Genetic Model for Exploration of Offshore West Coast Ironsands, North Island, New Zealand

A review of previous studies of ironsands on the west coast of the North Island suggests that the titanomagnetite was mostly derived from erosion of the Taranaki andesite volcanoes. GIS modelling suggests that approximately 485 km(3) of volcanic material, containing 39 x 10(9) tonnes of titanomagnetite, has been eroded from these volcanoes. This leaves about 37 x 10(9) tonnes of titanomagnetite eroded from Taranaki not accounted for by known resources in onshore deposits. A much larger quantity is likely if additional sources of titanomagnetite are considered, highlighting the potential for undiscovered resources onshore and offshore. The distribution of ironsand shown by previous offshore bottom sampling, together with interpretation of an aeromagnetic survey in the Patea area, suggests that offshore ironsand resources are present in former beach deposits and river channels formed when sea level was lower than at present (e.g. 9 Ka). Rising sea level, wave action and tidal currents will have modified the original beach and aeolian dune deposits.