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Brucejack - Valley of the Kings Zone, West Zone |
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British Columbia, Canada |
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Au Ag
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Brucejack gold-silver deposit is located in NW British Columbia, Canada, ~950 km NNW of Vancouver, 65 km NNW of Stewart, and 21 km SSE of the Eskay Creek Mine (#Location: 56° 28' 3"N, 130° 11' 14"W).
Prospecting and exploration for precious and base metals in the district surrounding the Brucejack deposits dates back to the late 19th century. In 1935, copper-molybdenum mineralisation was discovered on the Sulphurets Property by prospectors in the vicinity of the Main Copper Zone, ~6 km NW of Brucejack Lake, although between 1935 to 1959, the area was relatively inactive, with claims not being pegged until 1960. Various companies conducted exploration around and over the Brucejack district from 1960 to 1986, including Granduc Mines Ltd, Esso Minerals Canada Ltd, Newhawk Gold Mines Ltd and Lancana Mining Corp. In 1985, Granduc, Newhawk and Lancana formed a three way joint venture, the Newcana JV. Between 1986 and 1991, that JV spent ~CAD 21 million developing the West Zone and other smaller precious metal veins, mainly by underground drilling and drives. This work resulted in the discovery of more than 40 additional showings and the outlining of a historical mineral reserve for the West zone of 0.75 Mt @ 15.4 g/t Au, 678 g/t Ag. The JV sold parts of their holding in the district (including the Sulphurets Zone) to Placer Dome Inc. in 1992, but retained the West Zone and intermittently continued exploration. In 1999, Silver Standard Resources Inc. acquired the interests of the Newcana JV and by 2001 controlled the titles over the Brucejack deposit area. No exploration or development work was carried out between 2001 and 2008, but in 2009 Silver Standard resumed exploration to test for additional bulk tonnage resources on the Brucejack Property. This work included 12 drillholes targeted on what would become the Valley of the Kings Zone to the south of the West Zone. Significant intersections included 1.5 m @ 16 948.5 g/t Au; 0.5 m @ 5344 g/t Au; 1.5 m @ 184.5 g/t Au; 1.5 m @ 51.1 g/t Au; 1.5 m @ 47.5 g/t Au; and 1.5 m @ 46.1 g/t Au. A pre-feasibility study was commissioned in 2010, which recommended continuation to the next phase. In 2010, the interests of Silver Standard Resources were transferred to Pretium Resources Inc. Additional exploration continued, followed by a positive feasibility study in 2014, construction between 2014 and 2017, and commercial production commencing in July 2017. In November 2021, Newcrest Mining agreed to acquire Pretium Resources Inc., including 100% of the Brucejack operation.
Brucejack is a high-grade underground gold-silver mine. It is interpreted to be a deformed, transitional, porphyry-related to intermediate sulphidation high grade epithermal gold-silver deposit, a sulphide-rich sub-type of carbonate-base metal-gold deposits. It is developed within a well mineralised, north-south 'gossanous trend', the 'Sulphurets Mineral District' that coincides with a regional unconformity and a suite of proximal mineralised Early Jurassic porphyry intrusions that occur on the eastern limb of a north-plunging structure known as the 'McTagg Anticlinorium'. Mineralisation is interpreted to have been deposited between 184 to 183 Ma in an active intra-oceanic island arc regime. As of 2020, economic resources/reserves have been defined, and are being mined, in two areas, the West and the Valley of the Kings zones. The two zones are separated by a set of NW-SE trending, SW dipping and SW side down faults and conceivably may represent a deeper and more shallow section of the same mineralised zone.
Regional Setting
The Brucejack deposit is located within the western Stikine Terrane, the largest and westernmost of several exotic terranes that constitute the Intermontane Belt of the Canadian Cordillera (Monger and Price 2002). It is interpreted to represent a Mid-Palaeozoic to Mid-Jurassic intra-oceanic island arc terrane, that was accreted to the North American continental margin at ~173 Ma (Nelson and Colpron 2007; Evenchick et al., 2007; Gagnon et al., 2012). Western Stikinia was subsequently subjected to thin-skinned deformation during the Cretaceous accretion of the outboard Insular Belt terranes at ~110 Ma (Evenchick 1991; Kirkham and Margolis 1995). For an overview of the location and setting of the Intermontane Belt and Insular Belt terranes, Click here. Brucejack is located close to the western margin of the Intermontane Belt, in the centre of the lateral NW-SE extent of the belt.
Mineralisation is localised in the northern section of what is known as the NW-trending Stewart-Iskut Culmination, represented by the north-plunging McTagg Anticlinorium. This culmination is a major structural feature in western Stikinia and lies between the Stikine and Skeena Arches to the west of the Bowser Basin. This culmination has been variously interpreted as i). a structural culmination that developed in response to the Cretaceous deformation, or alternatively, as ii). an Early Jurassic structural highland upon which rocks of the Hazelton Group were deposited prior to Stikinia being accreted to the continent (Nelson and Kyba 2014). This culmination hosts a particularly metal-rich assemblage of volcano-sedimentary and related comagmatic plutonic rocks of the Triassic Stuhini and latest Triassic to Middle Jurassic Hazelton Groups (Nelson et al., 2013), containing >70 documented mineral occurrences and showings, including: i). structurally-controlled high-potassic calc-alkaline porphyry copper-gold deposits (e.g., Kerr, Sulphurets, Mitchell, Iron Cap, Snowfield of the Iskut River District), ii). transitional epithermal intrusion-related precious metal deposits (e.g., Brucejack, Silbak-Premier, Big Missouri, Red Mountain and Homestake Ridge), and iii). volcanogenic massive sulphide deposits (e.g., Granduc, Dolly Varden-Torbrit, Anyox and Eskay Creek). These deposits are interpreted to have been developed while Stikinia was in a state of compression or sinistral transpression (Nelson and Colpron 2007).
As detailed above, the Brucejack Deposit lies on the eastern limb of the north-plunging McTagg Anticlinorium. The core of the structure is occupied by arc-related volcanic rocks of the Triassic Stuhini Group, and progress successively outwards through arc-related volcanic rocks of the Jurassic Hazelton Group and then clastic basin-fill sedimentary sequences of the Middle Jurassic to Lower Cretaceous Bowser Lake Group. A major unconformity separates the Stuhini and Hazelton Group rocks. At Brucejack, the host sequence is tilted with a generally progressive younging towards the east.
Both Brucejack and the neighbouring Kerr-Sulphurets-Mitchell deposits have a strong spatial association with the unconformity between the Stuhini and Hazelton Group rocks, and with north-south structures to the east of this contact. These relationships are interpreted to suggest these features were relavent to formation of the deposits (Nelson and Kyba 2014). This conclusion is further supported by the association between numerous other Triassic to Jurassic mineral showings and porphyry copper-gold deposits throughout northwestern British Columbia with this same unconformity (Kyba 2014; Nelson and Kyba 2014).
The Kerr-Sulphurets-Mitchell porphyry Cu-Au-Mo deposits are associated with the Mitchell Suite intrusive rocks of the Texas Creek Intrusive Suite (Kirkham and Margolis 1995). They are broadly contemporaneous and have a similar mineralogy, alteration and textures (Campbell and Dilles, 2017). The Mitchell Suite intrusions have large areas of associated internal and surrounding hydrothermal alteration, with overprinting alteration relationships indicating magmatic-hydrothermal systems that underwent telescoping as they evolved between about 196 and 190 Ma (Campbell and Dilles, 2017). Early potassic alteration was syn-mineral and is locally overprinted by propylitic, albitic and chlorite-sericite assemblages, prior to being pervasively overprinted by a phyllic quartz-sericite-pyrite alteration event. The final stage of telescoping included local advanced argillic alteration and massive pyrite vein emplacement, overprinting earlier assemblages before being overprinted by high-level gold-rich veins (Campbell and Dilles 2017).
West-vergent thrusts and overturned folds affected the western limb of the anticlinorium, whilst on the eastern limb, east- to SE-directed thrusts and east-vergent overturned folds are evident (Kirkham and Margolis 1995). These structures are the result of the mid-Cretaceous Skeena Fold and Thrust Belt. In addition to thrusting, the McTagg Anticlinorium is cut by late-stage brittle faults that are likely of Tertiary age, representing reactivated older structures (e.g., the north-trending Brucejack Fault; Nelson and Kyba 2014). Penetrative foliation of variable orientation is preferentially developed in altered Hazelton Group rocks in the Sulphurets Mineral District, with an intensity proportional to the mica and/or clay mineral content (Kirkham and Margolis 1995). Timing of this penetrative fabric is most commonly considered to have been in response to the Late Jurassic to mid-Cretaceous Skeena Fold and Thrust Belt deformation related to the Insular Belt collision (Kirkham and Margolis 1995; Nelson and Kyba 2014). The regional sub-greenschist facies metamorphism associated with this deformation was at maximum temperature-pressure conditions of ~290°C and 4.5 Kbar, respectively, corresponding to thermally reset potassium-argon (K-Ar) and argon-argon (Ar-Ar) ages for foliation-parallel sericite in older porphyry-related phyllic alteration zones at ~110 Ma (Alldrick 1993; Kirkham and Margolis 1995).
Local Geology
The Brucejack mineralisation is predominantly hosted by volcano-sedimentary rocks of the Lower Jurassic Hazelton Group which unconformably overlie volcanic arc sedimentary rocks of the Upper Triassic Stuhini Group that are exposed along the western-most part of the deposit area. The principal lithologies within the deposit area, including those hosting mineralisation, are characterised by a ~195 to 188 Ma (U-Pb zircon) basal marine volcano-sedimentary package unconformably overlain by an ~188 and 185 Ma immature polylithic volcanic conglomerate that grades upward through a sandy epiclastic unit into a predominantly pyroclastic trachyandesite (latite) fragmental unit (Board et al., 2020). This sequence comprises a relatively complex volcanic stratigraphy characterised by rapid lateral facies changes, and defines a general younging upward and to the east. The sequence is interpreted as having been deposited in a series of small fault-bounded half-grabens on the eastern side of the Brucejack Fault.
The Brucejack Fault is the largest of numerous north-south lineaments that occur in the Brucejack deposit area. It is interpreted as the latest expression of a reactivated growth fault that was active during Early Jurassic volcanism and mineralisation. The most recent movement on this fault in the deposits area is dextral and east side down, with displacement in the order of tens of metres. It marks a significant change in thickness of the lowermost units of the Hazelton Group (Jones 2014; Tombe et al., 2018); the development of small secondary half-graben structures on its eastern side; rapid facies variations, and has been a focus of alteration and mineralisation along its entire 11 km strike length.
The host lithologic sequence at Brucejack is bounded to the south and NW by massive, relatively fine-grained plagioclase feldspar ±K feldspar ±hornblende-phyric rocks (the P1 porphyry phase), particularly the ~ 194 Ma Office and ~189 Ma Bridge Zone porphyries. The Bridge Zone porphyry is immediately SW of the Valley of the Kings Zone mineralisation whilst the Office Zone porphyry forms a wedge between that mineralised zone and the West Zone. These porphyry bodies have sharp contacts with, and very similar ages to, the volcaniclastic rocks and have been variously interpreted as comagmatic subvolcanic/hypabyssal monzonitic intrusions or latite flows (Kirkham and Margolis 1995; Jones 2014). The coarser-grained P2 feldspar-hornblende-phyric porphyry is locally present within the sequence, especially to the north and east of West Zone. East of the Brucejack Deposit, in the Flow Dome Zone, the lithologic sequence is overlain by a felsic unit that includes K feldspar ±plagioclase ±hornblende-phyric flows, breccia, bedded non-welded and welded felsic tuffs, and a comagmatic intrusion which is flow-banded and plagioclase-hornblende phyric (Macdonald 1993). This flow-dome complex, represents a high-level intrusive and extrusive parts of a local magmatic centre.
Hydrothermal breccia bodies occur throughout the lower Hazelton Group in the Brucejack area, following faults and fractures. They are generally composed of angular to subrounded, 2 to 15 cm wide, heterolithic, commonly immediate wall-rock clasts, set in a fine-grained matrix of rock flour and pyrite. Hydrothermal breccia bodies cut all host-rock units and are discordant to the penetrative foliation. Mineralised veins cut and are cut by breccia bodies and hydrothermal breccia grades into mineralised manganese-carbonate veins, suggesting that the breccia bodies are syn-mineralisation in timing.
All lithological units, mineralised veins and vein stockwork in the deposit area are cut by relatively uncommon, post-mineralisation, but altered, amygdaloidal intermediate to mafic dykes (Tombe et al. 2018). In the Valley of the Kings Zone, these dykes are subvertical, up to 1.5 m wide, and commonly east- to SE-trending, with a strike length of at least 900 m, extending for >1000 m down dip. Dykes in the West Zone trend NW-SE, have strike lengths of at least 500 m, and extend for more than 450 m down dip. These dykes follow faults and fractures in a staggered zig-zag patterns, having been emplaced along variably oriented structures during local extension, and partially utilise the same structures as the mineralised veins. They are interpreted to have been emplaced during a period of rifting that post-dated epithermal mineralisation and are un-related to gold mineralisation. A later set of north-south trending, undeformed, and unaltered mafic dykes that may be up to several metres wide, are found to the west of and along the Brucejack Fault, but are rare in the deposit area, and are geochemically distinct from the post-mineralisation intermediate to mafic dykes (Tombe 2015).
Mineralisation and Alteration
A north-south trending, generally slightly arcuate, west concave, 0.5 to 1.5 km wide band of variably phyllic-altered rocks and associated quartz stockwork veining extends over a strike length of ~5 km in the deposit area. This band straddles the Brucejack Fault, migrating from the west side in the north, to east side further south. The phyllic alteration typically contains between 2 and 20% pyrite, affects rocks throughout the lithological sequence, and, depending on the alteration intensity, can obliterate texture and render protoliths unrecognisable. More than 40 mineralisation showings, associated with this alteration band, have been outlined at Brucejack (McPherson 1994). At least ten mineralised zones have been recognised in the Brucejack deposit area, extending from the Hanging Glacier Zone in the north to the Bridge Zone in the south. Five of these zones have been tested to 2020, namely the West Zone, Valley of the Kings Zone, Bridge Zone, Gossan Hill Zone and Shore Zone, with mining focused on the first two.
Phyllic alteration dominates at Brucejack, and is typically a fine-grained admixture of white mica, pyrite, quartz and calcite that replaces the matrix of the volcano-sedimentary sequence, varying in intensity from trace to complete replacement. Relicts of earlier potassic, albitic and propylitic alteration are locally preserved in the intense phyllic altered rocks, consistent with a regime of overprinting and telescoping. Molybdenite mineralisation associated with the Bridge Zone P1 porphyry was formed between about 190 and 189 Ma, very similar in age to the P1 porphyry, and may represent an early overprinted event. Weak silicification has affected most of the host lithologic units in the deposit area, with local moderate to intense texture destruction. Pod-like zones of intense silicification that are metres- to tens of metres across are commonly developed in the polylithic conglomerate (especially at its upper and lower contacts) and locally in rocks of the underlying basal marine volcano-sedimentary package. These zones of intense silicification are composed of microcrystalline quartz, pyrite and sericite, and are associated with bands of massive pyrite and almost monomineralic green muscovite. Irregular stockworks of un-mineralised cloudy to translucent quartz veinlets of varying intensity are limited to the more intensely silicified zones. Hairline, clear, crack-seal quartz veinlets are locally present in the hardest and most intensely silicified zones, possibly reflecting local fluid overpressured zones developed beneath these impermeable features. Cross-cutting relationships suggest the phyllic and silica alteration predated all stages of electrum mineralisation (Tombe et al., 2018), and that pyrite, sericite and the silicified zones were coeval. Mineralised veins and 183 Ma intermediate to mafic dykes are generally spatially associated with the phyllic assemblage, suggesting that these structures preferentially utilised pre-altered zones.
Mineralised veins in the Brucejack Deposit cut the host 188 to 184 Ma volcano-sedimentary sequence, including rocks as young as 184 Ma, and are cut by the 183 Ma intermediate to mafic dykes. This indicates an age of about 184 to 183 Ma for the precious metal mineralisation, much later than the 195 to 188 Ma host volcano-sedimentary rocks and P1 porphyries.
Visible gold and silver mineralisation occurs as electrum, and is predominately hosted in quartz-carbonate to carbonate vein and vein breccia structural corridors, within broader stockwork zones (McPherson 1994; Kirkham and Margolis 1995; Tombe et al., 2018). Low-grade (i.e., <5 g/t), sub-microscopic gold mineralisation is found in vein- and wall rock-hosted arsenian pyrite throughout the Valley of the Kings Zone and possibly within the West Zone as well. Electrum-bearing quartz-carbonate veins and stockwork overprint and are co-spatial with earlier porphyry-related phyllic alteration in the Brucejack Deposit.
Valley of the Kings Zone
This zone, which is ~500 m south of the West Zone, has been defined over a 1200 x 700 m, WNW-ESE elongated interval and traced to a depth of ~650 m, although deep drilling suggests alteration and mineralisation persists to a depth of at least 1100 m. The host sequence forms a broad syncline in which fragmental volcanic and clastic sedimentary rocks, along with minor Upper Triassic to Lower Jurrassic flows appear to plunge moderately to the east. Variably altered hornblende-feldspar-phyric volcanic rocks of intermediate composition are interpreted to represent the youngest rocks of the sequence in this zone, and outcrop to the south, west and to the NW, whilst broadly equivalent coarse pyroclastic rocks, including common lapilli tuff and tuff breccia, may occupy the core of the syncline. These are underlain by interbedded immature volcanic-derived sedimentary rocks, including common pebble and cobble conglomerate and pebbly sandstone. The sedimentary sequence is considered to be a correlate of the basal Jack formation of the Hazelton Group. Generally thin, and likely discontinuous rhyolite flows, as well as local siliceous sinters have been mapped at surface and logged in drill core in the vicinity of the contact. The rhyolite is underlain by a relatively thick and generally poorly stratified sequence of fine-grained concretion-bearing mudstone and siltstone with locally interbedded immature but locally-derived sandstone and pebble conglomerate.
Six stages of veining have been recognised (after Shaw et al., 2020):
Stage I - discontinuous, deformed and variably oriented pyrite-quartz-calcite stringer veinlets that are widespread in zones of phyllic alteration, possibly representing D-type veinlets associated with early porphyry-style alteration. Individual veins have millimetric thicknesses and centimetre scale continuity, and carry pyrite that contains invisible gold, accompanied by traces of chalcopyrite, set in a pyrite-quartz-calcite-sericite ±chlorite gangue (Tombe et al., 2018);
Stage II - translucent to white, discontinuous, microcrystalline quartz-pyrite veins and veinlets, occurring exclusively within pervasively silicified rocks. Stage I and II veins are pre-mineral with respect to precious metal mineralisation, and are always cut by electrum-bearing epithermal veins;
Stage III - quartz-carbonate veins carrying electrum. These veins increase in abundance at depth, to the west, and to the east. Three subsets are recognised:
Sheeted veinlets that are centimetric in thickness and tens of metres in length, containing electrum and traces of sphalerite ±galena ±chalcopyite in a gangue of pyrite-quartz-calcite-dolomite ±sericite ±rutile;
Breccia/flooded zones that are centimetric to tens of centimetres in thickness and metres in length, again with electrum and traces of sphalerite ±galena ±chalcopyite in a gangue of pyrite-quartz-calcite-dolomite ±sericite ±rutile;
Stockwork veins and blows that are tens of cm to metres in thickness and tens to hundreds of metres long, carrying electrum and traces of sphalerite ±galena ±chalcopyite and traces of silver sulphosalts in a gangue of pyrite-quartz-calcite-dolomite ±sericite ±arsenopyrite ±rutile;
Stage IV - base metal sulphide-quartz-carbonate veining, with individual veins being centimetres to tens of cm in thickness and continuities of metres to tens of metres. Mineralisation includes sphalerite-galena-chalcopyite-electrum-silver sulphosalts, with the latter including acanthite, pearcite, pyrargyrite, freibergite, proustite, polybasite and argentotennantite. The gangue assemblages comprises pyrite-quartz-calcite-dolomite ±sericite ±arsenopyrite ±rutile;
Stage V - manganoan calcite sheeted veinlets, veins, vein breccia and vein stockworks, with electrum and traces of chalcopyrite in a gangue of calcite-quartz-pyrite ±rutile. Stages III to V veins are considered to have been coeval, as they have complex multiple overprinting relationships. They are locally un- to weakly-deformed, but have pinch-and-swell textures in high strain zones. Stage III and IV veins have classic epithermal vein textures, including crustiform banding, sparse cockade textures, whilst vugs are locally present (Tombe et al., 2018);
Stage VI - barren, thrust-related quartz-calcite-chlorite veins and tension gashes, which cut all earlier vein generations and are likely mid-Cretaceous in age (Tombe et al., 2018).
In all of the mineralised vein stages, electrum occurs in a variety of textures, including: i). common fine- to coarse-grained dendrites, ii). lesser coarse subhedral clots and aggregates; and iii). uncommon fine- to medium-grained, subhedral to euhedral sheet- to plate-like crystals. The gold/silver ratio of the electrum varies significantly, with each of the three main mineralised vein stages displaying unique gold/silver signatures, ranging from 30 to 70% Au. Stage V veins typically contain electrum with the highest proportion of gold, whereas Stage IV veins contain predominantly silver-rich electrum that is locally chemically zoned (gold-rich cores surrounded by silver-rich rims; McLeish et al., 2018). However, there does not appear to be any significant compositional zonation of electrum as a function of spatial location (Shaw et al., 2020).
West Zone
As known in 2020, this zone had a >590 m NW trending strike extent, was 560 m wide, and persisted to 650 m in depth. It is hosted by a north-westerly trending band of intensely altered Lower Jurassic latitic to trachyandesitic volcanic and subordinate sedimentary rocks that are as much as 400 m to 500 m in thickness, separating two more competent bodies of hornblende, plagioclase and hornblende-phyric flows. The stratified rocks dip moderately to steeply to the
NE and are intensely altered, particularly in the immediate area of the precious metals mineralisation. The mineralised zone comprises at least 10 quartz veins and mineralised quartz stockwork ore shoots, the longest of which has a strike length of ~250 m and a maximum thickness of about ~6 m. The West Zone is marked by a central silicified core that passes outwards to a zone of sericite ±quartz ±carbonate and then to an outer halo of chlorite ±sericite ±carbonate. The combined thickness of the alteration zones across the central part of the deposit is 100 to 150 m.
Drilling has indicated mineralisation and vein parageneses broadly similar to that described above for the Valley of the Kings Zone, with two notable exceptions: i). ore stage veins have a lower modal abundance of electrum and higher modal abundance of base metal sulphide and silver sulphosalt minerals, resulting in a lower gold/silver ratio, and ii). the mineralogy of pre-mineralisation-stage veining in the West Zone is different to that of the Valley of the Kings Zone, with Stage I veinlets being represented by potassium feldspar-quartz veinlets (Shaw et al., 2020). The electrum mineralisation is associated with, in decreasing order of abundance, pyrite, sphalerite, chalcopyrite and galena. Besides being found with gold in electrum, silver occurs in tetrahedrite, pyrargyrite, polybasite and, rarely, stephanite and acanthite. Gangue mineralogy of the veins is dominated by quartz, with accessory adularia, albite, sericite, and minor carbonate and barite.
Reserves and Resources
Mineral Resources and Ore Reserves after Pretium Resources Inc. Technical Report, 2020.
Valley of the Kings Zone
Mineral Resources as at 1 January 2020 were:
Measured Resources - 2.3 Mt @ 10.5 g/t Au, 12.6 g/t Ag;
Indicated Resources - 16.1 Mt @ 11.4 g/t Au, 12.2 g/t Ag;
Measured + Indicated Resources - 18.4 Mt @ 11.3 g/t Au, 12.2 g/t Ag, for 208 t of gold and 225 t of Ag;
Inferred Resources - 5.4 Mt @ 13.3 g/t Au, 15.9 g/t Ag, for 72 t of gold and 86 t of Ag.
Ore Reserves as at 1 January 2020 were:
Proved Resources - 1.4 Mt @ 8.9 g/t Au, 11.1 g/t Ag;
Probable Reserves - 11.3 Mt @ 8.7 g/t Au, 9.8 g/t Ag;
Proved + Probable Reserves - 12.8 Mt @ 8.8 g/t Au, 10.0 g/t Ag, for 112 t of gold and 127 t of Ag.
West Zone
Mineral Resources as at 1 April 2012 (pre-mining) were:
Measured Resources - 2.4 Mt @ 5.9 g/t Au, 347 g/t Ag;
Indicated Resources - 2.5 Mt @ 5.9 g/t Au, 190 g/t Ag;
Measured + Indicated Resources - 4.9 Mt @ 5.9 g/t Au, 267 g/t Ag, for 29 t of gold and 1305 t of Ag;
Inferred Resources - 4.0 Mt @ 6.4 g/t Au, 82 g/t Ag, for 25 t of gold and 329 t of Ag.
Ore Reserves as at 1 January 2020 were:
Proved Resources - 1.4 Mt @ 7.2 g/t Au, 383.0 g/t Ag;
Probable Reserves - 1.5 Mt @ 6.5 g/t Au, 181.0 g/t Ag;
Proved + Probable Reserves - 2.9 Mt @ 6.8 g/t Au, 278.5 g/t Ag, for 19 t of gold and 806 t of Ag.
Combined
Mineral Resources as at 1 January 2020 were:
Measured + Indicated Resources - 23.2 Mt @ 10.1 g/t Au, 65.5 g/t Ag, for 234 t of gold and 1520 t of Ag;
Inferred Resources - 9.4 Mt @ 10.3 g/t Au, 44.3 g/t Ag, for 97 t of gold and 416 t of Ag.
Ore Reserves as at 1 January 2020 were:
Proved + Probable Reserves - 15.7 Mt @ 8.4 g/t Au, 59.6 g/t Ag, for 132 t of gold and 936 t of Ag.
The information in this summary is largely drawn from: Shaw, A,. Boese, C., Fraser, C., Ghaffari, H., Jones, I.W.O., Huang, J., Findlater, L.-L., Phifer, M., Herrera, M., Schmitt, R. and Coleman, T., 2020 - Technical Report on the Brucejack Gold Mine, Northwest British Columbia; prepared by Tetra Tech Canada Inc., for Pretium Resources Inc., March, 2020, 383p. and
Armstrong, T., Brown, F., Puritch, E. and Vallat, C., 2011 - Technical report and resource estimate on the Brucejack Project Skeena Mining Division British Columbia, Canada; prepared by P & E Mining Consultants Inc., for Pretium Resources Inc., November 28, 2011, 170p.
The most recent source geological information used to prepare this decription was dated: 2020.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Brucejack
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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