Analysis of gold placer data throughout the world suggests that gold grades and volumes cannot be used to distinguish between most types of gold placers. Only the alluvial plain and fan placers are significantly different among the types of gold placers considered. Gold grades and volumes change when working placers go from small-volume methods to large-volume methods. The odds that a placer will be dominantly worked using small-volume methods at the surface are about 5:3. Once small-volume mining has occurred, the odds against subsequent large-volume mining are about 4:1. If a deposit is suitable for large-volume mining and the amount of gold produced from small-volume mining was reported, an estimate of the remaining gold (log//1//0kg) can be made using an equation.
Additional publication details
CHANGES IN GRADE, VOLUME AND CONTAINED GOLD DURING THE MINING LIFE-CYCLE OF GOLD PLACER DEPOSITS.