Applied Earth Science: Transactions of the Institutions of Mining and Metallurgy

Measure while drilling (MWD) data collected from production holes can provide information on the location of stratigraphic units in banded iron formation-hosted iron ore deposits. Stratigraphic modelling in these deposits is typically based on data from exploration holes, and adding more densely spaced production data can potentially increase model detail at the bench scale. Previous MWD classification methods struggle to differentiate between neighbouring ore units. In this paper, multivariate Gaussian Processes (GPs) were applied to locate the contact between two iron ore units in the Dales Gorge Member in the Brockman Iron Ore Formation. Production MWD points were then labelled based on the GP output. By altering parameters of the labelling process, 24.4–49.4% of the test data were labelled, with accuracies from 81.4 to 86.8%. Classifications from the same hole were compared to ensure MWD label consistency. The results demonstrate that the proposed method can improve geological unit classification from MWD data.

One of the first decisions to be made when building a mineral resource model is the definition of geological/geostatistical domains. Cluster analysis is a set of techniques in machine learning that can be especially suited for this matter. In order to compare different approaches, two clustering algorithms were investigated in this study: k-means and the dual-space clustering algorithm. Choosing the most appropriate method and the number of clusters can be challenging and some metrics are needed to support these decisions, including the validation of the spatial distribution of the clusters, which is not always appropriately discussed in the literature. We introduce the use of correlograms of the indicators for that matter. Although clustering techniques can be robust for an application in resource modelling, expert knowledge is still necessary when applying cluster analysis to resource modeling, since final decisions should not be based solely on statistical indexes, but also on experience. In this paper, the proposed methodology was tested in a three-dimensional dataset related to a phosphate/titanium deposit.

The Alemtena kaolin deposit is located within the main Ethiopian rift. New geological, mineralogical, geochemical and physical test data provide evidence of the genesis and potential use of the kaolin. These data indicate that the deposit formed as a result of the intensive weathering of felsic volcanic rocks including rhyolitic tuffs, pumice, and rhyolite. The deposit contains elevated concentrations of Cr + Nb and Ce + Y+La and low concentration of Ba + Sr suggesting the deposit has a supergene origin. The presence of only kaolinite and quartz, and absence of high temperature minerals like pyrophyllite, dickite and pyrite, low bulk density (<2 g/cm³) and high crystallinity (HI > 0.9) strengthen the supergene origin. The presence of comparable grain size distribution, mainly white colour, high Al₂O₃ and kaolinite, relatively low concentrations of Fe₂O₃, TiO₂ and alkali elements make the kaolin favourable for various industrial applications including paper, filler, ceramics, pharmaceuticals, and agricultural industries. Reserve estimation from section logging and pitting gave nearly 85 million tons of reserve.

Tantalite mineralization is located at Kenticha, southern Ethiopia and hosted by granitic pegmatite. The pegmatite has intruded the low-grade Neoproterozoic basement that forms part of the southern end of Arabian Nubian Shield. Ethiopian Mineral Development Share Company is conducting open pit mining and producing about 150 tons of tantalite concentrate annually. About 500 kg concentrate with ∼50% tantalite is produced a day from 1200 tons of feed using different mineral processing techniques. Impact of dilution and ore loss on the recovery of concentrate was studied by collecting five samples, 30 kg each from the mine site and tailings. The results suggest that the effect of dilution is about 5% and ore loss in tailings is 13%. Impact of ore loss is significant compared to dilution. Ore loss can be improved by (i) adjusting the shaking tables, (ii) adjusting ore-water ratio irrespective of grain size; and (iii) dry magnetic separation.

This study aims to investigate and compare the mineralogical characteristics of the western Crete iron ores in the Kakopetros and Arolithi areas. In addition, conventional beneficiation techniques, namely, magnetic and heavy liquid separation, were examined in order to potentially upgrade these ores. The ores were characterized through X-ray diffraction, X-ray fluorescence, Scanning electron microscopy and ore microscopy. Kakopetros iron ore consists mainly of compact goethite masses, while cryptomelane in the form of concentric shells was observed in several samples. Arolithi ore consists of several compact masses of goethite and fine-grained graphite and pyrite which are dispersed in the groundmass. Conventional beneficiation of specific fractions indicated that the heavy liquid treatment of the 0.063-0.250 mm size fraction of the Kakopetros ore resulting in a significant increase in upgrading. Overall, the results showed that fine-grained gangue minerals are locked in the iron-rich masses, making the separation techniques of ores ineffective.

Mineralogical and geochemical variations of elements from the Adi-Daero iron–duricrust were studied using petrographic, X–ray diffraction and geochemical analyses. Petrographic studies of the samples confirmed the presence of nodular and colloform textural features. The XRD analysis showed the presence of haematite, goethite, quartz, kaolinite and ilmenite are the mineral constituents. Major–element geochemistry was determined by ICP-AES, and trace and REEs were analysed using ICP-MS. Of the major oxides, Fe₂O₃ (6.8–72.93 wt-%) and SiO₂ (11.07–77.75 wt-%) showed significant variation with generally increasing and decreasing trends from the iron-rich duricrust to the bedrock, respectively. In the profile studied, the alkali and alkaline earth elements (Ca, Mg, Na and K) were highly depleted, suggesting that iron–duricrust near–complete leaching. Elevated values of Sr and Ba in the lower part of the profile are probably due to their abundance in the protolith material (sandstone). A considerable enrichment of V and Cr, and Zr and REEs in the iron-rich duricrust and clay-rich horizon compared to the bedrock confirms their substitution for the Feoxyhydroxides, occurring in heavy mineral phases and adsorbed onto clay minerals, respectively. The La/Y <1 indicates an acidic environment in the upper part of the profile (AD-1 to AD-6; 0.64–0.99) and La/Y >1 a basic environment in the basal part of the profile (AD-7 to AD-12; 1.13–1.58). Similarly, the (La/Yb)N ratio of samples AD-1 to AD-6 (6.81–8.05) is significantly lower than that of AD-7 to AD–12 (10.09–24.54), reflecting an acidic environment. Positive Ce anomalies in the samples of AD-1 to AD-2 (1.17–1.2) are linked to the existence of cerianite due to change in oxidation state of Ce while in AD-8 and AD-9 (0.92–0.93), it is related to adsorption of Ce ions onto clay particles protolith. Therefore, the absolute enrichment of iron in the Adi-Daero iron–duricrust deposit was most likely an in situ process that involved vertical transfer from the iron-poor sandstone source rock.