As I was posting my comments on the mining plan I noticed the detail in open pit areas. Zooming in on this image....
Opasura East in particular.
The "ore" blocks, in Magenta, clearly show discontinuities and stacked lenses. In an open pit situation this is "acceptable". However, in an UG situation it would probably add to the cost of mining where only detailed studies could show if mineralisation had viable economics.
Opasura E pit looks like it goes for the higher strip ratio to get the sweet spots near the adits. Very rough green line.
Opasura West - multiple pits plus scallops but significant continuous UG zones (dark red - Plus "rolls" or folds/and or faults).
Less stripping than at OpE.