24-MMP-A4 Mine Valuation and Mineral Resource Estimation · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Mining and Mineral Processing Engineering, 09-Mmp-A4 Mine Valuation and Mineral Resource Estimation, 2016-May. 3 hours duration; one handwritten 8.5×11 in reference sheet permitted (not an open-book exam); only approved Sharp or Casio calculators allowed. Question 1 is compulsory (40 marks, parts 1.1–1.6); candidates then select THREE of the six optional Questions 2–7 (20 marks each) to complete the paper.
Reference texts: Isaaks & Srivastava, An Introduction to Applied Geostatistics (variogram modelling, kriging estimators, volume–variance relations); Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (mine valuation, NPV and cut-off grade methodology, mineable reserves); Gentry & O'Neil, Mine Investment Analysis (Canadian mining taxation, inflation and financing effects on DCF yield, smelter/refining contract terms, net smelter return); SME Mining Engineering Handbook, 3rd ed. (mineral exploration/evaluation stages, ore reserve classification, ore deposit models); CIM Best Practice Guidelines and NI 43-101 (Canadian Securities Administrators).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
7.1) Volcanogenic massive sulphide (VMS). Forms at or near the seafloor above submarine felsic-to-mafic volcanic centres, where convecting seawater is heated, leaches metals from the volcanic pile, and exhales as metal-laden hydrothermal fluid through black-smoker-type vents; rapid quenching in cold seawater precipitates stratiform to lenticular massive sulphide bodies (pyrite-sphalerite-chalcopyrite-galena ± barite), typically underlain by a discordant, stringer/stockwork feeder zone. Canadian examples: Bathurst Camp (NB), Kidd Creek and Flin Flon–Snow Lake (Zn-Cu-Ag-Au). Because bodies are steeply dipping, lenticular and often high-grade, UNDERGROUND mining (cut-and-fill, longhole open stoping, sublevel caving depending on width/dip) is typical; unit mining costs are moderate-to-high relative to bulk-tonnage porphyries, offset by higher polymetallic grade.
7.2) Besshi type. A distinct VMS sub-type hosted in dominantly MAFIC volcanic and volcaniclastic/turbiditic sedimentary sequences (rather than the felsic-dominated Kuroko-type setting of 7.1), typically Cu-Zn dominant with comparatively little Pb, formed in a back-arc or rifted-margin marine basin where basaltic volcanism and clastic sedimentation interfinger; ore bodies tend toward thinner, more sheet-like stratiform lenses than classic Kuroko VMS. Canadian/regional example: Windy Craggy (northwestern BC, undeveloped, a large historic Besshi-type Cu resource). Mining method and cost profile mirror general VMS (underground, moderate-to-high unit cost) given similar steeply-dipping, tabular geometry.
7.3) Evaporites (Permian-basin type). Chemical sedimentary deposits precipitated by progressive evaporative concentration of seawater/brine in a restricted, poorly circulated marine or marginal-marine basin, producing a predictable mineral sequence outward/upward as brine concentrates – carbonate, then gypsum/anhydrite, then halite, then the most-soluble potash salts (sylvite, carnallite) last and uppermost. The classic Permian-basin examples (US Permian Basin potash) are matched in Canada by the Devonian Prairie Evaporite Formation of Saskatchewan, host to one of the world's largest potash resources. Mining is either CONVENTIONAL underground (room-and-pillar, continuous miners) at moderate depth, or SOLUTION mining (injection/dissolution wells) for deeper or lower-grade zones; unit value is low (a bulk fertilizer commodity) but tonnage and deposit continuity are enormous, giving very low per-tonne operating cost relative to metallic ores.
7.4) Sedimentary exhalative (SEDEX). Stratiform Pb-Zn-Ag deposits formed by basinal brine, heated at depth and driven upward along syn-sedimentary rift faults, venting onto the seafloor within a deep, anoxic, fine-grained clastic (shale-dominated) marine basin – distinguished from VMS by its sedimentary (not volcanic) host and by typically much larger areal extent and lower average grade. Canadian examples: Sullivan (BC, historic, one of the world's largest Pb-Zn-Ag SEDEX deposits) and Howard's Pass (Yukon/NWT). Given large lateral extent and typically flatter-lying to moderately dipping geometry, SEDEX deposits can be mined by OPEN PIT where depth permits, or by underground bulk methods (room-and-pillar, sublevel stoping) at depth; operating cost is comparatively low per tonne given the bulk-mineable geometry, though remote northern locations (e.g. Howard's Pass) add substantial logistics cost.
7.5) Sudbury Igneous Complex (SIC). Genetically unique among this list – NOT a sedimentary-exhalative or purely magmatic-arc deposit, but the differentiated melt sheet of a ≈1.85 Ga METEORITE IMPACT structure (the Sudbury astrobleme), whose impact-generated mafic-ultramafic melt sheet underwent sulphide-silicate liquid immiscibility, settling dense Ni-Cu-PGE sulphide melt to the base of the complex and into footwall-fault-hosted and "offset dike" (radial breccia dike) deposits beyond the main complex margin. Economic minerals: pentlandite (Ni), chalcopyrite (Cu), with platinum-group element (Pt, Pd) by-product credits. The Sudbury camp (Ontario – Vale, Glencore operations) remains the world's premier Ni-Cu-PGE mining district; deposits are mined UNDERGROUND (mechanized cut-and-fill, longhole stoping) given steep dip and depth, at moderate-to-high unit cost offset by strong polymetallic (Ni+Cu+PGE) by-product credits.
