Reconnaissance Exploration for Gold in the Misaki Area within the Iramba-Sekenke Greenstone Belt, Central Tanzania

Abstract

Combinations of geological, geophysical and geochemical techniques have been used to explorefor gold deposits at Misaki within the Iramba-Sekenke Greenstone Belt in Singida region. TheMisaki area is occupied by different rocks including homogeneous coarse-grained granitecontaining numerous xenoliths (> 5 vol. %), tonalite, K-rich granite, pegmatite and dolerite dykes.All granitic rocks have been intruded by dolerite dykes, cut by epidote veins and are foundjuxtaposed to a tonalitic rock. Granitic rocks contain mainly anhedral to subhedral K-feldspar,plagioclase, quartz, biotite, hornblende, muscovite and opaque minerals, whereas tonalite containssimilar minerals with relatively large amounts of plagioclase and mafic minerals (> 10 wt. %;biotite, hornblende and opaque minerals) and no K-feldspar. The rocks are weakly foliated tomassive and poikilitic. K-feldspar is perthitic, whereas plagioclases have cores with rimovergrowths. Chlorite, epidote and sericite in the rock formed at the expense of primary mineralsunder greenschist facies conditions. Geophysical datasets managed to identify lineaments thatcrosscut different rocks at Misaki, from which three (3) major structural trends have beenrecognized, which are NE-SW, NW-SE and ESE-WNW. Results from radiometric data mappeddifferent lithological units by their different radiometric element contents (U, Th and K),distinguishing areas occupied by sediments or sedimentary rocks and those underlain by granitoidrocks. Soil geochemical survey have identified gold anomalies of up to 0.2 ppm Au that in partsshow strong affinity with Pb. Bismuth and arsenic were also found to be associated with Au in thesoil. Gold anomalies when overlaid with magnetic lineaments indicate an association of gold withNE-SW trending lineaments. Results of this work call for a follow-up detailed geological mappingthat would involve trenching and sampling of unweathered rocks, and documentation of geologicalstructures to uncover potential gold deposits of the Misaki area within the Iramba-SekenkeGreenstone Belt.