What Happened to LWE? From a Tour Operator\u27s Point of View

The initial preparation for the exposition was good. The follow-up advertisement did not stimulate the interest from client\u27s perspective. The critical element which killed the fair was the press

Critical Metal Mineralogy: Preface to the special issue of Mineralogical Magazine

The phrase ‘critical metals’ has become widely used over the last decade. Critical metals are those for which demand is increasing, largely due to their use in new technologies, but for which there are restrictions to supply. These supply restrictions are normally not due to a natural shortage of these elements, but instead can be attributed principally to a concentration of production in a small number of countries. Markets for many of the critical metals are still small when compared with those for major industrial metals such as copper or lead, and at the time of writing prices for almost all metals are low; as a result it can be difficult to diversify production. A number of reports, books and special issues have been published on the subject (Graedel et al., 2012, EC, 2014, Gunn, 2014, Chakhmouradian et al., 2015, Lusty and Gunn, 2015, Graedel et al., 2015)

Tracing the fluid source of heavy REE mineralisation in carbonatites using a novel method of oxygen-isotope analysis in apatite: the example of Songwe Hill, Malawi

Stable (C and O) isotope data from carbonates are one of the most important methods used to infer genetic processes in carbonatites. However despite their ubiquitous use in geological studies, it is suspected that carbonates are susceptible to dissolution-reprecipitation and isotopic resetting, especially in shallow intrusions, and may not be the best records of either igneous or hydrothermal processes. Apatite, however, should be much less susceptible to these resetting problems but has not been used for O isotope analysis. In this contribution, a novel bulk-carbonatite method for the analysis of O isotopes in the apatite PO4 site demonstrates a more robust record of stable isotope values. Analyses of apatite from five carbonatites with magmatic textures establishes a preliminary Primary Igneous Apatite (PIA) field of δ18O = + 2.5 to + 6.0‰ (VSMOW), comparable to Primary Igneous Carbonatite (PIC) compositions from carbonates. Carbonate and apatite stable isotope data are compared in 10 carbonatite samples from Songwe Hill, Malawi. Apatite is heavy rare earth element (HREE) enriched at Songwe and, therefore, oxygen isotope analyses of this mineral are ideal for understanding HREE-related mineralisation in carbonatites. Carbonate C and O isotope ratios show a general trend, from early to late in the evolution, towards higher δ18O values (+ 7.8 to + 26.7‰, VSMOW), with a slight increase in δ13C (− 4.6 to − 0.1‰, VPDB). Oxygen isotope ratios from apatite show a contrary trend, decreasing from a PIA field towards more negative values (+ 2.5 to − 0.7‰, VSMOW). The contrasting results are interpreted as the product of the different minerals recording fluid interaction at different temperatures and compositions. Modelling indicates the possibility of both a CO2 rich fluid and mixing between meteoric and deuteric waters. A model is proposed where brecciation leads to depressurisation and rapid apatite precipitation. Subsequently, a convection cell develops from a carbonatite, interacting with surrounding meteoric water. REE are likely to be transported in this convection cell and precipitate owing to decreasing salinity and/or temperature

Rare earth elements in karst-bauxites: a novel untapped European resource?

Karst-bauxite deposits form as a result of the accumulation of residual clay minerals in depressions on a karst limestone surface, and their subsequent lateritic weathering. Rare earth elements (REE) become concentrated in the bauxite deposits due to crystallisation of authigenic REE-bearing minerals, accumulation of residual phases and the adsorption of ions on clays and other mineral surfaces. REE are concentrated in the red mud waste generated by alumina production from bauxite through the Bayer process. Red muds thus contain on average 900 ppm REE compared with typical values of <100 ppm to ~500 ppm REE in the bauxites. Extraction of REE from red mud has been shown to be feasible although it is challenging due to the heterogeneous spatial distribution of REE in the bauxites and the need for development of appropriate processing methods. With annual European extraction of bauxite estimated to be approximately 3.5 million tonnes per annum, resulting in approximately 1.4 million tonnes of red mud from the production of alumina, understanding the REE resource potential of bauxites is integral to the assessment of European REE resources

A review of the potential for rare earth element resources from European red muds: examples from Seydişehir, Turkey and Parnassus-Giona, Greece

Rare-earth elements (REE) are viewed as ‘critical metals’ due to a complex array of production and political issues, most notably a near monopoly in supply from China. Red mud, the waste product of the Bayer process that produces alumina from bauxite, represents a potential secondary resource of REE. Karst bauxite deposits represent the ideal source material for REE-enriched red mud as the conditions during formation of the bauxite allow for the retention of REE. The REE pass through the Bayer Process and are concentrated in the waste material. Millions of tonnes of red mud are currently stockpiled in onshore storage facilities across Europe, representing a potential REE resource. Red mud from two case study sites, one in Greece and the other in Turkey, has been found to contain an average of ∼1000 ppm total REE, with an enrichment of light over heavy REE. Although this is relatively low grade when compared with typical primary REE deposits (Mountain Pass and MountWeld up to 80,000 ppm), it is of interest because of the large volumes available, the cost benefits of reprocessing waste, and the low proportion of contained radioactive elements. This work shows that ∼12,000 tonnes of REE exist in red mud at the two case study areas alone, with much larger resources existing across Europe as a whole

REE minerals at the Songwe Hill carbonatite, Malawi: HREE-enrichment in late-stage apatite

Compared to all published data from carbonatites and granitoids, the fluorapatite compositions in the Songwe Hill carbonatite, determined by EPMA and LA ICP-MS, have the highest heavy (H)REE concentration of any carbonatite apatite described so far. A combination of this fluorapatite and the REE fluorocarbonates, synchysite-(Ce) and parisite-(Ce), which are the other principal REE bearing minerals at Songwe, gives a REE deposit with a high proportion of Nd and a higher proportion of HREE (Eu–Lu including Y) than most other carbonatites. Since Nd and HREE are currently the most sought REE for commercial applications, the conditions that give rise to this REE profile are particularly important to understand. Multiple apatite crystallisation stages have been differentiated texturally and geochemically at Songwe and fluorapatite is divided into five different types (Ap-0–4). While Ap-0 and Ap-1 are typical of apatite found in fenite and calcite-carbonatite, Ap-2, -3 and -4 are texturally atypical of apatite from carbonatite and are progressively HREE-enriched in later paragenetic stages. Ap-3 and Ap-4 exhibit anhedral, stringer-like textures and their REE distributions display an Y anomaly. These features attest to formation in a hydrothermal environment and fluid inclusion homogenisation temperatures indicate crystallisation occurred between 200–350 °C. Ap-3 crystallisation is succeeded by a light (L)REE mineral assemblage of synchysite-(Ce), strontianite and baryte. Finally, late-stage Ap-4 is associated with minor xenotime-(Y) mineralisation and HREE-enriched fluorite. Fluid inclusions in the fluorite constrain the minimum HREE mineralisation temperature to approximately 160 °C. A model is suggested where sub-solidus, carbonatite-derived, (carbo)-hydrothermal fluids remobilise and fractionate the REE. Chloride or fluoride complexes retain LREE in solution while rapid precipitation of apatite, owing to its low solubility, leads to destabilisation of HREE complexes and substitution into the apatite structure. The LREE are retained in solution, subsequently forming synchysite-(Ce). This model will be applicable to help guide exploration in other carbonatite complexes

The importance of tectonic setting in assessing European Rare Earth potential

Rare earth element (REE) resources are commonly found associated with alkaline igneous complexes or carbonatites, or as secondary deposits derived from igneous rocks. Globally, many REE deposits occur around the margins of Archaean cratons, most in continental rift zones. Europe contains many such rift zones, which are generally younger in the south. Many of these rifts are intracontinental, whereas others are associated with the opening of oceans such as the Atlantic. All these rift systems have the potential to host REE resources, but whereas the older provinces of northern Europe are deeply exposed, exposures in southern Europe are largely at the supracrustal level. This paper considers how an understanding of the tectonic setting of Europe’s REE resources is vital to guide future exploration

Alkaline magmatism and REE resources: a European overview, and links to Canada

In recent years, the European Union (EU) has prioritised the issue of critical raw materialsa – those materials which are important for the economy, but have risks to their supply. Of the materials identified as critical, the rare earth elements (REE) are considered to have the highest supply risks, since > 90% of global production comes from China. Several programmes are underway in Europe to investigate the supply chain for the REE and other critical materials. These include the EU-funded EURARE projectb, which aims to set the basis for the development of a European REE industry; and the Security of Supply of Mineral Resources (SoS Minerals) research programme in the UK

Responsible sourcing of critical metals

This is the author accepted manuscript. The final version is available from Mineralogical Society of America via the DOI in this recordMost critical raw materials, such as the rare earth elements (REE), are starting products in long manufacturing supply chains. It is difficult for consumers, buying cars or smartphones for example, to engage with the original mines and demand environmental and social best practice. Geoscientists can become involved in responsible sourcing because geology is related to environmental impact factors such as energy requirements, resource efficiency, radioactivity and the amount of rock mined. The energy and material inputs and emissions and waste from mining and processing can be quantified using life cycle assessment (LCA). Preliminary LCA studies for REE show little over all difference between ‘hard rocks’ such as carbonatites and easily leachable ion adsorption clays, mainly because of the embodied energy in chemicals used for leaching, dissolution and separation.This work is part funded by the NERC SoS RARE project, NE/M011429/1

Evidence for dissolution-reprecipitation of apatite and preferential LREE mobility in carbonatite-derived late-stage hydrothermal processes

The Tundulu and Kangankunde carbonatite complexes in the Chilwa Alkaline Province, Malawi, contain late-stage, apatite-rich lithologies termed quartz-apatite rocks. Apatite in these rocks can reach up to 90 modal% and displays a distinctive texture of turbid cores and euhedral rims. Previous studies of the paragenesis and rare earth element (REE) content of the apatite suggest that heavy REE (HREE)-enrichment occurred during the late-stages of crystallization. This is a highly unusual occurrence in intrusions that are otherwise light REE (LREE) enriched. In this contribution, the paragenesis and formation of the quartz-apatite rocks from each intrusion is investigated and re-evaluated, supported by new electron microprobe (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data to better understand the mechanism of HREE enrichment. In contrast to the previous work at Tundulu, we recognize three separate stages of apatite formation, comprising an “original” euhedral apatite, “turbid” apatite, and “overgrowths” of euhedral late apatite. The crystallization of synchysite-(Ce) is interpreted to have occurred subsequent to all phases of apatite crystallization. The REE concentrations and distributions in the different minerals vary, but generally higher REE contents are found in later-stage apatite generations. These generations are also more LREE-enriched, relative to apatite that formed earlier. A similar pattern of increasing LREE-enrichment and increased REE concentrations toward later stages of the paragenetic sequence is observed at Kangankunde, where two generations of apatite are observed, the second showing higher REE concentrations, and relatively higher LREE contents. The changing REE distribution in the apatite, from early to late in the paragenetic sequence, is interpreted to be caused by a combination of dissolution-reprecipitation of the original apatite and the preferential transport of the LREE complexes by F- and Cl-bearing hydrothermal fluids. Successive pulses of these fluids transport the LREE out of the original apatite, preferentially re-precipitating it on the rim. Some LREE remained in solution, precipitating later in the paragenetic sequence, as synchysite-(Ce). The presence of F is supported by the F content of the apatites, and presence of REE-fluorcarbonates. Cl is not detected in the apatite structure, but the role of Cl is suggested from comparison with apatite dissolution experiments, where CaCl2 or NaCl cause the reprecipitation of apatite without associated monazite. This study implies that, despite the typically LREE enriched nature of carbonatites, significant degrees of hydrothermal alteration can lead to certain phases becoming residually enriched in the HREE. Although at Tundulu the LREE-bearing products are re-precipitated relatively close to the REE source, it is possible that extensive hydrothermal activity in other carbonatite complexes could lead to significant, late-stage fractionation of the REE and the formation of HREE minerals. Keywords: Apatite, carbonatite, rare earth elements, Chilwa Alkaline Province, Tundulu, Kangankunde, REE mobility, dissolution-reprecipitatio