The main Kibali deposit consists of the combination of Karagba, Chauffeur and Durba (KCD) deposit. Currently only the KCD deposit hosts an underground Ore Reserve and this constitutes 74% of the total KCD Ore Reserve.

Gold mineralisation of the Kibali district are classified as Archaean orogenic gold deposits. At Kibali the gold deposits are largely hosted in siliciclastic rocks, banded iron formations, and chert that were metamorphosed under greenschist facies conditions. Ore-forming H2O-CO2-rich fluids migrated along a linked network of gently northeast-dipping shears and northeast to NNE- plunging fold axes that is commonly referred to as the KZ Trend. On-going deformation during hydrothermal activity resulted in development of lodes in a variety of related structural settings within the KZ Trend. The source(s) of metal and fluids which formed the deposits remain unknown, but metamorphic devolatilisation reactions within the supracrustal rocks of the Moto Greenstone Belt and/or deeper fluid and metal sources may have contributed.

Gold deposits of the Kibali district are associated with haloes of quartz, ankerite, sericite, ± albite (ACSA-A) alteration that extend for 10s to 100s of metres into the adjacent rocks. This widespread ACSA-A alteration assemblage is superimposed on older greenschist facies metamorphic assemblages. Locally in the vicinity of the main mineralised zones ACSA-A alteration is overprinted by ankeritesiderite, pyrite alteration (ACSA-B) that hosts the ore. Gold is directly associated with the ACSA-B alteration assemblage. In smaller peripheral deposits a late chlorite, carbonate, pyrite assemblage is associated with the ore rather than the ACSA-B assemblage, implying a district-wide zonation of mineral assemblages along and across the mineralised KZ Trend. Zones of auriferous ACSA-B alteration are commonly developed along the margins of banded iron formations, or contacts between chert, carbonaceous phyllite, and banded iron formations. Mineralised rocks in the Kibali district typically lack significant infill quartz-rich veins, unlike many other orogenic gold deposits. Gold is instead associated with pyrite in zones of alteration that replaced the earlier mineralogy of the host rocks. Local remobilisation and upgrading of ACSA-B related ore occurred adjacent to the margins of some post-ore crosscutting chlorite, carbonate, ± pyrite, ± magnetite-altered diorite dikes.

The location of the individual lodes within the KCD deposit are intimately controlled by the position, shape, and orientation of a series of gently northeast-plunging tight to isoclinal folds. The ACSA-A alteration developed during the formation of these folds, and the sericite foliation which is an integral part of the ACSA-A assemblage formed parallel to their axial planes. Zones of later auriferous ACSA-B alteration developed along the axes, limbs, and more rarely the axial planes of these folds, locally wrapping around the hinges of the folds to form elongate northeast-plunging concave-shaped rods. ACSA-B alteration is also commonly focused along the margins of more extensive banded iron formations, indicating a stratigraphic as well as structural control on the distribution of ore, both within KCD, and other parts of the wider KZ Trend. Shear zones that were active during folding are a third key structural control on the location of ore within KCD and the wider KZ Trend. At KCD a folded carbonaceous shear in the core of the deposit juxtaposes stratigraphically distinct blocks. The 3,000 lodes above this shear are hosted by locally ferruginous cherts, carbonaceous argillites, and minor greywacke, whereas the 5,000 and 9,000 lodes below are hosted by siliciclastic rocks and banded iron formation. Fold shapes and wavelength differ between the two blocks reflecting their different rheologies during folding, and this is reflected in the scale, shape, and continuity of lodes in each block. At Pakaka and Kalimva chlorite, carbonate, pyrrhotite, ± pyrite-altered shear zones rather than folds are the principal controls on gold distribution.

The mine comprises both open pit and underground mining.

Open pit mining takes place in a number of satellite pits over approximately 14 km. Some of the pits are relatively shallow and have a short mine life of two years or less such as Pamao and Sessenge, whilst others are deeper and have a longer life of more than two years, such as Pakaka and Gorumbwa. There are six main open pit deposits, KCD, Pakaka, Pamao, Kombokolo, Sessenge, and Mengu Hill, located within an approximately 7 km radius.

Open pit mining is conducted by contractor Kibali Mining Services (KMS), a local subsidiary of DTP Terrassement, using either free-dig or conventional drill, blast, load, and haul methods.

The mining equipment is jointly owned by a subsidiary of the owner and the contractor’s parent.

Development of the underground mine commenced in 2013. Stoping within the upper levels commenced in 2015, utilising the twin surface decline system for trucking of ore to surface. A vertical production shaft (751 m deep) is scheduled for full commissioning during 2018 following commissioning of the materials handling system completed at the end of 2017.

Longitudinal and transverse longitudinal stoping methods with paste backfill were chosen as the preferred underground mining methods.

The Kibali KCD underground mine is designed to extract the Karagba, Chauffeur and Durba (KCD) deposit directly beneath the KCD open pit. A 50 m crown pillar separates the pit bottom from the top of the underground mine. The underground mine is a long hole stoping operation planned to produce at a rate of 3.6 M ore tonnes per year.

Ore from stopes is loaded (both by teleremote and conventional manual loaders) from the stopes into the eight ore passes via finger raises on the respective levels. This ore is then transferred by Autonomous load haul dumpers (LHDs) into two coarse ore bins and then into two primary crushers, followed by two fine ore bins and independent skip loadout conveyors near the shaft bottom.

The proposed mining methods are variants of long hole open stoping with cemented paste:
• Primary / Secondary long hole open stoping (primary 28% of Ore Reserve tonnes, secondary 40% of tonnes) is used in the wider zones, with 35 m interval heights where stopes are mined either as single lift or multiple (up to four) lifts, depending on stope geometry and the geotechnical stable span.
• Advancing face long hole open stoping (23% of Ore Reserve tonnes) is used in the deepest portion of the mine where the mineralisation has a shallower plunge (approximately. 20° to the NE), where stopes are mined with variable interval heights between 25 m and 35 m to optimise extraction.
• Longitudinal open stoping (9% of Ore Reserve tonnes) is used in narrow zones (< 15 m width) with variable interlevel heights between 20 m and 35 m.

Mining methods are reviewed periodically as further resource infill and grade control drilling changes the shape of the ore zones, however, there have been no significant changes to the mining methods.

The underground mining operations are currently operated by contractors (Byrnecut) and the contractor operation will continue until approximately mid to late 2018, when the changeover to The Kibali KCD underground mine has a scheduled production rate of 3.6 Mtpa for 10 years. The LOM predicts a long tail of declining production over a further nine years thereafter. The schedule is expected to be progressively optimised to extend the period of the 3.6 Mtpa production rate.

The Kibali gold processing plant comprises two largely independent processing circuits, the first one designed for oxide, transition and free milling ore sources and the second for sulphide refractory ore. However, both circuits are designed to be switched to process sulphide ore when the oxide, transition and free milling ore sources have been depleted.

The processing plant rated throughput is 3.6 Mtpa of soft oxide rock ore through the oxide circuit and 3.6 Mtpa of primary sulphide rock ore through a parallel sulphide circuit. Once the plant is sulphide only, the capacity is 7.2 Mtpa of sulphide ore. Kibali’s operational performance has demonstrated that the process plant is fully capable of its design capacity, and further modifications to the mills with an increased motor size coupled with a decreased inlet trunnion size has allowed for an even greater power draw and hence higher throughputs.

Once the oxide, transition and free-milling ore sources have been ........