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The identification of trace element anomalies in soils has been proven to assist semi-mechanized small-scale gold operations. This study employs soil geochemistry combined with the microchemical signature of particulate gold from the Batouri goldfield to (1) vector possible gold-endowed lithologies introducing particulate gold into the overlying regolith, and (2) assess anthropogenic Hg used in purification of both primary and alluvial/eluvial gold by artisans. The soil geochemistry shows irregularly distributed anomalies of elevated Cu especially in the saprolite soil layer. Whereas in the lateritic soil layer, a Au-Ag-Hg metal association is reported for the first time in this gold district and could be linked to anthropogenic Hg used in gold recovery. Particulate gold recovered from the soil varies in shape from euhedral and irregular to sub-rounded, indicating a proximal lode source. The gold grains range in size from nano-particles to >300 µm and are Au-Ag alloys. The gold particles reveal inclusions such as quartz, silicate, zircon and ilmenite suggesting that the grains were dislodged from quartz veins within the granitic basement. Systematic variation in the microchemical signature of the gold grains is suggestive of spatial and temporal evolution of the mineralizing fluid. These results are consistent with investigations from similar geologic settings worldwide and validate the combined utility of gold fingerprinting and pathfinder elements in soil to examine deposit genesis in other gold districts globally. [ABSTRACT FROM AUTHOR]

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The Sanaga iron ore prospect within the Palaeoproterozoic Nyong Series in Cameroon is a magnetite‐dominated iron ore deposit hosted within granodioritic gneisses with an estimated resource of 82.9 Mt @ 32.1% Fe. The main ore mineral being magnetite, provides an opportunity to study the magnetite texture and iron‐oxygen isotope composition of the mineralization, which has heretofore not been reported. These offer insights into the nature and condition of formation of the mineralization thereby paving the way for better understanding the genesis and evolution of the mineralization as well as classifying it. The mineralization is characterized by Type I and Type II magnetite varieties based on their textural features. Type I magnetite is the dominant magnetite and is characterized by ilmenite oxy‐exsolution features with triple junction contacts, while Type II magnetite lacks these features. The presence of ilmenite oxy‐exsolution features in the Type I magnetite indicates a primary magmatic formation of the magnetite followed by re‐equilibration of primary Ti‐rich magnetite in the presence of a high‐temperature fluid. Oxygen isotope (δ18O) values for the magnetite range from +2.89% to 9.30‰ indicating precipitation from evolved ore‐forming fluids through reaction with country rocks. The iron isotope (δ56Fe) of the magnetite shows little variation, with positive values ranging from +0.49–0.66‰. These values plot within the magmatic and magmatic‐hydrothermal magnetite fields when compared to the published global range of δ56Fe values for different deposit types. A similar result is obtained by plotting the coupled Fe–O isotope pair, further buttressing the magmatic‐hydrothermal origin of the mineralization. Based on these data, the Sanaga iron mineralization is best explained as a magmatic‐hydrothermal deposit. [ABSTRACT FROM AUTHOR]

Tin mineralization at Mayo-Darlé in the Cameroon Volcanic Line is associated with highly evolved anorogenic ferroan granite magmatism with a pervasive hydrothermal overprint. Mineralization occurs as cassiterite-quartz-muscovite stockwork and disseminated in quartz-mica and quartz-topaz greisen in low-Ca alkali feldspar granite with a composition near the 1 kbar haplogranitic thermal minimum. The trace element composition of zircon indicates elevated temperature (880 ± 55 °C) and very low oxidation state below the quartz-fayalite-magnetite buffer. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) identifies a partly disturbed U-Pb system for igneous zircon (U and Th contents >1000 ppm) but defines Tera-Wasserburg concordia ages and common-lead-corrected weighted 206Pb/238U ages of about 54 Ma, similar to a previous 87Rb/86Sr vs 87Sr/86Sr regression with a date of 56.1 ± 1.7 Ma (MSWD = 58; n = 9) and an initial 87Sr/86Sr ratio of 0.7085 ± 0.0035 (2 s). Hydrothermal cassiterite gives a pooled LA-ICPMS Tera-Wasserburg concordia age of 56.7 ± 0.6 Ma on two samples (each about 20 points, MSWD = 0.54 and 1.3). These new age data define a period of early Cenozoic intraplate calc-alkalic felsic magmatism as a precursor to abundant Oligocene to Recent alkali basalt volcanism along the Cameroon Volcanic Line. Geochemical and Sr–Nd–Hf isotopic data suggest that the granitic rocks from Mayo Darlé were largely derived by partial melting of Mesoproterozoic basement and modified by strong differentiation, all likely powered by heat (and possibly fluids) from the mantle. The Tertiary age of the rare-metal magmatism sets this system apart from the widespread Late Neoproterozoic to Early Paleozoic rare-metal pegmatites and granites in the Pan-African collisional belts of Africa, and also from the anorogenic Mesozoic ring complexes in Central Nigeria. [Display omitted] • Tin mineralization is associated with anorogenic alkali feldspar granite magmatism. • Igneous zircons yield a partially disturbed U-Pb age of 54 Ma. • Zircon trace elements indicate very low oxidation state. • Hydrothermal cassiterite gives a pooled U-Pb concordia age of 56.7 ± 0.6 Ma. • Cassiterite proves to be suitable for U-Pb dating of highly evolved granite systems. [ABSTRACT FROM AUTHOR]