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File Created: 16-Jul-1996 by George Owsiacki (GO)
Last Edit:  24-Mar-2022 by Nicole Barlow (NB)

Summary Help Help

NMI
Name BIG SLEEP (SULPHURETS), BIG SLEEP EAST, GRACE, TRACHSEL Mining Division Skeena
BCGS Map 104B050
Status Prospect NTS Map 104B08E
Latitude 056º 28' 22'' UTM 09 (NAD 83)
Longitude 130º 11' 33'' Northing 6259338
Easting 426539
Commodities Gold, Silver, Lead, Zinc, Copper Deposit Types H04 : Epithermal Au-Ag-Cu: high sulphidation
G07 : Subaqueous hot spring Ag-Au
Tectonic Belt Intermontane Terrane Stikine
Capsule Geology

The Sulphurets property is underlain by Upper Triassic Stuhini Group and Lower Jurassic Hazelton Group andesitic tuffs, flows and minor sediments that have locally been extensively and pervasively quartz-sericite-pyrite altered. To date, at least 40 zones of quartz +/- carbonate veining, stockwork and breccia have been discovered on the property. Mineralization consists of up to 15 per cent disseminated pyrite within altered volcanics and trace to several per cent combined tetrahedrite, sphalerite, galena, pyrargyrite and rare electrum and native gold within quartz veins.

The Big Sleep and Big Sleep East zones form a sinuous east to southeast trending zone of quartz +/- carbonate stockwork and veining exposed over a 400 metre strike length. Both zones are hosted within quartz-sericite-pyrite altered volcanic rocks adjacent the contact between Jurassic sediments and volcanics. The two zones are offset from each other by roughly 50 metres of left-lateral displacement along several minor structures.

The Big Sleep structure consists of a 260 metre long, 3 to 20 metre wide quartz-carbonate vein within a halo of quartz stockwork up to 50 metres wide. The zone has a sinuous, S-shaped surface exposure with thickening of the quartz vein and local 'pooling' of sulphides in the hinges of the 'S'. The Big Sleep East is an east to southeast trending, vertically dipping quartz vein stockwork up to 14 metres in width, exposed over 140 metres, hosted within a 10 metre wide halo of strong sericitic alteration. Vein material has undergone moderate to strong fracturing and brecciation. Mineralization consists of less than 1 per cent up to 10 per cent pyrite, tetrahedrite, galena, sphalerite and rare arsenopyrite. Graphite is common as fracture fill and crosscutting stringers within the quartz veins. Trench sampling from the Big Sleep East zone yielded up to 13.2 grams per tonne gold and 1011.2 grams per tonne silver across 0.7 metre (Assessment Report 24610).

The Trachsel zone forms part of a continuous 680 metre long northwest to west trending sinuous structure of quartz veining and stockwork that extends east and southeast along the Big Sleep zone, southeast along the Big Sleep East zone, and then southeast to south along the Trachsel zone, which pinches out just north of Brucejack Creek. The Trachsel zone is exposed for 280 metres along strike, is up to 12 metres wide, and consists of both vertical and shallowly dipping quartz veins hosted within silicified argillite and argillaceous conglomerate adjacent the contact between Jurassic sediments and volcanics. Sericite alteration is peripheral to the zone. Sulphide content within the veins is generally low, consisting of trace to minor amounts of pyrite, arsenopyrite, tennantite, tetrahedrite, sphalerite, galena and rare native gold. Trench sampling yielded up to 8.7 grams per tonne gold and 1797.3 grams per tonne silver across 0.75 metre (Assessment Report 24610).

The Grace zone is a zone of quartz +/- barite stockwork and veining hosted within quartz-sericite-pyrite altered andesitic volcanics, located west and northwest of the Big Sleep zone. The zone is from 3 to 15 metres wide, trends east to northeast, and dips between vertical and 60 degrees to the northeast. Mineralization consists of 1 to 10 per cent pyrite and trace tetrahedrite within altered rocks, and trace tetrahedrite, sphalerite and galena in the veins. The western end of the zone is characterized by a clam-shaped quartz vein/breccia 'blowout' of intense silicification, while the eastern portion of the zone appears to be folded around a local, east-west recumbent fold axis. Trench samples yielded up to 8.8 grams per tonne gold and 75.7 grams per tonne silver across a 1 metre width (Assessment Report 24610).

Bibliography
EMPR ASS RPT *24610, 36214, 39314
EMPR BULL 63
EMPR OF 1988-4
GSC MAP 9-1957; 1418A
GSC P 89-1E, pp. 145-154
Kirkham, R.V. (1963): The Geology and Mineral Deposits in the Vicinity of the Mitchell and Sulphurets Glaciers, M.Sc. Thesis, University of British Columbia
Simpson, T.M. (1983): The Geology and Hydrothermal Alteration of the Sulphurets Deposits, Northwest British Columbia, M.Sc. Thesis, University of Idaho
Armstrong, T.A. (2010-01-14): Technical Report and Resource Estimates on the West, Bridge, Galena Hill, Shore, SG & Gossan Hill Gold & Silver Zones of the Brucejack Property
Ghaffari, H. (2010-09-10): Technical Report and Preliminary Assessment of the Snowfield-Brucejack Project
Ghaffari, H. (2010-10-28): Technical Report and Preliminary Assessment of the Snowfield-Brucejack Project
Armstrong, T.A. (2011-03-04): Technical Report and Updated Resource Estimate on the Brucejack Property
Armstrong, T.A. (2011-04-04): Technical Report and Updated Resource Estimate on the Snowfield-Brucejack Property
Ghaffari, H. (2011-06-03): Technical Report and Preliminary Economic Assessment of the Brucejack Project
Armstrong, T.A. (2012-01-12): Technical Report and Resource Estimate on the Brucejack Property
Ghaffari, H. (2012-02-20): Technical Report and Updated Preliminary Economic Assessment of the Brucejack Project
Jones, I. (2019-04-04): Technical Report on the Brucejack Gold Mine
Pretium Resources Inc. (2020-03-09): Technical Report on the Brucejack Gold Mine, Northwest British Columbia

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