[1] Univ Exeter, Environm & Sustainabil Inst, Penryn TR10 9FE, Cornwall, England
[2] Brunel Univ London, Coll Engn Design & Phys Sci, Inst Energy Futures, Uxbridge UB8 3PH, Middx, England
[3] Univ Exeter, Camborne Sch Mines, Penryn TR10 9FE, Cornwall, England
[4] Bur Rech Geol & Minieres BRGM, 3 Ave Claude Guillemin,BP 36009, F-45060 Orleans 2, France
[5] Rhein Westfal TH Aachen, Inst Mineral Resources Engn, Wiillnerstr 2, D-52062 Aachen, Germany