The scanning microprobe facility of the 3 MV Tandetron accelerator at King Fahd University of Petroleum and Minerals (KFUPM) has been applied extensively in various fields, including geology. This paper reviews a number of geological investigations carried out on samples of gold-bearing rocks, phosphorite ores and volcanic sediments. Elemental composition and distribution maps across single mineral grains, fluid inclusions, grain boundaries and matrices were measured. The microscopic data obtained are discussed to understand fundamental geological processes and ore genesis, and the provenance of economically important trace minerals contained in these samples.