Study of integrated geochemical techniques in the exploration for gold in North Mara mines, Tanzania

Characterization of certain alteration types, pathfinder elements and their distribution in and around gold mineralization can significantly aid delineation of exploration targets and reduce exploration costs. This study presents integrated use of multielement geochemical and mineral analysis in gold exploration with in North Mara Mines (NMM) in northern Tanzania. The aim was to evaluate the suitability of alteration mineral assemblages and composition as an effective exploration tool for fingerprinting hydrothermal systems responsible for the formation of major gold deposits within the North Mara mines. Mineralogical fingerprints were established using a combination of Short Wavelength Infra-Red (SWIR) spectrometry, X-Ray Diffraction (XRD) and micro petrography, whereas multielement analysis was done through four acid digest combined with Induced Coupled Plasma – Mass Spectrometry (ICP-MS) and Induced Coupled Plasma- Atomic Emission Spectrometry (ICP-AES). SWIR showed variation in chlorite and sericite chemistry and variation in Seri cite crystallinity which reflects pH changes and thermal gradient associated with gold mineralization in the NMM. XRD has established mineral phases from unaltered and altered samples in which mineralogical relationships were revealed by micro petrography. Multielement geochemical data revealed alkali and pathfinder elements (As, Sb, W, Mo, Bi and Ag) mobility with extension of pathfinder signatures beyond a distance of 600m width around the mineralization using an optimal sampling interval of 500 by 500m. The study demonstrates that a combination of pathfinder signatures, white mica crystallinity and composition can be used successfully to generate gold mineralization targets in the North Mara Mines and possibly in similar areas of Archean greenstone belts.