OGC.TO · 2023-08-15 12:00:00

OceanaGold Extends Mineralization Below Existing Resource at Didipio

Drill Results

August 15, 2023 News Release

(VANCOUVER) OceanaGold Corporation (TSX: OGC) (“OceanaGold” or the “Company”) is pleased to

announce year to date results from our ongoing 2023 drill program at the Didipio Mine in the Philippines.

The 2023 drill program is 45% complete, focused on resource growth and conversion of Inferred Resources.

Highlights from extensional drill intercepts include 1,2:

• 72.0 m @ 3.40 g/t AuEq (2.44 g/t Au and 0.69% Cu) (RDUG611) (Didipio Deeps)

• 18.6 m @ 4.24 g/t AuEq (2.56 g/t Au and 1.20% Cu) (RDUG465) (Eastern Breccia)

• 30.0 m @ 2.08 g/t AuEq (1.16 g/t Au and 0.66% Cu) (RDUG467) (Eastern Breccia)

• 21.0 m @ 1.65 g/t AuEq (0.90 g/t Au and 0.54% Cu) (RDUG466) (Eastern Breccia)

Highlights from resource conversion drill intercepts include 1,2.:

• 218.0 m @ 4.55 g/t AuEq (3.39 g/t Au and 0.83% Cu) (RDUG603) (Northern Monzonite)

• 86.5 m @ 5.35 g/t AuEq (4.22 g/t Au and 0.81% Cu) (RDUG481) (Balut Dyke)

• 197.0 m @ 2.23 g/t AuEq (1.47 g/t Au and 0.55% Cu) (RDUG602) (Northern Monzonite)

• 132.0 m @ 2.30 g/t AuEq (1.52 g/t Au and 0.56% Cu) (RDUG475) (Northern Monzonite)

• 56.1 m @ 3.51 g/t AuEq (2.90 g/t Au and 0.44% Cu) (RDUG484) (Balut Dyke)

• 62.0 m @ 1.56 g/t AuEq (1.07 g/t Au and 0.35% Cu) (RDUG492) (Balut Dyke)

• 49.0 m @ 1.83 g/t AuEq (1.38 g/t Au and 0.33% Cu) (RDUG611) (Didipio Deeps)

• 13.2 m @ 3.01 g/t AuEq (1.65 g/t Au and 0.98% Cu) (RDUG611) (Didipio Deeps)

Resource conversion drill results are in line with and support historic drilling within the resource model shell.

Gerard Bond, President & CEO of OceanaGold said, “Our 2023 drilling program at Didipio has delivered

exceptional results to date, supporting our focus on creating value through near-mine exploration targeting

resource growth and conversion. Drilling continues to improve confidence within the Inferred portions of the

deposit and supports potential reserve growth and our target to increase underground mining rates to at

least 2 million tonnes per year, approximately 20% above current underground mining rates. The drilling has

also identified exciting extensions beyond known mineralization at the Didipio Deeps, Eastern Breccia and

the Balut Dyke, representing significant upside potential outside of existing resources.”

1 AuEq is calculated as Au g/t + 1.39 x Cu %

2 Drill results are presented as core lengths (not true widths)

Overview

Since December 2022, 9,172 metres of resource conversion and extensional drilling in 45 holes has been

completed year to date (“YTD”) and the Company is on track to complete 20,250 metres (“m”) in 2023

(Figures 1 and 2). Extensional drilling has identified new areas of porphyry gold-copper mineralization 100m

below existing Inferred Resources within the Didipio Deeps target (previously untested), extensions of the

Balut Dyke to the west, and depth extensions of known mineralization within the Eastern Breccia. These

targets all remain open for extension beyond the existing resource.

Resource conversion drilling of Inferred Resources, utilising the same holes as extensional drilling, has also

successfully returned broad intersections of high-grade gold-copper mineralization within the Balut Dyke, the

Monzonite, and the Syenite. These results are in line with and support historic drilling within the resource

model shell.

Figure 1: Didipio resource model looking east with 2023 drilling YTD and existing mine development

Figure 2: Plan View of 2023 drilling YTD at 2090 mRL

Continues on page 4

Didipio Deeps

2023 drilling YTD has extended gold-copper mineralization down to a depth of 1860 mRL, which is

characterised by chalcopyrite-bornite veinlets and disseminations and remains open at depth. Hole

RDUG611 is the deepest hole drilled to date, intersecting several zones of mineralization down hole. The

lower zone of 72m at 3.40 g/t AuEq extends mineralization approximately 100m below the current limit of

the Inferred Resource shell. Holes RDUG609, RDUG610 and RDUG611 all intersected wide zones of

mineralization and will support the conversion of Inferred Resources. Further drilling is underway to better

define these zones (Figure 3).

Figure 3: Didipio Deeps, Monzonite section looking west (30 metre window)

Balut Dyke

2023 drilling YTD of the Balut Dyke below 2200 mRL has returned significant results with similar thickness

and grade to previous intercepts extending mineralization along strike to the west (Figure 4). The geometry

of the dyke in the west is not adequately defined due to acute drill hole intersection angles for RDUG481

and RDUG484. Definition of the Balut Dyke mineralization and geometry will continue as further underground

platforms become available.

Figure 4: Balut Dyke section looking west (30 metre window)

Monzonite & Syenite

A wide zone of gold-copper mineralization is hosted by the Balut Dyke, Monzonite and Syenite at the eastern

extent of mineralization where drilling supports the conversion of Inferred Resources (Figure 5).

Mineralization remains open at depth below 2000 mRL, with the deepest hole (RDUG603) returning the best

intercept of 218m @ 4.6 g/t AuEq. Drilling on a similar section down to 1980 mRL is well advanced with a

targeted completion by the end of Q3 2023.

Figure 5: Monzonite, Syenite, and Balut section looking west (30 metre window)

Eastern Breccia

2023 drilling YTD of the Eastern Breccia was undertaken immediately below the previously reported

intercepts from December 2022 at 2250 mRL level and outside existing Mineral Resources. Three drillholes

intersected significant gold-copper mineralization associated with chalcopyrite and bornite veinlets, and pods

of chalcopyrite-bearing quartz (Figure 6). This target remains open at depth.

Figure 6: Eastern Breccia section looking northwest (40 metre window)

Table 1: 2023 Didipio Resource Definition and Extensional drilling significant intercepts year to date

(intervals are core lengths, not true width). “Definition” drilling includes Conversion drilling and is

within the current resource model shell, while “Extensional” drilling is outside the current resource

model shell. Definition drill results are in line with and support historic drilling within the resource

model shell.

HoleID From To Interval Au g/t Cu % AuEq g/t AuEq gxm Drilling Category

RDUG465 73.0 91.6 18.6 2.56 1.20 4.24 79.30 Definition

RDUG466 70.0 91.0 21.0 0.90 0.54 1.65 34.61 Definition

RDUG467 74.0 104.0 30.0 1.16 0.66 2.08 62.25 Extensional

RDUG469 26.0 57.0 31.0 1.67 0.56 2.45 75.99 Definition

including 26.0 30.0 4.0 3.72 1.51 5.81 23.23 Definition

including 30.0 57.0 27.0 1.37 0.42 1.95 52.76 Definition

RDUG470 38.0 55.0 17.0 1.76 0.44 2.37 40.33 Definition

including 38.0 48.0 10.0 2.37 0.59 3.19 31.85 Definition

including 48.0 57.0 7.0 0.89 0.23 1.21 8.48 Definition

RDUG471 23.0 66.0 43.0 1.26 0.53 2.00 85.88 Definition

including 23.0 37.0 14.0 1.30 0.52 2.02 28.25 Definition

including 37.0 58.0 21.0 1.43 0.62 2.30 48.34 Definition

including 58.0 66.0 8.0 0.73 0.31 1.16 9.29 Definition

RDUG472 31.3 116.0 84.7 1.94 0.53 2.68 226.61 Definition

RDUG473 95.0 179.0 84.0 1.64 0.44 2.26 189.62 Definition

including 95.0 103.0 8.0 3.06 0.77 4.13 33.01 Definition

including 103.0 160.0 57.0 1.79 0.43 2.38 135.80 Definition

including 160.0 179.0 19.0 0.60 0.35 1.09 20.80 Definition

RDUG474 102.0 190.0 88.0 1.50 0.59 2.31 203.50 Definition

RDUG475 69.0 201.0 132.0 1.52 0.56 2.30 302.90 Definition

RDUG476 60.2 76.0 15.8 9.16 1.77 11.62 183.55 Definition

RDUG479 2.0 11.0 9.0 7.95 0.23 8.27 74.42 Extensional

RDUG480 55.0 104.0 49.0 5.87 1.14 7.45 365.26 Definition

RDUG481 59.0 145.5 86.5 4.22 0.81 5.35 462.41 Definition

and 205.8 216.0 10.2 4.07 1.35 5.94 60.61 Extensional

RDUG482 77.0 147.0 70.0 3.78 1.02 5.19 363.46 Definition

and 166.0 189.0 23.0 1.33 0.49 2.00 46.08 Definition

RDUG483 48.6 96.0 47.4 1.96 0.44 2.56 121.47 Definition

including 48.6 60.0 11.4 4.75 0.97 6.10 69.56 Definition

including 60.0 96.0 36.0 1.07 0.27 1.44 51.92 Definition

RDUG484 54.0 110.1 56.1 2.90 0.44 3.51 196.97 Definition

RDUG486 51.8 74.0 22.2 3.22 0.56 4.00 88.70 Definition

including 51.8 58.0 6.2 1.19 0.35 1.67 10.36 Definition

including 58.0 74.0 16.0 4.00 0.64 4.90 78.34 Definition

RDUG487 48.2 64.9 16.7 2.41 0.59 3.23 54.00 Definition

including 48.2 53.0 4.8 1.73 0.51 2.43 11.69 Definition

including 53.0 64.9 11.9 2.69 0.62 3.56 42.31 Definition

RDUG488 69.0 87.0 18.0 2.20 0.31 2.63 47.37 Definition

RDUG490 29.0 61.7 32.7 1.49 0.44 2.10 68.71 Definition

including 29.0 53.0 24.0 1.74 0.56 2.51 60.20 Definition

including 53.0 61.7 8.7 0.79 0.13 0.98 8.51 Definition

RDUG491 34.0 63.0 29.0 1.37 0.49 2.06 59.72 Definition

and 206.6 224.0 17.4 3.87 0.50 4.09 71.13 Extensional

RDUG492 38.0 100.0 62.0 1.07 0.35 1.56 96.51 Definition

and 223.0 234.5 11.5 1.71 0.35 2.20 25.27 Extensional

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