Special Prospecting Licence (SPL) 1451 covers 3,028 ha and is located in the southern part of Fiji on Ono Island (“Ono”), the eastern most island of the Kadavu Group (Figure 1). High-sulphidation epithermal gold-silver mineralisation is the primary target based on interpretation of results recorded by previous explorers in the area, who reported anomalous stream sediment geochemistry and mapped surface exposures of hydrothermal rock alteration and silicification. Although not outcropping, the gold mineralisation is expected to lie at depth below two zones anomalous in gold, copper, mercury, antimony, molybdenum and arsenic soil geochemistry.
In October 2016 an offset pole-dipole IP survey was successfully completed on two adjacent high sulphidation epithermal gold prospects on the northern part of Ono Island, known as Naqara East and Naqara West. These had previously been covered by soil sampling in 2013 and geological mapping campaigns in 2014 that identified areas of intense argillic alteration and zones of silicification and anomalous geochemistry, proximal to the northern rim of a volcanic caldera (Figure 2).
The offset pole-dipole IP survey involved four arrays, two over each prospect (Figure 2). Transmitter electrodes were placed along a central cut line at 100m intervals with three to four additional electrodes at the end of each receiver line for totals of between 31 and 32 points per array (gold coloured lines on Figure 2). Receiver electrodes were placed at 100m intervals along the two survey lines either side of the transmitter line (34 points). Two 32 channel IP receivers were used to take 3 to 4 readings at each electrode. Figures 3 & 4 are compilations of surface alteration and the processed IP data for the East and West Naqara prospects.
The two arrays on the eastern Naqara prospect produced coherent data showing a NNW trending linear resistivity anomaly that was evident nearer surface and coincident with a distinct chargeability anomaly at increasing depth. The relationship between resistivity and chargeability is poor near surface at Naqara West, but there are indications of increasing chargeability with depth, although the response is not as persistent nor as strong as at the Naqara East prospect. In part this may be due to the chargeability response (particularly at the Naqara West prospect) being impacted by the proximity and incursion of seawater and the rugged and more deeply incised terrain in the west. This contributed to “low earth resistivities” particularly for deeper readings (below 300m to 400m).
A five-hole diamond drilling program is being planned, with two holes in Naqara West and three proposed at Naqara East. These holes are designated A, B, C, D and E on Figures 2, 3 and 4.
The offset pole-dipole survey has been successful in assisting with location of an initial exploration drilling program on Ono Island, one of the few remaining untested epithermal targets along the so-called “Rim of Fire” in the South West Pacific. The schematic model in Figure 7 shows how the hydrothermal alteration, anomalous geochemistry, present land surface and IP data may indicate the presence of gold-silver bearing sulphide mineralisation in this environment.