Abstract

Neutron activation analysis with subsequent radiochemical separation was used to determine gold and platinum in 65 low-temperature ash samples of western Kentucky No. 9 coal. Twenty-three additional elements were determined at an earlier stage for the corresponding whole coal sample of each low-temperature ash. In the whole coal samples, gold ranges from a high of 1.8 ppb to a sub-ppb level and platinum ranges from a high of 210 ppb to a low of a few ppb. Comparison of mean values for all samples to crustal abundances indicates gold is depleted by a factor of 125 and platinum is enriched by a factor of 18. The correlation matrix between these two metals, low-temperature ash, and the 23 other elements was calculated. The strong correlation between gold and bromine, potassium, and sodium hints that a significant quantity of gold might have been introduced as halogen complexes. Gallium was reported to occur in coal macerals as colloidal inorganic compounds. The strong correlation between platinum and iron and low-temperature ash suggest that platinum may be absorbed and retained as similar colloidal inorganic compounds. The inverse correlation between gold and platinum implies a possible replacement relationship or, alternatively, the inorganic affinity of gold and the apparent organic affinity of platinum. Higher platinum contents tend to relate to sampling sites with a higher K/Na ratio which are located in the lower or tributary element of the delta in Pennsylvanian time.

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