Adalene Moreira Silva

Mapeamento de óxidos de ferro usando imagens Landsat-8/OLI e EO-1/Hyperion nos depósitos ferríferos da Serra Norte, Província Mineral de Carajás, Brasil

Mapping methods for iron oxides and clay minerals, using Landsat-8/Operational Land Imager (OLI) and Earth Observing 1 (EO-1)/Hyperion imagery integrated with airborne geophysical data, were applied in the N4, N5, and N4WS iron deposits, Serra Norte, Carajas, Brazil. Band ratios were achieved on Landsat-8/OLI imagery, allowing the recognition of the main minerals from iron deposits. The Landsat-8/OLI imagery showed a robust performance for iron oxide exploration, even in vegetated shrub areas. Feature extraction and Spectral Angle Mapper hyperspectral classification methods were carried out on EO-1/Hyperion imagery with good results for mapping high-grade iron ore, the hematite-goethite ratio, and clay minerals from regolith. The EO-1/Hyperion imagery proved an excellent tool for fast remote mineral mapping in open-pit areas, as well as mapping waste and tailing disposal facilities. An unsupervised classification was carried out on a data set consisting of EO-1/Hyperion visible near-infrared 74 bands, Landsat-8/OLI-derived Normalized Difference Vegetation Index, Laser Imaging Detection and Ranging-derived Digital Terrain Model, and high-resolution airborne geophysical data (gamma ray spectrometry, Tzz component of gradiometric gravimetry data). This multisource classification proved to be an adequate alternative for mapping iron oxides in vegetated shrub areas and to enhance the geology of the regolith and mineralized areas.Manuscript ID: 20160023. Received in: 02/01/2016. Approved in: 06/13/2016. ABSTRACT: Mapping methods for iron oxides and clay minerals, using Landsat-8/Operational Land Imager (OLI) and Earth Observing 1 (EO-1)/Hyperion imagery integrated with airborne geophysical data, were applied in the N4, N5, and N4WS iron deposits, Serra Norte, Carajás, Brazil. Band ratios were achieved on Landsat-8/ OLI imagery, allowing the recognition of the main minerals from iron deposits. The Landsat-8/OLI imagery showed a robust performance for iron oxide exploration, even in vegetated shrub areas. Feature extraction and Spectral Angle Mapper hyperspectral classification methods were carried out on EO-1/Hyperion imagery with good results for mapping high-grade iron ore, the hematite-goethite ratio, and clay minerals from regolith. The EO-1/Hyperion imagery proved an excellent tool for fast remote mineral mapping in openpit areas, as well as mapping waste and tailing disposal facilities. An unsupervised classification was carried out on a data set consisting of EO-1/Hyperion visible near-infrared 74 bands, Landsat-8/OLIderived Normalized Difference Vegetation Index, Laser Imaging Detection and Ranging-derived Digital Terrain Model, and high-resolution airborne geophysical data (gamma ray spectrometry, Tzz component of gradiometric gravimetry data). This multisource classification proved to be an adequate alternative for mapping iron oxides in vegetated shrub areas and to enhance the geology of the regolith and mineralized areas.

Data-driven modeling for groundwater exploration in fractured crystalline terrain, northeast Brazil

It is not possible, using numerical methods, to model groundwater flow and transport in the fractured crystalline rock of northeastern Brazil. As an alternative, the usefulness of self-organizing map (SOM), k-means clustering, and Davies-Bouldin techniques to conceptualize the hydrogeology was evaluated. Also estimated was the well yield and groundwater quality across the Juá region. This process relies on relations in the underlying multivariate density function associated with a sparse local set of hydrogeologic (electrical conductivity, geology, temperature, and well yield) and a complete regional set of airborne geophysical (electromagnetic, magnetic, and radiometric) and satellite spectrometric measurements. Resampling of the regional well yield and electrical conductivity estimates provides sufficient resolution to construct variograms for stochastic modeling of the hydrogeologic variables. The combination of these stochastic maps provides a way to identify potential drilling targets for future groundwater development. The data-driven estimation approach, when applied to available airborne electromagnetic and water-well hydrogeologic measurements, provides a low-cost alternative to numerical groundwater flow modeling. In addition to fractured rock environments, the alternative modeling framework can provide spatial parameter estimates and associated variograms for constraints to improve the traditional calibration of equivalent groundwater-porous-media models.RésuméIl n’est pas possible, en utilisant les méthodes numériques, de modéliser écoulements et transferts souterrains dans le massif cristallin fracturé du Nord-Est du Brésil. Comme solution de remplacement, on a évalué l’utilité de la carte auto-adaptative (CAA), regroupement selon les k-moyennes, et celle des techniques de Davies-Bouldin de conceptualisation de l’hydrogéologie. Ont été également estimés le débit des puits et la qualité de l’eau sur la région de Juá. Cette méthode est basée sur les relations à l’intérieur de la fonction de densité des multi variables sous-jacentes, associées à une série locale de données hydrogéologiques (conductivité électrique, géologie, température et production des puits) dispersées et un ensemble régional complet de mesures de géophysique aéroportée (électromagnétiques, magnétiques et radiométriques) et de spectrométrie par satellite. Le ré-échantillonnage du rendement des puits de la région et des estimations de conductivité électrique est assez précis pour construire des variogrammes en vue d’une modélisation stochastique des paramètres hydrogéologiques. La combinaison de ces cartes stochastiques livre un moyen d’identification des cibles potentielles de foration en vue du développement futur des eaux souterraines. L’approche par estimation sous pilotage des données, quand elle est appliquée aux mesures disponibles d’électromagnétisme aéroporté et d’hydrogéologie des puits, offre une alternative à bas coût à la modélisation numérique de l’écoulement souterrain. Au-delà des milieux rocheux fracturés, le cadre du modèle alternatif peut fournir une estimation spatiale des paramètres et des variogrammes des contraintes associées afin d’améliorer le calage classique des modèles équivalents de milieux poreux aquifères.ResumenNo es posible, usando métodos numéricos modelar el flujo y transporte de agua subterránea en las rocas cristalinas fracturadas del noreste de Brasil. Como alternativa se evaluó la utilidad de mapas autoorganizados (SOM), agrupamiento de las k medias y técnicas de Davies-Bouldin para conceptualizar la hidrogeología. También se estimó el rendimiento de los pozos y la calidad del agua subterránea a través de la región Juá. Este proceso depende de las relaciones en la función multivariada de densidad subyacente asociada con un conjunto local disperso de datos hidrogeológicos (conductividad eléctrica, geología, temperatura, y rendimiento de pozos) y un conjunto completo regional de mediciones de la geofísica aérea (electromagnéticas, magnéticas y radiométricas) y mediciones espectrométricas satelitales. El remuestreado del rendimiento regional de pozos y las estimaciones de conductividad eléctrica proporciona una suficiente resolución para construir variogramas para el modelado estocástico de las variables hidrogeológicas. La combinación de estos mapas estocásticos proporciona una forma para identificar los potenciales objetivos de perforación para el futuro desarrollo de agua subterránea. El enfoque de estimación forzado por los datos empleados, cuando se aplica a las medidas electromagnéticas aéreas e hidrogeológicas de pozos de agua, proporciona una alternativa de bajo costo para el modelado numérico del flujo de aguas subterráneas. Además de los ambientes de rocas fracturadas, el esquema del modelado alternativo puede proveer la estimación de parámetros espaciales y variogramas asociados para las limitaciones para mejorar la calibración tradicional de los modelos equivalentes de agua subterránea en medios porosos.摘要在巴西东北部裂隙结晶岩带,利用数值方法模拟地下水的流动和迁移几乎是不可能的。作为一种替代方案,对利用自组织映射, k平均值聚类和Davies-Bouldin技术概念化水文地质学进行了评价。同时,对Juá区域的水井涌水量和地下水水质也进行了评价。这个过程依赖于与当地稀疏的水文地质单元(电导率,地质,温度和水井涌水量)相关联的底层多变量密度函数和区域完整的航空物探(电磁,磁和放射性测量)及卫星光谱测量的关系。对区域水井涌水量和电导率评估的重采样为建立水文地质变量随机模型的变异函数提供了足够的分辨率。这些随机网络的结合为未来地下水的开发确定潜在的钻孔目标提供了一种方法。数据驱动评估方法被应用到现有航空电磁和水井水文地质测量时,为地下水流数值模拟提供了一个低成本的替代方案。除了裂隙岩体环境外,这个替代模型的框架可以为约束条件提供空间参数评估和相关联的变异函数,进而改善对相当于地下水多孔介质模型进行校准的传统方法。ResumoNas rochas cristalinas fraturadas do nordeste do Brasil não é possível modelar o fluxo e transporte de água subterrânea usando métodos numéricos. Como alternativa, avaliou-se a aplicabilidade das técnicas de mapa auto-organizado (SOM), agrupamento k-means, e técnicas Davies-Bouldin para a concetualização da hidrogeologia. Também foram estimadas a produtividade das captações e a qualidade das águas subterrâneas em toda a região de Juá. Este processo baseia-se nas relações subjacentes da função densidade multivariada associada a um conjunto esparso de dados hidrogeológicos locais (condutividade elétrica, geologia, temperatura e produtividade), num conjunto completo de dados regionais de geofísica aérea (eletromagnética, magnética e radiométrica) e em medições espetrométricas de satélite. A reamostragem das estimativas de produtividade e condutividade elétrica fornece uma resolução que permite a construção de variogramas para a modelação estocástica das variáveis hidrogeológicas. A combinação destes mapas estocásticos proporciona um caminho para a identificação de potenciais locais de perfuração para a exploração futura de águas subterrâneas. A abordagem de estimação baseada em dados, quando aplicada a medições disponíveis de eletromagnética aérea e a dados hidrogeológicos a nível da sondagem, fornece uma alternativa de baixo custo à modelação numérica de fluxo. Além de ambientes de rochas fraturadas, este quadro alternativo de modelação pode fornecer estimativas espaciais de parâmetros e variogramas associados para criar restrições que possam servir para melhorar a calibração tradicional de modelos de fluxo em meios porosos equivalentes.

Discriminação de áreas de espesso regolito do leste do Estado do Amazonas usando estatística multivariada, algoritmo hiperespectral e modelagem de dados espaciais

Areas with deep regolith profiles are widely distributed in the Amazonian region. Research on regolith geology in Brazil has concentrated, mainly, in geochemical and mineralogical aspects and where possible utilizing these in exploration. Although airborne geophysics and spatial data integration methods are being used increasingly for mineral resource assessments, the application in regolith-dominated terrains is new. The objective of this paper is to show the potential of a systematic approach, including the use of regional gamma-ray spectrometry, digital elevation model and image digital processing techniques for the identification of deep regolith areas characterized by potential economic interest in less well explored region of the eastern portion of Amazonas State. The application of multivariate statistics techniques (Principal Components Analysis and K-means) in airborne gamma-ray data allows the individualization of regoliths in comparison to the geologic units of this region. How exploratory guide, the following patterns were observed: low values of K (easily lixivied during the weathering) and K/eU ratio; high values of eTh, eTh/K ration and medium values of eU, besides the higher altitude (plateau). Based on these images, the hyperspectral algorithm named Spectral Angle Mapper (SAM) and the boolean and fuzzy logic spatial modeling techniques were applied to produce regolith potential maps that were compared with previous geological data in 1:250.000 scale. The quantitative relationships between geophysical and altimetric datasets have shown great capability for linking geological and geophysical interpretations, indicating potential areas that can direct new ways for mineral prospecting at the study area.

Fusão de imagens altimétricas e aeromagnetométricas como ferramenta de interpretação geológica, exemplo da Província Mineral de Carajás (PA)

The Carajas Mineral Province is located in the eastern portion of the Amazonian Craton, in the Para state, north of Brazil. It comprises two main tectonic domains: Carajas and Cinzento strike-slip systems. A significant proportion of the mineral deposits and occurrences of this Province is geologically related to structures belonging to these two fault systems. This paper presents the results obtained by the interpretation of merged altimetric and magnetometric data, as an auxiliary tool for understanding the structural framework of the Carajas Fault. Satellite digital elevation data acquired by the Shuttle Radar Topographic Mission (SRTM) were used in combination with aeromagnetometric data acquired by the Brazil-Canada Geophysical Project (PGBC). A method was developed for digital processing and merging the data acquired by these two surveys, based on geophysical and remote sensing processing methods. The results obtained allowed to establish the relationship between features interpreted from the merged image, with the main geomorphologic and magnetic domains known in the region. These results demonstrate the potential of applying these methods for assessing areas with similar metallogenetic characteristics located elsewhere in Amazon, thus facilitating and guiding regional exploration programs.

Uso de dados aerogeofísicos de alta densidade para mapeamento geológico em terrenos altamente intemperizados: o estudo de caso da região de Cláudio, porção sul do Cráton São Francisco

This paper presents an alternative way for mapping in highly weathered terrains using derivative products of high-density airborne geophysical data and their integration with geological data. The new products allowed a better definition of important geological features and supported the geological mapping in 1:100.000 scale. The region of Claudio, south part of Sao Francisco Craton is comprised by Archean granite-gneissic terrains (TTG), an amphibolite unit and a supracrustal unit comprised by ultramafic rocks, amphibolites, schists, garnet-sillimanite quartzite and banded iron formation. The integrated approach incorporates the use of Ipatinga Sao Joao Del Rey airborne geophysical project and remote sensing data (Landsat-7/ Enhanced Thematic Mapper plus (ETM+)). The derivative products were grounded-checked to examine the efficiency of the magnetic and gamma-ray responses to delineate geological domains. The magnetometric maps provided information to the structural framework and about specific lithological units like mafic and ultramafic bodies, while the gamaespectrometric data brought strong insights about lithological units and boundaries. The data integration, which presents the geophysical and geomorphological characteristics of the lithological groups, shows high potential to better define geological contacts and tectonic structures in highly weathered Archean terrains.

Integração e análise de dados aerogeofísicos por meio da aplicação de técnicas de processamento digital de imagens e classificação não supervisionada: o exemplo do Greenstone Belt Rio das Velhas, quadrilátero ferrífero, MG

Poor outcrop and deep weathering characterize the Rio das Velhas Greenstone Belt in the southeastern from Brazil. This paper summarizes the use of high-density airborne survey for mineral exploration studies based on interpretation enhancements of magnetic, radiometric and frequency domain electromagnetic data using image-processed methods and an unsupervised classification. The generated products provide new insights and an excellent tool for mapping and trace individual lithological units, improving the information content of the single geophysical channels. The geophysical images were processed using different combinations. The best product was the analytical signal amplitude and inclination integrated by IHS transformation. Information extracted from this image maps the geology and lineament patterns at both regional and local scales. The K-means technique using ten classes was also applied to the geophysical data. These results enhance the lithologies mapped by the field geologists at the 1:100.000. Also shows important host rocks and different gold mineralized geological domains. Such domains host the known gold mineralization, illustrating the utility of these techniques to improve the geological knowledge in the study area.

Análise prospectiva para ouro nas regiões Ouro Roxo-Cantagalo e Chico Torres, Província Mineral do Tapajós

Spatial modeling (fuzzy logic) was used to predict key areas for gold exploration in the Tapajos Mineral Province (Brazilian Amazon), specifically in the regions here named Ouro Roxo-Cantagalo and Chico Torres. The data used were regional airborne geophysical and SAR-R99B data. The airborne geophysical data processing allowed the generation of evidence layers for modeling approaches. The best evidences in current models were anomalous potassium, F parameter, radioelement ratios, radioelement normalization, and amplitude of the analytical signal of the magnetic anomalous field. The SAR images were used in the photointerpretation stage. In the case of regions of the Ouro Roxo-Cantagalo and Chico Torres shear zones, geophysical images and interpretations (when necessary) were used to application of fuzzy logic, and the gold locations were used to evaluate the quality of the modeling results. The main contributions of this research include the observation of potential gamma-ray spectrometry signatures, the refining interpretation of the digital data, and improving the information of the current geological maps. The prospective Ouro Roxo-Cantagalo and Chico Torres modeling results using the conceptual fuzzy logic method exemplify the generation of regional exploration models for the cartography and selection of gold potential areas. This methodology can be extended to others regions of the Tapajos Mineral Province using airborne geophysical data current available by CPRM and the SAR images of the Centro Tecnico Operacional do Sistema de Protecao da Amazonia (CENSIPAM).

As três anomalias elípticas da porção sul do Cráton São Francisco: novos alvos para a mineralização de grafita?

The southernmost part of the Sao Francisco Craton (SFC), Minas Gerais, Brazil, comprises early Archean up to late Neoproterozoic rocks. Geologic mapping in this area is limited to regional scales due to the lack of exposed bedrock. In this research, three anomalous, elliptical structures, with an extension over 10 km along main axis, were first revealed and mapped using high-resolution airborne magnetic and gamma-ray spectrometric data. The structure located at the eastern part of the area hosts the largest graphite mine in Brazil. The other two structures were entirely unknown and absent in previous maps. The merge of geophysical data and remote sensing imagery in a geographic information system provided additional support for the mapping. This successful application of airborne geophysical methods proved their usefulness in regional geologic mapping, which is of fundamental importance to the mining industry.

New approach for the study of paleofloras using geographical information systems applied to Glossopteris Flora

This paper introduces a methodology which makes possible the visualization of the spatial distribution of plant fossils and applies it to the occurrences of the Gondwana Floristic Province present on the eastern border of the Brazilian portion of the Parana Basin during the Neopaleozoic. This province was chosen due to the existence of a large number of publications referring to their occurrence, so that a meta-analysis of their distribution could be based on ample information. The first step was the construction of a composite database including geographical location, geology, and the botanical systematics of each relevant fossil. The geographical locations were then georeferenced for translation into various maps showing various aspects of the distribution of the fossils. The spatial distribution of the fossil-housing outcrops shows that these are distributed along the area of deposition studied. Although some genera persisted for long periods of time, others lasted for only short intervals. As time passed, the fossil composition underwent a gradual change from the Late Carboniferous (Itarare Group) to the Late Permian (Rio do Rasto Formation), with the number of genera represented decreasing from 45 in the Itarare Group to 11 in the Rio do Rasto Formation.

Plant debris accumulations in the Preto River Subbasin, Itanhaém, São Paulo, Brazil: Insights from geotechnology

Abstract Geophysical methods can be used to identify the frequency and spatial distribution of plant debris, as well as for the study of the development of such accumulations in recent depositional settings. Side-scan sonar and a sub-bottom profiler were used to generate acoustic images of plant macroremains along a 16.9 km stretch of the meandering course of the Preto River in the municipality of Itanhaém, São Paulo, Brazil. Numerous inclined heterolithic stratification (IHS) deposits with plant debris constitute point bars, while sand dunes mark the migration of the channel along the straighter portions of the river. A large concentration of methane gas was found associated with older organic sediments in the river. The acoustically generated results were confirmed by the analysis of cores with all data integrated into the geographic information system (GIS) environment. The present study is one of the first to apply the methods of geotechnology to taphonomic research.