The Shamrock Breccia occurrence is situated immediately east of a switchback on an old logging road, immediately north of Erie Lake, approximately 1 kilometre north of Highway 3, 2 kilometres east of the historic Arlington mine and 3 kilometres west of Salmo.
The area is underlain by Early Jurassic Rossland Group rocks intruded by phases of the Middle Jurassic Nelson Batholithic Suite. Within the Rossland Group, the Archibald Formation, a sequence of fine to coarse sediments, is overlain by the volcanic rocks of the Elise Formation and the mainly fine-grained clastic rocks of the Hall Formation. The Archibald Formation ranges from interlayered argillites and siltstones to dark, laminated rusty argillites interlayered with occasional augite phyric flows marking a gradational contact with the overlying Elise Formation. The Elise Formation is subdivided into a basal unit of mafic flows and flow breccias overlain by a thick accumulation of intermediate pyroclastic rocks. To the south, exposures of the Lower Elise contain massive augite-phyric flows, flow breccias and heterolithic to mafic clast-dominated volcaniclastics interbedded with well-layered, mafic water-lain tuff beds. To the north the Elise is dominated by well-layered fine to lapilli tuffs interlayered with dark graphitic argillite and dark grey argillaceous siltstone.
To the north, the southern edge of the Bonnington Batholith, part of the Nelson Plutonic Suite, is exposed, as is a small granitic stock in the valley to the south. Exposures of the Bonnington Batholith consist of potassium-feldspar porphyritic to locally massive granodiorite cut by felsic dikes.
Several generations of faulting have been recognized in the area. North-trending, east-verging thrust faults occurring to the south and southeast are cut by Cretaceous and Middle Jurassic plutons. Parallel, north-northeast–trending faults occurring to the south cut earlier folds and are cut and sealed by Jurassic plutons. Steeply dipping, northwest-trending extensional faults running through the centre of the Sadarsa property cut both earlier structures and Jurassic plutons.
A stripped area of outcrop has revealed a sheared, clay-altered, silicified, brecciated zone occurring at the contact between volcanics and sediments of the Archibald Formation to the north and granites belonging to a small granitic stock exposed in the Beaver Creek–Erie Lake Valley. The stock, believed to be related to the Wallace Creek stock to the east, is offset by several prominent northwest-trending faults and comprises a medium-grained, light grey biotite granite or granodiorite containing numerous aplitic dikes along the northern margin. The contact zone of the stock is marked by localized disseminated pyrite and pyritic or jarosite-stained shears and fractures.
The brecciated zone has an estimated width of 5 metres and an apparent northwest strike. Scattered sulphides of galena, sphalerite, pyrite and chalcopyrite occur as disseminations, in quartz stringers and in the matrix of the brecciated intrusive. Limited outcrop has obscured the true extent of the mineralization.
Prior to 1902, the Transvaal and Zambesi Mining Company conducted development work on the Armstrong claim group (MINFILE 082FSW267), consisting of the Armstrong, Erie and Black Knight claims, to the west of the Shamrock occurrence. The property was dormant from 1902 until 1928, when the claims were acquired by S.E. Coulter and P. Coulter. The old tunnels were cleaned out and the trail to the property was opened up. The workings, situated on the Black Knight claim, consisted of open-cuts and four tunnels. The tunnels developed four widely separated silicified fractured zones in granite.
In 1978 and 1979, Salmet Resources Corporation staked the Dan, Dan 2 and Dan 3 claims over the southern half of the modern Sadarsa property. The claims were held as part of the Silverhorn property. In 1980, Salmet Resources conducted a program of geochemical sampling, geophysical surveying and trenching on the Silverhorn claims to the immediate east.
The first record of exploration on the Sadarsa property was in 1981 on the Key claim to the west of the Dan and Armstrong claim groups. The Key claim covered an area containing the Meadows occurrence (MINFILE 082FSW268). Rick Wierzbicki carried out a limited molybdenum exploration program on the property, collecting two geochemical samples.
In 1983, Taiga Consultants Limited, on behalf of Rex Silver Mines Limited, conducted reconnaissance mapping, prospecting, sampling, soil geochemistry and ground geophysical surveying on the ORC claims to the north. Five samples were collected from the Erie Creek showing.
In 1989, a very low-frequency electromagnetic geophysical ground survey was conducted over the DC, Bear and Poogy claims to the immediate west of the historic Armstrong claim group (MINFILE 082FSW267). Following this survey, 117 soil samples were collected between 1989 and 1990. In 1990, a grid was established over the southeastern portion of the claim group. A total of 5.2 line kilometres of ground geophysical surveying were completed and 66 soil and eight rock samples were collected and sent for analysis.
In 1989, the northeastern portion of the modern Sadarsa property was staked as the Erie Creek property. Between 1989 and 1990, Desert Gold Resources Incorporated conducted an exploration program of geological mapping, geophysical surveying and soil, silt and rock geochemistry on the Erie Creek claim group.
Though no record of work exists for the Breccia showing prior to 1990, a small area of outcrop was mechanically stripped sometime between 1970 and 1990.
In 1990, a program of prospecting, mapping, showing and outcrop sampling and geophysical surveying was completed on the Shamrock claim group by claim owners R. Bourdon and C. Pittman. Bourdon and Pittman were the first to identify the Shamrock Breccia showing. The showing was mapped and samples were collected and sent for analysis. Samples returned erratic results for gold, silver, lead, zinc and copper.
Also in 1990, R. Jordan conducted a mapping and prospecting traverse across the Sherman claim to the west of the Shamrock zone and immediately east of the Armstrong claim group (MINFILE 082FSW267). The following year, Jordan followed up the mapping and prospecting program by collecting 23 soil samples on the Sherman claim and 35 samples on the RR claim to the immediate north of the Shamrock zone.
In 2007, D. Lavoie staked the Sadarsa claim group. That same year, prospector Tom Kennedy conducted a small rock geochemistry program on the property, collecting 42 rock samples. As a follow-up to the rock sampling program, Robert Klewchuk Limited was commissioned to conduct a soil sampling program on the property in 2008. Samples were collected over two grids—one to the southwest of the Erie Creek showing in the northern portion of the property and the other slightly north of and between the Meadows (MINFILE 082FSW268) and Shamrock occurrences in the southwestern portion of the property. Between 2009 and 2010, Kennedy conducted another rock geochemistry program, collecting 22 samples from both outcrops and float from an area to the east of the Shamrock vein in the southeastern corner of the property. Later in 2010, an additional nine samples were collected from the southwestern corner of the property from an area between the Meadows (MINFILE 082FSW268) and Armstrong (082FSW267) occurrences.
In 2011, Trygve Hoy, on behalf of Kootenay Gold Incorporated (also referred to as Kootenay Silver Incorporated), conducted a short program of geological mapping and sampling on the property. Seven samples were collected from the Meadows occurrence (MINFILE 082FSW268), 20 from the Shamrock vein, four from the Maybee vein and one from a new vein exposed approximately 1 kilometre west of the Shamrock vein. That same year, Tom Kennedy collected 65 rock samples across the southern portion of the Sadarsa property.
In 2012, Kennedy carried out a 34-sample rock geochemistry program over the Shamrock zone. Sampling was focused in the area of the Shamrock vein and to the south of the Maybee vein.
The best result from the 1990 sampling program was sample 72994, which returned 1.91 grams per tonne gold (Assessment Report 20208, Appendix II, page 4).
