They used the same cut-off grade as Excelsior's Gunnison project which uses a similar extraction process. Copper is more easily removed from the oxides than the sulphides.

http://www.excelsiormining.com/images/Presentations/min_ppt.pdf

It's unlikely the market will add value for Van Dyke until the following statement from the press release is answered:

The Base Case results of the resource estimate and the recent results from the In-Situ Pressure Leach tests will be used to determine if completion of a Preliminary Economic Assessment ("PEA") of the project is warranted.