The Boulder occurrence is located about 15.7 kilometres northwest of Bowser Lake and approximately 62 kilometres north of the community of Stewart.
The area of the Boulder showing is underlain by volcaniclastic rock of the Lower Jurassic Betty Creek Formation (Hazelton Group). A 10-centimetre-wide quartz-calcite vein with sulphides and wallrock clasts occurs in mafic volcanic rock. Sulphides consist of trace galena, disseminated pyrite, and patches of disseminated chalcopyrite and malachite. Sample B055298 assayed 13.65 grams per tonne silver, 1 per cent copper, 1.1 per cent lead and 0.97 per cent zinc (Assessment Report 37433). In 2017, Pretium Exploration collected a total of 309 samples from the boulder train area. The main concentration of boulder samples collected in 2017 is about 2 kilometres south of sample B055298 location. By the end of 2017 the boulder train source had not been located.
The first work on the mineralized boulder train area was completed by Noranda Exploration in 1989 where 29 rock samples, 14 soil samples, and 10 silt samples were collected across their Knipple property, with the best results coming from sulphide-rich, quartz-calcite vein and breccia float boulders collected along the lateral moraine in the Boulder zone. The boulders are sub-rounded to sub-angular and up to 1 metre in diameter. The boulders contain variable amounts of coarse sphalerite, galena, chalcopyrite and pyrite. Values up to 19.25 grams per tonne gold, 17.14 grams per tonne silver, 0.14 per cent copper, 4.08 per cent lead and 18.25 per cent zinc were obtained (Assessment Reports 20556 and 37443).
Follow-up work by Noranda included a VLF-EM geophysical survey, which identified a conductor near the foot of the boulder train. Six diamond-drill holes, for a total of 346.6 metres, were completed in order to test the geophysical conductor and a possible source for the boulder train (Assessment Report 22074). Alpine Exploration completed a 750 metre HLEM survey in 1996 (Assessment Report 25058) and Westpine Metals completed a 3025 metre magnetic and HLEM survey in 1997 (Assessment Report 27876). In 2004, Teuton Resources acquired the claims area by staking and did some limited prospecting. In 2006, on behalf of Teuton Resources, 292 line kilometres of airborne magnetics and EM were flown over a survey grid on their Ruy property (Assessment Report 28690).
Prior to 2014, Pretium Resources put together a very large block of contiguous claims called the Bowser Property, stretching from Brucejack Lake to Bowser Lake and farther to the south and southwest, to Summit and Long lakes. The Bowser Regional Project area, approximately 20 kilometres southeast of the Valley of the Kings deposit, comprises approximately 800 square kilometres.
In 2014, on behalf of Pretium Exploration on their Bowser property, an 1885 line kilometre magnetic and radiometric survey was flown at 400 metre line spacing. Due to inclement weather, only 350 line kilometres of 1TEM Time Domain Electromagnetics (TDEM) were flown (Assessment Report 36790).
In 2015, Pretium Exploration expanded the magnetometer and radiometric survey area to the east and south, as well as infilling specific block areas to 200 metre line spacing. A total of 1139 kilometres of magnetics and radiometrics were completed. In 2015, the proposed 2014 1TEM survey blocks were also completed, and the 1TEM survey grid was extended to match the area covered by the 2015 magnetometer and radiometric grids, totalling 3402 1TEM line kilometres flown that year. Follow-up work was to focus on areas where the resistivity and conductivity indicate alteration, and the conductive anomalies might indicate a massive sulphide bodies.
In 2016, Pretium Exploration initiated a 4 kilometre magnetotelluric (MT) line starting in the Canoe Glacier valley, crossing over the toe of the Knipple Glacier and continuing on to Scott Creek. A Direct Current Induced Polarization (DCIP) was also completed, focussing on the Salmon River Quock Member sediments and the underlying volcanics at the Kirkham, Pipe Dream, Knipple Lake, and Cone zones. Ten DCIP lines, covering 23.5 kilometres with 19 MT sites, as well as 26 MT stations covering the Bowser Valley were completed. In order to expand the structural and lithological interpretation at KL Gossan and KL East Zones, where outcrop exposure was minimal, 24 more MT sites were surveyed. The results of this 2016 work included the identification of 55 zones of interest related to resolved anomalies over Cone zone (5), Kirkham (18), Pipe Dream (21), regional MT Transect line (5) and Bowser infill MT area (6) (see Assessment Report 36790 for further information).
In 2016, Precision GeoSurveys Inc., on behalf of Pretium Exploration, completed a 1400 line kilometre airborne magnetic and radiometric survey on the Bowser Property. The survey covered the southern end of the Bowser Property, as an irregular 24.7 by 23 kilometre block, with 200 metre line spacing, flown north-south, and 2 kilometre tie lines. The purpose of the survey was to complete the magnetometer and radiometrics coverage over the entire Bowser Property claim area, as the northern extents of the property had previously been flown in 2014 and 2015. See Assessment Report 36793, Appendix III for Precision's,"Airborne Geophysical Survey Report", including 2014-2016 magnetic and radiometric maps.
In 2017, Pretium Exploration conducted grassroots prospecting, sampling and mapping on their Bowser property, mostly southwest and south of Bowser Lake. They collected 2901 rock and 429 silt samples (Assessment Reports 37435, 37443). Several new MINFILE occurrence are documented and a number previously documented occurrences were visited by Pretium.
In 2018, beyond the Brucejack mine area (104B 193), Pretium continued to evaluate their surrounding 1250 square kilometres of mineral claims. From July to October, 31 diamond-drill holes totalling 7725.1 metres were completed on the Bowser property; 10 holes tested the Lilliane (104A 112), 2 holes tested the Moonlight (104A 005), 9 holes tested the Bluffy (104B 075), 1 hole tested the Virginia K (104A 118), 3 holes tested the Outlaw (located 1.3 kilometres north of Moonlight Glacier 1 (104A 120), 4 holes tested the Haimila (104A 226), and 2 holes tested the Ridgeback (located 1.9 kilometres west of Koopa Bowl (104A 233). The exploration targets were widespread and drillholes targeted epithermal, porphyry copper, shear zone-hosted gold, and volcanogenic massive sulphide (VMS) style mineralization. The company also carried out mapping and prospecting (Assessment Report 38235).
As of September 2019, two drills were testing the high-priority A6 zone volcanogenic massive sulphide (VMS) target located 14 kilometres northeast of Brucejack mine; a third drill targeted a VMS system at the Canoe zone (104B 732, 734) located 15 kilometres west-southwest of Sharktooth; and a fourth drill targeted an intrusion-related gold system at the Koopa zone (104A 222, 229, 233) located 10 kilometres south of the Sharktooth. Drilling earlier in the summer also focussed on the Tuck zone (104B 730) located 22 kilometres west of Sharktooth and Liliane zone (104A 112) located 17 kilometres south of Sharktooth, both epithermal gold system targets.
To date (2019), approximately 26,103.1 metres have been drilled in 81 holes. To facilitate exploration work, the Bowser property has been divided into zones and the drilling took place in seven of these zones: A6 Anomaly, Canoe, Koopa, Tuck, Haimila, Kirkham, and Lillianne (Assessment Report 39085).
See Betty (104A 008), located 28 kilometres south of Sharktooth, for details of relevant work done on Pretium's grassroots project on their Bowser property, including significant property-wide geophysical surveys completed prior to to 2017. Refer also to West (104B 193), located 23 kilometres west of Sharktooth, for details of related mineralization and a common work history relating to the Brucejack project of Pretium Resources.
