Louise Lake copper-molybdenum-gold-arsenic deposit, Smithers, Omineca Mining Division, British Columbia, Canadai

Regional Level Types
Louise Lake copper-molybdenum-gold-arsenic deposit	Deposit
Smithers	Town
Omineca Mining Division	Mining Division
British Columbia	Province
Canada	Country

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The Louise Lake copper-molybdenum-gold-arsenic deposit is located immediately west of Louise Lake, about 34 kilometres west-northwest of Smithers, British Columbia, in the Omineca Mining Division.

There is an extended description of the property on the British Columbia “Minfile” site, current to 2022, focusing largely on exploration history, to which interested readers are referred. Relevant portions pertaining to geology are quoted below:
“The Louise Lake property is predominantly underlain by interbedded sediments and volcanic rocks. A major 060 degree trending fault system runs through Coal Creek and along the north shore of Louise Lake. Conglomerates, greywackes, shales and volcaniclastics of the Lower-Upper Cretaceous Skeena Group are present on the north side of the fault; south of the fault are Middle-Upper Jurassic Ashman Formation shale, sandstone and conglomerate, and Upper Jurassic Netalzul Formation basalts, andesite tuffs and flows, both of the Jurassic-Lower Cretaceous Bowser Lake Group.

Locally, an intensely altered Eocene feldspar porphyry plug intrudes Skeena Group sediments adjacent to the major 060-degree trending fault. Petrographic studies of the altered feldspar porphyry indicate that its original composition was quartz monzonite.
Argillization, sericitization and silicification are the main alteration phases evident in the intrusive resulting in three distinct zones. These grade from a highly silicified central stockwork zone through an intermediate zone of moderate clay alteration and silicification, to a peripheral zone with an extremely high degree of kaolinization and moderate silicification.
Pyrite occurs in all alteration zones and varies from 1 to 10 per cent. The zones also host a stockwork of quartz-pyrite veinlets (2 to 20 millimetres wide) that contain minor amounts of chalcopyrite and molybdenite, with assays of up to 0.8 gram per tonne gold (Assessment Report 18971 [Klassen, 1989]). There are three preferred orientations of the stockwork development: 340 degrees, 010 degrees and 060 degrees.”

Giles Peatfield comments:
This is a somewhat unusual porphyry copper deposit for the region, as much of the copper content appears to be contained in the arsenic-bearing species tennantite and enargite (see comments in the minerals reported section). The deposit is included in the compilation by Singer, et al. (2008), who apparently derived their information from Hanson and Klassen (1995).
There does not appear to have been a radiometric age determined for the Louise Lake intrusive rocks. Hanson and Klassen (1995) refer to these rocks as belonging to the “Eocene Nanika” suite of intrusives. Carter (1981) reported dates for several porphyry deposits associated with this suite in the general region, with ages ranging from 49.5±3 m.y. [Ma] to 56.2±2.3 m.y.
There have been a number of resource estimates reported for the Louise Lake deposit. Hanson (1992) reported that Equity Silver Mines Limited had estimated that “This zone contains an estimated resource of 50 million tonnes grading 0.3% copper and 0.3 grams per tonne gold with some payable molybdenum.” at a cut off of 0.2% copper. This estimate would certainly not meet current NI [Canadian Regulatory National Instrument] 43-101 standards. Subsequently, Schultz (2008) reported that SRK Consulting (Canada) Inc. calculated an NI 43-101 compliant resource, calculated at a 0.25% CuEq [for details see Schultz’ report], of an Indicated Resource of 6 million tonnes grading 0.214% Cu, 0.006% Mo, 0.20 g/t [gram per tonne] Au and 0.98 g/t Ag, with an additional 141 million tonnes grading 0.234 % Cu, 0.009 % Mo, 0.23 g/t Au and 0.94 g/t Ag. Unfortunately, the SRK report does not seem to be readily available.

Giles Peatfield comments on the minerals reported:
Slightly fewer than half of the minerals listed above were reported in the Hanson and Klassen (1995) paper in CIM Special Volume 46. The remaining ones were reported in a large number of other references. Some should be regarded as tentative. There appears to have been limited detailed examinations; where such data are available, they will be noted in the comments following:
Apatite: Harris (1983) reported that “Apatite forms small disseminated grains.” as traces in what he described as “Dacite-andesite (Intrusive?).” Note that all identifications by Harris were by microscopy, on polished thin sections.
Arsenopyrite: Hanson (1992) noted arsenopyrite in the logs for two diamond drill holes: in the first case in veins with sphalerite, pyrite and chalcopyrite; in the second case in veinlets with molybdenite. These are field identifications. See also comment below for galena.
Bornite: Carter (1970) reported bornite as a less common copper mineral. Hanson and Klassen (1995) reported bornite as a minor coating, on what mineral was not stated. They further commented that [its] “. . . fine-grained nature required X-ray diffraction techniques for positive identification (E. Wosniak, unpub., 1969)”. It is not fully clear here whether they meant that the X-ray work had been done, or that it would be necessary. Hanson and Klassen (1995) believed the bornite to be supergene. In any event, it seems that bornite is not a common mineral here.
Calcite?: Harris (1983) described “carbonate” in altered rocks, but gave no specific identification. One assumes calcite, but this is tentative. None of the other workers referenced mentioned calcite.
Chalcocite: The same comments apply here as for bornite – see above.
Chalcopyrite: This is common, and reported by all workers except Simpson (1969), who was reporting on only two specimens of altered rock.
Chlorite group: Harris (1983) and Schultz (2007) both reported “chlorite” but gave no specific data.
Covellite?: Carter (1970) reported that “A covellite tarnish on tennantite is common.” He gave no detailed information, and no other worker has reported covellite; I would regard it as tentative.
Dumortierite? Harris (1983), describing a polished thin section of an “altered tuff”, reported that “Locally there are clusters of tiny, high-relief, colourless needles (? dumortierite) and patches of (?) topaz.” I would regard both minerals as tentative at this stage.
Enargite: Carter (1994) reported that “A well-mineralized sample from drill hole C-18 . . . was also found [he did not say by whom] to contain some enargite, . . . .” Hanson and Klassen (1995) wrote that “Tennantite and to a lesser extent chalcopyrite, enargite (R. Kirkham, pers. comm. 1994) and molybdenite are the minerals of possible economic interest.” Dr. R. V. (Rod) Kirkham (“Dr. Copper”) was with the Geological Survey of Canada and may well have been the source of Carter’s (1994) information. Schultz (2007, 2008) also mentioned enargite.
Feldspar group: Chamberlain (1969) reported plagioclase in thin section. Harris (1983) simply reported plagioclase. Hanson and Klassen (1995) simply reported feldspar. None of these workers gave more details.
Galena: Hanson (1992), describing the Lake Zone, wrote that “The volcanics and high level intrusives display weak quartz-sericite alteration and variable amounts of pyrite, sphalerite, chalcopyrite, galena, and arsenopyrite mineralization in the form of small veins, veinlets, microveins and patches.”
Graphite: Chamberlain (1969) reported, describing the sulfide minerals in sample L.G.-1 (Section 112), that “A single grain of graphite was observed.”
Hematite: Hanson (1992) noted numerous occurrences of “bright red hematite”, generally in veinlets.
Ilmenite: Chamberlain (1969) reported, describing the sulfide minerals in sample L.G.-1 (Section 112), that “Rare ilmenite laths were observed in pyrite grains . . . .”
Kaolinite: Harris (1983) noted that the feldspars in his polished thin sections were generally kaolinized. Hanson and Klassen (1995) noted, describing alteration zoning, that “Both [the inner zones] are surrounded by a peripheral argillic zone of strong kaolinization and weak quartz-pyrite veining.”
Limonite: Carter (1970) described “intense iron staining”, which one assumes was limonite.
Malachite: Schultz (2007) reported traces of malachite. Although certainly to be expected, the mineral was not reported by other workers.
Marcasite: Carter (1970) noted that, with pyrite, marcasite was the most common sulfide mineral. Harris (1983) described marcasite in polished thin sections, in one case writing that the sulfides “. . . consist of anhedral pyrite, often with intergrown marcasite (sometimes in rounded colloform masses); . . . .”
Mica group: Essentially all the referenced workers described sericite, as an alteration of feldspars.
Molybdenite: This is a common mineral at Louise Lake. Harris (1983), describing a polished thin section of “altered tuff”, wrote that “Molybdenite is a prominent constituent, disseminated throughout as stubby grains, 0.2 - 0.8mm. These are usually discrete but occasionally in simple intergrowth with tetrahedrite.” Hanson (1992) describing a drill hole in the Main Zone, wrote that “The altered sediments? and feldspar porphyry are variably mineralized with pyrite, tennantite, chalcopyrite, and molybdenite occurring as disseminations, and in microveins, veinlets and veins with quartz.”
Pyrite: Pyrite is ubiquitous at Louise Lake, reported by all workers.
Pyroxene group: Harris (1983), describing a polished thin section of “altered porphyritic dacite”, wrote that “Patches of remnant augite occasionally survive in some of the carbonate-chlorite pseudomorphs.”
Pyrrhotite: Chamberlain (1969) wrote that “Pyrrhotite was observed as a small rounded bleb within a larger pyrite grain.”
Quartz: Quartz is ubiquitous at Louise Lake, reported by all workers.
Rutile: Harris (1983), describing several polished thin sections of altered rock, noted that “Tiny granules of sphene and rutile occur throughout.”
Sphalerite: Hanson (1992), describing the Lake Zone, wrote that “The volcanics and high level intrusives display weak quartz-sericite alteration and variable amounts of pyrite, sphalerite, chalcopyrite, galena, and arsenopyrite mineralization in the form of small veins, veinlets, microveins and patches.” Several other workers have mentioned sphalerite.
Stibnite: Hanson and Klassen (1995) wrote that “Other sulphide minerals present in rare amounts are stibnite, sphalerite, chalcocite and bornite.” They gave no more details. However, earlier Hanson (1992) noted a single occurrence of stibnite in drill core. Reference to the analytical results in the report shows a sample with an Sb analysis for a 3.1 metre core interval given as 24963 ppm [parts per million], or about 2.5%. Other elements in the interval were given as: As-451 ppm; Cu-27 ppm; Mo-3 ppm; Zn-1574 ppm; Pb-14 ppm; and Bi-2 ppm.
Tennantite: Carter (1970) reported tennantite, writing that “. . . copper values are associated with bluish-grey tennantite, which commonly occurs as a coating on the iron sulphides.” Hanson (1992) described numerous occurrences of tennantite in drill core logs. Carter (1994) wrote that “The presence of tennantite has also been confirmed by mineralogical work by the Geological Survey of Canada [GSC] (L.B. Warren, personal communication). A well-mineralized sample from drill hole C-18 . . . was also found to contain some enargite, which like tennantite is a copper-arsenic sulphide mineral.” Hanson and Klassen (1995) listed tennantite as one of the main minerals of potential economic interest. Schultz (2007), however, wrote that “Mineralization in the Main Zone area consists of several tabular north-dipping zones hosting fine-grained disseminated and vein-controlled sulphides, consisting of an almost even mixture of chalcopyrite and enagrite [sic - enargite], a copper-arsenic sulphide. These occur within a broad area of strong pyritization, with up to 10% disseminated, fracture and vein-controlled pyrite. The chalcopyrite-enargite mixture was originally believed to be tennantite, which is similar in appearance and chemical composition to enargite.” In light of the fact that tennantite was confirmed by the GSC, I believe we can ignore Shultz’ (2007) comment.
Tetrahedrite: This mineral has been reported by several workers. Chamberlain (1969) described it in polished section. Harris (1983) described it in numerous polished thin sections. Hanson and Klassen (1995) described it as occurring in pyrite-tetrahedrite filled fractures. Dr. J. D. Scott has raised a flag, as he is suspicious of tetrahedrite in a generally high-arsenic environment such as we have here. A cursory examination of analytical data in various reports shows that in cases of elevated copper, the arsenic analyses are usually (although not in all cases) an order of magnitude or more than the analyses for antimony. Dr. Scott further points out that without X-ray or microprobe analyses, tetrahedrite and tennantite are not easy to distinguish in polished section. Perhaps most of what early workers identified as tetrahedrite here is actually tennantite.
Titanite: Harris (1983) mentioned several occurrences of “sphene” – see comment above for rutile.
Topaz?: Harris (1983), describing a polished thin section of an “altered tuff”, reported that “Locally there are clusters of tiny, high-relief, colourless needles (? dumortierite) and patches of (?) topaz.” I would regard both minerals as tentative at this stage.
Tourmaline group: Harris (1983), describing an altered tuff, wrote that “Here and there limonite forms boxworks and apparent pseudomorphs after sulfides, often in pockets of coarser quartz and sericite. Small clusters of tourmaline needles occur in this association.” He gave no more details.
Zircon: Harris (1983), describing and altered tuff, listed in one section a trace of zircon, but gave no further data.
Giles Peatfield comments on the rock types reported:
The Louise Lake deposit is hosted by an assemblage of volcanic, sedimentary and intrusive rocks. All of the rock types listed were described either by Hanson and Klassen (1995) or by Schultz (2007). Note that in most cases these are field names.

Giles Peatfield
BASc. (Geological Engineering) University of British Columbia 1966.
PhD Queen's University at Kingston 1978.
Worked for Texas Gulf Sulphur / Texasgulf Inc. / Kidd Creek Mines - 1966 to 1985.
Vancouver based consultant 1985 to retirement in 2016

Mineral List

27 valid minerals.

Rock Types Recorded