Structural Control on the Dikulushi Cu-Ag Deposit, Katanga, Democratic Republic of Congo

Abstract

The Dikulushi Cu-Ag deposit is located in the Kundelungu Plateau region in the southeast Katanga province of the Democratic Republic of Congo. The Kundelungu Plateau is a triangular-shaped area to the north of the Lufilian arc, which contains part of the Central African copperbelt, the largest known sediment-hosted copper province in the world. The Lufilian arc and the Kundelungu Plateau comprise Neoproterozoic sedimentary rocks of the Katanga Supergroup that attain an overall thickness of more than 7,000 m. The Lufilian orogeny imposed a northeast-directed shortening on the Kundelungu Plateau region, forming several gentle, northwest-oriented anticlines above subparallel detachment surfaces at depth. A north-northwest–oriented thrust is exposed in the western part of the Dikulushi mine, marked by ductile deformed shale that was transported upward and is in faulted contact with an overlying dolomite-sandstone sequence. This upward emplacement of the shale caused brecciation and the local development of kink folds in the dolomite-sandstone sequence. The brecciated layers in the west and nonbrecciated sandstone layers in the central part of the mine are crosscut by several east-west– and northeast-oriented faults. This complex set of faults produced a damage zone that was a favorable site for the migration of mineralizing fluids. The faults and brecciated layers contain Cu-Pb-Zn-Fe mineralization consisting of chalcopyrite, bornite, and chalcocite, with minor pyrite, arsenopyrite, sphalerite, and galena, with dolomite, calcite, and quartz as gangue minerals. The northeast-oriented fault direction was reactivated several times, with dextral strike- and oblique-slip fault movement. These fault zones were sites of remobilization and enrichment of the previously deposited Cu-Pb-Zn-Fe mineralization. The remobilized sulfides consist of Ag-rich chalcocite, with barite, calcite, and quartz as gangue minerals. The study has shown that the deposit of Dikulushi is structurally controlled by a crosscutting set of east-west– and northeast-oriented faults. Similar structural settings in the mine and in the Dikulushi region represent important future exploration targets.