Osisko Windfall Update on Discovery 1 Deep Drill Hole

TORONTO, Dec. 10, 2019 (GLOBE NEWSWIRE) — Osisko Mining Inc. (OSK:TSX. “Osisko” or the “Corporation”) is pleased to provide an update on the Discovery 1 (OSK-W-19-1970) drill hole. Discovery 1 is a planned 3000 metre to 3500 metre deep drill hole, designed to target two down plunge extensions of known gold zones and investigate the projected source area of the Windfall deposit at depth. The working model for the Windfall deposit interprets an outer shell and centre of a possible porphyry intrusion feeding the Windfall-Lynx gold system.
Prior results from Discovery 1 included successful intersections in the targeted Underdog Zone (500 metre extension:  14.1 g/t Au over 2.1 metres), and the Triple 8 Zone (100 metre extension:  9.58 g/t Au over 7.6 metres) (see Osisko news release dated September 11, 2019).Discovery 1 completed approximately 2275 metres before requiring a wedge at 2170 metres to drill past blocked rods.  To date, the hole has progressed to 3225 metres of the planned 3500 metres.The drill hole has intersected several wide zones of anomalous gold mineralization between 2300 metres – 2900 metres down-hole. Analytical results below 2900 metres are pending. The newly detected anomalous gold zones range up to 116 metres in length, and occur in chlorite, sericite, and biotite altered andesites.  Wide zones of anomalous gold have similarly been observed in the proximity of Triple 8, Triple Lynx, and Lynx zones.Osisko President and Chief Executive Officer John Burzynski commented: “Discovery 1 gave early dividends with the discovery of the Underdog and Triple 8 extensions. As we approach the main target depth, these wide intercepts of anomalous gold values are a positive indication that we may be approaching another mineralized zone. We are at the really interesting part of this hole as Discovery 1 continues its voyage to the hypothetical roots and feeder system of the Windfall deposit.”Maps showing hole locations and full analytical results are available at www.osiskomining.com.
Qualified Person
The scientific and technical content of this news release has been reviewed, prepared and approved by Mr. Louis Grenier, M.Sc.A., P.Geo. (OGQ 800), Project Manager of Osisko’s Windfall Lake gold project, who is a “qualified person” as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects (“NI 43-101”).Quality Control and Reporting Protocols
True width determination is estimated at 55-80% of the reported core length interval for the zone. Assays are uncut except where indicated. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Reported intervals include minimum weighted averages of 3.0 g/t Au diluted over core lengths of at least 2.0 metres. All NQ core assays reported were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at (i) ALS Laboratories in Val d’Or, Québec, Thunder Bay, Ontario, Sudbury, Ontario or Vancouver, British Colombia, or (ii) Bureau Veritas in Timmins, Ontario. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. Selected samples are also analyzed for multi-elements, including silver, using an Aqua Regia-ICP-AES method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control (“QA/QC”) and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes by the Corporation as well as the lab. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.About the Windfall Lake Gold Deposit
The Windfall Lake gold deposit is located between Val-d’Or and Chibougamau in the Abitibi region of Québec, Canada. The mineral resource defined by Osisko, as disclosed in the Windfall Lake Technical Report (as defined below) and November 27, 2018 Lynx resource update, comprises 2,874,000 tonnes at 8.17 g/t Au (754,000 ounces) in the indicated mineral resource category and 10,352,000 tonnes at 7.11 g/t Au (2,366,000 ounces) in the inferred mineral resource category. For details regarding the key assumptions, parameters and methods used to estimate the mineral resources presented in respect of the Windfall Lake gold project, please see the technical report entitled “Technical Report and Mineral Resource Estimate for the Windfall Lake Project, Windfall Lake and Urban-Barry Properties” and dated June 12, 2018 (effective date of May 14, 2018), which has been prepared by InnovExplo Inc. from Val-d’Or, Québec (the “Windfall Lake Technical Report”) and the press release “Osisko Releases Mineral Resource Update for Lynx” dated November 27, 2018, which has been prepared by Osisko and reviewed and approved by Micon International, Ltd. from Toronto, Ontario. The Windfall Lake Technical Report and press release are available on Osisko’s website at www.osiskomining.com and on SEDAR under Osisko’s issuer profile at www.sedar.com. The Windfall Lake gold deposit is currently one of the highest-grade resource-stage gold projects in Canada. Mineralization occurs in four principal zones: Lynx, Zone 27, Caribou and Underdog. All zones comprise sub-vertical lenses following intrusive porphyry contacts plunging to the northeast. The deposit is well defined from surface to a depth of 900 metres and remains open along strike and at depth. Mineralization has been identified 30 metres from surface in some areas and as deep as 2,000 metres in others, with significant potential to extend mineralization down-plunge and at depth.