Deposits In Australia Research Articles

Recovery of Xenotime and Florencite from Silicate Minerals Using a Combined Technique of Magnetic Separation and Flotation

Xenotime (YPO4), a significant phosphatic minerl rich in heavy rare earth elements (HREEs), typically associates with granitic rocks, exemplified in the Wolverine rare earth deposit in Australia. A mineral composition analysis indicates that the primary valuable minerals in the deposit are principally xenotime and minor florencite, with quartz and illite as the main gangue minerals, showing a relatively simple mineral composition. The grade of rare earth concentrate was increased to 14.29% and the recovery reached 94.48% through the magnetic separation pre-enrichment test. However, a high-grade rare earth concentrate could not be achieved using magnetic separation alone. Further purification of the magnetic concentrate is conducted through flotation. The grade of rare earth concentrate reached 51.26%, and the recovery rate reached 90.47%. In summary, this process achieves the efficient recovery of xenotime and florencite, having substantial industrial potential.

Decarbonising mining of Australia's critical mineral deposits: Opportunities for sustainable mining through solar photovoltaics and wind energy integration

Critical minerals are essential in numerous industrial applications, particularly those related to green energy production. Nonetheless, the mining and processing of these minerals are severely energy-intensive, relying predominantly on diesel, coal, and gas as sources of power in Australia. Consequently, the use of diesel, coal, and gas as power sources results in a substantial carbon footprint. An important research gap that remains to be explored in the Australian mining sector is investigating the potential for decarbonising the mining of critical minerals through the implementation of renewable energy to attain sustainable mining. This study examines the potential of using solar photovoltaics (PV) and wind energy towards the decarbonisation of critical mineral deposits, taking into account both the intrinsic mineral characteristics such as ore grade, ore depth, and co-existing mineral clusters, as well as external factors such as the capacity factor (CF) and the periods of low energy generation (lull times) of solar PV and wind, which are crucial in assessing the availability of the renewable energy sources explored. The results from this study indicate that a considerable number of critical mineral deposits in Australia are remotely located from the existing national transmission line infrastructure. These deposits often form geographical clusters and typically have favourable conditions for solar PV and wind energy implementation, characterised by high capacity factors and minimal lull times in solar PV/wind. This clustering presents a promising opportunity for powering mining activities with solar PV and wind energy, thus facilitating the decarbonisation of mining operations in Australia through the utilisation of shared renewable energy infrastructures. Moreover, the study identifies specific mineral deposits that are most suitable for decarbonisation with solar PV and wind energy integration. The research method used in this study proposes an evaluative framework that correlates the capacity factor of solar PV and wind with lull times from these sources, as well as with mineral intrinsic characteristics within deposits. This framework enables a comparative analysis of different deposits, assessing their relative suitability for the integration of solar PV and wind energy technologies. This framework is versatile and can be employed to assess different renewable energy sources, making it applicable to various global contexts. The findings from this study underscore the transformative potential of renewable energy sources, indicating that solar PV and wind energy offer new opportunities for attaining decarbonised and sustainable mining in Australia.

The role of zircon in hydrothermal heavy REE mineralisation: The case for unconformity-related ore deposits of north-west Australia

Zircon is hailed for its chemical and physical durability, but can undergo extensive chemical and structural modification due to radiation damage via the emission of alpha (α) particles, and subsequent low-temperature hydrothermal alteration. Here, we investigate Archean zircons from arkosic metasediments of the Browns Range Metamorphics (BRM) to evaluate their role in the formation of local unconformity-related heavy rare earth element (REE) ore deposits, within the Browns Range Dome, Western Australia. We determine that the heavy REE inventory of the BRM are primarily hosted in zircon, and that these zircons have a wide range of major element totals (77 to ~100 wt%, including low SiO2 and ZrO2 contents), and high and variable ‘non-formula’ components (U, Th, Y, REE, Nb, P, Al, Ca, Fe, Ti, F and OH− or H2O). Concentrations of Y + REE in some cases exceed 8 wt%. Extensive radiation damage (metamictisation) is confirmed by structural features including porous and amorphous domains, cavities, and voids. The lack of regional thermal events over an extended period likely prevented thermal annealing of these radiation-damaged zircons. Uptake of non-formula elements in metamict zircon, most likely during sedimentation in the late Archean, promoted further radiation damage, such that these grains remained highly susceptible to alteration by subsequent hydrothermal fluid circulation. We propose that the unconformity-related REE mineralisation was formed by saline fluids leaching Y + REE (and possibly P) from metamict zircon in the BRM, followed by ore mineral precipitation in fault zones near, and along the regional unconformity. More broadly, this model of ore formation may be relevant to other basin-hosted mineral systems, and could be used to guide exploration for unconformity-related REE deposits in Australia, and globally.

Geometallurgical Detailing of Plant Operation within Open-Pit Strategic Mine Planning

Mineral and metallurgical processing are crucial within the mineral value chain. These processes involve several stages wherein comminution is arguably the most important due to its high energy consumption, and its impact on subsequent extractive processes. Several geological properties of the orebody impact the efficiency of mineral processing and extractive metallurgy; scholars have therefore proposed to deal with the uncertain ore feed in terms of grades and rock types, incorporating operational modes that represent different plant configurations that provide coordinated system-wide responses. Even though these studies offer insights into how mine planning impacts the ore fed into the plant, the simultaneous optimization of mine plan and metallurgical plant design has been limited by the existing stochastic mine planning algorithms, which have only limited support for detailing operational modes. The present work offers to fill this gap for open-pit mines through a computationally efficient adaptation of a strategic mine planning algorithm. The adaptation incorporates a linear programming representation of the operational modes which forms a Dantzig-Wolfe decomposition, nested within a high-performing stochastic mine planning algorithm based on a variable neighborhood descent metaheuristic. Sample calculations are presented, loosely based on the Mount Isa deposit in Australia, in which a metallurgical plant upgrade is evaluated, showing that the upgraded design significantly decreases the requirement on the mining equipment, without significantly affecting the NPV.

Concurrent 20. Presentation for: Suitability of depleted gas fields for underground hydrogen storage in Australia

Presented on Wednesday 18 May: Session 20 If there is a significant adoption of hydrogen in Australia as an energy carrier, it will be necessary to have storage options to buffer the fluctuations in supply and demand, both for domestic use and for export. For large-scale storage in a single location, underground hydrogen storage (UHS) is the preferred option for reasons of both cost and safety. The search for suitable sites for UHS will depend on the proximity to potential hydrogen generation, ports, and processing infrastructure, as well as CO2 storage options for blue hydrogen. Although UHS in salt caverns is an established technology, most of the suitable salt deposits in Australia (in the Canning Basin in WA, the Adavale Basin in Qld, and the Amadeus Basin in the NT) are not always well-located for production and transport. Depleted gas fields have been used previously for storage of hydrogen-rich gas mixtures as well as natural gas storage and appear to be the most promising and widely available UHS option in Australia. There appears to be sufficient storage capacity in depleted gas fields in most of the geographic areas with hydrogen production potential. However, there are still technical challenges to be addressed, such as the extent of possible contamination of the stored hydrogen with residual hydrocarbons, and the possible effects of geochemical reactions and microbial processes. To access the presentation click the link on the right. To read the full paper click here

Suitability of depleted gas fields for underground hydrogen storage in Australia

If there is a significant adoption of hydrogen in Australia as an energy carrier, it will be necessary to have storage options to buffer the fluctuations in supply and demand, both for domestic use and for export. For large-scale storage in a single location, underground hydrogen storage (UHS) is the preferred option for reasons of both cost and safety. The search for suitable sites for UHS will depend on the proximity to potential hydrogen generation, ports, and processing infrastructure, as well as CO2 storage options for blue hydrogen. Although UHS in salt caverns is an established technology, most of the suitable salt deposits in Australia (in the Canning Basin in WA, the Adavale Basin in Qld, and the Amadeus Basin in the NT) are not always well-located for production and transport. Depleted gas fields have been used previously for storage of hydrogen-rich gas mixtures as well as natural gas storage and appear to be the most promising and widely available UHS option in Australia. There appears to be sufficient storage capacity in depleted gas fields in most of the geographic areas with hydrogen production potential. However, there are still technical challenges to be addressed, such as the extent of possible contamination of the stored hydrogen with residual hydrocarbons, and the possible effects of geochemical reactions and microbial processes.

3D Inversion of Magnetic Gradient Tensor Data Based on Convolutional Neural Networks

High-precision vector magnetic field detection has been widely used in the fields of celestial magnetic field detection, aeromagnetic detection, marine magnetic field detection and geomagnetic navigation. Due to the large amount of data, the 3D inversion of high-precision magnetic gradient vector data often involves a large number of computational requirements and is very time-consuming. In this paper, a 3D magnetic gradient tensor (MGT) inversion method is developed, based on using a convolutional neural network (CNN) to automatically predict physical parameters from the 2D images of MGT. The information of geometry, depth and parameters such as magnetic inclination (I), magnetic declination (D) and magnetization susceptibility of magnetic anomalies is extracted, and a 3D model is obtained by comprehensive analysis. The method first obtains sufficient MGT data samples by forward modeling of different magnetic anomalies. Then, we use an improved CNN with shear layers to achieve the prediction of each magnetic parameter. The reliability of the algorithm is verified by numerical simulations of synthetic models of multiple magnetic anomalies. MGT data of the Tallawang magnetite diorite deposit in Australia are also predicted by using this method to obtain a slab model that matches the known geological information. The effects of sample size and noise level on the prediction accuracy are discussed. Compared with single-component prediction, the results of multi-component joint prediction are more reliable. From the numerical model study and the field data validation, we demonstrate the capability of using CNNs for inversing MGT data.

The development of specialised modular protective structure on continuous miners against coal burst hazards

As mining progresses into deep ore deposits in Australia, geo-hazards such as coal burst and outbursts are becoming a major concern for mine workers. The occurrence of geo-hazards involved the ejection of coal lumps and sometimes large volumes of hazardous gases such as methane and carbon dioxide. Whilst it is extremely important to de-stress and de-gas the seam and adjacent strata before roadway development and install competent support systems such as steel mesh and bolt, the last line of protection will be the installation of a protective canopy on the Continuous Miner (CM), which is typically used for roadway developments, to shield mine workers from these deadly dynamic impacts of coal and rock resulting from a burst or outburst. This paper aims to introduce the design, manufacture and testing of an innovative modular protective structure on the CM in underground coal mines. The developed protective system can be easily assembled in the underground mining environment and provide a high level of protection against flying debris hazards in the event of a coal burst. The extensive experimental program and numerical simulations have confirmed the high performance of the protective system against high-speed impact loading by single and multiple coal rocks and projectiles.

A fossil record of land plant origins from charophyte algae.

Molecular time trees indicating that embryophytes originated around 500 million years ago (Ma) during the Cambrian are at odds with the record of fossil plants, which first appear in the mid-Silurian almost 80 million years later. This time gap has been attributed to a missing fossil plant record, but that attribution belies the case for fossil spores. Here, we describe a Tremadocian (Early Ordovician, about 480 Ma) assemblage with elements of both Cambrian and younger embryophyte spores that provides a new level of evolutionary continuity between embryophytes and their algal ancestors. This finding suggests that the molecular phylogenetic signal retains a latent evolutionary history of the acquisition of the embryophytic developmental genome, a history that perhaps began during Ediacaran-Cambrian time but was not completed until the mid-Silurian (about 430 Ma).

The timing of land plant origins

Paleobotany Until now, the first fossil evidence of land plants was from the Devonian era 420 million years ago. However, molecular phylogenetic evidence has suggested an earlier origin in the Cambrian. Strother and Foster describe an assemblage of fossil spores from Ordivician deposits in Australia dating to approximately 480 million years ago (see the Perspective by Gensel). These spores are of intermediate morphology between confirmed land plant spores and earlier forms of uncertain relationship. This finding may help to resolve discrepancies between molecular and fossil data for the timing of land plant origins. Science , abj2927, this issue p. [792][1]; see also abl5297, p. [736][2] [1]: /lookup/doi/10.1126/science.abj2927 [2]: /lookup/doi/10.1126/science.abl5297

3D Inversion of Magnetic Amplitude Data with Sparseness Constraint

Inversion of magnetic data has been an important tool for the interpretation of the data. The conventional inversion approaches cannot recover geologically acceptable models in the presence of remanence. Hence, some techniques have been developed for the inversion of magnetic amplitude data which is independent of magnetization direction. The conventional methods in the inversion of magnetic amplitude data give rise to blurred models with long tails. In this study, a new algorithm has been developed in favor of sparse inversion of the data that generates more focused models using the Cauchy norm. The algorithm applies a regularized conjugate gradient (RCG) method to acquire the inverse model. The new algorithm has been employed for the inversion of two data sets from synthetic examples and magnetic data sets over the Allahabad iron deposit in Iran and the Osborne copper–gold deposit in Australia. All data sets exhibit remanent magnetization. The results showed that the new algorithm generates robust solutions that are geologically acceptable.

Trace Element Concentrations Associated with Mid-Paleozoic Microfossils as Biosignatures to Aid in the Search for Life.

Identifying microbial fossils in the rock record is a difficult task because they are often simple in morphology and can be mimicked by non-biological structures. Biosignatures are essential for identifying putative fossils as being definitively biological in origin, but are often lacking due to geologic effects which can obscure or erase such signs. As such, there is a need for robust biosignature identification techniques. Here we show new evidence for the application of trace elements as biosignatures in microfossils. We found elevated concentrations of magnesium, aluminum, manganese, iron, and strontium colocalized with carbon and sulfur in microfossils from Drummond Basin, a mid-Paleozoic hot spring deposit in Australia. Our results also suggest that trace element sequestrations from modern hot spring deposits persist through substantial host rock alteration. Because some of the oldest fossils on Earth are found in hot spring deposits and ancient hot spring deposits are also thought to occur on Mars, this biosignature technique may be utilized as a valuable tool to aid in the search for extraterrestrial life.

Gold nuggets: the inside story

Gold nuggets have long captured the imagination of geologists, prospectors and the public alike, but their origin remains disputed. Supporting a supergene origin, most gold nuggets in Australia have been found at or near the soil surface. Many are intimately associated with, and even appear to enclose, soil materials and weathered rock. Even large nuggets (e.g., >2 kg) have surface features and/or gross morphologies that suggest chemical reworking in the regolith. Conversely, other nuggets have been found at depths of ten metres or more in the regolith, and large masses of gold have been encountered at considerable depth, in completely unweathered, hypogene environments. Nuggets and particulate gold from many deposits in Australia, New Guinea, SE Asia and Brazil have been examined by optical and electron-optical techniques to determine characteristics that may indicate their genesis and stability in the regolith. The specimens have been collected at or close to the surface but all nuggets (mass range ~1 gm to >8 kg) and many smaller grains appear to be hypogene. They have nearly homogeneous Ag contents, mostly in the range 3 to 20 wt%, although some have no detectable Ag. One specimen also contains up to 3 wt% Hg, but no other alloyed metals > 0.1 wt% were detected. Enclosed minerals are rare – with only galena, Bi sulphide, galenobismutite and complex Ag-Hg tellurides in a few samples. The internal structure of the nuggets comprises nearly equigranular, randomly-oriented crystal domains. Many crystals display coherent twins and/or short incoherent twins that terminate within the crystal, all typical of thermal annealing at temperatures >250°C. Some small nuggets from SE Asia, also with annealing fabrics are possibly the product of hydrothermal remobilization and re-precipitation. In comparisons, some specimens from New Guinea contain 10->30 wt% Ag and have internal structures such as zoning and ‘fern-like’ crystal habits. These are derived from epithermal deposits and have not been deformed or recrystallized since initial deposition. Even the largest nuggets have internal evidence of weathering. Many have secondary minerals such as Fe oxides, clays and calcite within them, but none of these is fully enclosed. Rather, they are all open to the outer margin of the nuggets, situated in interconnecting voids along crystal boundaries. These boundaries also exhibit Ag depletion, similar to the depletion rims on the external surface. EBSD analysis shows there is no variation in crystallographic orientation across, or into, the depletion zones. These characteristics show that nuggets are dissolving in the surface environment, not forming, with weathering reactions initiated on the external surface and, internally, along crystal boundaries.

Building NED: Open Access to Australia’s Digital Documentary Heritage

This article charts the development of Australia’s national edeposit service (NED), from concept to reality. A world-first collaboration between the national, state and territory libraries of Australia, NED was launched in 2019 and transformed our approach to legal deposits in Australia. NED is more than a repository, operating as a national online service for depositing, preserving and accessing Australian electronic publications, with benefits to publishers, libraries and the public alike. This article explains what makes NED unique in the context of global research repository infrastructure, outlining the ways in which NED member libraries worked to balance user needs with technological capacity and the variations within nine sets of legal deposit legislation.

Assessing environmental contamination from metal emission and relevant regulations in major areas of coal mining and electricity generation in Australia

The Hunter and Latrobe Valleys have two of the richest coal deposits in Australia. They also host the largest coal-fired power stations in the country. We reconstructed metal deposition records in lake sediments in the Hunter and Latrobe Valleys to determine if metal deposition in freshwater lakes have increased in the region. The current regulatory arrangement applied to metal emissions from coal-fired power stations in Australia are presented, discussing their capacity to address future increases in metal deposition from these sources. Sediment records of spheroidal carbonaceous particles (SCPs), a component of fly-ash, were also used as an additional line of evidence to identify the contribution of industrial activities related to electricity generation to metal deposition in regions surrounding open-cut coal mines and coal-fired power stations. Sediment metal concentrations and SCP counts in the sedimentary records, from the Hunter and Latrobe Valleys, both indicated that open-cut coal mining and the subsequent combustion of coal in power stations has most likely resulted in an increase in atmospheric deposition of metals in the local region. In particular, the metalloids As and Se showed the greatest enrichment compared to before coal mining commenced. Although the introduction of bag filters at Liddell Power Station and the decommissioning of Hazelwood Power Station appear to have resulted in a decrease of metal deposition in nearby lakes, overall metal deposition in the environment is still increasing. The challenge for the years to come will be to develop better regulation policies and tools that will contribute to reduce metal emissions in these major electricity production centres in Australia.

Overview of microbial technology in the utilization of rare earth resources

As an important resource for the development of modern industry, rare earth elements are widely used in nuclear technology, batteries, permanent magnet, electronic products, catalysis, and superconducting technology, and they have been mined at a considerable large scale. China’s rare earth resources are abundant, and their reserves account for approximately 36.7% of the world’s total reserves. Over the recent years, global rare earth resources are generally faced with over-exploitation, low utilization rates, and serious environmental pollution problems. Therefore, there is an urgent need for the development of recovery systems that are inexpensive and cause less pollution. Rare earth elements can be widely involved in the metabolism of compounds in various micro-organisms and may have mining capabilities. The use of microbial technology to mine and recover rare earth resources has provided a novel green and efficient method for the utilization of rare earth resources, and research in related fields has continued intensify. This paper primarily introduced the important role and utilization status of rare earth resources, summarized the distribution and characteristics of rare earth minerals in China, and identified the problems associated with rare earth mining and the advantages of microbial mining. Furthermore, it reviewed the development process of rare earth mining using micro-organisms, summarized its research progress, and introduced the research mechanism of microbial mining, primarily including related research on the mechanism of microbial leaching, adsorption and accumulation of rare earth elements, separation methods, species distribution, and mechanism action of rare earth ore mining microorganisms. Considering minerals of the Bayan Obo deposit in China and the Mount Weld deposit in Australia as examples, the extraction of rare earth elements from ore by microbes selected from the surrounding environment has been explained. Moreover, the recovery of rare earth elements in low-grade ore and waste by micro-organisms has been briefly described. Based on the current status of microbial mining of rare earth ore, future challenges and prospects of microbial utilization of rare earth elements have been proposed.

Constraining the Economic Potential of By-Product Recovery by Using a Geometallurgical Approach: The Example of Rare Earth Element Recovery at Catalão I, Brazil

Abstract Geometallurgy aims to develop and deploy predictive spatial models based on tangible and quantitative resource characteristics that are used to optimize the efficiency of minerals beneficiation and extractive metallurgy operations. While most current applications of geometallurgy are focused on the major commodity to be recovered from a mineral deposit, this contribution delineates the opportunity to use a geometallurgical approach to provide an early assessment of the economic potential of by-product recovery from an ongoing mining operation. As a case study for this methodology, possible rare earth element (REE) recovery as a by-product of Nb production at the Chapadão mine in the Catalão I carbonatite complex is used. Catalão I is part of the Alto Paranaíba igneous province in the Goias Province of Brazil. Currently, niobium is produced in the complex as a by-product of the Chapadão phosphates mine. This production is performed in the Tailings plant, the focus of this study. REEs, albeit present in significant concentrations, are currently not recovered as by-products. Nine samples from different stages of the Nb beneficiation process in the Tailings plant were taken and characterized by mineral liberation analyzer, X-ray powder diffraction, and bulk-rock chemistry. The recovery of REEs in each of the tailing streams was quantified by mass balance. The quantitative mineralogical and microstructural data are used to identify the most suitable approach to recover REEs as a by-product—without placing limitations on niobium production. Monazite, the most common rare earth mineral identified in the feed, occurs as Ce-rich and La-rich varieties that can be easily distinguished by scanning electron microscopy (SEM)-based image analysis. Quartz, Fe-Ti oxides, and several phosphate minerals are the main gangue minerals. The highest rare earth oxide content concentrations (1.75 wt % total rare earth oxides) and the greatest potential for REE processing are reported for the final flotation tailings stream. To place tentative economic constraints on REE recovery from the tailings material, an analogy to the Browns Range deposit in Australia is drawn. Its technical flow sheet was used to estimate the cost for a hypothetical REE production at Chapadão. Parameters derived from SEM-based image analysis were used to model possible monazite recovery and concentrate grades. This exercise illustrates that a marketable REE concentrate could be obtained at Chapadão if the process recovers at least 53% of the particles with no less than 60% of monazite on their surface. Applying capital expenditure and operational expenditure values similar to those of Browns Range suggests that such an operation would be profitable at current REE prices.

Characterization and Hydrogen Storage Performance of Halloysite Nanotubes.

Here we report on the structural characterization and the hydrogen storage performance of naturally derived halloysite nanotubes (HNTs). HNTs were mined from different deposits in Australia and purified with different processes including crushing, blunging, reblunging, sedimentation and filtration. The clay materials were characterized by different techniques such as powder XRD, TGA, XPS, FTIR spectroscopy, SEM, TEM, and N₂ sorption. Characterization results revealed that they are highly porous in nature with tubular morphology and exhibited excellent thermal stability. Among the halloysite materials studied, HNT1 which is having higher halloysite content and less kaolinite exhibited hydrogen uptake of 0.5 wt.% at 1 bar and -196 °C, which is increased to 1.33 wt.% when the pressure raised to 48 bar. High hydrogen uptake was linked with the high surface area, hollow tubular aluminosilicate structure and the large interlayer spacing of the HNTs as they favour physisorption of hydrogen. It was also demonstrated that HNT1 is considered to be better material than some of the materials reported so far in terms of their cost-effectiveness and environmental safety for the hydrogen storage.

Mapping iron oxide Cu-Au (IOCG) mineral potential in Australia using a knowledge-driven mineral systems-based approach

Iron oxide copper-gold (IOCG) deposits are consequences of lithospheric- to deposit-scale earth processes, and form where there was a coincidence of ore-forming processes in space and time. Building on previous conceptualisations we view a ‘mineral system’ as an ore-forming geological system in which four components are required to have operated efficiently and coincidentally, namely: (1) available sources of ore metals (i.e., copper, gold, uranium, rare-earth elements) and hydrothermal fluids; (2) energy sources to drive fluids in the ore-forming system; (3) active crustal and mantle lithospheric architecture, representing hydrothermal fluid and/or magma flow pathways; and (4) physico-chemical gradients along which ore metals were deposited to form ore bodies.This holistic multi-scale mineral systems framework has been used to develop a practical, knowledge-based yet data-rich, prospectivity mapping method applicable at regional to continental scales for hydrothermal and orthomagmatic ore-forming systems. We demonstrate how the mineral system components can be translated into mappable criteria and show how maps of mineral potential are generated by integrating diverse and rich input data sets. The method enables prediction of mineral potential not only in brownfields areas but also in greenfields and covered terranes with no previously known mineralisation. Here we report the application of this methodology in regional-scale mapping of the potential for IOCG deposits in Australia, using examples from five studies over the last decade in northern Queensland, eastern South Australia, and southern and central-eastern Northern Territory. Uncertainties in the results arising from assignment of weightings to input data layers were investigated by the application of Monte Carlo-type probabilistic simulations. The results of 500 iterations using randomly assigned weightings overall support the deterministic results but also show that modelled prospectivity is controlled mainly by variations in intrinsic values of the input geoscientific data sets (e.g. highs and lows of gravity values) rather than by the weightings.The results of the knowledge-driven data-rich analyses of IOCG potential have been validated against known IOCG deposits (not used directly in the analysis). We find in all five studies (Queensland, South Australia and Northern Territory) a good spatial correspondence, with few exceptions. Statistical analysis of prospectivity mapping results from the Tennant Creek – Mt Isa study area demonstrate that 15 of 16 IOCG deposits occur in the highest modelled prospectivity areas within 4.2% of the study area, representing an area reduction of 95.8%. Moreover, several new discoveries of Cu-Au mineralisation have been made within areas previously highlighted as highly prospective. This success and validation support the utility of Geoscience Australia’s approach as a decision-support tool to assist exploration companies and governments in craton- to regional-scale area selection for discovery of IOCG and other mineral systems.

The sulfuric acid bake and leach route for processing of rare earth ores and concentrates: A review

Rare earths are critical to numerous materials and applications underpinning modern civilisation. The majority of the world's rare earth reserves are hosted in the three minerals bastnasite, monazite and xenotime. A key step in the processing of rare earth mineral concentrates is the chemical decomposition of the mineral structure to release the constituent elements. The sulfuric acid bake has historically been, and is also currently, one of the major processes used for this step. Current sulfuric acid bake processes for the Bayan Obo deposit in China and the Mt. Weld deposit in Australia together account for more than half of the world's rare earth production. In the sulfuric acid bake, the rare earth elements are converted to rare earth sulfates which are dissolved in a subsequent water leach. The conditions required to achieve mineral decomposition vary widely for different rare earth minerals. Adjustment of process conditions may often be used to achieve some degree of impurity rejection which is beneficial to downstream processing. This paper reviews the application of the sulfuric acid bake process to ores/concentrates containing mainly monazite, xenotime and bastnasite, and other less common rare earth minerals including euxenite, samarskite, fergusonite, loparite, allanite, eudialyte and pyrochlore. The reported effects of feed mineralogy and process variables such as reaction temperature, bake duration, acid to concentrate ratio and particle size are presented along with a brief review of current understanding of the bake chemistry and water leach results.