Sela Dingay kaolin deposit is a primary deposit formed mainly through the weathering of rhyolitic ignimbrite. Integrated analyses of geological, mineralogical, geochemical and physical properties were conducted to characterise the industrial applications of Sela Dingay kaolin. X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) were used to characterise the raw kaolin samples. The results show that Sela Dingay kaolin is mainly composed of kaolinite (66-93%) and quartz (9-34%). The higher chemical index of alteration (CIA = 94.2%) and chemical index of weathering (CIW = 96.8%) values suggest that Sela Dingay kaolin was formed by intense chemical weathering under oxidising conditions. Sela Dingay kaolinite deposit consists of high percentage of clay/silt-sized particles, a low shrinkage value (1.1-3.4%), medium-high plastic limit (25-35%), with specific gravity and pH values ranging between 2.47 and 2.56 g/cm3 and 6.3 and 7.2, respectively. The overall results show that Sela Dingay kaolin is medium to high grade and it can be used for various industrial applications with appropriate beneficiation processes to remove higher amounts of Fe2O3 and quartz. Therefore, the newly discovered kaolin deposit (estimated at 5,136,166 tonnes) in the Sela Dingay area is a potential target for future kaolin exploitation.
The development process of fractures in coal beds is influenced by many factors, and its development mechanism is complicated and difficult to be predicted accurately. The research addresses the problem of penetration enhancement technology in the process of coal bed methane mining, and designs a method that incorporates the theory of hydraulic fracturing fracture development. In the process, the coal seam structure was studied, the coal rock was cracked using water injection, the fracture development process during hydraulic fracturing was analysed, the numerical simulation model was constructed using the expanded finite element method, and the fluid flow process in the unit was designed. The experimental results show that when the research method is tested for the time-consuming generation of numerical simulation results, the maximum time-consuming generation of is only 92 ms when the fracture length is 10 m, which is shorter than that of other methods; when analysing the results of fracture initiation pressure calculations, the error between the calculation results generated by the research method and the actual measured results in a total of 14 sample points of the two mines is maintained at less than 0.5 MPa; in the analysis of the relationship between the fluid flow rate and the fluid flow rate, the error is kept at less than 0.5 MPa in the case of fluid flow rate exceeding 0.5 ms; the fracture length and the longest fracture radius decreased significantly with the increase of the injection flow rate after the injection flow rate exceeded 0.005 m3/s. It shows that the research method can effectively carry out coal seam penetration enhancement with good computational efficiency and higher accuracy.
Characterisation of six supergene ferromanganese ore samples revealed that P was hosted by several different Fe and Mn oxides. Goethite had the highest (up to >1% or higher) and highest mean (up to 0.32%) P contents, then cryptomelane-hollandite (mean up to 0.12% P) and nsutite-pyrolusite (mean up to 0.14% P). When present in the same sample, nsutite had a higher mean P content than pyrolusite. Phosphate minerals were not detected in the samples. P deportment was variable with deposit, deposit type and within individual mineral grains. EPMA showed that P content is elevated in cryptomelane with higher Mn/(Fe + Al + Si) ratios and in todorokite with lower Mn/(Fe + Al + Si) ratios. The results show that higher phosphorus supergene ferromanganese ores with considerable cryptomelane and nsutite contents are likely to have multi-phase Fe-P and Mn-P deportment. The propensity for very fine-scale intergrowths of goethite and Mn oxides +/- aluminosilicates in some ore types means that reliable characterisation of P deportment is critical in informing potential P-reduction pathways for ferroalloy feedstocks. P was most probably incorporated into Mn oxides via near-surface adsorption via complexation with cations such as Ca or Mg in todorokite, but the presence of structural P cannot be precluded in cryptomelane and nsutite.
This study provides an in-depth geophysical interpretation of the gold and base metal mineralisation of the Ibaga area related to hydrothermal alteration using high-resolution aero-geophysical and induced polarisation ground survey datasets. Despite its potential for gold and base metal and the available artisanal mines, the Ibaga area has remained poorly understood on geophysical signatures of ore deposits and other subsurface geological structures controlling the mineralisation. The magnetic results on the major structures show high magnetic signatures, supported by gravity, radiometric signatures and petrophysical analysis. The potential mineralised structures are interpreted as dyke for gold, and contacts for copper and the depth to the basement varies from 0.113 to 1.556 km. The gravity anomaly shows high values on the gold mineralisation similar to high-density values of dolerite dykes and gabbro and low to medium radiometric concentrations associated with mineralised zones. The magnetic signatures on the copper deposits coincide with the relative positive gravity anomaly of high-density intrusive bodies and relatively moderate conductive bodies with elevated potassium (K) alteration. The copper deposit also has intermediate K and low to intermediate K/Th and K/U ratios caused by K alteration within the geological structures. The good spatial correlation of the hydrothermally altered zones, igneous intrusions and geological structures implies that the geological features associated with gold and copper mineralisation lie within the regions of high-density intrusive bodies and geological structures (faults, fractures and dykes). These features are also associated with relatively moderate conductive bodies, low to intermediate radiometric concentrations and low to moderate magnetic signatures. Thus, the study reveals that the delineated geophysical signatures on gold and base metal mineralisation are associated with quartz-sericite-muscovite +/- chlorite hydrothermally altered areas, deformed structures, and intrusive bodies, which act as pathways for the migration and accumulation of hydrothermally altered fluids.
The majority of commercial kaolin deposits in Ethiopia originate from felsic igneous rock. On the other hand, the Adi-Hano kaolin deposit is a recently recognised kaolin deposit that was formed from sandstone. Nevertheless, this provides insight into potential deposit occurrences in the region's sedimentary sequence. This study aims to characterise the genesis, quality, quantity and potential industrial uses of Adi-Hano kaolin deposit. It was carried out by integrated field geological descriptions, thin-section interpretation, physical testing, mineralogical (X-ray diffraction, XRD) and geochemical investigations. An inductively coupled plasma mass spectrometer (ICP-MS) and an inductively coupled plasma atomic emission spectrometer (ICP-AES) were used to analyse the geochemistry. The main mineral phases in the deposit are quartz and kaolinite, while the minor mineral phases are rutile, cristobalite and tridymite. The elevated value of quartz, limits the quality of kaolin being as an impurity for its industrial use. The integrated result indicates that insitu weathering followed by leaching of the arkosic sandstone played a great role in kaolin deposit formation. The average chemical index of alteration (CIA; 94.18%) also shows that the source rock has experienced strong weathering and alteration. The deposit contains minor concentrations of Sr + Ba and Fe2O3 + TiO2, and high concentrations of Y + Ce + La and Nb + Cr values, which are indicative of a supergene type origin. Following treatment of the deposit, its similar grain size distribution, colour, relatively high Al2O3, relatively low TiO2, Fe2O3 and alkali components make it suitable for a variety of industrial uses, such as ceramics, refractory, paper coating and paint.
Sulphide minerals in the Palaeoproterozoic Loch Maree Group at Kerry Road, Gairloch, North-West Scotland, have a near-zero sulphur isotope composition of magmatic origin. New isotopic measurements in the region show a wider range of compositions. Other samples from the Gairloch region have compositions up to 15 parts per thousand heavier than the ore samples in the Kerry Road VMS deposit, indicating that there was a source of sulphur additional to magmatic sulphur. Graphitic schists and marbles from several other localities contain pyrite with relatively heavy compositions typical of diagenetic sulphides elsewhere in the North Atlantic region, which suggests that the additional source of sulphur was from the ambient seawater. The magmatic signature is however recorded in South Harris and Scardroy, which combined with the occurrence of rust zones in Palaeoproterozoic successions suggests that the region merits further exploration.
The Igarra area in southwestern Nigeria hosts a diverse suite of granitic rocks that play a significant role in understanding the regional geological framework. This study employs a comprehensive geochemical and petrogenetic approach to unravel these granitic rock's origin, evolution and geological implications. A comprehensive geochemical analysis was conducted on samples of the granitoids. The results showed moderate to high SiO2, Na2O and K2O, with average compositions of 68.95%, 3.50% and 4.09%, respectively. The total alkalis are characterised by low MgO, CaO, TiO2 and P2O5, consistent with metaluminous to weak peraluminous compositions. The granite primarily falls within the high-K calc-alkaline region, exhibiting distinctive patterns in rare earth elements, with notable depletion in Nb, P and Ti. Geochemical modelling suggests that the granitoids originated from incomplete melting of metasedimentary source rocks under low to moderate pressure conditions, with limited crustal contamination. Trace element discrimination diagrams indicate a collisional tectonic setting for the Igarra granitoids, interpreted to have formed during continental collision. This mixed-source model suggests a complex magmatic system involving both crustal and mantle contributions, with potential interaction between these diverse melt components during the formation of the granites. This study offers fresh perspectives on the evolutional setting of the Igarra granitoids, understanding the geological effect of the Pan-African belt in Southwestern Nigeria and its broader implications.
The granite pegmatites of Hmrat El Sorwhyia, situated in the northern Egyptian-Nubian Shield, are predominantly hosted within the central areas of syenogranitic bodies, with limited occurrences noted along the marginal sites. The Hmrat El Sorwhyia granitic pegmatites represent a notable example of rare-metal mineralisation. This study introduces novel bulk- rock compositions, including major, trace, and rare earth elements, to investigate and constrain the origin and mechanisms influencing the genesis of the Hmrat El Sorwhyia granitic pegmatites and their rare-metal mineralisation. The studied pegmatites exhibit diverse morphologies, featuring lenticular pockets that contain the highest radioelement concentrations. The maximum (equivalent uranium) eU value is 760 ppm while the maximum (equivalent thorium) eTh value is 5552 ppm. These pegmatites have granitic composition and peraluminous characteristics, indicative of A-type affinity associated with post-collisional tectonic settings, and are categorised as niobium–yttrium–fluorine-type pegmatites. The formation of granite pegmatites through fractional crystallisation during the late-stage magmatic processes involved the concentration of U, Th, rare earth elements, Zr, Y, and Nb. This concentration facilitated the crystallisation of thorite, uranothorite, columbite, cerianite, and zircon. Additionally, assimilation-fractional crystallisation mechanisms led to the exchange of accessory phases between successive injections of pegmatite and the surrounding wallrock, resulting in variable mineral concentrations. These open-system processes were responsible for the development of these pegmatites.
The petrographical and geochemical analyses of greywacke and siltstone samples from the Nampala gold deposit of the Paleoproterozoic Birimian supergroup, Southern Mali, have been carried out to make inferences on the provenance, tectonic settings, and weathering history of the sediments. Petrographical investigations revealed that greywackes can be classified as feldspathic wackes, with immature to moderately mature sediments, with the siltstones being immature. Geochemically, greywackes show features that resemble typical wacke sedimentary rocks, whereas the siltstones are arkose to litharenite. Overall, Nampala sedimentary rocks experienced low intensity of paleoweathering with <70 CIA and <90 CIW values and have not undergone significant sediment recycling having >1 CIV values. Their quartz and feldspar contents, together with the ratio of Al2O3/TiO2 and La/Sc, suggest the derivation of sediments from felsic igneous rocks, with a possible minor contribution from mafic proto-source rock. The petrographic and geochemical features of the greywackes and siltstones are consistent with siliciclastic rocks formed in an active continental margin, similar to other sedimentary rocks of the Paleoproterozoic Birimian terrane. These findings put positive constraints on the subduction-accretion geodynamic model proposed for the evolution of the Birimian terrane of the West African Craton.
The northwestern part of Gabal Um Ara granitic pluton is represents a good example for uranium occurrence in the southeastern desert of Egypt. Among the different lithologies in the study area, the granitic rocks attract attention for more detailed geological, geochemical and radiometrical studies. Um Ara granitic masses cover an oval outline area of about 300 km 2 , which is characterised by moderate topography. The granitic rocks are classified as monzogranite and alkali feldspar granite. Both of them belong to the post-orogenic younger granite magmatic activity that intruded the Egyptian shield between 620 and 530 Ma. The intrusion of Um Ara monzogranite and alkali feldspar granite appears to have been controlled by deep-seated tectonic zones and block faulting. The studied area lies at southeast of Aswan City between 22 ͦ 38′ 12˝–22 ͦ 38′ 34˝ N and 33 ͦ 47′ 27˝–33 ͦ 48′ 14˝ E. Geochemically, the average concentration of the elements in North Um Ara granite shows that the relative abundance decreases gradually with decreasing incompatibility from Rb to Y. The common features are enrichment in more mobile elements Rb, Th and U. The monzogranite shows the lowest U and Th content, whereas the alkali-feldspar shows an enhanced contents of both elements, with average Th/U ratio = 3.0. the alkali-feldspar exhibits an expanded enrichment of Th relative to U. The U of the alkali-feldspar may be included within the structure of the refractory accessory minerals. The northern part of the Um Ara granitoids has subjected to different types of alterations. The radiometric survey of the northwestern part of Gabal Um area granitic pluton revealed the presence of several radioactive anomalies near the contact with the Dokhan volcanic and metavolcanic rocks in the north. Some visible uranium mineralisation of uranium minerals occur mainly along the NW, NE, E-W and N-S joints, of a highly sheared alkali feldspar-granite. Uranophane is visible secondary uranium mineral, characterised by bright yellow lemon colours and occurs mainly as filling fractures and joints associated with violet fluorite, iron and manganese oxides. The radioactive and accessory minerals studying and X-ray diffraction analysis that of the mineralised alkali feldspar-granite granite in the northwestern part of Gabal Um Ara granitic pluton revealed include the presence of fluorite, zircon, columbite, spessartine garnet whereas, the secondary uranium minerals are represented by uranophane, β-uranophane and kasolite. The hydrothermal origin was proposed as two possible alternatives for this uranium mineralisation.
Investigation on the occurrence of magnetite ore minerals in Emure – Ekiti, Southwestern Nigeria was carried out by integrating magnetic and very low frequency electromagnetic (VLF-EM) methods on the suspicion that the major part of the magnetite ore being sought lies in the subsurface. Eight traverses in total were established with five traverses occupied in the northeast–southwest direction and the other three in the northwest–southeast direction. Six traverses were established across the exposed part of the pegmatite (magnetite) veins to serve as a control. Inter-station spacing of 1 m was chosen, so as not to miss any significant ore occurrence. The VLF-EM profile is a plot of the real and filtered real components. The KH-filter geophysical software was used to invert real data into a two-dimensional subsurface map that revealed variations in conductivity. The results of the geophysical interpretation for both methods indicate anomalous signatures observed on the exposed section of the pegmatitic veins, which are indicative of magnetite ore. These anomalous signatures align with certain zones along the Tr4 and Tr8 transects. Some of the high magnetic anomalies observed on traverse 5, 6, and 7 coincide with low conductivity suggesting the concentration of minerals such as quartz, microcline, plagioclase, and biotite, which are commonly associated with magnetite. The study has not only enhanced the mapping of the subsurface characterisation of the deposit but also confirms the reliability and suitability of using magnetics and VLF-EM geophysical methods for mapping magnetite deposits.
This study determines which predictors derived from geophysics or remote sensing data best generate a mineral prospectivity model (MPM) over Ghana's southern Kibi-Winneba belt in a scenario-based modeling case using Random Forest (RF) algorithm. Ten geophysically-derived predictors and six-remote sensing derived predictors were used as inputs in the first and second scenarios respectively. In the third case, the sixteen predictors derived from these afore-mentioned geoscientific datasets were used as inputs. Thus, three binary RF-based MPM were generated, and compared accordingly. The predictive performance in all three scenario-based RF-derived MPM produced was determined using the area under the receiver operating characteristic curve (AUC). AUC scores of 0.840, 0.785 and 0.809 respectively, were obtained for the first, second and third scenarios. The AUC scores obtained further indicates that, MPM developed based on using only the geophysics-sourced layers as inputs performed better in comparison with the MPMs generated in second and third scenarios.
The rare metals mineralisation in Um Safi area occurs in the acidic volcanics (mainly rhyolite and volcanogenic tuffs). The microscopic investigation revealed that they are highly altered and subjected to several alteration processes where the hydrothermal solution played the master role in redistribution of the rare metals. The mineralogical study configured three groups of rare metals mineralisation including: (a) rare metals of the radio-elements (thorite), (b) rare metals of the trace elements and REEs (zircon, xenotime, chernovite, ferro-columite, allanite, bastnäsite and cerianite) and (c) rare metals of the base metals (tungsten minerals and cassiterite). The assemblage of Wolframite–Heubnerite–cassiterite–copper and fluorite associated with sulfides indicating magmatic to hydrothermal transition mineralisation. The hydrothermal fluids rich in F and As cause the alteration of some primary minerals such as xenotime, allanite and wolframite into the secondary chernovite, bastnäsite and schellite, respectively. The study also clarified that the emplacement of granitic offshoots into rhyolite played an important role in the re-distribution of some rare elements.
The historical Encardideira gold mine, currently known as Chico Rei, represents a rare case of gold mine owned by a freed slave in Brazil's colonial times. The term 'encardideira' alludes to the property of ingraining dirt on the surface of something. Here, we provide chemical and mineralogical evidence that the Encardideira mine likely had its name from the begriming character of its ore shoots. Gold-mineralised samples are enriched in graphite C, identified as tourmaline-enclosed euhedral graphite, and Mn-oxide minerals, mostly pyrolusite and cryptomelane-like material. Measurements for Au by atomic absorption spectrometry returned Au values above 1 ppm only after cupellation, suggesting the existence of graphite-bound gold in pervasively oxidised rocks. It is hypothesised that graphite-rich ore shoots, with superposition of Mn-oxide minerals, could account for enough gold and softness for manual removal by enslaved miners and their characteristic begriming.
Less than half of the original two million km(2) of the Brazilian Savanna natural vegetation, called the Cerrado Biome, remains standing. Given its climate and socio-biodiversity importance, more effective public policies are needed to protect the remaining natural areas. In this paper, we present the methodology and results of the DETER Cerrado, an early warning deforestation system within the Cerrado region. The findings support that DETER is effective in detecting a wider range of deforestation patch sizes, from the larger patches, heavily associated with agricultural expansion, to the smaller areas (>1 ha <10 ha). Nevertheless, 80% of the deforestation is concentrated in the 10-km radius zone from the DETER Alerts. This area was later detected by the Cerrado Deforestation Monitoring Project (PRODES), the system that accounts for the annual deforestation rate assessment, which highlights the capability of the DETER system to provide support to the surveillance of deforestation in the Cerrado.
The Zvishavane Ultramafic Complex (ZUC) is a metamorphosed ultramafic-mafic body exposed within the Zvishavane gneiss complex in south central Zimbabwe. The complex hosts Africa's largest mine and reserves of high-grade chrysotile asbestos. Rock types of the ZUC range from serpentinites, metadunites, and metagabbros. Accessory chromites, which are altered to ferrian chromites, are hosted in metadunites and serpentinites. Chromium number, Cr# (100*Cr/(Cr + Al)), is extremely high, and ranges from 90.6 to 99.5. Low magnesium number, Mg# 100*Mg/(Mg + Fe 2+ ), ranges from 5.1 to 8.4. Most ZUC ferrian chromites occur as inclusions or marking the outlines of relict olivine crystals, and in veinlets traversing the serpentinites. On 100*Fe 3+ /(Al + Fe 3+ ) versus 100*Fe 2+ /(Mg + Fe 2+ ) diagram, the chromites all plot in the magnesioferrite field, and in the ferrian chromite field on a Fe 3+ -Cr-Al ternary diagram. On wt% Al 2 O 3 versus wt% Cr 2 O 3 and 100*Cr/(Cr + Al) versus 100*Mg/(Mg + Fe 2+ ) plots, chromites all plot in the modified trend fields. The bulk of the chromites were metamorphosed at temperatures of ≤500°C, and no samples experienced temperatures exceeding 550°C. A plot of Fe 3+ /(Fe 3+ + Fe 2+ ) versus wt% MnO is indicative of hydrous metamorphism of ZUC chromites. It is interpreted that extensive modification of the ZUC chromites occurred during hydrothermal alteration, under conditions more oxidising than quartz-fayalite-magnetite but less than magnetite-hematite, which accompanied the formation of high-grade chrysotile asbestos for which the ZUC is famous. Four granitic plutons exposed within 50km of ZUC were likely the source of hydrothermal fluids responsible for extensive hydrothermal alteration, which likely led to the formation of high-grade chrysotile asbestos, and almost completely modifying the chromites in the process. Compositions of accessory chromites in chrysotile asbestos meta-ultramafic bodies elsewhere are likely to be extremely modified.
This paper focuses on the geology and geochemistry of the Rhyacian Josephine gold deposit in northwestern Ghana, where gold is primarily hosted in quartzites, with other lithologies observed, including granitoids, mafic intrusions, and gneisses. Four deformational events, DJO0, DJO1, DJO2, and DJO3, are observed. DJO0 is synonymous with the primary preserved sedimentary crossbedding in the quarzitic rocks. Gold mineralization within the deposit is mainly associated with the DJO1 NNW-trending dextral and steeply dipping sinusoidal shear zone. Gold occurs primarily as free gold and invisible gold within the lattices of the disseminated arsenopyrite along the shear foliation planes of the host rock. The ore body geometry is 15-40 m wide and strikes 800 m in the NNW direction. Silicification, sericitization, chloritization, and sulphidation are the main alteration assemblages associated with the gold mineralization zones within the Josephine deposit. Pathfinder elements for gold are stibnite, tellurium, sulphur, copper, silver, and Lead.
Auriferous vein samples of the Angolan M'Popo deposit were characterized by a combination of 2D microscopy and 3D computed tomography (CT) in order to visualize and assess the gold distribution and gold morphology in in situ high-grade gold ore. The 0.1–2.4 m wide hydrothermal quartz veins in the Mesoproterozoic M'Popo granitic complex are composed mainly of quartz and pyrite, minor other sulfides and (visible) gold. The favourable X-ray attenuation/density contrast within this mineral assemblage allows delineation of the gold particle fraction so that gold particles of <0.01–19.95 mm³ in volume have been identified. Statistical analysis reveals that the bulk (∼99.98%) of all gold particles belong to the smallest volume classes (≤0.02 mm²) while large particles (>0.5 mm³) are few. The contrast between rounded, compact smaller particles and branched larger ones is clearly expressed in the CT reconstructions while transitions between these reflect a likely continuum in gold mineralization.
The current paper presents case study of the Budenovskoe sandstone-hosted uranium deposit, the host sequence of which has been modelled geostatistically, using Plurigaussian conditional simulation (PGS) and Sequential Gaussian conditional simulation (SGS). The PGS method minimises subjectivism of the geological interpretations, by constraining the lithological models to geostatistical and lithostratigraphic characteristics of the host sequence, and accurately reproduces litho-stratigraphy of the sedimentary sequence, realistically conveying its complexity. This was integrated with the rock permeability generated using SGS. Integrating two models has significantly enhanced definition of the fluid infiltration passages in the host sequence. The model was built using stochastic algorithms of PGS and SGS, and therefore can be used for estimation the project risk. In practice, the errors, initially estimated to the blocks used for the conditional simulation, are grouped to the volumes of a practical interest, including the resource and reserve domains, production blocks and the leach cells.
The investigated Phanerozoic volcanic (Gabal Um Itly, G. El Beida, G. Um Domi and G. Um Doweila) areas in the south Eastern Desert of Egypt of the Northern Arabian-Nubian Shield (ANS), have been a peralkaline affinity and display a continuous composition trachyte rocks. Geochemically, the studied rocks show significant negative anomalies in Ba, Sr, and Ti on the primitive mantle normalized trace element plot, indicating an ancestry involving plagioclase and Fe-Ti oxide fractionation. The concentrations of uranium mineralization and rare earth elements in the trachyte rocks is related to the presence of uranophane, kasolite, umohoite, autunite, monazite and allanite. The distribution of uranium, thorium and their ratios in the trachyte rocks reflects a direct strong relation, which suggests that U distribution is, at least in part, governed primarily by magmatic processes and disturbed later by a hydrothermal solution.
