Ferruginous duricrusts associated with diamond occurrences in the Diamantina Plateau, south Espinhaço Range, Brazil.(2021) Milagres, Alcione Rodrigues; Oliveira, Fábio Soares de; Varajão, Angélica Fortes Drummond Chicarino; Varajão, César Augusto ChicarinoMacromorphological and micromorphological characterization of the alteration facies associated with geomorphological studies are of great importance for understanding the genesis and evolution of ferruginous duricrusts. The study of the ferruginous duricrusts in the Diamantina Plateau (Southern Espinhaço Range, Minas Gerais), a region known worldwide for hosting important diamond deposits, was based on the characterization of the faciological variations of representative alteration profiles. The morphometric indexes of the area, macromorphological description of the profiles, and sampling for micromorphological and mineralogical analyzes were carried out to assist in the understanding of the landforms. The results show that the ferruginous duricrusts occur preferentially in the plateaus and high slopes, with the Sopa-Brumadinho Formation as substrate. Two types of ferruginous duricrust have been identified. Type 1 is characterized as a platy duricrust developed from a saprolite of hematitic phyllite with a ferruginous banded structure. Type 2 is characterized by a massive duricrust typically lateritic that overlaps a nodular and mottled facies, originated from a saprolite of hematitic phyllite with a diffuse distribution of opaque minerals. This phyllite is one of the rocks that occur with the diamond host rocks in the old mines of the region. Both types of ferruginous duricrusts formed by relative accumulation evolve into fragmentary facies and the soil. Locally, in discordant contact, occurs a concretionary duricrust, characterized by an absolute iron accumulation mechanism.Item Geochemical evolution of soils developed from pyroclastic rocks of Trindade Island, South Atlantic.(2021) Mateus, Ana Carolina Campos; Varajão, Angélica Fortes Drummond Chicarino; Oliveira, Fábio Soares de; Petit, Sabine; Schaefer, Carlos Ernesto Gonçalves ReynaudThe geochemical behavior of the major, minor, trace and rare earths elements (REEs) in soil profiles from ultramafic volcanoclastic rocks of the Vulcão do Paredão and Morro Vermelho Formation from Trindade Island (TI) was analyzed in this study. Losses and gains of chemical elements were calculated through the mass balance for two profiles along the slope: one located at higher altitude (460 m) and the other at lower altitude (258 m). In all profiles, Al, Fe and Ti accumulate due to their low mobility, whereas Ca, Na, K and Mg are the most intensely leached. Soils located at lower altitude show higher K and Mg values in the surface due to the contribution of saline sprays. Leaching of the REEs from higher to the lower slope led to the enrichment of these elements, especially the light REEs, in the soil at the lowest altitude (258 m). The high altitude profile showed Ce positive anomaly due to longer exposure to weathering. The geochemical balance shows a relative enrichment of Ti, Mn, Fe, Co, Cr, Ni, V, Zr, S related to the loss of mobile elements during the soil formation process, despite the youthful nature of these volcanic rocks.Item Non-allophanic Andosols of Trindade Island, south Atlantic : a new soil order in Brazil.(2020) Mateus, Ana Carolina Campos; Varajão, Angélica Fortes Drummond Chicarino; Oliveira, Fábio Soares de; Petit, Sabine; Schaefer, Carlos Ernesto Gonçalves ReynaudThe pedological studies carried out so far in Trindade Island (TI) have obtained patchy evidences of allophane, without detailed mineralogical and micromorphological studies to confirm the occurrence of Andosols in TI. Therefore, in this study, the mineralogical, micromorphological, physical and chemical characterization of four soil profiles from Vulcão do Paredão (P1) and Morro Vermelho formations (P2, P3, and P4) were carried on the latest volcanic events in Brazil from Trindade Island (TI) with the aim of to evaluate the presence of Andosols in this oceanic island. Profiles P1 and P2 are developed on pyroclastic bombs, and show, respectively, A-Bi- C and decapitated A-C horizons, whereas P3 and P4 are developed on lapillitic and bomb pyroclasts, show A-C horizons. The soil profiles have a reddish and brownish clayey matrix, are highly friable and show a plastic consistency. Their microstructures are granular, single grain and intergrain microaggregate, in which aggregates display an undifferentiated b-fabric. The mineralogical constituents of the bulk fraction are biotite, hematite, magnetite, ilmenite, pyroxene, olivine, halloysite, goethite, anatase, and rutile. The clay fraction is marked by the presence of halloysite, ferrihydrite, and little amounts of allophane. All soils presented andic properties and can be classified as non-allophanic Andosols. In addition, micromorphological features closely resemble those reported in Andosols from other volcanic islands from elsewhere. The predominance of halloysite in the clay fraction formed by alteration of sideromelane, suggests that allophane would be an intermediate phase of this rapid transformation favored by the wet climate conditions of the highest parts of TI.Item An Upper Pleistocene macroflora indicates warm and dry climate during an interglacial in central Brazil.(2021) Follador, Gabriela Luiza Pereira Pires; Cassino, Raquel Franco; Varajão, Angélica Fortes Drummond Chicarino; Rodrigues, Jonathas de Souza BittencourtThis study is the first report of the fossil macroflora of the Paleolagoa Seca, an Upper Quaternary fossil locality of lacustrine origin in central Brazil. Here we present an analysis of well-preserved fossil leaves collected from an argillite level dated at ca. 43,000 cal yr BP and discuss the paleoclimatic implications of this record. We reconstructed paleotemperature and paleoprecipitation using Leaf Margin Analysis (LMA) and Leaf Area Analysis (LAA), respectively, and used mineralogical (XRD and IR) and palynological analyses of the fossiliferous level to assess a complete picture of the past landscape. To test the ability of LMA and LAA models available for Southern Hemisphere to correctly predict Mean Annual Temperature (MAT) and Mean Annual Precipitation (MAP) for the Paleolagoa Seca, we applied several calibration models to the leaf dataset of a modern Cerrado forest and then compared predictions with modern climate data. Six LMA calibration models presented consistent MAT results and all four LAA calibration models provided satisfactory estimations of the modern MAP. The botanical iden- tification of the fossil leaves and the pollen record indicated a mosaic of open savanna, dry forests and gallery forest around the Paleolagoa Seca. The reconstructed MAP for the Paleolagoa Seca ranged between 647 and 948 mm depending on the LAA equation, which is at least 500 mm lower than the current MAP. The recon- structed Mean Annual Temperature (MAT) ranged between 22.6 and 26.3 ◦C, indicating a higher-than-present MAT, which we relate to a combination of high summer insolation and low humidity. Comparison with other local fossil macrofloras, including from nearby localities, and with other paleoclimatic records suggests that the observed dry conditions at Paleolagoa Seca were related to interhemispheric climate forcing and to a weakening of the South American Summer Monsoon (SASM).Item Phosphatized volcanic soils of Fernando de Noronha Island, Brazil : paleoclimates and landscape evolution.(2020) Silveira, Jonas Carvalho; Oliveira, Fabio Soares; Schaefer, Carlos Ernesto Gonçalves Reynaud; Varajão, Angélica Fortes Drummond Chicarino; Varajão, Cesar Augusto Chicarino; Senra, Eduardo OsórioVolcanic oceanic islands host soils that may hold important paleo-environmental proxies, based on vegetation and faunal evidences coupled with pedological and geomorphological indicators. In this regard, the main Brazilian oceanic island of Fernando de Noronha (FNI) still lacks a deeper and more complete analysis of its climatic history and soil evolution. We select and collect representative FNI soils to interpret their chemical, physical and mineralogical properties and to explain their changing pedogenesis and geomorphic balance, aiming at revealing the environmental and landscape evolutionary history of this island. Ten soil pedons on phonolites, ankaratrites and the associated pyroclastic rocks were collected in June/2018. Six profiles were classified as Inceptisols, one as Entisol, one as Mollisol, one as Vertisol and another as the first Oxisol ever described in a Brazilian oceanic island. The pH ranged between 5.0 and 6.0 in the more developed, dystrophic and Al-saturated soils, whereas alkaline pHs were found in the eutrophic and Na-rich pedons. For the latter group, chemical and physical attributes are closely associated with the parent material composition, whereas in the former, present day soil features overprint paleoweathered regoliths and former pedogenetic processes. High concentrations of available phosphorus (P) were observed in all soils and horizons, even at depths greater than 150 cm, and P forms were detected as amorphous or poorly-crystalline phosphates (Al, Fe, Na, Ca and K). High- and low-activity clay minerals coexist, combined with gibbsite and unstable primary minerals, indicating the polygenetic nature of FNI soils. A combined pedogeomorphological analysis indicated the existence of a high paleoweathered plateau with relict soils, and erosional surfaces hosting younger soils. Results showed the succession of at least three distinct main paleoclimates since the Pliocene and a post-magmatic model for landscape evolution. The unreported, widespread and intense phosphatization of all soils and paleosurfaces is attributed to a past large population of birds nesting all over the island, corroborating old historical records of the island’s early occupation. Report the occurrence of Brazil’s first ornithogenic Oxisol with more than 500 mg/ kg of bioavailable P.Item Mineralogical and geochemical signatures of Quaternary pyroclasts alterations at the volcanic Trindade Island, South Atlantic.(2020) Mateus, Ana Carolina Campos; Varajão, Angélica Fortes Drummond Chicarino; Petit, S.; Oliveira, Fabio Soares; Schaefer, Carlos Ernesto Gonçalves ReynaudThis paper reports the composition and alteration products of pyroclasts in the Holocene Paredão volcano (pyroclast 1) and Late Quaternary Morro Vermelho Formation (pyroclasts 2 and 3) of Trindade Island, South Atlantic, Brazil using combined macromorphological, micromorphological, mineralogical and geochemical techniques. The pyroclasts 1 and 2 are interpreted as volcanic tuff breccia deposits, whereas pyroclast 3 is a lapilli deposit. They are dark gray in color with some altered reddish regions and show vesicles and amygdales structures with small greenish crystals of 2.0 mm scattered throughout the matrix. The eruptions can be regarded as Strombolian-type by producing pyroclastic deposits with coarse fragments with high vesicularity and fluidal shape that indicate magmatic degassing and fragmentation. Petrologic and XRD data revealed a mixture of biotite, goethite, ilmenite, anatase, magnetite, hematite, pyroxene, zeolites, and olivine as their main mineral components. Optical microscopy analysis confirms the vesicular and amygdaloid structures, with a hypocrys- talline texture and a pale brown stained vitreous mass classified as sideromelane, due to its basaltic composition. The sideromelane changes to a reddish brown and yellowish-brown staining material identified as palagonite, clearly indicating a hydrovolcanic eruption that occurs when the ascending magma comes into contact with water. Infrared analyses in the palagonitized regions revealed the presence of halloysite, suggesting alteration of sideromelane to tubular clay minerals. Amygdales and microfractures are partially or totally filled with zeolites, which are formed by the percolation of water that reacts with the palagonite and precipitation of chemical elements of hydrothermal fluid. Reddish dark brown iddingsite and anhedral crystals of titaniferous magnetites occur in the fractures and edges of the olivine. These crystals are also dispersed in the matrix while some of them are zoned with Cr-rich core and Cr-poor edge, suggesting a deep mantle origin of the magma. The high trace elements content can be related to clinopyroxene (diopside) that include these elements. Geochemical data show that the pyroclasts are undersaturated in silica, plotting in the ultrabasic and foidites fields on the TAS classification diagram.Item Solos e superfícies de erosão : uma contextualização da evolução da paisagem na Serra do Espinhaço Meridional (SdEM), Minas Gerais.(2020) Varajão, César Augusto Chicarino; Varajão, Angélica Fortes Drummond Chicarino; Oliveira, Fábio Soares de; Barreto, Helen Nébias; Salgado, André Augusto RodriguesO estudo investigou a evolução da paisagem da Serra do Espinhaço Meridional (SdEM), MG, através da caracterização macromorfológica, mineralógica, micromorfológica e química de solos desenvolvidos nas principais unidades lito-estratigráficas da região. Ocorrem principalmente Neossolos e Cambissolos, decapeados e cobertos discordantemente por um paleopavimento. Considerando as variações climáticas, as superfícies de erosão e as recentes datações dos solos, entendemos que após um longo período sob condições desérticas no Cretáceo (Superfície Pós-Gondwana) até o Paleoceno (Superfície Sul-Americana), ocorreu uma abrupta variação climática no Eoceno, em que condições quentes e úmidas formaram os mantos de alteração e o desmantelamento dos veios de quartzo presentes nas unidades subjacentes (Supergrupo Espinhaço). Estas condições também estiveram presentes durante o Mioceno, desaparecendo no Plioceno, onde a instalação de um novo clima desértico promoveu o desaparecimento da vegetação e a consequente erosão-decapitação dos perfis de solo. Neste contexto se formou o paleopavimento regional supracitado, interpretado como contemporâneo à Superfície Velhas. Sobre ele, durante o Quaternário, formaram-se inúmeras turfeiras, que sugerem condições climáticas regionais amenas.Item The Cenozoic deposits of the ancient landscapes of Quadrilátero Ferrífero highlands, Southeastern Brazil : sedimentation, pedogenesis and landscape evolution.(2020) Varajão, Angélica Fortes Drummond Chicarino; Mateus, Ana Carolina Campos; Santos, Maria do Carmo; Varajão, César Augusto Chicarino; Oliveira, Fabio Soares; Yvon, JacquesThe Quadrilátero Ferrífero (QF), Southeastern Brazil, is a very important tropical highland region in the world’s geological context for its large and diverse Archean and Proterozoic rocks with great reserves of gold, iron, manganese, aluminum and industrial rocks, on a apparently stable geological structure. There, Cenozoic deposits perched on highland valleys show unclear genetic relationships with the underlying bedrock, with no apparent regional correlation. We studied five representative Cenozoic deposits (BR356, Água Limpa, Padre Domingos, Pau Branco and Casa de Pedra) on the highlands of the Serra da Moeda syncline, Western QF, to answer the question of their sedimentological origin, and investigate their pedological evolution. Field sampling was complemented by macromorphological, mineralogical and micromorphological analysis supported by X-ray diffraction (XRD), differential thermal analysis (DTA), infrared analysis (IR), scanning electron microscopy (SEM), micropobre and transmission electron microscopy (TEM). The evolution of these isolated highland de- posits comprises a deep-weathered source area, a tectonic activity, besides sedimentological and pedological processes, during and after the deposition. The deposits overlie deep saprolites of Precambrian rocks (Piracicaba and Itabira Groups), representing unconformable contact. The onset of the deposition was marked by torrential, coarse colluvial and large blocks landslides into the small basins generated by reactivating tectonic events during the Oligocene, producing local grabens. These tectonic basins were filled by cohesive debris and mudflow from the adjacent and previously laterized cover, developed under the hot and humid climate in the Eocene. The cover reveals an upside-down lateritic profile where morphology and kaolinite crystal properties (values of size of coherent scattering thickness ranging from 135 Å to 162 Å) in the bottom is related to the pedolith horizons of the former lateritic cover. Later, due to climate changes (during and after the Miocene), renewed weathering on these pre-weathered sediments occurred, characterized by alternating ferruginization and Fe-losses, with the superimposed generation of new pedogenic features such as nodules, ferruginous duricrusts and mottling (redox features). In addition to demonstrating that the Brazilian platform was not stable during the Cenozoic, these deposits reveal the role of polygenetic tropical pedological processes in their formation and transformation.Item Protocolo de inventário e avaliação de Lugares de Interesse Pedológico (LIPe) para um “Pedoturismo”.(2019) Fonseca Filho, Ricardo Eustáquio; Varajão, Angélica Fortes Drummond Chicarino; Castro, Paulo de Tarso AmorimO solo é parte essencial para a vida na Terra. As Geociências, em especial a Pedologia, têm um papel fundamental no balanceamento desta relação biótica-abiótica. Neste sentido propõe-se o Pedoturismo como segmento turístico por meio da inventariação e avaliação de “Lugares de Interesse Pedológico” (LIPe) como produtos eco- e geoturísticos. Os métodos utilizados abordaram revisão de literatura; elaboração de ficha de inventário quali-quantitativa para aplicação em campo; inserção dos dados de LIPe na base de dados online do Geossit, Terra Mineira e afins; quantificação pedoturística; cálculo do potencial pedoturístico. O resultado se apresenta na forma de um novo segmento turístico, o Pedoturismo, e uma base metodológica teórica para conceituação, descrição e quantificação de geossítios de interesse pedológico (pedossítios) cujo conjunto constitui a pedodiversidade e contribui para a pedoconservação do patrimônio pedológico em unidades de conservação, geoparques e outras áreas protegidas.Item Compactação e erosão de trilhas geoturísticas de parques do quadrilátero ferrífero e da serra do espinhaço meridional.(2019) Fonseca Filho, Ricardo Eustáquio; Varajão, Angélica Fortes Drummond Chicarino; Castro, Paulo de Tarso AmorimAs trilhas e seu conteúdo, em maior parte os solos, tendem a não serem monitoradas, seja em ambientes urbanos seja natural, como as unidades de conservação. O uso público por meio do turismo em parques se utiliza das trilhas para usufruto dos atrativos, impactando a superfície (e subsuperfície) dos solos. Pretendeu-se no presente trabalho identificar os níveis de compactação e de erosão dos solos como fatores de alterações ambientais negativas nas trilhas: Pico do Itacolomi - Parque Estadual do Itacolomi, Campo Ferruginoso - Parque Estadual Serra do Rola Moça e Cachoeira da Farofa - Parque Nacional da Serra do Cipó. A metodologia incluiu teste de resistência do solo (compactação) ao penetrômetro de cone com anel dinamométrico e medição da Área Seccional Transversal (erosão). Os resultados demonstram que: o leito das trilhas é, em geral, mais resistente que as margens (áreas não pisoteadas); e há uma correlação diretamente proporcional da litologia com a compactação e a erosão (filitos>quartzitos>canga). A fragilidade dos diferentes substratos (sedimentos de aluvião; quartzitos e filitos; e canga dos campos rupestres hematíticos) somada ao pisoteio sem monitoramento pode aumentar a degradação das trilhas, sugerindo-se revisão das normas de visitação.