Theta Gold Mines Ltd (ASX:TGM) will extend the Definitive Feasibility Study (DFS) for the TGME Underground Project in South Africa by incorporating the Rietfontein Mine.
This follows encouraging progress with the Rietfontein Mine Pre-Feasibility Study (PFS) which provides the company with adequate confidence to add it to the DFS.
With initial positive results, the Rietfontein PFS is nearing completion although further test work is required to confirm the processing recovery which has been conservatively assumed at 80%.
“Pleased with initial results”
The PFS and Underground DFS will run in parallel with both expected to be finalised in the second quarter of 2022.
Chairman Bill Guy said, “The board is pleased with initial results from the Rietfontein PFS and has decided to add Rietfontein to the TGME Underground Definitive Feasibility Study.
“It is expected that the addition will increase the production profile and mine life, along with further improving project economics.”
Adit entrances and surface footprint at Rietfontein Mine.
“Rietfontein high-grade ore was successfully mined up to 1945 using the shrinkage stoping method, producing 65,000 ounces of gold from 227,000 tons of ore, recovering more than 8 g/t,” Guy said.
“This method was also chosen for the PFS due to the proven methodology and relatively low ore dilution. The Rietfontein development will take place within the existing historical footprint, with minimal new surface disturbance.
“All workstreams for the Rietfontein PFS were completed, except for the metallurgical test-work, due to backlogs currently experienced globally within labs.
“The Definitive Feasibility Study has been running alongside the Rietfontein PFS and solid progress has been made by the team.”
TGME Underground (UG) Project will now include Rietfontein as well as the Beta, Frankfort and CDM mines.
Confidence in PFS
The Rietfontein PFS confirmed the following production target at the assumed recovery factor, subject to favourable processing test-work results:
- 1.334 million ore tonnes which consist of 479,000 tonnes of indicated resources and 855,000 tonnes of inferred resources;
- Average planned dilution was calculated over a 90 centimetre stope width where the dilution considered an overbreak into waste of 10 centimetres on either side of the reef contact;
- Delivered ore grade of approximately 6.82 g/t gold;
- 293,000 ounces produced, including 107,000 ounces delivered indicated resources and 186,000 ounces delivered inferred resources; and
- LoM of approximately 7.6 years at 180,000 tonnes per annum production rate.
The PFS requires validation from metallurgical test-work that is still in progress. Due to the global backlog experienced in laboratories, the metallurgical results are expected to be available in Q2 of 2022.
Underground sampling at Rietfontein Mine.
Rietfontein mine, with a mine delivered grade of 6.82 g/t, is the highest grade of the four mines incorporated in the project. As part of the DFS, the option of incorporating Rietfontein production earlier, as well as expanding throughput capacity, is being considered.
Further test-work
A current limitation to the Rietfontein study is that further metallurgical test-work is required. A sampling campaign is underway, from which more representable test-work can be done on the mine’s ore.
For the PFS a metallurgical recovery factor of 80% was applied to Rietfontein, despite much higher recoveries achieved historically. The proven results will, therefore, be incorporated in the DFS, and it was decided not to declare a reserve for Rietfontein until further test-work is concluded.
Strong economics
Theta Gold continues to demonstrate strong project economics for what it believes to be only a small portion of the underground resource.
The company will continue to build up its mining reserves during the next year by progressing Rietfontein and other mines through to DFS level.
TGM remains focused on its target of reaching 160,000 ounces per annum within five years from a multi-mine development program.