Ann: High Grade Copper intersected at Horse Well Prospect, page-428

The traditional model for sedex style requires a breccia pipe that feeds the deposit. The organic material will tend to deposit at the lowest points, so what you look for areas where it could pool close to the pipe. The reducing shale will cause sulphides to precipitate out of hydrothermal fluids. So hence it will be in the shales. These deposits can be thin and extend kilometres but can contain decent grades. Hence they can be hard to find at depth as shales and sands can exhibit similar seismic responses but generally are layered. If grades can be 1% it might economic over 200 metres. Which would be substantial. XRF can unreliable at grades 1% or lower.