Research Articles (Geology)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1738

A collection containing some of the full text peer-reviewed/ refereed articles published by researchers from the Department of Geology

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Limited reactivity of pyroxene and plagioclase in batch experiments with supercritical CO2 in the presence of NaCl and NaHCO3 in the context of CO2 sequestration via carbonation
(Springer, 2025-02) Nkosi, Zakhele H.; Altermann, Wladyslaw; Pölmann, Herbert; Doucet, Frédéric J.
One-step high-pressure and high-temperature direct aqueous mineral carbonation of tailings derived from mining of Platinum Group Metals in South Africa requires a fundamental understanding of the reactivity of the most dominant mineral phases, i.e. pyroxene and plagioclase (66 wt. % and 12 wt. % of the bulk rock respectively) that are typically found in these tailings. The silicate minerals pyroxene and plagioclase were sampled from a pyroxenite footwall mined with the ore-bearing UG2 and from the Merensky Reefs outcropping in the eastern limb of the Bushveld Complex. These pyroxene and plagioclase grains were concentrated by gravity separation from the orthopyroxenite bulk rock and batch-reacted in a sodium chloride (NaCl) brine saturated with pure carbon dioxide (CO2) gas-only or seeded with sodium bicarbonate (NaHCO3; as an additional CO2 source) for 13 days at 100 °C and 10 MPa. Pyroxene dissolved slightly but no weathering features were observed in plagioclase. Analyses of the filtrates obtained from the pyroxene sample in the absence of NaHCO3 showed an increased concentration of magnesium and calcium ions in the solution. However, they had also reached a cation saturation sealing. On the other hand, liquid samples from reactions where both CO2 gas and NaHCO3 were added to the solution exhibited a pronounced decrease in dissolved magnesium and calcium ions. XRD patterns of some of the post-reaction solids collected from the cation-depleted solution aliquots showed peaks of newly formed secondary magnesite and vermiculite. Moreover, the presence of magnesite was further confirmed by Raman shift analysis of the dried solid products. The formation of secondary magnesite was observed only in the experiments seeded with NaHCO3, specifically where the pre-reaction solid was pyroxene rich. Some of the resultant fluid chemistry was corroborated by the geochemical model that simulated the reaction parameters using the Geochemist Work Bench (GWB) software. Overall, the results indicate low pyroxene dissolution, which leads to limited carbonation. These findings suggest that the carbonation of PGM tailings may be constrained under the evaluated physicochemical conditions.
Weathering profile of completely weathered rock from the Dullstroom Formation, South Africa
(Springer, 2025-05) Swart, Duan; Dippenaar, Matthys Alois
This study investigates the weathering profile of completely weathered rock derived from the Dullstroom Formation in South Africa. The research emphasizes the significance of the soil-rock interface, particularly the transition between completely weathered rock and residual soil, in understanding mechanical, chemical, and hydraulic behaviours. Field sampling and laboratory analyses, including particle size distribution, Atterberg limits, X-ray fluorescence (XRF), X-ray diffraction (XRD), and X-ray Computed Tomography (XRCT), were conducted. XRCT proved invaluable in visualizing pore geometry, density contrasts, and the persistence of relict rock structures in three dimensions. The findings highlight how structural prominence decreases with increasing weathering intensity, influencing compressibility and porosity. The compressibility of the material correlates better with chemical weathering indices than traditional geotechnical parameters like void ratio or dry density. These insights contribute to the geotechnical characterization of weathered rock profiles and propose structural prominence as a novel parameter for evaluating mechanical behaviour across weathering stages.
Downscaling and validating GLDAS groundwater storage anomalies by integrating precipitation for recharge and actual evapotranspiration for discharge
(Elsevier, 2024-08) Viviers, Cindy; Van der Laan, Michael; Gaffoor, Zaheed; Dippenaar, Matthys Alois; cindy.viviers@tuks.co.za
STUDY REGION : The Steenkoppies Catchment is located approximately 75 km southwest from Pretoria, South Africa (RSA). STUDY FOCUS : This study tested a framework for downscaling Global Land Data Assimilation System (GLDAS-2.2) groundwater storage anomaly (GWSA) estimates from 0.25◦ to 0.05◦. This was achieved in Google Earth Engine using the Random Forest algorithm with only precipitation and actual evapotranspiration (ETa) as input variables. Additionally, the study assessed whether accounting for temporal lags could minimise residuals and enhance model performance. NEW HYDROLOGICAL INSIGHTS FOR THE REGION : The greater range of downscaled GWSA values indicated that the product effectively captured local recharge (precipitation) and discharge (ETa) variations while maintaining conservation of mass. Optimising the temporal correlation (r) between input variables resulted in lower residuals and fewer outliers. Groundwater level measurements and downscaled estimates for the hard rock aquifer showed larger amplitudes and seasonality and yielded the highest r (0.6) and lowest RMSE (40 mm) and MAE (31 mm). Measurements near the spring and in the karst aquifer showed less evident amplitude and seasonality. The in situ derived and downscaled GWSA comparison demonstrated the effectiveness of the product for monitoring storage declines. When applied over aquifers experiencing significant land use change or belowaverage precipitation, the approach could monitor groundwater storage changes, even with limited in situ observations. The adaptable code is available for application in other study areas.
The subduction-related metavolcanic rocks of Maroua, northern Cameroon : new insights into a neoproterozoic continental arc along the northern margin of the Central African Fold Belt
(MDPI, 2024-11) Biakan à Nyotok, Pierre C.; Gountié Dedzo, Merlin; Djamilatou, Diddi H.; Lenhardt, Nils; Klamadji, Moussa N.; Fosso Tchunte, Periclex M.; Kamgang, Pierre
Please read abstract in article.
Multi-parameter investigation of Cretaceous to Palaeocene sedimentary sequences in the Anambra and Niger Delta Basins, Nigeria : organic matter characterisation, palynofacies and implications for palaeoclimate and sea-level changes
(Wiley, 2025-01) Omietimi, Erepamo J.; Lenhardt, Nils; Yang, Renchao; Götz, Annette E.; Edegbai, Aitalokhai J.; Bumby, Adam John; nils.lenhardt@up.ac.za
The Anambra Basin of Nigeria, part of the larger West and Central African Rift System (WCARS) across Africa, contains primarily Cretaceous to Palaeocene shallow to marginal marine and freshwater sedimentary deposits. The organic-rich deposits of the Cretaceous Nkporo and Mamu formations within the Anambra Basin and the Palaeocene Imo Formation of the Niger Delta Basin constitute important conventional source rocks. Despite its economic significance, research on organic matter characterisation, palynofacies, sea-level fluctuations, palaeoclimate, hydrogeography, basin restriction, palaeobathymetry and the factors controlling organic matter preservation remains largely undocumented. The here presented new inorganic and organic geochemical and organic petrography data of the Cretaceous to Palaeocene deposits serve to refine the regional interpretation at a basinal scale and within the supra-regional context of the WCARS. Geochemical palaeotemperature proxies suggest a warm and humid tropical palaeoclimate during the Late Cretaceous within the study area. Furthermore, the measured TOC values indicate poor to very good organic content. Palynofacies analysis revealed high abundances of opaque and translucent phytoclasts and low amounts of palynomorphs with negligible amorphous organic matter (AOM) in the studied mudrocks. Two palynofacies groups suggest shallow-marine conditions in a proximal shelf setting and a heterolithic oxic basin. The palynofacies of the upper Imo Formation reveal higher percentages of dinoflagellate cysts during the early highstand phase, with equidimensional, opaque phytoclasts representing the maximum flooding phase, accompanied by warmer conditions. Additionally, abundant terrestrial phytoclasts, Deltoidospora spp., Classopollis spp. and geochemical indicators collectively indicate warm tropical climatic conditions consistent with geochemical interpretations. The palaeobathymetry reconstructions suggest a shallow seaway during the Upper Cretaceous in the Anambra Basin.
Magnetite geochemistry as a proxy for metallogenic processes : a study on sulfide-mineralized mafic-ultramafic intrusions peripheral to the Kunene Complex in Angola and Namibia
(Springer, 2025-03) Milani, Lorenzo; Oosthuizen, Lize; Owen-Smith, Trishya M.; Bybee, Grant M.; Hayes, Ben; Lehmann, Jeremie; Jelsma, Hielke A.; lorenzo.milani@up.ac.za
Trace element concentrations in magnetite are dictated by the petrogenetic environment and by the physico-chemical conditions during magmatic, hydrothermal, or sedimentary processes. This makes magnetite chemistry a useful tool in the exploration of ore-forming processes. We describe magnetite compositions from Ni-Cu-(PGE)-sulfide mineralized rocks from seven mafic–ultramafic intrusions peripheral to the Mesoproterozoic AMCG (anorthosite-mangerite-charnockite-granite) suite of the Kunene Complex of Angola and Namibia to investigate metallogenic processes through the geochemical characterization of Fe-oxides, which were analyzed in-situ via Electron Probe Microanalysis (EPMA), and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). We identified magmatic magnetite, segregated from both a silicate liquid and an immiscible sulfide liquid. Elements like Cr, Co and V suggest that the sulfide-related magnetite segregated from a relatively primitive Fe-rich monosulfide solid solution (MSS). Secondary Cr-rich magnetite appears in intrusions with abundant chromite or Cr-spinel. Two types of hydrothermal magnetite were identified, related to the pervasive replacement of sulfides and a late-stage, low-T fluid circulation event. Magnetite replacing sulfides is associated with serpentinized ultramafic rocks and is preferentially observed in the intrusions with the highest base and precious metal tenors. The high concentration of Ni, Co, Cu, Pd, As and Sb in these grains is corroborated by the identification of micron-size PGE mineral inclusions. We infer that serpentinization during hydrothermal fluid circulation was accompanied by desulphurization of sulfides with metal remobilization and reconcentration to generate magnetite carrying Pd microinclusions. We suggest that the highly serpentinized ultramafic rocks in the Kunene Complex region may become a possible target for economic Ni- Cu-(PGE) mineralization.
Seismic hazard assessment in the Podhale region, Poland—zone and smoothed seismicity approach
(Springer, 2024) Plesiewicz, Beata; Wiszniowski, Jan; Karkowska, Kamila; Kijko, Andrzej
Poland is characterised by weak natural seismicity. However, the last analysis of the natural seismic hazard in the country was carried out 24 years ago. Therefore, a significant fraction of the recorded seismicity is not included in the hazard estimates currently used, either because recent observations are not taken into account or because of improved seismic network capabilities. Furthermore, podhale, in the Tatra Mountains, is the only region with recorded permanent natural seismicity. This study aims to create new seismic hazard maps of the Podhale region from a newly compiled database containing information on historical events and two complete instrumental catalogues (regional and local), each at a different level of completeness. The local catalogue was recorded over the last few years. Two seismic hazard assessment techniques were applied, namely the conventional (zone-based) (Cornell in Bull Seismol Soc Am 58(5): 1583–1606, 1968) and the smoothed seismicity model, based on the spatial distribution of seismicity. The earthquake recurrence parameters were estimated using the methodology developed by Kijko et al. (Bull Seismol Soc Am 106: 1210–1222, 2016). The new seismic hazard model incorporates several improvements, such as a comprehensive logic tree and a new set of ground motion models. The new maps provide a more detailed assessment of the seismic hazards of the investigated area. Moreover, they predict higher PGA than previous seismic hazard maps covering Podhale, like global European Seismic Hazard Maps 2013 and 2020.
Mineralogical impact on the compaction of residual gabbro soils in the construction of platinum tailings storage facilities
(Springer, 2024-12) Tunnell, Jason; Dippenaar, Matthys Alois; matthys.dippenaar@up.ac.za
Over the past decade, there have been 45 tailings storage facility (TSF) disasters worldwide resulting in fatalities, serious environmental damage, and the destruction of entire ecosystems. These failures often stem from substandard design or operational practices. Many TSFs are constructed in regions associated with intrusive mafic rocks such as gabbro, norite, pyroxenite, and anorthosite, which are commonly found alongside platinum group metals in areas like the Bushveld Igneous Complex in South Africa and the Great Dyke in Zimbabwe. The stability of these structures can be significantly influenced by the residual soils present at the construction sites. Residual soils, both cohesive and non-cohesive, contain varying quantities of different minerals, which can impact the compaction characteristics and, consequently, the stability of the TSF foundations. Cohesive soils rich in clay minerals, such as kaolinite and smectite, exhibit properties that can hinder effective soil compaction. The expansive nature of smectite due to its ability to absorb large amounts of water and host free exchangeable cations counteracts the compaction process, reducing soil stability. Soil compaction is a complex process influenced by several factors, including compaction effort, method, water content, particle size distribution, and mineralogy. This study aimed to analyse these factors using a series of laboratory tests, including foundation indicators, MOD AASHTO compaction testing, and X-ray diffraction analysis, on residual soils from two TSF construction sites. The findings revealed that soils with high clay content tend to retain more water and have a higher optimum water content, adversely affecting their compaction properties. This study highlights the critical need to consider the mineralogical composition and weathering effects of residual soils in the design and construction of TSFs. By improving our understanding of these factors, we can enhance the stability of TSF foundations, reducing the likelihood of future failures. The insights gained from this research highlight the importance of thorough geotechnical assessments in the successful design and maintenance of TSFs.
The South African Statistical Association and its role in science in South Africa
(Academy of Science of South Africa, 2024-11) Fabris-Rotelli, Inger Nicolette; Smit, Neill; Potgieter, Cornelis J.; Fatti, Paul; Blignaut, Renette J.; Hastie, Trevor; Coetzer, Roelof; Chhana, Yoko; Le Roux, Niël; Lubbe, Sugnet; Reddy, Tarylee; Debba, Pravesh; Ferreira, Johan; Haines, Linda; Thiart, Christien; Farrar, Thomas; Sharp, Gary; Smit, Ansie; Jenneker, Ashwell; Morey, Liesl; Booyse, Mardé; North, Delia; Neethling, Ariane
The South African Statistical Association (SASA) turned 70 years old in 2023, having made huge impacts in South Africa and beyond. Through SASA, the statistics community in South Africa has made significant strides in the field, both locally and internationally, ensuring the importance of the discipline is concreted into the academic and industry playing fields. The statistics community continues to grow and remains passionate about growth and development of school learners, undergraduate and postgraduate students, academics and statisticians in industry. The opportunities for statisticians in South Africa are endless, and important to the economic sustainability of South Africa. This paper provides an historical overview of the impacts of the South African Statistical Association and statistics in South Africa.
Reactivity of a plagioclase concentrate from the South African Bushveld Igneous Complex via extractive acid leaching vs. extractive roasting-leaching processes
(Springer, 2024-10) Mohamed, Sameera; Van der Merwe, Elizabet Margaretha; Nkosi, Zakhele; Altermann, Wladyslaw, 1954-; Grote, Wiebke; Doucet, Frédéric J.
This study compared the reactivity of a plagioclase concentrate subjected to two processes: (1) direct acid leaching and (2) thermochemical treatment with ammonium sulfate followed by leaching. The sample was prepared from coarse-grained pyroxenite rock retrieved from the Bushveld Igneous Complex, South Africa. It contained 78% plagioclase (labradorite), 9% orthopyroxene (enstatite) and 13% quartz. The elements contained in the concentrate were categorized into three groups based on their susceptibility to direct acid extraction after 6 h of leaching. Group 1 consisted of the highly reactive main elements of plagioclase (Al, Ca and Na, with extraction efficiencies of 95%, 89% and 81%, respectively). Group 2 included elements predominantly present in enstatite (Mg and Fe with extraction efficiencies of 41% and 55%, respectively). Group 3 was composed of slowly extractable Si (25%) from mostly plagioclase. Increasing the duration of direct acid leaching to 24 h had no effect on the extraction of Group 1 elements, whereas the extraction of Mg and Fe (Group 2) increased to >60%, and that of Si (Group 3) increased from 25 to 80%. The latter correlated with the nearly complete disappearance of the plagioclase blueprint in the XRD pattern of the residues generated after 24 h of leaching. In contrast, plagioclase had limited reactivity with ammonium sulfate during thermochemical treatment. Direct acid leaching of plagioclase-rich tailings can therefore generate leachates to be used as precursors for the preparation of value-added products, such as silica nanoparticles via a sol–gel route and calcium aluminate nanoparticles via solution combustion.
An improved framework for detecting thyroid disease using filter-based feature selection and stacking ensemble
(Institute of Electrical and Electronics Engineers, 2024-06) Obaido, George; Achilonu, Okechinyere; Ogbuokiri, Blessing; Amadi, Chimeremma Sandra; Habeebullahi, Lawal; Ohalloran, Tony; Chukwu, C.W.; Mienye, Ebikella Domor; Aliyu, Mikail; Fasawe, Olufunke; Modupe, Ibukunola A.; Omietimi, Erepamo Job; Aruleba, Kehinde
In recent years, machine learning (ML) has become a pivotal tool for predicting and diagnosing thyroid disease. While many studies have explored the use of individual ML models for thyroid disease detection, the accuracy and robustness of these single-model approaches are often constrained by data imbalance and inherent model biases. This study introduces a filter-based feature selection and stacking-based ensemble ML framework, tailored specifically for thyroid disease detection. This framework capitalizes on the collective strengths of multiple base models by aggregating their predictions, aiming to surpass the predictive performance of individual models. Such an approach can also reduce screening time and costs considering few clinical attributes are used for diagnosis. Through extensive experiments conducted on a clinical thyroid disease dataset, the filter-based feature selection approach and the ensemble learning method demonstrated superior discriminative ability, reflected by improved receiver operating characteristic-area under the curve (ROC-AUC) scores of 99.9%. The proposed framework sheds light on the complementary strengths of different base models, fostering a deeper understanding of their joint predictive performance. Our findings underscore the potential of ensemble strategies to significantly improve the efficacy of ML-based detection of thyroid diseases, marking a shift from reliance on single models to more robust, collective approaches.
Zircon U-Pb and Lu-Hf isotopes reveal the crustal evolution of the SW Angolan Shield (Congo Craton)
(Elsevier, 2024-07) Ferreira, Ezequiel; Lehmann, Jeremie; Rodrigues, José Feliciano; Hayes, Ben; Merino-Martínez, Enrique; Milani, Lorenzo; Bybee, Grant M.; Smith, Trishya M.O; García-Lobón, José Luis; Tassinari, Colombo C.G.; Ueckermann, Henriette; Sato, Kei; Silva, Paulo Bravo; Correia, João; Labaredas, José; Duarte, Laurent; Molekwa, Mmasetena A.; Manuel, José; da Mata Lourenço Victorino, Américo
The crustal evolution of the Angolan Shield (AS) remains poorly constrained. To address this, we analysed U-Pb and Lu-Hf isotopes in detrital and igneous zircons to investigate the age and provenance of extensive sedimentary strata in southwestern Angola and use it as a proxy to gain insight into the Archean to Mesoproterozoic evolution of the region. Mesoproterozoic maximum depositional ages for the Iona (<1323 ± 13 Ma), Ompupa (<1215 ± 13 Ma), and Cahama (<1184 ± 23 Ma) siliciclastics challenge previous correlations with the Paleoproterozoic Chela Group. Provenance analysis reveals that the Mesoproterozoic strata were derived internally from the AS. Our combined dataset indicates that the widespread Eburnean magmatism (∼2.05–1.93 Ga) resulted from reworking of Archean crust, possibly in collision orogens. A major increase in the εHf(i) and εNd(i) values at ∼ 1.87–1.73 Ga indicates a change in geodynamics, with magmatism of the Epupa–Namibe Metamorphic Complex (ENMC) generated in an extensional accretionary orogen at the southern margin of the Eburnean–Archean crustal block. Magmatism resumed in the Mesoproterozoic (∼1.56–1.50 Ga), with suprachondritic εHf(i) values indicating significant juvenile addition. The Kunene Complex (KC: ∼1.50–1.36 Ga) anorthosite-mangerite-charnockite-granite magmatism displays variable εHf(i) and εNd(i) values, consistent with mixing between reworked ENMC-crust and juvenile melts in a long-lived accretionary orogen back-arc region. Post-KC (∼1.36–1.30 Ga) magmatism shows an increased juvenile contribution, potentially linked to partial melting of ENMC and ∼ 1.56–1.50 Ga juvenile crust during an orogenic event, or alternatively, related to renewed slab retreat and back-arc extension. The Hf isotopic compositions of ∼ 1.29–1.18 Ga zircons are compatible with a renewed input from the depleted mantle and/or reworking of the earlier ∼ 1.56–1.50 Ga juvenile crust. Emplacement of ∼ 1.13–1.10 Ga mafic dikes/sills marks the end of Mesoproterozoic magmatism in the AS. Our new data enhance our understanding of the Archean to Mesoproterozoic crustal evolution of the AS. Keywords: SW Angolan Shield; Archean to Mesoproterozoic; Detrital and igneous zircon; U-Pb and Lu-Hf isotopes; Crustal evolution.
Base-level fluctuation controls on migration of delta lobes : a case study from the paleogene Shahejie formation in the Huimin depression, Bohai Bay Basin, NE China
(MDPI, 2023-02) Yang, Renchao; Li, Yang; Wu, Xuepeng; Di, Jianqiang; Zhang, Junjian; Lenhardt, Nils
Sandbody distribution patterns and controls are the most important foundation for petroleum exploration and development, particularly in a lacustrine basin with rapid changes in the sedimentary environment. To provide sedimentologists and petroleum geologists around the world with an analogue for sandstone reservoir prediction, the sedimentary facies of the fourth member of the Shahejie Formation (Sha-4 Member) in the Huimin Depression of the Bohai Bay Basin were analyzed, and the sequence stratigraphic framework was established based on characteristics of spontaneous potential logs and lithology. According to the findings of this study, the Sha-4 Member’s sedimentary environment was dominated by delta front and shallow lake facies. Delta front sandbodies were discovered to retrograde before prograding again throughout the established profile. The Sha-4 Member in the Huimin Depression is divided into a third-order sequence (LSC1), which can be further divided into four fourth-order sequences (MSC1 to MSC4), corresponding to the four sub-members (S4-1 to S4-4). During the development of the MSC1 to MSC4 sequences, the delta depositional scale first decreased and then increased with the changing base level. The maximum flooding surface developed within the MSC3 sequence. The Sha-4 Member sequence model reveals that the deltas in the study area exhibit self-similarity, and delta sandbodies are primarily developed in the MSC1, MSC2, and MSC4, whereas mudstone is largely developed in the MSC3.
Tracing mine water flows in a dolomite quarry, South Africa, using hydrochemistry and stable isotopes
(Springer, 2024-06) Diamond, Roger; Van Staden, Christel; Dippenaar, Matthys Alois
South Africa has a growing population, a relatively dry climate, and abundant mining activity, all of which increase the importance of water management. The Mooiplaas Dolomite Quarry, south east of Pretoria, has been mining metallurgical grade dolomite since 1969, within the productive karst aquifers of the Malmani Subgroup, Transvaal Supergroup. This study was conducted to elucidate the flow of water around the site, including the mine water and groundwater. The site was investigated by sampling precipitation, surface water, groundwater, and mine water for hydrochemical and stable isotope analysis from 2011 to 2017, totalling over 400 samples. Levels of nitrate in groundwater and mine water were marginally above drinking water limits, from explosives residues, and ammonia in the nearby Hennops River was unacceptably high due to municipal sewage outfalls, but otherwise, water quality was very good. Alkalinity from rock weathering, aided by crushing of dolomite, was the main control on water chemistry. Combined analysis of dissolved matter (TDS, nitrate, Mg, etc.) suggested that the dewatering of the mine and resultant recharge from the slimes dams caused an aerated zone of groundwater, which mixed with regional groundwater flowing beneath the site. Stable isotopes, with an evaporated signature from the mine open water bodies, also showed how mine operations cause recharge to groundwater and subsequent seepage back into the pit lakes. The mine appears not to contaminate the regional groundwater; however, mine designs should avoid situations where process water flows via groundwater back into pits, causing excessive dewatering costs.
Elemental geochemistry of Cretaceous deposits in the Dahomey Basin (Nigeria) : implications for paleoclimatic and paleoenvironmental reconstructions
(Elsevier, 2024-08) Johnson, Temitayo D.; Oluwajana, Oladotun A.; Omietimi, Erepamo Job; Ayo-Bali, Abiodun E.; Odondiri, Oyinebielador D.; Igili, Chinedu O.; Lenhardt, Nils; erepamo.omietimi@tuks.co.za
Please read abstract in the article.
Catalogue of South African mine tailings for geochemical carbon dioxide removal purposes
(Elsevier, 2023-03) Bullock, Liam A.; Nkosi, Zakhele H.; Vele, Nkosi; Amponsah-Dacosta, Maxwell
South Africa has the potential to be a global leader in implementing strategies targeting geochemical carbon dioxide removal (CDR) using mine tailings, utilising methods for alkalinity production and mineral carbonation. This is due to the hundreds of millions of tonnes of geochemically and mineralogically suitable tailings produced annually from diamond, PGM, chrome, nickel, phosphate, copper, talc and magnesite mines, exploiting mafic and ultramafic rocks. This approach may offer an additional route towards emissions offsets and reduction targets for South Africa. Here, a catalogue of tailings has been developed to highlight overall national CDR potential, drawing attention to site opportunities for pilot schemes. It has been calculated, using bulk geochemistry and shrinking core modelling, that South Africa has an average 1.1-1.7 MtCO2 removal capacity per year across all suitable sites, while an additional 11-17 MtCO2 could be removed through weathering historic tailings. The total CDR that could be achieved over the 2030-2100 period, considering all annually produced tailings available to weather, is 79-119 MtCO2. The capacity may be higher if mines of limited production information are considered, and pre- 2017 tailings production amounts, abandoned stockpiles, and other industrial by-products are included. Diamond mines hold the highest geochemical CDR capacities, along with high tailings producers in Phalaborwa, Nkomati and Mogalakwena metal mines. There are incentives for academia, industry and policymakers to revise the geochemical CDR potential of mine sites in the years to come, and for other countries to catalogue their own suitable tailings and geochemical CDR potential capacities for future Mt-scale opportunities.
GIS‑assisted flood‑risk potential mapping of Ilorin and its environs, Kwara state, Nigeria
(Springer, 2023-12) Alimi, S.A.; Oriola, E.O.; Senbore, Samson Sanya; Alepa, V.C.; Ologbonyo, F.J.; Idris, F.S.; Ibrahim, H.O.; Olawale, Lovelyn Olawumi; Akinlabi, O.J.; Ogungbade, O.
The incessant reoccurrence of flooding disasters across Nigeria has mandated an urgent outlook on food-risk management techniques. Ilorin and its environs have suffered immensely from annual food reoccurrence. This study aims to assess food risk within Ilorin and its environs and proffer adequate food mitigation strategies that governments and policymakers can adopt to placate future flooding events within the state. Satellite imagery data were acquired and analyzed for food-risk assessment of the area. Ten highly influential food causative factors were synergized using Multi-Criteria Decision-Making techniques in this research; they are Land Surface Temperature, Elevation, Soil Moisture Index, and Distance to Stream, Drainage Density, Stream Power Index, Normalized Difference Vegetation Index, Land Use Land Cover, Slope, and Topographic Wetness Index. Findings showed that approximately 47.2% of the study area had low food risk, while moderate and high food-risk zones occupied 33.5% and 19.29%, respectively. Most parts of Ilorin and its environs are safe from food disasters; only about one-quarter of the total area under investigation lies in the high food-risk zones; these areas mostly fall within the shores of major streams, rivers, and dams within the state. A plot of previous food cases in the state placed the affected areas in the high and moderate zones of food risk, confirming the efficacy of geospatial techniques in food-risk assessment. It is hoped that this study's findings and recommendations can be implemented to prevent future devastating flooding occurrences within the state.
The Greater Cederberg-False Bay Large Igneous Province in South Africa : a southern node of widespread magmatism associated with South Atlantic rifting
(Geological Society of South Africa, 2023-12) Kingsbury, Cole G.; Altermann, Wladyslaw; Kramers, J.; Ernst, Richard E.; Söderlund, Ulf; Klausen, M.B.
Please read abstract in the article.
Microfacies analysis of the Palaeocene Lockhart limestone on the eastern margin of the Upper Indus Basin (Pakistan) : implications for the depositional environment and reservoir characteristics
(Wiley, 2023-02) Bilal, Ahmer; Yang, Renchao; Janjuhah, Hammad Tariq; Mughal, Muhammad Saleem; Li, Yang; Kontakiotis, George; Lenhardt, Nils
A detailed sedimentological analysis of the Palaeocene Lockhart Limestone has been conducted to evaluate the depositional environment, diagenetic processes and hydrocarbon potential of the eastern margin of the Upper Indus Basin. From bottom to top, there are three microfacies recorded. The lower microfacies, composed of fine-grained micrite and some diagenetic dolomite, reflect the low energy and calm palaeo-current in the shallower section (1–2 m) of the inner shelf close to shore. The middle microfacies contain algae that suggest 5–15 m of water depth, especially along the inner-middle shelf, but fractured and mixed bioclasts in micrite material indicate calm to moderately active water close to the wave base. Progressing from the lower microfacies to the middle microfacies, a gradual shift from orthochem to allochem components is observed. The top microfacies is dominated by massive benthic microfossils, indicating moderate energy-water conditions with normal salinity. However, the presence of limestone intraclasts surrounded by microspar, miliolids and nummulites at the top indicates a high-energy environment with increasing salinity and water depths from 20 to 130 m. These findings show that the Lockhart Limestone was deposited in a shallow shelf environment, spanning the inner-mid shelf. Diagenetic processes observed include micritisation, cementation, dissolution, replacement, physical and chemical compaction, and fracture filling by calcite cement. The Lockhart Limestone represents a deepening upward sequence deposited below the shelf margin system tract and highstand systems tract in a regressive environment that could reflect good reservoir characteristics, has the potential to serve as an excellent hydrocarbon reservoir rock, and could be a primary target for future hydrocarbon exploration.
Field tests for the identification of silts
(Springer, 2023-11) Swart, Duan; Dippenaar, Matthys Alois; Van Rooy, J.L. (Jan Louis); matthys.dippenaar@up.ac.za
Accurately identifying soil texture and understanding soil behaviour in terms of plasticity is a crucial initial step in properly characterizing a site, which in turn facilitates appropriate sampling and scheduling of laboratory tests. Soil identification techniques in literature are effective at assessing pure clays and silt–clay mixtures. This paper presents a comparative study between field tests, soil plasticity classifications, Atterberg limits, mineralogical and chemical data, SEM imagery, and stereographical microscopy. Natural residual soils comprising varying quantities of clays, silts, and sands were used and subjected to the same field and laboratory protocols. The findings of this study demonstrate that a series of field tests can effectively characterize and classify soils ranging from coarse soils to fine soils exhibiting non- to highly plastic indices with particle sizes less than 2.00 mm. By employing a single list of field tests that only necessitate water and commonly available stationery materials on-site, the researchers have presented a valuable tool for on-site determination of soil texture and inference of the Unified Soil Classification System (USCS). This approach streamlines the process and provides professionals with an efficient means of assessing soil properties and determining problem soils at an early stage of the investigation and during construction of high fills.

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