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.
6.1.1.a Tectonic setting. Epithermal deposits form in the uppermost 1–1.5 km of subaerial volcanic edifices along convergent-margin volcanic arcs (the Pacific Rim "Ring of Fire," and analogous Eocene volcanic belts in the interior/Rocky Mountain corridor of BC), commonly localized by CALDERA collapse structures and their associated ring-fracture systems, which provide both the heat source (shallow magma chamber) and the high-permeability structural pathways hydrothermal fluids exploit.
6.1.1.b Action of water. Meteoric water descends, is heated by the underlying magmatic heat source, and rises convectively; where it approaches the water table it commonly reaches boiling, flashing a fraction to STEAM – this boiling is the single most important ore-depositing mechanism in low-sulphidation systems (CO2/H2S loss to the vapour phase destabilizes gold-bisulphide complexes, precipitating gold). Above the water table, rising steam condenses into acidic, oxygenated near-surface groundwater that produces a separate, steam-heated advanced-argillic alteration cap, distinct from the boiling-level ore zone below.
6.1.1.c Alteration mineralogy. LOW-sulphidation systems show adularia–sericite–(illite) alteration flanking banded, colloform/crustiform quartz–calcite±adularia veins, grading outward to propylitic. HIGH-sulphidation systems (magmatic-fluid-dominated, more acidic) instead show advanced-argillic alteration (alunite–kaolinite–pyrophyllite–vuggy silica) directly hosting disseminated/massive sulphide ore. The steam-heated cap common to both styles is itself advanced-argillic (near-surface acid-sulphate alteration) but is typically barren – a common exploration trap when mistaken for the ore-grade advanced-argillic zone of a genuine high-sulphidation system.
6.1.1.d Associated economic minerals. Native gold and electrum, argentite/acanthite and silver sulphosalts (low-sulphidation, Au:Ag variable but often Ag-rich); enargite, luzonite, covellite and other Cu-As-S sulphides accompanying gold in high-sulphidation systems; base-metal sulphides (sphalerite, galena, chalcopyrite) occur peripherally in both styles at depth/lateral distance from the main gold zone.
