02 Pr Projects 2.001

Windfall

The Windfall property is 100% owned by Osisko Mining Inc. and consists of 285 individual claims covering an aggregate area of 12,467 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_map@2x

Figure 1: Map showing the location of the Windfall project.

 

Key Facts

Windfall is a world-class gold deposit located in the Eeyou-Itschee James Bay territory of Quebec, Canada.

1.21M oz Au 4.13Mt at 9.1 g/t Au (indicated) Mineral Resource Estimate
3.94M oz Au 14.53 Mt at 8.4 g/t Au (inferred) Mineral Resource Estimate
125 km² PROJECT AREA
26% Zone 27 positively reconciled bulk sample
89% Lynx Zone positively reconciled bulk sample
1,200,000 m Current Drilling Program
3,467 m Longest drillhole in Canada

Project Description

Geology

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 that are constrained to 2791 to 2707 Ma (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) that are constrained to 2697.6 ± 0.4 Ma at the WLGD site (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.

greenstone_belt@2x

Figure 2: Simplified regional geology map showing the location of the Urban Barry greenstone belt.

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

Intermediate to mafic volcanic rocks are basalt to andesite in composition with a tholeiitic affinity. 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.

Felsic volcanic rocks are rhyolitic in composition with a tholeiitic affinity and 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 range from basalt to komatiite in composition with a tholeiitic affinity but are simply visually described as gabbros. These intrusions cut the mafic to felsic volcanic rocks, occur as sill shaped bodies, 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.

Syntectonic Rocks – Windfall Intrusive Complex

The Windfall intrusive complex (WIC) was formed during seven distinct phases of felsic magmatism. The complex, observed crosscutting the volcanic strata at high angles, forms dikes and stocks that are subvertical to the present surface. The dikes are all of granodiorite composition and of calc-alkaline affinity. The dikes are divided into three main groups based on several criteria including: 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 4 – 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, one large stock of the small quartz eye QFP dike is rimmed by a magmatic breccia. This magmatic breccia (figure 4 – I1Frag) has the matrix of the small quartz eye QFP dike but also contains large fragments of: 1) rhyolite, 2) gabbro, 3) small quartz eye QFP dike, 4) of silica-pyrite altered fragments, and 5) tourmalinite. 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 4.

Post-mineral hematite altered 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 There are two types of post-mineral hematite altered QFPs and they are both geochemically indistinguishable from the above mentioned syn-deformation QFPs and are part of the same magmatic event (figure 4 – 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 post-mineral dikes are a late intrusive phase that crosscut all the volcanics, syn-deformation QFP units, and gold mineralization and associated hydrothermal alteration as observed in surface and underground exposures.

qfp_windfall@2x

Figure 3: Representative photographs of syn-deformation QFP intrusive rocks from the Windfall intrusive complex in order from earliest to the latest . Dating of the I2P and of the Red Dog dike were done using TIMS U-Pb of zircon by D. Davis at the University of Toronto. The dating of the I13 dike was done by C. Azevedo using HR-ICP-MS U-Pb of zircon at the Geotop Laboratory at the University of Québec.

Gold Mineralization

Gold Mineralization

Gold mineralization occurs in two styles: 1) vein-type mineralization, and 2) replacement-type mineralization. The vein-type mineralization consists of grey colored quartz veins with subordinate carbonate, pyrite, tourmaline, and locally visible gold (figure 5 A-C). Pyrite is the dominant sulphide mineral but locally traces of sphalerite, chalcopyrite, galena, arsenopyrite, tennantite, and tetrahedrite are observed. The vein-type mineralization forms high grade stockworks and an extensive conjugate vein network that is anastomosed and showing locally some weak pinch and swell style deformation. The replacement-type mineralisation is lower grade and occurs as haloes around the vein-type mineralization or can solely occur within corridors of high-strain (figure 5 D-E). The replacement-style mineralization consists of a strong to moderate pervasive or patchy silica-sericite-carbonate-pyrite ± fuchsite alteration. A similar sulphide assemblage with visible gold is also observed for this mineralization type and pyrite can make up anywhere from 5 to 70 volume % of the rock.

windfall_mineralization@2x

Figure 4: Representative photographs of significant gold mineralisation styles in the Windfall deposit.

Mineral Zones

The most significant gold mineralization defined to date is currently known for a vertical extent of approximately 1,800 metres in three zones; the Lynx zone (Lynx Main, Lynx HW, Lynx SW, Triple Lynx, and Lynx 4), the Main zone (Zone 27, Caribou, Mallard, Windfall North and F-Zones), and the Underdog zone (including Triple 8) see figure 6. In general, the bulk of the gold mineralization in the Windfall deposit forms within a series of subvertical to moderately dipping zones that have a lensoid geometry 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 envelopes varies slightly from zone to zone 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 2020 Mineral Resource Estimate Update

  • Indicated Resource: 4.127 Mt at 9.1 g/t Au for 1.21 M oz Au;
  • Inferred Resource: 14.532 Mt at 8.4 g/t Au for 3.94 M oz Au;
  • Mineral resource estimate occurs above 1,200 m vertical depth;

The 2019 drilling increased the indicated mineral resource estimate by 60% (adding 452,000 ounces) and increased the inferred mineral resource estimate by 66% (adding 1,572,000 ounces). In addition, two bulk samples (Zone 27 and Lynx) have been successfully completed and returned positive results.

Table 1: Windfall Gold Deposit Mineral Resource Estimate by Area (3.5 g/t Au cut-off)

mineral_resource_table_1

Notes:

  1. Values are rounded to nearest thousand which may cause apparent discrepancies.
  2. Lynx area includes: Lynx Main, Lynx HW, Lynx SW and Lynx 4, Triple Lynx.
  3. Main area includes: Zone 27, Caribou, Mallard, Windfall Nord and F-Zones.
  4. See Windfall Gold Deposit Mineral Resource Estimate Notes further below.

Table 2: Windfall Gold Deposit Mineral Resource Estimate Sensitivity Table

mineral_resource_table_2

Notes:

  1. Values are rounded to nearest thousand which may cause apparent discrepancies.

Table 3: Parameters used to estimate the underground cut-off grade for the Windfall Gold Deposit Mineral Resource Estimation

mineral_resource_table_3

Windfall Gold Deposit Mineral Resource Estimate Notes:

  1. The Windfall mineral resource estimate is compliant with November 29, 2019 CIM (as defined below) standards and guidelines for reporting mineral resources and reserves.
  2. 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, were included in the mineral resource estimate.
  3. As of January 3, 2020, the database comprises a total of 2,941 drill holes for 1,101,008 metres of drilling in the area extent of the mineral resource estimate, of which 2,280 drill holes (918,273 metres) were completed and assayed by Osisko. The drill hole grid spacing is approximately 25 metre x 25 metre for infill drilling and larger for extension drilling.
  4. All core assays reported by Osisko were obtained by analytical methods described below under “Quality Control and Reporting Protocols”.
  5. 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 292 tabular, sub-vertical gold-bearing domains defined by individual wireframes with a minimum true thickness of 2.0 metres.
  6. Assays were composited within the mineralization domains into 2.0 metres length composites. A value of 0.00125 g/t Au (¼ of the detection limit) was applied to unassayed core intervals.
  7. 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 15 g/t Au to 130 g/t Au and are applied using a three-step capping strategy where the capping value decreases as interpolation search distances increase.
  8. Five (5) block models were produced using Datamine™ Studio RM Software. The models are defined by parent cell sizes of 5 metres NE, 2 meters NW and 5 metres height, and sublocked to minimum subcell sizes of 1.25 meters NE, 0.5 metres NW and 1.25 metres height.
  9. Ordinary Kriging (OK) based interpolations were produced for each area of the Windfall gold deposit. Estimation parameters are based on composite variography analyses.
  10.  Density values of 2.8 were applied to the mineralized zones.
  11.  The Windfall mineral resource estimate is categorized as indicated and inferred mineral resource as follows:
    1. 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, and reasonable geological and grade continuity is shown.
    2. 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, and reasonable, but not verified, geological and grade continuity is observed.
  12. The mineral resource is reported at 3.5 g/t Au cut-off. The cut-off grade is calculated using the following economic parameters: gold price at 1,325 US$/oz, exchange rate at 1.30 USD/CAD, 93% mill recovery; selling cost at 5 C$/oz, 2% NSR royalties, mining cost at 100 C$/t milled, G&A cost at 30 C$/t milled, processing cost at 40 C$/t, transportation cost at 2 C$/t considering mill at site, and environment cost at 4 C$/t.
  13. Estimates use metric units (metres, tonnes and g/t). Metal contents are presented in troy ounces (metric tonne x grade / 31.10348).
  14. Micon International Limited 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.
  15. These mineral resources are not mineral reserves as they do not have demonstrated economic viability. The quantity and grade of reported inferred mineral resources presented above(with an effective date of January 3, 2020) are uncertain in nature and there has been insufficient exploration to define these inferred mineral resources as indicated or measured mineral resources, and it is uncertain if further exploration will result in upgrading them to these categories.

mineral_resource_figure_5@2x

Figure 5: Mineralized domains modelled in the Windfall deposit. A) Longitudinal view (looking north); and B) Cross-section view (looking northeast). Source: Osisko, 2020.

Lynx Zone

The Lynx zone consists of five gold mineralized zones (Lynx Main, Lynx HW, Lynx SW, Triple Lynx and Lynx 4) that are located in the east-northeast portion of the deposit. The Lynx zone hosts an average grade of >10 g/t Au and contains the majority of the indicated and inferred mineral resource estimate. The Triple Lynx zone is the most recent discovery and was made back in early 2019. This new discovery added four new high-grade gold zones that are in the Lynx area of the deposit and are located at vertical depths varying between 650 and 950 m.

The Lynx zones are hosted in a felsic volcanic dominant domain that is cut by gabbro sills that are then crosscut by a series of QFP dikes and stocks (figure 7). Gold mineralization is hosted in extensive conjugate vein and alteration networks that trends northeast to east and plunges 35°. The vein network is currently mapped by drilling to extend 2 kilometers and is still open down plunge at depth. Gold in the Lynx zone is hosted in vein-type mineralization that is associated with haloes of a pervasive sericite-pyrite ± silica alteration and pyrite-quartz veinlets in the host rocks that form envelopes that reach tens of metres thick. Fuchsite alteration is common in the Lynx zone and is spatially constrained to nearby gabbro sills. The Lynx zones are all very similar in terms of mineralization styles, but from zone to zone there are small variations in orientation and locally some overprinting ductile deformation when proximal to late regional scale shear zones.

mineral_resource_figure_6@2x

Figure 6: Cross-section of the Lynx Zone. Source Osisko, 2020.

Main Zone

The Main zone consists of three gold mineralized zones (Zone 27, Caribou, and Mallard) that are located above the post-mineral Red Dog intrusion (figure 7) in the central portion of the deposit. The Main zone hosts an average grade of 6.2 g/t Au. The zone is hosted in mafic to intermediate volcanic rocks and lesser felsic volcanics that are crosscut by two large QFP stocks (I2P and I1P YL) that are then crosscut by a swarm of thin QFP dikes (I1P Try). The gold mineralization is mostly concentrated in deformation zones that are located along the contacts between the QFP dike swarm and the host volcanic sequence. Most of the gold mineralization in these zones is associated with a replacement-type mineralization consisting of corridors of intense silica-sericite-pyrite alteration that are cut by stockworks of thin and densely packed pyrite-quartz veinlets.

Underdog Zone

The Underdog zone is located below the post-mineral Red Dog intrusion (figure 7), the top of the zone starts at approximately 600 metres depth and continues to 1400 meters where it is still open down plunge. What separates the Underdog zone from the Main and Lynx zones is that it is mostly hosted in a large multiphase intrusive stock that is composed of several intrusive phases, mainly the I2P, I1P YL and the I1P YB rock types. Gold mineralization in Underdog is dominated by replacement-type mineralization. This consists of extensive altered deformation corridors that develop over great lengths and consists of envelopes of silica-sericite-pyrite alteration and that are crosscut by quartz-pyrite veins and veinlets with disseminated pyrite and visible gold.

mineral_resource_figure_7@2x

Figure 7: Cross-section of the Main and Underdog zones. Source Osisko, 2020.

Triple 8 Zone

In May of 2018, Osisko commenced two deep exploration drill holes to investigate the potential for the extension of the Underdog mineralized zone at depth. The first drill hole was successful and outlined the new Triple 8 zone, encountered at a downhole depth of 1,500 m. The Triple 8 zone is located 660 m east-northeast from the closest mineralized intercept in the Underdog Zone. The second 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 mineralization in the Triple 8 zone is a replacement-type mineralization that crosscuts a basalt and consists of a 30 m corridor of silica-sericite-pyrite alteration that is cut by a stockwork of pyrite-quartz ± tourmaline veins and veinlets. Locally pyrite concentrations reach upwards of 50 volume % and visible gold is common. Due to its depth and lack of drilling, the Triple 8 zone is not considered in the resource estimate at this stage.

F-Zones and Windfall North

The F-zones (F-11, F-17, and F-51) and Windfall North are smaller zones that are located in the northwestern portion of the deposit. These zones have a similar orientation to the main mineralized corridors in the deposit, but have a weaker intensity in terms of mineralization, alteration, and deformation. The zones crosscut a package of mafic to intermediate volcanics that are cut by narrow QFP intrusions (I2P and I1P YL). The structural controls are similar and gold mineralization is localized in deformation zones that located along the contacts of the QFP dikes. The gold is hosted in a replacement-type mineralization which consists of narrow corridors of moderate to strong sericite-carbonate-pyrite and weak silica alteration that is cut by a stockwork of thin pyrite-quartz veinlets.

Deposit Type

The classification of the Windfall deposit has significantly evolved since the acquisition of the project by Osisko Mining. The Main Zone 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 to 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 earliest phases of QFP dikes were emplaced in east-northeast trending fault zones that formed during the early stages of a regional scale deformation event. Continued east-northeast deformation created high-strain and fracture zones in areas of rheological anisotropies (i.e. along contacts between volcanic and QFP dike rocks) which then channelled the gold-rich hydrothermal fluids. This is then overprinted again by continued east-northeast deformation. This east-northeast deformation event that controlled the emplacement of the dike rocks and the mineralization, is then cut by gold-barren north-trending deformation zones which controlled the emplacement of the post-mineral QFP intrusions (i.e. Red Dog).

The Windfall deposit is currently best classified as an atypical orogenic type or an intrusion-associated type. Although there is a strong spatial and temporal association of gold with felsic magmatism, the true control is structural, and the gold appears to be synchronous with a regional scale deformation event occurring ca. 2698 Ma.

Bulk Samples

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.

Geology

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.

Processing

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.

Reconciliation

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:

Table 1: Zone 27 Bulk Sample Reconciled Results

bulk_sample_zone_27_table_1

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.

Block Model

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).

Table 2: Infill Resource Block Model Predictions vs. Actual Processed

bulk_sample_zone_27_table_2

Concentrate

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

Geology

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.

Processing

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.

Reconciliation

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:

Table 1: Lynx Bulk Sample Reconciled Results

bulk_sample_lynx_table_1

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.

Block Model

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).

Table 2: Infill Resource Block Model Predictions vs. Actual Processed

infill_lynx_table_2

Concentrates

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.

Technical Reports

09 Dc Data Center 9.001
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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

03/04/2020

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NI 43-101 Technical Report: Preliminary Economic Assessment of the Windfall Lake Project, Lebel-sur-Quévillon, Québec, Canada

01/08/2018

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NI 43-101 Technical Report and Mineral Resource Estimate for the Windfall Lake Project, Windfall Lake and Urban-Barry Properties

12/06/2018

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Maps and Sections

General Maps

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Figure 1: Map showing the location of the Windfall project.

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Figure 2: Simplified regional geology map showing the location of the Urban Barry greenstone belt.

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Figure 3: Representative photographs of syn-deformation QFP intrusive rocks from the Windfall intrusive complex in order from earliest to the latest . Dating of the I2P and of the Red Dog dike were done using TIMS U-Pb of zircon by D. Davis at the University of Toronto. The dating of the I13 dike was done by C. Azevedo using HR-ICP-MS U-Pb of zircon at the Geotop Laboratory at the University of Québec.

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Figure 4: Representative photographs of significant gold mineralisation styles in the Windfall deposit.

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Figure 5: Mineralized domains modelled in the Windfall deposit. A) Longitudinal view (looking north); and B) Cross-section view (looking northeast). Source: Osisko, 2020.

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Figure 6: Cross-section of the Lynx Zone. Source Osisko, 2020.

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Figure 7: Cross-section of the Main and Underdog zones. Source Osisko, 2020.

Press Release Maps

OSISKO INFILL DRILLING WINDFALL. GOOD., 24/11/20OSISKO WINDFALL INFILL DRILLING INTERSECTS SOME MORE GOLD, 17/11/20OSISKO WINDFALL INFILL DRILLING RETURNS MORE OF THE SAME, 05/11/2020OSISKO INFILL DRILLING RETURNS HIGH GRADE AT WINDFALL, 08/10/2020OSISKO STEP-OUT DRILLING EXPANDS HIGH GRADE AT WINDFALL, 07/10/2020OSISKO INTERSECTS 115 g/t Au OVER 5.6 METRES AT WINDFALL, 01/09/2020OSISKO INTERSECTS 202 g/t Au OVER 9.0 METRES AT WINDFALL, 10/08/2020OSISKO EXPANSION DRILLING RETURNS HIGH GRADE AT LYNX, 16/07/2020OSISKO INFILL DRILLING CONTINUES TO CONFIRM HIGH GRADE AT LYNX, 14/07/2020OSISKO INFILL DRILLING CONTINUES TO CONFIRM HIGH GRADE AT LYNX, 23/06/2020OSISKO INFILL DRILLING INTERSECTS HIGH GRADE IN LYNX, 29/04/2020OSISKO INFILL DRILLING RETURNS MORE HIGH GRADE VALUES IN LYNX, 14/04/2020OSISKO EXPANSION DRILLING INTERSECTS HIGH GRADE AT WINDFALL, 07/04/2020OSISKO INFILL DRILLING CONTINUES TO INTERSECT HIGH GRADE, 31/03/2020OSISKO EXTENTION AND INFILL DRILLING INTERSECTS HIGH GRADE AT LYNX AND TRIPLE LYNX, 09/03/2020OSISKO WINDFALL RESULTS FROM DISCOVERY 1 DEEP DRILL HOLE, 25/02/2020OSISKO WINDFALL UPDATED MINERAL RESOURCE ESTIMATE, 19/02/2020OSISKO COMPLETES DISCOVERY 1 DEEP DRILL HOLE, 29/01/2020OSISKO INTERSECTS HIGH-GRADE AT WINDFALL, 09/01/2020OSISKO INTERSECTS HIGH GRADE AT LYNX, 18/12/2019OSISKO INTERSECTS 1475 G/T AU OVER 4.6 METRES IN LYNX, 16/12/2019OSISKO WINDFALL UPDATE ON DISCOVERY 1 DEEP DRILL HOLE, 10/12/2019OSISKO MINING RECAPS WINDFALL DRILL PROGRAM AND 
50 TOP INTERCEPTS, 09/12/2019OSISKO INTERSECTS 106 g/t Au OVER 13 METRES IN LYNX EXTENSION, 02/12/2019OSISKO INTERSECTS 161 G/T AU OVER 8.0 METRES AT WINDFALL, 25/11/2019OSISKO INTERSECTS HIGH GRADE IN THREE LYNX ZONES, 21/10/2019OSISKO MINING RELEASES DISCOVERY 1 PRELIMINARY RESULTS, 11/09/2019OSISKO INTERSECTS BONANZA GRADES AT LYNX EXTENSION AND TRIPLE LYNX, 09/09/2019OSISKO INFILL DRILLING INTERSECTS HIGH-GRADE AT LYNX, 05/09/2019OSISKO INTERSECTS 114 G/T AU OVER 2.8 METRES AT OSBORNE-BELL, 03/09/2019OSISKO DISCOVERS SIGNIFICANT NEW WIDE HIGH-GRADE GOLD ZONE, 23/07/2019OSISKO INFILL DRILLING CONTINUES TO INTERSECT HIGH-GRADE AT LYNX, 08/07/2019OSISKO INFILL DRILLING CONTINUES TO INTERSECT HIGH-GRADE AT LYNX, 17/06/2019OSISKO DISCOVERS NEW GOLD ZONE AT FOX, 06/06/2019OSISKO 400 METRE HIGH-GRADE EXTENSION AT LYNX, 03/06/2019OSISKO INFILLS NEW HIGH GRADE AT LYNX, 30/05/2019OSISKO DISCOVERS NEW NEAR SURFACE HIGH-GRADE GOLD ZONE AT WINDFALL, 28/05/2019OSISKO TO BEGIN DRILLING “DEEP DISCOVERY 1” AT WINDFALL, 30/04/2019OSISKO INTERSECTS 489 G/T AU OVER 3.7 METRES AT WINDFALL, 25/04/2019OSISKO EXTENDS LYNX DEPOSIT 100 METRES DOWN PLUNGE, 16/04/2019WINDFALL TRIPLE 8 DOWNHOLE IP SURVEY SUCCESSFULLY OUTLINES NEW TARGETS, 26/03/2019OSISKO LYNX INFILL DRILLING CONTINUES TO RETURN HIGH GRADES, 21/03/2019OSISKO WINDFALL INFILL DRILLING CONTINUES TO INTERSECT HIGH GRADE, 19/03/2019OSISKO EXPANDS TRIPLE 8 DISCOVERY, 16/01/2019OSISKO INTERSECTS 2223 G/T AU OVER 2.0 METRES AT WINDFALL, 07/01/2019OSISKO INFILL 38.9 G/T AU OVER 13.7 METRES AT UNDERDOG, 05/12/2018OSISKO INTERSECTS 83.9 G/T AU OVER 5.3 METRES AT LYNX, 21/11/2018OSISKO INTERSECTS 1026 G/T AU OVER 2.7 METRES AT LYNX, 23/10/2018OSISKO INTERSECTS 49.1 G/T AU OVER 6.6 METRES AT LYNX, 02/10/2018OSISKO WINDFALL DEEP DRILLING CONFIRMS TRIPLE 8 DISCOVERY, 13/09/2018OSISKO WINDFALL INFILL DRILLING CONTINUES TO CONFIRM HIGH-GRADE, 22/08/2018OSISKO WINDFALL INFILL DRILLING CONFIRMING SHALLOW MINERALIZED ZONES, 08/08/2018OSISKO DEEP DRILLING GOLD DISCOVERY AT WINDFALL, 07/08/2018OSISKO INFILL DRILLING CONFIRMING HIGH-GRADE MINERALIZATION AT WINDFALL, 25/07/2018OSISKO DEEP DRILLING GOLD DISCOVERY AT WINDFALL NEW WIDE HIGH-GRADE TRIPLE 8 ZONE 20.4 G/T AU OVER 28.3 METRES INCLUDING 44.5 G/T OVER 10.0 METRES, 81.1 G/T OVER 4.0 METRES, 18/07/2018OSISKO INTERSECTS 20.0 G/T AU OVER 8.7 METRES AT WINDFALL, 12/06/2018OSISKO INTERSECTS 97.6 G/T AU OVER 3.3 METRES AT LYNX, 07/06/2018OSISKO INTERSECTS 34.3 G/T AU OVER 4.5 METRES AT WINDFALL, 01/05/2018OSISKO INTERSECTS 115 G/T AU OVER 8.4 METRES AT LYNX, 26/04/2018OSISKO INTERSECTS 41.2 G/T AU OVER 3.5 METRES AT WINDFALL, 19/04/2018OSISKO INTERSECTS 68.5 G/T AU OVER 2.9 METRES AT LYNX, 17/04/2018OSISKO INTERSECTS 40.8 G/T AU OVER 4.1 METRES AT WINDFALL, 10/04/2018OSISKO INTERSECTS 403 G/T AU OVER 2.7 METRES AT LYNX, 05/04/2018OSISKO INTERSECTS 265 G/T AU OVER 2.4 METRES AT WINDFALL, 02/03/2018OSISKO INTERSECTS 56.1 G/T AU OVER 8.9 METRES AT WINDFALL, 25/01/2018OSISKO INTERSECTS 415 G/T AU OVER 5.9 METRES AT LYNX, 23/01/2018OSISKO INTERSECTS 86.7 G/T AU OVER 4.3 METRES AT WINDFALL, 18/01/2018OSISKO INTERSECTS 76.5 G/T AU OVER 5.0 METRES AT WINDFALL, 16/01/2018OSISKO INTERSECTS 140 G/T AU OVER 5.0 METRES AT LYNX, 09/01/2018OSISKO INTERSECTS 30 G/T AU OVER 2.4 METRES AT WINDFALL, 05/12/2017OSISKO INTERSECTS 479 G/T AU OVER 2.0 METRES AT LYNX, 28/11/2017OSISKO CARIBOU EXTENSION INCREASES TO 1.2 KILOMETRES AT WINDFALL, 16/11/2017OSISKO INTERSECTS 301 G/T AU OVER 6.2 METRES AT LYNX, 14/11/2017OSISKO INTERSECTS 17.8 G/T AU OVER 4.7 METRES AT WINDFALL, 01/11/2017OSISKO INTERSECTS 20.5 G/T AU OVER 11.6 METRES AT LYNX, 30/10/2017OSISKO INTERSECTS 39.4 G/T AU OVER 2.4 METRES AT WINDFALL, 25/10/2017OSISKO INTERSECTS 31.4 G/T AU OVER 6.0 METRES AT WINDFALL, 18/10/2017OSISKO INTERSECTS 61.8 G/T AU OVER 2.5 METRES AT LYNX, 12/10/2017OSISKO INTERSECTS 27 G/T AU OVER 2.7 METRES AT LYNX, 03/10/2017OSISKO INTERSECTS 611 G/T AU OVER 2.0 METRES AT WINDFALL, 20/09/2017OSISKO INTERSECTS 36 G/T AU OVER 6.9 METRES AT LYNX, 18/09/2017OSISKO INCREASES DRILL PROGRAM AT WINDFALL TO 800,000 METRES, 25/08/2017OSISKO INTERSECTS 36.7 G/T AU OVER 4.0 METRES AT WINDFALL, 24/08/2017OSISKO INTERSECTS 53.5 G/T AU OVER 3.0 METRES AT WINDFALL, 14/08/2017OSISKO INTERSECTS 379 G/T AU OVER 2.0 METRES AT WINDFALL, 09/08/2017OSISKO INTERSECTS 63.2 G/T AU OVER 7.7 METRES AT WINDFALL, 01/08/2017OSISKO INTERSECTS 57.0 G/T AU OVER 2.7 METRES AT LYNX, 25/07/2017OSISKO INTERSECTS 24.9 G/T AU OVER 31 METRES AT WINDFALL, 19/07/2017OSISKO INTERSECTS 131 G/T AU OVER 2 METRES IN LYNX DEPOSIT, 12/07/2017OSISKO INTERSECTS 12.5 G/T AU OVER 8.5 METRES AT WINDFALL, 07/06/2017OSISKO INTERSECTS 97.4 G/T AU OVER 8.4 METRES AT WINDFALL, 30/05/2017OSISKO INTERSECTS 42.4 G/T AU OVER 4.7 METRES AT WINDFALL, 24/05/2017OSISKO INTERSECTS 9.01 G/T AU OVER 9.4 METRES AT WINDFALL, 19/05/2017OSISKO INTERSECTS 11.7 G/T AU OVER 7.7 METRES IN NEW LYNX 4 DISCOVERY, 10/05/2017OSISKO INTERSECTS 936 G/T AU OVER 2.5 METRES AT WINDFALL, 03/05/2017OSISKO INTERSECTS 35.2 G/T AU OVER 2.8 METRES AT WINDFALL, 25/04/2017OSISKO INTERSECTS 19.4 G/T AU OVER 7.9 METRES AT WINDFALL, 11/04/2017OSISKO INTERSECTS 34.1 G/T AU OVER 4.0 METRES AT WINDFALL, 06/04/2017OSISKO INTERSECTS 63.8 G/T AU OVER 4.4 METRES AT WINDFALL, 05/04/2017OSISKO INTERSECTS 8.37 G/T AU OVER 2.8 METRES AT FOX, 04/04/2017OSISKO INTERSECTS 71.4 G/T AU OVER 5.4 METRES AT WINDFALL, 28/03/2017OSISKO INTERSECTS 15.6 G/T AU OVER 5.8 METRES AT WINDFALL, 22/03/2017OSISKO INTERSECTS 64.3 G/T AU OVER 2.3 METRES AT WINDFALL, 15/02/2017OSISKO INTERSECTS 9.76 G/T AU OVER 7.3 METRES AT WINDFALL, 14/02/2017OSISKO INTERSECTS 12.7 G/T AU OVER 5.4 METRES AT WINDFALL, 23/01/2017OSISKO EXPANDS BLACK DOG AU-AG-CU DISCOVERY, 18/01/2017OSISKO INTERSECTS 42.7 G/T AU OVER 9.0 METRES AT WINDFALL, 11/01/2017OSISKO INTERSECTS 47 G/T AU OVER 2.6 METRES AT WINDFALL, 05/01/2017OSISKO INTERCEPTS 6.14 G/T AU OVER 14.4 METRES AT BLACK DOG, 06/12/2016OSISKO INTERSECTS 65 G/T AU OVER 5.7 M AT WINDFALL EXTENSION DISCOVERY, 05/12/2016OSISKO INTERSECTS 27.6 G/T AU OVER 3.1 METRES AT FOX, 23/11/2016OSISKO INTERSECTS 6.1 G/T AU OVER 35.4 METRES AT WINDFALL, 08/11/2016OSISKO MAKES NEW GOLD DISCOVERY IN URBAN TOWNSHIP, 29/08/2016

Long Sections

Composite longitudinal section of the Windfall Gold DepositOSISKO INFILL DRILLING RETURNS HIGH GRADE AT WINDFALL, October 8, 2020 Zone 27 before OsiskoZone 27 with OsiskoCaribou Zone before OsiskoCaribou Zone with OsiskoFW3 Longsection UpdatedResources Expansion Planning September 2016

Drill Results

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Windfall - October 2019

01/10/2019

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Windfall - June 2019

01/06/2019

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Windfall - March 2019

01/03/2020

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Windfall - January 2019

01/01/2019

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Windfall - October 2018

01/10/2018

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Windfall - August 2018

01/08/2018

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Windfall - May 2018

01/05/2020

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Windfall - January 2018

01/01/2018

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Windfall - December 2017

01/12/2017

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Windfall - November 2017

01/11/2017

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Windfall - October 2017

01/10/2017

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Windfall - September 2017

01/09/2017

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Windfall - August 2017

01/08/2017

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Windfall - July 2017

01/07/2017

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Windfall - May 2017

01/05/2017

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Windfall - March 2017

01/03/2017

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Infrastructure

Surface Infrastructure

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

Exploration Ramp

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

Environment

CLOSURE PLAN

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Windfall – 01 – Closing Plan – Mise à jour du plan de restauration 2017 (French)

July 1, 2017

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Windfall – 01a – Closing Plan – Questions et réponses – Mise à jour du plan de restauration 2017 (French)

April 1, 2018

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Windfall – 02 – Closing Plan – Complément d’information 1 – Premier agrandissement de la halde (French)

December 1, 2018

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Windfall – 02a – Closing Plan – Questions et réponses 1 – Complément d’information 1 (French)

July 1, 2019

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Windfall – 02b – Closing Plan – Questions et réponses 2 – Complément d’information 1 (French)

October 1, 2019

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Windfall – 03 – Closing Plan – Complément d’information 2 – Deuxième agrandissement de la halde (French)

June 1, 2020

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Project descriptions and summaries

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Federal Project Description

June 17, 2017

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Federal Project Description – Summary

June 12, 2017

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Provincial Preliminary Project Information

May 23, 2017

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