The Lamego mine is an underground gold mine in the Iron Ore Quadrangle in Minas Gerais state, Brazil. The mine produces 48 to 50 koz per annum, as part of the larger Cuiabá-Lamego Complex. This combined unit is AngloGold Ashanti’s largest gold producer in the Americas, contributing with 310 to 320 koz per annum.
The mine started production in 2009, utilising cut-and-fill mining methods.
A mining method change was
trialled in 2014, introducing open stope methods. The key benefits proposed from
this change are considered to be:
- improved safety by eliminating re-entry mining methods
- reduced mining costs/increased productivity from utilising bulk-mining
The results from the trial were encouraging, and open stoping participation expanded beyond a trial.
Production from open stope areas reached 180 000 t (40 per cent of total run-of-mine; ROM) in 2015. While the change in mining method resulted in higher production rates, it also introduced a critical issue in terms of stope recovery rate.
Average underbreak (unplanned loss of ore) in the larger
open stopes reached 21 per cent in 2015. To manage this ore loss, a project
targeting higher recovery was structured with three primary components:
- analyse current performance to define contributing factors (design process
gaps, operating practices)
- investigate corrective actions
- apply corrective actions and maximise team engagement to ensure changes
become standard practice.
Within six months of commencement, a range of contributing factors had been identified, and the majority of the associated corrective actions implemented, including increased team engagement to ensure changes were not ‘once off’ actions.
The outcomes show a clear reduction in underbreak (average ~12 per cent for 2016), with further improvement opportunities identified. The challenging target is now to achieve a further reduction to 10 per cent underbreak as the average for 2017. The results contributed 1400 oz and additional US$ 0.5 million to the cash generation profile for 2016.
Heberle, A, Freeman, C and Cota, R
F, 2017. Increasing stope recovery in an underground gold mine by using
effective analysis, corrective action and employee engagement processes, in
Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 117–122 (The
Australasian Institute of Mining and Metallurgy: Melbourne).