The Fog occurrence is located at an elevation of approximately 1800 metres on a north-facing slope, approximately 3.4 kilometres south-southwest of Shedin Peak.
Regionally, the area is underlain by clastic sedimentary rocks of the Middle Jurassic to Upper Cretaceous Bowser Lake Group, which have been intruded by granodiorite of the Upper Cretaceous Bulkley Plutonic Suite. Hornfels and calc-silicate skarn is developed in the contact area of the intrusion.
Locally, low-grade porphyry-type copper-molybdenum mineralization is present in the stock in east-west–trending narrow quartz veins over an area of approximately 3000 metres east-west and 500 metres north-south.
Detailed mapping in the Fog-Peak target area in 2014 identified two phases of monzonite and three phases of dikes. The oldest monzonite (MZ1) is a moderately foliated medium- to coarse-grained intrusion with up to 5 per cent megacrystic square, zoned feldspar phenocrysts. There is a dark-grey chilled contact with the neighbouring sediments and foliation is parallel to that in the sediments, which is steeply west dipping in the two eastern cirques of the Fog ridge. The MZ1 unit has potassium feldspar stockwork, barren grey quartz veins, aplite dikes and many crosscutting vein types that appear to increase in intensity towards the east at and/or below the contact with the sediments. The younger monzonite (MZ2) outcrops extensively in the area and is a buff to pink, medium- to coarse-grained megacrystic intrusion with up to 10 per cent pink, zoned potassium feldspar phenocrysts. The contact with the MZ1 phase is not exposed and the two units may be gradational into each other.
Three generations of dikes were identified in the area; the highest concentration of dikes appears to correlate with the location of the MZ1 phase of monzonite. D1 is quartz-feldspar-biotite porphyry with 5 per cent small white (sericitized) feldspar phenocrysts; 3 per cent glassy quartz eyes to 2 millimetres and 3 per cent fine-grained red, shreddy biotite and disseminated pyrite. The matrix is siliceous and distinctly white. Portions of the dike have potassium feldspar network veinlets similar to MZ1 and it appears that all vein types cut this dike. The exposure of the dike strikes north-south and dips steeply west subparallel to the foliation in the sediments and MZ1, but has apophyses leading northeast from the main dike. There is no apparent foliation in the D1 dike. D2 is a white feldspar porphyritic dike with smaller quartz and biotite phenocrysts and a grey matrix. These dikes typically trend east-west, dip steeply to the south and cut the D1 dike. In part of the area these dikes form another east- west corridor and cut a quartz-feldspar porphyry sill that could be part of the D1 event. The D3 event is fine-grained mafic dikes found in the central and northeast part of the Fog area. The dikes are dark-green and chloritic with 1-centimetre hornblende or pyroxene phenocrysts. The dikes cut pegmatite and quartz veins and one D3 dike is seen to be displaced by a west-northwest–trending shear.
Sediments in the area are comprised of argillite, greywacke and arenite. Disseminated pyrite occurs throughout most of the stratigraphy and red-coloured shreddy biotite is evident in the arenite. Calcareous portions of the stratigraphy are seen in the central cirque near the D1 ‘white’ dike, where they are altered to skarn including garnet, epidote and diopside. Fragments and irregular veins of garnet with lesser epidote are incorporated in the D1 dike where it cuts through the skarn. Iron oxide alteration that is related to pyrite disseminated or in veins is identified in the area and occurs in both the monzonite and sediments.
The oldest vein set in the Fog target area is a network of thin potassium feldspar veins that are pervasive in the foliated monzonite (M1) and ‘white’ porphyry dike (D1) in the east-central part of the target area. There is no sulphide or rare disseminated pyrite-chalcopyrite within the potassium feldspar network. Barren, possibly A-type quartz veins and aplite dikes are commonly found in the area with the network and cutting the potassium feldspar network. The dominant mineralized vein sets are straight-walled, drusy quartz–potassium feldspar with halos of potassium feldspar or muscovite/sericite (V4b and V5b veins). Rare sulphide-only (typically pyrite) V6b veins were found in talus and outcrop. Biotite-filled fractures with muscovite halos and magnetite-amphibole veins with muscovite halos (V2b) were found in talus boulders only. The vein compositions including alteration halo indicates that the area is a potassic zone.
Sulphide content varies with vein type to include pyrite, chalcopyrite and molybdenite in addition to the main mineralized vein set. Disseminated sulphide is found in some of the halos of the sulphide-mineralized veins. Generally, the area is dominated by pyrite, but higher chalcopyrite content was seen in the talus field. Chalcopyrite and molybdenite typically occur in separate veins.
The dominant orientation of the mineralized veins is east-southeast with northeast and northwest orientations measured in the eastern portion of the Fog target, where there is a coincidence of higher intensity of veining and the presence of east-west– and north-south–trending dikes cutting the monzonite and sediments. In all cases, veins dip steeply with dominant dip direction to the north although south dips were also identified.
Work History
Mineralization was first identified in 1969, and the 39 Fog claims were staked later that year by Sicintine Mines Ltd. A program of geological mapping, geochemical sampling and trenching was performed at this time. Sampling of trenches yielded 16.4 grams per tonne silver, 0.27 per cent copper and 0.01 per cent molybdenum over 15 metres and 0.16 per cent copper with 0.02 per cent molybdenum over 9 metres (Property File - 812848).
In 1978, St. Joseph Explorations Ltd. completed a program of rock sampling and geological mapping on the Fog and Peak claims. Samples from the Fog claim yielded an average of approximately 0.05 per cent copper and 0.008 per cent molybdenum (Assessment Report 7116).
In 2013 and 2014, Vale Exploration Canada Inc. completed a program of geological mapping, geochemical sampling and a 3278.0 line-kilometre airborne magnetic survey on the area as the S2 property. In 2017, an induced polarization and magnetotellurics survey was completed on the property.
In 2014, samples (RX399285, RX399286, RX399291 and RX399292) from mineralized quartz monzonite boulders on the central area of the mineralized zone yielded values up to 0.118 gram per tonne gold, 5.3 grams per tonne silver, 0.583 per cent copper and 0.167 per cent molybdenum, whereas chip samples (RX399294 and RX399295) from mineralized quartz monzonite outcrops in the central area yielded up to 0.159 per cent copper and 0.073 per cent molybdenum (Assessment Report 35139). Several hundred metres east of the previous samples, a channel sample (RX401428) from a large talus boulder yielded 0.22 per cent copper over 0.59 metre, whereas another channel sample (RX401533), taken from a nearby outcrop, yielded 0.049 per cent molybdenum and 0.057 per cent copper over 0.72 metre (Assessment Report 35139). Also at this time, samples (RX398052, RX398062 and RX398063) from float boulders located approximately 1.5 kilometres west of the central mineralized zone yielded up to 0.08 gram per tonne gold, 6.6 grams per tonne silver, 0.531 per cent copper and greater than 1.00 per cent molybdenum, whereas grab samples (RX398055, RX398057, RX398058 and RX398059) of granodiorite hosting mineralized quartz veins yielded up to 10.3 grams per tonne silver, 0.513 per cent copper and 0.640 per cent molybdenum (Assessment Report 35139).
