Geology and Geochemical Exploration for Gold at Qeissan County, Blue Nile State, S-E Sudan

A Study of the geology and geochemical evolution of the basement rocks of the Blue Nile area shows that they can be placed into five tectonic terrains; amphibolite inclusions unconformably overlain by heterogeneous and more lithologically varied super crustal assemblage of intercalated Para-gneisses and calc silicate rocks all of which have been largely metamorphosed in the amphibolites facies, all of these rocks have been cut by several intrusive phases. The present work provides a detailed account of the geology of the Qeissan area, rocks and the intrusions cutting them, their stratigraphy, structure, petrography and geochemistry are discussed. High-grade gneisses and low grade volcano-sedimentary rocks underlain the Qeissan area. They have been folded and faulted extensively. Orogenic plutons and an orogenic ring complex have intruded these successions. A mylonitic quartz-feldthpathic zone of 3 to 6 kilometers wide is trending northeast to southwest hosting the auriferous quartz veins. An oriented study (grid soil sampling, quartz veins and their wall rock alteration zone sampling) has been carried out to determine the anomalous area. All samples, (soil, rock & alteration zone) are prepared, analyzed and the results are interpreted using different software’s. The soil samples shows a rather low gold grades comparing with those of quartz veins. Most of the gold is found in quartz veins and their wall-rock alteration zones. The auriferous veins are grey to milky in colour, about 1 ? 3 m wide and 20 ? 300 m long; often pinching and swelling up to 1 ? 4 km along their strikes.