Geophysical Program Research Articles

A reconnaissance study for tracing and ordering new mineralisation zones using integrated remote sensing, GIS, and aeromagnetic techniques, west Allaqi-Heiani-Suture,Egypt

ABSTRACT Reducing expenses is a critical aspect of natural resource explorations, especially in the reconnaissance stage. Accordingly, GIS algorithms using the free remote sensing data were used to rank the probable mineralised zones before any future implementations of the high-cost drilling and/or detailed geophysical programmes. Geological and tectonic settings, and being a historical mineral resource were motivations to choose the Allaqi-Heiani Suture (AHS), Upper Egypt, as a study area. Remote sensing data were processed for tracing the probably mineralised alteration zones, determining fractures and dominating structural systems, and mapping different geological units. Various alteration minerals including hydroxyls–carbonates, ferrous and ferric iron oxides were detected over different rock units using band ratio (BR) and Crosta techniques. Different geological units were distinguished using false colour composite (FCC) images. Moreover, an intense fractured system, demonstrating the area, was revealed by tracing lineaments using informative, spatially enhanced remote-sensed images. Fractures within the altered rocks represent 35% of the total fracturing system in the AHS to indicate a structural system controlling mineralisation occurrences. The processing of magnetic data suggested a deep/buried nature of these remotely detected lineaments/structures. Reduced to pole (RTP) and tilt derivative (TDR) maps detected the buried magnetic sources, whereas zero contours of TDR, Euler deconvolution, analytic signal and source parameter imaging (SPI) techniques traced buried contacts/structures and estimated their depths. A GIS strategy depending on the intensity of the fracturing system and the presence of more than one type of alteration was applied to potential-rank the prospective mineralised occurrences over AHS. The correlation between ranked zones with the old/known mines showed encouraging evaluation.

A systematic approach for surface exploration of sites – analysis of international exploration programs

Abstract. The site selection procedure for a high-level radioactive waste repository in Germany is based on the Repository Site Selection Act (StandAG, 2017), which comprises three phases. In phase 2 the Federal Company for Radioactive Waste Disposal (BGE) will conduct surface exploration. Based on the exploratory findings, the further developed preliminary safety analyses, the common requirements and criteria, and potential socioeconomic analyses will be applied feeding into proposed sites for underground exploration. Commissioned by the BGE, the Federal Institute for Geosciences and Natural Resources (BGR) contributes to this procedure with the projects GeoMePS and ZuBeMErk, which collate and assess geoscientific and geophysical methods and programs for surface exploration. Their common goal is to develop recommendations for surface exploration of siting regions. For this purpose, the BGR has developed a systematic approach that includes (1) deducing exploration targets, (2) compilation of geoscientific and geophysical exploration methods in a database structure, and (3) analysis of case studies of national and international exploration programs for high-level radioactive waste disposal. Exploration targets are based on the common criteria and requirements as defined by the StandAG. The identified exploration targets (Kneuker et al., 2020) together with a large number of geoscientific and geophysical exploration methods were integrated and linked within the BGR database “GeM-DB”. All methods were evaluated according to their suitability and applicability for (a) the three defined host rocks (crystalline rock, claystone, rock salt) and (b) the previously defined exploration targets. In step (3) the BGR reviews national and international waste disposal programs exploring for crystalline rock, claystone, and rock salt. Here, the focus is on nondestructive and minimally invasive surface exploration techniques, such as geophysical airborne and ground-based methods or investigations in drill holes and on drill cores. The aims are to identify gaps in the method catalogue of the GeM-DB and to infer exploration directives for surface exploration during phase 2. An example is the analysis of the Swedish site selection process, especially the site investigation program. There, the site investigations are, e.g. the basis for the discipline-specific site descriptive models, which were applied for design and safety assessments (SKB, 2001). The Swedish site investigation program along with programs of other countries considering crystalline host rocks, such as Finland and Canada, show a common ground, which could be adapted for surface exploration of crystalline host rock regions in Germany. The assessment and evaluation of selected programs exploring for rock salt and claystone is currently in progress. The entire systematic approach of the projects GeoMePS and ZuBeMErk aims to develop recommendations for a nondestructive and minimally invasive surface exploration program of siting regions in Germany, regarding the lithological, structural, mechanical, and hydrogeological characterization of the different host rock formations.

Geological Survey of Queensland: Strategic Resources Exploration Program concludes, New Economy Minerals Initiative and geophysical programmes commence, and MT results released

In August the GSQ marked the conclusion of the 4-year (2017 - 21) Strategic Resources Exploration Program (SREP) with a workshop in Mount Isa to present all the final reports and datasets completed...

The influence of early experiences and university environment for female students choosing geoscience programs: a case study at Universidad de Chile

Abstract. This case study addresses the experiences of female undergraduate students in the geology and geophysics programs at Universidad de Chile. These majors are part of the Faculty of Physical Sciences and Mathematics (FCFM) and have a relatively large proportion of female representation compared to the other engineering and science majors at FCFM that are dominated by male students. We interviewed 12 female students in geoscience majors to understand (a) the reasons for choosing geoscience as a major and (b) their experiences both at FCFM and in geoscience in an institution with a strong masculine environment that aims to increase women's undergraduate enrollment. We found that the decision to pursue a geoscience career was made during high school, and they maintained this decision during the first years of college, which is heavily focused on mathematics and physics, with no geoscience-related courses. During this early period in college, known as the common core program, students perceived a hostile environment due to high academic demands and gender-based discrimination. Their experiences had a positive shift once they started the geoscience courses in their fifth or sixth semester. The relatively large proportion of female students in the geoscience majors at FCFM creates a positive environment in which the participants developed a sense of belonging in the geoscience community. Students also felt that the feminist movement during 2018 in Chile positively influenced their perspectives on their path at FCFM. These findings give insights for developing strategies to increase early interest, participation, and satisfaction of women in science, technology, engineering, and mathematics (STEM) disciplines at various educational levels.

Fifty years of the Brazilian Marine Geology and Geophysics Program (PGGM)

Fifty years of the Brazilian Marine Geology and Geophysics Program (PGGM)

AusAEM: Australia’s airborne electromagnetic continental-scale acquisition program

ABSTRACTThe AusAEM airborne electromagnetic (AEM) survey is one of the main components of the Exploring for the Future program. This Australian Government initiative is aimed at enhancing the geoscientific information available, to support resource exploration and to showcase Australia as a destination for investment opportunities. Regional geophysical mapping programs are the basis for informed mineral exploration and have enabled the building of a continental-scale inventory of Australia’s potential resource endowment. They also provide elements of the scientific backing for decision-making and answering a range of different geoscientific questions. The latest of these airborne initiatives AusAEM is composed of a series of wide line-spaced studies targeting acquisition of data for regional mapping in area of new frontiers; it is gathering data and unveiling information on extents never previously attempted by AEM surveys.

Geological Survey of Western Australia: Regional and crustal-scale geophysical programmes in 2019

Geological Survey of Western Australia: Regional and crustal-scale geophysical programmes in 2019

Comparison of geophysical inversion programs run on aeromagnetic data collected over the Highland Valley Copper district, British Columbia, Canada

ABSTRACTAs part of the Natural Sciences and Engineering Research Council of Canada–Canada Mining Innovation Council (NSERC-CMIC) Mineral Exploration Footprints project, three selected magnetic inversion programs (VPmg, MAG3D and VINV) were used to process the same aeromagnetic data set from the Highland Valley Copper district, British Columbia, Canada. In each case, the inversion was constrained using available geological and physical property constraints. Analysis of magnetic susceptibility data suggests that the observed aeromagnetic anomaly pattern includes effects associated with boundaries between lithological units and fault zone alteration resulting from removal of magnetite. Susceptibility contrast associated with alteration is greater than that associated with changes in lithology. The inversions seek to define the three-dimensional geometry of geological boundaries and the fractures are treated as high-frequency noise. Results from the three programs, although similar, are sensitive to attributes of the different algorithms. VPmg emphasises physical boundaries between geological domains, MAG3D produces a more blurred image, whereas VINV produces reasonable geological images. Computer performance using the different programs ranges from reasonable for VPmg to computer intensive for MAG3D and VINV. Differences in the results reflect the inherent uncertainty in producing inversions from “noisy” aeromagnetic data.

Effects Stimulated by Radiation of the SURA Facility in the Geophysical Experiments Program at the International Space Station in 2017

The set of experiments in 2017 included the forecasting of geo- and heliophysical conditions in the ionosphere, the choice of heating regimes at a minimum critical frequency of the F2 ionospheric layer, analysis of the ionosphere radio sounding results and measurements of geomagnetic perturbations using ground-based facilities, study of the potential for higher efficiency and probability of artificial effects on the ionosphere, and the establishment of a correlation between geomagnetic field variations and the radio heating facility cyclogram. The experiments were carried out with a combination of new heating conditions (pulse ratio, period of action, two-frequency and continuous heating, variations in radiated power, polarization, shortwave radiation direction, etc.) in the intervals between recurrent magnetic storms. Geomagnetic field pulsations (in accordance with the cyclogram) and substorm effects were stimulated by the SURA facility against a background of quiet geophysical conditions.

The Brent Crater: An Alkaline Igneous Complex

The Brent Crater was discovered in 1951 from aerial imagery. The Crater was thoroughly investigated in the 1950s to early 1970s. The consensus throughout this period of exploration was that the crater was the result of a chondrite impact. This theory was disputed in 1971 in a paper by K.L. Currie who proposed that the crater was the result of alkaline volcanic activity within the Nipissing Alkaline Petrographic Province which resulted in geochemically and morphologically similar formations in the area of Lake Nipissing. Little research has been conducted to further verify or dispute this theory since. A 1977 national Uranium reconnaissance program followed up by a 1983 and 1984 field exploration and airborne geophysics program located a verified alkaline volcanic structure 15 km east of the crater known as the Allan Lake Carbonatite. The geophysical and geochemical data acquired from this work was processed to create aweighted probability raster of indicator elements of alkaline igneous materials. The Allan Lake anomaly demonstrates a more significant anomaly than the anomaly present at the Brent Crater. This anomaly is proposed to be the result of higher erosional rates in the crater. This hypothesis was tested by analyzing lake sediment concentrations of indicator elements in the nearby lakes. Given the world-renowned status of the Brent Crater as an example of a chondrite impact crater, it is important to either confirm Currie’s theory as a fact or disprove the theory to allow the structure to continue to act as an analogue without uncertainty.

Interpreter Sam

Several years ago Stephen Hill, former SEG president and an adjunct professor at the University of Houston and the Colorado School of Mines, contacted Sam about providing input to an “Industry Expectations” investigation being conducted as part of SEG's University Excellence Program. This study was looking into the validity of the assumption that developing nations' undergraduate and graduate geophysics programs would excel if they had a relevant curriculum. As it turned out, Stephen learned that the written curricula in those countries were fine.

Multi-scale Seismic Measurements for CO2 Monitoring in an EOR/CCUS Project

Acquiring multi-scale seismic measurements – 3D surface seismic, vertical seismic profiles (VSPs), and cross-well seismic data – comes with high cost and can be an operationally challenging endeavour, particularly in an oilfield under active enhanced oil recovery (EOR) management, as is the case with the Farnsworth Unit (FWU) EOR Field Project. The three aforementioned measurements were implemented in the FWU geophysical program, and utilized in conjunction with downhole measurements to address multiple site characterization and monitoring objectives for both EOR optimization and carbon dioxide (CO2) sequestration and monitoring. The three geophysical methods will be discussed in this paper.

3D density modelling of Gemeric granites of the Western Carpathians

Abstract The position of the Gemeric Superunit within the Western Carpathians is unique due to the occurrence of the Lower Palaeozoic basement rocks together with the autochthonous Upper Palaeozoic cover. The Gemeric granites play one of the most important roles in the framework of the tectonic evolution of this mountain range. They can be observed in several small intrusions outcropping in the western and south-eastern parts of the Gemeric Superunit. Moreover, these granites are particularly interesting in terms of their mineralogy, petrology and ages. The comprehensive geological and geophysical research of the Gemeric granites can help us to better understand structures and tectonic evolution of the Western Carpathians. Therefore, a new and original 3D density model of the Gemeric granites was created by using the interactive geophysical program IGMAS. The results show clearly that the Gemeric granites represent the most significant upper crustal anomalous low-density body in the structure of the Gemeric Superunit. Their average thickness varies in the range of 5–8 km. The upper boundary of the Gemeric granites is much more rugged in comparison with the lower boundary. There are areas, where the granite body outcrops and/or is very close to the surface and places in which its upper boundary is deeper (on average 1 km in the north and 4–5 km in the south). While the depth of the lower boundary varies from 5–7 km in the north to 9–10 km in the south. The northern boundary of the Gemeric granites along the tectonic contact with the Rakovec and Klátov Groups (North Gemeric Units) was interpreted as very steep (almost vertical). The results of the 3D modelling show that the whole structure of the Gemeric Unit, not only the Gemeric granite itself, has an Alpine north-vergent nappe structure. Also, the model suggests that the Silicicum–Turnaicum and Meliaticum nappe units have been overthrusted onto the Golčatov Group.

우리나라 가스 하이드레이트 연구･개발

Gas hydrate project in Korea was initiated by Korea Institute of Geoscience and Mineral Resources (KIGAM) in 1996. To understand the potential of gas hydrate presence in the Ulleung Basin, East Sea, KIGAM collected the geophysical data and sediment samples in the southwestern part of the basin from 1997 to 1999. Bottom simulating reflector firstly was identified from the seismic data acquired in 2008. Regional geophysical surveys and geological studies have been also carried out by KIGAM from 2000 to 2004. KNOC also collected seismic data from 2001 to 2003. Based on the results from these preliminary researches, “Korean National Gas Hydrate Program” was launched in 2005. The program has been supported by the government, and carried out by KIGAM, KNOC and KOGAS under the management of Gas Hydrate R&D Organization. The program has undertaken geophysical survey programs and coring for the identification of gas hydrate occurrences, the assessment of gas hydrate resources in the basin, development of optimum production technology, environmental impact studies, and test production. The gas hydrate test production which originally was planned to be performed in 2015, is postponed to study further for safer and more successful testing. Currently, the second national program is being planned.

Development of a space-borne spectrometer to monitor atmospheric ozone.

A new compact satellite spectrometer dedicated to monitoring terrestrial atmospheric ozone (ozonometer) is in preparation for the Russian Geophysics Program. Four instruments at four satellites (Ionosphere) are intended to monitor the total ozone content by measuring spectra of scattered solar radiation in nadir. The spectrometer is based on the Rowland scheme with a concave holographic diffraction grating. It covers the near UV and visible range of the spectrum, 300-500nm, with a spectral resolution of ∼0.3 nm. At present, a qualification model has been manufactured and tested. We introduce the description of the instrument and the results of laboratory and ground-based atmospheric calibrations. The ozone amount retrieved from atmospheric measurements using the differential optical absorption spectroscopy (DOAS) method is in good agreement with that measured by the collocated Brewer spectrophotometer and ozone monitoring instrument on board the Aura satellite.

О проблемах и ценностных приоритетах образовательной системы бакалавриата (на примере программ геофизического направления)

О проблемах и ценностных приоритетах образовательной системы бакалавриата (на примере программ геофизического направления)

Cross-borehole flow profiling—delineating subsurface flow paths within a geophysically defined aquifer framework

An extensive geophysical tool box is available with which to construct models of subsurface flow paths in complex aquifers using a combination of surface and borehole methods. These methods include electromagnetic and seismic sounding from the surface and downhole-imaging methods based on acoustic, optical, and electrical properties of rocks surrounding the borehole. However, such methods are inherently limited in hydrogeophysics because of the need to measure properties such as rock alteration or local fracture density that are indirectly related to subsurface flow rather than directly sampling the hydraulic parameters (permeability, storage coefficient, and hydraulic head) of subsurface flow paths. High-resolution borehole flow profiles provide an opportunity to relate geophysical characterization to hydraulic properties as an integral part of the standard geophysical logging program. Single-borehole flow analysis provides information on the hydraulic properties of flow paths in the limited region immediately adjacent to the borehole. Cross-borehole methods, where flow is measured in one borehole while an adjacent borehole is stressed, characterize the large-scale flow paths that connect the individual flow zones identified in individual boreholes.

Expression of terrain and surface geology in high-resolution helicopter-borne gravity gradient (AGG) data: Examples from Great Sand Dunes National Park, Rio Grande Rift, Colorado

Airborne gravity gradient (AGG) data are rapidly becoming standard components of geophysical mapping programs because of their advantages in cost, access, and resolution over measurements of the gravity field on the ground. Unlike conventional techniques that measure the gravity field, AGG methods measure derivatives of the gravity field. This means that effects of terrain and near-surface geology are amplified in AGG data, and that proper terrain corrections are critically important for AGG data processing. However, terrain corrections require reasonable estimates of density for the rocks and sediments that make up the terrain. A recommended philosophical approach is to use the terrain and surface geology, with their strong expression in AGG data, to the interpreter's advantage. An example of such an approach is presented here for an area with difficult ground access and little ground gravity data. Nettleton-style profiling is used with AGG data to estimate the densities of the sand dunefield and adjacent Precambrian rocks from the area of Great Sand Dunes National Park in southern Colorado. Processing of the AGG data using the density estimate for the dunefield allows buried structures, including a hypothesized buried basement bench, to be mapped beneath the sand dunes.

US coal geophysics expands and gains more support.

SUMMARY The US coal geophysics program was once the exclusive domain and best kept secret of one major coal company. The company was able to develop a full spectrum of remote-sensing technologies to address their complex upstream and downstream challenges. The program started in the mid-1970s, and greatly expanded a decade later with more robust and diverse applications. Innovative geophysical surveys were routinely conducted to enhance the company’s coal exploration, engineering, and environmental programs. As the largest operator of underground longwall mines in the country, Consol Energy was able to improve their mining productivity and mine safety by detecting and imaging potential geologic anomalies that could create adverse underground mining conditions prior to mine development. High-resolution surface seismic surveys were routinely conducted years in advance of mine development. Other geophysical methods were at times employed as part of internal multi-disciplinary (geology, geophysics, geohydrology, and ground control) studies to address environmental, engineering, and permitting issues.

Recognizing stakeholders in the design of effective community-level geophysics programs

Despite the challenges involved in implementing “humanitarian geophysics” projects, the potential impact of these projects is vast—particularly for engaging the public and encouraging a new and diverse generation of students to pursue careers in geophysics. Established programs like Engineers without Borders and emerging programs like Geoscientists Without Borders (GWB), which is administered through the SEG Foundation, provide unprecedented opportunities for geoscientists to become engaged in projects with a humanitarian focus. Many of us are excited by the prospect of using our knowledge and skills to make impacts on communities in a direct and immediate way. As scientists, it is easy for us to focus on addressing the technical issues of a project, such as selecting appropriate measurement methods and overcoming the daunting logistics of field operations—particularly if the project is in a foreign country. To create effective programs, however, it is equally important for us to consider nontechnical issues in the planning phase of a project, such as the role of stakeholders.