“Reasonable prospects” in mineral resource estimation and reporting

ABSTRACTABSTRACT A fundamental component of the Definition Standards for Mineral Resources is the requirement that the material have "reasonable prospects for eventual economic extraction" (RPEEE). The first adoption of the RPEEE requirement by a widespread group was in 1997 as part of the Denver Accord meeting and has since become an international standard. Mineral resource statements are prepared for mineral properties that are at various stages in the mining cycle, from the discovery stage through to the production stage. The confidence level of information available for the development of the input parameters for the technical and economic components of RPEEE varies greatly among stages. Consequently, the RPEEE assumptions may evolve with the stage of the mineral property as well. The economic aspects of RPEEE are commonly achieved by selecting appropriate input parameters for establishing a cut-off grade. The technical aspects can include consideration of such items as minimum widths, spatial continuity, and the application of appropriate constraining surfaces and volumes. In all cases, the responsibility of ensuring that the mineral resource statements are prepared in accordance with the requirements of the Canadian Institute of Mining, Metallurgy and Petroleum Definition Standards ultimately resides with the qualified person.RÉSUMÉUne composante fondamentale des Normes de définition des ressources minérales est l'exigence selon laquelle la matière doit avoir des « perspectives raisonnables d'extraction rentable à terme » (RPEEE, de l'anglais reasonable prospects for eventual economic extraction). La première adoption de l'exigence RPEEE par un groupe très répandu a eu lieu en 1997 dans le cadre de l'Accord de Denver et est devenue depuis une norme internationale. Les relevés des ressources minérales sont préparés pour les propriétés minérales qui en sont à diverses étapes du cycle minier, de la découverte à la production. Le niveau de confiance de l'information disponible pour l'élaboration des paramètres d'entrée pour les composantes techniques et économiques de RPEEE varie considérablement entre les étapes. Par conséquent, les hypothèses de RPEEE peuvent évoluer avec l'étape de la propriété minérale ausse. Les aspects économiques des RPEEE sont généralement obtenus en sélectionnant les paramètres d'entrée appropriés pour établir la teneur de coupure. Les aspects techniques peuvent inclure la prise en compte d'éléments tels que les largeurs minimales, la continuité spatiale et l'application de surfaces et de volumes contraignants appropriés. Dans tous les cas, il incombe à la personne qualifiée de veiller à ce que les énoncés sur les ressources minérales soient préparés conformément aux exigences des Normes de définitions de l'Institut canadien des mines, de la métallurgie et du pétrole.KEYWORDS: Cut-off gradeDefinition standardsMineral resourcesMinimum widthsOpen pit surfacesPotentially mineable shapesReasonable prospectsSpatial continuityMOTS-CLÉS: continuité spatialeformes potentiellement exploitableslargeurs minimalesnormes de définitionsperspectives raisonnablesressources minéralessurfaces à ciel ouvert teneur de coupure ACKNOWLEDGMENTSThe authors wish to thank Marilen Miguel and the Professional Geoscientists Ontario for their inspiration to write this paper. We also wish to thank Jason Cox and our colleagues at SLR Consulting (Canada) Ltd., including Natalia Dyatlova, Jeff Sepp, Pierre Landry, John Makin, and Lance Englebrecht for their support and assistance in the preparation of this paper. The authors also wish to gratefully acknowledge the support of Gordon Riddler, Chis Collins, and Victoria Yehl at the British Columbia Securities Commission, Patti Nakai-Lajoie at Endeavour Mining plc, Jon Hill at Jaguar Mining Inc., Jose Javier Santabarbara and Åsa Corin at Mandalay Resources Corporation, and Noris del Bel Belluz at Hummingbird Resources plc for their contributions to this paper. The authors also wish to thank both the internal and external reviewers who graciously provided their time to review this paper, share their experiences, and offer their thoughts and recommendations. Their efforts have greatly improved the paper.REVIEW STATEMENTPaper reviewed and approved for publication by the Geological Society of CIM.DISCLOSURE STATEMENTNo potential conflict of interest was reported by the authors.Additional informationNotes on contributorsR. PressaccoReno Pressacco, MSc(A), PGeo, is an associate principal geologist with SLR Consulting (Canada) Ltd. with more than 36 years' experience in industry, government, and consulting. He is a contributing author to the CIM Mineral Exploration Best Practices Guidelines and the CIM Estimation of Mineral Resources and Mineral Reserves Best Practices Guidelines. In 2020 he received the CIM Robert Elver Mineral Economics Award.L. EvansLuke Evans, MSc, PEng, is a principal geologist with SLR Consulting (Canada) Ltd. He has over 39 years of mineral industry and consulting experience, including over 27 years with SLR, where he currently leads a team of more than 25 resource geologists. He has presented papers and short courses on resource estimation best practices, audits, pitfalls, and other topics.J. PostleJohn Postle, MSc, PEng, is an associate mining engineer (retired) with SLR Consulting (Canada) Ltd. He has more than 50 years' experience in industry and consulting, specializing in mining operations, planning, and management. In 1985, he co-founded Roscoe Postle Associates Inc. (RPA), which was acquired by SLR in 2019. Mr. Postle is a past Chairman of the Mineral Economics Committee of the CIM, was appointed a Distinguished Lecturer of the CIM in 1991, and represented the CIM at the Denver Accord in 1997. He was awarded the CIM Robert Elver Mineral Economics Award in 1997.