Distribution and dispersion of gold in glacial till associated with gold mineralization in the Canadian shield

Supergene dispersion of gold at Akatasa prospect, Xinjiang, China

“…This interpretation also requires that the dispersed gold is inherited from the bedrock. If the dispersed gold were the result of supergene redistribution of gold, either mechanically as very fine particles or chemically, the gold should be more abundant in the finer fractions of the soils, as is commonly the case in more humid climates (Shelp and Nichol, 1987).…”

Regional and local-scale gold grain and till geochemical signatures of lode Au deposits in the western Abitibi Greenstone Belt, central Canada

“…They are analysed for Au and other elements by non-destructive instrumental neutron activation analysis (INAA) (Hoffman et al 1999). For unoxidized till, a small representative split of the (Bajc 1996) anomalous: large number of small gold grains, low gold concentration not anomalous: two very large gold grains, high concentration of gold anomalous: large number of small gold grains, high concentration of gold , 1997Matachewan Bajc et al 19963 Matheson McClenaghan 1990, 1992bNichol et al, HMC may also be analysed for base metals and other elements by aqua regia/inductively coupled plasma-emission spectrometry (ICP-ES). Destructive analytical methods for the HMC, such as fire assay, are not commonly used so that concentrates may be examined later for Au grains, kimberlite indicator minerals or other indicator minerals.…”

Automated Gold Grain Counting. Part 1: Why Counts Matter!

“…Since then, it has been extensively used in glaciated terrain by the exploration industry, and "Drift prospecting" has become the method of choice for grassroots gold exploration in North America and northern Eurasia. However, the method implanted in the 1970's [1,2,3,4], which is heavily dependent on operator's skills and poorly parameterized, barely evolved. The precepts of the method are that gold can efficiently be concentrated with gravimetric method and that gold grains can be easily identified, both of which we here challenge.…”

“…The method used to process glacial sediments in almost all laboratories, hereafter referred as the "conventional method", is based on a combination of gravity separation techniques (mainly shaking tables and hand panning) and visual identification (typically under binocular stereomicroscopes). Although such method is widely used and lead to numerous successes, e.g., [2, 6 ,7, 20-28], some studies also suggest that the conventional method yields erratic results due to low counts and is not effective in recovering/identifying very small gold grains [3,4,[29][30][31][32][33]. In facts, most laboratories report only an uncertified visual grain count, with grain size estimation and simple shape interpretation [34].…”

“…Given that the cumulative proportion of gold grains sharply increases as grain size decreases in unconsolidated sediments [35], the loss of small grains by the conventional method may generate skewed data. Shelp and Nichol [3] have suggested that the conventional method fails to recover 85% to 96% of the gold grains within heavy mineral concentrates from tills of the Canadian Shield.…”