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File Created: 24-Jul-85 by BC Geological Survey (BCGS)
Last Edit:  27-Mar-18 by Sarah Meredith-Jones(SMJ)

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NMI 104O16 Ag4
Name SILVERTIP, MIDWAY, SILVER CREEK, DISCOVERY, DISCOVERY NORTH, SILVER CREEK EXTENSION Mining Division Liard
BCGS Map 104O099
Status Producer NTS Map 104O16W
Latitude 59º 55' 38" N UTM 09 (NAD 83)
Longitude 130º 20' 32" W Northing 6644067
Easting 424973
Commodities Zinc, Silver, Lead, Gold, Tin, Copper, Antimony Deposit Types J01 : Polymetallic manto Ag-Pb-Zn
E14 : Sedimentary exhalative Zn-Pb-Ag
Tectonic Belt Omineca Terrane Cassiar
Capsule Geology

The Silvertip deposit is located near the Tootsee River in the Cassiar Mountains just south of the Yukon-British Columbia border.

The deposits occur in a carbonate and clastic sedimentary sequence of the Cassiar terrane, which has been intruded into the west by the mid-Cretaceous Cassiar batholith. The sediments include the Kechika, Sandpile, McDame and Earn groups. The deposits are situated on the west limb of a broad, open, northwest trending synclinorium, the core of which is occupied by volcanics, sediments and ultramafic rocks of the Devonian-Triassic Sylvester Allochthon. Massive sulphide zones in the Midway deposits occur in limestones of the upper part (Unit MLS) of the Middle-Upper Devonian McDame Group. This unit is unconformably overlain by clastic sediments of the Upper Devonian-Lower Mississippian Earn Group, which consists of two upward-coarsening sequences of turbiditic flows.

Several exhalative horizons, consisting of fine grained massive to laminated silica and/or barite with pyrite, sphalerite and minor galena occur in the Earn Group sediments. Two of these, the Upper and Discovery zones, occur near the base of the second cycle, and contain lead-zinc-silver mineralization. Sulphides within the exhalite zones are restricted in extent although exhalites are widespread and may be stratigraphically correlatable.

The McDame/Earn groups contact is a pronounced erosional surface, with carbonates below the contact strongly affected by Late Devonian karstification. The unconformity cuts across 165 metres of McDame limestone stratigraphy near the deposit. Uplift and erosion and karst development in Late Devonian time was accompanied by high-angle block faulting, which made the carbonates a better aquifer for meteoric waters. Breccias at Midway include carbonate mosaic breccias, and solution-collapse breccias which include Earn Group clasts. Vein mineralization occurs throughout the McDame and Earn groups. Veins vary from hairline fractures to 20 centimetre widths, and consist of quartz, calcite, pyrite, galena and sphalerite.

Mafic dikes of unknown age occur in the Midway area, and are commonly sericitized in the vicinity of the deposits. Potassium-argon dating of sericitized Earn Group sediments and quartz feldspar porphyry dikes about two kilometres southeast of the deposit, give ages of about 66 million years. The source of mineralizing fluids has not been identified, although the high silver content of the deposits and tin mineralization indicate a probable magmatic origin. Earn Group mudstones above the unconformity locally confined mineralizing fluids to the underlying limestones, with sulphide deposition occurring as open-space filling and replacement of carbonates.

The Silver Creek zone contains two high-grade core zones, Silver Creek North and Silver Creek South. Massive sulphide mineralization consists of pyrite (and associated marcasite and pyrrhotite), sphalerite and galena, with lesser freibergite, pyrargyrite, argentite, boulangerite, stannite, arsenopyrite, cassiterite, chalcopyrite and quartz-carbonate gangue. Lead sulphantimonides have also been identified. Sulphide textures indicate several phases of brecciation, replacement and open-space drusy growth. The southern part of the zone is characterized by freibergite and pyrargyrite and very fine grained colloform pyrite, while the northern part is marked by abundant lead sulphantimonides and by the absence of freibergite, pyrargyrite, pyrrhotite and colliform pyrite. Indicated ore reserves for the Silver Creek zone, in 1985, were 2,847,920 tonnes grading 446.4 grams per tonne silver, 8.45 per cent lead and 10.21 per cent zinc (Assessment Report 13259).

The Discovery deposit occurs about 300 metres east of the Silver Creek North core zone. Massive and brecciated sulphides occur in several zones in the McDame limestones. Mineralization consists of pyritic, pyrrhotitic and base metal massive sulphide (greater than 50 per cent sphalerite and galena) zones. These zones vary in thickness from 0.2 to 2.3 metres. Sulphides also occur as matrix to both sulphide and carbonate clast breccias. "Trash" breccias commonly occur toward the base of mineralized intersections. Metal distribution relations are not well known for the Discovery deposit. The Discovery zone, in 1985, was thought to contain 3,813,307 tonnes of indicated ore grading 371.7 grams per tonne silver, 13.34 per cent zinc and 5.4 per cent lead (Assessment Report 13259).

It is now known that the Silver Creek and Discovery zones are actually the same with a lower grade mineralized zone in between.

Silvercorp Metals Inc. acquired the property in February 2010 and released an updated resource estimate as follows:
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Classification Amount Grade
(tonnes) Ag(g/t) Pb(%) Zn(%) Au(g/t)

Indicated 1,976,664 398 7.65 10.35 0.58
Inferred 357,713 413 7.50 11.05 0.26

Silvertip NI43-101 Technical Report dated February 19, 2010 (http://silvercorpmetals.com)
Calculated using a greater than 400 grams per tonne Ag equivalent cut-off.
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In 1955, galena-rich float was discovered by prospectors on Silvertip Hill. In late 1956 and 1957, Conwest Exploration Company explored gossanous zones in the McDame Group limestone by drilling and surface and underground workings. Zones of galena and silver-rich values were found but most of the sulphides were thoroughly oxidized. In 1958, drilling was continued by a joint venture between Noranda Mines Limited, Canex Aerial Exploration Limited and Bralorne Mines Limited. A number of other companies optioned the property between 1960 and 1966, conducting AFMAG and induced polarization (IP) surveys over Silvertip Hill to identify drill targets. Other work included photo and geological mapping, rock and soil sampling, and trenching and stripping. Some good anomalies were found, but follow-up drilling found only deeply oxidized mineralization with generally uneconomic silver grades. Silverknife Mines Limited owned the Silvertip claims from 1966 until the claims lapsed in the early 1970s. During this time, four rotary holes were drilled (1966) to test IP anomalies, and two diamond-drill holes were targeted on electromagnetic (EM) survey targets (1967). Two diamond-drill holes tested geophysical anomalies in 1968. By this time, the idea that silver-lead mineralization was related to replacement of limestone at its contact with overlying ‘shale’ was the dominant exploration model for the Silvertip Hill area. However, results were still not encouraging due to various drilling problems, weak mineralization, or deep oxidation. Very little work was done in the 1970s.

In 1980, the main phase of exploration began when Cordilleran Engineering, on behalf of subsequent property owner Regional Resources Limited, was conducting regional reconnaissance in search of shale-hosted, lead-zinc Sedex deposits. The property was then known as Midway. They found base metal anomalies in soils and stream sediments about 1500 metres northeast of Silvertip Hill, which led to the discovery of baritic and siliceous gossans of exhalite origin within the Earn Group. Regional mapping, soil and EM surveys followed in 1981, with six diamond-drill holes around the exhalite showings. Four of these unexpectedly intersected massive sulphide below the base of the Earn Group, at the top of the McDame Group limestone, and by the end of 1982 the exploration focus had again shifted back to limestone-hosted replacement mineralization. An aggressive surface drill program was conducted between 1982 and 1984, along with geophysics and petrographic and metallurgical research. Two main, blind areas of mineralization were outlined, Silver Creek and Discovery, and a manto-type deposit model was formulated. Encouraged by the apparent size of the mineralized area and the good grade and thickness of sulphides, the company began underground exploration development in the Silver Creek area (1984), followed by 12,383 metres of underground drilling over 170 holes, in fans spaced 20 metres apart. The results showed that the mineralization was more erratic and discontinuous than had been modeled from the widely spaced surface drill pattern, leading to a reduced estimate of the size of the resource.

A new underground development initiative was carried out between 1989 and 1991 by operator Strathcona Mineral Services, with the opening of a decline to the east towards the Discovery area, and completion of 9620 metres of underground drilling. In 1996, Imperial Metals Corporation of Vancouver acquired Regional Resources and renamed the company Silvertip Mining Corporation (SMC). A large exploration program in 1997 comprising diamond drilling, seismic surveying, and surface geological mapping resulted in the discovery of a new zone, the Silver Creek Extension, now part of the Silver Creek zone. The high grade, near-surface Silver Creek Extension zone mineralization was intersected immediately north of the Silver Creek zone. A second new zone, Discovery North, is 150 metres north of the Discovery zone (T. Schroeter, personal communication, 1997). This added significantly to the total geological resource, which was subsequently recalculated at 2.57 million tonnes grading 325 grams per tonne silver, 6.4 per cent lead, 8.8 per cent zinc and 0.63 gram per tonne gold.

In 1998, SMC entered the Environmental Assessment review process with the provincial government for project certification. That year, various environmental baseline studies were done and monitoring procedures instigated, along with a reconnaissance CSAMT (Controlled Source Audio Frequency Magneto Telluric) geophysical survey. This survey revealed a large, vertically oriented low-resistivity anomaly between the Silver Creek South area and the Camp Creek fault, suspected of indicating a sulphide chimney. A more detailed, follow-up CSAMT survey was done in 1999, and the best three geophysical targets were drilled. One hole (99-65) intersected thick, feeder-style mineralization. This intersection prompted the re-opening of a portion of the existing underground workings by de-watering and refurbishment of decline and tunnels in the fall of 1999. This was followed by 3210 metres of underground diamond drilling in January-February 2000, centred on drillhole 99-65. This drilling identified the Zone 65 area of the deposit in sufficient detail to support a resource calculation for the 65 Zone but this was not done. The 65 Zone had failed to live up to the company’s hopes for the addition of significant additional high grade mineralization in the form of a feeder pipe or chimney.

A 14 line, 8.85 line-kilometre natural source Audio Frequency Telluric (AMT) geophysical survey was conducted in the summer of 2001. The grid was installed to the north of the previously known mineralization, in an area where the McDame limestone is not under the cover of the typically graphitic Earn Group sedimentary rocks. The AMT survey was successful in defining previously known geological features that confirmed the techniques effectiveness. At least one strong anomaly evident in the survey data was recommended for drilling, that target is as yet untested.

In 2002, Silver Standard acquired the Silvertip Project from Imperial Metals and put further work on the property on hold.

Silvercorp subsequently purchased the property from Silver Standard in February, 2010 and completed an NI 43-101 compliant report on the resources and work to date on the property. Silvercorp Metals Inc. conducted exploration and development work which included a VTEM geophysical survey, core drilling, a brief exploration and mapping program, claim staking and studies related to environmental impact including wildlife, fisheries, plants, air quality, noise and archaeology. Work began in July with a 4113 line-kilometre VTEM airborne geophysical survey over the entire property. This program was not successful in identifying the Silvertip deposit proper or in repeating some previously identified high priority AMT geophysical anomalies. The survey did identify a number of VTEM anomalies on the property. Drilling began in August and totalled 10,913.36 metres of NQ coring in 36 drillholes. Of the 36 drillholes attempted, 12 were abandoned before completion for various reasons including broken ground, drill rods getting stuck in the hole and inexperienced operators. Eighteen out of 24 completed drillholes intersected mineralization, and 17 of these drillholes intersected significant mineralization. Field exploration investigated the DM zone at Donegal Mountain, 8 kilometres south of the Silvertip deposit where previous work had identified high grade silver-lead-zinc mineralization at the Earn/McDame contact. Geological mapping at 1:1000 scale and collection of 14 mineralized rock samples for geochemical analysis were undertaken in September and October and traced mineralization for over 300 metres along this contact. The area is targeted for drill testing to define the potential for economic mineralization in this satellite zone.

Exploration work in 2011 was comprised of diamond drilling of the upper zone exhalite horizon near the portal, the kilometre long AMT geophysical anomaly to the east of the portal and on the DM zone, a contact-hosted zone of anomalous silver, zinc and lead mineralization 8 kilometres south of the main deposit. Road building was undertaken to create 10.05 kilometres of drill access to the DM zone and 3.5 kilometres of trail and drill pad refurbishment. A geotechnical drilling program was completed late in the year to collect near-surface soil samples and to install ground water monitoring wells in anticipation of mine construction in the near future. Exploration core drilling began in late June. The drill program completed 3994.5 metres of NQ coring in 21 drillholes. Of the 21 drillholes attempted, six were abandoned in bad ground and three of these were subsequently completed to target depth on a second attempt.

Silvercorp Metals Inc. released a Preliminary Economic Assessment for the Silvertip Project dated November 15, 2012 which included updated resources calculated at 325 grams per tonne Ag equivalent. In the Lower Zone indicated resources were reported as 2,455,000 tonnes grading 315 grams per tonne Ag, 5.88 per cent Pb, 6.28 per Zn and 0.413 gram per tonne Au, and inferred resources as 1,649,000 tonnes grading 281 grams per tonne Ag, 4.55 per cent Pb, 5.64 per cent Zn and 0.093 gram per tonne Au. In the Upper Zone inferred resources were reported as 3,638,000 tonnes grading 39 grams per tonne Ag, 0.65 per cent Pb, 2.36 per cent Zn and 0.025 gram per tonne Au.

JDS Silver Inc. (a private company) purchased the Silvertip project from Silvercorp in late 2013 and in June 2015 announced approval to start mine construction.

In October 2017 Coeur Mining Inc. purchased the Silvertip property from JDS Silver Inc.. Updated resources were reported in their news release on September 11, 2017:
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Category tonnes Ag (g/t) Zn (%) Pb (%)
Indicated 2,349,000 352 9.41 6.73
Inferred 460,000 343 9.81 6.18
Calculated at a cut-off grade of 200 grams per tonne AgEq
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In March 2018 Coeur Mining Inc. announced commencement of production. They estimate mill throughput of 250 tonnes per day in April steadily increasing to 750 tonnes per day by year-end (Coeur Mining Inc. News Release March 8, 2018).

Bibliography
EMPR ASS RPT *9912, *11020, *11799, *13259, *14104, *15560, 16899, 20735, *25495, 25791, 26073, 26240, *31919, *32976
EMPR EXPL 1986-A41; 1996-B14; 1997-17; 1998-13,30; 1999-1-11,19-31; 2000-1-8; 2001-1-9
EMPR FIELDWORK 1981, pp. 162-166; *1982, pp. 149-170; 1986, pp. 181-192; 1987, pp. 249-254, 353-362, 525-527
EMPR INF CIRC 1998-1, pp. 22-23; 1999-1, pp. 12,13; 2000-1, p. 17
EMPR MAP 65 (1989)
EMPR MP MAP 1992-12
EMPR OF 1987-5; 1992-1; 1996-11; 1998-8-M, pp. 1-74; 1998-10; 2000-22
EMPR P 1991-4, pp. 71-88
EMPR BULL 83
EMPR PF (Regional Resources Ltd. Annual Reports 82/83, 83/84, Canamax Res. Inc., 1986; see Mount Polley, (093A 008) - Imperial Metals Corporation information folder; See Silvertip (104O 003) for extensive listing; Memorandum regarding visit to property, 1985; Location map; Midway deposit compiled by D.G. MacIntyre; The Midway Project: Regional Resources, Research Report, Mar.28, 1984; News Release, Regional Resources Ltd., Dec.5, 1983; Generalized stratigraphy of Midway property, Nov. 1982)
EMR MIN BULL MR 223 B.C. 347
EMR MP CORPFILE (Regional Resources Ltd.; Amex of Canada Ltd.; Procan Expl. (B.C.) Ltd.; Canamax Res. Inc., 1986)
GSC MAP 18-1968
GSC OF 561; 2779
GSC P 68-55
CIM Reporter Oct.30, 1981
GCNL #192,#196,#230, 1981; #127,#146,#159,#187,#188,#203,#226, 1982; #50,#60,#74,#87,#108,#111,#144,#151,#182,#189,#225,#236, 1983; #10,#15,#30,#60,#75,#97,#112,#120,#149,#156,#194,#201,#226,#230, 1984; #31,#90,#116,#166,#179,#224, 1985; #112, 1986; #144(Jul.27), 1989; #162(Aug.22),#196(Oct.10),#205(Oct.24),#209 (Oct.30),#231(Dec.2), 1997; #10(Jan.15), 1998; #79(Apr.26), 1999; #45(Mar.6),#84(May2), 2000
IPDM May/June 1982
MIN REV Sept/Oct 1984; Fall 1998, pp. 27-28; Fall 2000
N MINER Apr.16, Oct.15, Dec.3, 1981; Mar.4, June 10, Oct.7, Nov.11, Dec.2, 23, 1982; May 5, June 2, Aug.11,18, Sept.22, Oct.20, Nov.24, Dec.15, 1983; Jan.19, Feb.16, Mar.22, May 17,24,31, June 1,14,21, Aug.9, Oct.4,25, Nov.15, 1984; Feb.21, Mar.7, May 23, June 6,20, July 25, Sept.9, Oct.21, 1985; June 23,30, July 28, 1986; Aug.7, Sept.25, 1989; Sept.24, 1990; Nov.10, 1997; February 23, May 4, Dec.14, 1998; June 7, Oct.18, 1999; Jan.31, Mar.13, 2000; Dec.9, 2002
N MINER MAG Feb. 1986
PR REL Imperial Metals Corporation, Nov.26, 1998; Silver Standard Resources Inc., Dec.2, 2002; Coeur Mining Inc. Sept.11,2017, Oct.17,2017, Mar.8,2018
W MINER Nov. 1981; Dec. 1983
*Abbott, J.G. (1983): Silver-bearing Veins and Replacement Deposits of the Rancheria District, Yukon Exploration and Geology, 1983, DIAND, pp. 34-44
Abercrombie, S.M. (1984): Midway, Report for UBC course Geology 558
Archambault, M. (1985): Geology and Mineralogy of the Silver Creek Deposit, Midway Property, North-Central B.C., (M.Sc. Thesis, UBC)
*Bradford, J. (1988): Geology and Genesis of the Midway Deposit, North Central British Columbia, M.Sc. Thesis, University of British Columbia
Dawson, K.M. Godwin, C.I., and Gabites, J. (1985): Lead isotope analysis from silver-rich deposits in the Cassiar, Midway and Ketza River areas of the Northern Cordillera; GAC Cordilleran Section Symposium, Program with abstracts, Silver '85, Vancouver, B.C.
Imperial Metals Corporation Annual Report 1996; 1997, p. 10
Preliminary Economic Assessment of the Silvertip Project, November 15, 2015 for Silvercorp Metals Inc.
*Sorenson, J. (1985): The long road to Midway, CMJ Apr 1985, pp. 20-27
*Stollery, J.W. and Sellmar, W.H. (1982): Midway, an analysis of a massive sulphide discovery, CMJ April 1982, pp. 66-71

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