The Yuniman occurrence is situated on the crest and south slopes of Yuniman Ridge near the headwaters of Bradshaw Creek, approximately 10 kilometres northwest of Olalla, British Columbia.
The regional geology of the area consists of a series of Carboniferous to Triassic volcanic and sedimentary rocks that have been intruded by granitic Okanagan intrusions. Larger intrusions are composed of granite and granodiorite, whereas smaller stocks are composed of diorite and gabbro. Numerous sills, dikes and apophyses are associated. Carboniferous to Triassic rocks are assigned to the Shoemaker and Old Tom formations, overlain by the Upper Triassic Independence Formation. These rocks form the eastern limb of a large anticlinal fold with fold axes striking roughly north.
The predominant rock type in the claim area is a dark brown, grey to white, fine-grained, massive competent chert. Occasional thin beds up to 0.3 metre thick are identified by layers of chert pebble tuff or silt. The age of these chert beds is uncertain and could belong to the Independence or Shoemaker formations. The cherts are in fault contact with andesitic volcanic rocks called the Old Tom Formation. Jurassic diorite and gabbro intrusions cut the cherts and andesites. A pervasive quartz-calcite alteration affects the andesitic rocks and the diorite intrusion. The four main rock types encountered at the occurrence are argillaceous chert, dark green andesite, buff chert and chert breccia, and biotite hornblende diorite. A number of narrow, north-trending, postmineral andesite dikes are also present.
Mineralized veins appear to be of four types and/or orientations. The first type are northeast to east-northeast–trending quartz-calcite-galena-sphalerite-gold-silver veins. These veins appear to be somewhat older than quartz-calcite-pyrite-arsenopyrite-gold veins trending north to 340 degrees. A third but minor mineralization type consists of late-stage quartz-pyrite-arsenopyrite veinlets hosting low gold values and the calcite-scapolite-garnet alteration zones of limy andesite, which show patches of pyrite and gold values. Quartz-pyrite veins in the andesite carry significant arsenopyrite and sometimes host free gold as inclusions in the pyrite. Marcasite and pyrite occur along fractures in the andesite and pyrrhotite with chalcopyrite replacing calcite amygdules in andesite flows. The diorite stock also hosts marcasite, pyrite and pyrrhotite along fractures with late, northeast-trending fractures hosting quartz-calcite-pyrite-galena-sphalerite veins and pods that carry gold and silver values. Disseminated magnetite is also present.
The most significant alteration and mineralization occur in an irregular, north-trending, white sugary quartz replacement zone bordering a coarse-grained, biotite hornblende breccia dike, 5 to 15 metres wide. The dike occurs along a fault, striking 340 degrees. Numerous quartz veinlets host pyrite and arsenopyrite. The zone is up to 40 metres wide and extends from the contact of the breccia dike east to tunnel No. 2 of the Old Yuniman mine.
The best sample of gold associated with arsenopyrite was from diamond drill hole Y86-4 in 1986. The drillhole intersected a vein at 56.77 metres depth. The 0.3-metre true-width interval yielded 1.95 per cent arsenic and 94.97 grams per tonne gold (Assessment Report 15843). In drillhole Y86-5, the replacement zone extends from 153 to 217 metres depth. Four sections from this drillhole yielded 1.23 to 2.88 grams per tonne gold over 3-metre or greater intervals (Assessment Report 15843). Samples YT2-7, -9, -11, -13 and -16 from this breccia zone from tunnel No. 3 of the old Yuniman mine yielded 5.86, 3.60, 2.67, 12.51 and 1.41 grams per tonne gold, respectively.
In the vicinity of the Far West claim (Lot 2469), rhodonite occurs in irregular pockets in a zone approximately 45.7 metres long by 4.6 metres wide in chert.
The Yuniman occurrence consists of several escheated and reverted Crown grants, including Black Pine (Lot 1912, escheated), Bush Rat (Lot 1913), Black Jack (Lot 1914), Little Bessie (Lot 1915), Far West (Lot 2469), Hub Fraction (Lot 2470), Triune (Lot 2471) and Blue Bell (Lot 2472). The Old Diggings is a more recent claim also staked in the area of the showing. The claims have been referred to as the Ymirman, Yumman, Yuninan or Yuniman group. The group was originally owned by E. Bullock-Webster and Crown granted in 1902. Initial exploration and development consisted of more than 61 metres of crosscuts, drifts and raises in three adits, two shafts and open cuts.
Hedley Yuniman Gold Fields Ltd. acquired eight Crown grants in 1937. An additional 44 adjacent claims and fractions were staked and prospected.
In 1946 and 1947, 113 metres of crosscutting and drifting was completed in a new lower (No. 4) adit at approximately 1810 metres elevation.
Toby Creek Resources Ltd. optioned the property in 1984 from J. Hrabi. The Old Diggings claim was staked. A comprehensive exploration program was carried out in 1984 and followed up with diamond drilling in 1986. This drilling consisted of five drillholes totalling 626 metres and focused on the Main zone. The best results include drillhole DDH Y86-04 with 95 grams per tonne gold over 0.76 metre in quartz-arsenopyrite veins and drillhole DDH Y86-1 with 4.18 grams per tonne gold over 5.1 metres beneath the Bush Rat pit (Assessment Report 33729). A 51 per cent option agreement was granted to T.R.V. Minerals Corp. in 1987.
The present Bradshaw Hill property was expanded by C. Greig, partner to B. Kreft, in January 2004, just prior to the finalization of an option agreement with Firestone Ventures Inc. In the same year, a work program carried out by Firestone Ventures Inc. consisted of five days of helicopter-supported detailed geological mapping, rock geochemical and limited silt and soil geochemical sampling. The program focused on due diligence–style sampling of the Main zone and “ground truthing” of geochemical anomalies to the east and west. A total of 89 rock, one soil and four silt samples were taken. The program led to the discovery of the Mozart and Beethoven zones, consisting of fairly abundant fine arsenopyrite veining within altered chert, situated southwest of the Main zone; however, these are of insufficient grade and extent to be economically viable (Assessment Report 27746).
In 2005, Target Exploration and Mining Company optioned the property. Target undertook geological, geochemical and geophysical work between 2006 and 2008. In 2007, Target completed a total field magnetics and induced polarization survey, approximately 3.5 by 0.8 kilometre in size, following the east-northeast trend of mineral showings on the property. Sampling resulted in zones of anomalous metal values in soil coincident with chargeability and resistivity anomalies. Drilling in 2008 consisted of nine drillholes totalling 1050 metres on three areas within the property, with the majority at the Main zone. The best results include drillhole DDH BS08-05, with 1.1 grams per tonne gold over 1.1 metres (Assessment Report 33729). The option was terminated in 2008.
Soil sampling between 2007 and 2012 has outlined multi-element geochemical anomalies near known mineralization, extending the potential of bedrock mineralization outward from the showing. Sampling has also identified new prospective areas. The 2012 sample program involved 366 samples (Assessment Report 33729).
