Abstract:

Some Gobi desert terrains in northwestern China are peneplains formed by a long period of erosion. Dispersion pattern of elements is changed under this kind of landscape evolution. Jinwozi gold deposit was selected for study of element dispersion and migration in the process of pediplanation by using overburden drilling sampling. The results show that (1) gold tends to concentrate in the top and bottom of the vertical profile over the ore body;  (2) gold is enriched in the finegrained fractions of soils with clayrich horizons at surface or near surface and the largest gold anomalies occur in fine grained samples  (-100 mesh) over the ore body;  (3) gold distribution in different size fractions of soils at the bottom of the weathering regolith display no obvious difference but tend to be anomalously enriched in bedrock troughs. This indicates that gold was concentrated in the lowest places by erosion and lateral transportation during the process of pediplanation. Vertical migration to the soil surface and entrapment by clays and amorphous FeMn oxides leads to the formation of geochemical anomalies directly over the ore body.

Key words: Gobi desert terrain, landscape evolution, pediplanation, Jinwozi gold deposit, geochemical anomaly, lateral dispersion, vertical migration