The Samatosum deposit is located at an elevation of approximately 1300 metres on a west- north west facing slope, east of Johnson Creek and approximately 3.5 kilometres west of Samatosum Mountain.

The area is located in structurally complex metasedimentary and metavolcanic rocks of the Paleozoic (Lower Cambrian and older(?) to Mississippian) Eagle Bay Assemblage (Formation). The assemblage has a complex deformational history involving multiple stages of thrust faulting and folding during the Jura-Cretaceous which produced strongly foliated and overturned rocks trending northwest and dipping northeast. These Paleozoic rocks are intruded by mid-Cretaceous granodiorite and quartz monzonite (such as the Baldy batholith about 30 kilometres to the north of the deposit), and Early Tertiary quartz-feldspar porphyry, basalt and lamprophyre dykes. These are all locally overlain by Miocene plateau lavas, now represented in the area by occasional erosional remnants.

The deposit area can be divided into several northwest trending, northeast dipping units. From northeast to southwest these are: 1) the Tshinikan Limestone which forms steep, massive landforms dominating the area; 2) mixed sediments consisting of interbedded cherts and argillite; 3) mafic volcanics; 4) the "Mine Series" of rocks which consist of a zone of more mixed sediments and mafic volcanics, with minor felsic to intermediate volcanics, which form the host stratigraphy for both the Samatosum and Discovery or Rea Gold zone (082M 191) deposits; and finally 5) a thick unit of argillites and wackes and a package of felsic rocks which lie in the structural footwall of the Mine Series.

The generalized ore stratigraphy reveals the apparent stratabound nature of the orebody within the hanging wall portion of the heavily strained and highly altered Mine Series rocks. The orebody lies near the interface of altered mixed sediments and predominantly altered argillites/wackes. Original terms such as "sericitic tuffs" for the mixed sediments, and "muddy tuffs" for the altered argillite/wackes are now largely out of favour as it is really alteration products that one sees rather than original lithologies (Friesen, 1990).

The mixed sedimentary unit (SERT) is characterized by a strong yellow to white sericitic content, interbedded with up to 30 per cent cherty/quartz lenses. The altered argillites (MUT) are characterized by light silvery grey muscovite and sericite. They may also often locally contain up to 60 per cent very fine-grained pyrite and host low grade values of base and precious metals. Both units represent altered lithologies; their protoliths were probably variations of an original argillite/wacke/tuff sequence.

Both the SERT and MUT lie structurally below a thick unit of chloritic mafic volcanics, which in the deposit area are most commonly tuffaceous to lapilli in texture; but with an occasional pillowed component.

Both the Samatosum and original Discovery zone or Rea Gold zone (082M 191) 500 metres to the southwest are contained in a very similar stratigraphy: within a package of mixed sediments, argillites and their sericitic equivalents of SERT and MUT, and both are structurally overlain by mafic pyroclastics. There is much speculation regarding their structural and genetic associations. There is a strong suggestion of repetition by folding and/or faulting (which supports a long favoured theory of a thrust fault zone located between the deposits). Alternatively, but currently discounted, the two deposits may exist within similar stratigraphic cycles overprinted by a crosscutting alteration package (Friesen, 1990).

The Samatosum deposit is an early, highly deformed quartz vein system containing massive to disseminated components of tetrahedrite, sphalerite, galena and chalcopyrite hosted in structurally complex wallrocks. The upper portion of the orebody is tabular, averages about 5 metres in thickness, has a northwesterly strike length of about 500 metres and dips at an average of 30 degrees northeasterly for 100-150 metres. In the northern half of the deposit the tabular nature of the orebody gives way downdip to an apparent synformal structure, which is currently interpreted to be caused by slicing and imbrication by local overturning and thrust faulting. The northern half of the orebody has a northwesterly plunge of about 20 degrees, whereas the southern half displays a very slight plunge to the southeast (phase 2 folding?).

Tetrahedrite is the most valuable mineral in the ore zone, followed by sphalerite, chalcopyrite and galena. The tetrahedrite contains 36 per cent copper, 25 per cent sulphur, 23 per cent antimony, 5 per cent zinc, 4 per cent silver, 3 per cent arsenic and 2 per cent iron. Tetrahedrite appears to be the most uniformly distributed, while the sphalerite, galena and chalcopyrite often appear more erratically distributed in the northern end of the orebody as semimassive to massive lenses within the quartz vein host; perhaps indicating more than one mineralizing episode. It is important to note to note that whereas chalcopyrite, sphalerite and galena can be present in minor amounts in virtually any quartz vein occurrence throughout the property; tetrahedrite has so far been rarely found outside the immediate ore zone (Friesen, 1990).

The principal ore-related gangue minerals are quartz (30 per cent), dolomite (19 per cent) and pyrite (11 per cent).

Sericite and muscovite are by far the dominant alteration minerals in the Mine Series rocks and are thought to be a deformational product of the original ore-related alteration. All units from the lower portion of the mafics through the entire Mine Series stratigraphy are sericitic. Muscovite/sericite alteration fronts producing MUT commonly crosscut bedding and foliation, often leaving behind unaltered argillite/wacke remnants.

Other significant alteration in the deposit area includes: silicification or silica flooding of portions of wallrock surrounding the orebody (eg. many original "quartzites" and black cherts are now believed to be silicified MUT and argillites); dolomite, much more intense than previously believed, the bulk of which is probably a late-stage fault-related overprint; pyritization, as a replacement feature of lapilli in the mafic pyroclastics; and the green mica fuchsite, so far almost entirely restricted to a several metre thick occurrence associated with the argillites/MUT along the immediate sheared footwall portion of the ore zone.

In 1985, diamond drilling on the Samatosum (Barite zone) occurrence yielded 0.012, 0.297 and 0.153 per cent copper, 0.07, 0.20 and 0.38 per cent lead, 0.04, 0.08 and 0.53 per cent zinc, 163.9, 282.0 and 20.2 grams per tonne silver with 0.39, 1.6 and 0.25 grams per tonne gold over 3.3, 1.1 and 1.2 metres in holes RG-44, RG-45 and RG-48, respectively (Property File - A.D. [1986-01-01]: Map of Rea Gold Option January 1986 Drill Proposal and Longitudinal Section). Two other drillholes (RG-42 and RG-40), located approximately 200 to 400 metres northwest of the previous holes, yielded 0.33 and 1.01 per cent copper, 0.08 and 2.16 per cent lead, 0.10 and 3.02 per cent zinc, 120.5 and 501.0 grams per tonne silver with 0.40 and 0.29 gram per tonne gold over 1.5 and 0.9 metres, respectively (Property File - A.D. [1986-01-01]: Map of Rea Gold Option January 1986 Drill Proposal and Longitudinal Section).

In 1986, drilling highlights included holes RG-82 and RG-83, which yielded 1.35 and 0.5 per cent copper, 1.81 and 0.53 per cent zinc, 1.28 and 0.38 per cent lead and 450 and 210 grams per tonne gold with 0.28 and 0.96 gram per tonne gold over 1.05 and 12.1 metres, respectively, whereas another hole (RG-85) intercepted 11.05 metres of massive sulphides grading 0.28 per cent copper, 2.8 per cent zinc, 2.6 per cent lead, 43 grams per tonne silver and 0.34 gram per tonne gold (Assessment Report 15718).

In 1989, a drillhole (RG-262), located approximately 300 metres north-northwest of the north end of the Samatosum orebody, intercepted a 9.70-metre thick section of pyritic muddy tuff yielding 0.19 per cent zinc, 0.20 per cent lead and 4.2 grams per tonne silver over 0.5 metre and 0.21 per cent zinc, 0.09 per cent lead and 12.9 grams per tonne silver over 1.2 metres (Assessment Report 19199). Further drilling that year is reported to have tested the Sam horizon.

Before production commenced in June 1989, reserves for the Samatosum open-pit deposit were reported to be estimated at 634 984 tonnes grading 1035 grams per tonne silver, 1.9 grams per tonne gold, 1.2 per cent copper, 1.7 per cent lead and 3.6 per cent zinc (Assessment Report 20984).

In 1990, two drill holes were completed to test the Rea horizon at depth and yielded intercepts of up to 0.15 per cent copper, 1.2 per cent zinc, 1.2 per cent lead, 12.8 grams per tonne silver and 0.45 gram per tonne gold over 2.5 metres (286.9 to 289.4 metres downhole), including 1.163 per cent copper, 2.37 per cent zinc, 3.99 per cent lead, 58.9 grams per tonne silver and 0.56 gram per tonne gold over 1.2 metres in hole RG391 (Assessment Report 20984).

Also at this time, drillhole RG-376 intersected a wide zone of silicification and quartz stringers hosting tetrahedrite and minor base metal sulphides yielding 21.3 and 24.5 grams per tonne gold over 9.8 and 10.5 metres, respectively (Property File – Hill, A.R. [1991-03-26]: Memo re: Budget and Exploration Proposal at Samatosum). The intercepts were separated by approximately 20 metres of barren rock and are located approximately 80 metres downdip and 100 metres down strike of the southeast end of the Samatosum orebody.

In 1991, underground drilling identified a new mineralized zone 10 metres below and parallel to the main Sam Horizon ore zone but appearing to dip more steeply. The zone varies in thickness from 2 to 11 metres, averages from 2 to 4 metres and has been intersected over a 50-metre strike length. The zone is reported to average approximately 0.43 per cent copper, 2.00 per cent lead, 3.23 per cent zinc, 67.0 grams per tonne silver and 7.29 grams per tonne gold (Property File – Meyers, R.E. [1991-08-13]: South-Central District Monthly Reports - March and July).

Also at this time, two drillholes (RG-394 and RG-395) were completed on the south-southeast and east-northeast extensions of the Samatosum deposit, respectively. Drillhole RG394 yielded 0.177 per cent copper, 1.090 per cent zinc, 0.938 per cent lead, 15.8 grams per tonne silver and 0.22 gram per tonne gold over 12.2 metres (177.0 to 189.2 metres downhole; Assessment Report 21689). Drillhole RG395 yielded intercepts including two short higher-grade veined zones grading 0.079 and 0.157 per cent copper, 11.45 and 2.16 per cent zinc, 2.10 and 0.40 per cent lead and 12.9 and 31.5 grams per tonne silver with 0.10 and 0.34 gram per tonne gold over 0.20 and 1.20 metres (329.1 to 329.3 metres and 443.4 to 444.6 metres downhole), respectively, and lower-grade broader intercepts including 0.029, 0.072 and 0.087 per cent copper, 0.293, 0.857 and 0.362 per cent zinc and 0.270, 0.911 and 0.222 per cent lead with 5.2, 10.9 and 6.0 grams per tonne silver over 9.1, 4.7 and 9.3 metres (460.3 to 469.4 metres, 478.3 to 483.0 metres and 491.7 to 501.0 metres downhole), respectively (Assessment Report 21689).

Underground mineable reserves at Samatosum are 80,278 tonnes grading 1.2 per cent copper, 2.9 per cent zinc, 1.7 per cent lead, 1021.5 grams per tonne silver and 1.7 grams per tonne gold (Northern Miner - August 5, 1991). Both open pit and underground reserves are expected to be exhausted by October 1992. The underground reserve is the strike extension of the open pit deposit and extends approximately 198 metres beyond the pit wall before it is structurally terminated.

Work History

The Samatosum deposit was discovered in 1986. During 1988 a feasibility study determined the deposit could be mined economically by open pit methods, despite an unusually high 25:1 waste-to-ore stripping ratio. Mine stripping began in March 1989; ore production and milling began in May 1989; shipments began in June 1989.

Mining ceased in July 1992 and milling ceased in September 1992.