Field Characteristics of Quartz Vein-Type Gold Deposits in Part of Kushaka Schist Belt, North Central Nigeria

Abstract

Gold deposits within the Kushaka schist belt of North-Central Nigeria are hosted within the metasedimentary basement rocks known as the schists. Those metasediments have been largely intruded by granitic plutons of Pan-African origin. Hydrothermal processes are believed to be largely responsible for the gold mineralization because the presence of lineament structures that extending from the granite outcrops and terminating in the schist. More so, faults, splayed veins, foliations and fractures hosted within the metasedimentary host rocks provided the needed pathway for fluid movement. The aeromagnetic data obtained from the Nigerian Geological Survey Agency (NGSA) on Minna sheet 164 as part of the Nigerian-wide geological survey data carried out in 2007 was used alongside the Oasis Montaj and ArcGIS software. The aeromagnetic data was obtained using a proton procession magnetometer with a resolution of 0.01nT. The magnetic data was important for structural mapping and the delineation of the magnetic anomaly. One of the magnetic lineaments was found to be one of the veins being currently worked on for gold. A total of 18 overburden soil samples were panned for gold along 10 pits at a weight of 2.5kg each. A positive correlation was found between vein splays and the presence of gold in the overburden soil. Two classes of quartz veins were identified from the study. They are the foliated (mineralized) and the un-foliated or massive quartz vein. The quartz vein that have no structural elements were observed to be barren and un-mineralized. The pattern of gold mineralization was found in the areas that are fractured, vug filling types, vein splays, wall rock alteration zones and dissemination in the overburden soil. The geochemical analysis of the soil concentrates, wall rock alteration and quartz veins are subjects to further research that are currently ongoing.