OceanaGold : JORC Table Macraes March 31 2022

31 March 2022

TABLE 1 – 2012 JORC: Macraes Gold Mine

OceanaGold Corporation (TSX:OGC)(ASX:OGC) (the “Company”) refers to the announcement released by the Company dated 31 March 2022 titled OCEANAGOLD REPORTS MINERAL RESOURCES AND RESERVES FOR THE YEAR-ENDED 2021 and hereby encloses TABLE 1 – 2012 JORC: Macraes

Gold Mine relating to the announcement.

SUMMARY OF TABLE 1 – 2012 JORC: Macraes Gold Mine

A Material Information Summary pursuant to ASX Listing Rules 5.8 and 5.9 is provided below for the Macraes Gold Project (MGP) which includes both open pit and underground mining, ore processing and a single economic analysis based on combined open pit and underground Mineral Reserves as at December 31, 2021.

MGP is controlled by OceanaGold Corporation through its wholly owned subsidiary OceanaGold (New Zealand) Limited (“Oceana”). OceanaGold is listed on the Toronto and Australian stock exchanges under the code “OGC” and is the Issuer of this Technical Report.

The areas included in the Project comprise the following:

  • Coronation North, Coronation, Deepdell, Round Hill, Innes Mills, Frasers West and Gay Tan open pits;

  • Frasers Underground mine and a new underground mine at Golden Point;

  • Processing plant; and

  • Tailings Storage Facilities, including a new storage facility that is currently being investigated for storage from 2024

The Assessment and Reporting Criteria in accordance with JORC Code 2012 is presented in Appendix 1.

1.0 Macraes Gold Project

The Macraes Gold Project (MGP) is located 91 km northwest of Dunedin, in the Otago Region of the South Island, New Zealand. The MGP is located 1-2km to the east of the Macraes Flat township and is predominantly surrounded by farmland. Modern open pit mining commenced in 1990 and underground mining commenced in 2006. OceanaGold (NZ) Limited (OceanaGold) holds most of the necessary permits, consents, certificates, licenses, and agreements required to operate the open pits and underground mines that form MGP. During 2020 work commenced on obtaining the necessary resource consents to add an uplift to the Top Tipperary Tails dam and to fully backfill the Frasers open pit with waste or tails. OceanaGold has a 31 year history of obtaining the necessary permits, consents, certificates, licenses, and agreements required for mining.

MGP comprises a number of areas that are at different stages of mining development. Coronation North, Deepdell, Gay Tan, Frasers West, Golden Point Underground and the Frasers Underground are in production and are the ore sources for 2022. Resource development drilling continued in 2021 and in 2022 further drilling will take place at Golden Point / Round Hill and Innes Mills. Resource development drilling is expected to continue in 2023 and beyond.

1.1 Geology and Geological Interpretation

The Macraes orogenic gold deposits, consisting of a series of 12 open pits and 2 underground mines, which are located within a low-angle (~15-20°) late metamorphic (Jurassic) shear zone called the Hyde Macraes Shear Zone (HMSZ) , which has been traced for at least 30km along strike (Error! Reference source not found.). The HMSZ consists of variably altered, deformed, and mineralized quartzo-feldspathic schist up to 150m thick, known as the Intra-shear Schist. The thickest part of the shear zone consists of several stacked mineralized zones. These shears have ductile deformation textures overprinted by cataclasis. The top of the HMSZ ismarked by a distinctive structure (‘hanging wall shear‘) up to 25m thick that is commonly darker colored than adjacent schist due to fine grained graphite and sheared sulphide minerals.

The following four types of mineralization occur within the HMSZ at Macraes:

  • Mineralized schist. This style of mineralization involved hydrothermal replacement of schist minerals with sulphides and microcrystalline quartz. Mineralization was accompanied by only minor deformation.

  • Black sheared schist. This type of schist is pervaded by cm to mm scale anastomosing fine graphite and sulphide bearing micro shears. This type of mineralization is typically proximal to the Hangingwall Shear and can be up to 1m to 15m thick. Scheelite mineralization occurs in the silicified cataclastic shears.

  • Shear-parallel quartz veins. These veins lie within and/or adjacent to the black sheared schist and have generally been deformed with the associated shears. The veins locally cross-cut the foliation in the host schist at low to moderate angles. Veins are mainly massive quartz, with some internal lamination and localized brecciation. Sulphide minerals are scattered through the quartz, aligned along laminae and stylolitic seams. These veins range in thickness from 1cm to > 2m. Scheelite mineralization is associated with quartz veining in some areas.

  • Stockwork. These veins occur in localized swarms that are confined to the Intrashear Schist. Individual swarms range from c. 100mtwo to 2,000mtwo in area and consist of numbers (10 100) subparallel veins. Most of these veins formed sub-perpendicular to the shallow east dipping shear fabric of the Intrashear Schist. Individual veins typically extend 1-5m vertically with most filling fractures that are 5 10cm wide but can be up to 1m thick. Swarms of stockwork veins within the Intrashear Schist were lithologically controlled by the dimensions and locations of more competent psammite pods within the Intrashear Schist.

Figure 1: MGP Geology Plan & Pit Location

1.2 Drilling, Sampling and Sub-Sampling

Between 1990 – 2021 over 7,500 surface drill holes for >1,000,000 m and over 3,000 underground diamond holes for nearly 150,000 m have been completed at MGP and used for resource estimation. About 80% of the surface holes are RC. The main ore minerals are pyrite and arsenopyrite sulphides with ubiquitous gangue consisting of quartz, sheared schist with a trace of graphite.

Resources at the MGP are defined using a combination of predominantly reverse circulation (RC) drilling and diamond drilling.

RC samples were collected as bulk samples in 1 meter intervals and riffle split into uniquely numbered sample bags to produce a 2 to 4 kg sub-sample. Geological logging and sampling were completed at the drill site using Tough books. At conclusion of the drill hole the samples are taken directly to the onsite laboratory operated by SGS (NZ) Ltd.

Diamond core is geologically logged, photographed and sawn in half with a diamond saw. In general samples are 1 m in length unless dictated to by significant geological or mineralization contacts in the core. The half-cut core samples are then delivered to the onsite lab operated by SGS (NZ) Ltd.

All drill hole collars are picked up by mine surveyors. Drill holes are routinely surveyed downhole on a 25 m or 30 m interval.

The quantity and quality of the lithological, geotechnical, geochemical data collected in the exploration, surface resource delineation, underground resource delineation and grade control drill programs are considered sufficient to support the Mineral Resource and Ore Reserve estimation.1.3 Sample Analysis methods

At MGP, OceanaGold operates an assay laboratory under contract to SGS (NZ) Ltd. QAQC procedures include the routine use of certified reference materials (CRM), lab standards, lab and field duplicates and field blanks. Sample batches are re-assayed if 1 of the OceanaGold CRM’s is outside 3 standard deviations. The performance of CRMs, field duplicates and blanks are actively monitored and reported.

RC samples are dried and crushed to nominal 2 mm. The crusher is integrated with a splitter to produce a 350 gram sub-sample. The entire sub-sample is pulverized to 90% passing 75 microns. A 30 gram aliquot is split for fire assay using SGS’s GO_FAA30V10 scheme which has a detection limit of 0.01 g/t Au.

Diamond core samples are dried and the entire sample pre crushed to nominal 25 mm. The entire sample is then crushed to nominal 2 mm. The crusher is integrated with a splitter to produce a 350 gram sub-sample. The entire sub-sample is pulverized to 90% passing 75 microns. A 30gram aliquot is split for fire assay using SGS’s GO_FAA30V10 scheme which has a detection limit of 0.01 g/t Au.

1.4 Estimation Methodology

Grade estimation for open pit resources is by large panel (25 mE x 25 mN x 2.5 mRL) recoverable resource estimates using either ordinary kriging or multiple indicator kriging (MIK) using FSSI proprietary GS3 software. Grades are estimated into 25 mx 25 mx 2.5 m panels which are approximately 70% the nominal drill hole spacing. A mining selectivity of 5 mE x 10 mN by 2.5 mRL is assumed.

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