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Energy Metals : BJV Vanadium Model Mineralisation Model and Extraction Update
Energy Metals : BJV Vanadium Model Mineralisation Model and Extraction
About this update from Energy Metals Ltd
Energy Metals Limited (ASX: EME) is pleased to update the market following completion of three-dimensional vanadium mineralisation modelling studies of the Bigrlyi uranium-vanadium deposit and the estimation of a new Exploration Target for vanadium. The models include construction of vanadium wireframe volumes for a 100 ppm V2O5 cut-off grade and implicit modelling of vanadium, uranium and calcium mineralisation shells using Leapfrog software. Further details of recent metallurgical test-work, aimed at optimising the co- extraction of vanadium and uranium, are also provided. A program to improve the economics of Energy Metals' flagship Bigrlyi project was initiated this year with a particular focus on studies to enhance the value of vanadium as a by-product commodity in a future Bigrlyi mining operation. Bigrlyi sandstone-hosted uranium-vanadium ores contain vanadium in various mineral forms that can be extracted by conventional acid leaching processes without the need for the extreme conditions required in the processing of more widely known magnetite-hosted vanadium. Bigrlyi uranium-vanadium ores are mineralogically identical to those of the Colorado Plateau district of the USA , which has a decades-long history of co-mining and co-recovery of uranium and vanadium; the extraction and recovery processes of uranium and vanadium from sandstone-hosted deposits are therefore well understood. The predominant industrial use of vanadium, at present, is as a steel strengthening agent; however, the metal has growing future uses in energy storage technologies, particularly redox flow batteries, which is the technology of choice in medium-scale storage of photovoltaically-generated energy. Although the significant price rise in vanadium seen in the latter part of 2018 has not been sustained this year, demand is expected to grow in future years. The current vanadium price is approximately $US 6 /lb V2O5, which is close to the long-term average vanadium price and compares with the current uranium spot price of $US26 /lb U3O8. Vanadium Mineralisation Modelling. The Bigrlyi deposit is hosted in the Mt Eclipse Sandstone of the Ngalia Basin (central Northern Territory ) and various sub-deposits from Anomaly-2 to Anomaly- 15 are recognised over a strike length of 10 km. In the past, modelling of uranium- vanadium mineralisation at Bigrlyi has been constrained by the uranium distribution resulting in previous vanadium resource estimates being reported on the basis of uranium cut-off grades. In the 2011 Mineral Resource Estimate (MRE), contained vanadium was estimated at 8.9 kilotonnes (kt) V2O5 at 1,197 ppm (500 ppm U3O8 cut-off grade) or 14.0 kt V2O5 at 935 ppm (250 ppm U3O8 cut-off grade); refer to ASX announcement of 28 June 2011 . However, it has been recognised since 1989 that a larger halo of vanadium mineralisation surrounds uranium mineralisation and that parts of the deposit are significantly vanadium-rich, yet uranium-poor; these parts of the deposit have not been adequately modelled previously and have potential to contribute significant additional vanadium resources. A program to improve the Bigrlyi deposit mineralisation model was initiated using data from Energy Metals' recently updated and re-verified exploration database. The program involved two phases of work: (1) construction of a vanadium mineralisation wireframe model at the 100 ppm V2O5 cut-off level followed by estimation of a new Exploration Target for vanadium and (2) development of geologically-constrained vanadium, uranium and calcium mineralisation shell models for the entire Bigrlyi deposit using Leapfrog implicit modelling software to interpolate between known mineralised zones, and to extrapolate along trend lines and to depth. Calcium was included in the modelling as a proxy for calcium carbonate (calcite), to better understand the distribution of acid- consuming gangue. As a first step, drill-hole assay data for V, U and Ca was compiled from Energy Metals' database and composited to 1 metre intervals producing some 25,300 records. A plot of U3O8 versus V2O5 assay results on this basis shows that the Bigrlyi deposit is dominated by vanadium-rich, but uranium-poor intervals - in fact 90% of the assayed metre intervals are of this type. Visualisation of this data in 3-dimensions shows that a large halo of vanadium mineralisation surrounds uranium- rich intervals. The halo is characterised by V2O5 values in the hundreds of ppm range (median 200 ppm V2O5) but with low uranium contents. At the 250ppm U3O8 cut-off level the vanadium halo would not be discernible, and it has not generally been considered in previous uranium-focused studies. The assay compilation allows calculation of the median V2O5:U3O8 ratio for Bigrlyi mineralisation, which is 23 for all data and 3.8 for uranium mineralised intervals above the 100 ppm U3O8 cut-off level. The dataset contains a significant number of metre intervals of elevated vanadium content, with over 5% of the dataset falling in the range 0.2% V2O5 to 10% V2O5 The modelling results permit the estimation of a new Exploration Target for vanadium in compliance with the JORC 2012 code. The results confirm the significantly expanded scale of vanadium mineralisation at Bigrlyi, compared to previous uranium-focussed results, and the potential to add resources in the future. A particular highlight is the Anomaly 7-to-9 corridor of sub-deposits, in which a vanadium-mineralised volume of more than 8 times the size of the uranium-mineralised volume has been estimated. The Anomaly 7-to-9 corridor is host to a vanadium Exploration Target (ET) of approximately 14 kilotonnes contained V2O5, which represents over 30% of the entire vanadium ET tonnage estimate for the Bigrlyi deposit. Leapfrog Modelling. In the second phase of the work program a 3-dimensional Leapfrog mineralisation model was constructed using a spheroidal interpolant method; the model was constrained by structural trends and internal fault planes. Vanadium, as well as uranium and calcium mineralisation shells were modelled for the entire deposit. Once again, the vanadium-rich but relatively uranium-poor zone along the Anomaly-7 to Anomaly-9 corridor was highlighted. Spatial variation in calcium, vanadium and uranium was explored in relation to internal stratigraphic units within the Mt Eclipse Sandstone. Most uranium mineralisation at Bigrlyi is associated with the contact zones between oxidised and reduced sandstone units, in particular between the oxidised Unit B and reduced Unit C higher in the stratigraphy (B-C contact), and between reduced Unit C and oxidised Unit D lower in the stratigraphy (C-D contact). Of particular note is the large calcium halo that extends stratigraphically above and below the unit contacts, and the occurrence of significant vanadium mineralisation within Unit C away from the B-C and C-D contacts. Leapfrog vanadium mineralisation shells compare favourably and are consistent with the wireframe model. In conclusion, the development of vanadium mineralisation models unconstrained by uranium cut- off grades has highlighted the potential of the Bigrlyi deposit, and in particular the Anomaly-7 to Anomaly-9 corridor, to host vanadium mineral resources additional to those previously estimated. An Exploration Target estimate suggests the Anomaly-7 to Anomaly-9 corridor may contain up to a third of total Bigrlyi vanadium resources. These models will form key input parameters for a review and potential update of the Bigrlyi mineral resource estimate and economic model in the coming 12 months, as well as providing a firm basis for further exploration work. Vanadium Optimisation Metallurgical Test-work. This year Energy Metals commenced a study to consider the range of metallurgical processing options available for co-recovery of uranium and vanadium from Bigrlyi uranium-vanadium ores. Following discussions with metallurgists at the Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights , Sydney , the parameters were established for a laboratory-based metallurgical test-work program. The main objective of the program was to optimise, with respect to acid concentration (pH) and other parameters such as redox potential (ORP) and temperature, the extraction of vanadium from a representative Bigrlyi uranium-vanadium ore. A new composite ore material was prepared using a 50:50 blend of Anomaly-4 and Anomaly-15 Unit C-D ores containing 2,007 ppm U3O8, 0.27% V (0.48% V2O5) and 3.1% Ca (4.3% CaO, equivalent to a maximum of 7.7% calcium carbonate). The results of an initial series of dilute (i.e. low slurry density) leach diagnostic tests were used to establish the base parameters for further conventional acid leach tests. The diagnostic test results showed that under all conditions uranium is 99% extractable and that a maximum of 80% of vanadium is extractable under conditions of pH 1.2, temperature 60-degreeC, and oxidation-reduction potential of 600 mV. The extractability was found to be most sensitive to pH. The results of a series of conventional leach tests were received in September 2019 . Three m) under varying conditions. As expected, uranium extraction was conventional acid leach tests at 50 wt% slurry density were conducted on a 1 kg of composite (P80 - 150 >98% under all conditions, whereas the extraction of vanadium varied with the different pH and temperature targets. C, the vanadium extraction from the Under the preferred leach conditions of pH 1.2 and 60 conventional test was 72.7%; this was lower than the diagnostic test probably due to particle size and to solution effects at the higher slurry density. However, this result is a substantial improvement on previous conventional leach test-work, which showed typical vanadium extractions around 40%. The sulphuric acid consumption of 123 kg/t represents a modest (approximately 20%) increase compared to acid consumption determined in previous base-case, uranium-only extraction tests. The economics of vanadium recovery is sensitive to reagent costs, and to acid consumption in particular; clearly such costs would be a key factor in development of a revised economic model for a Bigrlyi mining operation, and this factor would be important in determining whether vanadium recovery is economically viable within the current vanadium price framework. Uranium and vanadium extraction were also investigated as a function of leach time. Uranium extraction was found to be complete in all cases within 12 hours, but the vanadium extraction continued beyond 24 hours, although at a considerably slower rate. The final leach liquor compositions for the three conventional leaches show that along with uranium and vanadium, significant aluminium, iron and magnesium impurities were also leached. Plots of acid consumption versus uranium and vanadium extraction confirm the correlation between acid consumption and degree of extraction. It is important to note that the majority of the acid consumption occurs on acid addition to the ore due to its immediate reaction with calcium carbonate (calcite). The amount of calcite gangue in the ore feed is the most significant factor in determining overall acid consumption; for the ore material used in this test- work, the acid consumption due solely to reaction with carbonate gangue is estimated at 70 kg/t or just under 60% of the overall acid consumption. The uranium and vanadium extractions were also calculated for each size fraction. Uranium recovery was high in all fractions whereas the vanadium extraction was less in the fine clay fraction ( (C) 2019 Electronic News Publishing, source ENP Newswire