Review of exploration
Our exploration programme aims to create value through the discovery of world-class gold deposits.
- Drum Mountain Project
- Nome, Alaska
- Gramalote JV
- Western Cordillera JV
- Rio Dulce
- Quebradona JV
- La Colosa
- Anaima Toche
- Falcão JV
- Graben JV
- Siguiri Blocks 1-4
- Kilo Project
- Lusahunga JV
- Mkurumu JV
- Afar JV
- Afar JV
- Akordat North
- Wadi Kareem
12 Saudi Arabia
13 Solomon Islands
- Western Province JV
- Tropicana JV
- Gawler JV
AngloGold Ashanti holds a total of 69,565km2 of greenfield tenements over which exploration activities are undertaken through joint ventures, strategic alliances or as wholly-owned ground holdings.
During 2012, exploration activities were conducted in 14 countries with over 364,994m of diamond, reverse circulation and aircore drilling completed, compared to 213,441m in 2011. Drilling programmes aimed to test new high-priority targets in Australia, Brazil, Tanzania, the DRC and the Solomon Islands, and continued to delineate existing discoveries in Guinea, Egypt and Colombia.
In the Americas, the principle area of focus has been to advance exploration on a number of key projects in Colombia, including an advanced-stage diamond drill campaign at the Nuevo Chaquiro target, Quebradona project (AngloGold Ashanti/ B2Gold joint venture). The Nuevo Chaquiro target is a newly identified porphyry-related, copper-gold mineralised system located within the Western Cordillera of Colombia.
In 2012, about 20,700m of diamond drilling has tested this porphyry copper and gold mineralised stockwork zone. Long intersections of copper mineralisation with gold credits indicate good continuity within the zone and it has been intersected at depths from about 400m to over 900m below surface. Drilling will continue in 2013 to delineate the limits of the zone and define the presence of a higher grade core.
In Brazil, a joint venture was signed with Graben Mineração to explore its tenement holding in the highly prospective Juruena Belt while generative work continued in Argentina and the United States.
In sub-Saharan Africa, drilling continued to delineate significant mineralisation at the Saraya and Kounkoun prospects, both located within 50km of the Siguiri mine in Guinea. At the Saraya prospect 9,230m was drilled to infill and define the extensions of the mineralised zone from which ore-grade mineralisation was intersected in several holes. The zone has now been delineated over 1,300m in strike and from surface to 200m in depth. At Kounkoun about 56,000m was drilled with numerous shallow oxide ore-grade gold intersections indicating further good potential. In the DRC and Tanzania, preliminary diamond drill testing of coincident gold-in-soil and geophysical anomalies was completed.
In the Middle East and North Africa, exploration is conducted through a regional strategic alliance with Dubai-based Thani Investments. The alliance has made significant progress in advancing its Hutite orogenic gold discovery in Egypt and continues to make further discoveries such as the Pandora epithermal system, in partnership with Stratex International, in Djibouti. Early stage exploration activities continue in both Ethiopia and Eritrea while project generation activities are ongoing in Saudi Arabia where a number of tenement applications have been made. In 2012, AngloGold Ashanti fully impaired the loan amounting to $37m which it had made to the joint venture during 2011 and 2012.
In the Solomon Islands, the joint venture with XDM Resources has been expanded to include additional projects within the prospective New Georgia Belt, consolidating the island chain. Exploration is now focused on the discovery of large porphyry and epithermal gold deposits. Generative exploration activities were completed at Kele, Mase, Tirua and Paraso while diamond drilling was also completed at Kele, Tirua and Mase.
In Western Australia, the Tropicana joint venture continues to systematically explore the highly prospective Tropicana Belt through auger surface geochemical sampling and follow-up aircore, reverse circulation and diamond drilling. At the wholly owned Viking project, immediately southwest of the Tropicana JV, aircore and diamond drilling at the Beaker prospect has intercepted potentially significant gold mineralisation. In South Australia, diamond drill testing of conceptual iron oxide coppergold (IOCG) targets was completed at the Coronation Bore prospect, in joint venture with Stellar Resources.
A total of 22 surface holes were drilled during the year, six at Moab Khotsong, three at Mponeng (WUDLs) and 12 shallower surface holes were completed to the west of Kopanang, while one is still currently being drilled.
At Moab Khotsong, borehole MGR8 continued advancing its long deflection to the north. It was stopped due to budgetary constraints in the last quarter, but the site was not rehabilitated as the hole will continue as soon as funding is available. The drilling of the long deflection to the south in MGR6 continued. MHH2 advanced to a depth of 2,880m and progress was delayed by a series of in-hole technical difficulties. Diamond drilling started at MCY6 and advanced the hole to 1,998m. A high speed drilling programme started to confirm the structure in the centre of the main Zaaiplaats block, borehole MMB6 progressed to 2,541m and borehole MMB7 advanced to 1,134m.
A new generation, high resolution 3-D seismic survey was completed over the Project Zaaiplaats Phase 3 area. Data processing and interpretation is currently underway.
Three holes are currently being drilled on the WUDLs Mining Rights extension of Mponeng Mine. These holes are all targeting the Ventersdorp Contact Reef. All the holes experienced significant loss of drill fluids and required multiple grouting operations. UD51 by year end had reached a depth of 3,582m in the Klipriviersberg lavas. UD59 advanced to 2,446m in the Klipriviersberg lavas and UD60 drilled to 1,556m.
The drilling of a series of shallow surface holes (500m – 1,400m) to the west of Kopanang continued during the year. A total of six holes targeting the Ventersdorp Contact Reef and six holes targeting the Vaal Reef were completed during the year.
At Cerro Vanguardia, the drilling programmes for Mineral Resource expansion and exploration continued during the year with solid additions to the Mineral Resource. Follow up drilling for vein extensions along strike and at depth was successfully able to expand mill ore as was exploration and Mineral Resource modelling to identify opportunities for material to be processed at the heap leach facility. Exploration activities and drilling were completed based on geophysical surveys and target identification studies conducted at the El Volcan project during the year.
In the Iron Quadrangle, the Mineral Resource development drilling programmes continued at the Cuiabá and Lamego mines with renewed emphasis on support to long-term planning and Mineral Resource definition. The surface drilling programmes at the Córrego do Sítio project continued to expand the oxide Mineral Resource, while underground drilling at Córrego do Sítio focused on developing the Sangue do Boi sulphide Mineral Resource for production. Exploration work beyond the production centers included follow up underground drilling at Raposos. Regional exploration programs were conducted at the Pari and Morro da Gloria projects.
At Serra Grande, the second year of fast track exploration programme was successfully completed with additional expansion of the Mineral Resource. The programme was focused on additions in the Pequizão, Mina Nova, Mina III and Structure NW/Cajueiro targets. Geophysical surveys and soil sampling campaigns continued to be useful methods for target identification in preparation for drilling programmes at the Cajueiro, Structure NW and Boa Vista (Votorantim Metais JV) regional targets.
Exploration in the Gramalote area was focused on infill drilling to support the update of the Mineral Resource estimation for the Gramalote Central deposit. Drilling programmes were also conducted for nearby satellite targets at Monjas West, Trinidad, and El Limon. As part of the prefeasibility study, additional infrastructure and geotechnical drill holes were completed to support highwall design and condemnation drilling for the proposed plant site, waste rock, and tailings storage facilities.
At La Colosa, the Mineral Resource development drilling program continued with four drills operating through most of the year. The geological model was updated during the year to support a significant Mineral Resource addition that came through expansion of the deposit to the northwest and at depth. Other drilling continued as support for site characterisation and infrastructure site selection studies.
The Mineral Resource development drilling programme continued during the year at CC&V. Work focused on infill drilling to improve the definition of material within the current mine designs that will feed the planned mill facility. Other drilling was directed toward identifying expansion opportunities for the current open pit operations through highwall cutbacks. Selective drilling was also conducted to test deeper targets below or adjacent to planned open pit designs that may provide additional mill feed material potential.
At Geita, Mineral Resource upgrade and extension drilling was completed at the Geita Hill, Nyankanga and Star & Comet operations. Limited pre-resource drilling programmes were undertaken to test exploration targets. The infill drilling campaigns aimed at increasing the confidence level of the Mineral Resource base and to allow for Mineral Resource to Ore Reserve conversion. A total of 440 holes for 85,221m were completed, with 67,738 samples submitted for gold assay.
As a result of this extensive drilling campaign, positive analytical results were received for holes drilled at Nyankanga Cut 7 OP, Geita Hill East and West, Star & Comet – Ridge 8 Gap, Ridge 8, Nyankanga Block 1 & 2, Kukuluma, Matandani and Area 3 West areas. However, poor analytical results were received for the Geita Hill Waste Dump sterilisation programme.
Drilling of down-dip extensions outside of the existing Nyankanga pit shell continue to support and extend underground potential at Geita.
Pit-scale structural mapping was completed at Nyankanga, Geita Hill and Star & Comet. This detailed mapping has provided valuable resolution to the understanding of the geological model over the respective areas. Induced polarisation (IP), gravity and electromagnetic geophysical surveys were also undertaken during the year and assisted with target generation.
At Siguiri, exploration activities focused on the Block 1 licence area with a total of 144,908m drilled during the year. Infill Mineral Resource drilling of 86,552m took place along the main northsouth trending Siguiri mineralised area as well as an aggressive reconnaissance drilling programme of 34,145m over soil anomalies and structural targets.
Significant drilling activities took place in the (from south to north) Sintroko-Sokunu, Tailings Facility, Silakoro, Kami- Kossise-Kozan, Sanu Tinti-Eureka-Kalamagna, Balato, and Kintinian areas. Fresh rock drilling centred on the hard rock mineralisation potential below the pits of Kami NE, Kozan South, Kalamagna Pit 1, Sanu Tinti and Bidini and confirms the continuation of the mineralised ore zones below the oxidefresh rock interface. In total, 8,824m were drilled for fresh rock exploration purposes.
The target generation programme in Block 1 continued to centre on IP surveys over selected soil geochemical and structural target areas. IP surveys were completed at Silakoro, Sintroko South and Komatiguiya. Gravity surveys were also completed over Silakoro and Sintroko South target areas. No surface geochemical soil sampling took place.
At Obuasi, a total of 12,169m was drilled, with 4,805m from underground exploration and 7,364m from surface exploration activities. Surface exploration focused on the Rusty Monkey target, with 16 holes completed for a total of 5,659m.
Underground exploration continued to focus on the BSVS project area below 50 Level, with drilling designed to upgrade the existing Mineral Resource and test the down dip extensions of quartz and sulphide mineralisation hosted within the carbonaceous and graphitic shear zones present in the area below Block 10 to -1390RL. Above 50 Level, drilling also commenced in Sansu 3 area during November to upgrade the Mineral Resource in Red Zone 9 area.
Field mapping and sampling to generate drill targets and enhance and refine geological understanding continued throughout the year.
A total of 13,227m drilling was completed at Iduapriem. The focus was on Mineral Resource conversion drilling to facilitate the on-going Iduapriem expansion study, specifically at Block 3W and Blocks 7 and 8. A sterilisation drilling programme of 3,084m was carried out at the proposed location of the Ajopa waste dump from August to October 2012.
The geological modelling of Blocks 1, 2, 3, 3W, 4 and 5 to investigate the potential underground extraction of mineralisation below the open pittable Mineral Resource has been completed.
At Mongbwalu, a total of 30,000m of brownfield exploration drilling was carried out. Drilling focused on infill Mineral Resource drilling within the main Adidi-Mongbwalu Mine area. Sterilisation drilling was undertaken over both the portal, plant and camp areas. Additionally, over 18,000m of greenfield drilling was completed in the year under review. Limited reconnaissance drilling was completed in the Adidi North and Tchangaboli areas.
Total diamond drilling at Kibali was 18,000m. At the KCD deposit, a data review identified an area at the down plunge termination of the 5000 lode stope designs that has potential for Mineral Resource conversion and extension. Results to date are encouraging and compare positively with the current interpolated block model values; however a potential loss was identified in the 3000 lode with some intersections lower than those predicted by the block model. The KCD deposit remains open down plunge and there are further opportunities for the conversion of Inferred Mineral Resource, most notably in the 9000 lode.
Within a 10km radius of the main Sessenge-KCD deposit, there are a number of satellite deposits which are considered to have significant upside, either having very limited drilling or drilling only to relatively shallow depths. Kombokolo, Gorumbwa, Pakaka, Agbarabo and Mengu Hill are priority targets which form part of the endowment development plan for near mine site targets.
At Gorumbwa, drilling results confirmed the current model and further defined the depletion of underground Mineral Resource by historic mining activities. The drilling has the potential to allow for the conversion of a significant proportion of the current Mineral Resource into Ore Reserve and suggests further open pit potential.
At Mengu Village and Mengu Hill, an 18-hole shallow pitting programme was designed and completed in November to test for the up-plunge continuation of mineralisation beyond available drill data. Results received to date have confirmed the presence of a significant mineralised system.
A total of 119,554m of reverse circulation (RC) and diamond drilling were completed at Sadiola and Yatela.
At Sadiola, 48,490m of RC drilling was concentrated at Tambali, FE Gap, S12, Sadiola NE and the sub-laterite targets of Mandakoto and Sekokoto. Diamond drilling of the deep sulphide targets below the Sadiola Sulphide Project was conducted. Further core drilling focused on sulphide exploration below FE 3 and 4 and Tambali pits and follow-up drilling for geology and structural interpretation at Tabakoto and S12. Sterilisation drilling of 9,854m was successfully conducted at Tambali and over the proposed TSF and SSP infrastructure.
The S12 target at Sadiola, west of the FE3 pits, was one of the most prospective areas drilled during the year. Good results have been returned from both oxide and shallow sulphide intersections, with further drilling planned. Follow up drilling at Mandakoto confirmed the extension of northeast-southwest mineralisation. At Tambali, drilling around the planned pit areas indicates the potential for extension of the current oxide Mineral Resource and sulphide potential at depth.
Exploration at Yatela consisted of 59,192m RC drilling at Yatela NE, KW18, Alamoutala, Yatela Diorite, Badji and Yiri. Diamond drilling totalled 2,608m. Approximately 11% of the RC drilling was conducted over proposed waste dump areas for sterilisation purposes.
An IP geophysical survey at Sadiola-Yatela commenced in June and has been partially completed, with some delays experienced due to logistical factors and weather. Hyperspectral core imaging of 93,000m of core was completed and will provide alteration based vectors for exploration targeting and predictive metallurgy. Processing of this data is ongoing with results expected in early 2013.
A comprehensive termite mound sampling programme was undertaken over the entire Sadiola concession during 2012. The programme has been successful in highlighting prospective areas on the lease along the FE trend and northeast extensions of the Sadiola mineralisation. Termite mound sampling was also started at Yatela and will continue next year. Portable XRF analysis of all termite mound samples is ongoing to provide multi-element data and identify potential pathfinder elements for target generation.
A three-year research programme by the Centre for Exploration Targeting (CET) from the University of Western Australia commenced in early 2012. The objective of this project is to review and enhance the geological understanding of the Sadiola-Yatela deposit. This will inform further exploration programmes within the area.
At Navachab, 23,741m of drilling was completed over several areas, with the emphasis on the expansion project, Main Pit down-plunge extension area, and the Okahandja targets.
Drilling of the expansion project consisted of 7,105m diamond drilling for Mineral Resource upgrades and 4,846m RC drilling, mainly for sterilisation purposes, over the waste dump area. A total of 7,495m diamond drilling was completed in the lower schist down-plunge target at the Main Pit.
Off-mine exploration focused on the Okahandja target area, with 2,127m drilling to test the geophysical and soil geochemical targets generated at Agagia. Soil geochemical sampling was conducted at the Cox Montis target and 560 soil samples were submitted for analysis and assay results are expected early next year.
At Tropicana, a revised Mineral Resource estimate was prepared. The total Mineral Resource has increased by 1.0Moz to 5.5Moz of contained gold. Open Pit Resources are now reported within an A$1,500/oz pit shell. The prefeasibility study will consider the trade-off between open pit and underground mining options and will provide recommendations as to the optimal mining approach. Study work has commenced with metallurgical testing underway and a mining and geotechnical review.
Drilling of 38,336m for the Havana Deeps prefeasibility study was completed during the year while 14,221m of drilling of near-mine targets continued during the year. Drilling completed on the Havana-Tropicana trend, the Springbok/Hat Trick area and Boston Shaker. Some encouraging results were obtained.
Exploration at Sunrise Dam focused on growing the Mineral Resource base so that Sunrise Dam has the platform from which it can deliver its business plan each year. This was achieved through the specific work that includes:
- in-mine exploration (35,739m), which extends the known Mineral Resource in areas proximal to existing development; and
- near-mine exploration, which determines an understanding of the potential for Sunrise Dam, through specific geological characterisation, and explores the areas around the mine and within enveloping tenure of 2,932m. This forms part of the mine life expansion project of 47,569m and includes the Vogue Mineral Resource of 28,897m.
A total of 115,137m was drilled in 420 drill holes. Drilling (66%) focused on deep extensions and longer-term Mineral Resource growth of the Vogue, Carey Shear and Astro-Sunrise Shear Lodes, whilst 33% of the drilling focused on in-mine exploration and mineral resource extension.
AngloGold Ashanti/De Beers Joint Venture
In SASA, a drilling programme was concluded in February with a total of 87 boreholes drilled. All but 3.5% of samples taken over the 260 x 60km exploration area contained gold. This suggests that the exploration is taking place within a significant gold province but that this search now needs to be narrowed down geologically to target areas of higher potential.
A full review of all data collected to date was conducted by the Joint Venture around mid-year and a number of work flows were identified for completion prior to a further review and exploration planning workshop to be held early next year.
In Nome, the environmental baseline studies field work was successfully completed and the first draft report issued. Side scan sonar, swath bathymetry and 2D seismics survey were completed (3,997 line km). Interpretation of the geophysical data has been completed and an initial geophysical model developed.
A ship-based sonic core drilling campaign was completed during the summer season and 454m of core retrieved. This core was transported to Cape Town where initial logging and sampling has started. A conceptual economic study was completed and indicated that a positive business case was possible. A prefeasibility study is expected to begin in 2013.