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Kibali Project (Kilo, Moto) - Karagba-Chaffeur-Durba (KCD), Mengu-Hill, Pakaka, Kombokolo, Rhino |
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Dem. Rep. Congo |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Kibali gold project, previously the Kilo and Moto mining centres, includes the Karagba-Chaffeur-Durba (KCD) deposit complex and the satellite Sessenge, Pakaka, Pamao, Gorumbwa, Kibali, Mengu Hill, Mengu Village, Megi, Marakeke, Kombokolo, Sessenge and Ndala deposits. The project is located within the Kibali Granite-Greenstone Belt, in the northeastern part of the Democratic Republic of Congo (DRC), ~560 km NE of the city of Kisangani and 150 km west of the Ugandan border town of Arua, near the international borders with Uganda and Sudan. It is 1800 km from the Kenyan port of Mombassa and 1800 km NE of Kinshasa.
Australian prospectors Hannan and O'Brien are attributed with the discovery of gold in the NE of the Democratic Republic of Congo in 1903. Subsequently historic production from the Kilo and Moto mine areas between 1906 and 2009 is estimated to have been ~340 t Au, half of which was derived from alluvial workings. From 1926, the Belgian Government established the Société des Mines d'Or de Kilo-Moto (SOKIMO) to conduct mining operations. The bulk of mining in the district surrounding the Kibali Project area was undertaken during the 1950s. Gorumbwa, Agbarabo and Durba deposits are believed to have produced more than 60% of the over 100 t of recorded gold production from the Moto area. Following independence in 1960, gold production declined sharply as mining was predominantly by artisanal miners and small-scale alluvial operations. SOKIMO became Offices des Mines d'Or de Kilo-Moto (OKIMO) in 1966 and became the main operator in the Project area. Sporadic underground mining occurred in the Project area after 1960, although most appears to have been removing remnants and only negligible gold were produced. Production records are not available during the 1980s and 1990s due to civil unrest.
The Karagba-Chaffeur-Durba deposit was originally discovered by a Barrick and AngloGold Ashanti by a joint venture in 1998. Both partners withdrew from the Project in 1998 due to local unrest and civil war. Moto Goldmines Limited (Moto) acquired a 70% share of Kibali Goldmines in 2004 and completed a pre-feasibility study in 2006, a Feasibility Study in December 2007, and an Optimised Feasibility Study in March 2009. In July 2009, Randgold and AngloGold Ashanti entered into a 50/50 JV and acquired Moto and their 70% equity in the Project. In 2009, the joint venture obtained an further 20% interest in Kibali Goldmines from SOKIMO, which retained a 10% interest on belhalf of the DRC government.
A subsequent feasibility study update doubled the declared Ore Reserve to over 31 t gold, and construction was approved in 2012. An open pit operation commenced mining Karagba-Chaffeur-Durba in July 2012, primarily exploiting and processing oxide ore, and the first gold was poured September 2013.
Construction of an underground mine at Karagba-Chaffeur-Durba, including a vertical shaft and twin declines, a sulphide processing circuit in addition to the associated Project infrastructure to support mining of other satellite open pit operations including Mengu-Hill, Pakaka, Kombokolo and Rhino. The sulphide circuit was commissioned in early in 2014 and production has steadily ramped-up since then. (Quick et al., 2018).
The deposits are hosted by late Neoarchaean (3000 to 2500 Ma) greenstones of the Upper Zaire/Congo Massif, comprising the Kibalian (Upper and Lower) volcano-sedimentary rocks and ironstone-chert sequences that have been metamorphosed to green schist facies. The stratigraphy consists of a volcano-sedimentary sequence comprising fine-grained sedimentary rocks, several varieties of pyroclastic rocks, basaltic flows, mafic intermediate intrusions (dykes and sills) and intermediate to felsic intrusive rocks (stocks, dykes and sills). The metamorphosed lithologies comprise mafic to intermediate greenstones, quartzites and ironstones at Moto and sericite, chlorite, talc and amphibole schists at Kilo. The sequence is variably altered from slight (texture preserved) to intense (texture obliterated) such that in some cases the protolith is unrecognisable. An important part of the sequence is the 'ironstone-chert', a sequence of magnetite-rich fine-grained horizons and 'ferruginous chert' with occasional jasperoid and specular hematite horizons, that is sporadically developed and forms prominent hills and ridges over an extensive area capping hills throughout the goldfield.
The host rocks overlie an older granitoid basement and are cut by Neoarchaean granitoids. It is cut by regional-scale north, east, northeast and northwest trending faults and is bounded to the north by the Mesoarchaean West Nile granite-gneiss complex and cut to the south by the Upper Zaire granitic complex. These rocks have been mylonitised in the orebody area with mineralisation present as impregnations (particularly within mylonites and cataclasites) and shear controlled veining.
The mineralisation is structurally controlled with a linear distribution of gold occurrences, with a regular periodicity of emplacement of mineralised lenses. The largest mineralised zones of mineralisation are aligned along NE trends and are ovoid-shaped with long axes that extend down plunge for considerable distances. The
orientation of the long axes of mineralisation approximates the orientation of F2 fold axes, the orientation of the intersection of S1 and S2, as well as the orientation of stretching defined by stretched varioles and rodded lozenges. The dynamic interaction of D1 and D2 has had a direct influence on the location and shape of the mineralized bodies. The destructive alteration-mineralisation event strongly overprinted or destroyed the early structural fabrics (S1 and S2) textures, indicating that main-stage gold mineralisation was synchronous with or post dates both D1 and D2. The gold associated breccias appear to have utilized NE-trending D2 structures.
A stratigraphic control following primary porosity/permeability features is inferred where the mineralisation is sub-parallel to bedding contacts. Iron-rich units in the stratigraphy e.g., ironstone, ferruginous chert, Fe-tholeiitic basalt and pervasive early ankerite alteration, enhanced the potential for deposition of gold. Main-stage mineralising fluids appear to have ponded or restricted in their flow as aquitard control by both the ironstone-chert unit and the 'upper basalt unit'.
The development of multiple and repeated breccias are an important feature of the higher grade mineralised intervals. Early breccias are characterised by an amorphous silica matrix, and are generally barren of gold. Locally, the silica matrix is accompanied by albite and ankerite-siderite ± sulphides and may carry anomalous gold values. Late breccias are sealed by a matrix of secondary chlorite of probable hydrothermal in origin, and can carry very high gold grades with coarse gold visible in hand specimen.
The numerous generations of breccias suggests that brecciation is important as ground preparation by hydraulic fracturing proceeding and/or accompanying mineralisation may mark periods of fluid over-pressuring and seismic pump-and-seal rupturing of the rock column below the various aquitards. Some of the early breccias are overprinted by the S1 foliation (as well as early quartz-feldspar and silica veins) while some of the chlorite-filled breccias appear to be later than S1, suggesting an evolution of breccia development with time (geological information summarised from Cube Consulting 2007 and 2009 report to Moto Goldmines Ltd)..
As of January 2009, the Moto project is quoted (Moto Goldmines Ltd website) as containing JORC compliant Mineral Resource of some 700 tonnes (22.5 Moz) of gold in 12 deposits, Pakaka, Gorumbwa, Kibali, Mengu Hill, Mengu Village, KCD (including Sessenge Deep), Megi, Marakeke, Kombokolo, Sessenge, Ndalaand Pamao. The largest, KCD, contains 492 t Au.
The deposits are grouped as follows:
Kibali - Sessenge - KCD - Cheuffer - Karagba Trend - which comprises a 4.5 km mineralised corridor which hosts the Kibali deposit towards its southwestern extremity, extending northeast, passing through the Sessenge, historical producing Durba Mine; the Chauffeur and Karagba deposits. These occur as a series of stacked northeast plunging mineralised lodes which have a strong down-plunge continuity.
Pakaka and Pamao Trend - the mineralisation at Pakaka dips at 15 to 25° and plunges to the northeast as a sheetlike lode averaging 10 to 40 m in thickness. It starts at the surface and has been intersected in drilling at vertical depths of more than 270 m which is 900 m down plunge, yet to be closed off. The Pamao Deposit lies 500 m west of Pakaka, and occurs as a 15 to 25° northeasterly dipping, 15 to 25 m thick zone of mineralisation over a strike length of 500 m and down dip extent of up to 350 m, a vertical depth of less than 150 m.
Gorumbwa - which was partially mined from 1954 until 1993 to a vertical depth of about 380 m, producing over 40 tonnes of gold at a reported recovered grade of more than 15 g/t Au. It consists of a series of elongated stacked lodes within a 100 to 180 m wide zone which is approximately 50 m thick and can be traced down plunge for 780 m to approximately 400 m vertical depth where it remains open both along strike and at depth.
Megi - Mengu Trend - extends for 4 km in a northwest direction from the Megi in the SE, to the Mengu Hill deposit. This trend includes the deposits at Mengu Hill, Mengu Village, Marakeke and Megi. The Megi deposit also dips at 15 to 25° NE over a strike length of 500 m and down dip for up to 250 m, to vertical depth of <90 m, with mineralisation consisting of an upper and a lower zone, the latter attaining a thicknesses of up to 36 m, averaging 15 to 20 m. The upper zone is generally thinner, averaging 5 to 10m. The Marakeke deposit starts 400 m west NW of the Megi Prospect and comprises a shallow (15 to 25°) northeast dipping zone of mineralisation extending over a strike length of 400 m and down dip for 150 m, to a vertical depth of less than 60 m. The Mengu Village deposit commences a further 800 m to the northwest of the Marakeke. Drilling at Mengu Hill which is located 450 m south of the Mengu Village deposit has outlined mineralisation similar in style to the Chauffeur - Karagba deposits and consisting of a 30° NNE plunging mineralised shoot on the northern dip slope of Mengu Hill.
Ndala - is located 1.9 km east of Pakaka and covers an area of 180x130 m but is open in all directions.
Kombokolo - lies approximately 800 m to the southeast of the old Agbarabo mine and is marked by artisanal workings above one of the main exploration drives established by Belgian exploration in the early 1960s.
The resource in January 2009 (Moto Goldmines Ltd website) comprises:
Indicated mineral resource - 112.4 Mt @ 3.1 g/t Au
Inferred mineral resource - 107.2 Mt @ 3.3 g/t Au.
The most recent source geological information used to prepare this decription was dated: 2016.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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