Gold-bearing quartz veins and associated rocks in the Wawa area, western Nigeria: Insights to their nature from field investigation, petrographic study, and geochemical analysis

Abstract

This study focused on the Wawa area, a southern extension of the Zuru Schist Belt (ZSB) in Northwestern Nigeria. The ZSB is one of western Nigeria's broadest and least studied schist belts. Information about its full extent, petrological, and geochemical characteristics still needs to be improved. Preliminary field investigations have shown that the Wawa study area possibly hosts orogenic gold deposits. This study carried out field investigation, petrological study, and geochemical analysis to understand and characterize the tectonic setting and possible origin of gold mineralization in the area. In total, 40 rock samples were studied under the microscope and 72 samples were subjected to geochemical analysis, including X-ray fluorescence (for major and trace elements) and X-ray diffraction analyses. The field investigation revealed that the rocks in the area are mainly gneiss, migmatite, amphibolitic rocks, phyllites, granitoids, and intrusive rocks such as quartz veins and pegmatite veins. Gold mineralization is confined to the quartz veins in amphibolitic rocks, and micro veins of pyrite and chalcopyrite are apparent in the amphibolitic rocks as well. The petrological and mineralogical studies showed that quartz is dominant in the samples from the Wawa study area, together with feldspars, mica, and other accessory minerals. The XRF data showed that the rocks underlying the Wawa study area are highly enriched in silica; meanwhile, several trace elements exist in anomalous concentrations compared to the corresponding average elemental values in the upper continental crust and based on several other reports from western Nigeria. The underlying rocks in the study area are mostly peraluminous with few plotting as peralkaline. Gneisses in the area are orthogneisses. The amphibolitic rocks in the area show both tholeiitic and calc–alkaline affinity. The K2O/Al2O3 vs Na2O/Al2O3 discrimination plot suggested that gold-bearing fluids in the area are likely from igneous and sedimentary sources. Despite the new data/information contributed by this study, further geochemical studies within the ZSB are required to fully understand the evolution and origin of gold mineralization in the area.