A Ngapuhi leader says the Government will have a fight on its hand if it tries to open more land in Northland to mining without Maori consent.
Cabinet has approved funding for an aerial magnetic survey of the north, to evaluate the region's mineral resources.
Ngapuhi runanga chair Sonny Tau says the issue of who owns the minerals is part of a sovereignty claim by the tribe which is now before the Waitangi Tribunal.
Mr Tau says the Crown can claim ownership, but Ngapuhi never ceded authority over their lands or what lies beneath them.
GNS Science - the Government research agency that will conduct the magnetic survey - says countries like Australia have mapped their entire landmass in this way and gained thriving industries as a result.
GNS says the surveys of Northland and the West Coast will also yield useful information for seismologists, councils and road builders.