The Sulphurets zone is located above the north side of Sulphurets Glacier. The zone occurs within massive andesite of the Lower Jurassic Unuk River Formation, Hazelton Group. It occurs below the Sulphurets fault and above a complex parallel fault set. Large bodies of Jurassic Monzonite to Quartz Monzonite occur to the northwest and southwest of the zone.

The Sulphurets deposit (or Sulphurets Gold zone) formed in a high level, transitional porphyry copper-gold system that was thrust over the deeper levels of a syenite-centered porphyry copper-gold deposit (Main Copper zone) along the Sulphurets Thrust Fault (STF). Volcanic sequences on either side of the thrust have been assigned to Hazelton Group. Generally, in areas of intense alteration and mineralization, the protolith cannot be assigned accurately. Late hornblende phyric monzonite to monzogabbro dikes and sills intrude the area.

The Sulphurets zone is a northeast trending zone, over 1.5 kilometres in length, that forms a broad halo around the west, south, and east sides of the Main Copper deposit; a zone discovered by Granduc Mines Limited in the early 1960s. The Main Copper deposit is described in Assessment Report 8420 as "an extensive area of quartz-albite-pyrite rock and moderately altered quartz-albite-pyrite-chalcopyrite rock. Both apparently hydrothermal alteration products of intermediate volcanics intruded by syenite and granite". Bornite is also reported to occur.

The Sulphurets Gold zone is centered along a zone of strong faulting and phyllic-quartz-sericite-pyrite, intermediate argillic, and potassium silicate alteration. Copper-gold mineralization is usually coincident with areas of strongest fracturing and potassium silicate alteration. Late, auriferous hydrothermal breccias constitute the Breccia Gold zone.

Above the STF in the Main Copper Zone, intermediate volcanics are intruded by feldspar porphyry quartz syenites and potassic monzonite dikes. Rocks in the periphery of the dikes are K-feldspar altered and contain disseminated and fracture-controlled chalcopyrite with lower Cu and Au grades than the Sulphurets Zone. The dikes are grouped with the Mitchell intrusions that correlate with late Jurassic Texas Creek intrusions common throughout the region.

The Sulphurets Zone is comprised of two distinct zones—Raewyn and Breccia Gold. The Raewyn Copper-Gold Zone hosts mostly porphyry-style disseminated chalcopyrite and associated gold mineralization in moderately quartz stockwork, chlorite-biotite-sericite-magnetite altered sediments and volcanics. The alteration and mineralization are centred on meter scale; sills and dykes of altered porphyritic diorite are believed to tap a stock at depth. It has an apparent north-northeast strike and dips about 45 degrees to the northwest, with approximate true dimensions of 1,000 metres in strike, 550 metres down dip, and up to 250 metres in thickness. It remains open down dip and along strike to the northeast at depth. It may be offset in an echelon style by several north-northeast trending vertical structures. The mineralization is open down-dip. It crops out at surface on the cliff face above Sulphurets Lake and its upper surface follows or is clipped by the STF. The Breccia Gold Zone hosts mostly gold-bearing pyritic mineralization with minor chalcopyrite and sulfosalts in a potassium-feldspar-siliceous hydrothermal breccia that apparently crosscuts the Raewyn Zone. It comprises altered intrusive clasts in a matrix of mainly silica, potassium-feldspar and sulphides. An intense structurally controlled phyllic overprint nearly masks all earlier alteration phases over parts of the zone. Above the STF, low-grade, but widespread disseminated copper-gold mineralization, occurs in hornfels and skarn sediments and volcanics that have been intruded by a non-mineralized porphyritic monzonite. This is referred to as the Main Copper Zone, and it makes up less than 5 per cent of the Sulphurets Resource.

WORK HISTORY (a combined Sulphurets, Mitchell and Iron Cap zones work history is taken from the 2016 Seabridge Prefeasibility Study. Other sources are given below.)

From 1880 to 1933, limited placer gold exploration and mining occurred. From 1935 to 1959, placer gold prospecting, prospecting and staking of mining claims occurred. From 1959 to 1960, Newmont and Granduc conducted surveys including airborne mag. Sulphurets and Iron Cap Au zones discovered. D. Ross, S. Bishop, and W. Dawson prospected and stake claims in area.

From 1961 to 1968, Granduc conducted geological and geochemical surveys and drilled 9 holes into the Sulphurets Zone. The Ross-Bishop-Dawson claims were optioned by Phelps Dodge in 1962, Meridian Syndicate in 1965, and Granduc in 1968.

In 1963 R. Kirkham completed a M.Sc. thesis on the geology of Mitchell and Sulphurets areas. In 1981 T. Simpson completed a M.Sc. thesis on the geology of the Sulphurets gold zone.

From 1971 to 1977, Granduc conducted additional exploration surveys targeting molybdenum and drilled 6 holes into the Snowfield Zone (Bruceside).

From 1979 to 1984, Esso Minerals optioned Sulphurets Property and completed early-stage exploration including drilling 2,275 metres in 14 holes. In the Main Copper Zone about 0.69 gram per tonne gold accompanies 0.55 per cent copper (Bridge et al, 1981). From 5 drill holes completed on the Breccia zone an ore reserve of 20,000,000 tonnes grading 1.71 grams per tonne gold was inferred (Property File - Esso Minerals Canada (Unpublished Report), Bridge and Melnyk, 1982).

From 1985 to 1991, Granduc optioned Sulphurets to Lacana (later Corona) and Newhawk. Lacana-Newhawk joint venture spent approximately $21 million developing West Zone and other smaller precious metal veins on the Bruceside Property. They drilled 11 holes at Sulphurets. Sulphurets rock samples assayed as high as 5.28 grams per tonne gold (grab) and 2.95 and 3.33 grams per tonne gold over 3 metres (Northern Miner October 17, 1988).

Homestake undertook exploration after acquiring Corona. In 1991, the Arbee prospect was optioned by Newhawk from D. Ross.

In 1992, the Arbee prospect was optioned by Placer Dome from Newhawk. From 1991 to 1992 Newhawk commissioned a geophysical survey over Sulphurets. Newhawk subdivided the Sulphurets Property into Sulphside and Bruceside. Placer Dome acquires Sulphside (Sulphurets, Mitchell, Iron Cap, and other prospects). In 1992, Placer Dome undertook delineation drilling of Sulphurets deposit at 50 metre centres (23 holes).

In 1993 J. Margolis completed a Ph.D. thesis on the Sulphurets district. Newhawk-Corona drilled 3 holes in the Snowfields and Josephine zones east of Sulphurets.

From 1992 to 1996 Placer Dome completed geologic modeling, resource estimation (not NI 43-101 compliant), preliminary metallurgical test work, and scoping studies.

In 1999, Silver Standard Resources Inc. acquired Newhawk. From 1996 to 2000, the Sulphurets project was dormant.

In 2000, Seabridge acquired a 100 per cent interest in the Sulphurets/Mitchell properties from Placer Dome. In 2002, Noranda acquired an option to earn up to 65 per cent from Seabridge. From 2003 to 2004, Noranda undertook various exploration surveys. At Sulphurets, Placer Dome has estimated a total measured, indicated and inferred gold resource of 54.8 million tonnes grading 1.02 grams of gold per tonne, at a 0.50 gram per tonne cut-off (Press Release, Seabridge Resources Inc., June 6, 2000; Northern Miner, June 26, 2000). Approximately 72 per cent of the total gold resource is within 50 metres of a drill intercept and has been classified by Placer Dome as drill-indicated. The Sulphurets gold zone is the collective name for at least four intrusive centered gold-rich zones spanning approximately three kilometres of strike length. The resource calculations made by Placer Dome were confined to 1,000 metres of the three-kilometre strike length.

In 2005, Falconbridge Limited completed 4092 metres of drilling in 16 holes, distributed over six zones, one of them being the Main Copper in which 3 holes were drilled. At the Main Copper zone, mineralization is associated with potassic altered monzonitic porphyries which intrude quartz-chlorite-magnetite altered volcanics. Rock chip samples collected by Noranda over a 1300 by 700 metre area returned from 0.42 to 1.68 per cent copper and 0.3 to 1.1 grams per tonne gold (Press Release, Seabridge Gold Inc., July 25, 2005). The southeast slope of the Main Copper zone is well exposed, and exhibits strong chlorite-magnetite alteration, and widespread malachite and chalcopyrite mineralization. The zone lies north of the Sulphurets fault, with the Sulphurets deposit occurring immediately to the south. Immediately east of the Main Copper zone, a second area of mineralization was discovered by Noranda where melting of thin glacial ice and snowfields has exposed new outcrop. Disseminated chalcopyrite, minor pyrite and trace molybdenite occur in intensely silicified rocks and hydrothermal breccias similar to the Sulphurets deposit. Ten rock chip samples collected by Noranda over a 200 by 200 metre area averaged 0.41 per cent copper and 0.6 gram per tonne gold (Press Release, Seabridge Gold Inc., July 25, 2005). Falconbridge refers to this area as Icefield, and reports that the zone may potentially extend under remaining thin ice cover for several hundred metres to the north and east.

The eastern section of the Sulphurets zone was previously called the Breccia zone. In this zone the best gold values were derived from andesitic breccias, having quartz-pyrite-K-feldspar and minor sericite-chlorite alteration. The greater the silicification the greater the gold content. The western extension of the Breccia zone was called the Canyon Zone where gold occurs in andesite with quartz-pyrite-sericite alteration with the addition of quartz veins.

In 2006, Seabridge purchased Falconbridge's option and drilled 29 holes totalling about 9,129 metres at the Sulphurets and Mitchell zones. In 2007, Seabridge purchased Arbee prospect from D. Ross and drilled 37 holes totalling 15,650 metres.

In February 2008, a mineral resource of 74.655 million tonnes indicated grading 0.75 gram per tonne gold and 0.24 per cent copper and 33.636 million tonnes inferred grading 0.62 gram per tonne gold and 0.20 per cent copper was reported, using a 0.50 gram per tonne gold cut-off grade, for the Sulphurets deposit (Lechner, M.J. (2008-02-29): Kerr-Sulphurets Technical Report).

In 2008, Seabridge drilled 37 holes totalling 17,192 metres, started metallurgical testing, obtained new topographic data, and initiated permit related activities. In 2009, Seabridge drilled 11,843.8 metres (resource definition, geotechnical and water monitoring), conducted metallurgical testing, and intensified permit data collection.

In March 2009, an updated mineral resource of 87.300 million tonnes indicated grading 0.72 gram per tonne gold and 0.27 per cent copper with an additional 160.900 million tonnes inferred grading 0.63 gram per tonne gold and 0.17 per cent copper was report, using a 0.50 gram per tonne gold equivalent cut-off grade, for the Sulphurets deposit (Lechner, M.J. (2009-03-30): Updated KSM Mineral Resources).

In January 2010, an updated mineral resource of 159.000 million tonnes indicated grading 0.63 gram per tonne gold and 0.28 per cent copper with an additional 144.000 million tonnes inferred grading 0.50 gram per tonne gold and 0.16 per cent copper was report, using a 0.50 gram per tonne gold equivalent cut-off grade, for the Sulphurets deposit (Lechner, M.J. (2010-01-25): January 2010 Updated KSM Mineral Resources).

In 2010, Seabridge drilled 86 holes totalling 26,755.7 metres (resource definition and geotechnical), conducted metallurgical testing, and intensified permit data collection. In 2010 Seabridge Gold released updated reserves for the KSM property. Probable reserves for the Sulphurets Zone are 142.2 million tonnes grading 0.61 gram per tonne Au, 0.28 per cent Cu, 0.44 gram per tonne Ag, and 0.01018 per cent Mo (Stockwatch News Release March 31, 2010).

In March 2011, an updated mineral resource of 199.300 million tonnes indicated grading 0.63 gram per tonne gold, 0.26 per cent copper, 0.7 grams per tonne silver and 0.006 per cent molybdenum with an additional 160.500 million tonnes inferred grading 0.53 gram per tonne gold, 0.16 per cent copper, 1.1 grams per tonne silver and 0.003 per cent molybdenum was reported, using a 0.50 gram per tonne gold equivalent cut-off grade, for the Sulphurets deposit (Lechner, M.J. (2011-03-29): March 2011 Updated KSM Mineral Resources).

In 2011, Seabridge drilled 54 resource definition holes totalling 18,087.2 metres, continued prefeasibility-level work and completed magneto-telluric geophysical surveys.

A July 24, 2012, updated resource estimate for the Sulphurets deposit at 0.50 gram per tonne gold equivalent cut-off grade is reported as follows: Measured plus Indicated - 370,900,000 tonnes grading 0.59 gram per tonne gold, 0.21 per cent copper, 0.8 gram per tonne silver and 0.0049 per cent molybdenum; Inferred - 177,100,000 grading 0.50 gram per tonne gold, 0.15 per cent copper. 1.2 grams per tonne silver and 0.0030 per cent molybdenum follow (www.seabridgegold.net).

In 2012, Seabridge drilled 25 holes totalling 15,452.85 metres. In 2013, Seabridge drilled 11 holes totalling 8,857.4 metres, completed induced polarization and downhole geophysical surveys. In 2014, Seabridge drilled 13 holes totalling 13,601.25 metres, completed magneto-telluric and gravity geophysical surveys. In 2015, Seabridge drilled 8 holes totalling 4,581.1 metres, completed airborne magnetic geophysical survey.

The 2013 program primarily focused on intersecting deep mineralization at the Kerr deposit (29 holes) and the Iron Cap deposit (6 holes). Additional drilling was completed at the Camp and McQuillan targets. No holes were drilled into the Sulphurets deposit in 2013.

The 2014 program focused on exploring the down-dip extension of mineralization below the Kerr Zone (16 holes) and Iron Cap Zone (10 holes). Additional drilling was completed at the Sulphurets Zone (9 holes) and McQuillan Zone (2 holes). In 2014, two holes were collared to the northwest of the Sulphurets deposit and were designed to test for an intrusive source associated with mineralization, but instead encountered intensely metamorphosed sedimentary and volcanic rocks with extensive fracture and vein controlled phyllic and potassic alteration. Long intervals of highly-anomalous gold concentrations were encountered in these drill holes that correspond to the dip projection of the Sulphurets deposit.

In November 2014, an updated mineral resource for the Sulphurets deposit was reported at 370.900 million tonnes indicated grading 0.59 gram per tonne gold, 0.21 per cent copper, 0.8 gram per tonne silver and 0.005 per cent molybdenum with an additional 177.100 million tonnes inferred grading 0.50 gram per tonne gold, 0.15 per cent copper, 1.2 grams per tonne silver and 0.003 per cent molybdenum, using a 0.50 gram per tonne gold equivalent cut-off grade (Huang, J. (2014-11-11): 2012 KSM (Kerr-Sulphurets-Mitchell) Prefeasibility Study).

In 2015, Seabridge drilled nine core holes totaling nearly 14,000 metres. The majority of that meterage was designed to extend the known limits of mineralization beneath the Kerr deposit (6 holes). Three holes (about 5,000 metres) were drilled to test the down-dip projection of mineralization at the Mitchell deposit. No holes were drilled into the Sulphurets deposit in 2015.

In 2016, Seabridge reported that the Sulphurets Open Pit contained 304 million tonnes of ore in the Proven and Probable Reserves category, grading 0.59 gram per tonne gold, 0.22 per cent copper, 0.8 gram per tonne silver and 0.00516 per cent molybdenum (Ghaffari, H. (2016-10-06): 2016 KSM (Kerr-Sulphurets-Mitchell) Prefeasibility Study Update and Preliminary Economic Assessment).

In September, 2018, 5 holes were sited to confirm mineral reserves in those areas where production would likely begin. Drill holes in the Mitchell, Sulphurets and Kerr deposits confirmed block grades comparable with model predictions (Results in Seabridge Gold Inc., News Release, Sept.24, 2018). A total of eight drill holes oriented into the margins of the Mitchell and Sulphurets deposits have been completed and an additional four holes are planned for a total of 4,919 metres. These holes were designed to test an updated block model of waste types on the margins of the deposits. Eight exploration drill holes at Iron Cap have been completed and the final five are in progress, totalling about 16,700 metres of drilling. The exploration drill program was designed to continue testing the core zone of the Iron Cap deposit down-plunge to the west. Initial indications are that the deposit approaches near vertical continuity to depth of at least 1,800 metres. Nine geotechnical drill holes have been completed during the current season, totalling 3,609 metres of drilling. The work focused on evaluating the material properties of fractures and faults on the planned pit high-walls. Results will be used to plan additional work for the Mitchell and Sulphurets deposits.

In 2017, 2018 and 2019, work by Seabridge Gold was focused on Iron Cap (104B 173). See Iron Cap for further details.

Uprgraded resources were released in 2019 for Iron Cap (104B 173) (dated March 7, 2019) and incorporate all previous drilling plus 20,341 metres of diamond core drilling completed in 18 holes during the 2018 program.

During 2018, waste characterization and geotechnical drilling of the proposed Sulphurets pit encountered high grade gold intersections in several holes. After this finding Seabridge found additional such shallow intersections from previous drill campaigns in the same area. It was announced in August 2019 that two core rigs had been mobilized to complete 4,000 meters in 16 shallow holes within the proposed pit of the Sulphurets Deposit (Press Releases, Seabridge Gold (June 18 and August 27, 2019).

See Kerr (104B 191) for details of a 2016 Combined Mineral Resource (Measured and Indicated) of 2.9 billion tonnes and an additional Inferred Resource of 2.7 billion tonnes for the KSM project which includes resources from 4 zones; Kerr (104B 191), Sulphurets (104B 182), Mitchell (104B 103) and Iron Cap zones (104B 173).

In 2019, Seabridge Gold Inc. completed an airborne magnetic and electromagnetic survey on the KSM project. Also at this time, 26 diamond drillholes, totalling 6121 metres, were completed on the Sulphurets (MINFILE 104B 182) deposit.

In December 2019, Seabridge Gold Inc. released an updated mineral resource for the KSM project (Kerr [MINFILE 104B 191], Sulphurets [MINFILE 104B 182], Mitchell [MINFILE 104B 103] and Iron Cap [MINFILE 104B 173]) totalling 3 038 000 000 tonnes measured and indicated grading 0.52 gram per tonne gold, 2.8 grams per tonne silver, 0.21 per cent copper and 0.0048 per cent molybdenum plus an additional 4 599 000 000 tonnes inferred grading 0.38 gram per tonne gold, 2.2 grams per tonne silver, 0.32 per cent copper and 0.0029 per cent molybdenum (Threlkeld, W.E., Ghaffari, H. [2020-04-30]: KSM (Kerr-Sulphurets-Mitchell) Prefeasibility Study and Preliminary Economic Assessment Update, NI 43-101 Technical Report). For a complete summary of each deposit refer to the above cited report.

Please refer to Iron Cap (104B 173), Mitchell (104B 180) and Kerr (104B 191) for more details of the KSM work history and bibliography.