Lithologic, Petrographic and Geochemical Search for By­passed Gold Mineralization within Mutumdaya Gold Field in Minna outskirts, North-Central Nigeria

Abstract

By wildcat pitting, local artisanal miners established a lode gold mine within Mutumdaya in the Northern Nigerian Massif. The mine is now abandoned after a few years of mining. Wildcat pitting lacks the benefits of geoscientific investigations, and the mines so found remain unassessed discoveries. Some untapped gold mineralization does remain around such mines when abandoned. The mineralization constitutes by-passed gold mineralization. Lode gold mining will continue in Mutumdaya if by-passed gold mineralization is found within vicinity of the abandoned mine. This study identified by-passed gold mineralization prospects in immediate vicinity of the abandoned mine. This was achieved by searching for rocks that share similar lithologic, petrographic and geochemical attributes as rocks within the abandoned mine site. It involved surface lithologic mapping, thin section petrographic analysis, and elemental gold concentration analysis in rock samples, using X-Ray Fluorescence Spectrophotometer. The rock bodies were found to be kyanite schist, amphibole schist, quartz schist, and quartzite intruded by syntectonic biotite granite bodies. The quartz schist attained greenschist metamorphic grade, while kyanite schist and amphibole schist attained amphibolite facies metamorphic grade. The kyanite schist at the abandoned mine site contains 0.058 ppm gold concentration. This is 29 times average crustal gold abundance of 0.0000002 %. Outside the abandoned mine site, kyanite schist and amphibole schist contain 0.066 and 0.021 ppm gold concentration. They are respectively 33 and 11 times gold enriched. Gold was undetected in the quartz schist, quartzite and granite bodies. The kyanite schist outside the abandoned mine site is more enriched in elemental gold than the rock body that constitute gold ore within the mine. Apparently, rock bodies in the amphibolite metamorphic facies status constitute prospects for by-passed lode mineralization within the immediate vicinity of the abandoned gold mine. These prospects are at location 9°40 05 N, 6°4850 E, and location 9°39 05 N, 6°4840 E. Abandoned artisanal gold mines in the Northern Nigerian Massif and in other developing economies should be searched for by-pass lode gold mineralization, using integrated geoscientific methods.