Sample support size and spacing determination for resource development of a marine placer gold deposit
P Saravanakumar†Z, GJ Brown, G van Eck
Successful resource development for a marine placer gold deposit
requires continuous sampling throughout the life of mine. The cost of
sampling marine placer gold deposits is exponentially more expensive
than for terrestrial placer and non-placer gold deposits and thus
warrants a comprehensive cost-effective sampling strategy. The
optimum sample support size depends on expected gold grade,
desired confidence limit, and shape and size of the gold grains. The
optimum sample spacing depends on the continuity of the deposit,
required confidence limit, and cost-benefit analysis of a sampling
programme. The current study combines sample support size and
spacing determination for resource development of a marine placer
gold deposit. The study used two methods to calculate the sample
support size – modified Gy’s formula and the approach pioneered by
Clifton et al. (1969). Using historical drillhole data, a geostatistical
simulation of a representative geological/mineralization domain was
created on an extremely dense grid. The simulation realizations were
validated using statistical, spatial, and graphical methods. Additional
sample support sizes were then created by combining adjacent
simulation nodes to form double, quadruple, and octuplet multiples of
drill diameter sizes. The simulations were sampled at three different
spacings: 100 m x 100 m; 50 m x 50 m; and 25 m x 25 m and then
each sample set estimated into 50 m x 50 m blocks with ordinary
kriging. A comparison between the actual and estimated block results
was then carried out and the confidence of each sampling pattern
(sample spacing and sample support size) determined. A cost-benefit
analysis was then used to determine the optimum sampling strategy
for the marine placer gold deposit.
Keywords: sampling, support size, spacing, marine placer gold.