Otago survey shows complex schist geology structure

Mr Doyle said that 50,000 line km of electromagnetic and gradient magnetometer was flown and the images processed from the data collected indicate considerably more variation and structural complexity in the Otago schist than has been previously mapped and interpreted.

Mr Doyle said that the new data showed there were sets of narrow, strong northwest-southeast trending magnetic features that currently have no explanation.

Due to complex erosional history, most of the Otago goldfield is contaminated with transported gold which limits the effectiveness of gold geochemistry to detect covered basement gold-arsenic-tungsten mineralisation Mr Doyle said.

Before it began on the recent survey Glass Earth had reprocessed the 180 sq km helicopter electromagnetic survey completed by Oceana Gold in 1996 over the Hyde Macraes shear zone where the Macraes gold mine is sited. The reprocessed resistivity image revealed a zone of increased resistivity in the area between the shear zone’s footwall fault and hanging wall fault where the Macraes gold resources were found.

Based on this evidence Glass Earth had determined that a helicopter electromagnetic survey (HEM) was capable of mapping other geological structures such as the Hyde Macraes shear zone.

The Otago Regional Council, which was keen to encourage collection of regional datasets in the mineral resources area, became a joint venture partner with Glass Earth in carrying out the HEM survey and contributed $1m to the cost.

Mr Doyle said Glass Earth also formed joint venture agreements with three other exploration companies holding a significant permit position in the Otago region, Aurora Minerals Ltd, Australasia Gold Ltd and New Zealand Minerals Ltd.

OceanaGold (NZ) Ltd also entered into a data sharing agreement with Glass Earth.

Source: Glass Earth