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Fractured-basement reservoirs are igneous or metamorphic rocks having no matrix porosity and low secondary fracture porosity of ~2–3% and generally are devoid of adequate void space to hold sufficient volume of hydrocarbons for economic production. Nevertheless, several giant and major oil fields of fractured basement reservoirs are known to host substantial reserves and produce significant amount of hydrocarbons and are therefore categorized under unconventional reservoirs. The prospectivity of fractured basement reservoirs depends exclusively on the volume of rocks fractured and geometry of fractures which comprises the dimensions, densities and orientations of the fractures. The intensity of the fracture geometry ultimately defines the network it creates to host and produce oil and gas economically. Some such fractured basement fields in the world are discussed along with the challenges in exploring the fractured-basement reservoirs.

Shale oil and gas reservoirs have become one of the fastest growing economically viable energy resource. Traditionally considered as a source and cap rock for conventional hydrocarbon accumulations, shale by itself can be a reservoir by hosting the remnant part of oil and gas it generates which could not be expelled. Shale prospectivity is an arduous task for geoscientists to assess and more challenging for engineers to produce economically. Shale being a tight reservoir devoid of permeability, it requires hydraulic fracturing (fraking) to produce albeit at huge cost and environmental damage. Types of shale and their rock properties that make them potential prospects to produce hydrocarbon are analyzed. Seismic role in shale exploration by providing leads to shale plays, characterization of shale reservoirs and monitoring fracking for hydrocarbon production is deliberated.

Recent exploration has identified a series of Cu-Mo skarn deposits within the Xuancheng-Magushan orefield. The orefield forms part of the Nanling-Xuancheng mining district, which is located within the Middle-Lower Yangtze River Metallogenic Belt (MLYRMB) of central-eastern China. However, this area contains thick and widespread unprospective sedimentary cover sequences that have impeded traditional approaches to mineral exploration. This study presents the results of 3D numerical simulation modeling that identifies possible mineral exploration targets within the entire Xuancheng-Magushan orefield. This modeling enables the identification of unexplored areas with significant exploration potential that are covered by thick sedimentary sequences that cannot be easily explored using traditional exploration approaches. This study outlines the practical value of 3D numerical simulation-based targeting in areas with thick sedimentary cover sequences and uses the Flac3D software package to couple processes involved in ore formation such as stress, pressure, and heat transfer. Here, we use volumetric strain increments calculated during numerical modeling as the thermodynamic representation of the generation of space during prograde skarn formation, with this space filed by sulfides either penecontemporaneously or soon after magmatism. This process occurred during retrograde hydrothermal ore formation and the genesis of the skarn-type mineralization in this area. The results of the volumetric strain increment calculated during this numerical modeling study matches the distribution of known mineralization as well as delineating eight potential targets that have not yet been explored but represent areas of significant exploration potential within the Xuancheng-Magushan orefield, indicating these targets should be considered prospective for future mineral exploration. One of these targets was also identified during our previous Comsol-based numerical modeling of the formation of the Magushan Cu-Mo skarn deposit. The fact that this area has been identified as prospective using two different numerical modeling methods indicates that this area should be prioritized for future exploration and also validates the numerical modeling approaches used here and in our previous research that more specifically focused on the Magushan skarn deposit. Overall, our study indicates that prospectivity modeling using 3D numerical simulation-based approaches can be both effective and economical and should be considered an additional tool for future mineral exploration to reduce exploration risks when targeting mineralization in areas with thick and unprospective sedimentary cover sequences.

Currently ADNOC is conducting the world's largest continuous 3D seismic acquisition campaign of approximately 90 000km2 with the aim of covering the entire Abu Dhabi emirate subsurface (both onshore and offshore) with 3D seismic. The main objective of this campaign is to provide high quality seismic data to explore conventional and unconventional resources. The new 3D covers areas that were under-explored in the past and is of excellent quality to apply advanced technologies for interpretation and reservoir characterization. The new 3D seismic data has high-trace density, broadband frequency content, full-azimuth and long offsets, which provides paramount information for detailed subsurface imaging and characterization of complex reservoirs.This study is focused on a 3D land seismic survey recently acquired that is currently at the time and depth imaging stage. The early-out volumes obtained from processing consist of valuable preliminary data that can be used to infer some possible exploration prospectivity features while final processing is still ongoing.A significant benefit of the pre-stack depth migration (PSDM) method is the construction of a detailed anisotropic subsurface velocity property model. Therefore, it accounts for lateral velocity variations, which are related to geological features especially attractive to explorationists, and has a more accurate overburden representation than historical time imaging workflows. Herein, we present some examples on how the 3D PSDM volume reveals more confidence in geological features that are not so clear in a pre-stack time migrated (PSTM) volume. The preliminary results indicate how shallow hydrocarbon presence can interfere with the PSDM velocity model and how it can be solved to reveal possible exploration potential in deeper sections.

Historic records have shown that lithium enriched geothermal waters circulate within natural geological fractures at depth in Cornwall. These fracture zones outcrop at surface and can be examined to understand which structures are most prospective for further exploration. Using airborne hyperspectral imagery, a rapid and high-resolution survey of alteration patterns can indicate the structures that have interacted with geothermal water. Spectra were analysed for kaolin and haematite minerals which were successfully identified and subsequently verified using lab analyses. A drilling campaign was successful in confirming the presence of lithium in structures that were identified in the remote sensing programme.

Geochemical exploration of stream sediments is an important step for the identification of areas of interest with potential mineralization, particularly in the early stages of mineral exploration. A total of 407 sample points for 15 different geochemical traces were collected from Central Wales and classified into two groups: a training group consisting of 285 samples and a testing group consisting of 122 samples. Geospatial characterization of each parameter at stream level was performed using two different prediction models; the inverse distance weighting and the geostatistical kriging. Several variations of the IDW model was applied based on the power function and the number of the sample points, and the best one selected based on “root mean square prediction error” statistic. The same statistic was also used in the best-fitted semivariogram models including the circular, spherical, exponential and Gaussian for each geochemical parameter in Kriging. Finally, the mineral prospectivity map of the area was developed based on the geochemical accumulation index (GAI) using multivariate overlay analysis. The experimental results show that there is no single method that can be used independently to predict the spatial distribution of geochemical elements in streams. Instead, a combinatory approach of IDW and kriging is advised in order to generate more accurate predictions. The mineral prospectivity map based on GAI showed that most of the mineral-enriched streams were found in northwest, northeast, and south part of the study area which was also confirmed with the existing mining activities in the region.

The successful application of geographic information system (GIS)-based mineral prospectivity mapping (MPM) essentially relies on two factors: one is reasonable evidential layers that conform to geological cognition, and the other is excellent models that can extract critical prospecting information from evidential layers. Geological features in MPM are usually discretized by categorizing them into classes and assigning the same or linear weights to each class, which suffer from bias in the interpretation of geological processes under ambiguous knowledge. Moreover, either unsupervised or supervised MPM models are constructed based on the assumption that the variables are relatively independent or identically distributed. In terms of these two issues, this study develops a joint workflow that combines a rational evidence layer weighting method and a deep learning MPM model, considering both the spatial and genetic associations of geological features. A data-driven singularity-based weighting method is first applied to evaluate the relative importance of geological features for mineralization and assign continuous weights to evidential layers using a nonlinear function that is consistent with existing geological models. Then, a more recent deep learning model, namely the long short-term memory network, is employed to extract and integrate the deep-level geological prospecting information among the weighted evidence layers. This joint approach was demonstrated with the help of a case study targeting Fe mineralization in southwestern Fujian Province, China. The mineral potential map obtained using this approach revealed that almost all the known Fe mineral deposits developed in the delineated high prospective regions, indicating that the proposed workflow is reasonable and meaningful for MPM.

Tungsten (W) is used in a variety of industrial and technological applications and has been identified as a critical mineral for the United States, India, the European Union, and other countries. These countries rely on W imports mostly from China, which leaves them vulnerable to supply disruption. Consequently, the U.S. government has a current initiative to understand domestic resource potential. The eastern Alaska portion of the Yukon-Tanana Upland (YTU), is prospective for W skarn deposits, the major source of global W supply. The regional geology consists of juxtaposed Paleozoic lithotectonic packages that were reaccreted to North America in the Mesozoic. Multiple subsequent episodes of arc-related magmatism intruded the lithotectonic packages, accompanied by W skarn formation mostly associated with 100–90 Ma intrusions; major W skarn deposits in Canada are part of the same metallogenic event (e.g., Mactung, Cantung). In this paper, we present an assessment for undiscovered W skarn resources for parts of the lesser-explored western (Alaskan) portion of the YTU. We used GIS proximity analysis to map the intersection of pluton and carbonate-bearing rocks to define three permissive tracts for W skarn deposits. The permissive tracts were qualitatively assessed by mineral potential mapping using region-wide sediment geochemistry and mineral concentrate datasets. This analysis showed that much of the western YTU has high potential for undiscovered W skarn deposits, whereas the eastern and southern YTU had only isolated areas of medium to high potential. Historical production and the quality of the geochemistry data of the western YTU tract (ca. 9200 km2) permitted a quantitative assessment of undiscovered W resources. Probabilistic estimates by a panel of 20 experts predicted a 70% chance of one to three undiscovered W skarn deposits in the western YTU tract. The rationale for favorability employed by the expert panel included favorable lithology, previous production, clustering of previously mined deposits, W placers in the area, lack of recent exploration, pan concentrates containing W minerals, and W geochemical anomalies. Estimates were combined with a global grade and tonnage model for W skarns in a Monte Carlo simulation and provided a median estimate of undiscovered resources of 94 kt WO3. If the undiscovered W skarn deposits are located close to infrastructure (e.g., near Fairbanks, or close to roads and/or power grid), application of an economic filter indicates that the median total economically recoverable WO3 is 63 kt with a net present value (NPV) of $330 million USD (2008 dollars). Whereas if deposits are far from infrastructure, median recoverable WO3 is only 30 kt and the NPV is $44 million. Our models for contained WO3 resources and NPV estimates for the western YTU tract are considerably lower than the known resources in skarns in adjacent areas in Canada. Estimates for the western YTU are also lower than preliminary estimates for undiscovered W skarn deposits in areas of the western conterminous United States. We speculate that lower permeability and continuity of favorable carbonate rock horizons in the relatively higher-grade metamorphic country rocks in the Alaska portion of the YTU may explain some of the differences in prospectivity. More detailed geologic mapping, modern geochemistry, and geophysical surveys are needed to refine the resource potential of the whole YTU. Regardless, quantitative mineral resource assessment provides a useful tool for making first-order regional estimates of undiscovered resources, identifying target areas for new data acquisition, and guiding research on the fundamental controls of district-scale metallogenic endowments.

Regression models are often employed in prospectivity modeling for the targeting of resources. Logistic regression has a well understood statistical foundation and uses an explicit model from which knowledge can be gained about the underlying phenomenon. In this paper, a model selection procedure based on logistic regression enhanced with nonlinearities is proposed. The method is designed to help the researcher in the model building process and can also be used as preprocessing step for other machine learning algorithms such as neural networks.

Overlooked prospects and underexplored fields in the Niger Delta Basin continue to attract the attention of many stakeholders in the industry as the quest to achieve the national 40 billion barrels oil reserve target continues to gain momentum. A key area of interest is that many wells drilled earlier in the basin were limitedlargely by technology from probing deeper formations. With the availability of 3D seismic data, improved subsurface knowledge, more efficient interpretation tools and skills, this study reevaluated the hydrocarbon potentials of the economically strategic ‘Pateke’ field in the Coastal Swamp Depobelt where the deepest well was drilled to a total depth of 8950 feet (2728 meters). Thereevaluation approach involved high precision fault and horizon mapping, seismic attribute extraction and analysis using the Petrel platform. The interpretation shows the structural framework of the field to be constituted by five faults with two major faults trending east – west and northwest – southeast respectively, thus dividing the field into three fault blocks. Integration of Root Mean Square (RMS) Amplitude, Envelope and Sweetness seismic volume attributes suggest probable hydrocarbon accumulations within the fault blocksthat lie far beneath the reach of the present wells in the field. The implication of this result is that the full potentials of ‘Pateke’ field are yet to be achieved considering the positive indications of economically recoverable hydrocarbons in the deeper sections of the field.

International audience; This study details new geochemical analysis from an outcrop in Crete to improve understanding of the hydrocarbon potential of the southern margin of the Hellenic Arc along the continental convergent zone of the central Mediterranean Ridge. Seventeen samples were collected from the Late Miocene sub-salt sedimentary succession of Plouti section in central Crete and were studied in terms of their organic geochemical features using Rock-Eval VI pyrolysis. Results of this investigation revealed intervals with sufficient organic material of good enough quality and quantity to be considered as potential source rocks. The obtained data generally present poor to fair and/or good in some cases hydrocarbon generation potential. The TOC values range from 0.03 to 1.99%, with an average fair (2.1 mg HC/g rock) hydrocarbon potential. A Type III kerogen was identified, indicating a terrestrial origin organic matter. T max and Production Index values suggest that the most promising parts of the section (organic-rich sediments) are immature with respect to oil generation and have not experienced high temperature during burial. Overall, the present study offers the opportunity to advance our understanding on the hydrocarbon potential onshore Crete and further investigate hydrocarbon prospectivity in the adjoining area, and particularly, the Greek part of the Mediterranean Ridge, a region with crucial economic and strategic importance.

The Labrador Trough in northern Quebec is currently the focus of ongoing exploration for magmatic Ni-Cu-platinum group element (PGE) sulphide ores. This geological belt hosts voluminous basaltic sills and lavas of the Montagnais Sill Complex, which are locally emplaced among sulphidic metasedimentary country rocks. The recently discovered Idefix PGE-Cu prospect represents a stack of gabbroic sills that host stratiform patchy disseminated to net-textured sulphides (0.2–0.4 g/t PGE+Au) over a thickness of ∼20 m, for up to 7 km. In addition, globular sulphides occur at the base of the sill, adjacent to the metasedimentary floor rocks. Whole-rock and PGE geochemistry indicates that the sills share a common source and that the extracted magma underwent significant fractionation before emplacement in the upper crust. To develop the PGE-enriched ores, sulphide melt saturation was attained before final emplacement, peaking at R factors of ∼10 000. Globular sulphides entrained along the base of the sill ingested crustally derived arsenic and were ultimately preserved in the advancing chilled margin.

Small intrusions dominated by olivine- and pyroxene-rich cumulates are well known to be favorable hosts to magmatic Ni-Cu-(Platinum Group Element—PGE) sulfide mineralization. Such intrusions are common in a variety of settings around the world, but only a very small proportion contain economically exploitable sulfides; these tend to be of conduit or chonolith style. If prospectivity could be discriminated from sparse sampling at early exploration stages, then the discovery rate for deposits of this type could be improved. To this end, a number of pyroxene-bearing samples from small intrusions containing magmatic sulfide deposits have been investigated including the Noril'sk-Talnakh camp in Siberia, the Kotalahti nickel belt in Finland, Ntaka Hill in Tanzania, Nova-Bollinger in the Albany-Fraser Orogen of Australia, Savannah in the Halls Creek Orogen of Australia, Jinchuan in central China, Xiarihamu in Tibet and Huangshanxi in the east Tianshan Ni province of NW China. To compare, samples from unmineralized intrusions in four of these regions were also investigated along with four mafic intrusions from other localities that are not associated with any known economic sulfide mineralization. Using fine-scale (

Nuclear power has the potential to provide significant amounts of reliable electricity generation without carbon dioxide emissions. Disposing of radioactive waste is, however, an ongoing challenge, and if it is to be buried, the characterisation of the regional groundwater system is vital to protect the anthroposphere. This aspect is understudied in comparison to the engineered facility; yet, selecting a suitable groundwater setting can ensure radionuclide isolation hundreds of thousands of years beyond that provided by the engineered structure. This paper presents a multi-faceted scoping tool to quantitatively assess, and directly compare, the regional hydrogeological prospectivity of different groundwater settings for disposal at an early stage of the site selection process. The scoping tool is demonstrated using geological data from three distinct UK groundwater settings as a case study. Results indicate a significant difference in the performance potential of different regional groundwater settings to ensure long-term waste containment.

Groundwater depletion and contamination has increased in recent decades due to increased groundwater use and the intensification of agricultural practices. The increasing demand for groundwater has increased the need to identify areas in a landscape where groundwater resources are most likely to be available. The present study was conducted on three management blocks in West Bengal in India where excessive groundwater use for agriculture primarily has caused groundwater levels to decrease. An AHP technique was employed to compile a groundwater resources potential map for the study area. The map was compiled using ten thematic layers including: geomorphology, slope, geology, landuse/landcover, rainfall, slope curvature, the Modified Normalized Difference Water Index, drainage density, soil type and the Topographic Wetness Index. The groundwater potential map has been validated using the groundwater fluctuation data and correlated with agricultural dependency on groundwater. The final potential map obtained categorized the regions into five categories. These are areas with a poor, low, moderate, high and very high prospectivity.

The main aim of this study is to determine the location of the cave and cavities in Zarrinabad area, Lorestan province, west of Iran. For this purpose, a combination of hybrid AHP-TOPSIS procedure and content-area (C-A) fractal method has been conducted on three types of geoelectrical data derived from electrical resistivity, self-potential and mise-a-la-masse methods to detect karstic zones and determining the geometry of the cavities. Initially, the raw values of the data were transformed to [0–1] domain using the MSlarge fuzzy function, and then the fuzzified values were discretized applying C-A fractal model to separate different geological populations (e.g., conglomerate and limestone layers as well as the geometry of the cave). Subsequently, the analytical hierarchy process (AHP) as the most widely used multiple criteria decision making (MCDM) technique was applied for calculating meaningful weights and then assigning them to different fractal-based classes of investigation criteria (here, triple geoelectrical data) based on the expert knowledge. A decision matrix based on the calculated weights were constructed and TOPSIS as another well-known MCDM technique was then employed for generating cave potential model of AHP-TOPSIS procedure. In addition, a fuzzy Gamma model (gamma = 0.9) based on three fuzzified electrical layers is implemented to assess the AHP-TOPSIS model. Finally, for the evaluation of generated models, electrical resistivity sections along profile 1, 2 and 3 were prepared. The results exhibit a strong spatial association between final prospectivity models, electrical resistivity sections and the outcrop of the cave on the surface. According to the obtained results, a cave with dimensions of several meters (for example, its length in one direction is up to 100 m) is appeared to be expanded from the north of the study area to the south. Besides, it is possible that the karstic zones contain a number of small cavities which are linked together like a beehive. Thus, this area can be considered as a good source of underground water due to the presence of these holes which often contain fresh water. In addition, this area is prone to convert into a tourism area in the future as this cave contains high level water especially in rainy seasons.

Antimony (Sb) is a critical metal for Europe. Indeed, Sb is widely used in a variety of industrial operations, especially in the European aircraft industry, such as production of flame retardants, plastics, paint pigments, glassware and ceramics, alloys in ammunition and battery manufacturing plants.Despite its strategic importance, the knowledge on Sb and its ore deposits remains poorly constrained. Moreover, Europe remains under the threat of an essentially Chinese supply despite a proven potential for European deposits that contain also strategic and precious co-products (W, Au). In parallel, Sb and associated metalloids (As, Hg, etc) are more and more recognised as a global threat for human health and it has been demonstrated that most of elevated concentrations of Sb on earth surface originate from natural, geogenic sources. Then, a first large-scale identification of these areas where primaries resources occur and metalloids can contaminate humans should be a priority.To achieve its objectives, the overall approach of the ERA-MIN2 AUREOLE project (2019-2022 - https://aureole.brgm.fr) is based on disruptive concepts: i) development of a 3D large-scale metallogenic model integrating deep-seated processes to determine the spatial distribution of ore deposits; ii) the use of mineral prospectivity data weighted by surface data to determine the probability of environmental risk over large areas.The work package (WP) 1 is dedicated to produce the new 3D deep-seated metallogenic model for antimony mineralisations and contribute to the global 3D understanding of the Sb mineralising processes. The WP2 is designed to the understanding of processes - such as geomorphology, weathering, climate - that control the mobilisation and transport of metalloids at the earth surface. The WP3 will use results from WPs 1 & 2 to produce large-scale mineral prospectivity and a large-scale environmental risk assessment by weighting mineral prospectivity with earth surface properties, such as DTM, rainfall, weathering cartographic maps, etc.The AUREOLE project will bring new scientific knowledge on Sb and Sb deposits, for a better mineral exploration targeting.The expected outcomes will be several high-impact deliverables devoted to the targeting of new Sb deposits and a new large-scale environmental assessment maps for decision-making dealing with humans health. Long term expected impacts would be an increase of EU Sb resources and EU Sb sustainable supply. Because of its implications for European critical metals, the AUREOLE project will provide new findings and results to the SCRREEN project (Solutions for Critical Raw Materials – a European Expert Network) and to the IMP@CT project (Integrated Mobile Modularised Plant and Containerised Tools for sustainable, selective, low-impact mining of small, high-grade or complex deposits). It will also interact with the Geo-ERA FRAME project (Forecasting and assessing Europe’s strategic raw materials needs).

There are a significant number of image processing methods that have been developed during the past decades for detecting anomalous areas, such as hydrothermal alteration zones, using satellite images. Among these methods, dimensionality reduction or transformation techniques are known to be a robust type of methods, which are helpful, as they reduce the extent of a study area at the initial stage of mineral exploration. Principal component analysis (PCA), independent component analysis (ICA), and minimum noise fraction (MNF) are the dimensionality reduction techniques known as multivariate statistical methods that convert a set of observed and correlated input variables into uncorrelated or independent components. In this study, these techniques were comprehensively compared and integrated, to show how they could be jointly applied in remote sensing data analysis for mapping hydrothermal alteration zones associated with epithermal Cu–Au deposits in the Toroud-Chahshirin range, Central Iran. These techniques were applied on specific subsets of the advanced spaceborne thermal emission and reflection radiometer (ASTER) spectral bands for mapping gossans and hydrothermal alteration zones, such as argillic, propylitic, and phyllic zones. The fuzzy logic model was used for integrating the most rational thematic layers derived from the transformation techniques, which led to an efficient remote sensing evidential layer for mineral prospectivity mapping. The results showed that ICA was a more robust technique for generating hydrothermal alteration thematic layers, compared to the other dimensionality reduction techniques. The capabilities of this technique in separating source signals from noise led to improved enhancement of geological features, such as specific alteration zones. In this investigation, several previously unmapped prospective zones were detected using the integrated hydrothermal alteration map and most of the known hydrothermal mineral occurrences showed a high prospectivity value. Fieldwork and laboratory analysis were conducted to validate the results and to verify new prospective zones in the study area, which indicated a good consistency with the remote sensing output. This study demonstrated that the integration of remote sensing-based alteration thematic layers derived from the transformation techniques is a reliable and low-cost approach for mineral prospectivity mapping in metallogenic provinces, at the reconnaissance stage of mineral exploration.

© 2020 by the authors. The exploration of carbonate-hosted Pb-Zn mineralization is challenging due to the complex structural-geological settings and costly using geophysical and geochemical techniques. Hydrothermal alteration minerals and structural features are typically associated with this type of mineralization. Application of multi-sensor remote sensing satellite imagery as a fast and inexpensive tool for mapping alteration zones and lithological units associated with carbonate-hosted Pb-Zn deposits is worthwhile. Multiple sources of spectral data derived fromdifferent remote sensing sensors can be utilized for detailed mapping a variety of hydrothermal alteration minerals in the visible near infrared (VNIR) and the shortwave infrared (SWIR) regions. In this research, Landsat-8, Sentinel-2, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and WorldView-3 (WV-3) satellite remote sensing sensors were used for prospecting Zn-Pb mineralization in the central part of the Kashmar-Kerman Tectonic Zone (KKTZ), the Central Iranian Terrane (CIT). The KKTZ has high potential for hosting Pb-Zn mineralization due to its specific geodynamic conditions (folded and thrust belt) and the occurrence of large carbonate platforms. For the processing of the satellite remote sensing datasets, band ratios and principal component analysis (PCA) techniques were adopted and implemented. Fuzzy logic modeling was applied to integrate the thematic layers produced by image processing techniques for generating mineral prospectivity maps of the study area. The spatial distribution of iron oxide/hydroxides, hydroxyl-bearing and carbonate minerals and dolomite were mapped using specialized band ratios and analyzing eigenvector loadings of the PC images. Subsequently, mineral prospectivity maps of the study area were generated by fusing the selected PC thematic layers using fuzzy logic modeling. The most favorable/prospective zones for hydrothermal ore mineralizations and carbonate-hosted Pb-Zn mineralization in the study region were particularly mapped and indicated. Confusion matrix, field reconnaissance and laboratory analysis were carried out to verify the occurrence of alteration zones and highly prospective locations of carbonate-hosted Pb-Zn mineralization in the study area. Results indicate that the spectral data derived from multi-sensor remote sensing satellite datasets can be broadly used for generating remote sensing-based prospectivity maps for exploration of carbonate-hosted Pb-Zn mineralization in many metallogenic provinces around the world.

Fuzzy modelling of multisource geoscience data and its implications to mineral prospectivity mapping is drawing wide attention of the mineral exploration sector. Mineral deposits are basically end products resulted from optimal combination of certain metallogenetically favourable earth processes which leave their imprints in the associated geological entities at a range of scales that can be interpreted from their direct or indirect manifestation in several geospatial datasets. Therefore, in geologically potential yet under-explored or greenfield areas with no or very few discovered mineral deposits, the qualitative knowledge on the spatial relationship between mineralisation of interest and geoscience data could be an important guide to delineate exploration targets. In such a case, fuzzy set theory aided with Geographic Information System (GIS) is preferred as an effective mechanism for the transformation of subjective knowledge into quantitative information that further helps in modelling of earth science data. The Archaean to Paleo-proterozoic Sonakhan Greenstone Belt (SGB) located in the north-eastern fringe of the Baster Craton in central India is considered as a potential geological terrane for mesothermal gold mineralisation based on its geological and geochemical similarities with other mineralised greenstone belts. In this case study, a part of SGB has been taken as a target area that exposes sequence of metamorphosed mafic to ultramafics rocks and associated metasedimentary units in a gneissic country and younger granites. Since the study area represents a less explored terrane in terms of mineralisation, the objective of this research is to generate gold prospectivity maps using fuzzy logic modelling. A total of 17 multiclass evidential maps were generated using four independent geoscience datasets viz. geological, geochemical, geophysical, and remote sensing. The sources of data include existing databases from the Geological Survey of India (GSI) and published work along with the newly produced exploratory data in this research. Fuzzy membership values (0-1) were assigned to each class of evidential maps based on subjective judgement. The fuzzyfied evidential maps were then combined using fuzzy operators (AND, OR, SUM, PRODUCT, and GAMMA) through a series of logical steps i.e. the fuzzy inference network. Two different fuzzy inference networks were created using several combinations of fuzzy operations and accordingly, two prospectivity maps resulted which were classified as very high, high, moderate, low, very low favourable zones. To further enhance the result, the two maps were intersected to produce the final gold prospectivity map in support of targeting gold exploration in the region. A part of the study area, that is the Baghmara gold block, that was already identified as a gold enriched block based on traditional exploration works, coincides with the very high to high favourable zones predicted in the final map and this ensures the reliability of the gold prospectivity map and the efficiency of the adopted fuzzy logic approach in delineating promising targets for exploration.

The prime aim of work package (WP) 3 in the FRAME project is to produce a map of Strategic and Critical Raw Materials (SCRM) for Europe, including the so-called energy and conflict minerals. In cooperation with other FRAME WPs, there was a consensus on the methodology used for the identification and selection process of the Strategic and Critical Raw Materials (SCRM) to be included in the metallogenetic map, linked mainly to information collected from existing databases (DB), such as Minerals4EU (M4EU) and European Geological Data Infrastructure (EGDI). One main objective of WP3 is the predictive targeting based on GIS exploration tools and prospectivity assessments at continental scale. Two types of prospectivity mapping have been produced in this WP3 based on different knowledge and data-driven methods. The first method applies the latest developments in “data driven” mineral prospectivity that allows mapping at continental scale, such as the “Cell Based Association" (CBA) one method developed by BRGM. CBA is an alternative to GIS-supported prospectivity methods. It has been developed to better manage uncertainties related to cartographic data which are highly significant at continental scale. The second method is using the hybrid fuzzy weights-of-evidence (WofE) model for mineral potential mapping.SCRM may be recovered either as primary commodities or as by-products. Carbonatite-related deposits are the primary sources of many CRM such as REEs, niobium (Nb) and tantalum (Ta). Granitic pegmatite deposits are currently the principal source of Ta. Compilation of Nb and Ta occurrences/deposits in Europe is currently going on within FRAME WP6 (see separate presentation by Reginiussen et al., this conference). The data has been used for the spatial analysis and prospectivity mapping related to geology and geotectonic and metallogenic setting at European scale.The results of our prospectivity mapping highlight several Nb and Ta mineral potential areas related to evolved granite to leucogranite bodies mostly in Scandinavia, Spain, France and Portugal, e.g Morille-Martinamor district, Fontão and Penouta where previous exploration activities on those elements were carried out in past. The late Neoproterozoic to early Cambrian Schist-Greywacke Complex (SGC) of the Variscan belt, in Central Iberian Zone, is also indicated as favourable area for Nb and Ta. Pegmatites in the Campo Mineiro De Lagares in the CIZ are another area of interest. Pegmatites in central Iberian zone is another area of interest, as is the case for Campo Mineiro De Lagares. The late Neoproterozoic to early Cambrian Schist-Greywacke Complex (SGC) of the Variscan belt, in Central Iberian Zone, is also indicated as favourable area for Nb and Ta. . In Sweden, the pegmatites of the Varuträskt area, close to Skellefteå, dated to c. 1.8-1.77 Ga, are clearly highlighted in the prospectivity maps. The areas related to Fennoscandian carbonatites appear also to be strongly favourable as Nb and Ta mineral potential targets. In the northern, central and southern parts of Sweden, high to moderately favourable areas are related to the numerous individual and granitic pegmatite dykes of Proterozoic age.

The rare earth elements (REEs) are a group of seventeen metals including 15 lanthanides, scandium and yttrium. These metals have been projected to be critical for future industrial development. However, India currently does not have any economic grade primary deposit of REEs; all of India’s production comes from monazite-bearing beach sands along the eastern and western coasts that have been derived from REEs-enriched continental rocks such as pegmatites or carbonatites. This contribution documents a GIS-based prospectivity model for exploration targeting of REE associated with carbonatites and alkaline-complexes in the geologically permissive tracts of NW India comprising parts of western Rajasthan and northern Gujarat. A mineral systems approach is applied to model the key ingredients of an REE system including geodynamic setting; fertile mantle/crustal sources of REEs; deep to shallow crustal architecture; and REE deposition. This conceptual genetic model of REE mineral systems is, in turn, used to identify the key regional-scale REE-deposit targeting criteria in NW India. Regional-scale multi-parametric exploration datasets are processed to represent the targeting criteria in form of predictor GIS layers. Finally, an expert-driven fuzzy inference system is designed for delineating and raking prospective REE targets. Simultaneously, the stochastic and systemic uncertainties in the prospectivity modeling are modelled to delineated (a) high priority REE exploration targets areas with low uncertainty and high prospectivity for immediate ground follow up and (b) areas with high uncertainty and high prospectivity for further data acquisition in order to reduce uncertainty.

The Axi low-sulfidation (LS) epithermal deposit in northwestern China is the result of geological controls on hydrothermal fluid flow through strike-slip faults. Such controls occur commonly in LS epithermal deposits worldwide, but unfortunately, these have not been quantitatively analyzed to determine their spatial relationships with gold distribution and further guide mineral prospecting. In this study, we conduct a 3D mineral prospectivity modeling approach for the Axi deposit involving 3D geological modeling, 3D spatial analysis, and prospectivity modeling. The spatial analysis of geometric features revealed the gold mineralization trends in convex segments (0&ndash, 20 m) with a specific distance from fault 2, the lower interface of late volcanic phase, and the upper interface of phyllic alteration with steep slopes (&gt, 65&deg, ), implying that gold deposition was significantly controlled by the morphological characteristics and distance fields of geologic features. The present alteration&ndash, mineralization zone at Axi has a larger width in bending sites (sections No. 35&ndash, 15 and No. 40&ndash, 56) than elsewhere, indicating the location of two fluid conduits extending to depth. The prediction-area plots and receiver operating characteristic curves demonstrated that (genetic algorithm optimized support vector regression (GA-SVR)) outperformed multiple nonlinear regression and fuzzy weights-of-evidence, which was proposed as a robust method to solve complicated nonlinear and high-dimensional issues in prospectivity modeling. Our study manifests spatial controls of structure, host rock, and alteration on LS epithermal gold deposition, and highlights the capability of GA-SVR for identifying deposit-scale potential epithermal gold mineralization.

Summary Extraction of hydrocarbon from shale gas reservoirs always presents challenges due to their extremely low permeability and hence production depending totally on natural and induced fractures. Geomechanics is of vital importance for shale gas prospectivity evaluation in terms of brittleness and anisotropy. The research objective is to evaluate the prospectivity of Qusaiba Shale by delineating brittle zones/layers. This study also quantifies the anisotropy leading to accurate determination of hydraulic fractures orientation. The log data, including sonic (P and S-waves), density, and mineralogy logs for about 950 feet thick shale interval, were used to calculate the brittleness index. Brittleness index was determined based on two approaches: elastic parameters and mineralogy. Thomsen parameters and Schoenberg model were used to investigate the anisotropy. Both approaches for brittleness estimation revealed that Qusaiba Shale is composed of alternating brittle and ductile layers. The comparison of results revealed that the quartz rich layers exhibit high Young’s Modulus and low Poisson’s ratio in terms of high brittleness index. Anisotropy analysis revealed high degree of P and S wave anisotropy. The study emphasizes the importance of the role of brittleness and anisotropy analyses in prospectivity evaluation of Qusaiba Shale and assist in optimum designing of completion stages.

West Africa’s maritime regions, including its onshore and offshore basins and rifts, are experiencing an unprecedented expansion in oil exploration and development as a result of their proven hydrocarbon reserves and high prospectivity. Along the stretch of coastline between the Senegal basin in the north right down to the more profitable Gulf of Guinea and on to southwest Africa, more than 500 oil (and gas) companies from various Western countries and from as far away as India, Malaysia, and Singapore are participating vigorously in the upstream (exploration, discovery, development, and production) and downstream activities (refining, marketing, and shipping) of one of the most important commodities in international trade. In addition to the traditional oil-producing and exporters, such as Nigeria and Angola strengthening their capacity, major new and significant producers have now emerged including Ghana, Equatorial Guinea, and Sao Tome and Principe. There have also been significant new offshore discoveries in Cote d’Ivoire and the under-explored Senegal basin, in the northern tip of West Africa. As a result of this frenetic exploration activities, the region is witness to frequent new basin openings and relatively high discovery success of ‘sweet crude’, one of the world’s most coveted type of crude oil. The subregion, once viewed largely through the prism of Nigerian oil, sub-Saharan Africa’s largest oil producer, is now a central part of the global energy economy, largely due to its ongoing widely dispersed commercially profitable oil finds. The region is projected to increase its crude oil production from 1935.90 in 2018 to 3006.24 thousand barrels per day in 2024. As widespread prospecting and drilling for commercial oil takes hold across the subregion however, concerns are being raised about the rapacious and non-consultative manner of exploitation and its implications for good governance, development, human security, and stability.

International audience; Geodynamic models, geological-geophysical interpretations, and isotope analysis illustrate that there are links between the nickel and gold mineral systems in the Halls Creek Orogen, Western Australia. Whole-rock Nd and 40Ar/39Ar analysis of rocks throughout the region, when compared with the geodynamic models suggest that nickel and gold mineralization in the Halls Creek Orogen can be related to basin development and subsequent basin closure during the convergence of North Australian Craton and Kimberley Craton, respectively. Whole-rock Nd analysis confirmed the input of juvenile melts in the centre of the orogen before the 1835–1805 Ma Halls Creek Orogeny, supporting the upwelling of decompression mantle melts during the basin development. These analyses also revealed the spatial links between nickel and gold mineralization and lithological units with positive εNd values. Spatially the link between these mineral systems appears to be related to the presence of deep-seated shear zones that formed early in the history of the orogen and were later reactivated. The results of geodynamic models, geophysical interpretation, and isotopic analysis are used to understand the critical processes in the gold and nickel mineralization, which are presented by predictor maps. The GIS-based knowledge-driven fuzzy logic method used to integrate the predictor maps and create the prospectivity maps. Herein we show that mafic-ultramafic units prospective for nickel mineralization formed by upwelling of decompression mantle melt during crustal thinning and extension during basin development, and typically consist of the most juvenile magmas in the region. Whereas, gold deposits formed during the compressional regime and basin closure, and are located along a major shear zone separating two terranes. This deep crustal-scale shear zone is implied to be the site of multiple stages of deformation that acted as fluid migration pathways during basin closure and subsequent collision. Another critical element that appears to be related to gold prospectivity is the presence of lithologies with a juvenile signature. In contrast to nickel analyses which are closely related to mafic-ultramafic units, the source component seems less influential when attempting to target orogenic gold deposits.

[Abstract A glossary of commonly used terms related to the geometric forms and geological settings of basement highs is presented to assist cross‐disciplinary understanding, qualifying prefixes for the term basement are discussed and a scheme for characterising basement highs is presented. This scheme is designed to standardise, and to add rigour to, description of basement highs. It will thereby enhance basement high comparisons and assist understanding of basement highs across technical disciplines. The scheme enables systematic characterisation of: the geometry of a basement high; the lithologic units and structures in, above and around it; timings; tectonics and origins of the basement high and play elements relating to resource prospectivity. Use of this scheme is demonstrated using the southern Rona Ridge (West of Shetland, UK Continental Shelf). The tectonic, isostatic, erosional and stratigraphic processes that form basement highs are also discussed, and examples in proven petroleum systems are presented., Example of geometric features of a basement high, illustrated using the south Rona Ridge 3D Top Basement depth structure map. A = Lancaster Field oil‐water contact at 1678 m true vertical depth sub sea level (TVDSS) (Hurricane Energy, 2019c). B = Lincoln oil discovery “oil down to” at 2258 m TVDSS. C = Whirlwind Discovery “oil down to” at TVDSS. The basement high covers an area of ~ 1200 km , so it is a 4th order basement high. It has an approximately trapezoid shape in map view shape (including the Whirlwind downthrown block). The topography of the upper surface can be described as an undulating wedge (area i) and an undulating planar slope (areas labelled ii). Structures segmenting the basement high include: 1 = Westray Fault Zone; 2 = Brynhild Fault Zone. Contour increment 100 m. ]

Summary Lithium, cobalt and natural graphite are essential for energy storage technologies. Their demand is expected to surge with the increasing electrification in the transport sector. As they are all produced outside Europe, their supply for the European industry is potentially a threat. To address this, the FRAME project has produced prospectivity maps for Li, Co and Gr, to identify high potential mineral areas in Europe. They were calculated with the Cell Based Association (CBA) method, developed to better manage uncertainties related to cartographic data, often significant at continental scale. The base principle is to identify the associations of evidential features in the cells of a regular grid. Several techniques for scoring the favourability of the cells were tested. A prospectivity map was then calculated for each commodity (Co, Li and Gr) with the 1:1.5 million geological map of Europe, a regular grid of 10 by 10 km cells covering the whole Europe and the most performant scoring technique. These maps highlights favourable areas for the discovery of new energy critical elements deposits in Europe, and are valuable outputs of the FRAME project that help assessing highly prospective areas where mineral exploration should be focused in the coming years.

Summary A 3D seismic data set has been acquired at the Blotberget iron-oxide mining site of the Bergslagen mineral province in central Sweden. A 3D focusing seismic imaging technique accompanied by 3D first-arrival traveltime tomography to obtain a P-wave velocity model of the shallow subsurface have been applied to the 3D data set after basic pre-processing. As a result, a high-quality 3D seismic cube with several dominant structural features has been obtained in depth. One distinct reflector can be related to the southeast dipping mineralisation and a major conjugate reflector with opposite dip crosscuts this mineralisation reflector at greater depth. Our findings verify earlier studies based on 2D seismic profiles in that area and, beside a significantly improved data quality, now also provide 3D structural information about the true spatial dips of the imaged structures. The high-resolution 3D seismic cube serves as a good basis for building a 3D model of the deposit and its internal architecture including future prospectivity modelling to estimate its economic potential.

Summary The discovery of the Rosebank oil and gas field in the NE Atlantic has identified inter-basalt reservoirs as significant targets for future exploration. Top and Base Basalt and numerous overlying amplitude anomalies are mapped on 3D seismic data in two study areas: West of Shetland (UK) and the outer Voring Basin (Norway). We describe seven undrilled elongated ridge structures which are defined at Top Basalt level. Above these ridges are stacked amplitude anomalies interpreted to be caused by hydrocarbon leakage. In the Voring Basin seabed sampling finds that both oil and gas seeps occur at the seabed above these anomalies. In the West of Shetland area, well data from Tobermory (214/4-1) and Bunnehaven (214/9-1) as well as a seismic well-tie indicates that the basalt sequences at the two wells are diachronous. Seismic interpretation shows that the basalt sequences overlie each other and that a clastic sand-rich unit observed at both wells potentially extends between the basalt units. Four of the basalt ridges occur where the sand-rich unit observed at the two wells could be an inter-basalt reservoir. Overlying amplitude anomalies suggest the reservoir may be charged.

Summary Detailed prospecting studies were carried out in Kikombo, Dodoma, Central Tanzania to examine the possible mineralization zones through delineating subsurface structures and characterizing geochemical distribution of various elements by integrating the results of the methods applied. The prospecting methods utilized include geological methods, regional aeromagnetic survey, local ground magnetic survey, airborne gravity survey, induced polarization survey and geochemical survey. Geological observation shows the area’s underneath geology to be composed of tonalitic — orthogneiss rock types whose regolith is composed of brown sand which is light as well as reddish. Gravity survey results suggest high gravity anomaly to most of the occupied area. Aeromagnetic surveys reveal high magnetic anomaly to most of the occupied area with NE-SW structural trending patterns. Local ground magnetic survey reveals to lack prominent structures (faults) that are deep and localized, however, the shallow structures were revealed showing similar trend of NE -SW. The depth to the magnetic anomaly of various methods employed goes up to 494.1 m. IP results indicate high resistive and chargeable bodies at the basement with some faults striking NE-SW. Geochemical survey shows the concentration of elements such as As, Au, Ca, Cr, Cu, Fe, K, Mg, Mn, P, S, Ti, V, Zn and Zr while suggesting a strong positive correlation of Mn and Cu.

Summary The prime focus of mineral prospectivity mapping (MPM) is the identification, delineation and level of potential for an area to host feasible mineral resources. In general, GIS-based MPM can be either data driven or knowledge-driven. Methods of data-driven MPM, which involve quantitative analysis of spatial relationships among anomalies (i.e., indicators of mineralization) and existing occurrences of mineral deposits of the type sought, is suitable for “brownfields” or well-explored regions, wherein the objective is to define additional targets for exploration. One of the main objectives of WP3 in the FRAME project (www.frame.lneg.pt) is to produce a map of Strategic and Critical Raw Materials (SCRM) for Europe. Another objective is to produce predictive targeting based on GIS exploration tools at continental scale. in this presentation we will review the state of the art for the MPM and show example of the favourability maps using CBA method and hybride fuzzy weight of evidence produced in the FRAME project. This methodology represents different development stages, scales and progress of economic geology surveys which could be a tool to improve effectiveness and efficiency of future investments in exploration. Improved understanding and support for a balance management of competitive land-usage interests is an additional benefit.

This chapter presents case studies on the application of nonconventional exploration techniques from Africa and Asia. The first case study is on the Kabanga Ni–Cu sulfide deposit using mainly the work of Macheyeki. In this case study, procedures on how to obtain lithogeochemical vectors are given along with their limitations. The second case study elucidates the use of Mineral Prospectivity modeling on ore field scale and at Prospect scale, in the Yangtze Metallogenic Belt, China by Li et al. and Yuan et al. In this study, workflows of 3D geological and mineral prospectivity modeling are presented. The third case study is on the use of multifractal modeling for identification of Cu and Au geochemical anomalies in northern Xinjiang Province, China. It is the belief of the authors that such case studies could be extended to other parts of the world having similar geological settings.

In this paper, we present an integrated landform-regolith mapping protocol/chart for West Africa developed using a case from Central Burkina Faso. The chart accounts for (i) the specificities of the ubiquitous, duricrust-capped remnants of the regional paleolandsurfaces – particularly the residual or detrital character of the Fe duricrusts – and (ii) the diversity of the remaining, non-duricrusted portions of the landscape, with an emphasis on the pitfalls encountered in determining the in-situ or transported character of the regolith. The paper also provides field identification criteria and illustrations of the typical West African landform-regolith associations. The landform-regolith mapping chart is integrated into a prospectivity chart, which is used to define exploration guides: (i) defining sampling strategies, (ii) interpreting potential geochemical anomalies and (iii) targeting lateral extensions of known bedrock mineralizations. The mapping protocol further allows for the definition of a class of landform-regolith association propitious to supergene mineral concentrations. The mapping protocol is shown to be transposable to wetter contexts and, more generally, to other tropical shield provinces.

Post 9/11 USGS research on the prospectivity, or mineral potential mapping, of Afghanistan’s mineral wealth led commentators, governments and the US military to promote the mineral resources of Afghanistan as enough to fundamentally alter the Afghan economy and perhaps the Afghan war itself. Afghanistan’s prospectivity however was of little surprise to economic geologists and is some of the most highly prospective ground in the world.

Knowledge of the in situ stress state of the Earth's crust plays a key role in understanding geological processes including plate tectonics, earthquakes, slope failure, and igneous emplacement. In this paper, we determine the in situ stress orientation from the PTA2 borehole on the island of Hawai'i, drilled into a lava flow dominated sequence between Mauna Kea and Mauna Loa. High‐resolution acoustic images were collected from the open hole interval 886 m to 1,567 m. Based on identification of 371 borehole breakouts for a total length of 310 m, the mean orientation of the minimum horizontal principal stress is N106° and remains constant across different volcanic rock fabrics. Changes in borehole breakout shape are linked to the different strength of volcanic facies and intra‐facies. The orientation of the present‐day stress field at Mauna Kea deviates from the plate forces and regional tectonic stress field. We interpret the compressive stress regime at the PTA2 site as resulting from the competing gravitational fields of the large topographic highs of Mauna Kea and Mauna Loa. Our study reveals that the mass accumulation associated with shield volcano growth imparts significant local variations to the subsurface stress state on volcanic islands consisting of overlapping shield volcanoes. The results have significant implications for stress accumulation leading to brittle failure and flank collapse, along with potentially influencing magma accumulation and ascent pathways during volcanic island evolution. This study provides the first insights into the orientation of the present‐day stress field between the major island forming shield volcanoes of Hawai'i.

Summary Machine learning continues to advance technologies across a broad network of industries. For natural resources specifically, we have developed a general machine learning algorithm (VNet) and successfully applied it to a wide variety of problems. These include mineral and water prospectivity mapping in 2D, 3D, or 4D, airborne induced-polarization detection, airborne EM regression and segmentation, geologic mapping, structural geology prediction and interpretation, borehole and grade classification, and seismic segmentation and horizon picking. These new developments use deep convolutional neural networks to rapidly detect subtle and complex patterns across many geoscience data layers and spatial scales, in order to provide deeper insights to the geoscientist.

The multi-element aqua regia National Geochemical Survey of Australia (NGSA) database is used to demonstrate an improved method for quantifying the degree of geochemical similarity (DOGS2) between soil samples. The improvements introduced here address issues relating to compositional data (closure, relative scale). After removing the elements with excessive censored (below detection) values, the rank-based Spearman correlation coefficient (rs) between samples is calculated for the remaining 51 elements. Each element is given equal weight through the rank-based correlation. The rs values for pairs of samples of known similar origin (e.g. granitoid-derived) are significantly positive, whereas they are significantly negative for pairs of samples of known dissimilar origin (e.g. granitoid- v. greenstone-derived). Maps of rs for all samples in the database against various reference samples are used to obtain correlation maps for lithological derivations. Likewise, the distribution of soils having a geochemical fingerprint similar to established mineralized provinces can be mapped, providing a simple, first order mineral prospectivity tool. Sensitivity of results to the removal of up to a dozen elements from the correlation indicates the method to be extremely robust. The new method is compliant with contemporary compositional data analysis principles and is applicable to various digestion methods.

Global exploration has seen a dramatic upturn in 2018, with close to 4 billion barrels of oil equivalent discovered in the first half of the year alone, and many exciting wildcat wells still to come. Although the oil price slide of 2014 changed the industry, with the focus now on commerciality and risk reduction, it is of interest that most of the new discoveries this year have been made in commercially challenging deep water. The reason for this is that our industry has been exploring shallow-water oil-prone basins since the invention of marine seismic methods in the 1950s, and they appear now to be ‘mature’ and depleted in material low-risk opportunities. Indeed the future of shallow-water exploration has been portrayed as binary: either mopping up around what we know or exploring new frontiers. However, in South Gabon we challenge the established idea that after 50 years of exploration the basin is mature, by revealing a new generation of prospectivity with modern 3D acquisition and processing (Figures 1 and 2). The play primarily chased so far has been the Gamba Sandstone play, the seismic imaging of which has always been a significant challenge, owing to the complex velocities in the post-salt geology, the heterogeneity and the halokinesis of the Ezanga Salt. Yet with the exception of the Muruba-2 discovery, few wells have deliberately targeted the syn-rift section below the Gamba, leaving the pre-salt section completely unexplored (Figure 1). Diligent planning and acquisition (Esestime et al., 2017, 2018) of 3D data in South Gabon covering an area eight times the size of Greater London (11,500 Km2), has enabled an imaging veil to be lifted. The intra-syn-rift is now visible and is revealing large-scale hydrocarbon prospects, capable of attracting interest from global exploration players (Figure 3).

The Tangbale-Hatu belt (western Junggar region), located in the Central Asian Orogenic Belt (CAOB), has undergone complicated accretion and collision processes during the evolution of the Paleo-Asian Ocean. The geological events contributed to orogenic gold mineral systems in the region. In the present study, mineral systems approach was employed to evaluate critical ore-forming processes such as fluid migration pathways, the formation of trap zones, and deposition of metals. By means of translating these critical processes into mappable ore-controlling variables, we attempt to establish a process-based quantitative evaluation model. A maximum entropy (MaxEnt) model was proposed to predict the potential distribution of orogenic gold deposits based on known gold deposits/occurrences, and ore-controlling variables. Nine ore-controlling variables including fault intersection density, fault linear density, the first factor score map, Au singularity indices, Au regional anomaly, Au local anomaly, proximity to NE-trending faults, proximity to intrusion contacts and proximity to stratigraphic contacts, were selected to identify the most potential zones endowed with gold deposits. The spatial association of individual ore-controlling variable with the incidence of gold deposit occurrences was investigated by response curves, and the relative importance of each ore-controlling variable was determined by jackknife analysis in the MaxEnt model. The results indicate that Au regional anomaly derived from spectrum–area (S–A) fractal model is the most important variable, followed by the first factor score map and proximity to stratigraphic contacts. The model accuracy was evaluated by ROC curve giving a high predictive ability (AUC = 0.915). Favorable zones for gold mineralization illustrated by the prospectivity map are spatially coincident with known gold deposits/occurrences and the main mineralized trends, showing that the MaxEnt model can be efficiently employed for spatial fusion analysis of multisource geospatial data to support conceptual mineral systems modeling of geologic controls on mineral deposit occurrences.

Upper Permian (Zechstein Supergroup) evaporites have a major control on structural styles and prospectivity in the UK Southern North Sea (SNS). They form the regional super-seal for the main Rotliegend Group (Leman Sandstone Formation) reservoir play fairway immediately beneath. The evaporites have highly variable thicknesses due to the syndepositional basin architecture, differential loading and post-depositional deformation through diapirism and salt withdrawal. The halokinetic activity leads to touchdown (welding) of the supra-salt section onto the sub-salt strata and the development of narrow (up to 15 km-wide) graben systems. The interpretation and depth conversion of well-calibrated, high-quality, 3D post-stack time-migrated (PSTM) seismic data along the southwestern margin of the basin show that a NW–SE-striking elongate extensional Dowsing Graben System transects the area. The graben is defined by a series of large, overlapping, en echelon listric growth faults, with oblique secondary planar faults, which sole-out on two main (deep and shallow) decollement levels in the Zechstein Supergroup and the Middle Triassic Rot Halite Member. Whilst its initial formation was related to Mesozoic extension, the graben system also displays a contractional overprint resulting from regional compression and structural inversion during the Cenozoic. Detailed mapping of the Zechstein Supergroup has revealed that the evolution of the extensional system was influenced by the ESE–WNW-striking anhydrite–carbonate Zechstein shelf-margin. The occurrence of variable-thickness, low-velocity sediments within the graben impacts seismic imaging and depth conversion, leading to prospective structures being overlooked; something that has implications for prospectivity in the SNS and other evaporite basins where similar graben occur.

Novel mineral prospectivity modelling presented here applies knowledge-driven feature extraction to a data-driven machine learning approach for tungsten mineralisation. The method emphasises the importance of appropriate model evaluation and develops a new Confidence Metric to generate spatially refined and robust exploration targets. The data-driven Random Forest™ algorithm is employed to model tungsten mineralisation in SW England using a range of geological, geochemical and geophysical evidence layers which include a depth to granite evidence layer. Two models are presented, one using standardised input variables and a second that implements fuzzy set theory as part of an augmented feature extraction step. The use of fuzzy data transformations mean feature extraction can incorporate some user-knowledge about the mineralisation into the model. The typically subjective approach is guided using the Receiver Operating Characteristics (ROC) curve tool where transformed data are compared to known training samples. The modelling is conducted using 34 known true positive samples with 10 sets of randomly generated true negative samples to test the random effect on the model. The two models have similar accuracy but show different spatial distributions when identifying highly prospective targets. Areal analysis shows that the fuzzy-transformed model is a better discriminator and highlights three areas of high prospectivity that were not previously known. The Confidence Metric, derived from model variance, is employed to further evaluate the models. The new metric is useful for refining exploration targets and highlighting the most robust areas for follow-up investigation. The fuzzy-transformed model is shown to contain larger areas of high model confidence compared to the model using standardised variables. Finally, legacy mining data, from drilling reports and mine descriptions, is used to further validate the fuzzy-transformed model and gauge the depth of potential deposits. Descriptions of mineralisation corroborate that the targets generated in these models could be undercover at depths of less than 300 ​m. In summary, the modelling workflow presented herein provides a novel integration of knowledge-driven feature extraction with data-driven machine learning modelling, while the newly derived Confidence Metric generates reliable mineral exploration targets.

Following a regional reconnaissance stream sediment survey that was carried out in the northern Vosges Mountains in 1983, a total of 20 stream sediment samples were collected with the aim of assessing the regional prospectivity for the granite-hosted base and rare metal mineralisation of the northern Vosges magmatic suite near Schirmeck. A particular focus of the investigation was the suspected presence of W, Nb and Ta geochemical occurrences in S-type (Kagenfels) and I-S-type (Natzwiller) granites outlined in public domain data. Multi-element geochemical assays revealed the presence of fault-controlled Sn, W, Nb mineralisation assemblages along the margins of the Natzwiller and Kagenfels granites. Characteristic geochemical fractionation and principal component analysis (PCA) trends along with mineralogical evidence in the form of cassiterite, wolframite, ilmenorutile and columbite phases and muscovite&ndash, chlorite&ndash, tourmaline hydrothermal alteration association assemblages in stream sediments demonstrate that, in the northern Vosges, S-type and fractionated hybrid I-S-type granites are enriched in incompatible, late-stage magmatic elements. This is attributed to magmatic fractionation and hydrothermal alteration trends and the presence of fluxing elements in late-stage granitic melts. This study shows that the fractionated granite suites in the northern Vosges Mountains contain rare metal mineralisation indicators and therefore represent possible targets for follow-up mineral exploration. The application of automated mineralogy (QEMSCAN&reg, ) in regional stream sediment sampling added significant value by linking geochemistry and mineralogy.