CHALLENGE: Is there a word for ?

We have received an inquiry from an individual who is seeking the name of a particular kind of agreement unique to the mining industry.

John Dash at McCarthy Tetrault explained the situation thus: Company "A" owns property that has copper in the first 500 meters below the surface and uranium from 750 to 1,500 metres below the surface. Company "A" is not interested in the copper but wants to mine the uranium. So company "A" wants to sell the copper rights to Company "B" (a copper mining company) but retain the rights to mine the uranium simultaneously. Is there a name for this type of mining agreement?

If the perfect word pops into the mind of a CMJ reader, Dash can be contacted at jdash@mccarthy.ca or 416-601-8075.