The Packsack occurrence is located 12 kilometres from tidewater on Douglas Channel about halfway between Prince Rupert and Kitimat. The claims lie on the east side of the ridge at the bend of the Ecstall River, 10 kilometres south of Johnston Lake. The Steelhead (103H 036) and Horsefly (103H 014) showings occur 5.1 and 4.3 kilometres southeast, respectively.
The Packsack prospect crops out in five small exposures in two parallel east-draining creeks, at 230 metres elevation on the east slope of Prospect Ridge. The prospect was discovered by W. Padgham in September, 1957, as a single 4.5-metre wide massive sulphide band in Gunnysack Creek. Follow-up work revealed another four sulphide horizons distributed over a 25-metre interval along Packsack Creek, 150 metres to the south of Gunnysack Creek (Schmidt, 1996a, b).
A north trending, steep easterly dipping belt of metavolcanics and metasediments consisting of chlorite-sericite schist, quartz-sericite schist, mixed dacitic to rhyolitic rocks, phyllite, and meta-siltstone are bounded by altered hornblende diorite of the Coast Plutonic Complex. All rocks are cut by hornblende lamprophyre dikes.
Two massive sulphide bodies, 170 metres apart, occur within the quartz-sericite schist and are associated with a 600-metre long, 34-metre wide shear zone. The deposit averages 3.8 metres in thickness and has been traced continuously for 600 metres. The sulphide lenses are hosted in pyritic quartz-sericite schist units that are interbedded with basaltic and andesitic tuffs and massive flows. The pyritic quartz-sericite schists are interpreted and felsic ash tuffs and fragmental tuffs. The mineralization is similar to that at the Ecstall deposit (103H 011), about 13 kilometres to the north-northeast.
The southern body, up to 6 metres wide and traced for 365 metres, consists of massive pyrite with minor chalcopyrite, chalcocite and sphalerite. The mineralized body is open at depth and along strike in both directions and appears to be thickening and becoming more zinc rich (relative to copper) with depth. The northern body is up to 0.6 metre wide. Disseminated pyrite is common in the quartz-sericite schist.
In 1986, unclassified reserves were 2.7 million tonnes grading 0.5 per cent copper, 0.2 per cent zinc, 0.01 per cent lead, 34 grams per tonne silver and 0.3 gram per tonne gold (Assessment Report 15756).
The Packsack property has been repeatedly explored by prospecting and by geological, geochemical and geophysical programs over 40 years. The deposit was drilled in 1960 (11 holes) and again in 1990 (3 holes). Exploration trenches are conspicuous by their absence, but the sulphide deposit has been well delineated by drill intersections and by electromagnetic (EM) surveys. Thirteen of the 14 drillholes intersected massive and semi-massive pyrite, and the deposit remains open to the north, south and at depth. Drilling has outlined two adjacent massive sulphide horizons, the Main and Hangingwall zones that range in true thickness from 2 to 8 metres. Both extend along strike for at least 500 metres.
Ecstall Mining Company Ltd. carried out a reconnaissance geological survey in this vicinity in 1957 under the direction of W.R. Bacon. Sulphide showings were discovered at an elevation of about 244 metres in the beds of two intermittent streams on the east slope of what came to be know locally as Prospect Hill. Sixteen claims in two rows of eight (Packsack 1-8 and Gunnysack 1-8) were staked in a north-south direction. An EM survey was carried out over the showings in 1958. The assets of Ecstall were transferred to the parent company, Texas Gulf Sulphur Company, in 1960 and Ecstall was placed in voluntary liquidation in August of that year. Work during 1960 included 881 metres of diamond drilling in 11 holes. All the holes are reported to have cut pyrite mineralization, much of which is massive.
The company name (Texas Gulf) was changed in 1972 to Texas Gulf, Inc. and in 1973 to Texasgulf Inc. During 1973, geological mapping, and a geochemical soil survey (119 samples) over 3.2 line kilometres were carried out over Packsack 1-4 and Gunnysack 1-8. In 1975, a shootback EM survey was carried out over 9.75 line kilometres on Packsack 1 and 2 and Gunnysack 1-6. Texasgulf Inc. dropped the claims and they were restaked by Mr. C.W. Graf.
In 1981, the property was optioned by a joint venture of E & B Explorations Inc. and Welcome North Mines Ltd. who did airborne geophysics, geology and geochemistry. After the property was dropped, Noranda Exploration Company Limited optioned the property in 1985. They staked more claims and carried out airborne EM surveys, ground geophysics, geology and rock geochemistry. Noranda dropped the property in 1987 and the claims were transferred to Mr. Graf. In 1988, Ecstall Mining Corporation purchased the property consisting of 15 claims including Ecstall 8, 9, 10, 15; Tall 1, 3, 6, 13; Fall 10, 11; Fall 12-13 Fr. In 1989, Cominco Ltd. optioned the deposit. In 1990, they drilled three holes totalling 934 metres.
In 1994, Atna Resources Ltd. examined the Horsefly and Steelhead (103H 036) areas and following this entered into an option agreement with Ecstall Mining Corp. In 1995, Atna Resources commenced exploration with a program of linecutting, Max-Min EM survey, mapping and drilling (1076 metres in eight holes).
In 2012, Winrock Resources Ltd. acquired the property and in October, conducted a rock sampling program and reconnaissance sampling program on the Packsack property and targeted two main areas within the claim boundaries.