Geophysical methods used in the discovery of the Kitumba iron oxide copper gold deposit

2015 ◽  
Vol 3 (2) ◽  
pp. SL15-SL25 ◽  
Author(s):  
Thomas R. H. Woolrych ◽  
Asbjorn N. Christensen ◽  
Darcy L. McGill ◽  
Tom Whiting
Keyword(s):  
Iron Oxide ◽  
Structural Information ◽  
Geophysical Methods ◽  
3D Models ◽  
Induced Polarization ◽  
Magnetic Data ◽  
Airborne Gravity ◽  
Data Sets ◽  
Geologic Mapping ◽  
Copper Gold

A range of geophysical techniques has been used at various stages of the discovery and delineation of the Kitumba deposit in Central Zambia. Early era magnetics, geologic mapping, artisanal Cu plays, and the application of an iron oxide copper gold (IOCG) exploration model led explorers to the area in the 1990s. An airborne gravity gradiometer (AGG) survey was flown in 2004, and it highlighted key regional elements considered to be prerequisite for prospective IOCG mineralization. The AGG survey accurately delineated the spatial extents of two target areas referred to as the Kitumba and Mutoya systems. Gravity, radiometric, and magnetic data sets acquired as part of the AGG survey have mapped geologic and structural information as well as the extent of the IOCG alteration system. Significant uranium anomalism in the radiometric data was identified at Kitumba upon which the discovery hole S36-001 was sited. In 2012, a 3D direct current resistivity and induced polarization survey was conducted over Kitumba. The survey results provided 3D models of induced polarization chargeability anomalism and allowed successful delineation of sulfide material within the known deposit. The survey also provided an enhanced understanding of the 3D geometry of the mineralization. This improved understanding allowed a refocusing of drilling activities to best target extensions to existing mineralization.

scholarly journals Prospectivity analysis of gold and iron oxide copper-gold-(silver) mineralizations from the Faina Greenstone Belt, Brazil, using multiple data sets

2017 ◽  
Vol 47 (4) ◽  
pp. 561-590
Author(s):  
Daniela Schievano de Campos ◽  
Adalene Moreira Silva ◽  
Catarina Laboure Bemfica Toledo ◽  
Marcelo Juliano de Carvalho ◽  
Vinícius Gomes Rodrigues ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Greenstone Belt ◽  
Gold Deposits ◽  
Data Sets ◽  
Multiple Data ◽  
Gold Silver ◽  
Target Sites ◽  
Copper Gold ◽  
Multiple Data Sets ◽  
Fuzzy Logic Technique

ABSTRACT: The Faina Greenstone Belt is located in the southern sector of the Goiás Archean Block and has been investigated since the 18th century because of its gold deposits. Recent studies have revealed the polymetallic potential of the belt, which is indicated by anomalous levels of Ag, Cu, Fe and Co in addition to Mn, Ba, Li, Ni, Cr and Zn. This study was developed based on a detailed analysis of two selected target sites, Cascavel and Tinteiro, and multiple data sets, such as airborne geophysics, geochemistry and geological information. These datasets were used to create a final prospectivity map using the fuzzy logic technique. The gold mineralization of Cascavel target is inserted in an orogenic system and occurs in two overlapping quartz veins systems, called Mestre-Cascavel and Cuca, embedded in quartzite with an average thickness 50 cm and guidance N45º-60ºW/25ºSW with free coarse gold in grains 2-3 mm to 3 cm. The prospectivity map created for this prospect generated four first-order favorable areas for mineralization and new medium-favorability foci. The Tinteiro area, derived from studies conducted by Orinoco do Brasil Mineração Ltda., shows polymetallic mineralization associated with an iron oxide-copper-gold ore deposit (IOCG) system posterior to Cascavel target mineralization. Its prospectivity map generated 19 new target sites with the potential for Au, Cu and Ag mineralization, suggesting new directions for future prospecting programs.

Application of 3D magnetic amplitude inversion to iron oxide-copper-gold deposits at low magnetic latitudes: A case study from Carajás Mineral Province, Brazil

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. B13-B22 ◽  
Author(s):  
Marcelo Leão-Santos ◽  
Yaoguo Li ◽  
Roberto Moraes
Keyword(s):  
Iron Oxide ◽  
Gold Deposits ◽  
Magnetic Data ◽  
Magnetic Latitude ◽  
Amplitude Inversion ◽  
Carajás Mineral Province ◽  
Amplitude Data ◽  
Copper Gold ◽  
Magnetic Amplitude

Strong hydrothermal alteration modifies rock physical properties in iron oxide-copper-gold deposits (IOCGs) and may result in characteristic signatures detectable in geophysical surveys. Magnetic data are commonly used in characterizing orebodies, and 3D inversions are often used to assist in interpretations. In areas with strong remanence and self-demagnetization, the total magnetization can have directions different from the inducing field direction. This deviation precludes the use of traditional inversion methods. Magnetic amplitude inversion offers one solution to this challenge because the amplitude data are weakly dependent on the magnetization direction. In addition, the low magnetic latitude also imposes difficulty in amplitude data calculation due to the instability in the component conversion in the wavenumber domain. To formulate a practical approach, we present a case study on applying the magnetic amplitude inversion to the Furnas southeast IOCG deposit at the low magnetic latitude in Carajás Mineral Province, Brazil, and demonstrate that the approach can reliably recover an interpretable distribution of effective magnetic susceptibility and identify massive magnetite from hydrothermal alterations associated with the high-grade ore.

scholarly journals AIRBORNE GRAVITY GRADIOMETRY SURVEY IN THE SOUTHEASTERN PORTION OF PIMENTA BUENO GRABEN IN PARECIS BASIN: INTEGRATED 2D FORWARD MODELING AND ITS IMPLICATIONS IN DEFINING A NEW STRUCTURAL FRAMEWORK

2015 ◽  
Vol 33 (1) ◽  
pp. 101 ◽  
Author(s):  
Alan De Souza Cunha ◽  
Fábio Andre Perosi ◽  
Luiz Fernando Braga ◽  
Leandro Barros Adriano ◽  
Marlon Cabrera Hidalgo-Gato ◽  
...  
Keyword(s):  
Geophysical Methods ◽  
Forward Modeling ◽  
Magnetic Data ◽  
Airborne Gravity ◽  
Gravity Gradiometry ◽  
Seismic Section ◽  
Technical Data ◽  
Geophysical Surveys ◽  
Well Data ◽  
Airborne Gravity Gradiometry

ABSTRACT. Airborne geophysical surveys are widely used in geological prospecting of hydrocarbon reservoirs. The efficiency and acquisition speed of these methods in covering large areas accredit them as a key tool for any exploration project where there are sparse technical data available to support the exploratory decisions. Among the airborne geophysical methods, potential methods, namely, gravity and magnetics are the most spread in oil & gas projects of this nature. Such methods are used to support the generation of regional geological knowledge and also in detailed approaches, integrated with seismic, geochemical and well data. The objectives of this work were to describe the FalconTM Airborne Gravity Gradiometry System, explaining acquisition and processing steps, and crosscheck the results of its application in the southeastern portion of the Parecis Basin with two proposed models for the structural genesis and evolution proposed by the academy. Throughout the integration of the airborne gravity gradiometry and magnetic data along 2D seismic section it was possible to infer the geometry of the Pimenta Bueno Graben. While many works have mapped basement depth about 7,000 m, the current modeling shows basement deeper than 10,000 m.Keywords: airborne gravity gradiometry, 2D forward modeling, Parecis Basin, FalconTM, tectonic framework.RESUMO. Levantamentos aerogeofísicos são amplamente utilizados na prospecção geológica de reservatórios de hidrocarbonetos. A eficiência e a velocidade de aquisição desses métodos na cobertura de grandes áreas os credenciam como uma ferramenta fundamental para qualquer projeto de exploração onde há poucos dados técnicos disponíveis para apoiar as decisões exploratórias. Dentre os métodos geofísicos aéreos, os potenciais gravimétricos e magnetométricos são os mais utilizados em projetos da natureza de prospecção de óleo e gás. Tais métodos são utilizados para apoiar a geração de conhecimento geológico regional e também em abordagens de detalhe, integrados com seções sísmicas, dados geoquímicos e de poço. Este trabalho pretende apresentar o Sistema FalconTM de Gravimetria Gradiométrica, descrevendo suas etapas de aquisição e processamento, e interpretação dos resultados de sua aplicação na porção sudeste da Bacia do Parecis, em confronto com dois modelos propostos para a gênese e evolução estrutural da Bacia. Através da integração dos dados de gravimetria gradiométrica com dados magnéticos extraídos ao longo da secção sísmica 2D foi possível inferir a geometria detalhada do graben de Pimenta Bueno. Enquanto trabalhos anteriores mapearam a profundidade do embasamento em cerca de 7.000 metros, uma modelagem 2D direta e vinculada mostra que o mesmo pode alcançar, de forma localizada, profundidades maiores que 10.000 metros.Palavras-chave: gravimetria gradiométrica aérea, modelagem direta 2D, Bacia dos Parecis, FalconTM, arcabouc¸o tectônico.

Constraining magnetic amplitude inversion with magnetotelluric data to image volcanic units: A case study

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. B63-B75
Author(s):  
Kaijun Xu ◽  
Yaoguo Li
Keyword(s):  
Structural Information ◽  
Geophysical Methods ◽  
Magnetic Data ◽  
Structural Constraints ◽  
Structural Constraint ◽  
Magnetotelluric Data ◽  
Amplitude Inversion ◽  
Amplitude Data ◽  
Magnetic Amplitude

We present a case study on imaging volcanic units in gas exploration by constraining magnetic amplitude inversions using magnetotelluric (MT) sounding data at sparse locations. Magnetic data can be effective in mapping volcanic units because they have remanent magnetization and significant susceptibility contrast with surrounding rocks. Although magnetic data can identify the lateral distribution of volcanic units, they often have difficulties in defining the depth extent. For this reason, additional structural constraints from other geophysical methods can often help improve the vertical resolution. Among the independent geophysical methods, MT data can provide the needed structural information at a low cost. We have investigated an approach to combine a set of sparse MT soundings with magnetic amplitude data to image the distribution of volcanics in a basin environment. We first use a blocky 1D MT inversion based on Ekblom norm to obtain the structural constraint, and then we perform a constrained 3D magnetic amplitude inversion to recover the distribution of effective susceptibility by incorporating the structural information from MT soundings. We determine that even a small number of MT stations (e.g., 20) in a [Formula: see text] area is sufficient to drastically improve the magnetic amplitude inversion. Our results indicate that magnetic amplitude inversion with structural constraint from MT soundings form a practical and cost-effective means to map the lateral and vertical distribution of volcanics.

scholarly journals Structural Evolution of the Central Kiruna Area, Northern Norrbotten, Sweden: Implications on the Geologic Setting Generating Iron Oxide-Apatite and Epigenetic Iron and Copper Sulfides

2021 ◽  
Vol 116 (8) ◽  
pp. 1981-2009
Author(s):  
Joel B.H. Andersson ◽  
Tobias E. Bauer ◽  
Olof Martinsson
Keyword(s):  
Iron Oxide ◽  
Structural Evolution ◽  
Geologic Mapping ◽  
Basin Inversion ◽  
Copper Sulfides ◽  
Structural Framework ◽  
Temporal Relationships ◽  
Copper Gold ◽  
Geologic Setting ◽  
Back Arc

Abstract To guide future exploration, this predominantly field based study has investigated the structural evolution of the central Kiruna area, the type locality for iron oxide-apatite deposits that stands for a significant amount of the European iron ore production. Using a combination of geologic mapping focusing on structures and stratigraphy, petrography with focus on microstructures, X-ray computed tomography imaging of sulfide-structure relationships, and structural 2D-forward modeling, a structural framework is provided including spatial-temporal relationships between iron oxide-apatite emplacement, subeconomic Fe and Cu sulfide mineralization, and deformation. These relationships are important to constrain as a guidance for exploration in iron oxide-apatite and iron oxide copper-gold prospective terrains and may help to understand the genesis of these deposit types. Results suggest that the iron oxide-apatite deposits were emplaced in an intracontinental back-arc basin, and they formed precrustal shortening under shallow crustal conditions. Subsequent east-west crustal shortening under greenschist facies metamorphism inverted the basin along steep to moderately steep E-dipping structures, often subparallel with bedding and lithological contacts, with reverse, oblique to dip-slip, east-block-up sense of shears. Fe and Cu sulfides associated with Fe oxides are hosted by structures formed during the basin inversion and are spatially related to the iron oxide-apatite deposits but formed in fundamentally different structural settings and are separated in time. The inverted basin was gently refolded and later affected by hydraulic fracturing, which represent the last recorded deformation-hydrothermal events affecting the crustal architecture of central Kiruna.

Evaluation of mineral exploration targets defined by airborne gravity gradiometry through gravity and magnetic modelling: vicinity of the Iron Range Fault, Purcell anticlinorium, southern Canadian Cordillera

2019 ◽  
Vol 56 (5) ◽  
pp. 452-470
Author(s):  
Mike D. Thomas ◽  
Mark Pilkington ◽  
Mike McCuaig
Keyword(s):  
Iron Oxide ◽  
Regional Scale ◽  
Vertical Component ◽  
Magnetic Data ◽  
Airborne Gravity ◽  
Canadian Cordillera ◽  
Iron Range ◽  
Vertical Gravity Gradient ◽  
Magnetic Modelling

An airborne gravity gradiometer survey was recently flown over the Iron Range Fault in the Purcell anticlinorium, southern Canadian Cordillera. The fault is commonly associated with iron oxide mineralization having characteristics similar to those of iron oxide Au ± Cu deposits. Drilling near the fault has revealed Au ± Cu–Pb–Zn mineralization. Prominent positive vertical gravity gradient (VGG) anomalies defined by the survey were identified as targets for follow-up exploration. Possible sources of the target anomalies were investigated by modelling gravity, VGG, and magnetic data along several profiles. Modelling of regional-scale profiles of the vertical component of gravity crossing exploration targets provides a regional perspective on the regional geological setting, dominated by the broad Goat River anticline, whose axis closely follows the Iron Range Fault. Modelling indicates that several VGG anomalies are related to Moyie sills, although one anomaly is modelled as a narrow vertical body (120 m wide, 1000 m vertical extent, 40 m deep) just west of the Iron Range Fault. Its apparent high density of 3500 kg/m3 suggests metallic content, making it a choice candidate for follow-up investigation. Drilling at the southern end of this geophysical target intersected a Moyie intrusion, but untested geochemical anomalies in the vicinity encourage follow-up exploration. The densities of modelled units derived from VGG profiles across two other specific targets indicate that Moyie sills represent one target and iron oxide mineralization the other, as supported by magnetic modelling, which also delineated vertical zones of significantly magnetic material along the Iron Range Fault.

scholarly journals Integrated magnetotelluric and seismic investigation of Cenozoic graben structure near Obrzycko, Poland

2021 ◽  
Author(s):  
Adam Cygal ◽  
Michał Stefaniuk ◽  
Anna Kret
Keyword(s):  
Seismic Data ◽  
Geophysical Methods ◽  
Geological Structure ◽  
Data Sets ◽  
Low Velocity ◽  
Shallow Subsurface ◽  
Geophysical Model ◽  
Novel Approach ◽  
Loose Deposits ◽  
Static Corrections

AbstractThis article presents the results of an integrated interpretation of measurements made using Audio-Magnetotellurics and Seismic Reflection geophysical methods. The obtained results were used to build an integrated geophysical model of shallow subsurface cover consisting of Cenozoic deposits, which then formed the basis for a detailed lithological and tectonic interpretation of deeper Mesozoic sediments. Such shallow covers, consisting mainly of glacial Pleistocene deposits, are typical for central and northern Poland. This investigation concentrated on delineating the accurate geometry of Obrzycko Cenozoic graben structure filled with loose deposits, as it was of great importance to the acquisition, processing and interpretation of seismic data that was to reveal the tectonic structure of the Cretaceous and Jurassic sediments which underly the study area. Previously, some problems with estimation of seismic static corrections over similar grabens filled with more recent, low-velocity deposits were encountered. Therefore, a novel approach to estimating the exact thickness of such shallow cover consisting of low-velocity deposits was applied in the presented investigation. The study shows that some alternative geophysical data sets (such as magnetotellurics) can be used to significantly improve the imaging of geological structure in areas where seismic data are very distorted or too noisy to be used alone

scholarly journals A Review of Geophysical Modeling Based on Particle Swarm Optimization

2021 ◽  
Author(s):  
Francesca Pace ◽  
Alessandro Santilano ◽  
Alberto Godio
Keyword(s):  
Particle Swarm Optimization ◽  
Inverse Modeling ◽  
Critical Evaluation ◽  
Particle Swarm ◽  
Geophysical Data ◽  
Magnetic Data ◽  
Data Sets ◽  
Swarm Optimization ◽  
Geophysical Modeling ◽  
Original Works

AbstractThis paper reviews the application of the algorithm particle swarm optimization (PSO) to perform stochastic inverse modeling of geophysical data. The main features of PSO are summarized, and the most important contributions in several geophysical fields are analyzed. The aim is to indicate the fundamental steps of the evolution of PSO methodologies that have been adopted to model the Earth’s subsurface and then to undertake a critical evaluation of their benefits and limitations. Original works have been selected from the existing geophysical literature to illustrate successful PSO applied to the interpretation of electromagnetic (magnetotelluric and time-domain) data, gravimetric and magnetic data, self-potential, direct current and seismic data. These case studies are critically described and compared. In addition, joint optimization of multiple geophysical data sets by means of multi-objective PSO is presented to highlight the advantage of using a single solver that deploys Pareto optimality to handle different data sets without conflicting solutions. Finally, we propose best practices for the implementation of a customized algorithm from scratch to perform stochastic inverse modeling of any kind of geophysical data sets for the benefit of PSO practitioners or inexperienced researchers.

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