Lapa startup slated for mid-2009

Pre-production development at Agnico-Eagle’s LAPA MINE, 45 km west of Val d’Or, Que., is advancing toward startup in mid-2009. By the middle of May when CMJ visited the project, 2,300 m of development had been completed on three levels: 49, 77 and 101 (respectively 490, 770 and 1,010 m below surface). Despite fast-tracking development, the property’s history goes back over 70 years.

Exploration at Lapa has been on-again, off-again since the late 1930s. Underground drilling was carried out on the property between 1937 and 1943 by Lapa-Cadillac Gold Mines. Canadian Malartic Gold Mines intersected gold mineralization in the Pich Volcanic Group during its 1,200-m drill program in 1955. Breakwater Resources owned the property from 1981 to 1989, advancing an exploration ramp and conducting an underground drill program. Cambior Exploration Canada drilled the A zone and Contact zone in 1999, but the property remained in the hands of Breakwater.

Agnico-Eagle drilled three holes in the Contact zone during 2002, and the results were so promising (as much as 12.34 g/t Au over a true thickness of 5.0 m) that the company acquired the entire Lapa property from Breakwater in 2003 for $8.9 million plus royalty interests. Agnico-Eagle got busy on an underground exploration program that included a new shaft and development in 2004. New gold zones were unearthed, the price of gold headed toward the stratosphere, and two years later, the decision was made to take the project through to full production by early 2010.

At full production the US$165-million Lapa mine and mill will produce on average 125,000 oz of gold annually at a cash cost of approximately US$300/oz. The project has proven and probable reserves of 3.8 million tonnes (t) grading 8.87 g/t Au or 1.07 million contained ounces of gold. There are also 865,000 t of indicated resources grading 4.48 g/t Au and 759,000 t of inferred resources grading 8.96 g/t Au.

The high-grade, narrow-vein Lapa mine will be the second Agnico-Eagle gold mine with no cyanide and no tailings on site (following the Goldex mine)–another “green” mine made possible by the permitted cyanide use and tailings impoundment at the LaRonde mill 10 km to the west.

Geology of the Lapa deposit

The LaRonde and Lapa deposits are geologically similar, no surprise since both are located near the southern boundary of the Abitibi and Pontiac sub-provinces and are nearneighbours. The CLL fault zone, which passes east-west though the Lapa property, is marked by schists and mafic to ultramafic volcanic flows of the Pich Group up to about 300 m thick.

To the north of the Pich Group lie the Cadillac Group sedimentary rocks consisting of well-banded wacke, conglomerate and siltstone with intercalations of iron formation. The Pontiac Group sedimentary rocks that occur to the south of the Pich Group are similar to the Cadillac Group but do not contain conglomerate nor iron formation. Minor diabase dikes that strike northwest cut all of the rocks.

All of the known gold mineralization along the CLL fault zone is epigenetic vein-type, and is controlled by structure. It occurs in or immediately adjacent to the Pich Group rocks. Although gold mineralization also occurs throughout the Pich Group at Lapa, it is generally discontinuous and has low economic potential except for the Contact and the satellite zones.

The Lapa deposit comprises the Contact zone (generally at the contact between the Pich Group and the Cadillac Group sediments) and five satellite zones (within the Pich Group). The ore zones are made up of multiple quartz veins and veinlets, often smoky and anastomosing, within a sheared and altered envelope (with minor sulphides and visible gold).

Quartz veins and millimetre-sized veinlets that are parallel to the foliation account for 5-25% of the mineralization. Visible gold is common in the veins and veinlets but can also be found in the altered host rock. Sulphides account for 1-3% of the mineralization. The most common sulphides are (in order of decreasing importance) arsenopyrite, pyrite, pyrrhotite and stibnite. Graphite is also rarely observed as inclusions in smoky quartz veins.

The Contact zone is a tabular envelope oriented east-west and dipping 87 to the north, but with a south dip at depth. The economic portion of the zone has been traced from roughly 450 m below surface to below 1,500 m and is open at depth. It has an average strike length of 300 m and varies in thickness from 2.8 to 5.0 m.

The satellite zones (North, FW, Center, South 1 and South 2) are also steeply dipping and are oriented subparallel or slightly oblique to the Contact zone, with similar thicknesses.

Lapa mine

The Lapa mine has a 1,370-m-deep, 4.9-mdiam concrete-lined production shaft that was completed in October 2007.It is fitted with two 12-t bottom-dump skips with a small doubledeck cage slung under one and a counterweight under the other. Two automated 4.1 x 2.0-m-diam Nordberg double-drum hoists with 932-kW General Electric motors keep things moving.

Agnico-Eagle has a strategy of using used equipment appropriately, said mine manager Carol Plummer. For example, the headframe and shaft house that previously served the LaRonde shaft No. 1 have been moved to the Lapa property and refurbished. The hoist room was at the Victoria Creek project, and the compressors were purchased from the Louvicourt mine. The silo for the cement plant that is under construction at Lapa was moved from the Lac St-Jean region of Quebec. The mine offices consist of 20 modules that can be cheaply and easily moved at the end of the mine life.

Ventilation is a push-pull system. Fresh air is drawn down the shaft, circulated and exhausted up a 3.7-m-diam raise 80 m from the shaft collar. The vent raise is being bored by a crew from CMAC-Thyssen with a Robbins raise borer. Two fans currently move 2,800 m3/min, but the pair of new Alphair exhaust fans that will be installed in July will be able to handle a volume of 9,800 m3/min. Until the exhaust raise is ready, exhaust exits the mine up a 1.4-m-diam pipe in the shaft beside the manway. A second 2.4-m-diam raise is being excavated and will serve as an escapeway.

Sixty-five percent of the ore is found in 3.5-m-wide veins in the Contact zone. The other 35% occurs in satellite lenses. The orebody lends itself to longitudinal mining with sublevels established at 30-m intervals. An internal ramp connects the various mining levels, and the garage and services are being established on 77 level.

Stopes will be cut 12-m long with a raisebored slot in the first stope. When the stope is empty, Styrofoam blocks 60 mm x 120 mm and 2.4-m long will be installed along the exposed side wall of the open stope. Once the empty stope is backfilled with cemented rock fill, the adjacent stope can be drilled. The Styrofoam acts as a slot allowing the rock mass to expand when the second stope is blasted, saving the time and money otherwise needed to excavate a conventional slot.

The engineers have worked out three horizontal ore blocks and a number of vertical blocks. They intend that six stopes be active at a time. That strategy not only allows multiple working faces but also maintains the stress front.

Haulage is being established on 77 and 125 levels, with a grizzly and rock-breaker station on each. Rock-breaking and loading will be automated and monitored from surface.

Agnico-Eagle’s chosen fleet of underground production equipment has been ordered. There are two Atlas Copco jumbos (one-and two-boom),Atlas Copco 710 load-haul-dumpers and Atlas Copco 20- t haulage trucks. Sandvik is supplying Getman scissor lifts, and a McLean Engineering hydraulic boom truck is on its way.

Meanwhile the Agnico-Eagle development crews supplemented by crews from Dumas Mining are pushing toward the development goals in 2010. An underground dri
lling crew from Orbit/Garant is diamond drilling the lower portions of the orebody where the mineralization remains open. Further exploration will be focused on the east side where economic values were intercepted during the surface exploration program.

The Lapa mine will begin commercial production in mid-2009, reaching full production (540,000 t/y) in early 2010. The project has a short life, only five years at full production. The savings made possible by building the mill on the permitted LaRonde site, along with the commitment of employees both at the mine and in the concentrator make the recovery of this small resource feasible.

Off site milling

Each day 1,500 t of ore from the Lapa mine will be trucked 14 km west to the LaRonde mill where new circuits have been built to treat it. Production will begin in 2009 at 1,050 t/d, ramping up to 1,500 t/d in 2010. That means that the footprint of the mine is as small as possible–no tailings pond, no acid-generating waste, no processing plant, and no cyanide on the Lapa site. There is, however, a small minewater settling pond on site. Using the permitted facilities at the LaRonde site will undoubtedly cut permitting and development time as well as major costs.

The decision to mill at LaRonde has other benefits. The complete processing team including health and safety members is in place. There are laboratory services, plant utilities (electrical, air and water), a refinery and a tailings impoundment, in addition to permitted reagent (lime, cyanide, lead nitrate and flocculent) storage. Moreover, the existing crusher, ball mill installation, a gravity gold room, primary cyclones and some pumps and pump boxes were re-used.

Marcel Beaudoin is Agnico’s superintendent in charge of construction, and leading the team for the mill construction. Assistant mill superintendent Paul Blatter gave CMJ a tour of the Lapa mill construction site in mid-May, describing it as a “dark brownfield project”. The Genivar Group is doing the engineering out of Rouyn-Noranda, Que.

The processing can be summarized as: Once the ore arrives by truck from Lapa, it is crushed to 150 mm with the 900-mm x 1,220- mm jaw crusher that was moved from its old installation into a more optimal location to feed the mill. The crushed ore then reports to an existing 1,000-t silo that was modified to accommodate new feeders and services.

Fine ore feeds a new 5.5-m-diam, 2,200- kW SAG mill with a variable speed drive. The nameplate identifies it as a Farnell-Thompson mill. It is an example of Agnico- Eagle’s collaborative approach. Farnell- Thompson engineered the mill and sourced the parts. When the pieces arrive at the plant, Agnico-Eagle crews will assemble the mill.

Slurry from the SAG mill is cycloned and then pumped approximately 110 m east into the existing LaRonde mill for a regrind in one of the re-commissioned 750-kW ball mill circuits. Free gold, up to 35%, is extracted via an existing and re-commissioned gravity circuit. The total gold recovery expected from Lapa ore is 85-87%.

The final ground product is then pumped back into the new complex for thickening and leaching in a new carbon-in-leach circuit. Loaded gold is then stripped in a new conventional carbon strip circuit. The circuit, provided by Como Engineering of Perth, is engineered and built according to North American and Agnico specifications (electrical, mechanical, etc.), built and completely pre-commissioned in Australia prior to an ocean voyage and re-installation at LaRonde.

Both concentrates (gravity and elution sludge) are sent to the LaRonde refinery for dor production. The final tails product is then pumped into the existing LaRonde tailings impoundment facility.

Lapa’s footprint

The opportunity to treat Lapa ore at LaRonde fits neatly into a philosophy of keeping the project’s ecological footprint small, mine manager Plummer told CMJ.

The strategy is evident in many practices at the mine site. Awareness is the key. Spill kits have been distributed underground, recycling is practised both inside (paper, plastic, glass and cans) and outside (wood, steel, copper, etc.).All water is 100% recycled from an old pit and the settling pond. Domestic water is treated in a “bionest”with naturally occurring bacteria, hence there are no antibacterial soaps used at Lapa. With the help of Hydro-Quebec, an energy-saving variable-drive compressor will be installed late in 2008.

With emphasis on personal safety, regulations and budget, Lapa looks to be a very timely project, indeed.