Geochemical exploration methods for gold in areas with mountain glaciation in Siberia, U.S.S.R.

Abstract

In the mountainous areas of Siberia intensive destruction of ore deposits occurs as a result of Pleistocene mountain glaciation and, as a consequence, element dispersion trains form in the eroded material and in the stream sediments. In these areas, cirques and glaciated valleys are incised as much as 250–600 m into ore deposits. Geochemical anomalies in the stream sediments in the glaciated valleys form as water washes through the till and lacustrine sediments. The surface erosion processes result in the removal of fine gold from talus-covered cirque walls from where it is deposited in channels and lakes. Secondary dispersion halos may either be localized entirely within cirques, or they may be found in the drift within the outwash or glaciolacustrine environments downstream of the cirques. Intermittent accumulations of gold are specifically concentrated in glacially-fed stream sediments in those glaciated valleys characterized by smooth, flat bottoms and abundant lakes: gold in such cases tends to be concentrated in the lake muds. After the lakes have silted up, gold will be found in the fluvial deposits. In general, the complete elemental composition of the ore under discussion (Au, Ag, Pb and Zn) is reflected in only short dispersion trains within the fluvial and lacustrine deposits. Gold anomalies, on the other hand, are extensive (up to 6 km) in the stream sediments within the glaciated valleys and will occur sorbed onto hydrous iron oxides and clays, as well as in the form of flattened (thin) gold particles. In the glaciated valleys, the gold geochemical anomalies in moraine, lacustrine and stream sediments properly reflect the mineralization in the drainage basin.