NI 43-101 Technical Report Haile Gold Mine

Lancaster County, South Carolina

Effective Date: December 31, 2021

Report Date: March 30, 2022

Report Prepared for

OceanaGold Corporation

Report Prepared by

SRK Consulting (U.S.), Inc.

1125 Seventeenth Street, Suite 600 Denver, CO 80202

SRK Project Number: 392900.310

Signed by Qualified Persons:

David Carr, BEng Metallurgical (Hons), MAusIMM (CP) (OceanaGold Chief Metallurgist) Michael Kirby, PE, MEng Civil (OceanaGold Environmental Superintendent)

David Londono, BSC, MEng, MSc Earth and Systems Engineering, MBA, SME-RM (OceanaGold Executive General Manager)

Gregory Hollett, BEng Mining Engineering, P.Eng (EGBC) (OceanaGold Group Mining Engineer) Jonathan Moore, BSc Geology (Hons), MAusIMM (CP) (OceanaGold Chief Geologist)

Brianna Drury, BEng Mining, SME-RM (OceanaGold Underground Project Manager)

Larry Standridge, PE, MSE Geotechnical (Call & Nicholas Principal Engineer, Geotechnical Engineer) Jay Newton Janney-Moore, PE (NewFields Project Manager I)

William Lucas Kingston, P.G. Hydrogeology and Groundwater Management (NewFields Senior Hydrogeologist) Joanna Poeck, BEng Mining, SME-RM, MMSAQP (SRK Principal Consultant, Mining Engineer)

Matt Sullivan, BEng, RM-SME (SRK Principal Consultant, Mineral Economics)

David Bird, MSc., PG, RM-SME (SRK Principal Consultant, Geochemistry) John Tinucci, PhD, PE (SRK Principal Consultant, Geotechnical Engineer) Brian S. Prosser, PE (SRK Principal Consultant)

Reviewed by:

Berkley Tracy, MSc Geology, PG, CPG, PGeo (Principal Consultant, Resource Geologist)

Page ii

Table of Contents

1 Summary ..................................................................................................................... 17

  • 1.1 Property Description and Ownership ................................................................................................ 17

  • 1.2 Geology and Mineralization .............................................................................................................. 17

  • 1.3 Status of Exploration; Development and Operations ........................................................................ 17

  • 1.4 Mineral Processing and Metallurgical Testing .................................................................................. 18

  • 1.5 Mineral Resource Estimate ............................................................................................................... 18

    Open Pit Mineral Resource Estimate .................................................................................... 18

    Underground Mineral Resource Estimate ............................................................................. 19

    Combined Open Pit and Underground Resource Estimate .................................................. 21

  • 1.6 Mineral Reserve Estimate ................................................................................................................. 22

    Open Pit Mineral Reserves Estimate .................................................................................... 22

    Underground Mineral Reserves Estimate ............................................................................. 23

    Combined Open Pit and Underground Reserves Estimate .................................................. 25

  • 1.7 Mining Methods ................................................................................................................................. 25

    Open Pit Mining Methods ...................................................................................................... 25

    Underground Mining Methods ............................................................................................... 28

    Combined OP and UG Production Schedule ........................................................................ 30

  • 1.8 Recovery Methods ............................................................................................................................ 33

  • 1.9 Project Infrastructure ......................................................................................................................... 33

  • 1.10 Environmental Studies and Permitting .............................................................................................. 33

  • 1.11 Capital and Operating Costs ............................................................................................................. 34

  • 1.12 Economic Analysis ............................................................................................................................ 35

  • 1.13 Conclusions and Recommendations ................................................................................................ 36

    Geology and Mineral Resources ........................................................................................... 36

    Status of Exploration; Development and Operations ............................................................ 37

    Mining and Reserves ............................................................................................................. 37

    Mineral Processing and Metallurgical Testing ....................................................................... 38

    Recovery Methods ................................................................................................................ 38

    Project Infrastructure ............................................................................................................. 38

    Environmental Studies and Permitting .................................................................................. 39

    Economic Analysis ................................................................................................................ 39

2 Introduction ................................................................................................................ 40

  • 2.1 Terms of Reference and Purpose of the Report ............................................................................... 40

  • 2.2 Qualifications of Consultants ............................................................................................................ 40

  • 2.3 Details of Inspection .......................................................................................................................... 42

Page iii

  • 2.4 Sources of Information ...................................................................................................................... 43

  • 2.5 Effective Date .................................................................................................................................... 43

  • 2.6 Units of Measure ............................................................................................................................... 43

3 Reliance on Other Experts ........................................................................................ 44

  • 4 Property Description and Location .......................................................................... 45

    • 4.1 Property Location .............................................................................................................................. 45

    • 4.2 Ownership ......................................................................................................................................... 47

  • 5 Accessibility, Climate, Local Resources, Infrastructure and Physiography ........ 49

    • 5.1 Accessibility ....................................................................................................................................... 49

    • 5.2 Climate .............................................................................................................................................. 49

    • 5.3 Local Resources and Infrastructure .................................................................................................. 49

    • 5.4 Physiography .................................................................................................................................... 49

    • 5.5 Infrastructure Availability and Sources .............................................................................................. 49

  • 6 History ......................................................................................................................... 50

  • 7 Geological Setting and Mineralization ..................................................................... 52

    • 7.1 Regional Geology .............................................................................................................................. 52

    • 7.2 Local Geology ................................................................................................................................... 55

    Lithology ................................................................................................................................ 55

    Structure ................................................................................................................................ 62

  • Mineralization and Alteration ................................................................................................. 64

  • 8 Deposit Type .............................................................................................................. 67

    • 8.1 Haile Genetic Model .......................................................................................................................... 67

    • 8.2 Haile Geological Model ..................................................................................................................... 68

  • 9 Exploration ................................................................................................................. 69

    • 9.1 Pre-Romarco ..................................................................................................................................... 69

    • 9.2 Romarco ............................................................................................................................................ 69

    • 9.3 OceanaGold Exploration ................................................................................................................... 69

    Geologic Mapping and Surface Sampling ............................................................................. 69

    Geophysics ............................................................................................................................ 70

  • 10 Drilling ......................................................................................................................... 71

    10.1 Type and Extent ................................................................................................................................ 71

    10.2 Sample Collection ............................................................................................................................. 72

    10.3 Collar Locations and Downhole Surveys .......................................................................................... 73

    10.4 Significant Results and Interpretation ............................................................................................... 73

  • 11 Sample Preparation, Analysis and Security ............................................................ 75

    11.1 Sample Preparation for Analysis ....................................................................................................... 75

Page iv

Off-Site Sample Preparation ................................................................................................. 76

11.2 Sample Analysis ................................................................................................................................ 77

11.3 Check Assays ................................................................................................................................... 79

11.4 Quality Assurance/Quality Control Procedures ................................................................................ 79

Standards .............................................................................................................................. 79

Blanks .................................................................................................................................... 79

Duplicates .............................................................................................................................. 79

Actions and Results ............................................................................................................... 79

11.5 Opinion on Adequacy (Security, Sample Preparation, Analysis) ...................................................... 80

12 Data Verification ......................................................................................................... 81

12.1 Data Validation of Pre-Romarco Holes ............................................................................................. 81

12.2 Verification of Romarco and OceanaGold Data ................................................................................ 81

12.3 Romarco Data Verification ................................................................................................................ 82

12.4 Horseshoe Data Verification 2016 .................................................................................................... 83

12.5 Haile QA/QC ALS July 2017-January 2022 ...................................................................................... 85

July 2017- January 2022 CRM Performance ........................................................................ 85

Contamination Monitoring ..................................................................................................... 89

Statement of Data Adequacy ................................................................................................ 90

13 Mineral Processing and Metallurgical Testing ........................................................ 91

13.1 Testing and Procedures .................................................................................................................... 92

Comminution ......................................................................................................................... 92

Throughput Estimate Assumptions ....................................................................................... 95

Flotation and Cyanidation ...................................................................................................... 95

Sample Representativeness ............................................................................................... 106

13.2 Recovery Estimate Assumptions .................................................................................................... 107

14 Mineral Resource Estimate ..................................................................................... 111

14.1 Open Pit Mineral Resources Estimate ............................................................................................ 111

Drillhole Database ............................................................................................................... 112

Geologic Model Concepts ................................................................................................... 112

Lithology .............................................................................................................................. 112

Silicification .......................................................................................................................... 113

Pyrite ................................................................................................................................... 113

Grade Domain Construction ................................................................................................ 113

Compositing ........................................................................................................................ 114

Assay Cap Values ............................................................................................................... 114

Multiple Indicator Gold Class Thresholds and Means ......................................................... 115

Variogram Analysis and Modeling .................................................................................. 115

Page v

Block Model ..................................................................................................................... 115

Estimation Methodology Gold, Sulfur and Carbon .......................................................... 115

Estimation Methodology Silver ........................................................................................ 116

Bulk Density .................................................................................................................... 117

Resource Classification .................................................................................................. 118

Model Validation ............................................................................................................. 119

Resource Model Reconciliation ...................................................................................... 122

Mineral Resource Statement .......................................................................................... 123

14.2 Underground Mineral Resource Estimate ....................................................................................... 123

Horseshoe Mineral Resource Estimate ............................................................................... 123

Palomino Mineral Resource Estimate ................................................................................. 134

14.3 Open Pit, Stockpile and Underground Combined Mineral Resource Statement ............................ 148

14.4 Relevant Factors ............................................................................................................................. 149

15 Mineral Reserve Estimate ........................................................................................ 150

15.1 Open Pit Mineral Reserve Estimate ................................................................................................ 150

Introduction .......................................................................................................................... 150

Conversion Assumptions, Parameters and Methods .......................................................... 151

Reserve Estimate ................................................................................................................ 153

15.2 Underground Mineral Reserve Estimate ......................................................................................... 154

Introduction .......................................................................................................................... 154

Conversion Assumptions, Parameters and Methods .......................................................... 154

Reserve Estimate ................................................................................................................ 157

15.3 Open Pit and Underground Combined Reserves Statement .......................................................... 157

16 Mining Methods ........................................................................................................ 159

16.1 Open Pit Mining Methods ................................................................................................................ 159

Current or Proposed Mining Methods ................................................................................. 160

Parameters Relevant to Mine or Pit Designs and Plans ..................................................... 160

Optimization ........................................................................................................................ 167

Mine Design ........................................................................................................................ 170

Overburden/Geochemical ................................................................................................... 172

Mine Production Schedule .................................................................................................. 177

Mining Fleet and Requirements .......................................................................................... 184

Labor ................................................................................................................................... 185

Mine Dewatering ................................................................................................................. 186

16.2 Underground Mining Methods ......................................................................................................... 187

Cut-off Grade Calculations .................................................................................................. 188

Geotechnical ....................................................................................................................... 190

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OceanaGold Corporation published this content on 31 March 2022 and is solely responsible for the information contained therein. Distributed by Public, unedited and unaltered, on 31 March 2022 23:28:08 UTC.