Mineralogical and Geochemical Characterization of Gold-Bearing Rocks in Mararaban Yauri, Northwestern Nigeria

Abstract

The Mararaban Yauri area within the Zuru Schist Belt of northwestern Nigeria hosts significant artisanal gold workings, yet the mineralogical characteristics, hydrothermal alteration patterns, and geochemical controls on gold mineralization remain poorly constrained. This study integrates petrographic analysis, X-ray diffraction (XRD), and X-ray fluorescence (XRF) geochemistry to characterize gold-bearing host rocks and evaluate the exploration significance of stream sediments. Thirteen rock samples and ten stream sediment samples were collected, from which ten representative rock specimens were analyzed by thin-section petrography and XRD, while ten host rocks and ten stream sediments were analyzed for major oxides and trace elements using XRF. Petrographic observations identified quartz, orthoclase, plagioclase, biotite, muscovite, chlorite, garnet, hornblende, and opaque minerals, with widespread sericitization, chloritization, silicification, and localized oxidation. XRD analysis confirmed quartz as the dominant mineral phase (39–69.2 wt.%), accompanied by orthoclase (6.0–30.4 wt.%), albite (0.2–21.0 wt.%), muscovite (0.1–34.0 wt.%), clinochlore (12.0–19.0 wt.%), goethite (0.06–6.2 wt.%), and minor anorthite (5.6–5.7 wt.%). Whole-rock geochemistry revealed SiO₂ contents ranging from 52.95 to 95.62 wt.% and K₂O contents from 0.15 to 10.88 wt.%, reflecting extensive silicification and sericitic alteration. Gold concentrations in host rocks varied from below detection to 126.24 ppm, with the highest values occurring in quartz veins and structurally controlled phyllite–gneiss contact zones. Stream sediment geochemistry identified pronounced gold anomalies of 216.12 ppm, 129.93 ppm, and 122.96 ppm at RSS2, RSS3, and RSS1, respectively, whereas northern drainage sediments contained only background concentrations (18.50–20.06 ppm) or no detectable gold. The integrated mineralogical and geochemical evidence indicates that gold mineralization is associated with hydrothermal fluids that migrated along NE–SW-trending shear zones and quartz veins during the Pan-African Orogeny, producing silicification, sericitization, chloritization, and subsequent supergene oxidation. The close spatial association between hydrothermal alteration, quartz veining, and elevated gold concentrations establishes reliable mineralogical and geochemical vectors for future exploration within the Mararaban Yauri area and comparable Precambrian orogenic gold systems of the Nigerian Basement Complex.