The Siwash North occurrence is located on a small ridge south east of Siwash Creek and approximately 1.2 kilometres northwest of Siwash Lake.
The Elk property is underlain by Upper Triassic volcanics and sediments of the Nicola Group and by Middle Jurassic granites and granodiorites of the Osprey Lake batholith. The contact between these units trends north easterly across the property. Early Tertiary feldspar porphyry stocks and dikes of the Otter intrusions occur throughout the property.
The western property area is underlain by steeply west-dipping andesitic to basaltic flows, agglomerates, tuffs and minor siltstone and limestone units of the Nicola Group. The eastern half of the property is underlain by granitic rocks of the Osprey Lake batholith. Early Tertiary feldspar porphyry and quartz feldspar porphyry stocks and dikes of the Otter intrusions cut both of the above. Breccias containing rounded volcanic, dioritic and granitic fragments in a granitic matrix crosscut rocks of the Nicola Group, Osprey Lake batholith and Otter intrusions rocks. The elongate breccia bodies vary in width from 5 to 30 metres and trend to the northeast. These zones may be portions of major fault structures, but displacement, if any, is not readily apparent. Andesite dikes are the youngest units mapped, postdating all of the above. They are dark greyish green, fine- grained and vary in thickness from 30 centimetres to 5 metres. They are commonly muscovite-altered and brown weathering. Strong orange and blue clay alteration is also evident in these rocks. Mineralization appears to be spatially associated with these (Tertiary (?)) andesite dikes, which are locally cut by quartz veins.
The Nicola Group lithologies mapped on the Elk property consist of dark greyish green, massive basaltic andesite (some porphyritic containing pyroxene and/or amphibole phenocrysts and some containing 0.5-millimetre laminae of sand-sized black grains); pale grey-green siliceous laminated tuff; and brownish green to pale green agglomerates containing fragments from 5 to 50 centimetres in size. The Nicola rocks are occasionally silicified, carbonatized or epidote-altered. Iron oxide staining and finely disseminated pyrite are common.
Nicola rocks on the west side of the property dip approximately 60 degrees west, forming the east limb of a syncline. The syncline trends roughly north-south and its axis passes approximately 5 kilometres west of the property. Structural deformation in the area appears to be minimal.
The Osprey Lake granitic rocks are pinkish grey, medium to coarse-grained, equigranular quartz monzonite to granodiorite in composition. Pink, sugary textured aplite dikes cut the quartz monzonite. Quartz diorite related to the batholith is far less common and occurs as stocks. Dikes of quartz monzonite and hornblende-biotite-quartz monzonite also occur. Alteration includes weak to strong propylitic, argillic, phyllic and silicic assemblages.
The Otter intrusions comprise quartz feldspar porphyry, feldspar porphyry and quartz-biotite-feldspar dikes and stocks. The quartz feldspar porphyry is extensively clay altered.
Gold-silver mineralization on the Elk property is hosted primarily by pyritic quartz veins and stringers in altered pyritic granitic and, less frequently, volcanic rocks. Crosscutting relationships indicate that the veins are Tertiary in age; they may be related to Tertiary Otter intrusive events. To date, mineralization has been located in at least five areas on the Elk property: Siwash North, South showing (MINFILE 092HNE261), North showing (MINFILE 092HNE281), Siwash Lake (MINFILE 092HNE041, 295) and Bullion. The Siwash Lake zone is 800 metres south of the Siwash North deposit; the North showing and South showing areas are 2 and 3 kilometres south of Siwash North, respectively, and the Bullion zone is 500 metres north of the main Siwash North occurrence.
In the Siwash North area, gold occurs in veins measuring 5 to 70 centimetres wide, hosted by a zone of strongly sericitic altered granite and, in the west, volcanic rocks. In general, the mineralized zone trends east-northeast with southerly dips from 20 to -80 degrees (from east to west), and appears to be related to minor shearing. Quartz veining occurs in a number of parallel to subparallel zones. Each zone consists of one or more veins within an elevation range of 5 to 10 metres that can be correlated as a group to adjacent drill holes. In the eastern part of the area, up to six subparallel zones occur. Five of these zones are consistent enough to be labelled the A, B, C, D and E zones. Mineralization in the west has been identified in one or locally two zones (the B and C zones). The main mineralized zone (B) is consistent, with only minor exceptions, across the entire drill grid. The Siwash North structure has been tested to 335 metres down dip and along a strike length of 925 metres. The zone remains open to depth and along strike.
At the surface, supergene alteration has leached out most of the sulphides, though some pyrite and chalcopyrite remains. Mineralization occurs primarily as native gold, occasionally as spectacular aggregates of coarse flakes in frothy quartz (strong pyrite boxwork) or in fractures in the vein. Electrum was noted in one area as very coarse-grained flakes associated with strong manganese staining. Gold is rarely seen in boxworks in sericitic (phyllic) alteration.
In drill core, mineralization has not been affected by supergene processes. Metallic minerals in drill core include (in order of decreasing abundance) pyrite, chalcopyrite, sphalerite, galena, tetrahedrite, maldonite, pyrrhotite and native. Gold is strongly associated with pyrite and with a blue-grey mineral. Photomicrographs show the gold commonly in contact with this mineral, which may be a gold-bismuth alloy (maldonite?) or a copper-bismuth- antimony sulphosalt.
Gangue mineralogy consists primarily of quartz and altered wallrock fragments. Ankerite is commonly present, with lesser amounts of calcite. Minor barite is also present. Fluorite was noted in one vein as very small (less than 1 millimetre) zoned purple cubes scattered in the quartz.
Stronger alteration generally accompanies higher grade gold mineralization. Seven main types of alteration were recognized in the granitic rocks throughout the property: propylitic, argillic, sericitic, potassium feldspar stable phyllic, phyllic, advanced argillic and silicic. Locally, potassic alteration, skarnification and silicification are evident, but are relatively minor and do not appear to be related to mineralization.
Propylitic alteration is generally light green with biotite and hornblende altered to chlorite, and plagioclase is saussuritized. In volcanics, the colour is generally olive green, and the rock is soft. Argillic alteration is exemplified by bleached rock, with plagioclase white and clay-altered; potassium feldspar is slightly altered. Volcanics are bleached to light green or grey. Sericitic alteration is typically pale green with a micaceous sheen, with plagioclase altered to sericite; trace disseminated pyrite may be present. This type of alteration is often associated with quartz veins and appears to be the lowest grade alteration associated with gold mineralization. It is not recognized in volcanics. Potassium feldspar stable phyllic alteration is light pink, green or yellowish with potassium feldspar fresh, pink and blocky. Plagioclase and mafic minerals are altered to fine-grained quartz-sericite-pyrite. It often occurs with veins and is associated with gold mineralization; it is not recognized in volcanics. Phyllic alteration is generally grey, fine-grained quartz-sericite-pyrite alteration, usually associated with veins, often gradational to quartz and often auriferous. Advanced argillic alteration is exemplified by most or all of feldspar being destroyed, quartz is "free-floating". The alteration is often sheared and white in colour and is often associated with quartz veins. Volcanics are white or blue- coloured. Silicic alteration is quartz veining or replacement that is hard with moderate conchoidal fracture.
There is a strong symmetrical zoning of alteration around the quartz veins: vein - advanced argillic - phyllic - potassium feldspar stable phyllic - argillic - propylitic.
The Elk 1 to 27 claims were staked in November 1986 by Cordilleran Engineering Ltd. for Fairfield Minerals Ltd. to cover new showings of gold-silver mineralization veins. Work conducted on the property from 1986 to 1991 consisted of geological mapping, prospecting, line cutting, soil sampling, geophysics, excavator trenching, diamond drilling and road construction.
Measured geological reserves of the Siwash North deposit are 308,414 tonnes grading 22.17 grams per tonne gold and 24.68 grams per tonne silver using a cut-off grade of 10 grams per tonne gold. Reserves are based on results from 107 drill holes at 50 metre grid spacing along 804 metres of strike length to 304 metres down dip. All veining intercepts have been adjusted for true width and assays diluted to 2 metre mining widths (George Cross News Letter No. 223 (November), 1991).
The revised drill indicated reserve, based on more realistic open pit and underground mining widths of 0.39 to 0.79 metre with a cut-off grade of 20.5 grams per tonne gold, is 122,458 tonnes averaging 54.5 grams per tonne gold (George Cross News Letter No. 65, April 2, 1993).
From 1992 and 1995 (inclusive), 16,570 tonnes of ore were mined and milled and 1,518,777 grams (48,830 ounces) of gold and 1,903,000 grams (61,183 ounces) of silver were recovered. In 1996, Fairfield shipped all remaining stockpiles, estimated to contain 2700 tonnes and grading greater than 12 grams per tonne (Information Circular 1997-1, page 21). A total of 994 metres of ramp access and three development levels exist underground. Reverse circulation drilling, underground diamond drilling, reclamation, road construction, water sampling and aerial photography were also undertaken during this period.
Surface and underground diamond drill programs were carried out in the Siwash Mine area from 1994 to 1996 to define the resource. Exploration surface drilling was also carried out during the 1995 and 1996 field seasons to test trench targets between the Siwash mine site and the South showing area, 2.5 kilometres to the south. Limited prospecting and environmental monitoring was undertaken from 1997 to 1999.
In 1995, Fairfield Minerals, with the support from the Explore B.C. program, carried out an extensive program including geochemistry, 13,972 metres of surface and underground diamond drilling in 315 holes and reserve calculations. Surface drilling was done on fences 10 to 50 metres apart, underground drilling on fences 10 metres apart. Reserve calculations by the company and consultant Roscoe Postle gave the following results (Explore B.C. Program 95/96 - A38):
Company Roscoe Postle
Probable (undiluted) 16,991 tonnes at 28,200 tonnes at
50.2 g/t gold 26.6 g/t gold
Possible (undiluted) 50,260 tonnes at 66,400 tonnes at
42.0 g/t gold 31.4 g/t gold
The 1996 exploration program consisted of 6873 metres of drilling in 91 holes. The Siwash zone has been traced along a 914 metre strike length and down dip to 245 metres.
Reserves estimated by the company at January 1, 1996 were 121, 350 tonnes grading 25.4 grams per tonne gold and 35.3 grams per tonne silver. These include a diluted, open-pit probable resource of 11, 340 tonnes grading 58.97 grams per tonne gold, an underground probable resource below the open pit of 20, 225 tonnes grading 26.74 grams per tonne gold, and a further possible underground resource of 89, 790 tonnes grading 23.66 grams per tonne gold (Information Circular 1997-1, page 21).
Surface diamond drilling totalling 1413.96 metres in 12 holes was completed on the Siwash mining lease during 2000, testing the B, WD and Gold Creek West (GCW) zones. A trenching program was carried out in 2001 in the Siwash East area consisting of six trenches totalling 202 metres. Almaden Resources and Fairfield Minerals Ltd. merged into Almaden Minerals Ltd. in February, 2002.
In 2002, Almaden Minerals Ltd. undertook a 26 hole surface diamond drill program for a total of 4995.67 metres testing the B, WD, GCW and Bullion Creek zones. During the 2003 field season a 6570 metre, 30 hole, diamond drill program was carried out by Almaden in the Siwash North area testing the WD zone. The WD vein system is located approximately 100 metres north of the Siwash B zone vein and has been tested over a strike length of 610 metres and down dip for 380 metres.
By the end of May 2004, a total of eight mineralized veins had been discovered on the property. Four vein systems had been drilled in the Siwash area: the B system, with a strike length of 900 metres, has been tested down dip to 320 metres; the WD zone, with a strike length of 650 metres, has been tested to 370 metres down dip; the GCW zone, with a strike length of 300 metres, has been tested to 130 m down dip and the Bullion Creek (BC) zone, which has been tested with two holes to a depth of 75 metres. A new NI 43-101 compliant resource was calculated using drill data for the Siwash B and WD veins, just two of eight known mesothermal vein structures on the property. Global (bulk-tonnage and underground mineable) measured and indicated resources were reported to total 668,300 tonnes grading 9.66 grams per tonne gold (207,600 ounces) plus an additional 1,317,200 tonnes grading 4.91 grams per tonne gold (207,800 ounces) in the inferred category (News Release, Almaden Minerals Limited, May 28, 2004). Included in the global figures is a higher grade, underground-mineable resource totalling 164,000 tonnes grading 33.69 grams per tonne gold in the measured and indicated category, plus another 195 200 tonnes grading 16.38 grams per tonne gold in the inferred category.
In 2004, a diamond drill program consisting of 10,265 metres of NQ drilling in 44 holes was completed. As reported by Almaden in 2001, a possible extension to the B and WD vein systems was found roughly two 2 kilometres along strike to the east, on the other side of an area of overburden cover and no outcrop, as part of a trenching program. Grab samples of the vein material taken at surface assayed averaged analyses of 31.6 grams per tonne gold and 104.4 grams per tonne silver (News Release, Almaden Minerals Limited, March 4, 2005). This discovery added approximately 2 kilometres of prospective, unexplored strike length to the high-grade vein system.
In 2005, a diamond drill program consisting of 8395.0 metres of NQ drilling in 36 holes was completed. The following year another 58 diamond drill holes, totalling 8873.0 metres, were completed. In 2011, 25.5 line-kilometres of ground magnetic, self-potential and induced polarization surveys were completed on the area.
In October 2009, Almaden released an updated resource estimate, reporting combined measured and indicated resources of 1.57 million tonnes grading 5.9 grams per tonne gold and inferred resources of 1.86 million tonnes grading 6.0 grams per tonne gold, calculated using a cut-off of 1 gram per tonne (Press Release October 6, 2009 www.almadenminerals.com).
In 2011 and 2012, a 45 hole diamond drilling program, totalling 5527.6 metres, was completed on the area. This program confirmed the connectivity of the Far West zone to the main Siwash North zone. During this time, a drill hole (SND11-123) intercepted a gold- bearing quartz vein yielding 30.4 grams per tonne gold and 56 grams per tonne silver over 0.30 metre. Another drill hole (SND12-229), located 125 metres to the east of the previous hole, intercepted a 0.04 metre wide quartz vein yielding 1.23 grams per tonne gold and 354 grams per tonne silver over a 0.5 metre sample width (Assessment Report 34382).