24-MMP-A4 Mine Valuation and Mineral Resource Estimation · Undated paper
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, undated sitting. 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 (parts 1.1–1.5); candidates then select THREE of the five optional Questions 2–6 (20 marks each) to complete the paper.
Reference texts: Isaaks & Srivastava, An Introduction to Applied Geostatistics (variogram modelling, anisotropy, volume–variance relations); Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (mine scheduling, NPV/valuation methods, stripping-ratio economics); Gentry & O'Neil, Mine Investment Analysis (Canadian mining taxation, CCA classes, smelter/refining contract terms, net smelter return); SME Mining Engineering Handbook, 3rd ed. (mineral exploration/evaluation stages, ore reserve classification); Guilbert & Park, The Geology of Ore Deposits (volcanogenic massive sulphide genesis); 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.
2.1.1 — Formation. VMS deposits form on or near the sea floor at submarine hydrothermal vent systems, typically associated with active volcanic/sub-volcanic centres at mid-ocean ridges, back-arc basins or island-arc settings. Convecting seawater is drawn down through the volcanic pile along fractures, heated by an underlying magma chamber, and leaches metals (Cu, Zn, Pb, Au, Ag) from the surrounding volcanic and volcaniclastic rocks; the hot, metal-charged, reduced hydrothermal fluid then rises buoyantly back to the sea floor and discharges through vents ("black smokers"), where it mixes with cold, oxygenated seawater. This abrupt cooling and mixing causes rapid, near-instantaneous precipitation of sulphide minerals, which accumulate as a stratiform lens or mound directly on the sea floor (the massive sulphide "cap") with a discordant, pipe-like zone of disseminated/stringer sulphide-filled fractures beneath it (the feeder/stringer zone) marking the fluid's upflow conduit.
2.1.2 — Host rocks. VMS deposits are hosted in submarine volcanic and volcaniclastic sequences: felsic to intermediate volcanic rocks (rhyolite, dacite, andesite flows and their pyroclastic equivalents) are the classic and most common host, often directly overlain or interbedded with volcaniclastic sediments and, less commonly, mafic volcanics (basalt) in ophiolite-hosted (Cyprus-type) deposits. The immediate footwall beneath the stringer zone is typically the same felsic volcanic pile the fluids passed through, while the hanging wall above the massive sulphide lens is commonly a chemical or exhalative sedimentary unit (chert, tuffaceous sediment, or "exhalite") marking the cessation of hydrothermal venting and the return to normal sedimentation.
2.1.3 — Economic minerals. The dominant economic sulphides are chalcopyrite (Cu), sphalerite (Zn) and galena (Pb), typically within a gangue-forming matrix of pyrite and/or pyrrhotite (which host little direct value themselves but are the bulk mineral of the massive sulphide lens); precious metals gold and silver are frequently significant by-product or co-product credits, particularly enriched in the upper, more oxidized/precious-metal-rich part of some deposits.
2.1.4 — Examples. Kidd Creek (Timmins, Ontario, Canada) — a very large, high-grade Cu-Zn-Ag VMS deposit; Flin Flon–Snow Lake camp (Manitoba/Saskatchewan, Canada) — a classic Archean/Proterozoic VMS district; internationally, Kuroko-type deposits of Japan and the Cyprus-type ophiolite deposits of the Troodos massif are the type localities the VMS classification itself is named after.
2.2 — Three interpretations of the same drilling. Given identical drill data at a geologic feature, three defensible-but-different orebody outlines can be drawn, and the choice between them is a professional and economic judgment call, not a purely geometric one.
2.2.1 — Conservative outline. A conservative interpretation connects mineralization strictly between adjacent drill intersections only where continuity is directly supported by the data, using tight, close-to-linear tie-lines and excluding any speculative extrapolation beyond the last hole. This minimizes the risk of overstating tonnage/grade and protects the corporation from the downside of building a mine (or committing capital) on ore that turns out not to be there, at the cost of potentially leaving economic, real mineralization outside the model (understating true value) and requiring more infill drilling before the deposit can be confidently expanded.
2.2.2 — Optimistic outline. An overly optimistic interpretation extrapolates mineralization aggressively beyond the drilled intersections, smoothing across gaps and projecting continuity into undrilled ground on the assumption the geological feature persists uniformly. This serves an on-site management or promotional desire to show the largest possible resource and justify moving straight to construction, but it materially understates estimation risk — the extrapolated tonnage carries far lower actual geological confidence than the outline visually implies, and a mine built on this interpretation risks encountering far less ore than planned once mining exposes the true, more limited extent of the structure.
2.2.3 — Realistic ("best interpretation") outline. A realistic interpretation sits between the two extremes: it honours the actual drill intersections, applies a geologically-reasoned (not purely mechanical) continuity model based on the known style of mineralization (e.g. the fold/lens geometry typical of VMS ore), and extrapolates only as far as the geological model and reasonable sample spacing support — explicitly separating the higher-confidence "measured/indicated" core of the interpretation from a lower-confidence "inferred" fringe rather than drawing one uniform outline. This is the professionally defensible approach a Qualified Person under NI 43-101 is expected to produce, and it is the outline that should actually drive resource classification and mine planning, since it neither needlessly discards real ore (as the conservative case risks) nor commits capital against unsupported continuity (as the optimistic case risks).
