Vanadium ore resources of the African continent: State of the Art

As part of the critical metals group, vanadium is an essential commodity for the low- and zero-CO2 energy generation, storage and transport. This contribution aims to carry out a review of the known vanadium ore sources and mineralizations located in Africa, which are highly diversified in their geological and mineralogical characteristics, and can be classified in: 1. Vanadiferous (titano)magnetite deposits; 2. Sandstone-hosted (U)-vanadium deposits; 3. Calcrete-hosted (U)-vanadium deposits; 4. Vanadate deposits; 5. Graphite-associated vanadium deposits; 6. Vanadium occurrences associated with laterite, bauxite, and phosphate ores. The economically most significant vanadium sources in Africa are associated with titanomagnetite layers in mafic–ultramafic layered magmatic intrusions (e.g., the Bushveld Complex in South Africa and the Great Dyke in Zimbabwe). Vanadium has been historically mined also in vanadate deposits deriving from the supergene alteration of Pb-Zn-Cu sulfide ores in Namibia and Zambia. Several areas in these countries, where potentially re-processable old tailings and slags have been accumulated, still have economic potential. Vanadium mineralizations are associated with graphite bodies in the Mozambique Metamorphic Belt. Vanadium is also enriched in uranium ores occurring in the Upper Paleozoic-Mesozoic Karoo continental sediments: typical examples are found in Botswana, South Africa, and Zimbabwe. Significant uranium-vanadium concentrations (where carnotite prevails) occur in relatively recent (Tertiary-Quaternary) calcrete duricrusts in paleo-fluviatile beds, which are widespread throughout the African continent. These derive from the weathering of U-(V)-fertile source rocks, which under favorable paleoclimatic conditions resulted in the vanadium precipitation in the critical zone. Variable vanadium amounts have been also recorded in iron ore deposits, phosphorites, and laterites, even though the phosphate deposits seem to have the most favorable characteristics for potentially economic vanadium concentrations. On the whole, South Africa holds the most significant vanadium ore resources globally. However, also many other African countries, where this metal could be profitably extracted as a by-product from other economic ores, will probably be at the forefront of vanadium production in the near future

Investigating structure, magneto-electronic, and thermoelectric properties of the new d0 quaternary Heusler compounds RbCaCZ (Z = P, As, Sb) from first principle calculations

818-824The ab initio calculations based on the density functional theory (DFT) using the self-consistent full potential linearized augmented plane wave (FPLAPW) method were performed to explore the electronic structures, magnetic and thermoelectric properties of quaternary alloys RbCaCZ (Z = P, As, Sb) with quaternary Heusler structure. Results showed that FM-Y3 is the most favorable atomic arrangement. All the compounds are found to be half-metallic ferromagnetic materials with an integer magnetic moment of 2.00 μB, which predominantly derives from the strong spin polarization of p channels of C hybridized with Z elements. The predicted minority (half-metallic) band gaps were found to be 1.86 (0.87), 1.72 (0.78), and 1.78 (0.71) eV for Z = P, As, and Sb, respectively. Thermoelectric properties of the RbCaCZ (Z = P, As, Sb) materials are additionally computed over an extensive variety of temperature and it is discovered that all compounds demonstrates higher figure of merit. The half-metallic structures of these compounds with large band gaps and adequate Seebeck coefficients mean that they are suitable for use in spintronic and thermoelectric device applications

Petrogenesis of Eocene Tamazert continental carbonatites (Central High Atlas, Morocco): implications for a common source for the Tamazert and Canary and Cape Verde Island carbonatites

The Tamazert Eocene alkaline complex of the Central High Atlas Range of Morocco hosts the largest outcropping occurrences of carbonatites in northern Africa. The complex consists of carbonatites and undersaturated ultramafic to syenitic alkaline to peralkaline silicate rocks. Mineralogically and geochemically the Tamazert carbonatites are classified as calciocarbonatites, magnesiocarbonatites and silicocarbonatites.They are enriched in light rare earth elements and large ion lithophile elements (Cs, Rb, Ba, U,Th), but depleted in high field strength elements (particularly, Ti, Nb and Ta). Stable and radiogenic isotope ratios vary in the range of δ13CPDB=-5·8 to 1·8 0/00, δ18OSMOW=6·9-23·5 0/00, initial 87Sr/86Sr=0·7031-0·7076, 143Nd/144Nd=0·5125-0·5129 and 206Pb/204Pb=18·29-19·89. Calciocarbonatites intruding Jurassic limestones have the highest δ13C and δ18O values and the most radiogenic initial 87Sr/86Sr, but least radiogenic 143Nd/144Nd, 206Pb/204Pb and 208Pb/204Pb isotope ratios, and are interpreted to have interacted with the limestones (crustal components). The magnesio- and silicocarbonatites have Sr, Nd and Pb isotope ratios that are nearly identical to those of low-87Sr/86Sr calciocarbonatites. The isotope signature of the high-Sr, low-87Sr/86Sr calciocarbonatites with mantle-type O and C isotopic compositions indicates the presence of HIMU- and EMI-type components in the mantle source of the Tamazert carbonatites, similar to what has been proposed for the Cape Verde and Canary Islands.The close similarity in carbonatite composition between the Cape Verde and Canary Islands and Tamazert suggests a common sublithospheric source for these carbonatites. We therefore propose that theTamazert carbonatites originated through melting of Canary plume material that may have flowed through a sub-lithospheric corridor extending from the Atlantic near the Canary Islands to the Middle Atlas, formed by the delamination of the subcontinental lithosphere in response to Africa-Europe collision at c. 42Ma. Seismic tomography data suggest that the common source may be within the lower mantle at depths >1000 km

Toward Male Individualization with Rapidly Mutating Y-Chromosomal Short Tandem Repeats

Peer reviewe

Isotope geochemistry of Mississippi Valley Type strataboundF-Ba-(Pb-Zn) ores of Hammam Zriba (Province of Zaghouan, NETunisia).

Peer reviewed journal article. Geology, 2017.Abstract available in PDF file

Pétrographie et altération de la matière organique du gisement de plomb-zinc-cuivre de Beddiane, district de Touissit- bou Beker, Maroc nord oriental

Reflectance measurements and organic petrography were used to study altered organic matter in the dolomitic Middle Jurassic Beddiane sequence hosting the Beddiane lead–zinc deposit. Organic matter occurs in the lower dolostone units of the formation where zinc sulfide mineralization prevails. The upper units, where lead sulfide mineralization is dominant, contain lesser amounts of organic matter. The organic matter in the Beddiane sequence consists of macerals, amorphous kerogen, and solid bitumen, inertinite and vitrinite are ubiquitous. The amount of exinite increases toward mineralized areas but the ratio exinite/kerogen remains constant. Two types of vitrinite are considered on the basis of their reflectance: Vt1 with low reflectance values (0.3–0.5%) and Vt2 with higher values (0.7–1.25%). The ratio Vt1/Vt2 increases and the reflectance values for Vt1 decrease toward the zinc-prevailing units, Organic matter associated with the mineralization exhibits features such as oxidation halos and desiccation cracks, together with a low-fluorescent exinite. The association of the kerogen content, the trend in reflectance values, and the alteration features of the Mississippi Valley-type Beddiane deposit support the hypothesis that the regional flow of hot brines associated with the mineralization process was the cause of anomalous heating, that the occurrence of exinite maceral and its associated gas played a role in the ore deposition, and that the new chemical equilibrium reached by the zinc-dominant host rock after ore deposition is responsible for the suppressed reflectance values within and near the ore deposits. </jats:p