Abstract The inherent structural complexity of fractured aquifers, which controls the groundwater accumulation and flow in restricted zones, can lead to a high number of non-productive tube wells. The combined analysis of geomorphological features and indirect investigations like geophysics methods allows the identification of favorable targets for groundwater exploitation. This paper deals with regional and local structural surveys coupled with electrical resistivity tomography data in order to identify favorable targets for groundwater exploitation for urban consumption in a fractured granite located in Caçapava do Sul city, southern Brazil. The structural control is manifested in the regional landforms and clearly conditions the orientation of main drainages. Based on this structural control, four parallel electrical resistivity tomography lines were performed in an area of interest for groundwater exploitation, followed by the generation of 2D inversion models and pseudo 3D models. The contact between the very thin superficial soil and the underlying granite massif determines the existence of a regional free aquifer and the probable recharge of the fractured aquifer. In the 2D inversion models, abrupt variations of resistivity related to locally recognized vertical fractures in the field occur, although they do not show lateral continuity (out of plane). The analysis of the geophysical maps from 40 meters depth allows the recognition of three alignments of low resistivity (around 500 Ωm) within a granite context where high values predominate (above 15000 Ωm). These alignments show a triple fracture intersection pattern also recognized in satellite images, which are highly favorable for groundwater accumulation and exploitation.

Resumen La complejidad estructural inherente a los acuíferos fracturados, que controla la acumulación y el flujo de agua subterránea en zonas restringidas, puede dar lugar a un elevado número de pozos tubulares no productivos. El análisis combinado de las características geomorfológicas y las investigaciones indirectas, como los métodos geofísicos, permite identificar objetivos favorables para la explotación de aguas subterráneas. Este trabajo trata de los estudios estructurales regionales y locales acoplados con datos de tomografía de resistividad eléctrica con el fin de identificar objetivos favorables para la explotación de aguas subterráneas para el consumo urbano en un granito fracturado situado en la ciudad de Caçapava do Sul, en el sur de Brasil. El control estructural se manifiesta en las formas del terreno regional y condiciona claramente la orientación de los drenajes principales. Basándose en este control estructural, se realizaron cuatro líneas paralelas de tomografía de resistividad eléctrica en una zona de interés para la explotación de aguas subterráneas, seguidas de la generación de modelos de inversión 2D y de modelos pseudo 3D. El contacto entre el suelo superficial muy fino y el macizo granítico subyacente determina la existencia de un acuífero libre regional y la probable recarga del acuífero fracturado. En los modelos de inversión 2D se producen variaciones bruscas de resistividad relacionadas con las fracturas verticales localmente reconocidas en el yacimiento, aunque no muestran continuidad lateral (fuera del plano). El análisis de los mapas geofísicos a partir de 40 metros de profundidad permite reconocer tres alineaciones de baja resistividad (alrededor de 500 Ωm) dentro de un contexto granítico donde predominan los valores altos (por encima de 15000 Ωm). Estas alineaciones muestran un patrón de triple intersección de fracturas reconocido también en las imágenes de satélite, que son altamente favorables para la acumulación y explotación de aguas subterráneas.

Abstract Metal mining deeply modifies local environmental dynamics and produces large volumes of waste rock and residues, which is expected to be carefully disposed in order to prevent soil, water, and environment degradation. The Osamu Utsumi mine was a pioneer uranium ore exploitation site in Brazil, located in the State of Minas Gerais. The open pit and the high concentration of sulfide in waste rock piles are nowadays a dispendious concern to the Nuclear Industries of Brazil (INB, in Portuguese), due to sulfide oxidation and the resultant acid mine drainage (AMD). The objective of this research is to analyze the correlation between gamma-ray spectrometry data and the generation of AMD in a waste rock pile, locally known as BF-04. Potassium concentrations can be used to distinguish zones of rock depletion, lowest concentrations, and radioelement sedimentation. The radiometric data acquisition combined with previous studies indicates that high uranium and thorium concentrations are associated with high sulfide zones. The mineralized uranium ore includes sulfides that are rapidly destroyed by surface hydration conditions, responsible for generating acid mine drainage. In this sense, superficial zones in the waste rock pile with high levels of eU and eTh are areas exposed to oxidation and hydration of sulfides, and, therefore, their recognition and neutralization can contribute to decrease AMD generation in the study site and areas with similar characteristics. The gamma-ray spectrometry results can subsidize more effective and low-cost remediation techniques.

Resumen La minería de metales modifica profundamente la dinámica ambiental local y produce grandes volúmenes de roca y residuos, los cuales se espera sean eliminados cuidadosamente para evitar el deterioro del suelo, el agua y el medio ambiente. La mina Osamu Utsumi fue un sitio de explotación de mineral de uranio pionero en Brasil, ubicado en el estado de Minas Gerais. La mina abierta y la alta concentración de sulfuro en las capas de material estéril son hoy en día un tema de preocupación para las Industrias Nucleares de Brasil (INB), debido a la oxidación del sulfuro y el drenaje ácido de la mina resultante (AMD, por sus siglas en inglés). El objetivo de esta investigación es analizar los datos de espectrometría de rayos gamma y la generación de AMD en una capa de material estéril, BF-04, en el sitio. La adquisición de datos radiométricos combinada con estudios previos indica que las altas concentraciones de uranio y torio están asociadas con zonas de alto contenido de sulfuro. El mineral de uranio mineralizado incluye sulfuros que se destruyen rápidamente por las condiciones de hidratación de la superficie y son responsables de generar el drenaje ácido de la mina. En este sentido, las zonas superficiales de la capa de material estéril con altos niveles de eU y eTh son áreas expuestas a la oxidación e hidratación de sulfuros y, por lo tanto, su reconocimiento y neutralización pueden contribuir a disminuir la generación de AMD en el sitio de estudio y áreas con condiciones similares. Los resultados de la espectrometría de rayos gamma pueden ser de interés para una remediación de bajo costo en el entorno local.

RESUMO Crianças e adolescentes com deficiência física apresentam desafios motores e socioemocionais que interferem na qualidade de vida relacionada à saúde e os colocam em maior risco de desenvolver doenças secundárias. Além disso, estão mais sujeitos a restrições de serviços adequados que ofereçam terapias, principalmente para a população de baixa renda social. Torna-se necessário oferecer ações voltadas para a promoção da saúde em um sentido mais amplo, oferecendo não só meios de habilitação e reabilitação física, mas também de ganhos sociais e emocionais. Este objetivo pode ser atingido com esportes adaptados e atividades recreativas nos quais o condicionamento físico é acompanhado por ganhos em autoestima e benefícios sociais. Com a pandemia de COVID-19 e o isolamento social, crianças e adolescentes com deficiência física ficaram ainda mais privados de assistência. Relatamos aqui o esforço de uma organização não-governamental esportiva em manter o atendimento físico e psicológico por meio de consultas virtuais, e avaliamos as percepções das partes interessadas no processo. Nível de evidência IV; série de casos .

ABSTRACT Children and adolescents with physical disabilities have motor and social-emotional challenges that interfere with their health-related quality of life and put them at greater risk of developing secondary conditions. Moreover, services that provide them therapies are more likely to be restricted, especially for the low-income population. There must be broader actions towards health promotion, offering not only means for physical habilitation and rehabilitation but for social and emotional improvements as well. This goal is attainable by adaptive sports and recreational activities where physical conditioning is accompanied by an improvement in self-esteem and social benefits. With the COVID-19 pandemic and social isolation, children and adolescents with physical disabilities were even further deprived of assistance. Our aim was to report the efforts of a non-governmental sports organization in maintaining physical and psychological care through virtual consultations and to analyze the perceptions of those affected by the process. Level of evidence IV; case series .

Abstract The geophysical diagnosis of mineral deposits can be extremely useful in detailing mineralized zones and is a strategy for direct sampling by probing holes for content analysis. This study involves the combined use of Electrical geophysical methods (DC resistivity and Induced Polarization), geological recognition and structural field analysis, with a study of the mineralized occurrence of copper, previously described in a systematic geochemical survey carried out by the Geological Survey of Brazil (CPRM), located in the north of the Camaquã Basin, extreme south of Brazil. The mineral occurrence is partially outcropped and consists of quartz vein shafts with malachite and relic structures of sulfides, contained in schist. Structural data obtained in the field revealed the existence of a system of fracture pairs in the directions N40-50W and N70-80E. Such information is presented in the programming of the geophysical data acquisition scheme, which consisted of 6 lines of electrical tomography with 410m each, in azimuthal disposition and Schlumberger arrangement, where all lines cross a single center and are separated according to an angle of 30°, in an attempt to cover fractures in various orientations. The 2D results reveal the existence of high chargeability zones (>40mV/V) positioned below the 40m depth. These data were interpolated in 3D visualization models and generated resistivity and chargeability maps for several depths, which integrated with previous structural data, and indicate the existence of zones with potential sulfide concentration with strong structural control, in addition to clear target recognition for direct and objective probing evaluation, with rationalization of costs.

Abstract Airborne and ground magnetic and gravimetric maps provide important information about the spatial distribution of causative sources in the geological substrate. These sources normally have different physical properties and geometric shapes and are located at different depths, making it difficult to identify the geological features that correspond to the sources. Filtering and enhancement techniques can be used to highlight features in potential field anomalies (such as center and edges of sources). Also, these techniques remove associated noise, isolate shallow from deep sources, and estimate depths. We applied enhancement and depth estimation techniques in airborne and ground potential field data to delineate a subsurface structural framework of two copper occurrences (Victor Teixeira and Capão Grande) in the northwestern border of Camaquã Basin with the Sul-Riograndense Shield. Our results confirmed previously recognized structures and revealed an interconnected structural framework, which has an estimated depth of 170 m by Euler solutions. This configuration suggests a possible connection between the two mineralization outcrops, which are separated by a distance of 2,300 m.

Resumen Los mapas magnéticos y gravimétricos (aéreos y/o terrestres) suministran información importante sobre la distribución espacial de las fuentes del sustrato geológico, las cuales normalmente tienen propiedades físicas y geometrías diferentes. Estas fuentes también pueden estar localizadas a distintas profundidades, complicando la identificación de las correspondientes estructuras geológicas. Técnicas de filtrado y de realce de anomalías potenciales, pueden ser utilizadas para realzar ciertas características de interés (como el centro y el borde de las fuentes), para remover aquellas características asociadas a ruidos, para separar las anomalías de las fuentes superficiales y profundas, así como estimar sus profundidades. En este trabajo se analizan los resultados de la utilización de técnicas de realce y estimación de profundidad de las fuentes con datos geofísicos aéreos y terrestres potenciales, con el objetivo de delinear una imagen estructural del subsuelo en un área con dos ocurrencias de cobre en el límite noroeste, entre las rocas del Escudo Sul-Riograndense y la Cuenca del Camaquã. Los resultados confirman estructuras que han sido reconocidas previamente y revelan otras estructuras geológicas que integran una malla estructural interconectada, cuya profundidad, estimada por las soluciones de Euler, alcanzan los 170 m. Esta configuración sugiere una probable conexión entre las mineralizaciones de cobre observadas en los afloramientos, separados por un intervalo de 2,300 m.

Abstract The Precambrian metamorphic rocks in the southern region of the Espírito Santo State (southeastern Brazil) is intercepted by ductile and brittle/ductile shear zones over which towns like Guaçuí, Marechal Floriano and Domingos Martins were established. In the years of 2014 to 2016 the Espírito Santo State faced the worst drought in the past 80 years. In situations like that, the only source of fresh water available is underground. Therefore, the purpose of this study was to integrate multisource data for groundwater prospecting and management. The study area comprises the central sectors of the Guaçuí and Batatal shear zones. Methodology involved the interpretation of stereo-pairs for the identification of lineaments, electrical resistivity surveys and geological fieldwork. The results were tentatively validated with available groundwater well production data. Six resistivity profiles with a total length of 2,400 m were surveyed and 15 outcrops were described across these structures. Results have shown that the structural framework of the shear zones is predominantly made of NW to NNW and NE to NNE-trending lineaments. The former is related to brittle tectonics and the latter coincides with the ductile Precambrian fabric of the crystalline basement rocks. A near-surface porous aquifer regarded to the regolith and recent unconsolidated sedimentary deposits presenting resistivity values < 1,372 Ohm.m and depths < 30 m have good potential for groundwater storage. However, results are not conclusive about the hydrogeological significance of tectonic structures for groundwater prospection in the study area.

Resumen Las rocas metamórficas Precámbricas en la región sur del estado de Espírito Santo (sureste de Brasil) están interceptadas por zonas de cizallamiento dúctiles y quebradizas / dúctiles sobre las cuales se establecieron pueblos como Guaçuí, Marechal Floriano y Domingos Martins. En los años de 2014 a 2016, el estado de Espírito Santo enfrentó la peor sequía de los últimos 80 años. En situaciones como esa, la única fuente de agua dulce disponible es subterránea. Por lo tanto, el propósito de este estudio fue integrar datos de fuentes múltiples para la prospección y gestión de aguas subterráneas. El área de estudio comprende los sectores centrales de las zonas de cizallamiento Guaçuí y Batatal. La metodología abarca la interpretación de pares estereoscópicos para la identificación de lineamientos estructurales, prospección geofísica (resistividad eléctrica) y trabajos geológicos de campo. Los resultados se validaron tentativamente con los datos de producción de pozos de agua subterránea disponibles. Se estudiaron seis perfiles de resistividad con una longitud total de 2.400 m y se describieron 15 afloramientos. Los resultados mostraron que el marco estructural de las zonas de cizallamiento está hecho predominantemente de lineamientos de orientación NW a NNW y NE a NNE. La familia de orientación NW-NNW está relacionada con la tectónica frágil y la familia de orientación NE-NNE coincide con la trama dúctil Precámbrica de las rocas cristalinas del basamento. Un acuífero poroso superficial relacionado al regolito y a depósitos sedimentarios no consolidados recientes, con valores de resistividad < 1.372 Ohm.m y profundidades <30 m presenta un buen potencial para el almacenamiento de agua subterránea. Sin embargo, los resultados no son concluyentes sobre el significado hidrogeológico de las estructuras tectónicas para la prospección de aguas subterráneas en el área de estudio.

Abstract Usually, stability conditions of excavation slopes are evaluated by means of kinematic analysis and geomechanical classification systems. However, field surveys are concentrated at the slope toe and information about the upper and internal portions of rock masses are not taken into account. In order to tackle with these issues multisources data were integrated. The studies were carried out in a marble quarry located in one of the largest Brazilian poles of dimension stones. Results have shown that drone images actually help in the structural characterization of rock masses because they allow to classify variable degrees of fracturing and to identify structural domains in the entire slope face. In addition, the number of discontinuities interpreted from drone images was much larger than that determined by scanline survey methods. This demonstrates that the subsampling of classical survey methods may significantly affect slope stability assessment. Results have also shown that the intensive use of explosives as a method for rock dismantling was an important mechanism of fracture generation. The electrical resistivity tomography method coupled with the other survey methods employed in this work, proved an important tool for rock mass characterization and quarry exploitation, since it allowed identifying and assessing subsurface fractured zone.

Abstract The Guacuí and Batatal lineaments in the southern region of the state of Espírito Santo (southeastern Brazil) can be traced from satellite images for tens of kilometers. They are considered shear zones associated to the final tectonic stages of the Araçuaí-West Congo (A-WC) Orogen during the Ediacaran-Cambrian period. In order to understand their nature and tectonic implications for the development of the orogeny, we integrated geological and structural data based on fieldwork and detailed microstructural analysis. Data was collected along two profiles located at the central segments of both structures. The results demonstrated that the Guaçuí shear zone (GSZ) is a typical ductile transpressive shear zone with approximately 9 km width that shows numerous dextral kinematic indicators and records metamorphism of upper amphibolite facies. The GSZ shows different levels of intensity of dynamic deformation. The Batatal shear zone (BSZ) is a narrow brittle shear zone that shows essentially brittle microstructures (intercrystalline microfractures) revealing deformation at low-grade conditions (frictional regime). Based on their characteristics and the level of erosion of the rocks exposed in the region, we interpret that GSZ developed prior to BSZ.

RESUMO Necrochorume é um efluente gerado a partir da decomposição de corpos. Em cemitérios, a principal causa de poluição subsuperficial é a sua percolação, que altera significativamente o solo, impedindo-o de realizar suas funções naturais. Particularmente no Brasil, pela falta de planejamento consequente do histórico cultural, os cemitérios se localizam totalmente integrados à malha urbana, representando um problema de saúde pública. O risco de contaminação está associado à presença de elementos, como compostos nitrogenados, metais pesados, vírus e bactérias, com riscos inerentes à saúde humana. Na literatura, esses contaminantes têm sido constantemente identificados no ambiente geológico a partir de resultados analíticos de água e solo quando comparados a uma área não impactada. A presente pesquisa objetivou investigar eventuais alterações no meio físico subsuperficial do cemitério municipal da cidade de Rio Claro, São Paulo, por meio dos resultados analíticos dos poços, apoiados por dados obtidos da técnica geofísica da sondagem elétrica vertical (SEV). Os resultados apontaram boa correlação com a evolução espacial e temporal da ocupação do cemitério ao longo de sua história.

ABSTRACT Putrefative liquid is an effluent generated from the decomposition of bodies. In cemeteries, the leading cause of subsurface pollution is the liquefaction products percolation, which substantially alter the physical-chemical and biological characteristics of the soil. In Brazil, due to the lack of consistent planning due to cultural history, cemeteries are fully integrated into urban areas, which can be a public health problem. The risk of contamination is associated with the presence of elements such as nitrogen compounds, heavy metals, viruses and bacteria, with risks to human health. In the literature, these contaminants have been consistently identified in the geological environment through analytical results of water and soil compared to non affected areas. This research aimed to investigate possible changes in the subsurface physical environment of the Rio Claro city (São Paulo, Brazil) municipal cemetery, through the analytical results of the wells, supported by data obtained from the geophysical technique of vertical electrical sounding (VES). The results showed good correlation with the spatial and temporal evolution of the occupation of the cemetery throughout its history.

Abstract The dumps are areas of final disposal of solid wastes directly into the soil, with no technical criteria or collecting systems of gases or liquids. A large part of Brazilian municipalities have used this extreme damaging alternative to the environment up to the year 2010, when a federal law made compulsory the installation of sanitary landfills. However, large parts of the dumps were simply abandoned, although some eventually go through treatment after assessments of the state environmental agencies. This work presents the results of a geophysical investigation in a dump deactivated in 2004 in a small city in southern Brazil, where previous investigations have revealed contamination of soil and groundwater by leachate. Structural analyzes in the area of study combined to geological data from monitoring wells indicate the presence of contaminants in fractured granite, with a wide variation in the thickness of soil, saprolite and groundwater level. The integration of chemical analyses of the groundwater with electrical resistivity tomography (ERT) in 2D and 3D processing, revealed the existence of large contaminated areas within the limits of the dump flowing into the aquifer partially free up to 5m depth. Such areas may decrease gradually with the increase in depth and between 9m and 19m contaminated zones clearly predominate, associated with the Flow in the fractured aquifer. The indication of restricted and oriented zones suggests the targeting and accumulation of contaminants in two systems of preferential fractures. The discovery of these zones is fundamental for planning and the installation of pumping and decontamination systems of groundwater, considering a declining production of leachate since the closure of the dump.

Resumen Los basureros son zonas de depósito final de desechos sólidos directamente en el suelo, en ausencia de criterios técnicos o sistemas de recolección de gases o líquidos. Una gran parte de los municipios brasileños han utilizado esta alternativa extremadamente perjudicial para el ambiente hasta el año 2010, cuando una ley federal hizo obligatoria la instalación de rellenos sanitarios. Sin embargo, una gran parte de los basureros fueron simplemente abandonados, aunque algunos finalmente tuvieron algún tratamiento después de las evaluaciones de los organismos ambientales. Este trabajo presenta los resultados de la investigación geofísica en un basurero cerrado en 2004 en una pequeña ciudad del sur de Brasil, donde las investigaciones anteriores revelaron contaminaciones del suelo y de las aguas subterráneas por lixiviación. Los análisis estructurales en la región de estudios vinculados a datos geológicos de pozos de monitoreo indican la presencia de contaminantes en la fractura de granito, con amplias variaciones en el espesor del suelo, saprolita y el nivel del agua subterránea. La integración del análisis químico de las aguas subterráneas con los datos de la tomografía eléctrica (ERT) en el procesamiento de imágenes 2D y 3D, reveló la existencia de grandes áreas contaminadas dentro de los límites del basurero y el flujo en el acuífero parcialmente libre hasta 5m de profundidad. Estas zonas pueden disminuir gradualmente con el aumento de la profundidad y entre 9m y 19m predominan zonas contaminadas claramente orientadas, asociada con el flujo en el acuífero fracturado. La indicación de zonas restringidas y dirigidos sugiere la focalización y la acumulación de contaminantes en los dos sistemas de fracturas preferenciales. El descubrimiento de estas áreas es esencial para la planificación y la instalación de sistemas de bombeo y de descontaminación de aguas subterráneas, en vista de la disminución de la producción de lixiviado desde la clausura del basurero.

Abstract Ore mining fundamentally depends on the definition of its tenor and volume, something extremely complex in disseminated mineralization, as in the case of certain types of deposits of gold and sulfites. This article proposes the use of electrical tomography for definition of a geophysical signature in terms of electrical resistivity and chargeability, in an outcrop of mineralized quartz lode at the end of an inactive gold mine. One of the targets was to analyze the continuity of the mineralized body, the occurrence of new outcrops and the applicability of the method as an auxiliary tool in mineral extraction. Three parallel lines of electrical tomography in a dipole-dipole arrangement, being orthogonal to the orientation of the gold lode, were installed in an area outside the mine. The results allowed the geophysical characterization of the mineralized zone by high resistivity (above 1000Ω.m) and high chargeability (above 30mV/V). The results of the 2D inversion models were interpolated in 3D visualization models, which allowed definition of the contour surfaces for the physical parameters measured, and the morphological pattern modeling of the mineralization. The data reveal the existence of a new lode in subsurface, localized 30m to the south of the lode outcrop. The versatility of the acquisition and data processing indicate the application potential of electrical tomography as a criterion for sampling and tenor definition in ore extraction activities, since it is objective and low cost.

Abstract : This paper makes a comparative analysis between the Dipole-dipole, Wenner and Schlumberger arrays through electric resistivity tomography (ERT), about the sensitivity and resolution in the spatial characterization of infiltrating pollutants in septic tank and cone of depression in supply well, both contained in unconfined aquifer. Data acquisition consisted of electrical resistivity rea- dings using five parallel lines with 105m long, electrode spacing and lines of 5m. The data from each line were subjected to 2D inversion and then interpolated to generate 3D blocks, which were extracted from a fixed resistivity isosurface (620 Ω.m), which enabled the modeling of volumes related to the flow structures. The results for the Dipole-dipole array allowed the modeling of the cylindrical structure associated to the supply well, and an isosurface deformation associated to the septic tank, but did not allow the modeling of the plume. The data for the Schlumberger array cannot allow for the cone recognition, but resulted in a drop shape model, associated to the septic tank and similar to a contamination plume. The Wenner array resulted in a model with structure in elongated keel format associated to the cone of depression, and another that is similar to the drop shape model, also associated to the septic tank. The comparative analysis shows that the Dipole-dipole array is recommended in works of modeling vertically integrated three- dimensional structures of high resistivity in the saturated zone. The Wenner and Schlumberger arrays are recommended for modeling vertically integrated three-dimensional structures of low resistivity in unsaturated zone, with emphasis on the Schlumberger array.

Resumen: En este trabajo se hace un análisis comparati- vo entre los arreglos Dipolo-dipolo, Wenner e Schlumberger por medio de pruebas de Tomo- grafía de Resistividad Eléctrica (TRE), como la sensibilidad y la resolución en la caracterización espacial de la infiltración de contaminantes en un tanque séptico y cono de depresión en el pozo de captación de agua; ambos contenidos en acuífero libre. La adquisición de datos consistió en lecturas de resistividad utilizando cinco líneas paralelas con 105 m de largo espaciado, 5 m entre los electrodos y líneas. Los datos de cada línea se sometieron a la inversión 2D, posteriormente interpolado para la generación de bloques 3D, de la cual se extrajo una isosuperficie de resistividad fija (620 Ω.m), lo que permitió el modelado de las estructuras de volúmenes de flujo relacionados. Los resultados para el arreglo Dipolo-dipolo permite el modelado de la estructura asociada con el eje cilíndrico, y un isosurface de la cavidad asociada con la deformación, pero que no permitirá que el modelado de la pluma. Los datos para la disposición Schlumberger no pueden ser reconocidos cono, pero dieron lugar a un modelo de forma de lágrima asociado con el tanque séptico, como una pluma de contaminación. El arreglo Wenner resultó en un modelo con estructura en formato de quilla alargado asociado con el cono de depresión, y uno en formato caída similar también asociado con el tanque séptico. El análisis comparativo muestra que la disposición Dipolo-dipolo se recomienda en las obras de modelado de estructuras tridimensionales de alta resistividad verticales en la zona saturada. La disposición Wenner y Schlumberger se recomiendan en estructuras de modelado en tres dimensiones verticales de baja resistividad en zona no saturada, con énfasis en la disposición Schlumberger.

Abstract: Biogas produced in sanitary landfills consists in a potential source, formed by degradation of organic matter, this gas is constituted by CH4, CO2 and water vapor. Sanitary landfills represent important depository of organic matter with great energetic potential in Brazil, although presently with inexpressive use. Estimates for production or maintenance of productive rates of CH4 represent one of the main difficulties of technical order to the planning and continuity of collection systems for rational consumption of this resource. Electrical resistivity measurements are routinuously used in profiling oil wells for the determination of levels with accumulations of oil and gas, facing the contrast among fluids and rocks. This paper aims to evaluate eventual relationship among biogas flow quantified in surface drains of a waste cell in landfill, with characteristic patterns of in depth electrical resistivity. The integration of Electrical Resistivity Tomography (ERT) lines allowed for the generation of 3D blocks and a clear distinction among zones of high biogas production, quantified in surface drains, with areas of high resistivity in depth. The results suggest the possibility of use of the method in studies to place drains in areas promising to the collection of biogas for energetic generation in sanitary landfill.

Resumen: El biogas producido en rellenos sanitarios puede ser una fuente importante de energía en el futuro. Este gas, constituido por CH4, CO2 y vapor de agua, se forma por la descomposición de materia orgánica. Una de las limitaciones técnicas en la planeación de sistemas colectores de este gas es la forma de estimar la producción de metano en un relleno dado. En este trabajo se evalúa la relación entre el flujo de biogas medido en drenes de un relleno sanitario en Brasil con la resistividad eléctrica del material de relleno. La medición en perfiles con el método de Tomografía de Resistividad Eléctrica (TRE) y su inversion a modelos 2D de resistividad muestra una clara correlación entre zonas de alta producción de biogás con áreas de alta resistividad en profundidad. Estos resultados sugieren la posibilidad de usar el método de TRE como una herramienta diagnostica en la colocación de drenes de extracción de biogas en rellenos sanitarios.

ResumoEsse estudo consiste na aquisição de dados magnetométricos na região de São Sepé (RS), sul do Brasil, com o propósito de avaliar o potencial de mineralização aurífera de um gabro, a partir de indícios obtidos em prospecção geoquímica de sedimentos de corrente prévios. O gabro denominado Santa Catarina está intrudido no Complexo Metamórfico Vacacaí, uma sequência metassedimentar ,onde foram reconhecidas diversas jazidas de ouro. Nesse estudo, foram realizadas nove linhas de magnetometria terrestre, com 1.200 m de comprimento cada, num total de 10.800 m e 720 estações de leitura. Os resultados sugerem a presença de mineralizações filonianas em fraturas, algumas das quais sujeitas à ação intempérica, com liberação e transporte de ouro por ação fluvial e deposição junto a sedimentos de corrente a jusante do gabro. O mapa de sinal analítico descreve as áreas de alta susceptibilidade magnética dentro de seus limites, coincidentes com lineamentos estruturais nas direções NE e E-W, associadas a à última das quatro fases de deformação regional, possivelmente responsável, tanto por fraturamento e abertura de espaços no gabro, quanto pela remobilização de sulfeto e ouro reconhecidamente descritos em diversas jazidas de ouro no âmbito do Complexo Metamórfico Vacacaí.

AbstractThis study involved magnetometric exploration in the region of São Sepé (RS), southern Brazil, to evaluate the potential for gold mineralization in a gabbro using evidence previously obtained from the geochemical exploration of stream sediments. The gabbro named Santa Catarina is intruded in the Metamorphic Complex Vacacaí, a metassedimentary sequence where several gold deposits were recognized. In this study, nine lines of land magnetometry were performed with 1.200m in length each, a total of 10.800m and 720 reading stations. The results suggest the presence of filonian mineralization in fractures, some of which are subject to weathering action, releasing and transporting gold by water action and depositing it along the stream sediments downstream from the gabbro. The analytical signal map outlines areas of high magnetic susceptibility within its boundaries, coinciding with structural lineaments in the NS and EW directions, associated with the last of the four stages of regional deformation, possibly responsible for both fracturing and opening of spaces in the gabbro, as by remobilization of sulfide and gold recognizably described in several gold deposits within the Vacacaí Metamorphic Complex.

Geophysical methods are widely used in mineral exploration. This paper discusses the results of geological and geophysical studies in supergene manganese deposits of southern Brazil. Mineralized zones as described in geological surveys were characterized as of low resistivity (20Ω.m) and high chargeability (30ms), pattern found also in oxides and sulfite mineral deposits. Pseudo-3D modeling of geophysical data allowed mapping at several depths. A relationship between high chargeability and low resistivity may define a pattern for high grade gonditic manganese ore. Large areas of high chargeability and high resistivity may result in accumulation of manganese and iron hydroxides, due to weathering of the gonditic ore, dissolution, percolation and precipitation.

Los métodos geofísicos constituyen una herramienta ampliamente utilizada en exploración mineral. Este trabajo presenta y discute los resultados de estudios geológicos y geofísicos desarrollados en un yacimiento de manganeso de origen supergénico, localizado en la región sudeste de Brasil. La zona mineralizada descrita en levantamientos geológicos fue caracterizada por bajos valores de resistividad (20Ω.m) y altos valores de cargabilidad (30ms), en un patrón similar al descrito en diversos trabajos en depósitos minerales de óxidos y sulfuros en rocas. Modelos geofísicos pseudo-3D permita la generación de mapas para diversas profundidades. Las áreas de alta cargabilidad y baja resistividad definen un patrón de mineralización gonditica con altos niveles de Mn. Áreas considerables con elevados valores de cargabilidad y baja resistividad probablemente resulten de la acumulación de hidróxido de manganeso y hierro, originados del intemperismo en cuerpos de mineral gonditico, disolución, percolación y precipitación.