24-MMP-A1 General Geology and Exploration · December 2015
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Mining and Mineral Processing Engineering, 09-Mmp-A1 General Geology and Exploration, 2015-Dec. Closed book; only a Casio or Sharp approved calculator permitted. Questions 1–4 are compulsory; a candidate then completes ONE more question chosen from Questions 5, 6 or 7.
Reference texts: Guilbert & Park, The Geology of Ore Deposits (genetic classification, deposit-type descriptions throughout); Evans, Ore Geology and Industrial Minerals, 3rd ed. (deposit classification, ore-body morphology); Klein & Dutrow, Manual of Mineral Science, 23rd ed. (crystal systems, diagnostic physical properties, hand-specimen identification); Telford, Geldart & Sheriff, Applied Geophysics, 2nd ed. (gravity, magnetic, electrical, EM and radiometric methods); Kearey, Brooks & Hill, An Introduction to Geophysical Exploration, 3rd ed. (survey design and method selection); Rose, Hawkes & Webb, Geochemistry in Mineral Exploration, 2nd ed. (stream-sediment/soil survey design); Peters, Exploration and Mining Geology, 2nd ed. (sampling methods, drilling programs).
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.
A successful surficial geochemical survey in glaciated Canadian Shield terrain follows a deliberate sequence of design decisions:
| Step | Description |
|---|---|
| 1. Sample medium selection | Choose stream sediment (for broad regional reconnaissance), soil/humus (for follow-up over specific targets), or basal till (in Shield terrain, since glacial transport can offset the geochemical anomaly down-ice from the bedrock source, so till sampling must account for ice-flow direction). |
| 2. Sample density/spacing | Set stream-sediment sample density from drainage-basin area (one sample per basin at reconnaissance scale, tightening on follow-up); set soil/till grid spacing from the expected target size and dispersion-train length. |
| 3. Sample preparation | Sieve to a consistent fine fraction (commonly −80 mesh) to concentrate the clay/fine fraction that best adsorbs mobile Au and pathfinder elements, and dry/homogenize consistently to avoid a preparation-induced analytical bias. |
| 4. Analytical method | Fire assay with an AA or ICP-MS finish for gold (needed for the low ppb detection limits gold exploration requires), with a multi-element ICP-MS package for pathfinder elements (As, Sb, Bi, Te, W). |
| 5. QA/QC program | Insert field duplicates, certified reference standards and blanks at a fixed frequency to monitor sampling and analytical precision/accuracy before any anomaly is interpreted. |
| 6. Background/threshold determination | Establish the local geochemical background and statistical threshold (e.g. mean + 2 standard deviations, or a probability-plot break) separately for each distinct lithological/overburden domain, since background varies with rock type and glacial history. |
| 7. Data compilation and follow-up | Compile results in a GIS with drainage-basin/glacial-flow overlays, rank anomalies, and design a tighter follow-up (soil grid, then trenching/drilling) over the highest-priority anomalies. |
| Technique | Usefulness |
|---|---|
| (i) Airborne and satellite techniques | Provide rapid, cost-effective REGIONAL coverage before committing to expensive ground work: airborne magnetic/EM/radiometric surveys map structure, lithological contacts, alteration and conductive sulphide zones, while satellite multispectral/hyperspectral imagery maps surface lithology, hydrothermal alteration minerals and structural lineaments over large, often inaccessible areas. |
| (ii) Fluid inclusions | Microscopic droplets of the original ore-forming fluid trapped within growing crystals; microthermometry (homogenization temperature, freezing-point depression) recovers the temperature and salinity of the ore fluid, which helps establish the deposit's genetic model and can vector exploration toward the hotter, higher-salinity fluid pathway associated with higher-grade mineralization. |
| (iii) Radioisotopes | Radiometric age dating (U-Pb on zircon/monazite, Re-Os on molybdenite/sulphide, ⁶⁵Ar/₃₉Ar on alteration mica) establishes the absolute timing of mineralization relative to host-rock crystallization and regional tectonic events, which both tests genetic models and focuses exploration on rock packages/structures of the favourable age; naturally occurring radon or helium soil-gas anomalies can also directly locate buried faults or uranium mineralization. |
| (iv) X-ray fluorescence (XRF) | Portable handheld XRF units give rapid, non-destructive, quantitative elemental analysis in the field (or on drill core/chips in camp), so pathfinder-element geochemistry can be read essentially in real time, letting a geologist prioritize drill targets and adjust a program's direction without waiting weeks for laboratory assay turnaround. |
| (v) Lasers | Airborne LiDAR strips away vegetation canopy to reveal high-resolution bare-earth topography, exposing subtle fault scarps, fracture patterns and structural lineaments invisible on the ground or in optical imagery, particularly valuable in heavily forested Canadian Shield terrain; laser ablation ICP-MS performs micro-scale, spatially resolved trace-element and isotopic analysis of individual mineral grains, useful for provenance studies and detailed geochronology. |
