MENVSC / Department of Ecology and Resource Management / See the attached abstract below

MESMEG / Department of Mining and Environmental Geology / Literature indicated that several mineralogical identification studies have been carried out on clays but few have focused on the characterisation of geophagic materials from South Africa. Large quantities of earth materials are consumed daily in Mashau Village, however, their mineral content and geochemical compositions had not been determined. Moreover, though the consumption of geophagic materials is very common in the village, the associated health implications had not been addressed. Thus, the main aim of the research was to mineralogically and geochemically characterise geophagic materials commonly ingested in Mashau Village and infer on possible health implications that could result from their consumption. Questionnaires were administered to geophagists in the study area with the aim of generating data on the prevalence of geophagia and the motivations for the practice. Geophagic soils and their parent rocks (for determination of provenance) were sampled and analysed for mineralogical and geochemical content. Geophagic soil samples were subjected to the following physicochemical analyses: colour, particle size distribution, pH, cation exchange capacity (CEC) and electrical conductivity (EC). An x-ray diffractometer (XRD) was used for mineralogical analysis while major oxides and trace elements abundances were determined using x-ray fluorescence (XRF) spectrometry and laser ablation inductively coupled mass spectrometry (LA-ICP-MS), respectively. Furthermore, provenance of the geophagic materials was determined using data obtained from mineralogical and geochemical analysis. Inferred health implications were based on the physico-chemical, mineralogical and geochemical data obtained. Outcomes of the questionnaire survey revealed craving to be the motivation for geophagia in Mashau Village. Although the practice seemed to be prevalent in females of certain ages, it was certainly not limited to gender, age, educational level or socio-economic status. Out of the 20 geophagic samples, 3 samples were brown, 2 had a strong brown colour and another 2 had a light olive brown colour. Other soil colours were less common, as each colour was only observed in one sample. The sand fraction dominated the samples; the clay content was low, giving the samples a sandy clay loamy texture. The pH of the soil ranged from being slightly acidic (5.4) to being slightly alkaline. The CEC values were very high ranging from 17 t0 109 meq/100 g. vii The EC values were also high (ranging from 11.2 to 245 μS/cm) indicating a high amount of soluble salts. Mineralogical analysis of geophagic soils identified quartz, microcline, plagioclase, hornblende, dolomite, muscovite, kaolinite, smectite, talc, anatase, hematite, ilmenite, chlorite and epidote with quartz and kaolinite being the dominant minerals. Actinolite, augite, chlorite, epidote, forsterite, magnetite, muscovite, plagioclase, quartz, sepiolite and microcline were the minerals identified in rock samples. Geochemical analysis for major oxides content (SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5 and Cr2O3) indicated that both geophagic soils and parent rocks were mainly composed of silica and alumina. Trace elements geochemistry showed a depletion of LREEs and an enrichment of HREEs in geophagic soils. The results also revealed that the REEs were enriched in the bulk fraction than in the clay fraction. Relative to the Upper Continental Crust (UCC) compositions, the concentrations of trace elements in geophagic soils were generally low. Provenance determination results showed that geophagic soils in Mashau were derived from basalts and sandstones. Majority of the samples were formed as a result of intense weathering while some were as a result of intermediate weathering. The negative health implications of the studied materials could include perforation of the colon, damage of the dental enamel and anaemia. However, geophagic materials could also be a good source of mineral nutrients and beneficial for reduction of nausea during pregnancy. / NRF

MESMEG / Department of Mining and Environmental Geology / Vhembe District has several clay deposits which are traditionally use for clay products such as burnt bricks without taking into account the chemical and mineralogical characteristics of clay being used. The ever-increasing market demand for these clay products cannot be met with the traditional method of clay utilization due to the paucity of scientific information on properties of the clay in the area. Consequently, there is a need to gain better understanding of the characteristics of the clay in Vhembe District and to establish the suitability of the variety of clay for different purposes. The current study was undertaken to better understand the compositional relationship between the clay deposits and surrounding rocks present in the study area. It further aimed at characterizing the clay deposits on the basis of chemical, mineralogy, physical, mechanical, thermal and micro structural properties with a view of evaluating the clays for possible industrial use. A total of thirty-nine clay and rock samples were collected from thirteen different locations across the Vhembe District. Thirteen representative samples from each location were obtained after thorough mixing until homogenization was attained and then quartered for subsequent analyses. The mineralogical and chemical characteristics of the clay and rock samples were determined using XRD and XRF respectively. Thin-sections of the rock samples were prepared and examined under petrographic microscope to better understand the mineral assemblages present in the rocks. The thermal and micro structural properties of the clays were determined using DTA-TGA and SEM analyses and the physical properties which include colour, cation exchange capacity (CEC) and soil pH were assessed. The particle distribution and Atterberg limits tests of the clay samples were also conducted in order to establish their mechanical properties. The petrographic results showed that the clay deposits exhibited an intense weathering and sedimentation processes which incorporated detrital minerals from the surrounding rock units. The rock units which include basalt, granodiorite, gneiss and quartzofeldspathic gneiss were found to be differentiated from subalkaline and/or tholeiitic magmatic composition. Although the value of SiO2 content in rock samples was higher when compared with clay samples, it indicated an ongoing desilicication and allitization processes. The high values of chemical index of alteration (CIA), low values of K/Cs (<6200), Ce* normalized value and higher values of LILE enrichment in the clay deposits indicated oxidizing environments during period of deposition. v The mineralogical composition of the studied clayey deposits showed that smectite (8.25 - 29.32%), kaolinite (14.91 - 59.26%) and chlorite (5.94 -16.54%) were present as clay minerals although associated with other non-clay minerals such quartz, plagioclase, talc and geothite. The chemical composition results revealed high silica and alumina content in most studied clay samples. Their fluxing oxides which include K2O, Na2O, CaO, and MgO, varied slightly from 0.06% to 1.78% in abundance while the Fe2O3 and TiO2 contents in most samples averages at 9.2% and 1.3% respectively. The plasticity index of the studied deposits ranged from 9.50 to 62.00% while liquid limit ranged from 31.34 to 73.62%. The microanalysis using SEM indicated that the microstructure framework of most studied clay exhibited a porous skeleton structure owing to numerous tiny voids. The composite results of SEM and CEC analyses suggested their possible application in water filter and chemical fertilizer industries since they provided passage for water and soil cations transmission. The particle size distribution demonstrated that the studied soils have clayey silt texture with wide range coverage of the well graded and sorted particle sizes. Compressibility and plasticity properties were found to be high in Mukondeni, Mashamba-1, Mashamba-2 and Mashamba-3 clay samples. The thermal behavior of Mukondeni, Mashamba-1, Mashamba-2 and Mashamba-3 samples showed relatively high shrinkage (>9%). The high shrinkage percentage suggests the preponderance of smectite minerals. Other samples which are rich in kaolinite and chlorite minerals exhibited low shrinkage (<2%). The drying trends of the studied clay suggest their suitability for fast drying processes like soft and hard refractoriness, sanitary wares and ceramics. Empirical assessment of most studied clay showed their suitability for pottery-making and manufacturing of roofing tiles and masonry bricks. / NRF