Agne Ahlenius
General Manager
Aranzazu Mine, Aura Minerals
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View from the Top

Massive Expansion Plan Underway at Aranzazu,

Wed, 10/21/2015 - 09:31

Q: What condition was the Aranzazu mine in when it was acquired by Aura Minerals in 2008?

A: When Aura Minerals acquired the Aranzazu copper-goldsilver mine in Zacatecas in 2008, it was already a producing mine but it had to be put on care and maintenance in 2009. We found that the ore body had not been well investigated in the past so we used this chance to carry out better exploration. This went on for about a year while some upgrades were made to the plant, after which, production was restarted to reach the level it is at now. Aranzazu is located in a very interesting mining area, which has simply been badly explored. For example, Minera Tayahua, which is owned by Minera Frisco, operates on the other side of a mountain in the same geological zone. Our company sees huge potential in this area as, even by just considering our own investigations which have gone to a depth of around 300m, it is an enormous ore body. This gives us up to 15 years of production at an increased production level of 4,500 t/d. We know that the ore body plunges down even deeper but we have not yet performed full investigation and exploration. This makes it highly feasible for the operation to be viable for a much longer period of time than currently planned for.

Q: Aranzazu includes plans for both open-pit and underground mines. How has this affected the overall design of the mine site, and what operational challenges has this posed?

A: When production was restarted in 2010, a decision was made to temporarily run part of the production from an open pit. This is just until the underground mine is ready for increased production in 2014. The open pit will be finished by the end of 2014 when 100% of the production will come from underground mining. This decision was taken because of the ore body’s geometry. It is extremely deep and cannot be mined in an open pit due to the surrounding mountains, as well as the village of Concepcion del Oro where most of our workforce live.

Q: You plan to upgrade the mine’s mill from 2,600 to 4,500 t/d. When will this stage be completed and how will it improve operational processes at Aranzazu?

A: The process plant in Aranzazu is fairly simple as it takes care of crushing, grinding, milling, flotation, and filtering to produce a copper concentrate. We already have sufficient capacity in crushing, so we do not need major modifications in this area, but we do need an additional ball mill to boost our grinding and flotation capacity. These areas will mainly be upgraded outside the existing buildings so they do not impact our current production and capacity. By remaining at full production while we build the expansion, we will be able to optimize our cash flow and operational costs. Part of the expansion will also involve an arsenic roasting process, which is not a commonly used process in Mexico. This roaster treats the valuable copper concentrate in order to separate it from the arsenic. Our ore body is peculiar as it has a fairly high arsenic content, which will only increase in the future as we go deeper and encounter new ore bodies. Harnessing this roasting technology will therefore improve our long-term viability as the arsenic levels increase.

Q: What technologies and innovations is Aura Minerals investing in to maximize the efficiency of its operations at Aranzazu?

A: At Aranzazu, we plan to use paste backfilling technologies. We will be using 50% of the tailings, mixing them with cement, and injecting them into the underground mine to backfill the mined out voids. This has many positive effects, such as reducing the environmental footprint of the tailings dam on the surface, and allowing us to backfill the mined out stopes so we can safely extract almost 100% of the resources.

Q: What will be the priorities for Aranzazu’s development over the coming years?

A: Our objectives are straightforward. It is very important for us to complete the expansion from 2,600 to 4,500 t/d, which will generate sufficient cash flow to provide us with a base for steady, long-term strategic growth. Our plan is to reach the increased production level of 4,500 t/d by late 2015, which will mean we have fully tapped into the area’s huge exploration potential. We will then have the potential to increase the extraction of resources in the close vicinity of Concepcion del Oro. Parallel to this, we will continue looking for other projects, particularly those that are fairly close to beginning operations rather than pure greenfield projects.