The Windfall property is 100% owned by Osisko Mining Inc. and consists of 286 individual claims covering an aggregate area of 12,523 hectares. The Windfall project, located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec, Canada is 700 kilometres north-northwest of Montréal, 200 kilometres northeast of Val-d’Or and 115 kilometres east of Lebel-sur-Quévillon. The Windfall project falls within the traditional territory of the Cree First Nation of Waswanipi.
Windfall is a world-class gold deposit located in the Eeyou-Itschee James Bay territory of Quebec, Canada.
LATEST NEWS — WINDFALL
The Urban-Barry Greenstone Belt
The Windfall property is located in the central part of the Urban-Barry greenstone belt which is part of the Abitibi Subprovince (figure 2). The Urban-Barry belt is an east-west trending belt that is 135 kilometres long by 4 to 20 kilometres wide. The belt is dominated by mixed mafic to felsic volcanic rocks with lesser fine-grained clastic sedimentary sequences. This greenstone belt was deformed during the 2.71 to 2.66 Ga Kenoran orogen (Card, 1990). The rocks generally record greenschist grade metamorphism, but locally reach amphibolite facies within corridors of intense deformation and proximal to large pluton contacts (Joly, 1990).
The belt is divided into five rock formations (Rhéaume and Bandyayera, 2006): 1) the Fecteau (2791 Ma), 2) the Lacroix (no age), 3) the Chanceux (2727 Ma), 4) the Macho (2717 Ma) and 5) the Urban (2714 to 2707 Ma). The Windfall deposit is hosted in the volcanic rocks of the Macho Formation which contains two distinct lithostratigraphic sequences: the Rouleau Member and the younger Windfall member (2716.9 ± 2 Ma). The Windfall deposit is hosted in the Windfall member which is comprised of: 1) calc-alkaline dacite, rhyodacite and trachyandesite, 2) tholeiitic felsic tuffs and lavas, 3) tholeiitic to transitional andesite porphyries and tuffs, and 4) minor iron formation (Bandyayera 2002, Rhéaume and Bandyayera, 2006). This volcano-sedimentary sequence is cut by a series of granodiorite quartz feldspar porphyry dikes (QFP). U-Pb zircon ages from pre- and post-mineralization QFP intrusions were dated at 2698 ±3 Ma and 2697.6 ±0.4 Ma, respectively (D. Davis unpublished report to Osisko Mining Inc. 2016).
Osisko mining is currently the largest stakeholder in the Urban-Barry greenstone belt with over 40 % of the land staked.
Rock Types of the Windfall deposit
The rock types in the Windfall deposit are divided into two groups: 1) synvolcanic rocks that form part of the Macho Formation (ca. 2717 Ma), and 2) syntectonic rocks that intrude the volcanic sequence and are part of a regional tectonic-magmatic event at ca. 2698 Ma.
Synvolcanic Host Rocks
The intermediate to mafic volcanic rocks are of tholeiitic affinity and range in composition from basalt to andesite. They consist of massive, pillowed, fragmental and breccia flows that are locally vesicular or porphyritic with phenocrysts of plagioclase. The rock is commonly fine-grained, medium green to dark green in colour, and is weakly to strongly foliated.
The felsic volcanic rocks are of tholeiitic affinity and range in composition from dacite to rhyolite. Texturally, they consist of massive and breccia flows that are often porphyritic containing small (1 to 3 millimetres) phenocrysts of quartz that vary in abundance from 2 to 10%. The rock is commonly fine-grained, yellowish beige in colour that can locally be green when chloritized and is weakly to moderately foliated. Felsic volcanics are stratigraphically located above the mafic-intermediate volcanics.
Mafic intrusions are of tholeiitic affinity and range in composition from basalt to komatiite but are simply visually described as gabbros. These intrusions locally cross-cut the mafic to felsic volcanic rocks, but mainly occur as sill shaped bodies that are laterally extensive and range from 1 to 300 m in thickness. The rocks are texturally homogenous and massive, have a medium to dark green color, are fine- to medium-grained and are locally weakly foliated.
At depth, thin horizons (0.3-1m) of argillite and mudstone are locally interbedded within the felsic volcanic sequence. The sedimentary units are dark grey-green, fine-grained, bedded, and contain pyrite-pyrrhotite laminations.
Syn-deformation Rocks – Windfall Intrusive Complex
In the Windfall deposit, five texturally distinct QFP dikes are observed to cross-cut the volcanic strata at high angles. The QFP dikes are all of granodiorite composition and of calc-alkaline affinity. The dikes are divided into three main groups based on several criteria: texture, colour, size and abundance of quartz phenocrysts, orientation and timing with respect to deformation and mineralization. These groups are: 1) syn-deformation fragmental and small quartz eye QFPs, 2) syn-deformation large quartz eye QFPs; and 3) post-mineral hematite altered QFPs.
Syn-deformation fragmental and small quartz eyes QFPs
The small quartz eye QFP dike is characterized by 2 to 10% small quartz eyes generally less than 2 millimetres in diameter (figure 3 – I2P). This unit has some textural variations that range from massive and porphyritic to fragmental with up to 30% sub-angular to sub-rounded fragments. The fragments are generally <1 centimetre in diameter. Fragments are comprised of volcanic fragments, both intermediate and felsic compositions, that are locally sericite and pyrite altered. This dike is the earliest observed intrusive phase and was dated at 2698 ± 3 Ma using TIMS U-Pb of zircon (D. Davis, 2016, unpublished report to Osisko Mining).
In the Lynx zone, another fragmental intrusive phase is present is referred to as the I1 Frag. The I1 Frag differentiates from the I2P as it contains abundant fragments of: 1) earlier QFP intrusive; 2) felsic and mafic volcanics; 3) tourmaline-breccia; and 4) quartz-pyrite fragments. The contact of this magmatic breccia with the small quartz eye porphyry stock is gradational to locally sharp.
Syn-deformation large quartz eyes QFPs
The large quartz eyes QFP dikes form stocks and small dike swarms that trend northeast to east and crosscut the earlier fragmental porphyry intrusions. They are composed of an aphanitic matrix that contains variable proportions of large sub-rounded quartz eyes (> 2 mm) and locally altered feldspar and amphiboles. The dikes are classified according to the abundance of quartz eyes which varies from trace <1% (I1P Try), 1 to 10% (I1P YL), and >10% (I1P YB) large quartz eyes as shown in figure 3.
Post-mineral hematite altered QFPs
There are two types of post-mineral hematite altered QFPs and they are both geochemically indistinguishable from each other (figure 3 – Red Dog and I13). The Red Dog intrusion has a brick-red color, an aphanitic matrix that contains 3 to 10% quartz phenocrysts (up to 1 cm) and 5 to 10% poorly defined relict feldspar phenocrysts. Locally the Red Dog intrusion is weakly magnetic, which is caused by millimetre-sized magnetite crystals. The Red Dog intrusion was dated at 2697 ± 0.4 Ma using TIMS U-Pb of zircon (D. Davis, 2016, unpublished report to Osisko Mining). The I13 intrusion is pinkish to slightly orange, fine grained with a saccharoidal-texture, is homogeneous, non-magnetic, and contains less than 1% quartz eyes smaller than 2 millimetres. The I13 intrusion was dated at 2695 ± 3.8 Ma using HR-ICP-MS U-Pb of zircon (C. Azevedo, 2018, unpublished data).
The post-mineral dikes are a late intrusive phase that cross-cut all the volcanics, syn-deformation QFP units, and gold mineralization and associated hydrothermal alteration as observed in surface and underground exposures.
Gold mineralization occurs in two styles: 1) vein-type mineralization, and 2) replacement-type mineralization. Vein-type mineralization consists of grey to translucent coloured quartz veins that contain subordinate amounts of ankerite, tourmaline, pyrite and commonly visible gold (figure 4). The veins have sharp contact margins that are straight or folded. Texturally these veins are massive, but locally can form laminated textures characteristic of fault-fill veins (Robert and Poulsen, 2001). The veins vary in thickness from 0.1 to 1 m and are generally associated with the highest gold grades ranging on average from 20 to >100 g/t. In the veins, sulphide content ranges from 1 to 80% and is dominated by pyrite with minor concentrations (<1% total sulphide) of chalcopyrite, sphalerite, arsenopyrite, galena, pyrrhotite, tennantite and other Bi Te minerals, as identified by internal petrographic and microanalytical analyses. This mineralization style is commonly observed to occur in felsic volcanic dominated domains of the deposit (i.e., Caribou and Lynx). Replacement-type mineralization occurs at the margins of vein-type mineralization or in high strain zones that lack the development of quartz veins. This mineralization style consists of pyrite replacement zones and stockworks associated with a strong pervasive silica-sericite-ankerite ± tourmaline alteration of the host rock (figure 4). The gangue and precious-metals are identical to those mentioned above in the vein-type mineralization. The gold is associated with disseminated pyrite, which varies from 1 to 80% over mineralized intervals. This mineralization style is commonly observed to occur in the mafic volcanic dominated domains of the deposit (i.e., Main area).
The most significant gold mineralization defined to date is currently known for a vertical extent of approximately 1,800 metres in four areas; the Lynx area (Lynx Main, Lynx HW, Lynx SW, Triple Lynx, and Lynx 4), the Main area (Zone 27, Caribou, Mallard, Windfall North and F-Zones), the Underdog area, and the Triple 8 area (figure 5). In general, the bulk of the gold mineralization in the Windfall deposit forms within a series of subvertical to moderately dipping zones that have sigmoidal geometries with true widths of single mineralized envelopes averaging between 1-10 m and are generally oriented east-northeast with plunges of about 35° towards the east-northeast.
The size and nature (i.e., vein- and replacement-type mineralization) of the mineralized lenses vary slightly from area to area and this is a reflection of the different host rock types across the deposit. The main differences between the host rock types are the different rheological and chemical contrasts which create the necessary traps to channel and destabilize gold-rich fluids.
Mineral Resource Estimate
February 2021 Mineral Resource Estimate Update
- Measured and Indicated Resources (M&I): 1.67 M oz Au at 9.6 g/t Au;
- Inferred Resource: 4.24 M oz at 8.0 g/t Au;
- The resources are defined from surface to a depth of 1,600 metres as it now includes the Triple 8 (T8) zone. The resources excluding T8 are defined from surface to a depth of 1,200 metres.
The 2020 drilling increased the measured and indicated mineral resource estimate by 54% (adding 651,000 ounces) and increased the inferred mineral resource estimate by 306,000 ounces. In addition, two bulk samples (Zone 27 and Lynx) have been successfully completed in 2018 and 2019 and returned positive results.
- Values are rounded to nearest thousand which may cause apparent discrepancies.
- Lynx area includes: Lynx Main, Lynx HW, Lynx SW and Lynx 4 and Triple Lynx.
- Main area includes: Zone 27, Caribou, Mallard, Windfall Nord and F-Zones.
Windfall Gold Deposit Mineral Resource Estimate Notes:
- The independent qualified person for the 2021 MRE, as defined by NI 43-101 guidelines, is Pierre-Luc Richard, P.Geo.(OGQ#1119), of BBA Inc. The effective date of the estimate is November 30, 2020.
- The Windfall mineral resource estimate is compliant with the November 29, 2019 CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines.
- These mineral resources are not mineral reserves as they have not demonstrated economic viability. The quantity and grade of reported inferred mineral resources in this news release are uncertain in nature and there has been insufficient exploration to define these resources as indicated or measured; however, it is reasonably expected that the majority of inferred mineral resources could be upgraded to indicated mineral resources with continued exploration.
- Resources are presented undiluted and in situ and are considered to have reasonable prospects for economic extraction. Isolated and discontinuous blocks above the stated cut-off grade are excluded from the mineral resource estimate. Must-take material, i.e. isolated blocks below cut-off grade located within a potentially mineable volume, was included in the mineral resource estimate.
- As of November 30, 2020, the database comprises a total of 3,612 drill holes for 1,343,593 metres of drilling in the area extent of the mineral resource estimate, of which 2,959 drill holes (1,161,872 metres) were completed and assayed by Osisko. The drill hole grid spacing is approximately 12.5 metres x 12.5 metres for definition drilling, 25 metres x 25 metres for infill drilling and larger for extension drilling.
- All core assays reported by Osisko were obtained by analytical methods described below under “Quality Control and Reporting Protocols”.
- Geological interpretation of the deposit is based on lithologies, mineralization style, alteration and structural features. Most mineralization envelopes are subvertical, striking NE-SW and plunging approximately 40 degrees towards the north-east. The 3D wireframing was generated in Leapfrog Geo, a modelling software, from hand selections of mineralization intervals. The mineral resource estimate includes a total of 374 tabular, mostly subvertical domains defined by individual wireframes with a minimum true thickness of 2.0 metres.
- Assays were composited within the mineralization domains into 2.0 metres length composites. A value of 0.00125 g/t Au and 0.0025 g/t Ag (¼ of the detection limit) was applied to unassayed core intervals.
- High-grade composites were capped. Cappings were determined in each area from statistical studies on groups of zones sharing similar mineralization characteristics. Cappings vary from 10 g/t Au to 200 g/t Au and from 5 g/t Ag to 150 g/t Ag. A multiple capping strategy defined by capping values decreasing as interpolation search distances increase was used in the grade estimations.
- Block models were produced using Datamine™ Studio RM Software. The models are defined by parent cell sizes of 5 metres NE, 2 metres NW and 5 metres height, and sub-locked to minimum sub-cell sizes of 1.25 metres NE, 0.5 metres NW and 1.25 metres height.
- Ordinary Kriging (“OK”) based interpolations were produced for gold estimations in each area of the Windfall deposit, while silver grade estimations were produced using OK or Inverse Distance Squared (“ID2”) interpolations. Gold estimation parameters are based on composite variography analyses. The gold estimation parameters were used for the silver estimation.
- Density values of 2.8 were applied to the mineralized zones.
- The Windfall mineral resource estimate is categorized as measured, indicated and inferred mineral resource as follows:
- The measured mineral resource category is manually defined and encloses areas where:
- drill spacing is less than 12.5 metres;
- blocks are informed by a minimum of four drill holes;
- geological evidence is sufficient to confirm geological and grade continuity;
- zones have been accessed by underground workings.
- The indicated mineral resource category is manually defined and encloses areas where:
- drill spacing is generally less than 25 metres;
- blocks are informed by a minimum of two drill holes;
- geological evidence is sufficient to assume geological and grade continuity.
- The inferred mineral resource category is manually defined and encloses areas where:
- drill spacing is less than 100 metres;
- blocks are informed by a minimum of two drill holes;
- geological evidence is sufficient to imply, but not verify geological and grade continuity.
- The measured mineral resource category is manually defined and encloses areas where:
- The mineral resource is reported at 3.5 g/t Au cut-off. The cut-off grade is based on the following economic parameters: gold price at USD1,485/oz, exchange rate at 1.30 USD/CAD, 94% mill recovery; payability of 99.95%; selling cost at USD5/oz, 2% NSR royalties, mining cost at CAD100/t milled, G&A cost at CAD30/t milled, processing cost at CAD40/t, transportation cost at CAD2/t considering mill at site, and environment cost at CAD10/t. A cut-off grade of 3.5 g/t Au was selected over the calculated cut-off grade of 3.2 g/t Au to better reflect a realistic mining cut-off.
- Estimates use metric units (metres, tonnes and g/t). Metal contents are presented in troy ounces (metric tonne x grade / 31.10348).
- The independent qualified person is not aware of any known environmental, permitting, legal, title-related, taxation, socio-political or marketing issues, or any other relevant issue, that could materially affect the mineral resource estimate.
- Values in tonnes and ounces are rounded to nearest thousand which may cause apparent discrepancies.
The Lynx zone consists of five gold mineralized zones located in the east-northeast portion of the deposit (figure 6). The gold mineralization is hosted in a felsic volcanic dominant domain (i.e., rhyolite) with minor felsic QFP and mafic intrusions (i.e., I2P, I1P, gabbro sills). Most of the Lynx mineralization zones form an extensive anastomosed network of quartz-rich and pyrite-rich veins hosted within strongly silicified felsic volcanic rocks or gabbros. This system is located on the southern limb of an open fold plunging at 40º towards the east-northeast along the Bank fault-shear zone. It also coincides with the global plunge of most of mineralized zones at Windfall. The Lynx Main, Lynx HW, Lynx SW and Lynx 4 zones are closest to the Bank fault and are locally influenced by the latter. In contrast, the Triple Lynx zone is located roughly 200 to 300 m lateral distance from this structure and occurs beneath a thick gabbroic sill.
The Main area consists of five gold mineralized zones located in the central portion of the deposit (Zone 27, Caribou, Mallard, Windfall North, and F-Zones) that terminate at the upper contact of the thick post-mineral Red Dog QFP intrusion (figure 7). The gold mineralization is constrained along east-northeast oriented contacts of narrow subvertical granodioritic dikes within tilted volcanic rocks. Most mineralized envelopes in the Main zone are associated with pyritic stringers occurring near contacts between volcanic rocks and younger intrusive rocks. Generally, the gold mineralization is hosted in a mafic dominant domain (i.e., basalt and andesite). In contrast, the Caribou zone is partly hosted in felsic volcanics.
The Underdog area is located in the southwestern portion of the deposit and is separated from the Main area by the post-mineral Red Dog QFP intrusion and occurs beneath the latter. The top of this deeper mineral zone starts at around 600 m depth and continues to depths of roughly 1,600 m where it is still open at depth and down-plunge. The gold mineralization is hosted in a syn-deformation QFP dominant domain (i.e., I2P, I1P QFP dikes) with minor mafic and felsic volcanic rocks. The mineralization in the Underdog zone is composed of disseminated to semi-massive pyrite intervals associated with strong silica and sericite alteration, generally following main intrusive contacts and/or deformation zones.
The Triple 8 zone is located 660 m east-northeast from the closest mineralized intercept in the Underdog Zone. The drill hole Deep Discovery 1, the longest diamond drill hole in Canada with a final depth of 3,467 m, also intercepted the Triple 8 corridor and several other zones of anomalous gold mineralization up to 116 m in strike length. The Triple 8 zone consists of mostly mafic to intermediate volcanic rocks intercalated with felsic flows and gabbro sills cross-cut by a series of syn-deformation QFP intrusions and post-mineral Red Dog intrusion. The volcanic package is metamorphosed to upper greenschist facies consisting of a chlorite-calcite-epidote-magnetite metamorphic assemblage. This alteration assemblage is then cross-cut by shear zones altered by a gold-bearing fluid, forming an early biotite-chlorite-carbonate-pyrite assemblage that is later overprinted by a sericite-carbonate-silica-pyrite assemblage. The latter alteration assemblage is associated with most of the gold mineralization. The primary control on gold mineralization in the Triple 8 area appears to be controlled by series of stacked northeast-oriented shear zones. Within these shear zones, the mineralization is mainly composed of pyrite-rich replacement zones that are cross-cut by laminated quartz-carbonate-tourmaline ± pyrite veins and carbonate-quartz stockworks and breccias.
The F-Zones are located in the northern portion of the deposit. Gold mineralization in the F-17, F-11 and F-51 zones differs from that of the Main and Lynx areas. The F-Zones trend to the northeast, subparallel to the Main area, but dip steeply to the north. F-17 and F-51 are aligned along the same trend but separated by approximately 800 m. F-11 lies in a similar structural context but is located 500 m to the northwest. Mineralization continuity between the two zones cannot be established from the current drilling data. The zones cross-cut a package of mafic to intermediate volcanics that are cut by narrow QFP intrusions. The zones are interpreted to be associated to the Northern fault, and the mineralization is typical of shear-hosted replacement-type mineralization at the contacts of QFP dykes, which consists of narrow corridors of moderate to strong sericite-carbonate-pyrite and weak silica alteration that is cross-cut by a stockwork of thin pyrite-quartz veinlets.
The classification of the Windfall deposit has significantly evolved since the acquisition of the project by Osisko Mining. The Main area which consists of the Zone 27 and Caribou were initially interpreted as an intrusion-related gold deposit type because gold mineralization and associated alteration showed a strong spatial and temporal relationship with felsic porphyry intrusions.
However, additional work (i.e., two bulk samples and underground mapping, adding +1,000,000 meters of drilling, and discovering the Lynx zone) performed since 2016 has significantly improved the understanding of the deposit. Gold mineralization in the Windfall deposit is now clearly associated with a deformation event that overprints the earliest phases of felsic magmatism (i.e., small and large quartz eye QFPs) and that exhibits a strong structural control on the emplacement of gold mineralization. The Windfall deposit is characterized as an atypical orogenic gold deposit due to the presence of unique mineralogical assemblages and the temporal and spatial association of gold with intrusive phases. Gold mineralization is hosted in: 1) deformation zones that are concentrated in areas of contrasting competencies defined by lithological variations; 2) along geometrical boundaries between flat-lying lithological boundaries and steep gold-bearing structures; and 3) along strong chemical boundaries between ultramafic and felsic rock types. The structural style is variable (i.e., brittle or ductile) and is largely dependent on host rock composition (rhyolite-andesite-gabbro-QFP).
Mineralization consists of a network of quartz-carbonate-pyrite-tourmaline veins and an associated silica-sericite-pyrite alteration assemblage. The mineralization and alteration have strike lengths of >2 km that show, as of yet, no recognized vertical zoning. Gold mineralization is only locally spatially associated with calc-alkaline QFP dikes but shows no genetic association with them. The QFP intrusions were emplaced mainly as a product of tectonism and deformation and act only as competent host rocks that concentrate deformation and gold-bearing hydrothermal fluids.
This new model significantly improved the targeting potential of new mineralized zones at the deposit scale and contributed to expanding known mineralized zones.
First Bulk Sample : Zone 27
- The first bulk sample (5,500-tonne) was prepared with Zone 27 mineralized material.
- Average grade of 8.53 g/t Au for the bulk sample; 26% higher than predicted in the 12.5 m infill drilling block model.
- The sample contained 1,508 ounces Au and 1,450 ounces of Ag.
- Average Au recovery of 93.7% achieved using contract mill.
- A total of 34.5% of the gold was recovered in the gravity concentrate.
The Zone 27 bulk sample is characterized by a sub-vertical zone of sulphides in a strong silica alteration envelope averaging 1.5 metres thick, hosted in a strong sericite altered porphyritic dike containing disseminated pyrite. Mineralization consists of up to 30% pyrite stringers, up to 20% disseminated pyrite, with trace chalcopyrite and sphalerite. Visible gold was observed locally, predominantly in silica fracture filling. Geological mapping during the bulk sample has shown that the mineralized zone is very distinctive and identifiable on the mining face.
The bulk sample test was performed at the Northern Sun Redstone concentrator at an average throughput of 30 tonnes per hour. Processing produced gravity and flotation concentrates. Ore transportation trucks were sampled for moisture and weighed on a calibrated weight scale. The sample material was crushed and milled to a particle size favorable to the flotation recovery process. Gravity and flotation concentrates produced were weighed and sent to a local smelter for sale. Daily composite samples of streams for the reconciliation process were prepared and analyzed by an external independent lab. Concentrate production tonnage and assays were used to reconcile the bulk sample mass balance process in the concentrator. The reconciliation was performed by an external independent consultant using Bilmat (a reconciliation software) on a dry tonnes basis. A total of 2,080 tonnes were processed in December 2018. Subsequently, 3,420 tonnes were processed in May 2019.
The reconciled head grade is 8.53 g/t Au and 8.20 g/t Ag. The sample contained 1,508 oz Au and 1,450 oz Ag, and a total of 1,413 oz Au and 1,355 oz Ag were recovered. Reconciled recoveries are 93.7% for gold and 93.4% for silver. The Preliminary Economic Assessment metallurgical test work considered a communition, gravity and carbon in leach process flowsheet, giving an average recovery of 92.5% for Zone 27. Test mill availability dictated the use of a mill with a comminution, gravity and flotation flowsheet. The reconciled results from the processing of the bulk sample material are presented in Table 1 below:
Mill feed tonnages used in the sample processing reconciliation were provided by Northern Sun. Daily composite samples collected during the processing of the bulk sample were assayed by external independent laboratories. Bulk sample results were reconciled by an external independent consultant using Bilmat.
The area mined was located in mineralization wireframe 115 from the Windfall resource block model. The area was prepared for mining with infill drilling at 12.5 metre spacing. The internal update of the resource block model using infill drilling in the bulk sample area (using May 2018 MRE parameters) predicted 5,512 tonnes at 6.76 g/t Au containing 1,198 ounces of gold inside the excavated area (see Table 2 below).
Both the gravity concentrate and flotation concentrate produced from the sample are considered high-grade. The gravity concentrate averaged 1,389 g/t Au (44.7 oz/T Au), while the flotation concentrate averaged 69.8 g/t Au (2.2 oz/T Au), or respectively CDN$75,479/t and CDN$3,790/t (using US$1300/oz and 1.3 US/CDN exchange rate). Further work will be conducted on the process flowsheet prior to feasibility in light of these high-value numbers.
Mining and Grade Control
The bulk sample area displayed excellent ground conditions. The sample was mined through conventional development methods following the orebody in an ENE-WSW direction over approximatively 56 metres. Rounds were 5.5 metres high, between 2.4 – 3.0 metres deep with an average width of 4 metres. Selective blasting was performed (with an ore blast and a marginal blast) depending on ore thickness and the presence of the Red Dog dike. Benches were performed on the floor over 20 metres and in the access level in order to capture ore along the plunge of the mineralized zone. Channel sampling in the drift face and muck sampling was conducted after each round. Channel and muck assays dictated what material was shipped to the mill for processing.
Second Bulk Sample: Lynx Zone
- The second bulk sample (5,716-tonne) was prepared with Lynx Main Zone mineralized material
- Average grade of 17.8 g/t Au for the bulk sample: 89% higher than predicted in the 12.5 m infill drilling block model
- The sample contained 3,271 ounces Au and 2,176 ounces of Ag.
- Higher than anticipated average Au recovery of 97.2% achieved using contract mill.
- A total of 66.7% of the gold was recovered in the gravity concentrate
The Lynx zone 311 bulk sample is characterized by an East-North-East sub vertical silica altered corridor with an average width of approximately 2.5 meters. Banded grey quartz veins contain 3 to 15% disseminated pyrite and local visible gold, cross-cutting foliated rhyolite and granodiorite with strong sericite and local fuchsite alteration. The continuous vein system was mapped along sills over three levels.
A total of 5,716 tonnes were processed in November 2019. The bulk sample test was performed at the Northern Sun Redstone concentrator. Processing produced gravity and flotation concentrates. Ore transportation trucks were sampled for moisture and weighed on a calibrated weight scale. The sample material was crushed and milled to a particle size favorable to the flotation recovery process. Gravity and flotation concentrates produced will be sent to a local smelter for sale. Day and night shift daily composite samples of streams for the reconciliation process were prepared and analyzed by an external independent lab. Concentrate production tonnage and assays were used to reconcile the bulk sample mass balance process in the concentrator. The reconciliation was performed by an external independent consultant using Bilmat (a reconciliation software) on a dry tonnes basis.
The reconciled head grade obtained from the processed sample is 17.8 g/t Au and 11.8 g/t Ag. The sample contained 3,271 oz Au and 2,176 oz Ag, with a total of 3,181 oz Au and 2,052 oz Ag recovered. Reconciled recoveries are 97.2% for gold and 94.3% for silver. The Preliminary Economic Assessment metallurgical test work considered a communition, gravity and carbon in leach process flowsheet, giving an average recovery of 93.8% for Lynx zone. Test mill availability dictated the use of a mill with a communition, gravity and flotation flowsheet. The reconciled results from the processing of the bulk sample material are presented in Table 1 below:
Mill feed tonnages used in the sample processing reconciliation were provided by Northern Sun. Day and night shift daily composite samples collected during the processing of the bulk sample were assayed by external independent laboratories. Bulk sample results were reconciled by Soutex Inc., an external independent consultant using Bilmat.
The area mined was located in mineralization wireframe 311 from the Windfall Lynx updated resources block model. The area was prepared for mining with infill drilling at 12.5 metre spacing. The same parameters used in the November 2018 Mineral Resource Estimation (see Osisko news release dated November 28, 2018) were used for an internal update of the resource block model in the bulk sample area. The infill drilling block model predicted 5,717 tonnes at 9.40 g/t Au containing 1,736 ounces of gold inside the excavated area (see Table 2 below).
Both the gravity concentrate and flotation concentrate produced from the sample are considered high-grade. The gravity concentrate averaged 7,020 g/t Au (225.7 oz/T Au), while the flotation concentrate averaged 110.6 g/t Au (3.6 oz/T Au), or respectively CDN$381,464/t and CDN$6,010/t (using US$1300/oz and 1.3 US/CDN exchange rate). Further work will be conducted on the process flowsheet prior to feasibility in light of these high-value numbers.
Mining and Grade Control
The Lynx bulk sample was mined in wireframe 311 with the long hole mining method proposed in the PEA. Two development drifts were mined conventionally at 20 metre vertical intervals between 210 and 230 meters below surface. A third development drift was mined 20 metres above the stope at 190 meters below surface to confirm grade and continuity of the Lynx 311 wireframe. While mining the development drifts, split blasts of the face were completed to test the width and grade of the mineralization. A V30 borehole was used in the slot raise and two and one-half inch production holes were drilled down and blasted. The blasted ore was retrieved with remote scoop tram equipment and trucked to the mill with muck samples taken.
NI 43-101 Technical Report: Preliminary Economic Assessment Update for the Windfall Lake Project
NI 43-101 Report: An Updated Mineral Resource Estimate for the Windfall Lake Project, Located in the Abitibi Greenstone Belt, Urban Township, Eeyou Istchee James Bay, Québec, Canada
NI 43-101 Technical Report: Preliminary Economic Assessment of the Windfall Lake Project, Lebel-sur-Quévillon, Québec, Canada
NI 43-101 Technical Report and Mineral Resource Estimate for the Windfall Lake Project, Windfall Lake and Urban-Barry Properties
Maps and Sections
Press Release Maps
26/03/2019Chargeability Signature Triple8 Area Southwest Plan View
26/03/2019Chargeability Signature Triple8 Area Southeast Longsection View
26/03/2019Chargeability Signature Triple8 Area South Inclined View
26/03/2019Chargeability Signature Triple8 Area Northeast Long-section View
Windfall - December 2020
Windfall - October 2019
Windfall - June 2019
Windfall - March 2019
Windfall - January 2019
Windfall - October 2018
Windfall - August 2018
Windfall - May 2018
Windfall - January 2018
Windfall - December 2017
Windfall - November 2017
Windfall - October 2017
Windfall - September 2017
Windfall - August 2017
Windfall - July 2017
Windfall - May 2017
Windfall - March 2017
The Windfall area is accessible year-round and is serviced by a complete network of well-maintained logging roads.
The Windfall exploration camp can accommodate 300 people. This area includes:
- Temporary trailer-type structures for administrative offices, dormitories and infirmary as well as the kitchen and the dining room
- Septic fields and an enviro-septic unit
- Four separate core shacks with core racks
- Two drill core storage areas
- A core cutting building
- Three drinking water wells
- Three megadomes
- Three temporary maintenance and storage areas for diamond drilling companies
- Three generators (2MW each) providing electricity to the surface and underground infrastructure
- Fuel tanks
- A helicopter landing area
- Containers and sheds for storage of equipment
- Propane storage tank
- A composting unit
The exploration ramp portal sector includes the following facilities:
- Access roads
- A portal and a ramp
- Underground exploration tunnels
- An overburden pile
- A lined stockpile (mineralized material and waste rock) with lined perimeter ditches
- A sedimentation basin and a polishing basin
- Water treatment units and geotubes
- A garage with concrete slab
- Sanitary facilities (septic tank and leaching field)
- Construction trailers serving as offices and drys
- Magazines for storage of explosives and detonators
- A megadome with concrete foundations
- A fuel storage tank
- A ventilation raise with heaters and propane tank
Windfall – 01 – Closing Plan – Mise à jour du plan de restauration 2017 (French)
July 1, 2017Download View
Windfall – 01a – Closing Plan – Questions et réponses – Mise à jour du plan de restauration 2017 (French)
April 1, 2018Download View
Windfall – 02 – Closing Plan – Complément d’information 1 – Premier agrandissement de la halde (French)
December 1, 2018Download View
Windfall – 02a – Closing Plan – Questions et réponses 1 – Complément d’information 1 (French)
July 1, 2019Download View
Windfall – 02b – Closing Plan – Questions et réponses 2 – Complément d’information 1 (French)
October 1, 2019Download View
Windfall – 03 – Closing Plan – Complément d’information 2 – Deuxième agrandissement de la halde (French)
June 1, 2020Download View