Potential Ore Deposits Research Articles

Structural Characterization of the Taltal Segment in Northern Chile Between 22°S and 26°S Using Local Earthquake Tomography

AbstractRecordings of earthquakes by a temporary deployment of 84 short period seismometers in northern Chile were used to derive regional 3D seismic velocity models for the Taltal segment. We used the Regressive ESTimator (REST) package for event detection and automatic onset estimation of P‐ and S‐wave arrival times to create an earthquake catalog with 23,985 hypocenters. We followed standard acceptability criteria (i.e., azimuthal gap and residual cutoff) to create a high‐quality data set and inverted for 3D Vp, Vs and Vp/Vs models using local earthquake tomography. Plots of hypocenters from the catalog, comprising 16,349 earthquakes, reveal active structures in the upper crust, dip changes along the slab and fracturing within the oceanic crust. Moreover, the wavespeed models illuminate anomalies in both the Nazca and South American plates that correlate with the observed seismicity distribution, including variations from low (1.75) to high (>1.80) Vp/Vs near the Atacama fault system on the coastline and the Domeyko Fault System in the forearc. The seismic velocity models also provide evidence for fluid circulation caused by the subducting Taltal ridge on the coast and partial melting feeding a volcanic complex close to the Andes. Finally, the observed low Vp/Vs ratios (∼1.75) are associated with copper mining operations in the area, suggesting that this kind of imaging can be used to characterize the distribution of potential ore deposits in the area.

Fractal analysis of structural characteristics and prospecting of the Luanchuan polymetallic mining district, China

Abstract The Luanchuan polymetallic mining district (LPMD) covers many major deposits of the East Qinling metallogenic belt in Henan Province, central China. It has attracted much attention because of its various types of minerals, abundant mineral reserves and huge metallogenic potential. Systematic research on the geology of LPMD has been carried out previously, and it is concluded that the formation of the ore deposits is dominantly controlled by fault structure. However, there are few reports on the quantitative characterization of fault structure and spatial distribution of deposits and the coupling relationship between them. This study applies fractal theory to the illustration of the characteristics of inter-relationship between fault structure and spatial distribution of the ore deposits in LPMD, which then may serve as a basis for further ore exploration. Our results indicate that the capacity dimension (CPDs) of integrated fault structure, NW-trend fault and NE-trend fault for the area investigated are 1.7206, 1.6539 and 1.2145, respectively; while the information dimension (IND) of which is 1.7143, 1.6559 and 1.2222, respectively. The studied area has superior geological environment for potential ore deposits, with major contribution from the NW-trend fault. Spatial distribution dimension value of metallic ore is 0.8873. Quantity fractal dimension and Density fractal dimension values of the metallic deposits are 1.1154 and 1.115, respectively. Quantitatively, the main ore deposits discovered in this area mainly fall on either CPD ≥ 1.49, IND ≥ 1.38 or 1.49 > CPD ≥ 1.00, 1.38 > IND ≥ 1.00. Qualitatively, conditions that facilitate ore deposits require higher fractal dimension values. Among the areas studied, we found that Rank I area is the most ideal region that fulfilled the quantitative and qualitative conditions, which is consistent with the actual location of the ore deposits discovered.

Application of Airborne Electromagnetics and Magnetics for Mineral Exploration in the Baishiquan–Hongliujing Area, Northwest China

Airborne electromagnetics is an effective and efficient exploration tool in shallow mineral exploration for its high efficiency and low cost. In 2016, airborne electromagnetic and airborne magnetic surveys have been carried out at the border of Xinjiang Uygur Autonomous Region and Gansu Province, the Northwest China. With an integrated system, the airborne electromagnetics and airborne magnetic data were collected simultaneously by AreoTEM-IV system from Aeroquest International Limited in Vancouver, BC, Canada, and the CS3 Cesium Vapor magnetometer from Scintrex in Concord, ON, Canada. About 3149 line-km of both data with 250 m line space were acquired. After data processing, the comprehensive analysis and interpretation of resistivity and magnetic anomalies has been carried out to infer lithological structure and outline the potential ore deposits. Verified by the ground surveys, seven outlined anomalies are consistent with the known ore sites, and one new gold deposit and several mineralization clues were found. The prospective reserves of gold are expected to exceed 10 tons. Besides, some prospecting target areas were outlined as the possible locations of copper–nickel deposits. The successful case shows the airborne magnetic data accords with geological structures, and the airborne electromagnetic method is effective in finding metal mineral resources, which can help to quickly identify potential ore targets with no surface outcrop.

Exploration of Potential Ore Deposits along the Cameroon Volcanic Line from Gravity and Magnetic Studies

A gravity and magnetic study has been carried out along the continental part of the Cameroon Volcanic Line (CVL), with the aim to explore the possibility of ore’s presence into the basement of this region. Different processing techniques have been applied, including the isostatic residual, the analytic signal and the Euler deconvolution to compute the Bouguer and magnetic anomalies. Following Euler solutions (result of Euler deconvolution) and the analytic signal results, four profiles crossing main structures on the isostatic residual have been used to enhance the structure of intrusions in the studied area. Despite the lack of constraints in the studied region, the results show that the basement is intruded by bodies of different density (2.57 g/cm3 to 2.87 g/cm3), different size and shape, with depths between 1 and 10 kilometers. These bodies have been interpreted as old rocks then as potential reservoirs of rare ores. In addition, volcanic rocks modeled have constituted potential reserves of other ores like graphite, sulfur, copper, iron.

A Special Issue Dedicated to Geometallurgy: Preface

AbstractGeometallurgy is an interdisciplinary field aimed at describing potential ore deposits in terms that mine planners and economists can use to design and run profitable mining operations. The major geologic contribution to the field is defining the spatial variability of potential and active mining resources so that planning and scheduling can accurately predict the economic performance and environmental impact of mining in time to respond efficiently to variations in ore type. This information is needed at the feasibility stage and throughout the mine life. We review the available literature on how geologists have contributed to these predictions in the past. There have been substantial advances in predicting comminution behavior. Prediction of recovery and environmental impacts are less advanced. This introductory paper provides a brief review of geometallurgy and a synopsis of the papers in the Special Issue, along with suggestions on future directions.

Joint Interpretation of Geological, Magnetic, AMT, and ERT Data for Mineral Exploration in the Northeast of Inner Mongolia, China

The integrated interpretation of data from various technologies has the potential to obtain a more accurate estimate of subterranean earth properties. In this paper, we implement the joint interpretation of geological and geophysical data for mineral exploration in the northeastern region of Inner Mongolia, China. The joint application of several methodologies reduces the exploration risk. We first determined an approximate and large potential area for mineral exploration with geological data and magnetic data interpretation in Gaoerqi. Results from the two types of data analysis show that the ore deposit strikes roughly east in the northern part of the Gaoerqi mining area. Next, we employed the audio-magnetotelluric (AMT) method to study the subterranean electrical resistivity distribution and divide the earth into four layers. Inverted resistivity sections from the AMT data illustrate that the ore deposits are likely developed in the low-resistivity zone of the survey area from the land surface to 300-m depth. Finally, the high-resolution borehole-to-surface electrical resistivity tomography (ERT) method was employed for further investigation of the location and attitude of the potential ore deposits. Inverted resistivity sections from the ERT data show that two prospective areas for mineral exploration were observed in the west of the survey area and that the eastern portion of the survey area warrants further investigation.

The Prospects for Expansion and Cost-Effective Development of Mineral Resources in the Mining and Industrial Areas of India

Exploitation of different kinds of mineral deposits is currently addressed to recover mostly the main product from an ore, with little effort either for its co-/by-products or for value-addition and creation of wealth from waste. Presently, mineral industry is facing many problems that make it less attractive for old and new entrepreneurs. To overcome them, there is a need for ‘Mega-, Micro- and Nano (10-9)-Scale’ (MMNS) investigations on both working and potential ore deposits. Salient aspects of these multi-disciplinary and multi-faceted, both field- and laboratory-based, investigations, together with their main objectives, during different stages of ‘Mineral Exploration and Exploitation’ (MEE) are presented. Brief description of some major explored and exploited ore deposits in India, along with their possible, high-value by-products, and waste from a few mining industries, both recommended for research, are listed. Nano-scale mineral technology, presently in its initial stage, may be effectively used to isolate valuable elements or molecules from ore and gangue minerals as well as has the potentiality for ‘Recycling and Reusing’ (R & R) of waste material, thereby serving the twin concept of value-addition and creation of wealth from waste. Some pertinent problems of mineral industry, which can be tackled by comprehensive MMNS studies, and some requiring future Research and Development (R & D), as well as expected results of such research are given. The objectives of these studies on ore deposits are (i) maximum recovery of both the main and valuable co-/by-products from ores for value-addition, (ii) utilization of their waste material for creation of wealth from waste and (iii) expansion and cost-effective development of mineral resources in mining and industrial areas of India.

Metasomatic Alteration Control of Petrophysical Properties in the Great Bear Magmatic Zone (Northwest Territories, Canada)

The Great Bear magmatic zone in the Northwest Territories of Canada contains large iron-oxide alkali alteration systems noted for having high potential for iron oxide-apatite, iron oxide-copper-gold, and affiliated ore deposits. Physical properties (density, magnetic, and electrical) were measured on 824 rocks samples selected to represent the range of metasomatic alteration types in the region. Mineralogical and geochemical classification of the prograde iron oxide and alkali alteration facies reveals large variations in physical properties through the evolution of the metasomatic systems. In particular, deep and early sodic alteration produced rocks having low densities and low magnetic susceptibilities. During calcium and iron precipitation, rocks gain extremely high density and susceptibility, due to crystallization of amphibole and especially magnetite. Subsequent hightemperature, potassic- and iron-altered rocks are marked by cocrystallization of magnetite with K-feldspar or biotite, and as the transition from magnetite to hematite takes place, K-feldspar crystallizes instead of iron oxides leading ultimately to potassic felsites having low densities and susceptibilities. Subsequent cooler, shallower, and more oxidized potassic-iron alteration produced high densities but moderate susceptibilities owing to crystallization of hematite. Understanding these major variations in physical properties of rocks enables detailed geophysical mapping of alteration zones, which builds and improves the regional context for integrated mineral exploration vectors to potential ore deposits.

Marine Phosphorites as Potential Resources for Heavy Rare Earth Elements and Yttrium

Marine phosphorites are known to concentrate rare earth elements and yttrium (REY) during early diagenetic formation. Much of the REY data available are decades old and incomplete, and there has not been a systematic study of REY distributions in marine phosphorite deposits that formed over a range of oceanic environments. Consequently, we initiated this study to determine if marine phosphorite deposits found in the global ocean host REY concentrations of high enough grade to be of economic interest. This paper addresses continental-margin (CM) and open-ocean seamount phosphorites. All 75 samples analyzed are composed predominantly of carbonate fluorapatite and minor detrital and authigenic minerals. CM phosphorites have low total REY contents (mean 161 ppm) and high heavy REY (HREY) complements (mean 49%), while seamount phosphorites have 4–6 times higher individual REY contents (except for Ce, which is subequal; mean ΣREY 727 ppm), and very high HREY complements (mean 60%). The predominant causes of higher concentrations and larger HREY complements in seamount phosphorites compared to CM phosphorites are age, changes in seawater REY concentrations over time, water depth of formation, changes in pH and complexing ligands, and differences in organic carbon content in the depositional environments. Potential ore deposits with high HREY complements, like the marine phosphorites analyzed here, could help supply the HREY needed for high-tech and green-tech applications without creating an oversupply of the LREY.

Identification of hydrothermal paleofluid pathways, the pathfinders in the exploration of mineral deposits: A case study from the Sukumaland Greenstone Belt, Lake Victoria Gold Field, Tanzania

Hydrothermal fluids play a key role in the process of metalliferous mineralization such as gold deposits. The modern exploration indicators for such deposits are tectonic structures and characteristic alteration minerals observed as detectable halos adjacent to mineral deposits. Tectonic fractures are the conduits to these hydrothermal fluids and thus control the spatial locations for the formation of mineral deposits. Along crustal structures, hydrothermal fluids commonly induce mineral alteration in the adjacent wall rocks depending on the physical–chemical conditions. These alteration patterns, which are the pathfinders for the proxies in the modern mineral exploration, can be detected by innovative application of combined remote sensing techniques. The study area has experienced intense tectonic deformations, which resulted to two major sets of structures, the NW–SE and NE–SW-trending structures. The knowledge-based analysis applied to SRTM data was useful in identifying crustal lineaments, which the above two set of structures, truncating lithological units of the Sukumaland Greenstone Belt were identified. The Feature Oriented Principal Component Selection (FPCS) together with the GIS functions applied to Landsat 7ETM+ data, were useful to enhance signals from hydrothermal alteration minerals. Results have revealed that the Sukumaland Greenstone Belt is intensively fractured, in a systematic pattern, and has apparently been “injected” with large volumes of hydrothermal fluids. Both processes together have resulted in the systematic and structurally controlled hydrothermal alteration patterns. In this study linear alteration patches are interpreted to represent the hydrothermal paleofluid pathways. Alteration patches coincide spatially with regional and local tectonic structures and are consistent with major gold occurrences and gold mines. This study indicate that careful analysis of SRTM and Landsat ETM+ data can identify crustal lineaments, the likely hydrothermal paleofluid conduits, which may lead to the discovery of potential ore deposits.

Data fusion and porphyry copper prospectivity models, southeastern Arizona

Mineral exploration programs commonly use a combination of geological, geophysical and remotely sensed data to detect sets of optimal conditions for potential ore deposits. Prospectivity mapping techniques can integrate and analyse these digital geological data sets to produce maps that identify where optimal conditions converge. Three prospectivity mapping techniques – weights of evidence, fuzzy logic and a combination of these two methods – were applied to a 32,000km2 study area within the southeastern Arizona porphyry Cu district and then assessed based on their ability to identify new and existing areas of high mineral prospectivity. Validity testing revealed that the fuzzy logic method using membership values based on an exploration model identified known Cu deposits considerably better than those that relied solely on weights of evidence, and slightly better than those that used a combination of weights of evidence and fuzzy logic. This led to the selection of the prospectivity map created using the fuzzy logic method with membership values based on an exploration model. Three case study areas were identified that comprise many critical geological and geophysical characteristics favourable to hosting porphyry Cu mineralisation, but not associated with known mining or exploration activity. Detailed analysis of each case study has been performed to promote these areas as potential targets and to demonstrate the ability of prospectivity modelling techniques as useful tools in mineral exploration programs.

Some Notes on the Lugiin Gol, Mushgai Khudag and Bayan Khoshuu Alkaline Complexes, Southern Mongolia

Volcanic-plutonic alkaline complexes from Lugiin Gol, Mushgai Khudag and Bayan Khoshuu, southern Mongolia (244, 139 and 131 Ma, respectively) occur within grabens in E-W lineaments. They are represented by syenitic rock-types (silica undersaturated to slightly silica oversaturated) potassic rocks and are associated to stockworks of carbonatitic veins, dykes and so on. Geochemical characteristics and isotope systematics point to a veined mantle source particularly enriched in LILE and LREE. The carbonatitic veins show high contents of Ba, Sr, Th and REE and are suitable as potential ore deposits.

Geophysical modelling of the central Skellefte district, Northern Sweden; an integrated model based on the electrical, potential field and petrophysical data

Abstract The central Skellefte district (CSD) is a part of a major ore-bearing district in northern Sweden. Studying the depth and patterns of the contact relationship between the two major stratigraphic units of the CSD, the Skellefte Group and the Vargfors Group, is a key issue to understand the geometry and structure of the area and to guide exploration of base metals. In this study, we interpret geoelectrical data collected along two profiles and magnetic and gravity data obtained from the database of the Swedish Geological Survey (SGU) and Boliden Mineral, to reveal contact relationship and depth extension of the major geological structures. Petrophysical analyses of the different lithologies were conducted on samples from the database of the SGU. Electric resistivity, induced polarisation (IP), magnetic susceptibility and density were determined on 154 core samples representing the different lithologies of the area. The resistivity/IP data were acquired to define structural relations down to a maximum depth of ~ 430 m. The major contact between sediments of the Vargfors basin and volcanic rocks of the Skellefte Group were outlined from the inversion of the resistivity/IP sections, suggesting a synform boundary between the Vargfors Group and Skellefte Group. The contact relationship between the felsic and mafic volcanic rocks of the Skellefte Group is also understood with the help of the resistivity/IP data. The resistivity models were tested using the magnetic data and magnetic susceptibility inferred on the resistivity bodies. The result suggests a good correlation between the initial resistivity model and the magnetic and gravity field calculated from that model. The integration and interpretation of geological and geophysical data improved the basic understanding of the geometry of CSD. Based on previous geological investigations, the potential ore deposits are believed to be found along the volcano-sedimentary contact. The result from this study can thus be used for the base metal exploration, finding the locations of potential sulphide deposits and give a better understanding about spatial relationship between different geology structures in the CSD.

Worldwide potential for ex-situ mineral carbonation

World data on (i) CO2-emission sites and (ii) ore deposits in mafic/ultramafic (M/UM) rock contexts have been crossed through a GIS (under ArcGIS) in order to identify sites of potential interest for implementing the ex-situ carbonation method. Applying relevant criteria, such as the nature and quantity of mining waste, volumes of CO2 e mission, distance between mine and emission sites, and adding mining data from the literature, has led to a selection of eight potential ore deposits in an ultramafic rock context. These are located in Botswana, South Africa, China, Russia and Kazakhstan, and all lie within a 300 km radius of coal-fired industrial plants emitting >1 Mt/year CO2. This approach is but a first level of reflective thinking that could be complemented by applying hydrographic, topographic, chemical and mineralogical, economic, and even political criteria.

Optimal Location of a Copper Smelter in Saudi Arabia for Polymetallic Deposits Using a Computerized Numerical Approach

The objective of this research work is to locate an optimal site for a copper smelter in Saudi Arabia to utilize the polymetallic ore deposits in the Arabian Shield. The research is concerned with investigating the potential ore deposits including their reserve sizes and ore grades. The study includes determining the deposits' locations with reference to industrial facilities, business centers, and shipping yards along with its location with reference to national highway network. The research includes a survey of seven applicable smelter sites that include two districts of the metalliferous ore deposits, four seaports, and the central region of the Kingdom. The survey includes determining the involved potential local ore deposits, possible imports of copper ore concentrates, and available industrial facilities. A computer program was constructed using Lotus spreadsheet to manipulate the relevant data to rank the candidate smelter sites. A macro function programming allows the reflection of any relevant information to update the ranking result. The analytical technique has ranked the candidate smelter sites. The seaport of Yanbu was ranked first to host the smelter plant. The district of Jabal Sayid in the Northern belt of mineral prospects ranked second amongst all candidate smelter sites.

The mineralogy and crystal chemistry of deep-sea manganese nodules, a polymetallic resource of the twenty-first century

The relatively high concentrations of cobalt, nickel, and copper in deep-sea manganese nodules, such as those occurring on the sea-bed beneath the north equatorial Pacific Ocean, indicate that these marine sediments are potential ore deposits. In order to explain the strong enrichments of Ni, Cu, and Co in the nodules, the crystal chemistries and structures of the host manganese oxide minerals must be understood. Over twenty manganese(IV) oxide minerals are known, but only three predominate in manganese nodules. They are todorokite, birnessite, and delta-MnO 2 . All Mn IV oxides contain edge-shared MnO 6 octahedra linked in diverse ways, leading to a hierarchy of structure-types somewhat resembling the classification of silicates. Todorokite is deduced to contain chains of edge-shared MnOe octahedra enclosing huge tunnels, thus resembling hollandite and psilomelane. Birnessite has a layered structure with essential vacancies in the sheets of edge-shared MnO 6 octahedra, while δ-MnO 2 is a disordered birnessite. The uptake of Co into manganese nodules involves replacement of low-spin Co 3+ for Mn 4+ ions in the structures, whereas Ni 2+ and Cu 2+ substitute for Mn 2+ ions in octahedra located in the chains or between layers of edge-shared MnO 6 octahedra.

Mechanism for nucleation and growth of manganese nodules

FERROMANGANESE oxide crusts and concretions cover vast areas of the sea floor1,2 and the relatively high concentrations of cobalt, nickel and copper in manganese nodules, together with the high population densities of polymetallic nodules on certain sea beds, such as the North Pacific Equatorial Belt3, mean that these marine sediments are potential ore deposits. A fact that is often overlooked, however, is that in many sedimentary environments most of the manganese and iron does not accumulate in the form of ferromanganese nodules, but instead is distributed throughout the sediment in the form of dispersed microscopic concretions4. A fundamental problem in accounting for the origin and distribution of polymetallic nodules is to explain the nucleation and growth of the host ferromanganese oxide phases. We demonstrate here that crystal-structure relationships between host manganese (IV) oxide and iron (III) oxide hydroxide phases control the authigenesis, mineralogy and metal enrichments of manganese nodules.

Lunar Features and Lunar Problems

The major features of the Moon (marcs, highlands, craters, fractures) are briefly reviewed to encourage geologists to participate in the solution of lunar problems—problems involving the interpretation of varied land forms, the rock types and their distribution, potential ore deposits, and lunar tectonics. Special attention is given the fracture systems, the origin of the lava filling many closed craters, and the origin of the central peak complexes.