The strategic review of the project development and exploration programmes resulted in significant realignment of the global exploration programme.
Greenfields and brownfields exploration
Exploration at AngloGold Ashanti has two key processes aimed at adding significant value for the company:
- Greenfields exploration, which aims to make large, highvalue gold discoveries leading directly to new mines.
- Brownfields exploration, which is focused on delivering value through incremental additions to the Ore Reserve in existing mines as well as new discoveries in defined areas around existing operations.
AngloGold Ashanti’s greenfields exploration team has been recognised as an industry leader and has a proven track record that includes the world-class discoveries of La Colosa, Gramalote and Tropicana. These discoveries can be attributed to our committed and professional team of explorationists who work on a portfolio of highly prospective and strategic ground holdings. Greenfields exploration provides a pipeline of highquality and rigorously prioritised exploration projects, which in turn lead to the discovery of new deposits and mines.
“Greenfields exploration provides a pipeline of high-quality and rigorously prioritised exploration projects, which in turn lead to the discovery of new deposits and mines.”
AngloGold Ashanti’s greenfields exploration business unit underwent significant re-organisation in 2013, with the refocusing of the group’s project portfolio to achieve a cost saving of more than 25% in 2013 from an initially approved $100m to actual realised expenditure of $75m. Greenfields also adjusted the portfolio for a significantly reduced budget of approximately $35m in 2014. The global greenfields exploration footprint was rationalised by 26,000km² but AngloGold Ashanti remains committed to its core greenfields projects and still retains over 23,000km² of highly-prospective ground in three countries – Australia, Colombia and Guinea – while also maintaining small ground positions in Argentina and Brazil.
In 2013, advanced greenfields exploration activities were conducted in six countries with over 161km of diamond, reverse circulation and aircore drilling completed. Drilling programmes aimed to test new high-priority targets in Australia, Brazil, the DRC and the Solomon Islands, and continued to delineate existing discoveries in Guinea and Colombia. Withdrawal or divestment of projects following the restructuring of the group’s portfolio were conducted in the Middle East and North Africa region, the Solomon Islands, the DRC and the United States. Where the company has halted or suspended its activities, or is in the process of doing so, it will do so in a sensitive and responsible manner. The company intends to meet its community obligations and will work to ensure effective environmental rehabilitation is completed at its exploration sites as required.
AngloGold Ashanti actively drives the creation of value by seeking to continually grow its Mineral Resource and Ore Reserve. This is based on a well-defined and active brownfields exploration programme, innovation in geological modelling and mine planning, and continual optimisation of the asset portfolio. In 2013, a total of $146m was spent on brownfields exploration ($51m capitalised and $95m expensed). Brownfields exploration was undertaken around most operating mines and advanced projects. Over 590km of diamond, reverse circulation and aircore drilling was completed on brownfields projects.
Exploration continued with a total of 10 surface holes being drilled during the year, comprising four at Mponeng’s Western Ultra-Deep Levels (WUDLs), three at Moab Khotsong, two at Project Zaaiplaats, and the completion of one shallower surface hole to the south west of Kopanang. A total of 9,476m was drilled.
Mponeng (WUDLs): UD51 intersected a low-grade thin channel Ventersdorp Contact Reef at a depth of 3,837.5m in February 2013. A long deflection is currently being drilled to obtain a second cluster about 100m from the original intersection and targeting thicker reef channel. The deflection has advanced to 3,384.6m and is approximately 450m from reef. UD59 reached a depth of 3,645m when the drill rod string was dropped. This resulted in the bottom 2,100m of the original hole being abandoned. Re-drilling of the hole has advanced to 1,893.8m. Similar in-hole problems were experienced at UD60. Re-drill has advanced from 304.5m to 1,156.5m. Percussion drilling at UD58 began in December and reached a depth of 472m.
Moab Khotsong: MGR6 advanced to 2,416.9m before it was stopped in May 2013 in response to a call to reduce capital expenditure. MHH2 intersected a poorly developed reef at 3,144.0m in April 2013. The intersection is an unusual development of Vaal Reef in a fault zone. Further plans to drill MHH3 were abandoned and the Hormah Prospecting Right that was due to expire in July 2013 was allowed to lapse. MCY6 was stopped at a depth of 3,039.4m in April 2013 after structural modeling showed that the Vaal Reef target blocks lie much deeper and further to the east, beyond the Mining Rights boundary.
Zaaiplaats: MMB6 was the first of two Project Zaaiplaats holes to be drilled. The surface hole diamond drilling was completed within one year. MMB6 intersected Vaal Reef at 3,309.7m, only 11.3m above the depth expected from the 3-D seismic structural model. MMB7 the second of the Project Zaaiplaats holes intersected the Vaal Reef at 3,335.1m, 29m below the modelled reef position.
Kopanang: KGD12 was the final borehole in the Kopanang shallow-surface drilling programme. The hole was drilled to define the eastern margin of the high-grade VCR zone that was intersected in KGD8.
Democratic Republic of the Congo
Total drilling for exploration at Kibali was 15,904m, with an additional 6,151m drilled on regional projects. Two areas were identified in the Karagba-Chauffeur-Durba (KCD) deposit as having a high potential for Mineral Resource conversion, 9000 Lode up-plunge and 5000 Lode down-plunge, which incorporated drilling of the 3000 Lode down-plunge. Drilling to test the 5000 Lode up-plunge of KCD was also completed in the Durba Hill area. Drilling was also undertaken at Mengu Hill, Ndala and Pakaka, with a review of historic data completed at the Gorumbwa deposit.
Results from the 9000 Lode confirmed the Mineral Resource potential, although the results indicate that drill-testing of the eastern portion up-plunge programme is of lower priority to targeting higher grades zones further up dip. Drilling of the 5000 and 3000 Lode down-plunge indicate that the 3000 Lode diminishes in grade and thickness down plunge from KCD but continued strong mineralisation is associated with the 5000 Lode, despite some structural complexity.
Drilling of the up-plunge continuation of the 5000 Lode into the Durba Hill area of the KCD deposit confirmed the continuation of mineralisation, but also supported previously interpreted thinning of the mineralisation towards Gorumbwa.
At Mengu Hill, drilling showed that while there was reduced thickness and grade up-plunge, the down-plunge zone was underestimated. Sampling of geotechnical holes was also completed at Mengu Hill where they intersected the mineralisation.
At the Gorumbwa Deposit, a detailed re-logging and selective sampling of all historical Moto and KGM holes was undertaken. Digital capturing of historic underground mine plans to develop a 3D wireframe of workings was completed. The results of limited drilling at Ndala were disappointingly low in tenor.
“AngloGold Ashanti seeks to actively drive the creation of value by continually growing its Mineral Resource and Ore Reserve.”
At Obuasi, a total of 5,902m was drilled, with 5,127m underground exploration and 775m surface exploration. Underground drilling took place from 24S-383E, targeting the Sansu 3/Red Zone 9 area. Surface drilling was limited to infill at Gyabunsu North.
At Iduapriem, a total of 4,813m RC pre-collar and diamond tail drilling was completed in Blocks 7 and 8. In addition, four diamond drill holes were drilled in the Ajopa area for geotechnical purposes but the data will inform the geological and Mineral Resource model. Reconnaissance mapping and sampling was undertaken around blocks 1, 5, 7 & 8 Footwall, and Bankyim.
At Siguiri, brownfields exploration activities concentrated on the Block 1 licence area with a total of 86,200m drilled. Drilling focused on reconnaissance, Mineral Resource delineation and infill projects both for oxide and fresh-rock targets. Block 1 target generation programmes included induced polarisation (IP) and resistivity geophysical surveys over Komatiguiya NW, Niono and Seguelen. An updated geological map of the total Siguiri lease area was also completed during the year.
Sterilisation drilling of the new tailing storage facility (TSF) return water dam south of the main CIP plant was completed with no significant gold values reported.
Fresh-rock drilling focused on the mineralisation potential below the pits of Bidini, Kami and Seguelen, with limited fresh-rock drilling also at Eureka, Kossise South East, and the Komatiguiya target. At Bidini pit access and drilling issues led to the introduction of directional drilling capabilities on site. At Kami, several encouraging assay results have been received to date, along with frequent reports of visible gold in the drill core. Freshrock drilling at Seguelen tested the continuation of mineralisation in fresh rock below Seguelen Pushback 1 and 2. Drilling identified three sets of gold-bearing quartz-carbonate veins, with the mineralisation also showing a strong lithological control.
Greenfields exploration drilling continued to delineate significant oxide mineralisation on the Kounkoun trend, located within 50km of the Siguiri mine, in Block 3. To date, mineralisation has been defined through drilling over 6,300m and 1,900m strike lengths in the eastern and western zones, respectively. The oxidised zone is typically between 60m and 100m deep, below which mineralisation continues in fresh rock. In 2013, a total of over 7,000m of aircore, 35,000m of reverse circulation and 3,100m of diamond drilling was completed with drilling continuing to indicate further upside potential. Results from these drill programmes were very encouraging and included, but were not limited to (true widths), 38.4m @ 2.97g/t Au in KKRC373, 52.2m @ 2.11g/t Au in KKRC361 and 15.5m @ 5.58g/t Au in KKRC456*. Within Block 2 and Block 4, reconnaissance drilling and ground geophysical surveying was completed.
At Geita, a total of 38,239m of drilling was completed. A significant portion of exploration effort was dedicated to infill drilling programmes in active open pits (Geita Hill, Nyankanga and Star & Comet), as well as on their respective extensions. Limited pre-resource drilling programmes were undertaken to test ’blue sky’ targets.
Two holes were drilled at Nyankanga to test a revised geological model that indicates the potential for repetitions of the Nyankanga style of mineralisation at depth, beneath the current pit. Both drill holes intersected mineralisation, with one intersecting a mineralised Banded Ironstone Formation package at a depth of approximately 800m.
Non-drilling activities undertaken during the year included regional and target-scale mapping, target consolidation, pit mapping and geology modelling. Considerable advances have been made in the geological understanding at both deposit and regional scales.
A total of 40,220m of reverse circulation drilling was completed at Sadiola and Yatela, with the focus on Sadiola where 28,038m expensed drilling was completed at Sadiola NE, Sadiola FNE, Sadiola Strike Extension, Tambali, Voyager West, S12, and Timbabougouni. Capital drilling amounted to 9,134m of reverse circulation at FN3 and 2,264 reverse circulation metres dedicated to sterilisation of the North-East corner of the Sadiola Sulphide Project waste dumps.
At Sadiola work was completed on a number of oxide targets close to the FE3/4 complex, Tambali and Sadiola as well as further away along known mineralised extensions. At S12 prospect, further exciting drilling results were recorded with both oxide and sulphide potential. The prospect is however situated adjacent to the existing TSF and indications are that mining will impact on the integrity of the TSF. Positive results for follow up have also been achieved at Tambali targets. Infill drilling was completed at FN3 to improve confidence in the Mineral Resource and infill drilling at Tambali will be incorporated into the next Mineral Resource model.
Drilling at Sunrise Dam included surface and underground diamond and reverse-circulation drilling totalling 52.9km. Drilling activities were largely focused on infill and extension targets following budget restructuring which resulted in the demobilising of all surface diamond rigs (for the MLE project) and all underground diamond rigs until late into the third quarter of the year. Most drilling at Sunrise Dam was conducted with underground reverse-circulation rigs (24.1km).
In Western Australia, greenfield exploration activities on the Tropicana project, in joint venture with Independence Group NL (AngloGold Ashanti interest 70%), progressed well through the year with over 72,000m of aircore, 4,800m of reverse circulation and 600m of diamond drilling completed. Encouraging results were returned from several prospects. Geophysical surveys were also completed over key prospects and included airborne EM and magnetics, ground-based IP and EM, and seismic surveying. Results from these surveys are currently being assessed and will be used to plan follow-up work in 2014. In New South Wales, a farm-in agreement was executed with Mungana Goldmines to explore for Au-Cu porphyries. During the year, ground gravity and induced polarisation geophysical surveying was progressed over key prospective areas to assist in delineating targets for diamond drill testing.
At Cerro Vanguardia, a total of 60,688m were drilled in programmes designed for Mineral Resource expansion and extension. Follow-up drilling for vein extensions along strike and at depth, guided by geophysical surveys, identified additional mill feed material. Exploration and Mineral Resource modeling also successfully identified material to process at the heap leach facility.
In the Iron Quadrangle, the Mineral Resource development drilling programmes (89,322m) continued at the Cuiabá and Lamego mines with a continued emphasis on support to longterm planning and Mineral Resource definition. The surface drilling programmes at the Córrego do Sítio mine continued to expand the oxide Mineral Resource, while underground drilling at Córrego do Sítio focused on developing the Sangue do Boi and São Bento Mineral Resource for production. Regional exploration programmes were conducted to test various nearmine satellite projects.
At Serra Grande, drilling totalled 62,310m. The exploration focused on the newly identified Inga mineralised structure below the Pequizão ore body. Regional early phase exploration continued, with geophysical surveys and soil sampling campaigns continuing to be useful methods for target identification in preparation for surface drilling programmes in the district.
In Brazil, greenfields exploration progressed on the Graben project, in joint venture with Graben Mineração (AngloGold Ashanti interest 51%). Following the completion of high-resolution airborne radio/magnetics surveying and reconnaissance soil geochemistry, approximately 13,000m of aircore and 3,000m of diamond drilling were completed on priority targets within the highly prospective Juruena Belt.
“Exploration (37,459m) in the Gramalote area was focused on infill drilling to support the updated Mineral Resource estimation for the Gramalote Central deposit.”
Quebradona: In Colombia, focused greenfields exploration efforts continued at the Nuevo Chaquiro target, part of the Quebradona project, in a joint venture with B2Gold (AngloGold Ashanti’s interest 84.6%) with over 12,000m of diamond drilling completed. The Nuevo Chaquiro target is a porphyryrelated, copper-gold mineralised stockwork system, located within the Western Cordillera, where long intersections of copper mineralisation with gold credits were intersected during 2012. Diamond drilling in 2013 aimed to delineate the limits of this zone and define the presence of a higher-grade core. Results from the year’s drill programmes were very encouraging, and included, but were not limited to, 686m @ 0.72% Cu and 0.33g/t Au in CHA-039, 402m @ 0.53% Cu and 0.26g/t Au in CHA-032, and 430m @ 0.48% Cu and 0.22g/t Au in CHA-046*.
Gramalote: Exploration (37,459m) in the Gramalote area was focused on infill drilling to support the updated Mineral Resource estimation for the Gramalote Central deposit. This programme included the drilling of a detailed grade-control spaced block. Drilling programmes were also conducted to expand the nearby Monjas West target. As part of the prefeasibility study, additional drill holes were completed to support highwall design and condemnation drilling for the proposed plant site, waste rock, and tailings storage facilities.
La Colosa: At La Colosa, the Mineral Resource development drilling (10,002m) continued at a slower pace compared to previous years as the emphasis was on other projectrelated drilling which was expanded to support geotechnical, hydrological and site infrastructure studies. The geological model was updated during the year as part of the Mineral Resource addition that expanded the deposit to the north-west and at depth. The main deposit remains open to the north-west and drilling continues to explore the limits of the ore body.
The Mineral Resource development drilling programme continued during the year at Cripple Creek & Victor. A total of 43,691m was completed. Infill drilling continued to improve definition of material within the current mine designs that will feed the mill facility currently under construction. Other drilling was directed toward identifying expansion opportunities for the current open pit operations through highwall laybacks. Selective drilling was also conducted to test deeper targets below or adjacent to planned open pit designs that may provide additional mill feed material.
- * See AngloGold Ashanti 2013 quarterly reports and market releases on exploration activities for full details.