The Willa occurrence is located at 1220 metres elevation on the southwest side of Aylwin Creek, immediately west of its confluence with Wild Creek. Silverton, British Columbia lies 7.5 kilometres to the north.
The Willa occurrence is located on ground covered by the Rockland claim group. The claim group consisted of the Rockland (Lot 3884), Rustler and Willa (Lot 1529) claims.
The Willa deposit occurs in a 5 by 5 kilometre roof pendant of Lower Jurassic Rossland Group volcanics within the Middle Jurassic Nelson intrusions. Biotite and amphibole (likely actinolite) hornfels is developed within the Aylwin Creek roof pendant at or near the contact of the Nelson intrusions. In general, the rocks in and around the mineralized area have undergone lower greenschist facies metamorphism as evidenced by the development of actinolite-tremolite, biotite, epidote and albite-oligoclase.
Intruded into the Rossland Group volcanics in the area of the deposit is an Early Jurassic epizonal quartz latite porphyry ring and radial dike complex, and a central feldspar porphyry stock which are interpreted as being comagmatic and in part coeval with the Rossland volcanics. Penetrating the porphyry, and likely related to it, is a subvertical heterolithic breccia pipe which hosts gold-copper-silver mineralization in several structurally controlled zones.
The Rossland Group within the pendant strike northeast, are largely pyroclastic in origin and steeply dipping. The volcanics range from coarse breccia to tuff and volcanic siltstone. Augite porphyry is a significant component in the mineralized area and may be in the form of sills and/or flows. The Rossland volcanics are predominantly of basaltic composition but does include some low silica andesite.
The fragmental rocks range from volcanic agglomerates and conglomerates, with porphyritic clasts up to 50 centimetres in diameter, to finely bedded crystal and lithic tuffs. The volcanic breccias predominate and are generally monolithologic.
Most of the augite porphyry occurs near or within the quartz latite porphyry ring dike complex. Augite porphyry occurs in two types of bodies: irregular intrusive bodies that crosscut the inferred bedding, and stratiform flows and tuff breccias.
Volcanic siltstones are usually thin bedded and intercalated with augite porphyry and less frequently with other types of volcaniclastics.
Quartz latite porphyry forms a ring and radial dike complex centred about a feldspar porphyry heterolithic breccia pipe complex. It generally ranges in composition from quartz monzonite to monzogranite to granodiorite, but much of this variation is probably due to potassic alteration (Heather, 1985). The ring dike portion of the complex is elliptical in plan view, 1 by 5 kilometres, with the long axis trending 050 degrees. Numerous dikes radiate inward and outward from this ring dike complex.
Feldspar porphyry forms a hypabyssal stock centred within the quartz latite porphyry ring dike complex. The stock has an elliptical surface plan with the long axis trending north-south.
Centrally located within the quartz latite porphyry ring dike complex, a heterolithic breccia forms a crudely cylindrical pipe-like body whose surface expression is an ellipse, 350 by 200 metres, with the long axis trending roughly north-south. Horizontal sections through the breccia pipe reveal that with increasing depth the width remains relatively constant but the length, at least to 1050 metres (ASL) increases to 450 metres. Rock types found as fragments within this breccia body include: pyroclastics, augite porphyry, volcanic siltstones, biotitic schist, quartz latite porphyry and feldspar porphyry. The breccia pipe appears to plunge to the north-northeast at a steep angle and commonly grades outward into a marginal crackle breccia which ranges in width from a few metres to several tens of metres.
Within the mineralized area only dikes and/or sills related to the Nelson intrusions were intersected in drilling. Mafic dikes crosscut all other rocks and appear to be post-mineralization.
Distinctive fracture patterns can be related to igneous intrusive events and post-intrusive deformational events. Structures observed include faults, fractures, intrusive and tectonic breccias, and late stage shear zones.
The most prominent structure within the Aylwin Creek mineralized area is the Willa shear zone. The Willa shear is a near-vertical zone which strikes 045 degrees and is an intensely fractured or shattered zone. The zone is a few tens of metres wide and has been traced for approximately 350 metres. Offset on mafic dikes indicates minimal left-lateral (5 metres) movement. This major structure is clearly post-mineralization and crosscuts all rock types within the mineralized area.
Three superimposed fracture sets were found which could be related to major geologic features within the mineralized area. The first set strikes 045 degrees parallel to the Willa shear zone with fractures of this set being most abundant within and near this zone. These fractures crosscut all earlier fractures. The second fracture set tangentially rings the breccia pipe. This set is best developed on the eastern margin of the breccia pipe. The third fracture set is north-south oriented and can be correlated with the trace of the Main mineralized zone and is well developed in the southern portion of the pipe, but weak in the central portion. The pattern is obscured in the north by the fractures associated with the Willa shear zone. Somewhat weaker north-south fractures are evident on the eastern and western margins of the breccia pipe; the East and West mineralized zones may be related to these (Heather, 1985).
A series of superimposed alteration and mineralization types are spatially related to the Willa deposit. Early potassic alteration centred on the feldspar porphyry stock grades outward to a propylitic alteration of the country rock. Superimposed on this is a calcsilicate alteration related to the late stages of heterolithic breccia pipe development. Retrograde alteration is superimposed on the calcsilicate mineral assemblages. Postdating all other alterations is a group of late-stage veinlets.
Potassic alteration consists predominantly of biotite and associated but less abundant potassium feldspar, occurring predominantly within and around the central feldspar porphyry stock. Limited surface data indicates that the potassium feldspar alteration is more abundant (relative to the biotite alteration) in the centre of the potassic alteration zone. Locally the potassium feldspar alteration appears to be overprinting the biotite alteration, but in general the two appear to be approximately coeval. The biotite alteration is of two types. The first and most prominent type consists of fine, disseminated secondary biotite within the feldspar porphyry stock and the immediately surrounding country rock. Rocks with this alteration have a pink hue. The second type consists of felted masses of biotite pseudomorphing original hornblende phenocrysts in quartz latite porphyry dikes which lie peripheral to the area of pervasive pink biotite alteration.
Calcsilicate alteration consists of various combinations, in order of generally decreasing abundance, of pyroxene, amphibole, epidote, garnet, plagioclase, potassium feldspar, quartz, anhydrite, sphene and calcite. These occur as matrix replacements within the heterolithic breccia pipe and as vein material within peripheral crackle zones. The calcsilicate alteration can be subdivided into four types which represent increasing degrees of calcium metamorphism: amphibole, pyroxene, epidote and garnet(-anhydrite) types.
There are two distinct types of mineralization within the Aylwin Creek mineralized area: molybdenite mainly associated with quartz veinlets in the quartz latite porphyry, and gold-copper-silver associated with the calcsilicate alteration. Only the gold-bearing mineralization is of economic significance.
Extensive molybdenite +/- quartz mineralization is locally developed in the quartz latite porphyry and ring dikes and the volcanics surrounding them. Plagioclase phenocrysts are commonly albitized within a narrow halo about the quartz veinlets. An extensive pyrite halo partly overlaps, and is peripheral to the mineralization. Locally associated with these molybdenite-bearing quartz veins are thin quartz-sericite-pyrite alteration envelopes.
The gold-copper-silver mineralization at Willa occurs in three major zones (Main, West and East) hosted within the heterolithic breccia pipe and its peripheral crackle breccia. The central Main zone contains the bulk of the mineralization and is comprised of two near-vertical, en echelon tabular bodies that strike north-south across the core of the breccia pipe. The West and East zones occur in marginal crackle breccia and may form one continuous arcuate zone around the southern portion of the breccia pipe (Heather, 1985).
The Main zone is near vertical, strikes north and extends at least to the 1000 metre level (ASL) or approximately 270 metres below the surface. The trace of this zone on surface is 200 metres in length. The width is variable, ranging from 10 to over 60 metres locally, with the average being 30 metres. It attains a length of 400 metres. The southern end of the Main zone is predominantly a crackled breccia made up of volcanic and feldspar porphyry fragments. The central portion occurs in heterolithic breccia, and the northern end terminates against the quartz latite porphyry ring dike (to the north of the breccia pipe). The maximum width of the mineralized zone is in the central portion of the breccia pipe, where it is intersected by the Willa shear zone.
The West zone is situated approximately 60 metres west of the Main zone at a depth of 240 metres below the surface. The West zone may wrap around the southern periphery of the heterolithic breccia pipe. The West zone does not crop out at surface and appears to be hosted within a crackle breccia on the west side of the heterolithic breccia pipe.
The East zone is in an area of intense crackle breccia in volcanics, with abundant sulphides and associated calcsilicate alteration. The zone can be traced for 100 metres in Aylwin Creek on the eastern edge of the heterolithic breccia pipe. The East zone appears to be localized in crackle breccia similar to the West zone, possibly with the two wrapping around the southern portion of the heterolithic breccia pipe and joining up (Heather, 1985).
Mineralization consists of pyrite, pyrrhotite, chalcopyrite, native gold, magnetite, minor sphalerite, and traces of native silver, in virtually any combination. Locally these minerals may be accompanied by hematite and traces of lead-bismuth bearing antimony sulphosalts. The mineralization occurs as massive sulphide, breccia matrix replacements, stockworks in peripheral crackle breccia zones and as disseminations and veins. The mineralization is associated with a suite of calcium-rich minerals including salite-ferrosalite, actinolite, andradite, epidote, anhydrite, scapolite and calcic plagioclase. These calcsilicate alteration minerals occur as massive to vuggy replacements of rock-flour breccia matrix in the central part of the breccia pipe and as veins and veinlets in the marginal crackle breccia. There is a strong spatial relationship between the mineralized zones (high gold grades) and the development of high calcium mineral assemblages, with andradite being particularly localized in the upper portions of the mineralized zones and anhydrite in the lower portions. The andradite-magnetite assemblage overprints the pyroxene-pyrite-pyrrhotite assemblage, with the gold mineralization being deposited during this transition (Heather, 1985).
U/Pb analyses of 5 zircon fractions obtained from the Aylwin Creek porphyry (stock related to mineralization) resulted in a range of ages from 176-185 Ma; a precise age cannot be assigned. The best-fit lower intercept, ca. 183 Ma, is considered to be a reasonable estimate of the minimum age (GSA Special Paper 299, pages 159-171, 1995).
The Willa deposit has features in common with the alkalic-type porphyry copper-gold deposits, the Rossland gold-copper camp, and copper and iron skarns (Heather, 1985).
Development on the property began as early as 1899 when a 30- tonne shipment of copper-gold ore was reported from the Rockland claim. To 1904, underground work totalled approximately 91 metres of drifts in three adits, one on the north side of the creek and two on the south. Work in 1937 included 32 metres of drifting and 3 metres of raising.
The Willa claim was first Crown granted in 1898 to Willow Gold Mining Co. The Rockland claim produced 300 tonnes of ore in 1899 and the claim was subsequently Crown granted to W. Spinks in 1900. At this time, the Rockland claim group was owned by Spinks, Graves and Watson. About 91 metres of drifts were completed by 1904 with three adits, one on the north side of Aylwin Creek and two on the south side. Claim ownership was transferred to W.J. Nicholls in the 1930s and optioned to Slocan Lake Gold Mining Company Inc. in 1936. An additional 32 metres of drifting and 3.6 metres of raise were completed. Northlode Exploration Ltd. held 17 Crown grants and claims including the Rockland group in the 1960s. Under option to Cominco Limited between 1964 and 1965, 297 metres of diamond drilling in four holes were carried out on the Willa and Rockland claims. Rockland Mining Ltd. was incorporated in 1967 and purchased the Rockland Group and Little Daisy (082FNW070) Reverted Crown grants. Additional ground covering 36 recorded claims surrounding the Rockland and Little Daisy claim groups were purchased. A diamond drilling program was carried out near the Rockland and Little Daisy occurrences. The Aylwin joint venture between Riocanex Inc. (50 per cent) and BP Canada Inc. (50 per cent) carried out additional drilling on the claims from 1980 to 1981. From 1980 to 1984, 14,295 metres of diamond drilling from 47 surface holes were completed. By 1984, BP Canada Inc. had acquired a 72 per cent interest in the property. Northair Mines Ltd. obtained an option in 1985 to earn a 50 per cent interest in the property over three years. The final partnership called for a Northair (50 per cent), BP Canada Inc. (36 per cent) and Riocanex Inc. (14 per cent) interest in the property. Exploration performed by Northair Mines Ltd. between 1986 and 1987 included 290 metres of drifting and crosscutting, 2317 metres of underground diamond drilling in 51 holes, and sampling of drift rounds, drift faces and walls and drill core. In 1987, an upper level was opened into the Main zone and a decline driven under the West zone.
Measured geological reserves at the West zone are 414,297 tonnes grading 6.03 grams per tonne gold and 0.92 per cent copper (George Cross News Letter October 24, 1988). Combined (probable and possible) reserves at the Main and East zones are 219,518 tonnes Cross News Letter October 24, 1988).
Production records for the Willa occurrence indicate 300 tonnes mined with no recorded recovery in 1899. In 1988, 7883 grams silver, 2873 grams gold, 4418 kilograms copper, 63 kilograms lead and 4154 kilograms zinc were recovered from 495 tonnes of custom ore.
Orphan Boy Resources Inc. entered into an option to purchase agreement, in June 2002, to acquire the property.
In 2003, Orphan Boy Resources Inc. announced the acquisition of Imperial Metals Corporation wholly owned Bethlehem Resources Corporation. Bethlehem’s principal asset is the 1,000 metric ton per day Goldstream mill and related infrastructure. It has been the intention of Orphan Boy to mine the Willa and truck the ore to the Goldstream facility for milling.
The 2004 underground drilling program consisted of 5282.8 metres in 39 holes and was designed to cover six areas adjoining known areas of Au-Cu-Ag mineralization that had either not been drilled or were under drilled. The drilling in the peripheral areas of the Willa deposit was not successful in locating significant new zones of potentially economic mineralization. Drilling along the west edge of the West Zone did better define the boundaries of that zone.
Willa contains a measured resource of 487,989 tonnes grading 6.77 grams gold, 0.97 per cent copper and 11.59 grams silver, plus an indicated resource of 292,457 tonnes at 5.31 grams gold, 0.65 per cent copper and 11.94 grams silver; total resources, including inferred, are pegged at 996,623 tonnes grading 6.3 grams gold, 0.79 per cent copper and 10.77 gram per tonne silver, at a 3.5-gram gold cutoff (The Northern Miner, April 21, 2005).