Geochemistry and Petrology of Metasediments Associated with Gold Mineralization in Imonga Area, Eastern DR Congo

Abstract

The Imonga sector is located in the Eastern of DR Congo, precisely within the Maniema province located in the Central African Karagwe Ankole belt, which forms together with the Kibara belt a Mesoproterozoic geological structure. This study gives fresh information on the origin of the metasediments in this zone, their geochemical and petrographic characteristics, and the genetic model of the gold mineralization that they contain. Field observations, as well as petrographic and geochemical studies reveal that the metasediments consist of sericitoschists and quartzites. Petrographic work revealed varying proportions of sericite and quartz with subordinate iron-oxide minerals. Geochemically, most of the analyzed metasediments displayed higher SiO 2 contents and enriched in Fe 2 O 3 . They belong to the groups of shales and sand (sometimes rich in iron), litharenite and grauwakes derived from quartzose sedimentary and mafic igneous provenance. Their protholites are intermediate altered (70 < CIA < 90) andesitic, granite and granodioritic rocks emplaced in a geotectonic active continental margin. Gold mineralization in the Imonga sector occur in veins. Gold mineralization is controlled by veins which occur as micro veins with small thickness. The mineralization consists of specific grains and nanoparticles pyrite associated with gold, hematite and goethite. The hydrothermal alteration accompanying this mineralization consists of silica, goethite and sericite-carbonate. Keywords: Metasediment, sericitoschist, quartzite, sericite, goethite, vein, Gold, Imonga, Eastern DR Congo DOI: 10.7176/JEES/13-2-04 Publication date: March 31 st 2023