Gibraltar

Overview

Gibraltar, Taseko Mines Limited 75% owned copper-molybdenum mine, is located near Williams Lake in central British Columbia, Canada. The open pit mine, covers approximately 109 square kilometers and consists of 251 mineral claims and 30 mining leases. The property hosts resources and reserves in seven separate mineralized zones which has supported mining for most of the past 30 years.

Mining began at Gibraltar in 1917. The current mine opened in 1972 and closed in 1998. In 1999 Taseko acquired the mine and resumed operations in 2004, when prices for copper and molybdenum rose. The mine is operated by Taseko and currently employs 418 people.

The mine site covers approximately 109 square kilometers and consists primarily of 251 mineral claims and 30 mining leases. There are seven separate mineralized zones. The pits are the Polyanna, PGE Connector, PGE Connector Additional, Granite Lake, and Granite Lake Additional. The pits occur within the Granite Mountain batholith in a broad zone of shearing and alteration. The Sawmill zone lies about 6 kilometres to the south, along the southern edge of the batholith, within a complex contact zone between the batholith and Cache Creek Group rocks.

Location

Gibraltar is in south central British Columbia, a region known as the Cariboo. The mine is 65 km north of Williams Lake and 600 km from Vancouver. There is good road access from Vancouver: Highway 97 branches off the Trans Canada Highway at Cache Creek, going north to Williams Lake. There is also an airport at Williams Lake.

Geology and Mineralization

The Triassic Granite Mountain batholith intruding the Permian Cache Creek Group hosts the mineralization. The Tonalite phase intrusive (other than Sawmill zone) is regionally sheared and altered and is associated with the emplacement of pyrite, chalcopyrite and molybdenum during a later stage of regional alteration. The Sawmill Zone was emplaced along the intrusive/ Cache Creek contact. Supergene alteration and enrichment of copper is important in the upper portions of the deposits.

The mine generally consists of seven separate mineralized zones. Six of these – Pollyanna, Granite Lake, Connector, Gibraltar East, Gibraltar West and Gibraltar West Extension – occur within the Granite Mountain batholith in a broad zone of shearing and alteration. A seventh copper mineralized body, the Sawmill zone, lies about 6 kilometres to the south, along the southern edge of the batholith, within a complex contact zone between the batholith and Cache Creek Group rocks.

DEPOSIT
The Pollyanna, Granite and Connector deposits have been referred to at the mine as porphyry ores due in part to their large size and diffuse nature of mineralization. In contrast, the Gibraltar Extension deposit was considered shear ore, and the Gibraltar East deposit as transitional between the two types consisting of a series of interconnected planar zones that form a large body of uniform grade. Exploration of the Pollyanna, Granite, Connector and Gibraltar East deposits has used well established features of these deposits such as the uniform southerly dip of the mineral zones and offsets by a series of northerly trending, generally steeply west dipping faults to guide hole placements.

MINERALIZATION
The Gibraltar Extension deposit is a shear-hosted orebody. Mineralization is structurally controlled, occurring as inclined, strongly chlorite, quartz, sericite altered pyrite-chalcopyrsite bearing quasi-planar zones of variable thickness hosted by early, low-angle, possibly thrust structures, directed to the northeast, and bounded by subvertical, post-mineral faults. Structural deformation, hydrothermal alteration and sulphide mineralization appear to be synchronous and inter-dependant and mineralization intensity appears to increase with stronger alteration and deformation. The relationship between structure, alteration and mineralization is a common theme in the other Gibraltar deposits, but is particularly prominent in the Gibraltar Extension deposit. Pyrite and chalcopyrite are the principal primary sulphide minerals in the deposit. Sulphide veinlets alternate with chlorite, sericite and quartz veinlets forming penetrative microstructures inside mineralized intervals grading at least 0.15% Cu. Chalcopyrite occurs predominantly as coarse grained segregations rather than fine grained uniformly distributed disseminations as in the other Gibraltar deposits where very fine disseminations form up to about 60% of the porphyry-type ores.

Mining & Operation

Gibraltar is a large-scale, 35,000 tonne per day open pit mine. Current mining operations are carried out utilizing conventional open pit mining equipment. The waste and ore are mined utilizing three 12¼” electric blast hole drills, four electric rope shovels, six 240 ton haul trucks and five 205 ton haul trucks. The main mining fleet is supported by a fleet of ancillary equipment including track and rubber tired dozers, motor graders and rubber tired loaders as well as sand and water trucks. Mine operations are conducted on 45 foot benches. A sulphide ore cut-off grade of 0.20% copper is applied for concentrator feed and a 0.10% acid soluble copper cut-off is used to define oxide ore economic for processing via dump leaching. Ore grading is performed based on assays received from blast hole drill cuttings and a practical minimum block width of 50 feet.

Under normal operations, it produces 80 Mlb of Cu and 700,000 lb of molybdenum annually. The company uses a froth flotation to extract the high-grade material and SX/EW to extract the low grade material

Processing

The sulphide ore is processed through a two stage crushing circuit consisting of an Allis-Chalmers 54x74 gyratory crusher followed by four parallel Allis-Chalmers 13x84 secondary crushers operating in closed circuit to produce a 1” minus feed for the grinding circuit. The grinding circuit consists of three parallel rod mill – ball mill circuits operated in closed circuit to produce a nominal 40% plus 65 mesh product to feed rougher flotation. Three parallel rougher flotation banks, one per grinding line, produce a combined rougher concentrate which is subsequently reground to 65% passing 325 mesh.

The SX/EW plant is designed to extract copper from the pregnant leach solutions (PLS) collected from the site’s leach dumps and heap leach pad.

Environment & Community

New regional landfill site on one of the mine's waste rock dumps. The public agreed that establishing such a facility at the mine site would be environmentally, socially and economically sustainable, and could be developed as a public private partnership. Under the agreement, Gibraltar would remain responsible for the waste rock and drainage below the landfill and the Cariboo Regional District would be responsible for the air space above the waste rock. The benefits of locating the landfill at the Gibraltar mine site are numerous: Located on industrial land, with no need to build roads and disturb new ground, environmental impact and additional cost of construction were eliminated. Large on-site mine equipment could build the landfill at half the cost. The landfill would compliment mine reclamation. The mine's extensive surface and groundwater monitoring system would also serve the landfill.