CONCEPTS FOR GEOCHEMICAL GOLD EXPLORATION BASED ON THE ABUNDANCE AND DISTRIBUTION OF ULTRAFINE GOLD

Conventionally, geochemical exploration for gold is based on the assum ptions that (1) gold is chemically inert in surficial environments; (2 ) gold occurs mainly in discrete grains; and (3) gold is transferred b y mechanical means to form elastic dispersion halos and dispersion tra ins. Consequently, the commonly adopted methodology has been (i) to de termine gold in heavy mineral concentrates; (2) to use large samples i n order to improve the reproducibility of gold analyses; (3) to use hi gh detection limits and thresholds; and (4) to determine total gold co ntents and pathfinder elements in the samples. However, these methods are not always successful in locating gold deposits, and they have lim ited application in the search for buried or blind deposits. In China, studies of the distribution and migration of particulate and ultrafin e gold indicated that (1) gold is active and mobile in surficial envir onments; (2) gold occurs not only as discrete grains, but also as ultr afine particles and other complex forms; and (3) regional low-concentr ation gold anomalies as well as local anomalies over buried gold depos its originate from ultrafine gold and other complex forms of gold. The methodology developed in China for regional and local geochemical gol d exploration is based on this experience. Results of investigations a round two gold deposits in China are presented.