THE BEHAVIOUR OF SELENIUM IN GEOLOGICAL PROCESSES

摘要

Selenium contents were analysed from a total of 244 soil samples collected over dif- ferent rock types at a sampling density of one sample per 4 km~2 around Geita gold mining areas, Northwestern Tanzania. Comparisons using literature survey contents of selenium in geological ma- terials and some implications on the selenium in soils are compiled and discussed. Most selenium occurs as simple selenides in small quantities in low temperature hydrothermal deposits devoid of sulphur. It has been observed that to a large extent selenium content is increased more than most trace elements in the upper parts of the Earth perhaps through extraterrestrial deposition.