The usefulness of electromagnetic (EM) methods for mineral exploration is severely restricted by the presence of a conductive overburden. Approximately 80% of the Australian continent is covered by regolith that contains some of the most conductive clays on Earth. As a result, frequency-domain methods are only effective for near surface investigations and time-domain methods, that are capable of deeper exploration, require the measurement of very small, late-time signals. Both methods suffer from the fact that the currents in the conductive Earth layers contribute a large portion of the total measured signal that may mask the signal from a conductive target. In the search for non-layered structures, this form of geological noise is the greatest impediment to the success of EM surveys in conductive terrains. Over the years a range of data acquisition and processing techniques have been used in an effort to enhance the response of the non-layered target and thereby increase the likelihood of its detection.The combined use of a variety of survey configurations to assist exploration and interpretation is not new and is practiced regularly. The active nature of EM exploration means that the measured response is determined to a large degree by the way in which the Earth is energised. Geological structures produce different responses to different stimuli. In this work, two new methods of data combination are used to transform the measured data into a residual quantity that enhances the signature of non-layered geological structures. Based on the concept of data redundancy and tested using the results of numerical modelling, the new combinations greatly increase the signal to noise ratio for targets located in a conductive environment by reducing the layered Earth contribution. The data combinations have application to frequency-domain and time-domain EM surveys and simple ++ / interpretive rules can be applied to the residuals to extract geological parameters useful in exploration. The new methods make use of inductive loop sources and can therefore also be applied to airborne surveys.Airborne surveys present special difficulties due to the data acquisition procedures commonly used. Flight-line related artefacts such as herringbones detract from the appearance of maps and make boundary definition more difficult. A new procedure, based on the Radon transform, is used to remove herringbones from airborne EM maps and locate the conductive boundaries correctly, making interpretation more reliable and easier. In addition, selective filtering of the Radon transform data enables the enhancement or attenuation of specific linear features shown in the map to emphasise features of interest. Comparison of the Radon transform procedures with the more conventional Fourier transform methods shaves the Radon transform processing to be more versatile and less prone to distortion of the features in a map.The procedures developed in this work are applied to field data with good results.

The Paleoproterozoic Talbot volcanogenic massive sulphide (VMS) Cu-Zn occurrence is located near Talbot Lake, Manitoba, about 80 km south of Snow Lake. The mineralised system is unconformably overlain by more than 100 m of Paleozoic dolomite sequences and Quaternary glacial till. The clay fraction of the till contains pronounced anomalies of Zn, Cu, Ag, Pb, Au, Mn, Hg, Cd, Co, Bi and Se, which is ascribed to the formation of clay-humic complexes that have carbon-isotopic compositions of δ13C < -20‰. A VMS origin of the near-surface anomaly is confirmed by distinctly low 206Pb/204Pb ratios, compared to a more radiogenic till signature. The overall low 206Pb/204Pb ratios in the organic surface media black spruce bark, moss and humus also indicate input from a magmatic sulphide source, but likely reflect windblown material from the Flin Flon smelter stack at 160 km to the northwest. Black spruce tree rings that pre-date industrial sources of atmospheric metal input are used to measure historical element distributions because they record the local geochemistry at the time of heartwood growth and their root systems tap into large volumes of soil. At the Talbot prospect, the presence of secondary Zn from the till in black spruce tree cores is reflected in the Zn/Ca ratio, which eliminates the effect of dolomite-derived Zn. The process of element migration from buried mineralisation to the surface is complex and includes oxidation of sulphides, mobilisation and complexation of metal ions, physical upward transport, and deposition of indicator elements near the surface in accessible sampling media. To account for a significant influx of indicator elements into the relatively recently deposited till blanket, post-glacial groundwater upwelling is proposed to act as a major mechanism driving upward element migration. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2011-05-14 04:38:36.886

No description available.

Surficial geochemistry, particularly selective leach technology, has proven effective in revealing anomalous concentrations of ore indicator metals overlying zones of buried mineralization. This study focuses on the buried Zn-Cu-Au-Ag VMS deposit at McIlvenna Bay in the Flin Flon Greenstone Belt to determine whether the peat swamp at the surface contains any anomalies of ore indicator metals using simple surficial geochemical techniques. Three selective leaches were performed, ammonium acetate pH 5.0, hydroxylamine, and sodium pyrophosphate. The hydroxylamine leach, which selects for metals in the reducible phase often associated with Mn and Fe oxides, has the clearest anomaly for multiple metals observed simultaneously, at the greatest magnitude. The pyrophosphate leach, which selects for metals that are oxidizable, often associated with organics showed a clear anomaly only for Cu, despite the abundance of organic matter and its great affinity for binding metals, likely because the organic-metal complexes formed in this system are easily exchangeable and highly soluble, not allowing for the formation of clear anomalies. The use of selective leach technology on surficial soil or peat has shown to be effective for delineating ore indicator metal anomalies, giving surface projections of buried mineralization in various types of systems, as long as the dynamics of the system are well understood in order to determine the phase the metals are associated with.

Very much like the great navigations in the 14th century or the space programs, exploring remote parts of our planet is a dangerous, challenging, and unknown endeavor that drives human beings. We not only do it to find resources but also for the sake of science, looking for shreds of evidence of a past that we only speculate. Our civilization has been driven by courageous and visionary explorers and now the challenges are different, and they need to be investigated. The Unexplored Earth is a design project that aims to provide a vision of the future of mineral exploration in such an unknown planet, the Earth. Hopefully, the result presented in this paper will serve its purpose of inspiring both the mining industry and geological survey organizations throughout the world in developing new technologies and methods of exploration increasing the rate of discoveries with reduced expenditure in comparison with current scenarios. Pilgrim is an underground drone capable of exploring where humans are not able to go, performing geological, geophysical, and geochemical surveys within the Underground.

Biogeochemistry has been utilized successfully in Australia as a regional or fellow-up geochemical exploration techniques in the arid terranes of Australia. This Master's study is based on the biogeochemistry approach, which relies on the chemical analysis of plant tissues to obtain information on the geology and geochemistry of the underlying rocks. The project involved the systematic sampling and chemical analysis of plant materials and the supporting soils to establish the suitability of using particular tree species for environmental monitoring and their potential as a sample medium in geochemical exploration in the vicinity of the Temora Gold Mine, NSW, Australia. Working on 168 plant tissues (leaves, twigs and bark) in 54 plants species from 8 families at the three sites of background area, mineralized area and tailings area, and 54 supporting soil samples from three strata of 0-5 cm, 20-30 cm, and 30-40 cm, found that there was a good agreement between soil geochemistry and plant geochemistry on the result of a strong geochemical association between Au and As. The As-Au pattern was suggestive of the presence of the Au-As mineralization. Black cypress pine (Callitris endlicheri) LEAVES show a higher ratio of Asminjn/Aumin in the mineralized area than ASbkg/Aubkg in the background area, up to 7 times. The research finding suggests that the LEAVES of Black cypress pine (Callitris endlicheri) have a potential to be a biogeochemical sample medium as better indicators for Au. Golden wattle (Acacia pycnantha) BARK and Yellow box (E. melliodora) BARK appear to be better indicators for Au but more research is required. The most occurrence of anomalies of As, Au, Sb, Cu and Fe were found in Red box (E. polyanthemos) BARK. Red box (E. polyanthemos) BARK may have the potential to be an Au indicator in the area when Red box (E. polyanthemos) is present. Results on test-tolerant plants show that Eucalyptus species: Red box (E. polyanthemos), Coral gum (E. torquata), and Yellow box (E. melliodora) have a higher rate of uptake trace elements from the tailings soils. Therefore, Eucalyptus family generally adapted to metal-rich soils and can be used as cleaning-up indicators and environmental monitors for the tailings area of metal contaminated soils in the Temora Gold Mine.

The seismic reflection method has been used extensively in mineral exploration and for imaging crustal structures within hardrock environments. In this research the seismic reflection method has been used and studied to address problems associated with hardrock settings. Papers I and II, address delineating and imaging a sulfide ore body and its surrounding rocks and structures in Garpenberg, central Sweden, at an active mine. 3D ray-tracing and finite-difference modeling were performed and the results suggest that although the detection of the ore body by the seismic reflection method is possible in the area, the presence of backfilled stopes in the mine makes seismic imaging of it difficult. In paper III the deeper structures of the Pärvie fault system in northern Sweden were revealed down to about 8 km through 2D seismic reflection profiling. The resulting images were interpreted using microearthquake data as a constraint. Based on the interpretation, some locations were suggested for future scientific deep drilling into the fault system. In paper IV, the seismic signature of complex geological structures of the Cue-Weld Range area in Western Australia was studied using a portion of a deep 2D seismic reflection profile. The pronounced reflections on the seismic images were correlated to their corresponding rock units on an available surface geological map of the study area. 3D constant velocity ray-tracing was performed to constrain the interpretation. Furthermore, the proposed structural model was tested using a 2D acoustic finite-difference seismic modeling method. Based on this study, a new 3D structural model was proposed for the subsurface of the area. These studies have investigated the capability of the seismic reflection method for imaging crustal structures within challenging hardrock and complex geological settings and show some its potential, but also its limitations.

Submitted by LENON MELO ILHA null (lenonilha@unipampa.edu.br) on 2017-08-22T14:11:00Z No. of bitstreams: 1 Levantamento Magnetométrico em Sequência Metaultramáfica Mineralizada em Cromita, São Sepé (RS).pdf: 4941337 bytes, checksum: 4bae6be70b020d210ee384046ccfeadd (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-08-23T18:49:11Z (GMT) No. of bitstreams: 1 ilha_lm_me_rcla.pdf: 4941337 bytes, checksum: 4bae6be70b020d210ee384046ccfeadd (MD5) / Made available in DSpace on 2017-08-23T18:49:11Z (GMT). No. of bitstreams: 1 ilha_lm_me_rcla.pdf: 4941337 bytes, checksum: 4bae6be70b020d210ee384046ccfeadd (MD5) Previous issue date: 2017-06-30 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Estudos de prospecção e pesquisa mineral por meio da geofísica são fundamentais para o reconhecimento e incorporação de novas reservas, devido ao baixo custo em relação aos métodos diretos de investigação e a possibilidade de cobertura de amplas áreas. Este trabalho consiste na aplicação do método da Magnetometria Terrestre, na caracterização de um corpo ultramáfico metamorfizado e mineralizado em cromo, a área de estudo se localiza na zona rural do município de São Sepé (RS) e situada nos limites das rochas do Escudo Sul Riograndense. Os litotipos presentes na área são arenitos, rochas metavulcânicas e rochas máficas/ultramáficas. Foram realizadas 1677 leituras em linhas perpendiculares a direção principal do corpo ultramáfico, com espaçamento de 25 metros entre pontos de medida. Os mapas magnetométricos gerados revelam anomalias de alta intensidade, acima de 420nT no mapa de intensidade de campo total, relacionadas com as rochas ultramáficas. Os resultados demonstraram a aplicabilidade do método da magnetometria na individualização de ocorrências minerais magnéticas de dimensões métricas, e a possibilidade de uso na seleção de alvos para perfuração, amostragem e quantificação de teores, em rotinas de pesquisas por depósitos de cromo. / Studies of mineral research and exploration through geophysics are fundamental for the recognition and incorporation of new reserves, due to the low cost in relation to the direct methods of investigation and the possibility of covering large areas. This work consists of the application of the Terrestrial Magnetometry method, in the characterization of a metamorphic and mineralized chrome mineralized body, the study area is located in the rural area of the city of São Sepé (RS) and located in the limits of the rocks of the Escudo Sul Riograndense. The lithotypes present in the area are sandstones, metavulcanic rocks and mafic / ultramafic rocks. There were 1677 readings in lines perpendicular to the main direction of the ultramafic body, with spacing of 25 meters between measurement points. The generated magnetometric maps show high intensity anomalies, above 420nT in the map of total field strength, related to ultramafic rocks. The results demonstrated the applicability of the magnetometry method in the individualization of magnetic mineral occurrences of metric dimensions, and the possibility of use in the selection of targets for drilling, sampling and quantification of contents, in search routines for chromium deposits. / CNPq: 470821/2013

Abstract The thesis deals with numerical methods designed for the modeling and inversion of geophysical electromagnetic (EM) measurements using a conductive thin plate model. The main objectives are to study the EM induction problem in general and to develop practical interpretation tools for mineral prospecting in particular. The starting point is a linearized inversion method based on the singular value decomposition and a new adaptive damping method. The inversion method is introduced to the interpretation of time-domain EM (TEM) measurements using a thin plate in free-space. The central part of the thesis is a new approximate modeling method, which is based on an integral equation approach and a special lattice model. At first the modeling method is applied to the interpretation of frequency-domain EM (FEM) data using a thin plate in conductive two-layered earth. After this time-domain responses are modeled applying a Fourier-sine transform of broadband FEM computations. The results demonstrate that the approximate computational method can model the geophysical frequency and time-domain EM responses of a thin conductor in conductive host medium with sufficient accuracy, and that the inversion method can provide reliable estimates for the model parameters. The fast forward computation enables interactive interpretation of FEM data and feasible forward modeling of TEM responses. The misfit function mapping and analysis of the singular value decomposition have provided additional information about the sensitivity, resolution, and the correlation behavior of the thin plate parameters.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19411号 / 工博第4127号 / 新制||工||1636(附属図書館) / 32436 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 小池 克明, 教授 田村 正行, 教授 三ｹ田 均 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM