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.
3.1.1 Tectonic setting. Canadian Cordilleran porphyries (e.g. Highland Valley, Gibraltar, Mount Polley, New Afton) form above east-dipping subduction zones along the convergent margin of ancestral terranes (Quesnellia, Stikinia) accreted to the North American craton, where partial melting of the subducting slab/mantle wedge generates calc-alkaline to alkalic magmatism. Porphyry stocks are emplaced at shallow crustal levels (1–5 km) as the final, volatile-rich apophyses of larger underlying batholiths, typically along major arc-parallel or transverse structural corridors that focus fluid flow.
3.1.2 Host and associated rock types. The mineralizing intrusion itself is typically a porphyritic granodiorite, quartz monzonite or (in Cordilleran alkalic examples like Mount Polley/New Afton) monzonite/syenite, characterized by phenocrysts in a finer-grained groundmass reflecting rapid near-surface cooling. It intrudes and mineralizes a broader "associated" package of comagmatic volcanic and volcaniclastic wall rocks (andesitic to dacitic flows/tuffs) and older basement, with mineralization commonly straddling the intrusion/wall-rock contact rather than being confined strictly to the stock.
3.1.3 Alteration mineralogy. Alteration is classically zoned outward from the intrusive core: a potassic core (secondary biotite ± K-feldspar, hosting the bulk of the Cu–Mo stockwork veining); an overlying/lateral phyllic zone (quartz–sericite–pyrite, "QSP"); an argillic zone (clay minerals ± residual quartz, often weakly mineralized, sometimes host to a later high-sulphidation overprint); and a distal, weakly mineralized propylitic halo (chlorite–epidote–calcite–pyrite) that can extend hundreds of metres to kilometres beyond the ore zone and is a key vectoring tool in exploration.
3.1.4 Associated economic minerals. Chalcopyrite (±bornite in higher-grade potassic cores) is the principal copper sulphide; molybdenite is a common by-product concentrated in the potassic-to-phyllic transition (often as a separate, later stockwork generation); pyrite is ubiquitous, especially in the phyllic zone; native gold/electrum and Ag-bearing sulphosalts occur in the Cu-Au-enriched sub-type (e.g. New Afton, Mount Polley) associated with the potassic zone. Supergene enrichment (chalcocite blankets) can locally upgrade near-surface grades where post-mineral weathering and oxidation have occurred.
