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• Discussion of mineral prospectivity modelling as a targeting tool. • Practical issues that limit the effectiveness of mineral prospectivity modelling. • Recommendations for a more effective prospectivity modelling process. Despite many decades of development, spatial prospectivity modelling is not yet widely used or accepted throughout the global mineral exploration industry. A common criticism of the method is that it is not practically useful because it has a bias to mature, well-known areas and generates excessively large areas of high-prospectivity. It is suggested that the reason for this is not primarily related to limitations in the prospectivity mapping algorithms but rather to issues relating to the use of input data sets. Specifically, it is common that the input data (such as geological interpretations) do not uniformly and objectively represent the search space of interest, omit critical targeting-relevant geoscientific elements (such as major, deep-seated ore-controlling structures) and have a large degree of unrecognised dependence. It is considered that these problems are not in principle barriers to the eventual successful deployment of this technology. However, future approaches to spatial prospectivity modelling need to explicitly address these concerns. It is suggested that the most effective method may be a hybrid of subjective human geological interpretation and objective, machine-based analysis, that captures the best aspects of these alternative approaches; i.e., an intelligence amplification (IA) rather than an artificial intelligence (AI) approach. A roadmap is proposed for improving the effectiveness of spatial prospectivity modelling that has implications for the broader community interested in mineral exploration targeting. [ABSTRACT FROM AUTHOR]

Formation of hydrothermal mineralization is related to the late stages of, or immediate following, orogenic compressional regimes that have been superimposed on arc magmatism. For instance, mineralization-related fluid flux mechanisms of porphyry Cu formation deal with how magmatic fluids are transferred from the corresponding source chambers to the environment of stock emplacement related to porphyry systems. In this paper, firstly, we review the imperative physicochemical processes of mineralizing fluid flux mechanisms, e.g., the function of intrusive, metalliferous compounds, and permeable structures, and then assemble them to translate the mechanism of forming focused fluid flux into 2D mappable criteria for mineral exploration targeting. According to the review and the ensuing knowledge and idea, we propose a simplifying approach by focusing on a geological point feature - inferred sites of strongly concentrated ore fluid flux - that represents a critical, if not the most critical, geological element in mineral exploration targeting. We demonstrate that this point feature can be derived as a mappable criterion and that there are stronger spatial and thermal relationships between the location of hydrothermal mineral deposits and this proposed point feature relative to the existing point and line features (e.g., intrusive contacts, fault density, fault intersections, and proximity to faults), which have been widely used in the procedure of prospectivity analysis for mineral exploration targeting. We illustrate the procedures of generating mineral exploration targets, proposed in this paper, using geochemical and geological data sets of porphyry Cu deposits of Iran. [Display omitted] • Function of hydrothermal mineralization-related focused fluid flux is discussed. • The function is translated into a newly-explored mappable exploration criterion. • The mappable criterion mitigates the problem of localizing hydrothermal mineralization. • Geochemical and geological data sets are applied in the modeling procedure. • Physicochemical ore-forming processes are discussed. [ABSTRACT FROM AUTHOR]

The punctuated distribution of major gold deposits along orogenic belts is poorly understood. In northern Perú, gold deposits cluster along trends that transect the subparallel Phanerozoic belts that accreted onto the western margin of the Archean--Proterozoic Amazonian craton. This suggests the influence of as yet unrecognized pre-Andean basement structures in controlling the localization of Phanerozoic deposits. We report the newly discovered Tomac ophiolite, which represents a missing link in tracing a cryptic basement collisional suture striking obliquely to the Peruvian Andes. The Tomac ophiolite signals the opening of a former Neoproterozoic ocean basin between the Amazonian craton and a continental ribbon of dispersed microterranes. Re-accretion of the continental ribbon resulted in the formation of a collisional belt between ca. 465 and 440 Ma. Rifting and re-accretion occurred parallel to the strike of the ca. 1400-1000 Ma Grenvillian-Sunsás orogen, indicating that structural corridors that transect the Andes at an oblique strike angle reflect inheritance of preexisting lithospheric weak zones. Our study demonstrates that Phanerozoic gold deposits in northern Perú cluster at the intersection between the newly defined basement suture and the superimposed Andean belt and associated well-documented cross faults. Gold mineralization was localized at ancient structural intersections, where enhanced permeability facilitated anomalous energy and mass transfer, promoting major ore accumulation during episodes of accretion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Survival bias concept is adapted for mineral exploration. • Next generations of mineral deposits are defined. • Analysis of the exploration search spaces in terms of Null and Negative tests is proposed. • Targeting mineral deposits of the future is discussed. • The findings have implications for the future development of exploration information systems. Broad consensus exists amongst mineral explorers that most outcropping mineral deposits have been found. The next generation of discoveries will rely on our ability to recognize the subtle or cryptic signals of deep-seated deposits. Exploration targeting under such conditions requires greater knowledge of the processes that formed the targeted mineral deposit types and new or improved exploration methods designed to effectively test for buried mineralization. Survival bias is a form of selection bias that is defined as the logical error resulting from neglecting data or information because of their "lack of visibility". In this study, "lack of visibility" refers to situations where (i) mineral explorers ignore or overlook particular terrain because it lacks or contains only weak signals of a mineralizing system, and (ii) such areas are excluded from further exploration as the existing data or information neither confirm nor support the targeting model. Therefore, it is critical to more comprehensively analyze a search space to more confidentially determine whether a terrain without the desired targeting signals satisfies the criteria of a null or negative test. The idea for this study is based on the notion that if a buried mineral deposit was present in an overlooked terrain it would nevertheless comprise distinctive geological features and targeting signals to guide the explorer, although, more likely than not, these signals would be very weak. Here we used a porphyry copper (Cu) district in Iran to explain and illustrate the adaptation of the survival bias concept. More specifically, in this study we tested the usefulness of a recently proposed targeting criterion, namely sites of potential focused fluid flux, as an input to mineral prospectivity analysis and exploration targeting. The findings of our study have implications for the future development of regional- to global-scale exploration information systems (EIS), designed to improve the performance of mineral exploration targeting. [ABSTRACT FROM AUTHOR]

Abstract: Holistic mineral systems approaches are being increasingly adopted in the study of ore deposits but application in industry has been suboptimal, because of the lack of a conceptual framework to help translate the mineral system understanding to practical application. A four-step process is proposed for linking the conceptual mineral system with data available to support exploration targeting. These steps include translation from (1) critical processes of the mineral system, to (2) constituent processes of the mineral system, to (3) targeting elements reflected in geology, and (4) targeting criteria used to detect the targeting elements directly or by proxy. This translation process is illustrated using examples from komatiite-hosted Ni–Cu–PGE and orogenic Au mineral systems. Ranking of targets must be at the critical process level, rather than the current practice of mixing processes, elements and proxies. The significance of targeting elements and their mappable criteria changes as a function of the scale at which the critical processes operate and the availability of relevant geoscience datasets. This scale dependence is rarely recognised in current practice. Sources of uncertainty when translating the mineral system understanding into an effective exploration targeting system include: (1) resolution of a mappable criterion in a dataset, (2) how well the targeting criterion reflects the targeting element, (3) how well the targeting element reflects the critical process and (4) whether the process being mapped is critical for the genesis of a mineral deposit. The first three sources of uncertainty collectively are termed the representativeness of the targeting criteria (i.e., how representative is a mappable criterion of the constituent process for which it is a proxy). The last source of uncertainty reflects our lack of understanding of the processes that control mineralisation, and highlights areas for further research. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution global seismic tomography (Vs) models reveal high-velocity domains beneath cratonic crust in Africa that extend to depths of 300–400 km. These high-velocity domains show a distinct contrast with the characteristics of “normal” asthenosphere and are interpreted as depleted, buoyant roots that formed in the Archean and have been metasomatised over time, but have remained attached to the overlying crust. Such deep roots are impediments to free horizontal convection in the upper mantle. The movement of magmas and other fluids in such regions may be more vertically constrained (a shallow lava lamp regime), creating a geodynamic environment conducive to interaction of such magmas with the boundaries of deep mantle domains that would carry old “crustal” geochemical signatures. The tomographic models and the new world magnetic-anomaly map show that these continental roots, overlain by thinned continental crust, locally extend well out under the deep Atlantic Ocean basin. However, such high-velocity domains are not confined to the basin margins, but are scattered randomly through the basin, some quite distant from the continental margins of South America and Africa. These high-velocity domains are interpreted to be remnant lithospheric fragments isolated by disruption of the ancient continental regions during rifting. This interpretation is supported by the old Os depletion ages of mantle peridotites from mid-ocean ridges and oceanic islands. Basaltic magmas near such high-velocity domains carry the geochemical signatures (EM1, EM2) of interaction with refertilised cratonic mantle. The interaction of rising magmas with fragments of ancient lithospheric mantle can explain such geochemical signatures and obviates the need for complex models in which these geochemical reservoirs are isolated and preserved in the convecting mantle. [Copyright &y& Elsevier]

Abstract: Continental flood basalts, derived from mantle plumes that rise from the convecting mantle and possibly as deep as the core–mantle boundary, are major hosts for world-class Ni–Cu–PGE ore deposits. Each plume may have a complex history and heterogeneous composition. Therefore, some plumes may be predisposed to be favourable for large-scale Ni–PGE mineralisation (“fertile”). Geochemical data from 10 large igneous provinces (LIPs) have been collected from the literature to search for chemical signatures favourable for Ni–PGE mineralisation. The provinces include Deccan, Kerguelen, Ontong Java, Paraná, Ferrar, Karoo, Emeishan, Siberia, Midcontinent and Bushveld. Among these LIPs, Bushveld, Siberia, Midcontinent, Emei Mt and Karoo are “fertile”, hosting magmatic ore deposits or mineralisation of various type, size and grade. They most commonly intruded through, or on the edges of, Archaean–Paleoproterozoic cratonic blocks. In contrast, the “barren” LIPs have erupted through both continental and oceanic crustal terranes of various ages. Radiogenic isotopic signatures indicate that almost all parental LIP magmas are generated from deep-seated mantle plumes, and not from the more widespread depleted asthenospheric mantle source: this confirms generally accepted plume models. However, several important geochemical signatures of LIPs have been identified in this study that can discriminate between those that are “fertile” or “barren” in terms of their Ni–PGE potential. The fertile LIPs generally contain a relatively high proportion of primitive melts that are high in MgO and Ni, low in Al2O3 and Na2O, and are highly enriched in most of the strongly incompatible elements such as K, P, Ba, Sr, Pb, Th, Nb, and LREE. They have relatively high Os contents (≥0.03 to 10 ppb) and low Re/Os (<10). The fertile LIP basalts display trends of Sr–Nd–Pb isotopic variation intermediate between the depleted plume and an EM1-type mantle composition (and thus could represent a mixing of these two source types), and have elevated Ba/Th, Ba/Nb and K/Ti ratios. These elemental and isotopic signatures suggest that interaction between plume-related magmas and ancient cratonic lithospheric mantle with pre-existing Ni- and PGE-rich sulfide phases may have contributed significantly to the PGE and Ni budget of the fertile flood basalts and eventually to the mineralisation. This observation is consistent with the location of fertile LIPs adjacent to deep old lithospheric roots (as inferred from tectonic environment and also seen in global tomographic images) and has predictive implications for exploration models. Barren LIPs contain fewer high-MgO lavas. The barren LIP lavas in general have low Os contents (mostly ≤0.02 ppb) with high Re/Os (10–≥200). They show isotopic variations between plume and EM2 geochemical signatures and have high Rb/Ba ratios. These signatures may indicate involvement of deep recycled material in the mantle sources or crustal contamination for barren LIPs, but low degrees of interaction with old lithospheric-type roots. [Copyright &y& Elsevier]

Mineral exploration targeting is a highly complex decision-making task. Two key risk factors, the quality of exploration data and robustness of the underlying conceptual targeting model, have a strong impact on the effectiveness of this decision-making. Geographic information systems (GIS) can be used not only for compiling, integrating, interrogating and interpreting diverse exploration data, but also for targeting by employing powerful mathematical algorithms, an approach that is commonly referred to as mineral potential modelling or mineral prospectivity mapping (MPM). Here, we pose and examine key aspects around the question of " how can we get better at mineral exploration targeting using GIS? " We do this by (1) reviewing the fundamental aspects of MPM, (2) identifying significant deficiencies of MPM, and (3) discussing possible solutions to alleviating or eliminating these deficiencies. In particular, we discuss how these deficiencies can be overcome by adopting an intelligence amplification system , such as the recently proposed exploration information system (EIS) for translating critical ore-forming processes into spatially predictive criteria (i.e., predictor maps and spatial proxies) and improving decision-making in mineral exploration targeting. [Display omitted] • Geographic information systems (GIS) are related to exploration information system (EIS). • The current status of study in GIS-based mineral exploration targeting is reviewed. • Use and abuse of mineral deposit models in mineral exploration targeting are discussed. • Mineral system-based exploration targeting using EIS is discussed. • Future research directions are provided. [ABSTRACT FROM AUTHOR]

• A new "information system" is proposed for mineral exploration targeting. • The system is called "exploration information system" (EIS). • EIS uses "mineral system" concepts in conjunction with GIS. • Ore-forming processes are classified into pre-, syn-, and post-mineralization parts. • EIS aims to automated translation of ore-forming processes into spatial proxies. The advent of modern data collection and storage technologies has brought about a huge increase in data volumes with both traditional and machine learning tools struggling to effectively handle, manage and analyse the very large data quantities that are now available. The mineral exploration industry is by no means immune to this big data issue. Exploration decision-making has become much more complex in the wake of big data, in particular with respect to questions about how to best manage and use the data to obtain information , generate knowledge and gain insight. One of the ways in which the mineral exploration industry works with big data is by using a geographic information system (GIS). For example, GIS platforms are often used for integration, interrogation and interpretation of diverse geoscience and mineral exploration data with the goal of refining and prioritising known and identifying new targets. Here we (i) briefly discuss the importance of carefully translating conceptual ore deposit models into effective exploration targeting maps, (ii) propose and describe what we term exploration information systems (EIS): a new idea for an information system designed to better integrate the conceptual mineral deposit model (i.e., the critical and constituent processes of the targeted mineral system) with data available to support exploration targeting, and (iii) discuss how best to categorise mineral systems in an EIS as scale-dependent subsystems to form mineral deposits. Our vision for the future use of EIS in exploration targeting is one whereby the mappable ingredients of a targeted mineral system are translated and combined into a set of weighted evidence (or proxy) maps automatically, resulting in an auto-generated mineral prospectivity map and a series of ranked exploration targets. We do not envisage the EIS replacing human input and ingenuity; rather we envisage the EIS as an additional tool in the exploration toolbox and as an intelligence amplifying system in which humans are making use of machines to achieve the best possible results. [ABSTRACT FROM AUTHOR]