Our exploration programmes enable us to ultimately expand our Ore Reserve and are based on consistent standards and processes across the AngloGold Ashanti portfolio which are guided by peer reviews.
We identify the best group of drill targets, prioritising those that have the highest potential for success.
We have developed a system – Exploring for value (E4V) – that goes beyond SAMREC limitations to ensure that our exploration activities are focused on maximising value for the business and allow us to bring into play, at an early stage, very low confidence material. This means we can ensure our exploration pipeline can deliver into our life-of-mine (LOM) plans at the right time.
The system allows for an understanding of the geology from the earliest stage of development. In addition to integrating our E4V process with our LOM planning, we have also integrated our E4V process with our accounting standards. Through this integration, as an area is explored and drilled, a series of reviews and appropriate economic studies are used to support the next level of exploration.
Targeted investments during the year led to two positive advances, with Pure Gold Mining, in which we have a 16% stake, continuing to ramp up at the Madsen mine redevelopment in Red Lake, Ontario. Further, AngloGold Ashanti made an offer to purchase Corvus Gold Inc. and the acquisition was completed in January 2022. The Company also actively monitors for new early-stage opportunities that would be a potential fit for our portfolio.
Some highlights of our greenfield and brownfield exploration work follow.
Our greenfield exploration programmes are designed to discover a new Mineral Resource that will ultimately lead to the development of new gold mines. In 2021, $38m was spent on greenfield exploration. Exploration tenements cover over 4,400km2 of highly prospective ground in four countries – Australia, Brazil, Argentina and the United States. In total, 114km of diamond, reverse circulation (RC) and aircore drilling was completed in greenfield exploration programmes in 2021.
In the United States, a total of 25,538m of RC and 14,581m of diamond drilling was completed during the year at the Silicon project near Beatty, Nevada. Work focused on expanding the project along strike and at depth. Infill drilling was completed as part of a successful conceptual study that defined a first Inferred Mineral Resource of 3.37moz of gold at 0.87g/t and 14.17moz silver at 3.66 g/t contained in 120.44Mt constrained within a pit optimisation completed at a $1500/oz gold price. Development drilling to expand gold mineralisation and tighten average drill spacing to increase the Mineral Resource classification will continue as part of project studies in 2022.
At the Merlin target, in the Silicon project tenement area, 5,198m of RC and 7,104m of diamond drilling were completed. The drilling tested a target area with favourable volcanic stratigraphy and widely spaced gold-bearing drill intercepts that will be followed with additional drilling in 2022.
In Argentina, field programmes started in the fourth quarter of 2021 with systematic talus fines (890 samples) and ridge and spur sampling (225 samples) undertaken at the El Cori project.
During 2021, brownfield exploration activities were undertaken across the globe. We completed 1,059km of drilling with a total expenditure of $83m (capital) and $76m (expensed) for the year.
Tanzania: Capitalised (underground) and expensed (surface/underground) drilling programmes completed a total of 167,392m during the year at a cost of $37m.
Mineral Resource development drilling was carried out at Star & Comet Cut 2 and Cut 3 and assay results confirmed the continuity of the mineralisation for both Cuts. While exploratory drilling conducted at Star and Comet Cut 3 towards Ridge 8 returned results confirming open-ended mineralisation. Results at Cut 4 confirmed the hanging wall and footwall structures as modelled and exploratory drilling results from Cut 5 confirmed the continuity of the mineralisation.
At Nyankanga Block 1 and Block 2, the drilling results confirmed up-dip continuity of the mineralisation for both targets. The results from a short drilling programme at Block 5 suggest possible down-dip continuity of mineralisation. Drilling results from Geita Hill confirm open-ended down-dip extensions of the ore zones. At Lone Cone, the results confirm the down-dip continuity of mineralisation and increased the Mineral Resource model confidence.
Results from exploration drilling at Nyamulilima Cut 1 and 2 confirmed the model. The assay results from the sterilisation drilling for a proposed waste dump site returned no significant intersections, and at Xanadu, drilling is in progress with the results, so far, not showing obvious down-dip continuity.
Non-drilling exploration programmes consisted of surface geological mapping and integration of various geological datasets to better understand the sub-surface geology in an effort to identify new exploration targets.
Guinea: Capitalised and expensed drilling programmes completed a total of 34,336m during the year at a total cost of $7m. The 2021 drilling was impacted by contractor changes and significant delay in mobilising three of the contractor’s new rigs.
Ghana: At Obuasi, drilling continued with a total of 37,583m drilled in the underground exploration programmes at a cost of $7m. Exploration was impacted by the suspension of underground mining activities after the tragic death of one of our colleagues in May 2021. The resumption of the drilling was staged, with the first rig restarting in July 2021. Exploration and infill drilling activities in the year focused on 41 Level in Blocks 1 and 10, 32 Level in Blocks 8 and 10, 21N1, 26 and 26N3 Levels in Sansu and stockpiles along the ODD decline.
Democratic Republic of the Congo: Capitalised and expensed drilling programmes, at Kibali, completed a total of 16,035m during the year at a cost of $4m.
Tete Bakangwe was delivered as an opportunity, and post Mineral Resource conversion drilling it has been added to the mine plan for 2022.
First phase drilling results testing down plunge continuity of high grade at Kalimva support an underground project. At KCD, step out holes have confirmed continuity of 3000, 5000 and 11000 system 500m down plunge, with additional mineralisation below 11000 lode.
In Argentina, a total of 38,895m of drilling was completed at a cost of $7m. Exploration was focused on creating new Mineral Resource which could be converted to Ore Reserve to extend the current life of mine.
In Brazil, at Cuiabá and Lamego, 151,042m were drilled at a cost of $14m.
In Colombia, at Quebradona, work was completed on drill hole relogging, tuff differentiation logging, geometallurgical modelling and geology project support. Preparation and support for the geotechnical campaign including laboratory follow up was started as were routine measurements of groundwater levels, flow stations and rain stations.
- Our planned investment (capital and expensed) in brownfield exploration drilling ramps up to a level of approximately $210m to $220m for Ore Reserve and Mineral Resource additions in 2022
- We expect another year of good Mineral Resource and Ore Reserve delivery across the portfolio
- We have expanded our project exploration budget in 2022 to allow for expanded drilling in Nevada
- We continued to take advantage of field restrictions that were in place during most of 2021 to generate a group of new terranes and districts through data reviews and desktop assessments for field validation in 2022