The Santa Rita Operation consists of a simple, low cost, open pit drill and blast, load and haul mining operation which feeds a conventional, low technology nickel sulphide concentration plant. Based on the current ore reserves estimate, the expected remaining mine life is approximately 14 years.
The operation is well located, close to key infrastructure, including power, water and transport. It is approximately 260km southwest of Salvador, the capital of Bahia in Brazil, approximately 6km from the town of Ipiaú , which supplies the majority of the operation's workers, and approximately 140km from Ilhéus, the deepwater port from which Mirabela exports its nickel concentrate.
Mirabela acquired the Santa Rita deposit in 2004, completed commissioning of the operation in October 2009, commenced production of nickel concentrate in November 2009 and entered commercial production in January 2010.
Since commencing operations, the mine has had a strong safety performance with a Lost Time Injuries Frequency Rate of 1.58 for 2014. This strong performance is testament to the high priority and commitment given to safety by the operational team. Health and safety training programmes remain ongoing and are aimed at continuous improvement.
The Santa Rita deposit comprises disseminated nickel and copper sulphide mineralisation with cobalt and platinum group element (PGE) credits. The deposit is up to 140m thick in places and averages 40m thick over a continuous strike length of more than 2km and 1km depth. Zones of thicker and more continuous ore are located in the north and south ends of the pit.
Mirabela produces a high quality nickel-copper-cobalt-PGE concentrate with metal content of approximately 20% and an average nickel content of approximately 13-15%. The concentrate is sold in bulk to overseas customers via the port at Ilheus, Bahia, Brazil.
In the second half of 2014 the company undertook a full review of the mine operation resulting in a new four year mine plan strategy commencing in 2015. Mirabela's 2015 mine plan focuses on streamlining operations and reducing production unit costs. The mine plan targets optimising near-term cash flows given the low and volatile nickel price environment. The mine plan has built-in flexibility and can be modified at the appropriate time when nickel prices demonstrate a sustained recovery.
Optimising near-term cash flows focused on improved productivity and lowering mining operating costs, which includes modifying the geometry of the pit to work on 10 metre benches with the ore being mined on 5 metre cuts. The newly optimized mine sequence will simplify mine operations and take advantage of shorter haulage distances to the primary crushing station and waste dump locations. A better understanding of process recoveries by rock type has also led to a review of the cut-off grade and stockpiling strategy used by the mine. The new mine sequencing has been developed as part of the 2015 plan.
Two new mine phases (Pit 6 and Pit 8) were designed to take into account the zones of thicker and more continuous ore in the north and south ends of the pit and to reduce stripping the entire strike length of the deposit in one phase. For the short-term, the first phase involves mining in the north pit (Pit 6) where the ore thickness is greater than in the central and the south pits. The first phase will provide feed to the plant for a six month period at an average grade of 0.50% total nickel. The second phase (Pit 8) will provide feed for 3.5 years with the ore quantity for the two phases sufficient for a four year production plan at an average strip ratio of 2.35:1. Starting in the first quarter of 2017, Mirabela will benefit from a low strip ratio given the mine design and it is anticipated that surplus capacity in the mining fleet will be deployed to commence stripping on the west wall in preparation for the subsequent phases of mining.
Layout of the Santa Rita Operations