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Global exploration

MULTITUDE OF EXPLORATION OPTIONS

Total expensed exploration for 2011 amounted to $313m of which $98m was spent on greenfield exploration, $87m on brownfield and $19m on marine exploration. This includes $109m spent on prefeasibility 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.

Greenfield exploration

Location of AngloGold Ashanti greenfield exploration

Greenfield exploration
  1. 1
    Canada

    Baffin Is JV 
    Superior JV 
    Melville Project  

  2. 2
    USA

    Drum Mountain Project 
    Nome, Alaska 

  3. 3
    Colombia

    Western Cordillera 
    Rio Dulce 
    Quebradona 
    Anaima - Tocha 
    Chaparral 
    Salvajina 
    La Llanada 

  4. 4
    Argentina

    Santa Cruz (El Volcan) 

  5. 5
    Brazil

    Falcao JV 
    Juruena 
    Santana JV 
    (South Carajas Block)

  1. 6
    Guinea

    Siguiri Blocks 1-4 

  2. 7
    Gabon

    Dome JV 
    Ogooue 
    Amiga JV 

  3. 8
    DRC

    AGK JV Kilo Project 

  4. 9
    South Africa

    South African Sea Areas 

  5. 10
    Tanzania

    Oryx JV 
    Mkurumu JV 

  6. 11
    Ethiopia

    Stratex Afar JV 
    Gordoh JV 

  7. 12
    Djibouti

    Stratex Afar JV 

  1. 13
    Eritrea

    Akordat North 
    Kerkasha JV 

  2. 14
    Egypt

    Wadi Kareem JV 
    Hodine JV 

  3. 15
    Saudi Arabia 
  4. 16
    China

    Jinchanggou CJV 

  5. 17
    Solomon Islands

    Kele & Mase JV  
    New Georgia 
    Vangunu JV 

  6. 18
    Australia

    Cornelia Range 
    Tropicana JV 
    Viking 
    Gawler JV 

  7. 19
    New Zealand

    Sea Field Resources 

  1. Greenfield exploration countries
  2. Greenfield strategic alliances
  3. Pre-2011 100% AngloGold Ashanti
  4. Pre-2011 joint ventures
  5. New 2011 joint ventures
  6. 2011 100% AngloGold Ashanti
  7. Blue-sky – AngloGold Ashanti/De Beers
    marine exploration joint ventures

An expansive greenfield exploration programme was undertaken in 17 countries during 2011. 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, Democratic Republic of the Congo (DRC) and Canada. This compares with 276,346m drilled the previous year. 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 greenfields 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 joint-ventured or divested to maximise AngloGold Ashanti’s return on its exploration investment.

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 joint venture focusing on marine exploration.

A further $150m of expenditure is allocated to prefeasibility studies at the La Colosa and Gramalote projects in Colombia, as well as to feasibility studies on the Central Mongbwalu deposit in the DRC, and associated expenditures.

Strategic context

The five core strategic focus areas translated into the exploration strategy and execution of the business plan are summarised below:

People are the business – greenfield exploration, which is active in 17 countries, is undertaken by a highly diverse group of personnel in terms of age, gender, culture, nationality and technical skills. This depth has created a mobile workforce capable of global deployment. An integral part of the greenfield exploration team’s strategy is to provide employment for local personnel at all levels, assisting in engagement of communities from the earliest stages of exploration.

Maximise margins – in line with the exploration strategy, the objective is to achieve a greater than 25% return on investment. This requires new and significant discoveries every four to five years and a portfolio composition that maximises potential returns from projects not meeting the investment criteria. Discovery costs of less than $25 per ounce are targeted for AngloGold Ashanti discoveries and are calculated on the basis of total investment in exploration net of divestments.

Significant additional value can be ascribed to AngloGold Ashanti’s tenement positions in world-class districts that include the Colombian Cordillera, Birimian terrane in Guinea and the fertile greenstone terranes of eastern DRC.

Asset portfolio management – the greenfield exploration team maintains a balanced portfolio and a pipeline of projects at the various stages of exploration, from project generation to resource definition. This ensures a continuous opportunity flow through the pipeline in order to spread risk. Importantly, this requires diversification across new frontiers, emerging regions and known terranes. The range of ownership and partnership structures employed by AngloGold Ashanti helps achieve the desired variety of targets envisaged in this strategy. Important components for new discoveries and effective resource targeting include securing new search spaces and strategic landholdings whilst maintaining a balanced portfolio.

Grow the business – the greenfield exploration portfolio includes strategic world-class holdings in Colombia, Guinea, the DRC, Australia and the Arabian-Nubian Shield. Following the discovery and ongoing incremental size increases at La Colosa, Gramalote, Tropicana-Havana and Mongbwalu, the company has moved a number of projects forward in the discovery pipeline. Projects with emerging potential include Hutite (Egypt), Saraya and Koun Koun (Guinea) and Quebradona (Colombia).

In the Middle-East and North Africa, AngloGold Ashanti and its strategic alliance partner, Thani Investments, have made significant progress in building a regional tenement portfolio in Egypt and Eritrea. The Thani Ashanti Alliance Company has also applied for tenements in Saudi Arabia and Ethiopia and conducted exploration in joint venture with Stratex International in Ethiopia and Djibouti.

The strategic landholdings and the robust portfolio of projects from early to advanced stages position the company for significant growth through exploration.

Deliver sustainable outcomes – Greenfield exploration is committed to the integration of Project ONE into the business unit to ensure the strategy is supported by an appropriate organisational design and cross functional relationships within operating regions. The safety transformation programme is an integral part of the deployment of Project ONE with leadership and safety training programmes being crafted and progressively rolled out across the business unit through to the end of 2013.

Critical to operating a safe global business has been the development of a three-year intervention strategy to address safety performance, serious injuries and fatalities. The strategy focuses on aligning the Safety Transformation component of Project ONE with the implementation of AngloGold Ashanti safety standards.

During 2011, greenfield exploration in Guinea increased options for potential discoveries in Blocks 2 and 3. In the DRC, regional exploration work over the Kilo Greenstone Belt started to unlock potential, while in North Africa the Thani Ashanti strategic alliance made exceptional progress in Egypt and Ethiopia. In Colombia, exploration drilling at Quebradona confirmed the potential for copper-gold porphyry mineralisation which, coupled with the world-class La Colosa deposit in the greater Anaima-Tocha project area, represents an exceptional value proposition.

Significant achievements for 2011 included the delineation of additional pre-inferred gold ounces in Guinea and the resumption of drilling at the Quebradona project in Colombia.

Considerable progress was also made in advancing AngloGold Ashanti’s greenfield exploration portfolio elsewhere in 2011. Following the company’s entry into four new regions in 2009, 2011 saw rapid progress in the delineation of exploration targets, licence applications and associated approvals and exploration activities including drilling, airborne and ground geophysics and diamond drilling.

Encouraging drilling and trench results have been received from Egypt, Guinea, the DRC and the Solomon Islands.

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 is already underway in Canada, Gabon, China and elsewhere.

pathway to value - concept to resource definition

Project pipeline

AngloGold Ashanti holds a total of 97,531km² of high-priority greenfields tenements globally from which there is a robust project pipeline. This is illustrated 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. Elsewhere in Colombia, the completion of airborne magnetics and radiometrics and further mapping has resulted in new targets being defined and drilled at Quebradona (AngloGold Ashanti/B2Gold joint venture). Here a total of 4,711m was drilled targeting porphyry gold-copper mineralisation.

Elsewhere in Colombia, exploration among others was undertaken on the Rio Dulce and La Llanada tenement groups.

In Canada, exploration continued on properties forming part of the Superior joint venture with Laurentian Goldfields, where drill testing of targets generated by lake sediment geochemistry was completed in late 2011 in the Goldpines South joint venture. On the Baffin Island joint venture with Commander Resources, exploration work was limited to mapping and IP surveys on specific targets.

In Brazil, early stage exploration comprised of 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, using a combination of aeromagnetic interpretations and gold-in-soil geochemistry to target initial drill holes. A total of 15 diamond holes for a total of 3,663m were completed in 2011. The drill testing produced some encouraging early results but no ore grade intercepts.

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 greenfields 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 have 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 with regional soil geochemistry programmes that are expected to 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 4,009 diamond metres were drilled, 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 Gabon, AngloGold Ashanti is conducting exploration on an exclusive basis on the Ndjole and Mevang properties in partnership with Silver Bull Resources (formally Dome Ventures). The work has comprised regional geochemical sampling programmes and completion of a diamond drilling programme on the Ndjole licence.

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.

In Eritrea, AngloGold Ashanti is currently reviewing its investment. Exploration in partnership with Stratex International was conducted for epithermal gold mineralisation in the Afar depression of Ethiopia where the first-phase 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, an extensive 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. The potential for substantive epithermal gold mineralisation appears limited in the Vulu area. Exploration will now 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 drilling 4,911m, trenching, field mapping, soil and rock chip sampling, spectral studies and airborne electromagnetic surveying.

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. Greenfields 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, where aircore and RC drilling identified mineralisation. Best results include 20m @ 1g/t Au from 32m.

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.

In Australia, a total of 2,231 Aircore/RAB holes were drilled for 102,278m, 109 reverse circulation holes for 15,945m and six diamond holes for 1,032m. In addition, 18,417 surface auger samples were collected, 30,861-line kilometres of aeromagnetic and radiometric surveys were flown and 1,223 line kilometres of ground gravity data were acquired.

Brownfield exploration

Location of AngloGold Ashanti brownfield exploration

  1. 1
    United States

    Cripple Creek & Victor

  2. 2
    Colombia

    La Colosa
    Gramalote JV

  3. 3
    Brazil

    Serra Grande
    AGA Mineração

  4. 4
    Argentina

    Cerro Vanguardia

  1. 5
    Guinea

    Siguiri

  2. 6
    Mali

    Yatela
    Sadiola
    Morila

  3. 7
    Ghana

    Iduapriem
    Obuasi

  4. 8
    Namibia

    Navachab

  1. 9
    South Africa

    Vaal River
    Great Noligwa
    Kopanang
    Moab Khotsong
    Surface operations
    West Wits
    Mponeng
    TauTona
    Savuka

  1. 10
    Tanzania

    Geita

  2. 11
    DRC

    Kibali JV
    Mongbwalu

  3. 12
    Australia

    Sunrise Dam
    Tropicana JV

  1. Operations
  2. Advanced projects

AngloGold Ashanti continues to actively drive the creation of value by growing its major asset, namely its Mineral Resource and Ore Reserve. The drive is based on a well defined and active brownfields 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.

Borehole MMB5 completed its deflection drilling programme early in the year. Borehole MGR8 continued advancing (Deflection 9) and intersected the Vaal Reef in the last quarter. Deflection drilling continues. In MGR6 drilling of the long deflection is still in progress. MHH2 was started and advanced to a depth of 709m. Percussion drilling of the pilot hole was completed at MCY6 and diamond drilling will start on completion of MGR8.

UD51 advanced to 2,436m. Heavy losses of drilling fluids experienced during the year have been resolved by inserting casing into the hole. UD59 started drilling and advanced to 1,132m. Rigging was completed for UD60 and the casing is being inserted.

A series of shallow surface holes to the west of Kopanang started drilling in the third quarter. KGD1, targeting the Vaal Reef on the farm Grootdraai, advanced to a depth of 1,168m. The Vaal Reef was faulted out and a long deflection is now being drilled. KGD2, targeting the VCR also on Grootdraai, was drilled to 519m and has been completed. The drill site has been rehabilitated. KGD3 started drilling and advanced to a depth of 292.5m. KDPL1, targeting the Vaal Reef on the farm De Pont Landing, advanced to a depth of 719.1m. The hole is currently being recovered after the rods were dropped. Boreholes, KWH1 and KWH2 both started late in the year and reached depths of 63m and 103m respectively.

Continental Africa

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. A good example of this potential was drilled from Cut 8 and recorded 24.2m @ 22.17g/t Au from 262.5m.

Reconnaissance drilling (20,158m RC and DD holes) to support a growth strategy was undertaken on three induced polarisation (IP) targets, namely Nyankumbu, Nyakabale West and Mgusu and 14 electromagnetic (EM) targets which include Kibugwe 17A, 17B and 17C, Nyamikoma, Lwenge, Bugulula, Kukuluma East, Area 3 North, Bukolwa, Kanza, Mzingama and P30.

Diamond drilling was conducted at Kukuluma, Matandani and Area 3 deposits in the Kukuluma Terrain in order to help define an optimal processing route.

During 2011 a total of 87km of IP surveys were conducted at Nyakabale East, Kalondwa Hill and Star & Comet Extension areas.

Intensive geological and structural mapping was undertaken at Ridge 8, Star & Comet and the P30 area. An initial mapping phase commenced at the Kukuluma and Matandani pits; with reconnaissance mapping completed for the portion of the Kukuluma Terrain surrounding Kukuluma, Matandani and Area 3 deposits.

Guinea

At Siguiri in Guinea, 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 Sintroko, Tubani Extension and Kozan pits to define sulphide ore continuity below the current pit outlines.

A reconnaissance exploration programme in Block 1 continues to discover new geochemical anomalies, with a total of 5,211 geochemical surface samples collected during the year. A new discovery was made at Silakoro Project, on a previously unexplored trend, of a potential oxide Mineral Resource situated 2km west of the processing plant. Significant drill results included 23.38m @ 1.13g/t Au from 6m and 19.92m @ 9.77g/t Au from 6m.

IP surveys were completed over the Sokunu East reconnaissance target as well as over the Seguelen Mineral Resource 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 during 2011 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-UWA-CET 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.

A total of 13,067m was drilled into the old Teberebie Leach Pads during the year at the Iduapriem Gold Mine. Reduced drill rig availability has postponed a planned underground scoping study drilling programme until the first quarter of 2012.

Democratic Republic of the Congo

Exploration work progressed at Mongbwalu during 2011 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 mine dewatering holes at the Adidi Mine in support of the continued growth of the project. Six water monitoring holes were also completed and equipped.

A core re-logging 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 exploration drilling during 2011 connected the Sessenge deposit to KCD (9000 lode) and confirmed over two kilometres of continuous down plunge mineralisation. The first deep hole, DDD532 (1,346m) has confirmed mineralisation a further 450m down plunge from the existing block model. The lower 5000 and 9000 lodes were not intersected as the hole deviated. A second deep hole is currently underway.

The geological model identifies the potential lateral continuation of the 9000 lode and possible link between KCD and Gorumbwa. A programme of five diamond drill holes 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

During 2011 a total of 68,184 RC metres and 3,628 diamond core metres were drilled on the Sadiola Concession.

Additional drilling in 2011 involved the sterilisation around the Sadiola Sulphide Project (SSP) 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 from 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 RC and 1,805m of diamond drilling completed. A comprehensive termite mound sampling programme across the concession at 200 x 50m spacing 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, and only narrow mineralisation at KW18. 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 of drilling during 2011. Of this drilling, 48 holes (23,370m) were completed in the Main Pit NP2 down plunge, HW and FW vein areas and 135 holes (10,270m) were completed in the HME waste dump condemnation area.

Off mine drilling focused on the Anomaly 16 Valley and Okatjimukuju target areas with 41 RC holes drilled for 7,638m and 5 DD holes totalling 944m. This drilling tested geophysical targets generated at Anomaly 16 and exploration of the down plunge extension of the higher grade LS/LM ore zone as well as the western limb of the anti-formal structure. Promising assays to date indicate the continuation of the higher grade mineralisation on the LS/LM contact and the continuation of mineralisation in the LS at Anomaly 16. A total of 20 holes (2,008m) were drilled at EPL3275 Okatjimukuju target areas following up on gold in soil geochemical anomalies.

Americas

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 with LYDDH1616 being a good example and returning 2.7m @ 30.7g/t Au and 286.35g/t Ag from 326m. Exploration and Mineral Resource modelling to identify heap leach material was active during the year. Initial drilling was completed based on geophysical surveys and target identification work at the El Volcan project during the year.

Brazil

The 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. Results from Anomaly 1 indicate the potential of a large oxide deposit close to São Bento. No estimate of the gold content is possible at this stage but a coherent 1,200m anomaly has been defined with oxide mineralisation down to 200m. Borehole FCSII0283 is a good example of the better mineralisation and intersected 6.31m @ 16.2g/t from 37.4m.

Underground drilling at the Córrego do Sítio started during the year to develop the São 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 was successfully completed. The programme focused on Mineral Resource addition 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 estimation 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. A number of boreholes intersected thick mineralised packages to the north and have resulted in the orebody being extended. The best example of these boreholes was COL138 which intersected 240m @ 3.14g/t from 242m. The geological model was updated during the year to support the new Mineral Resource estimation and drilling support was provided to infrastructure selection studies.

United States

The drilling programme for Mineral Resource expansion and to improve high grade definition within the Mineral Resource area continued at Cripple Creek and Victor. In the expansion drilling, an increase in grade and tonnage was particularly noticeable for the Grassy Valley and WHEX areas where holes such as GR-952 intersected 74.7m @ 11.0g/t Au from 38m. A significant conversion of Inferred Mineral Resource to Indicated Mineral Resource occurred during the year. A drilling programme to provide additional samples for metallurgical test work of high grade material was completed.

Australasia

Australia
Grade distribution for Dolly gold lodes
Grade distribution for Dolly gold lodes [map]

At Tropicana, near-mine exploration has continued at the site, using up to four diamond and reverse circulation rigs, 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 Ore Reserve estimate increased to 56.4Mt at a grade of 2.16g/t Au, containing 3.91Moz Au, an increase of 0.54Moz. The increase was primarily due to the inclusion of the Boston Shaker pit, which added 0.24Moz and the conversion of Inferred Mineral Resource into Indicated Mineral Resource at Havana South, which added a further 0.26Moz Au.

Approval was given in late 2010 to proceed with a prefeasibility study on the Havana Deeps mineralisation and drilling for this project began in April 2011. The 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 ongoing and expected to continue until mid 2012. The project is due to be completed by the end of 2012.

Drilling was sufficiently advanced by year-end to announce a significant increase in the Mineral Resource as follows:

December 2011 Mineral Resource (attributable)
Classification Tonnes (millions) Gold (g/t) Contained (Moz)
Measured 19.77 2.14 1.36
Indicated 34.61 2.04 2.27
Inferred 7.43 3.56 0.85
Total 61.82 2.26 4.49

This represents an 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.

Work to date has successfully demonstrated the continuity of higher grade (potentially underground) mineralisation extending to depths around 1km, on the southern shoot at Havana in particular. The drilling shows the mineralisation remains open in all directions.

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, identification and delineation of the Vogue mineralisation was the highlight for 2011. Even though interruptions occurred, which included a period of extensive rainfall, when in excess of 250mm of rain fell in 10 days and leading to the failure of the wall, 67,602m were drilled. This includes 18,112m drilled as part of the regional exploration and tenement maintenance programmes.

The drilling proximal to the Cosmo and GQ lodes illustrated that gold mineralisation continues as both extensions to these lodes and as parallel subordinate structures that have been defined from the drilling. In addition to the Mineral Resource extension drilling, the deeper drilling defined a new zone of mineralisation, named Vogue. The Vogue mineralisation extends down plunge from the >1.5Moz Cosmo-Dolly system (see diagram) and forms geological complex zones that are manifested as broad domains of low- and high-grade gold mineralisation. These extend for more than 400m in length and to depths greater than 900m vertical.

Long-section view of major Sunrise Dam gold lodes
Long-section view of major Sunrise Dam gold lodes [graph]

Numerous intercepts have been returned and reported. Some key intercepts that include a composite of gold mineralisation and waste (up to 25m) include:

Vogue:

229.40m@5.10g/t Au
255m@4.41g/t Au
159m@1.57g/t Au
109m@2.06g/t Au
126.5m@1.96g/t Au
124.1m @1.54g/t Au
32m@14.56g/t Au

May include up to 25m of continuous waste to a cumulative total of 100m of waste, averaging >1g/t.

An aggressive and detailed exploration strategy planned for 2012 is expected to include drilling of 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 the 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 field trip 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 began during December 2011 and was completed in February 2012.