Review of exploration and development
Total expensed exploration for 2011 amounted to $313m, of which $98m was spent on greenfield exploration, $87m on brownfield exploration and the balance of $19m on marine exploration. A further amount of $109m was spent on prefeasibiity studies. The main objective of AngloGold Ashanti’s greenfield exploration team is to make significant, high-value gold discoveries in new and existing regions, while brownfield exploration focuses on incremental additions to known orebodies and new discoveries in defined areas around existing operations.
For 2012, expensed exploration of $230m is planned (including expenditure at equity-accounted joint ventures), with $108m planned for greenfield exploration, $102m allocated for brownfield exploration and a further $20m for the De Beers marine joint venture. A further $150m of expenditure is allocated to prefeasibility studies at the La Colosa and Gramalote projects in Colombia, as well as feasibility studies at Central Mongbwalu deposit in the DRC and associated expenditures.
Baffin Is JV
Drum Mountain Project
Anaima - Tocha
Santa Cruz (El Volcan)
(South Carajas Block)
Siguiri Blocks 1-4
AGK JV Kilo Project
South African Sea Areas
Stratex Afar JV
Stratex Afar JV
Wadi Kareem JV
Kele & Mase JV
Sea Field Resources
- Greenfield exploration countries
- Greenfield strategic alliances
- Pre-2011 100% AngloGold Ashanti
- Pre-2011 joint ventures
- New 2011 joint ventures
- 2011 100% AngloGold Ashanti
- Blue-sky – AngloGold Ashanti/De Beers marine exploration joint ventures
An extensive greenfield exploration programme was undertaken during 2011 in 17 countries. A total of 213,441m of diamond, reverse circulation and aircore drilling was completed in testing existing priority targets and in the delineation of new targets in Australia, Colombia, Brazil, Argentina, the Solomon Islands, Gabon, Guinea, Egypt, Ethiopia, the DRC and Canada. Significant airborne geophysical surveys were undertaken in Colombia.
Greenfield activities are undertaken through joint ventures, strategic alliances and wholly-owned ground holdings. The principal objective of the greenfield exploration team is value creation through the discovery of new long-life, low-cost mines that maximise shareholder value. Discoveries and ground positions that do not meet certain investment criteria are jointventured or divested to maximise AngloGold Ashanti’s return on its exploration investment.
Following the La Colosa, Gramalote, Tropicana-Havana and Mongbwalu discoveries, greenfield exploration teams are targeting new discoveries in Colombia, Australia and the DRC. At the same time, prospects in Guinea and Egypt have advanced from early stage to tangible projects, where multiple intersections of potentially economic gold mineralisation have been intersected.
Before any further expansion of the exploration portfolio can be considered, the focus has shifted to prioritising expenditure on projects with potential for significant near-term discoveries. At the same time, projects that have not met requirements will be monetised. This process already underway in Canada, Gabon, China and elsewhere.
AngloGold Ashanti holds a total of 97,531km2 of high-priority greenfield tenements globally from which there is a robust project pipeline. This is illustrated in the graph alongside for a number of key regions (this does not reflect the full extent of the project portfolio).
In the Americas, the principal area of focus has been to advance exploration on a number of key projects in Colombia. This has included further mapping and airborne surveys over the Anaima-Tocha project area, covering some 600km2 predominantly to the north of La Colosa. It is anticipated that a number of drill-ready projects will be explored in 2012 once permits have been obtained. At the Quebradona project (AngloGold Ashanti/B2Gold joint venture) a total of 4,711m was drilled targeting porphyry gold-copper mineralisation.
In Brazil, early stage exploration comprising mapping and regional geochemical programmes, was undertaken on the wholly-owned Juruena Belt tenements. The Falcão joint venture with Horizonte Minerals commenced drill testing of greenstone hosted gold mineralisation. A total of 15 diamond holes for a total of 3,663m was completed in 2011.
In sub-Saharan Africa, greenfield exploration programmes were undertaken in the DRC, Guinea, Gabon and Tanzania, with a number of prospects in Guinea and the DRC exhibiting potential. In Guinea, the greenfield exploration teams are exploring the regional tenements that comprise a combined area of 1,685km2. Regional geochemical programmes have defined a number of significant gold-in-soil anomalies with strike lengths of up to 10km. At Saraya and Saraya South, located in Block 2 to the west of the Siguiri, ore-grade intercepts were returned for multiple holes. Similarly, at the Koun Koun prospect, located in Block 3 to the east of the Siguiri operations, drilling beneath robust gold-in-soil anomalies has returned ore-grade intercepts in a deeply weathered profile.
In the DRC, AngloGold Ashanti holds an 86.22% interest in Ashanti Goldfields Kilo (AGK), while the remaining 13.78% is held by the state-owned gold company SOKIMO. Of the 7,443km2 previously held under exploitation licences by SOKIMO, 5,447km2 has been transferred to AGK under the terms of an agreement with the government, with 399km2 pending transfer at the end of the year. Significant progress was made in regional soil geochemistry programmes that will provide significant coverage over much of the landholding during 2012. This, combined with detailed geologic mapping and structural interpretation, has enabled the ranking and prioritisation of drill targets. During 2011, a total of 4,009m of diamond drilling was undertaken, with some encouraging results. A total of 789 trench samples were taken at a number of prospects, some of which returned promising gold grades.
In the Middle East and North Africa, exploration is conducted through a regional strategic alliance with Dubai based Thani Investments. Since the inception of the alliance in mid-2009, significant progress has been made on advancing exploration projects on the Wadi Kareem and Hodine concessions in Egypt. The Hutite project, located on the Hodine concession, is an orogenic gold deposit where the alliance has to date completed 54 diamond holes for a total of 12,352m. Visible gold and significant intercepts have been returned from many of the completed diamond holes. Mineralisation extends over a strike length greater than 1.6km.
Elsewhere in the region, early stage exploration is conducted on alliance-held licences in Eritrea. Exploration in partnership with Stratex International was conducted for epithermal gold mineralisation in the Afar depression of Ethiopia where the firstphase drill programme intersected encouraging low- to moderate-tenor gold mineralisation. The alliance has continued with project generation activities in Saudi Arabia and a number of licence applications have been made.
In the Solomon Islands, where AngloGold Ashanti is in joint venture with XDM Resources, a dominant land position is held over the New Georgia Island chain. Work has been focused on specific epithermal and porphyry targets, including Vulu, Mase and Konga. Future work will focus on the broader region in anticipation of securing additional land access agreements. The joint ventures collectively cover 1,707km2 in the New Georgia Belt, effectively consolidating the entire island chain. Exploration activities in 2011 included 4,911m of diamond drilling, mapping and sampling programmes.
In China, AngloGold Ashanti is in the process of divesting its 70% interest in Gansu Longxin Minerals CJV located in the Gansu Province of western China. All active exploration activities have been concluded in China.
The Tropicana joint venture (AngloGold Ashanti 70%, Independence Group NL 30%) is systematically targeting a belt of tectonically reworked Archaean and Proterozoic rocks on the eastern margin of the Yilgarn Craton, Western Australia. Greenfield exploration in the Tropicana joint venture during 2011 focused on regional aircore drilling and reverse circulation/diamond drilling of seven priority targets. A number of prospects have been identified for further work including the Iceberg prospect, located 35km south of the Tropicana gold mine. The wholly-owned Viking project covers the interpreted southeast extensions of the Tropicana belt. Exploration during 2011 included airborne magnetics/radiometrics, regional auger sampling and aircore drilling of selected targets. Several auger anomalies have been identified for drill testing.
Cripple Creek & Victor
- Advanced projects
AngloGold Ashanti continues to actively drive the creation of value by continually growing its Mineral Resource and Ore Reserve through a well-defined and active brownfield exploration programme, innovation in geological modelling and mine planning, and continual optimisation of its asset portfolio.
South Africa: A total of 14 surface holes were drilled during the year, five at Moab Khotsong, three at Mponeng and six shallower surface holes to the west of Kopanang.
Argentina: At Cerro Vanguardia, the drilling programmes for Mineral Resource expansion and extension continued during the year. Follow-up drilling for vein extensions laterally and at depth was successful, identifying bonanza zones in the Lucy vein at depth. Exploration and Mineral Resource modelling to identify heap leach material was active during the year. Initial drilling at the El Volcan project, based on geophysical surveys and target identification work, was completed.
Brazil: Mineral Resource development drilling programmes continued at the Cuiabá and Lamego mines. The surface drilling programmes at the Córrego do Sítio project to expand the oxide Mineral Resource were successful, especially at the Rosalino and Anomaly 1 targets. Underground drilling at the Córrego do Sítio started during the year to develop the Sao Bento and Sangue do Boi sulphide orebodies. Exploration work in the Nova Lima area beyond the production centres included completing the deep drilling programme at Raposos that identified a second mineralised zone called Santa Catarina, in addition to the main ES and EW orebodies. Regional exploration programmes were conducted at the Pari, Mariana, and Bento Rodriques projects.
At Serra Grande the first year of the ‘fast track’ exploration programme, to rapidly identify additional resources, was successfully completed. A total of 70,000m of diamond drilling was executed. The programme was focused on Mineral Resource additions along the main orebodies and regional areas. Pequizão, Mina Nova, Mina III and Structure NW/Cajueiro were the main targets. Geophysical surveys were conducted to support exploration for the Mina III and Palmeiras Mine down-plunge extensions. Soil sampling campaigns were done to define targets at Cajueiro, Structure NW and Boa Vista (Votorantim Metais joint venture) regional targets.
Colombia: Exploration at the Gramalote area was focused on infill drilling to support the new Mineral Resource estimate for the Gramalote Central deposit. Drilling programmes were also conducted for the satellite targets at Monjas Oeste, Monjas Este, El Limon, El Topacio and Trinidad. As part of the prefeasibility study, geotechnical drillholes were completed around the proposed pit limit to support highwall design, and condemnation drilling started for the potential waste dump and tailings storage facilities.
At La Colosa, the Mineral Resource development drilling programme ramped up to five drills by the end of the year with 47,619m completed. The geological model was updated to support the new Mineral Resource estimation and drilling support was provided to infrastructure selection studies. A new structural geology model was also completed.
USA: The drilling programme for Mineral Resource expansion and to improve high grade definition within the Mineral Resource area continued at Cripple Creek & Victor. Increase in grade and tonnage was particularly noticeable for the Grassy Valley and WHEX areas. A significant conversion of Mineral Resource to Ore Reserve occurred during the year.
Tanzania: At Geita, Mineral Resource drilling over the Nyankanga, Geita Hill, Geita Hill East, and Star and Comet areas was completed during the year. Assay results proved the down-dip potential underground extension of the Nyankanga deposit, which still remains open at depth. Reconnaissance drilling to support a growth strategy was undertaken on three induced polarisation (IP) targets, namely Nyankumbu, Nyakabale West and Mgusu and 14 electro-magnetic (EM) targets. Diamond drilling was conducted at Kukuluma, Matandani and Area 3 deposits in the Kukuluma Terrain to help define an optimal processing route. During 2011 a total of 87km of IP surveys were conducted at Nyakabale East, Kalondwa Hill and the Star & Comet Extension areas. Intensive geological and structural mapping was undertaken at Ridge 8, Star & Comet and the P30 area.
Guinea: At Siguiri, brownfields exploration activities in 2011 focused on the Block 1 licence area with a total of 153,955m drilled during the year. Mineral Resource drilling of oxide material concentrated on Kozan, Sintroko and Sokunu. Fresh rock drilling focused on the pits of Sintroko, Tubani Extension and Kozan to define sulphide ore continuity below the current pit outlines. A reconnaissance exploration programme in Block 1 continues to discover new geochemical anomalies. A new discovery was made at the Silakoro Project, on a previously unexplored trend, of a potential oxide Mineral Resource. It is situated 2km west of the processing plant. IP surveys were completed over the Sokunu East reconnaissance target as well as over the Seguelen Mineral Resources as a type-deposit for further targeting. A gravity survey was completed over a promising shallow oxide target at Silakoro.
Ghana: Surface exploration resumed on the Obuasi concession to evaluate any shallow mineralisation potential at the Anyankyerim deposit and results to date are positive. Mineral Resource upgrade and extension drilling achieved a total of 4,413m. Underground drilling to explore the Obuasi Deeps below 50 level and southern extensions of the current mining areas above 50 level continued during the year with a total of 3,771m achieved. A joint Obuasi-University of Western Australia-Centre for Exploration Targeting three-year research project commenced mid-year, with the primary deliverable being an integrated 4D model for controls on the geometry of mineralisation within the Obuasi system. The study is expected to enhance delineation of the Obuasi deeps Mineral Resource and guide exploration strategies in the Ashanti belt and the greater Birimian. Drilling of the old Teberebie Leach Pads was undertaken during the year at the Iduapriem gold mine. The reduced drill rig availability has postponed a planned underground scoping study drilling programme until the first quarter of 2012.
DRC: Exploration work progressed at Mongbwalu with 26 diamond core holes completed for 6,446m and 18 RC holes for 2,755m. These were predominantly Mineral Resource drilling and metallurgical holes at Kanga, and included mine de-watering holes at the Adidi mine in support of the continued growth of the project. A Mongbwalu core relogging exercise was completed during 2011 with 366 diamond holes re-logged to support the re-estimation of the overall geological Mineral Resource and increase the structural understanding of the deposits. A resistivity survey was undertaken over the Nzebi and Adidi faults in support of this work.
At Kibali, drilling connected the Sessenge deposit to KCD (9000 lode) and confirmed over 2km of continuous down plunge mineralisation. The first deep hole (1,346m) has confirmed mineralisation a further 450m down plunge from the existing block model. A second deep hole is currently under way.
The geological model identifies the potential lateral continuation of the 9000 lode and possible link between KCD and Gorumbwa. A programme of five diamond drillholes for 3,980m has been approved, which will also test the 3000 lode extension towards Durba hill where access was previously not possible due to the presence of Sokimo infrastructure. This drilling is scheduled to take place during 2012.
Mali: A total of 68,184m RC and 3,628m diamond core holes were drilled on the Sadiola Concession.
Additional drilling involved the sterilisation around the Sadiola Sulphide Project for planned infrastructure. Preliminary results from multi-element analysis revealed potential for economic molybdenum and work is ongoing to assist with a desk-top study to investigate the financial benefit of potentially recovering molybdenum by-product.
Exploration over the Yatela concession followed an aggressive programme based on a short life of mine to identify and test any additional oxide opportunities in 2011, with 21,888m of RC and 1,805m of diamond drilling completed. A comprehensive termite mound sampling programme across the concession, together with ground gravity and IP geophysics surveys, were carried out concurrently with the drilling to aid further target generation. Results to date indicate promising shallow oxide intercepts at the Badji target to the NW of the Yatela mine. Drilling to follow up on mapping targets north of Alamoutala North satellite pit also returned encouraging results.
Namibia: Exploration programmes at Navachab completed 259 holes totalling 39,085m during 2011. Off-mine drilling focused on the Anomaly 16 Valley and Okatjimukuju target areas with 41 RC holes drilled for 7,638m and five diamond drillholes totalling 944m.
Australia: At Tropicana, near-mine exploration has continued at the site with extensive infill drilling being completed at Boston Shaker and Havana South Prospect. This has enabled identification of significant additions to the Ore Reserve, the estimate of which increased to 56.4Mt at a grade of 2.16g/t of gold, containing 3.91Moz of gold, an increase of 540,000oz.
Drilling for the prefeasibility study on the Havana Deeps project began in April 2011. This project is focused on extending the higher grade parts of the Havana mineralisation down plunge beyond the bankable feasibility study pit limits and reviewing the open pit and underground mining options for this mineralisation. Drilling is expected to continue until mid 2012, with the project due for completion by end 2012.
Drilling was sufficiently advanced by year-end to announce a significant increase in the Measured, Indicated and Inferred Mineral Resource for the project of 1.05Moz of contained gold or almost 20% over that estimated in December 2010. The bulk of this increase (1.00Moz) is in the underground component of the estimate which increased to 1.63Moz.
At the Sunrise Dam gold mine, near-mine exploration focused on extensions to the known mineralisation, in addition to defining large targets beneath the deposit. While investigating extensions to the GQ, Cosmo and Dolly lodes, identifying and delineating the Vogue mineralisation were the highlights of 2011. Initial results have been most encouraging and an aggressive and detailed exploration strategy is planned for 2012, which will include drilling the extension and Vogue targets from both surface and underground positions.
AngloGold Ashanti/De Beers Joint Venture: Results from the seafield sampling campaign in New Zealand were analysed and, although offshore gold was detected, the grades did not warrant any further follow up work. Subsequently a decision was made to relinquish the offshore prospecting licences.
Exploration activities in the South African Sea Areas (SASA) offshore concessions of ~28,000km2 entailed the following:
- logging, sampling and assay of a large number of historical vibrocores and samples;
- a geophysical survey campaign of ~3,300km of seismic data;
- an 11-day vibrocoring campaign during which 38 cores were collected; and
- a reconnaissance fieldtrip to the west coast of South Africa.
All of the above was used to compile a geological and mineralisation model which was used to derive exploration targets for the coring campaign that commenced during December 2011 and was completed in February 2012.