The Goodall gold mine is located 30 km east of Adelaide River, within
the Pine Creek 1:250 000 map sheet, at 8 525 000 mN: 750 000 mE, on
the AMG grid. The first gold was poured in April 1988 and the mine closed in
September 1993, having produced 228 400 ounces of gold from 4.095
million tons of ore, at a head grade of 1.99 g/t. Oxide and primary ore was
mined from one large open cut and low grade oxide ore from three
smaller pits. The gold mineralisation was discovered in 1981 by means of
a helicopter borne rock chip sampling survey, which delineated 13
discrete anomalies. Systematic grid sampling of rock chips outlined an
area of 1300 m by 300 m within the 2.0 g/t contour. Over 7500 m of
costeaning was used to delineate the A and B-Pod mineralised areas.
Geochemical soil sampling played only a minor role in the discovery and
geophysics none at all. By the end of 1984, 40 diamond drill holes had
been completed and a resource of 3.63 million tonnes at 3.0 g/t
calculated. In January 1985, Western Mining Corporation Ltd became a joint
venture partner and funded exploration to cam a 60 per cent interest.
Additional drilling led to a feasibility study in 1987, based on a Measured
and Indicated resource of 4.25 million tonnes at a grade of 2.35 g/t. The host rocks are quartzo-feldspathic wacke and interbedded phyllitic
siltstone, of the Proterozoic Burrell Creek formation. The main zone of
gold mineralisation, A-Pod, occurs in a sub-vertical vein array, up to 50 m
wide and 800 m in length, of quartz and sulphide veins (5-20 mm wide),
It is parallel to and on the east limb of an upright, north plunging
anticline. Five types of veining have been recognised, with the bulk of the
gold mineralisation associated with quartz-pyrite-arsenopyrite and
chlorite-quartz-pyrite veins. The gold occurs as particles, from 1-20
micron, as inclusions and along fractures in pyrite and arsenopyrite and to
a limited extent in chlorite. The mineralisation is epigenetic and
structurally controlled by fractures developed during an earlier folding
event. The gold is assumed to have been derived from the underlying
sediments of the Koolpin Formation by hydrothermal fluids emanating
from the deep seated northern margin of the Cullen Batholith.
Precipitation of gold may have been controlled by variations in
temperature and pressure.