Question 7 of 19: 2.4: Underground Mining Method Selection and VMS Deposit Significance

Question 2.3–2.4: Underground Mining Method Selection and VMS Deposit Significance (10 marks)

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2.3 — Suitable underground mining methods. VMS lenses are typically steeply-dipping to sub-vertical, tabular, and can range from narrow (a few metres) to moderately wide (tens of metres); host-rock competency (particularly of the hanging wall) is a critical selection driver alongside width and dip. For a narrow, steeply-dipping lens with a competent hanging wall, shrinkage stoping or cut-and-fill (mechanized or resuing cut-and-fill for very narrow, high-grade material) are well suited — both control dilution tightly against a narrow orebody and cut-and-fill additionally provides backfill support where selective, grade-sensitive extraction matters. For a wider, steeply-dipping lens with a competent hanging wall and footwall, sublevel open stoping (with or without backfill) is efficient and lower-cost, exploiting the deposit's width to allow large, mechanized, non-entry stopes. Where the hanging wall is weak or unstable (common where the VMS hanging wall is a friable exhalative/chemical sediment rather than competent volcanic rock), open stoping without support is unsafe, so cut-and-fill or, for larger weak-ground deposits, longhole stoping with cemented backfill is preferred to actively support the excavation as ore is extracted rather than relying on the rock mass alone. Steep dip generally favours gravity-assisted methods (shrinkage, sublevel open stoping, VCR) over methods designed for flatter, tabular bodies (room-and-pillar), which are rarely applicable to VMS geometry at all.

2.4 — Importance of VMS deposits to metal supply. VMS deposits are a globally significant source of copper and zinc, and a major source of lead, silver and gold as co-/by-products, because a single VMS orebody typically hosts several of these metals simultaneously in one polymetallic ore, giving VMS mines an economic resilience that single-metal deposits lack (a weak copper price can be partly offset by strong zinc or gold credits, and vice versa). In Canada, VMS camps such as Kidd Creek and the Flin Flon–Snow Lake belt have historically been (and in the latter case remain) major contributors to Canadian copper, zinc, silver and gold production, and have anchored regional smelting/refining infrastructure and mining communities for decades. Internationally, the Iberian Pyrite Belt (Spain/Portugal), the Bathurst camp analogues, and Kuroko-type districts in Japan have historically supplied substantial base-metal tonnage, while modern exploration continues to target VMS systems (including in submarine/seafloor massive sulphide settings) as a source of future copper and zinc supply at a time when global demand for both metals — copper especially, driven by electrification and renewable-energy infrastructure — is rising faster than easily accessible new discoveries are being made, making VMS-style exploration and re-exploration of known camps an ongoing strategic priority for supply security.