Norlartic

Norlartic


Phase: Exploration
Mine Type: Pit, Underground

Tags: actinolite albitization andesite archean basalt calcite carbonatization chlorite diorite dyke granodiorite greenstone belt komatite stockwork

Gold Map

Canada, province of Quebec. The deposit is located in the western portion of the province, about midway between the towns of Val-d’Or and Malartic.

Located on the north side of Highway 117, approximately 15 km northwest of Val-d’Or, Quebec and immediately east of Canadian Malartic Partnership’s Camflo property. The project is accessible by the Gervais Road, a well-maintained all-weather gravel road running north from Highway 117. It provides access to the historic Norlartic, Kierens, and Marban mines. The Camflo road provides access to the western part of the project area. Winter access for snowmobiles and all-terrain vehicles is provided by trails and winter roads.

History:

Estimated historical gold production: Norlartic Mines - 1959-1966; Aur Resources - 1990-1992. Total: 1544 kt ore, Au grade - 4.2 g/t, Au ounces*1000 - 209.

Exploration:

Discovered in 1943–1944, the Norlartic Main zone was developed in 1946 through 1948, when Reserves were estimated at 544,320 tonnes grading 5.83 g/t Aug (102,000 ounces) in the Main zone above the 152-m level. In the early 1950s, the North Zone was discovered 365 m north of the Norlartic shaft.

Additional underground drilling led to the calculation of Reserves totaling 566,093 tonnes grading 6.51 g/t Au (118,560 ounces) in the Main zone west of the shaft, in addition to 90,000 tonnes grading 25.37 g/t Au in the North Zone. Drilling west of the shaft and below the 305-m level in 1959 added 108,864 tonnes at 3.77 g/t Au (13,200 ounces) to the Reserves.

Following drilling by Brominco in 1980–1981 on the Main zone, primarily in an untested area east of the shaft and above the 152-m level, Reserves were estimated in the Main zone at 780,192 tonnes grading 4.46 g/t Au (111,800 ounces) above the 152-m level.

Regional geology: Abitibi greenstone belt

Abitibi greenstone belt of the Superior province of the Canadian Shield. The area consists mostly of felsic to mafic volcanic rocks of Archean age together with related dioritic sills which are concordant to the regional rock formations. These volcanic and intrusive rocks have generally been metamorphosed to the greenschist facies.

The Superior Province is the largest exposed Archean craton in the world and hosts several world class gold deposits. It has yielded nearly 300 million ounces of gold from hundreds of deposits since the beginning of the twentieth century. One prominent characteristic of all significant gold deposits in the Superior Province is their occurrence within or immediately adjacent to greenstone belts. Another characteristic is their occurrence within major tectonic zones which comprise a series of shear zones (Colvine et al., 1988). The Superior Province is divided into four major subprovince types (Card and Ciesielski, 1986): volcano-plutonic, plutonic, metasedimentary, and high metamorphic grade gneiss. The boundaries of these subprovinces are either major dextral, transcurrent, east-striking faults, or zones of structural and metamorphic transition.

The greenstone belts which host the gold deposits occur as east-north-easterly trending ribbon domains in the volcano-plutonic terrains. They typically consist of mafic to ultramafic and felsic metavolcanic …

Read more →

Local geology:

See description at Marban deposit.

Deposit geology:

Located in the northern part of the west-north-west striking, north-dipping shear zones related to the Norbenite shear. The mineralization is related to a swarm of mafic to intermediate sills and dykes that intrude the shear zones (Lefrançois, 2005). The Norbenite shear is comprised of highly altered and deformed units of ultramafic volcanics and mafic to intermediate dykes. These units tend to be discontinuous due to the effects of superimposed shearing and drag folding and are thereafter cut by relatively undeform felsic dykes. The shear zone ranges from 45–90 m in width and is approximately conformable with encompassing hanging wall and footwall ultramafic units. The different lithological units present within the Norbenite deformation zone were well described by Stuart and Martin (1986). Some of the rock names have been modified in terms of new interpretations, but the descriptions are still accurate.

The mafic rocks, previously interpreted as volcanics and later as mafic dykes, make up 20–30% of the mineralized horizons and may occur anywhere within the zone. Thicknesses of individual units vary from a few centimetres to tens of metres. These rocks may be either relatively unaltered or intensely altered by albitization and carbonatization.

Relatively unaltered mafics are medium to dark green, non-magnetic, fine-grained, and massive to moderately foliated. Abundant fine-grained chlorite and carbonate are common. The altered mafic rocks are a distinct sub-unit representing up to 30% of the mafic unit. Those rocks are characterized by intense albitization, carbonatization, a quartz and quartz-carbonate stockwork is related to pyrite dissemination and generally contain economic gold mineralization. The matrix of the host rock within these altered zones is dark grey-green, fine grained, and probably recrystallized.

The komatiite makes up approximately 50% of the mineralized horizons, occurring in units varying from less than 1 metre to over 30 m in thickness. These rocks are typically blue-grey or green, have a soapy texture, and are very highly schistose and incompetent. They are composed of 50–70% fine-grained talc and chlorite, with 30–50% calcite and magnesite. The carbonates occur as greenish-white disjointed veins up to one centimetre wide that have a characteristic preferred orientation parallel to a well-developed, and commonly folded, schistosity.

The komatiites typically contain 1–2% medium to coarse-grained disseminated euhedral pyrite. Gold appears to be erratically distributed within this unit. The blue-grey komatiites are moderately to strongly magnetic and are the altered and deformed equivalents of the hanging wall and footwall komatiites. The green facies are non-magnetic, but their origin is probably similar to that of the blue-grey units, the green colour being due to the presence of abundant magnesian chlorite.

The intermediate dykes generally make up between 20% and 30% of the mineralized horizons and are an important host for mineralization in the Kierens and Norlartic areas. They range in thickness from a few centimetres to tens of metres, although rarely exceed 10 m, and are oriented parallel to the principal schistosity.

The intermediate dykes are typically medium to pale grey, rarely reddish grey (hematite staining), fine-grained to aphanitic, and have a massive to weakly foliated texture. They are usually strongly albitized and variably carbonatized, with primary textures often obliterated. In some cases, apparent recrystallization has taken place, which produces a medium- to coarse- grained, allotriomorphic, granular rock composed almost entirely of carbonate. The dykes also commonly contain 5–15% randomly oriented carbonate and quartz-carbonate veins.

The intermediate dykes usually contain between 2 and 5% fine-grained disseminated pyrite and can also contain significant associated gold values. In general, gold only occurs in trace amounts where the dykes are relatively homogenous, weakly or moderately altered, and contain fine disseminated pyrite, but the dykes host more important mineralization where they are strongly altered and are cut by numerous quartz-carbonate veins.

The mafic and intermediate dykes related associated with the Norlartic and Kierens mineralization are mainly calc-alkaline dykes that stands out of the tholeiitic nature of the Jacola Formation.

Geologic Plan View of the Norlartic Pits Area

Geologic Cross-section of the Norlartic Pits Area

Mineralization:

The Norlartic deposit can be trace over a strike length of 800m down to a vertical depth of 800m. Gold was mined from two principal zones: the Main Zone and the Actinolite Zone, which are both now referred to as the Norlartic deposit. These zones are hosted by the Norbenite shear. The Main zone consists of a 5- to 15-metre-wide intermediate sill or dyke that
occurs within a large, sheared envelope of mafic rocks in the core of the Norbenite shear (Sauvé et al., 1993). Above the 500 level of the Norlartic mine, the main sill seems to change into a swarm of smaller dykes in ‘horse tail’ style. Gold is usually directly associated with the intrusion(s). The intermediate and mafic intrusions in the Norlartic zone have been strongly albitized and pyritized and have undergone intense brittle fracturing and quartz-carbonate-pyrite vein injection. Economic gold concentrations are found in quartz-calcite-pyrite vein stockworks that occur in closely spaced tabular intermediate intrusions. Hosting sheared komatiite also contain disseminated pyrite and are associated with gold, creating a wide auriferous envelope. On the east side of the historical shaft, the main target was the Actinolite Zone, where similar mineralization is hosted by a set of dioritic dykes in the hanging wall of the Main Zone. The higher percentage of actinolite in the ultramafic rocks hosting these mineralized dioritic dykes gave the zone’s name. The Norlartic mineralized zones were defined as three northwest-trending planar conformable with the Norbenite deformation corridor. A 0.3 g/t Au cut-off grade was used for the in-pit material while the cut-off for the under pit was raised to 2.0 g/t Au. A west-southwest planar structural component seems to intersect the zones in the old mine sector and while it doesn’t seem to displace the zone, the structure carries some continuous mineralisation, so a fourth zone was created to follow this structure.

Deposit types:

See description at Marban deposit.

Note:

For MRE effective date: 27 February 2022:

Mineral Resources (Feb. 27, 2022)

Class Ore (ktonnes) Au grade (g/t) Au (kg) Au (oz * 1000)
Indicated 15092.00 1.26 19047.82 614.00
Inferred 1250.00 1.70 2128.08 69.00

Source: