scholarly journals GEOELECTRICAL SIGNATURES AND THEIR RELATIONSHIPS WITH THE LATERITIC HORIZONS: A CASE STUDY OF THE N4EN MINE’S IRON CAVE, CARAJÁS COMPLEX, BRAZIL

2019 ◽  
Vol 37 (4) ◽  
pp. 235
Author(s):  
GUILHERME A. S. PROSDOCIMI ◽  
MARCO A. DA S. BRAGA ◽  
MARCELO R. BARBOSA ◽  
IURI VIANA BRANDI
Keyword(s):  
Electrical Resistivity ◽  
Well Logging ◽  
Near Surface ◽  
Applied Geophysics ◽  
Geophysical Surveys ◽  
Iron Mine ◽  
Northern Brazil ◽  
Iron Formations ◽  
Lateritic Profile

ABSTRACT The Brazilian speleological heritage is protected by laws, and every region where caves are present requires scientific studies to assist in environmental licensing. In the context of mining in iron formations, the near-surface geophysical studies using electroresistivity survey were performed in the cave N4E-0022, located at the N4EN iron mine, Carajás Complex, northern Brazil. The near-surface geophysical surveys generated continuous images that enhanced the lithostructural mapping of the lateritic profile, especially in places to which access by conventional methods was difficult. The electrical resistivity profiles were acquired with the dipole-dipole arrangement in the upper portion of the cave. Three sections were performed in SW-NE direction and two in SE-NW direction, totaling 435 meters of acquisition. The geoelectrical signatures were correlated with the lithologic logs of drillholes, the geophysical well logging and with the typical lateritic profile in the cave N4E-0022 surroundings. The results showed a satisfactory interpretation for the near-surface geoelectrical profiles and evolved to a comparison with the lateritic profile (lateritic crust, transition horizon, and saprolite horizon), providing inherent resistivity signatures for each modeled material.Keywords: applied geophysics, iron cave, Carajás.RESUMO O patrimônio espeleológico brasileiro é protegido por leis, e qualquer região com a presença de cavidades precisa de estudos científicos para auxiliar o licenciamento de empreendimentos. No contexto da mineração em terrenos ferríferos, estudos geofísicos rasos utilizando eletrorresistividade foram executados na cavidade N4E-0022, localizada no extremo norte da Mina de N4EN, Complexo Carajás. A geofísica rasa gerou imagens contínuas que potencializaram o mapeamento lito-estrutural do substrato rochoso, principalmente em locais de difícil acesso aos métodos convencionais. Os perfis de eletrorresistividade foram adquiridos com arranjo dipolo-dipolo na porção superior da cavidade. de modo paralelo entre si na porção superior da cavidade. Três seções foram executadas na direção SW-NE e duas na direção SE-NW, totalizando 435 metros de aquisição. As assinaturas geoelétricas das seções foram correlacionadas com as descrições litológicas de furos de sondagem, perfilagens geofísicas de furos de sonda e o mapeamento de detalhe do perfil laterítico no entorno da cavidade N4E-0022, evidenciando um resultado satisfatório para as interpretações realizadas. Os resultados evoluíram para uma comparação com o perfil de alteração típico de rochas ferruginosas (crosta laterítica, horizonte de transição e saprolito), e forneceram assinaturas de resistividades inerentes à cada material modelado. Palavras-chave: geofísica aplicada, caverna ferrífera, Carajás.

scholarly journals GEOPHYSICS APPLIED TO THE MAPPING OF NATURAL CAVES HOSTED IN IRON ORE IN CARAJÁS (PA), BRAZIL

2019 ◽  
Vol 37 (3) ◽  
pp. 249
Author(s):  
Maria Filipa Perez da Gama ◽  
Marco Antonio Braga ◽  
Marcelo Roberto Barbosa ◽  
Rafael Guimarães de Paula ◽  
Daniele Freitas Gonçalves ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Rock Mass ◽  
Geophysical Methods ◽  
Mining Operations ◽  
Near Surface ◽  
Geophysical Surveys ◽  
Iron Mine ◽  
Northern Brazil ◽  
Ground Penetrating ◽  
The Impact

 ABSTRACT. The Brazilian environmental licensing for mining activities requires technical-scientific studies to demonstrate that natural caves will be protected from the impact of the mining operations. This study presents the results of near-surface geophysical methods applied to geostructural mapping of the rock mass in which the caves are hosted. The ferruginous karstic terrains are challenging to the geophysical interpretation due to the caves’ modest dimensions and the large variations in the host rock physical properties. Electrical Resistivity and GPR (Ground Penetrating Radar) geophysical surveys, were performed overlaying a natural cave located in the surroundings of the N4EN iron mine, in the Carajás Province, northern Brazil. The resistivity data were useful to discriminate different lithotypes as well as the presence of humidity in the rock mass, while the GPR data revealed a detailed degree of fracturing of the rock mass. The presence of humidity and the highly fractured zones may constitute zones of greater fragility of the cave walls and ceiling.Keywords: speleology, GPR, electrical resistivity, near-surface geophysics.RESUMO. O licenciamento ambiental brasileiro para atividades de mineração requer que estudos técnico-científicos demonstrem que as cavernas serão protegidas do impacto das operações de mineração. Este artigo apresenta os resultados de métodos geofísicos rasos aplicados ao mapeamento geoestrutural do maciço rochoso em que as cavernas estão hospedadas. Os terrenos cársticos ferruginosos são desafiadores para a interpretação geofísica, devido às modestas dimensões das cavernas e às grandes variações nas propriedades físicas da rocha hospedeira. Levantamentos geofísicos de Resistividade Elétrica e GPR (Radar de Penetração no Solo) foram realizados sobre a uma caverna localizada no entorno da mina de ferro N4EN, na Província de Carajás, região Norte do Brasil. Os dados de resistividade foram úteis para discriminar diferentes litotipos, bem como a presença de umidade na massa rochosa, enquanto os dados de GPR revelaram em grau detalhado o fraturamento da massa rochosa. A presença de umidade e as zonas altamente fraturadas podem constituir zonas de maior fragilidade das paredes e teto da caverna.Palavras-chave: espeleologia, GPR, resistividade elétrica, geofísica rasa.

scholarly journals Geophysical site assessment of an active urban development site, southeastern suburb of Cairo, Egypt

2020 ◽  
Vol 54 (1) ◽  
pp. qjegh2018-151
Author(s):  
N. I. Medhat ◽  
M. Atya ◽  
E. A. Ragab ◽  
A. A. El-Kenawy ◽  
M. Abdel Zaher ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Structural Damage ◽  
Residential Buildings ◽  
Seismic Refraction ◽  
Urban Site ◽  
Site Assessment ◽  
Near Surface ◽  
Geophysical Surveys ◽  
Quarry Blasting ◽  
Ground Stability

There has been significant structural damage of newly built residential buildings in Quarter-27 District in the SE of Cairo, Egypt. A nearby active limestone quarry may also be affecting ground stability. This paper shows how a near-surface geophysical survey could characterize the site, unusually after the initial housing construction had already been undertaken. Geophysical surveys included seismic refraction (acquired between phases of quarry blasting), electrical resistivity and ground penetrating radar (GPR) 1D and 2D datasets. Geophysical results produced maps of a 3D ground model that also included water table depth, known major faults and a saturated layer that may have caused the building damage. Of the geophysical techniques trialled electrical resistivity tomography and GPR data were deemed optimal. This study shows that it is possible to undertake geophysical surveys to characterize a restricted urban site development.

scholarly journals Large-scale electrical resistivity tomography in the Cheb Basin (Eger Rift) at an ICDP monitoring drill site to image fluid-related structures

2019 ◽  
Author(s):  
Tobias Nickschick ◽  
Christina Flechsig ◽  
Jan Mrlina ◽  
Frank Oppermann ◽  
Felix Löbig ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Fault Zone ◽  
Large Scale ◽  
Earthquake Activity ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Scientific Drilling ◽  
Eger Rift ◽  
Geophysical Surveys ◽  
Cheb Basin

Abstract. The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N-S-striking Počatky-Plesná fault zone (PPZ) and the NW-SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are subject of an International Continental Scientific Drilling Program (ICDP) project in which several geophysical surveys are currently carried out to image the near-surface geologic situation, as existing boreholes are not sufficiently deep to characterize the structures. As electrical resistivity is a sensitive parameter to the presence of low-resistivity rock fractions as liquid fluids, clay minerals and also metallic components, a large-scale dipole-dipole experiment using a special type of electric resistivity tomography (ERT) was carried out in June 2017 in order to image fluid-relevant structures. We used static remote-controlled data loggers in conjunction with high-power current sources for generating sufficiently strong signals that could be detected all along the 6.5 km long profile with 100 m and 150 m dipole spacings. Extensive processing of time series and apparent resistivity data lead to a full pseudosection and allowing interpretation depths of more than 1000 m. The subsurface resistivity image reveals the deposition and transition of the overlying Neogene Vildštejn and Cypris formations, but also shows a very conductive basement of phyllites and granites that can be attributed to high salinization or rock alteration by these fluids in the tectonically stressed basement. Distinct, narrow pathways for CO2 ascent are not observed with this kind of setup which hints at wide degassing structures over several kilometers within the crust instead. We also observed gravity/GPS data along this profile in order to constrain ERT results. Gravity clearly shows the deepest part of the Cheb Basin along the profile, its limitation by MLF at NE end, but also shallower basement with an assumed basic intrusion in SW part of profile. We propose a conceptual model in which certain lithological layers act as caps for the ascending fluids, based on stratigraphic records and our results from this experiment, providing a basis for future drills in the area aimed at studying and monitoring fluids.

scholarly journals Linear discontinuous deformations in the light of investigations performed with ERT method

2018 ◽  
Vol 66 ◽  
pp. 01006 ◽  
Author(s):  
Piotr Strzałkowski ◽  
Roman Ścigała ◽  
Katarzyna Szafulera ◽  
Marek Kruczkowski
Keyword(s):  
Electrical Resistivity ◽  
Rock Mass ◽  
Electrical Resistivity Tomography ◽  
Underground Mining ◽  
Mining Area ◽  
Geological Structure ◽  
Mining Operations ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Geophysical Surveys

The article presents an example of using the electrical resistivity tomography method to assess the condition of shallow rock mass layers in the area of linear discontinuous deformations created in the past due to underground mining activity. The research concerned the mining area of one of the Upper Silesian Coal Basin mines, where intensive mining operations have been conducted for several decades. In the considered area, linear discontinuous deformations were created in the form of ground steps. Their location is related to characteristic layout of deposit accessing roadways and extraction fronts in several coal seams. The article analyzes the geological structure of the deposit and the state of deformation of the rock mass caused by mining operations. In order to evaluate the hitherto impacts, appropriate calculations of the extraction influence were performed, assuming different views on the summation of horizontal strain in long time intervals. The calculations were carried out using the theory of W.Budryk - S. Knothe. Theoretical considerations were supplemented with geophysical surveys performed with using electrical resistivity tomography. Obtained results of the near-surface layers ERT imaging in the form of resistivity profiles confirm the existence of rock loosening zones in the areas of discontinuous deformations occurrence.

A LOW-COST RESISTIVIMETER FOR USE IN PRACTICAL LECTURES OF APPLIED GEOPHYSICS

2016 ◽  
Vol 34 (1) ◽  
Author(s):  
Walter Sydney Dutra Folly ◽  
Aracy Sousa Senra
Keyword(s):  
Electrical Resistivity ◽  
Low Cost ◽  
Test Area ◽  
Vertical Electrical Sounding ◽  
Applied Geophysics ◽  
Resistivity Profile ◽  
Electrical Sounding ◽  
Good Agreement

ABSTRACT. We describe the construction and testing of a simple and efficient low-cost resistivimeter designed for use in practical classes in Applied Geophysics. The equipment was successfully tested in a vertical electrical sounding (VES) performed on sandy terrain within the campus of the Universidade Federal de Sergipe, Brazil. The VES results were in good agreement with the profiles obtained from two boreholes located approximately 500 m from the test area, clearly demonstrating the efficiency of the equipment and the adopted methodology.Keywords: vertical electrical sounding, electrical resistivity, resistivity profile. RESUMO. Neste artigo, descrevemos a construção e o teste de um resistivímetro de baixo custo, simples e eficiente, concebido para ser utilizado em aulas práticas de Geofísica Aplicada. O equipamento foi testado com a realização de uma sondagem elétrica vertical (SEV) em um terreno arenoso localizado no campus da Universidade Federal de Sergipe, Brasil. Os resultados obtidos nesta SEV apresentaram boa concordância com os perfis observados em dois poços de sondagem localizados a 500 m da área de teste, fato que comprovou a eficiência do equipamento e da metodologia adotada.Palavras-chave: sondagem elétrica vertical, resistividade elétrica, perfil de resistividade. 

scholarly journals Comparison between electrical resistivity tomography and tunnel seismic prediction 303 methods for detecting the water zone ahead of the tunnel face: A case study

2020 ◽  
Vol 12 (1) ◽  
pp. 1094-1104
Author(s):  
Nima Dastanboo ◽  
Xiao-Qing Li ◽  
Hamed Gharibdoost
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Geological Structure ◽  
Rock Properties ◽  
Electrical Tomography ◽  
Tunnel Face ◽  
Resistivity Tomography ◽  
Geological Conditions ◽  
Seismic Prediction

AbstractIn deep tunnels with hydro-geological conditions, it is paramount to investigate the geological structure of the region before excavating a tunnel; otherwise, unanticipated accidents may cause serious damage and delay the project. The purpose of this study is to investigate the geological properties ahead of a tunnel face using electrical resistivity tomography (ERT) and tunnel seismic prediction (TSP) methods. During construction of the Nosoud Tunnel located in western Iran, ERT and TSP 303 methods were employed to predict geological conditions ahead of the tunnel face. In this article, the results of applying these methods are discussed. In this case, we have compared the results of the ERT method with those of the TSP 303 method. This work utilizes seismic methods and electrical tomography as two geophysical techniques are able to detect rock properties ahead of a tunnel face. This study shows that although the results of these two methods are in good agreement with each other, the results of TSP 303 are more accurate and higher quality. Also, we believe that using another geophysical method, in addition to TSP 303, could be helpful in making decisions in support of excavation, especially in complicated geological conditions.

Electrical Resistivity and Induced Polarization signatures to delineate the near-surface aquifers contaminated with seawater invasion in Digha, West-Bengal, India

CATENA ◽  
2021 ◽  
Vol 207 ◽  
pp. 105596
Author(s):  
Prashant Kumar ◽  
Prarabdh Tiwari ◽  
Anand Singh ◽  
Arkoprovo Biswas ◽  
Tapas Acharya
Keyword(s):  
Electrical Resistivity ◽  
West Bengal ◽  
Induced Polarization ◽  
Near Surface
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