mining practicalities : expert opinion sought

The latest ann covers a new New Breccia Pipe with 64m at 2.5% Copper from Surface and Sulphides at Depth.
However the plan area of the Pipe is only 50m x 50m.

Assuming an open cut operation, can anyone suggest to what sort of depth this would be economic. I am assuming that haklage ramps will be outside the orebody and that excavation volumes for this will be considerable and significant realative to the volumes of ore, thus effectively diluting the grade.

Supplementary question is the size of the orebody sufficient to warrant an underground operation at some stage.