GEOELECTRIC PROSPECTION OF COPPER OCCURRENCE IN FOLDING LAYERS IN THE SUL-RIOGRANDENSE SHIELD (BRAZIL)

ABSTRACTSulfide prospecting with the geophysical methods, such as electrical resistivity and induced polarization, are promising due to the contrast of electrical resistivity and chargeability, where deposits with disseminated sulfides or filoneans are characterized by low resistivity and high polarizability. This work carried out a study of geophysical prospecting by means of tomographic acquisition in mineral copper occurrence, in the region of Caçapava do Sul. Three acquisition lines were performed by means of electrical tomography technique using a Dipole-dipole arrangement, with a length of 400 m and a spacing of 5 m between the electrodes, arranged in perpendicular layout to the structure of the area, represented by a large synclinal where research galleries with carbonates and copper sulfides were recognized in the ridge. The 2D inversion models and 3D multilevel maps indicate central and lateral regions with high resistivity and chargeability with indication of probable presence of copper sulfide, possibly housed in quartz veins. Peripheral zones with moderate resistivity and chargeability infer possible areas with presence of argilization, zones with high chargeability and low resistivity are likely to be zones of sulfation and possible silicification zones with high resistivity and low chargeability, observed in the vicinity of the probable mineralized zones.Keywords: Chargeability, Mineral Research, Resistivity, Sulfide, 3D Multilevel modeling.RESUMO A prospecção de sulfetos por meio de métodos geofísicos de eletrorresistividade e polarização induzida são altamente efetivos devido ao contraste de resistividade elétrica e cargabilidade, uma vez que os depósitos com sulfetos disseminados ou filoneanos são cvaracterizados por baixa resistividade e alta polarizabilidade. Esse trabalho realizou aquisição de tomografia elétricas em ocorrência mineral de cobre, na região de Caçapava do Sul (RS). Foram realizadas 3 linhas de tomografia elétrica em arranjo dipolo-dipolo, com 400 m de comprimento e 5 m de espaçamento entre eletrodos, dispostas de forma perpendicular à crista de um anticlinal, onde no passado foram reconhenhecidos carbonatos e sulfetos de cobre, em galerias de exploração mineral. Os modelos de inversão 2D e mapas de multiníveis 3D indicam regiões centrais e laterais com alta resistividade e alta cargabilidade com provável zona de sulfetos alojados em veios de quartzo. Zonas periféricas com moderada resistividade e cargabilidade sugerem a presença de argilização; zonas com alta cargabilidade e baixa resistividade são prováveis zonas de sulfetação e altos valores de resistividade e baixos de cargabilidade indicam zonas de silicificação.Palavras-chave: Cargabilidade, Pesquisa Mineral, Resistividade Elétrica, Sulfeto, Modelamento Multinível 3D.

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Multi-methodological investigation of a retrogressive thaw slump in the Richardson Mountains, Northwest Territories, Canada

10.5194/egusphere-egu2020-14201 ◽

2020 ◽

Author(s):

Julius Kunz ◽

Christof Kneisel ◽

Tobias Ullmann ◽

Roland Baumhauer

Keyword(s):

Electrical Resistivity ◽

Active Layer ◽

Geophysical Methods ◽

Three Dimensional ◽

Active Layer Thickness ◽

Permafrost Degradation ◽

Low Resistivity ◽

Permafrost Table ◽

Retrogressive Thaw Slump ◽

Richardson Mountains

The Mackenzie-Delta Region is known for strong morphological activity in context of global warming and permafrost degradation, which reveals in a large number of retrogressive thaw slumps. These are frequently found along the shorelines of inland lakes and the coast; however, this geomorphological phenomenon also occurs at inland &#8203;&#8203;streams and creeks of the Peel Plateau and the Richardson Mountains, located in the southwest of the delta. Here several active retrogressive thaw slumps are found of which some have reached an extent of several hectares, e.g. the mega slump at the Dempster Creek.In this study we investigated a recent retrogressive thaw slump at the edge of the Richardson Mountains close to the Dempster Highway to determine the subsurface properties using non-invasive geophysical methods. We performed three-dimensional Ground Penetrating Radar (GPR) surveys, as well as quasi-three-dimensional Electrical Resistivity Tomography (ERT) surveys in order to investigate the subsurface characteristics adjacent to the retreating headwall of the slump. These measurements provide information on the topography of the permafrost table, ice content and/or water pathways on top, within or under the permafrost layer. Additionally, we performed manual measurements of the active layer thickness for validation of the geophysical models. The approach was complemented by the analysis of high-resolution photogrammetric digital elevation models (DEM) that were generated using in situ drone acquisitions.The measured active layer depths show a strong influence of the relief and especially of small creeks on the permafrost table topography. Likely, this influence also is the primary trigger for the initial slump activity. In addition, the ERT measurements show strong variations of the electrical resistivity values in the upper few meters, which are indicative for heterogeneities, also within the ice-rich permafrost body. Especially noticeable is a layer of low resistivity values in an area adjacent to the slump headwall. This layer is found at depths between 4m to 7m, which approximately corresponds to the base of the headwall. Here, the low resistivity values could be indicative for an unfrozen or water-rich layer below the ice-rich permafrost. Consequently, this layer may have contributed to the initial formation of the slump and is important for the spatial extension of the slump.These results present new insights into the subsurface of an area adjacent to an active retrogressive thaw slump and may contribute to a better understanding of slump development.

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ENVIRONMENTAL GEOPHYSICAL DIAGNOSIS OF A CONTAMINATED AREA BY HYDROCARBONS IN A RAILWAY ACCIDENT IN THE MUNICIPALITY OF BOTUCATU – SP

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v36i4.865 ◽

2018 ◽

Vol 36 (4) ◽

pp. 1 ◽

Cited By ~ 1

Author(s):

Fernanda Cavallari ◽

César Augusto Moreira ◽

Lívia Portes Innocenti Helene

Keyword(s):

Electrical Resistivity ◽

Geophysical Methods ◽

3D Models ◽

Integrated Analysis ◽

Geological Environment ◽

Electrical Tomography ◽

Aquifer System ◽

History Of ◽

Physical And Chemical ◽

Contaminated Area

ABSTRACTThe diagnosis of contaminated areas is a mandatory procedure to treatment and remediation of soil and groundwater. Complex contaminants like hydrocarbons undergo physical and chemical changes along the dwell time in the geological environment, with changes in dissolution and spread in unsaturated and saturated soil aquifer system. This research describes the application of geophysical methods integrated with a history of chemical data in a contaminated area by leaked hydrocarborn in a railway accident, in 2005, at rural area in Botucatu (SP). The geophysical methods Electrical Resistivity and Induced Polarization were used by 5 parallel lines of electrical resistivity tomography in Schlumberger array, programmed and adjusted from a history of chemical analysis of groundwater. The electrical tomography data allowed thegeneration of 2D inversion models and visualization of 3D models. The data integrated analysis indicated the advanced state of degradation of hydrocarbons, recognized by high values of high chargeability in relation to the natural pattern of the area, concomitantly to areas of medium resistivity. This pattern may be indicative of the advanced state of degradation of the contaminants in the geological environment, with probable formation of sulphides resulting from the stabilization of the sulphur from the hydrocarbons and the iron present commonly found in tropical soils.RESUMOO diagnóstico de áreas contaminadas é um procedimento obrigatório ao tratamento e remediação de solo e águas subterrâneas. Contaminantes complexos como hidrocarbonetos passam por transformações físicas e químicas ao longo do tempo de permanência no ambiente geológico, com alterações no grau de dissolução no sistema aquífero. Este trabalho descreve a aplicação de métodos geofísicos integrados com um histórico de dados geoquímicos, numa área contaminada por hidrocarbonetos vazados num acidente ferroviário em 2005, na zona rural do município de Botucatu (SP). Foram utilizados os métodos geofísicos Eletrorresistividade e Polarização Induzida, por meio de 5 linhas paralelas de tomografia elétrica em arranjo Schlumberger, programadas e posicionadas a partir da interpretação de um histórico de análises geoquímicas do solo e água subterrânea. Os dados de tomografia elétrica permitiram a geração de modelos de inversão 2D e modelos de visualização 3D. A análise integrada de dados indica o avançado estado de degradação dos hidrocarbonetos, reconhecido por elevados valores de alta cargabilidade em relação ao padrão natural da área, concomitantemente a zonas de resistividade moderada. Este padrão pode ser um indicativo do avançado estado de degradação dos contaminantes no ambiente geológico, com provável neoformação de sulfetos oriundos estabilização do enxofre proveniente dos hidrocarbonetos e o ferro presente comumente encontrado em solos tropicais.

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Detecting fault zone characteristics and paleovalley incision using electrical resistivity: Loma Blanca Fault, New Mexico

Geophysics ◽

10.1190/geo2020-0375.1 ◽

2021 ◽

Vol 86 (3) ◽

pp. B209-B221

Author(s):

Heather Barnes ◽

Johnny R. Hinojosa ◽

Glenn A. Spinelli ◽

Peter S. Mozley ◽

Daniel Koning ◽

...

Keyword(s):

Electrical Resistivity ◽

Fault Zone ◽

Water Table ◽

Unsaturated Zone ◽

Late Quaternary ◽

Rio Grande ◽

Rio Grande Rift ◽

High Resistivity ◽

Low Resistivity ◽

Sand And Gravel

We have combined electrical resistivity tomography (ERT), geologic information from boreholes and outcrops, and hydrogeologic data to investigate field-scale fault-zone cementation of the Loma Blanca Fault in the Rio Grande Rift. We have collected electrical resistivity data from 16 transects and geologic samples from 29 boreholes (completed as groundwater wells to 30 m depth) across and around the fault. The 2D ERT profiles, whose interpretations are constrained by geologic data, indicate (1) a high resistivity zone in cemented portions of the fault below the water table and (2) in the unsaturated zone, a low-resistivity feature along the cemented portions of the fault. The high-resistivity zone below the water table is consistent with a 10% reduction in porosity due to the fault zone cementation. With the same porosity in the unsaturated zone, the low-resistivity feature in the cemented fault zone is consistent with saturation >0.7, in contrast to saturation 0.2–0.7 for sediment outside of the cemented fault zone. In addition, subsurface samples and ERT profiles delineate a buttress unconformity (i.e., steeply dipping erosional contact) corresponding to a paleovalley margin. This unconformity truncates the cemented fault zone and separates Pliocene axial-fluvial sand (deposited by an ancestral Rio Grande) from late Quaternary sand and gravel (deposited by the Rio Salado, a Rio Grande tributary). The cemented fault zone in the southern portion of the study area is a hydrogeologic barrier; north of the buttress unconformity, where the cemented fault zone has been removed by erosion, the fault is not a hydrogeologic barrier. The integration of geologic, geophysical, and hydrogeologic observations is key to developing our understanding of this complex system, and it allows us to demonstrate the utility of ERT in detecting subsurface fault-zone cementation.

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Ground penetrating radar and electrical resistivity tomography for locating buried building foundations: A case study in the city centre of Thessaloniki, Greece

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.10946 ◽

2016 ◽

Vol 47 (3) ◽

pp. 1355

Author(s):

G. Vargemezis ◽

N. Diamanti ◽

I. Fikos ◽

A. Stampolidis ◽

Th. Makedon ◽

...

Keyword(s):

Electrical Resistivity ◽

Ground Penetrating Radar ◽

Electrical Resistivity Tomography ◽

Geophysical Methods ◽

Geological Structure ◽

City Centre ◽

High Resistivity ◽

Resistivity Tomography ◽

Ground Penetrating ◽

The City

Ground penetrating radar (GPR) and electrical resistivity tomography (ERT) surveys have been carried out in the city centre of Thessaloniki (N. Greece), for investigating possible locations of buried building foundations. Geophysical survey has been chosen as a non-destructive investigation method since the area is currently used as a car parking and it is covered by asphalt. The geoelectrical sections derived from ERT data in combination with the GPR profiles provided a broad view of the subsurface. Regarding ERT, high resistivity values can be related to buried building remains, while lower resistivity values are more related to the surrounding geological materials. GPR surveying can also indicate man-made structures buried in the ground. Even though the two geophysical methods are affected in different ways by the subsurface conditions, the processed underground images from both techniques revealed great similarity. High resistivity anomalies and distinct GPR signals were observed in certain locations of the area under investigation, which are attributed to buried building foundations as well as the geological structure of the area.

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Pore resistivity variation by Resistivity imaging technique in sedimentary part of main Gadilam river basin, Cuddalore District, Tamil Nadu, India

Journal of Applied and Natural Science ◽

10.31018/jans.v13i1.2541 ◽

2021 ◽

Vol 13 (1) ◽

pp. 268-277

Author(s):

R. Ravi ◽

S. Aravindan ◽

C. Ramachandran ◽

Sanjay Kumar Balabantaray ◽

B. Selvaraj ◽

...

Keyword(s):

Electrical Resistivity ◽

River Basin ◽

Tamil Nadu ◽

Saline Water ◽

Groundwater Potential ◽

High Resistivity ◽

Clay Layer ◽

Clayey Sand ◽

Low Resistivity ◽

Matching Techniques

Electrical resistivity is the only property of physics which give information of subsurface moisture content in the formation, Hence geophysical electrical resistivity survey was carried out to investigate the nature of shallow subsurface formations and geological contact in the main Gadilam river basin of Cuddalore District in Tamil Nadu. Twenty-seven vertical electrical soundings (VES) were conducted by Schlumberger configuration in the basin. Data is interpreted by curve matching techniques using IPI2 WIN software, layer parameters like apparent resistivity (?a) and thickness (h) interpretation were exported to Geographic Information System (GIS). Interpretation distinguishes three major geoelectric layers like topsoil, sandy clay layer, clayey sand layer along the contact zone in the basin. Interpreted VES sounding curves are mostly four-layer cases of QH, H, HA and KH type. Investigation demarcates lithology of subsurface and hydrogeological set up by employing maximum possible electrode sounding to infer saline water and freshwater occurrence based on resistivity signals. Zone of groundwater potential map was prepared with the combination of resistivity (?= ?1+ ?2+ ?3+ ?4) and corresponding thickness (T= T1+T2+T3+T4). High resistivity value of >200 ? m and low resistivity value of <10 ? m show the occurrence of alkaline and saline water within the formation aquifers as a result of possible rock water interaction and saline water dissolution. Four-layer resistivity cases from the matched curve (namely KH, AH, QA, and KA type) show the resistivity distribution/variation. It separates the freshwater depth wish from 1 to 140 ? m in fluvial sediments. Flood basin, sandstone and clay layer with low resistivity value of 3.16 - 7.5 ? m indicates contact with saline and freshwater aquifer. The Iso – resistivity map delineates saline water and freshwater zones with in the fourth layer cases in the same locations to indicate the irrational way of abstracting groundwater, resulting in saltwater ingress.

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The Application of CRU-Resistivity Meters for Groundwater Investigation in Chantaburi, Thailand

Journal of Environmental and Engineering Geophysics ◽

10.2113/jeeg24.1.145 ◽

2019 ◽

Vol 24 (1) ◽

pp. 145-149

Author(s):

Pithan Pairojn

Keyword(s):

Electrical Resistivity ◽

Water Samples ◽

Low Cost ◽

Electrode Array ◽

High Resistivity ◽

Low Resistivity ◽

Total Dissolved Solid ◽

Resistivity Meter

This research proposes an investigation of groundwater by using 2D electrical resistivity techniques with the low-cost Chandrakasem Rajabhat University Resistivity Meter (CRU-Resistivity Meter) and processing with the Chandrakasem Rajabhat University Resistivity Images software (CRU-Resistivity Images). The resistivity meter, constructed of parts costing less than $1,000 USD, was tested at Soi Dao in Chantaburi, Thailand with a profile length of 90 m. Using a Wenner electrode array, the results showed that high resistivity zones greater than 100 ohm-m at a depth of 8 m generally considered to be topsoil with sand. Through testing, it was also found that low resistivity zones about 10 ohm-m at a depth of 20 to 50 m depth were generally considered a suitable subsurface range for good quality groundwater. The results of total dissolved solid (TDS) from water samples confirmed that groundwater at the sites of this example survey may be used for agriculture.

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Ground penetrating radar and electrical resistivity tomography for locating buried building foundations: A case study in the city centre of Thessaloniki, Greece

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.10930 ◽

2016 ◽

Vol 47 (3) ◽

pp. 1355

Author(s):

G. Vargemezis ◽

N. Diamanti ◽

I. Fikos ◽

A. Stampolidis ◽

Th. Makedon ◽

...

Keyword(s):

Electrical Resistivity ◽

Ground Penetrating Radar ◽

Electrical Resistivity Tomography ◽

Geophysical Methods ◽

Geological Structure ◽

City Centre ◽

High Resistivity ◽

Resistivity Tomography ◽

Ground Penetrating ◽

The City

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GEOPHYSICAL SURVEY AT THE OMALOS PLATEAU, CHANIA, CRETE

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16463 ◽

2004 ◽

Vol 36 (3) ◽

pp. 1204

Author(s):

Α. Βαφείδης ◽

Μ. Μανούτσογλου ◽

H. Hamdan ◽

Ν. Ανδρονικίδης ◽

Μ. Κουκαδάκη ◽

...

Keyword(s):

Electrical Resistivity ◽

Seismic Refraction ◽

Geophysical Methods ◽

Geophysical Survey ◽

Electrical Tomography ◽

Preliminary Results ◽

The Third ◽

High Electrical Resistivity ◽

Electrical Mapping ◽

Karstic Features

This paper discusses the preliminary results of a geophysical survey that was carried out at the Omalos plateau in Chania, Crete. The geophysical survey included measurements of electrical tomography, electrical mapping, seismic refraction, georadar, VLF and gravity. The aim of this survey is to compare the results from different geophysical methods used in imaging dolines and karstic features. The processing of the measurements indicates three geoelectrical layers. The first layer of extremely high electrical resistivity is attributed to alluvial - dilluvial deposits. The second layer of very low electrical resistivity reflects mainly the presence of marls. Finally, the third geoelectrical layer outlines the carbonate bedrock, whose relief appears highly irregular. The comparison of all geophysical methods leads to the same results, concerning the detection of dolines and karstic anomalies at the Omalos plateau.

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On the Rayleigh—Taylor instability in hydromagnetics with finite electrical resistivity and Hall current

Journal of Plasma Physics ◽

10.1017/s0022377800004670 ◽

1969 ◽

Vol 3 (4) ◽

pp. 633-642 ◽

Cited By ~ 25

Author(s):

Surindar Singh ◽

J. N. Tandon

Keyword(s):

Magnetic Field ◽

Electrical Resistivity ◽

Hall Current ◽

Incompressible Fluids ◽

Taylor Instability ◽

High Resistivity ◽

Horizontal Magnetic Field ◽

Low Resistivity ◽

Rayleigh Taylor Instability

The effect of Hall current and finite electrical resistivity has been studied on the Rayleigh—Taylor instability of superposed incompressible fluids in the presence of a uniform horizontal magnetic field. It is found that Hall current has a negligible stabilizing influence in the high resistivity limit whereas it has a destabilizing influence in the low resistivity limit.

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INTEGRATION OF GEOPHYSICAL METHODS IN THE STUDY OF ACID DRAINAGE IN URANIUM MINING WASTE

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v36i4.1968 ◽

2018 ◽

Vol 36 (4) ◽

pp. 1 ◽

Cited By ~ 2

Author(s):

Matheus Felipe Stanfoca Casagrande ◽

César Augusto Moreira ◽

Débora Andrade Targa ◽

Heber Luiz Caponi Alberti

Keyword(s):

Electrical Resistivity ◽

Preferential Flow ◽

Mine Drainage ◽

Geophysical Methods ◽

Sulfide Minerals ◽

Geochemical Data ◽

High Resistivity ◽

Groundwater Flux ◽

High Sulfur Concentration ◽

Physical And Chemical

ABSTRACT. Among the potential environmental impacts in mining activities, acid mine drainage (AMD) is a relevant problem caused by reactive minerals, such as sulfides, due to their exposure to the surface conditions. This is the context of contamination of a waste pile (BF-04) at Osamu Utsumi mine, closed in 1995 after years of physical and chemical processing of the uranium ore and currently under decommissioning plan. This study is based on the application of the combined geophysical methods of Electrical Resistivity and Induced Polarization and the analysis of previous geochemical data, aiming the evaluation of zones related to the generation of AMD and groundwater flux into the waste pile BF-04, containing sulfide minerals and uranium. The association of high resistivity and high chargeability zones is related to disseminated sulfide minerals in rock with silica cement. Infiltration of meteoric water through those zones induces the oxidation of sulfides, high sulfur concentration in groundwater followed by a drop in pH values, which results in a higher leaching capacity and solubility of ions and heavy metals. In addition, high chargeability zones (higher than 10 mV=V) represent portions of generation of AMD, while the low resistivity anomalies (under 70W:m) are related to preferential flow zones of the contaminated groundwater.Keywords: minning, sulfides, uranium, electrical resistivity, chargeability.RESUMO. Dentre os potenciais impactos ambientais em mineração, a drenagem ácida de mina (DAM) é um problema grande onde ocorrem minerais instáveis como os sulfetos, outrora isolados em subsuperfície. É neste contexto de contaminação do meio físico que está inserido uma pilha de rejeitos (BF-04) pertencente à mina de urânio Osamu Utsumi, cujas atividades de mineração, processamento físico e processamento químico foram encerradas em 1995, seguidas pela etapa de descomissionamento até os dias atuais. Neste estudo foram aplicados os métodos geofísicos da Eletrorressitividade e Polarização Induzida combinados com dados geoquímicos prévios, com o intuito de avaliar zonas de geração e fluxo de drenagem ácida de mina na pilha de rejeitos de mineração BF-04 com sulfetos e urânio. A combinação de zonas de alta resistividade e alta cargabilidade revela sulfetos disseminados em rochas com cimento silicático. A infiltração de águas meteóricas nestes locais induz a oxidação de sulfetos, liberação de enxofre nas águas subterrâneas seguida pela queda no pH, que resulta num efluente com alta capacidade de lixiviação e solubilidade de sais e metais. Neste sentido, zonas de alta cargabilidade (acima de 10 V=V) representam locais de geração de drenagem ácida de mina, enquanto que zonas de baixa resistividade (abaixo de 70 W:m) revelam zonas preferenciais de fluxo do efluente.Palavras-chave: mineração, sulfetos, urânio, resistividade, cargabilidade.

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