Minbos holds a 50% interest in the Cabinda Phosphate Project, which incorporates an approximate 2000km² exploration permit covering all the known phosphate occurrences in the Cabinda Province, in the Republic of Angola. The remaining 50% is held by private company, Petril Phosphates Limited (Petril), which Minbos is proposing to merge with.
The Project contains one development project – Cacata and five advanced exploration projects; Mongo Tando, Chibuete, Ueca, Chivovo and Cambota.
Importantly, all of these projects lie within 50km of the coast and within 0.5km of the established road infrastructure providing an excellent economic basis for the Project.
The Project consists of sediments from the cretaceous and tertiary periods deposited in a large basin situated in the southern part of the Republic of the Congo, north western part of Angola and the western part of the Democratic Republic of the Congo.
Utilizing historical drill data, as well as results from Minbos’ drilling program, the Company has delineated a total resource of 391.3Mt @ 9.2% P2O5.
Minbos’ focus is the development of the high grade Cacata Project. The Company has completed a Scoping Study on Cacata, which produced positive results. Following this, a Bankable Feasibility Study is currently underway, and will be completed in 2017.
The BFS is based on the JORC high grade indicated resource of the Central portion of the Cacata ore body that demonstrate the robust nature of the project.
The BFS scope of works has been divided into two stages. Stage 1 is the completion a Trade-Off study to select the beneficiation route that will optimise the whole of resource outcome for the Cacata deposit. The Trade-Off study will compare the following 800,000tpa production scenarios:
Stage 1 is expected to be completed Quarter 2-2017.
As part of Stage 1, GMining Services Limited (GMining Services) has commenced work on the mine optimisation for each beneficiation route to determine the tonnes and grade that are available for the respective flowsheets to produce the target product specifications. This is an iterative process but it is expected the target head grades will be 30.5% – 31.5% P2O5 for dry beneficiation and 29 %- 30% P2O5. The available tonnage for each beneficiation route will be fed into the Trade-Off-Study comparison.
GMining Services has prepared an infill drill program for Cacata that is designed to increase the Mineral Resource confidence classification and to support the BFS reserve estimate. It will also provide the necessary data to design the ongoing grade control drilling regime for the mining operation. It is estimated that a program of around 3,000 to 4,000 metres will be sufficient to meet these objectives. In addition, the drilling program has been designed to satisfy geotechnical and hydrological drilling requirements.
Bulk samples have been tested by two equipment suppliers in the USA for beneficiation by drying and sizing. Another bulk sample was tested by Mintek in South Africa for beneficiation by wet scrubbing and screening.
The testwork results for both streams have been very encouraging and initial quotes for major equipment items have been provided to Ausenco Limited (Ausenco) who will prepare a comparison of the beneficiation alternatives for presentation to the JV partners.
Both equipment suppliers were provided a high grade sample grading 34% P2O5 and a medium grade sample with a higher clay content grading 30% P2O5. The equipment suppliers elected to size the material through roll crushers before drying the material and passing it through an air classifier to remove particles below fine dust to meet shipping requirements.
Both suppliers were able to beneficiate the samples to 33.5%-34.5% P2O5 which is much better than expected. The flowsheets were particularly successful at upgrading the higher clay samples. The testwork showed that P2O5 recoveries of 90%-95% are achievable and the final number will be determined in conjunction with the mine optimisation study.
Major equipment lists and quotes have been provided by the equipment suppliers and Ausenco is preparing a cost performance comparison of the two process flowsheets.
Mintek was provided 7 individual bulk samples grading between 28%-31% P2O5 with an average grade of 29.9% P2O5. The testwork involved sizing through a roll crusher, wet scrubbing, and wet screening to size the product between 106 microns and 12mm. The tests all achieved a recovery of 95% or better and the average product grade was 31.5% P2O5.
It is expected that the final run of mine (ROM) head grade supplied to the wet beneficiation will be a little lower than the testwork average. As a result, the recovery will also be lower than the testwork results in order to maintain the same average product grade. The final numbers will be determined in conjunction with the mine optimisation study.
As part of the testwork, it was determined that the fine discards would require thickening before disposal in a tailings dam. Ausenco has already prepared a Wet Beneficiation equipment list and is obtaining costings for the plant. Golder has prepared options and costings for the tailings dam which will be included in the Trade off Study.
Quotations from local contractors have been sought for the road haulage of rock phosphate product from the mine site to Porto de Caio, a distance of 60km on well-formed bitumen roads. An internal estimate for an owner operator costing has been completed to evaluate the contractor proposals and resulted in a tariff that will be used in the Trade-Off-Study.
Ausenco has completed its evaluation of Porto de Caio and concluded that a rotating container system offers the most economic and flexible solution for Cacata. Porto de Caio continue to target availability for shipping before the end of 2017.
Engineers from Golder Associates have completed and costed alternative tailings impoundment designs for the Wet Beneficiation processing option. In addition, Golder’s have designed geotechnical and hydrogeological drilling for the BFS which will be incorporated into the infill drilling program.