Magnum Mining and Exploration (ASX: MGU) has completed a short term mining schedule for its 100% owned Buena Vista Iron Project in Nevada, USA, with the purpose to investigate a short term expedited mine development plan opportunity.
A scoping study for the Buena Vista Iron Project was based on an annual production rate of 1.6Mt per year of high-grade magnetite concentrate. A fast start-up option is under consideration. The option may deliver earlier cash flows based on accessing higher grade portions of the existing resource. As part of that review, a mine schedule has been constructed to enable the production of 800,000t of high-grade magnetite concentrate per year. Industry leader SRK Consulting out of Reno, Nevada, USA were contracted to undertake this work.
The mine schedule was developed using the following parameters:
• Supply five years of mill feed at a cutoff grade of 10% Fe
• Pit to access an average 2.5Mtpa of ore
• Maximize ore grade while minimizing the strip ratio
• Optimized pit should not sterilize any resource
• Pit slopes are to be conservative at 43 degrees in the absence of sufficient geotechnical data
Additionally, to find a balance between highest grade and lowest strip ratio, SRK generated a series of nested pit shells using the pseudo flow algorithm with simplified economic inputs. To generate the shells, the price input was slowly increased, and larger shells were produced. SRK evaluated these shells against the internal cutoff for that shell.
A starter pit was added (pit 1) to the optimized pit 2 to allow higher grade material to be extracted earlier in the schedule. The two pit phase solids were divided into benches and loaded into Hexagon’s MinePlan Schedule Optimizer™. A monthly mine plan was generated based on bench material quantities. Linear optimization was utilized to balance ore and waste while shifting grade forward in the schedule as much as possible while maintaining a practical mining sequence.
The company is now investigating to determine the impact of feeding ore from the resulting low-grade stockpile into the mill during periods of high-grade ore production. The aim will be to smooth out ore feed grade to improve the mill’s performance.
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