Geology and exploration of gold deposits in the Giro Region, Haut Uele province, Democratic Republic of Congo

Abstract

The Central African Meso- and Neoarchean Greenstone Belt extends ca. 3000 Km from Tanzania extends westward to the Democratic Republic of Congo (DRC), South Sudan, and into Central African Republic. This greenstone belt is highly prospective for gold. However, except Tanzania, the rest of this greenstone belt is still under-explored area due to the challenging jurisdiction. The Kibali gold deposit in DRC has 28-million-ounces of gold being the only well-studied world-class producing deposit in this belt. This study focuses on the Kebigada gold deposit in the Giro region, which is ca. 30 Km west of the Kibali gold deposit. In the Giro region, the prolonged magmatism in the Giro region commenced at ca. 2801 Ma, with peak activities at ca. 2646 Ma. It ceased at around 2196 Ma. A group of felsic to intermediate granitoid plutons with relatively high Sr/Y ratio was formed during the magmatism and intruded the volcano-sedimentary rocks in the region. A stage of dextral ductile shearing along the 30km-long NNW-trending Kebigada Structure Corridor (KSC) occurred between ca. 2583 Ma and ca. 2512 Ma and led to the pervasive NNW-trending foliation predominantly in the volcano-sedimentary rocks in the region. During this 70 million years period, the rock units were uplifted shortly after the ductile deformation and experienced another stage of sinistral brittle deformation along the KSC which opened up fissures sub-parallel to the foliations. The first phase of gold mineralization deposited along those fissures and controlled the major shape of the Kebigada deposit. A geochemically- distinct phase of intermediate doleritic intrusions with low Sr/Y ratios emplaced at ca. 2512 Ma cutting across the foliation and the first phase of gold mineralization. This magmatism ceased at around 2497 Ma. Shortly after the cessation of this intermediate magmatism, the Kebigada deposit and the whole Giro region experienced another phase of sinistral brittle deformation which leading to the formation of a number of vein-type high-grade gold deposits, including Douze Match, Mangote, Adoku, Congo Ya Sika, Peteku, and a set of late stage veins within the Kebigada deposits, in the Giro region. Geophysics, soil sampling and lithostructural are very effective tools in pinpointing the prospective areas for potential gold deposit(s) in the Giro region. These exploration tools narrowed down the exploration targets to the Kebigada deposit. With extensive drilling at this deposit, a minimum of 4-million-ounces of gold have been estimated. Following the same exploration strategies, another Kebigada-type gold deposit has been newly discovered just 10 Km to the south of the Kebigada deposit. The exploration techniques designed in this study should be applicable for further exploration in the northeast part of the Congo Craton.