Very little public domain information is available on the exploration
signature of the Coronation Hill Au+Pd+Pt deposit. From 1987 to 1990
the BMR (now AGSO) carried out geological, geophysical and
geochemical (whole-rock, stream, soil and rock chip) surveys within the
South Alligator and Kakadu Conservation Zones and defined several key
parameters useful for exploration programs. The essential geological
ingredients for the style of Coronation Hill Au+Pd+PtU deposit are
oxidised, low pH fluids, dilatant fault structures, a thick neutral to
oxidised cover sequence and chemical traps in the basement. In
geophysical data, the areas surrounding the mineralisation can be detected
by airborne magnetics as major lows in magnetite-rich rocks, whereas in
airborne gamma-ray spectrometry data, imaged spectrometric channel
ratios such as U2/I'h and U2/K highlighted alteration surrounding the
deposits. Three types of stream-sediment and soil samples were taken
from each site: (1) -1 mm mesh, 5 kg sample for bulk cyanide leach
(BCL) analysis for Au, Pd, and Pt; (2) 1 kg sample of -1 mm mesh
sediment for fire assay/ICPMS analysis for Au, Pt and Pd; and
(3) 50 g - 180 mesh sample for a variety of trace element analyses,
including Au, Pd and Pt. Techniques 2 and 3 gave similar results for Au,
Pt and Pd, while the recovery rates for Pd and Pt from the BCL samples
were considerably lower. Other trace elements did not define unique
indicators for Pt or Pd mineralisation, as each sample reflected the
dominant lithology in the drainage basin. Rock chip surveys were useful
in determining which faults were associated with the ore fluid in regions
of multiple fracturing. Results from these exploration-style surveys also
confirmed that the Coronation Hill deposit is a variant of the
unconformity-style of mineralisation, as all significant geochemical
and/or geophysical results occur at or below the unconformity.