Chemical characterization of heavy minerals and stream sediment of Betare-Oya gold district Neoproterozoic Fold Belt, Eastern Cameroon: implications for gold mineralization

Abstract

Stream sediment geochemical survey was carried out in Boyo situated in the Betare-Oya gold district. The study was aim to determine the primary source of gold, mineralogy of heavy mineral concentrate, provenance, weathering conditions and tectonic setting. Samples were collected by panning and analyzed using inductively couple plasma mass spectrometry method. Heavy minerals present in concentrates include gold, zircon, magnetite. The gold grade ranges from 15–37 and could be overestimated due to the presence of nuggets. Gold grains vary in size from 0.125-1 mm and exhibit sub-angular and angular shape indicating they were proximal to the source. Sediments shown enrichment in Au (8440- >10000 ppb), Mn (250–350 ppm), Hg (40–560 ppm), Th (186- >200 ppm), Y (67.5–117 ppm), large ion lithophile elements, rare earth element (REE: 1684.9-2382.6 ppm) and depletion in Fe2O3 (1.08–2.25 wt.%), Nb (0.4–1.6 ppm), Mo (0.03–0.21 ppm), high field strength elements. REE patterns show LREE enrichment (LaN/SmN = 1.06–1.24) relative to HREE (GdN/YbN = 2.20–9.29) and negative Eu anomaly (Eu/Eu* = 0.24–0.31). Au may be linked to sulphide minerals and the sulphidation could be the dominant mechanism of gold ore deposition. The association Bi-Pb-Sb-Sn-Zn are interpreted as mineralization factor and Bi, Pb, Sb, Sn, Zn are regarded as pathfinders for Au. The sediments were sourced intermediate igneous provenance, the detrital fraction and the source of contamination resulted from granitic sources. Sediments were immature, undergone intense weathering, transported in a short distance and were deposited in a passive margin consistent with rift environments.