jack,
If I recall correctly from an early tour at Lupin, perma-frost extends to depths of about 500 meters. This requires cemented (tailings) backfill in the stopes to prevent them from filling up with ice. The stopes were rather large, about 20 meters wide, I couldn't see the top of them and up to 70 or 80 meters long.
The roof and floor on the "dyke" at Snap lake is paragneiss(hopefully one that will not exfoliate, cave or sluff, layer by layer). The kimberlite is not serpentinized, however the footwall and hangingwall contacts should be narrow, clay rich, serpentinized slips(maybe the kimberlite will break clean with little dilution?)...
I'm not a miner, however, this may help you comment further on the mining method and likely cost.
regards,
teevee |
