Low cost zinc and lead production
CAML took 100% ownership of the Sasa underground zinc-lead mine in November 2017. The mine is located in north eastern North Macedonia, approximately 150km east of the capital city, Skopje, and 10km north of local town, Makedonska Kamenica.
The Sasa deposit was discovered during a period of exploration between 1954 and 1965. Trial mining commenced in 1965 and, in 1966, the mine commenced commercial production as a state-owned entity. The mine closed in 2002 and was placed into bankruptcy due to lack of funding. The Solway Investments Group subsequently purchased the mine, invested in new equipment and operations resumed in 2006. Solway Group later sold the mine to Fusion Capital and Orion Mine Finance Group in 2015.
Sasa lies within the Serbo-Macedonian Massif, which hosts a large number of lead and zinc deposits and extends through Serbia, North Macedonia, Bulgaria, eastern Greece and into Turkey. The mine’s Svinja Reka and Golema Reka deposits are located on the eastern flank of a copper molybdenum porphyry deposit at Osogovo. Mineralisation occurs as stratiform deposits hosted predominantly by schists and marbles at Svinja Reka and by gneisses at Golema Reka. Hydrothermal fluids and bedding parallel faulting are responsible for the metasomatism of the host sediments that produce the skarn and base metal mineralisation. The deposits are well defined lenses of lead zinc silver mineralisation, which dip at about 35 degrees and range in thickness from 2 metres to 30 metres.
YEAR SASA MINE LIFE
The following table shows recent Sasa mine and concentrate production for the past five years.
|Pb in concentrate||t||30,181||30,693||29,524||28,955||29,881||29,388||29,201|
|Zn in concentrate||t||23,182||23,522||23,476||22,515||21,585||22,532||23,369|
Sasa Mineral Resources and Ore Reserves, June 2020
|Mt||Pb %||Zn %||Ag g/t||Pb (kt)||Zn (kt)||Ag (koz)|
|Svinja Reka – Reserves|
|Svinja Reka – Resources|
|Golema Reka – Resources|
- Ore Reserve prepared by Sasa technical team as of June 2020, Scott Yelland (CAML COO) as Competent Person
- Svinja Reka Mineral Resource Estimate prepared by Sasa technical team as of June 2020, Jordan Angelov (Sasa Technical Services Manager) as Competent Person
- Golema Reka Mineral Resource Estimate prepared by SRK Consulting (UK) Ltd as of December 2018, Guy Dishaw, SRK Principal Consultant as Competent Person
- Mineral Resources are reported inclusive of that material used to derive the Ore Reserves
How we produce zinc and lead concentrates
Sasa is an underground zinc and lead mine that produces approximately 820,000 tonnes of ore each year. Accessed by adit, the Svinja Reka deposit is currently mined using a sub-level caving method, which utilises the geotechnical characteristics of the weak hanging wall to allow the rock to cave naturally into the void remaining after ore has been blasted.
Main haulage levels are at 80 metre intervals, with sub-levels every 7 metres. Ore drives are typically 3.5 metres by 3.5 metres. Ore is mined using a top down approach without backfill. Ore is drilled using single boom jumbos, blasted and then excavated with underground loaders.
From the second half of 2022 the Sasa team will transition to a new mining method, cut and fill stoping, with approximately 90% of ore being extracted using this method by 2024. The voids will then be backfilled with paste material containing tailings to provide support, rather than allowing the roof to cave as is the case with the current sub-level caving method.
Once blasted, 70% of the ore is then sent via ore passes to the 830m level where it is transported by rail wagons to the Golema Reka shaft for hoisting, and the remaining 30% is hauled to surface via the adit.
Once at surface, ore is then crushed in three stages. The milling circuit then involves two rod mills, followed by spiral classifiers and then two ball mills to ensure material is the appropriate size for liberation by flotation at approximately 74 microns.
The processing plant then operates both lead and zinc flotation processes, producing separate concentrates that are filter pressed to produce products containing 5-9% moisture. Silver is also produced and this reports to the lead concentrate. The lead concentrate contains c.73% lead and the zinc concentrate contains c.49% zinc. The concentrates are stored in two separate bays before being loaded into haulage trucks for sale to smelters.
Tailings from the Sasa processing plant are stored in storage facilities on site. With the commencement of cut and fill stoping approximately 45% of Svinja Reka’s life of mine tailings will be stored underground and as of the backfill. Then approximately 30% of tailings will be stored in the current Tailings Storage Facility 4. CAML is advancing studies with a view to dry stacking the remainder tailings and eliminating the future use of tailings dam facilities.
Life of Mine study
A Life of Mine study was commissioned in order to investigate the efficiency of operations at Sasa, including a review of the current sub-level caving mining method, and to determine recommendations that would optimise productivity.
The study recommended the transition from sub-level caving to cut and fill stoping, a more selective mining method, that will not only result in maximum recovery of mineral resources, but will also enable safer operating practices as well as longer-term improvements to tailings disposal. The recommendation has been approved by the Board and the transition to the new mining method will take effect in the second half of 2022, with approximately 90% of ore being extracted using this method by 2024. In order to move to cut and fill stoping and therefore ensure effective long-term operations for the life of the mine at Svinja Reka, several practical changes will be implemented at site.
Cut and fill stoping is a more selective mining method than sub-level caving, which is expected to achieve greater recovery of ore as well as reducing the dilution of ore with un-mineralised material. It is a bottom-up mining method involving drilling, blasting and mucking out of ore before filling voids.
The cut and fill mining method involves filling mined voids with a backfill paste material containing tailings to provide support, rather than allowing the roof to cave as is the case with the current sub-level caving method. In order to achieve this, a backfill plant will be constructed, along with associated reticulation pipework to transport this material underground. Tailings from the processing facilities will be sent to the backfill plant to be thickened and pressed to contain 80% solids, and then mixed with a slurry containing cement, fly ash and water to produce a paste of the appropriate consistency. This is then distributed underground to fill stopes.
Storage of tailings
Given that a major component of the backfill material will be tailings generated from the Sasa processing plant, it is estimated that approximately 45% of Svinja Reka’s life of mine tailings will be stored underground. Approximately 30% of tailings will be stored in the current TSF4, and CAML is advancing studies with a view to dry stacking the remainder and therefore eliminating the need to construct further tailings dams in the future. The Company is firmly committed to the environmental and socially responsible disposal of tailings for the long term.
Streaming agreement with Osisko Gold Royalties
Due to a long standing streaming agreement with Osisko Gold Royalties, CAML will receive approximately $5/oz for its silver production for the life of the Sasa mine.
TONNES OF ORE