Eocene valleys of Amangeldy district (Northern Kazakhstan) and bauxite content

Abstract

River valleys of Eocene age are described within the limits of Shoindykul Basin (western Kazakn shield) which contain bauxite ores. Ancient gullies and small valleys are filled with red beds of ephemeral streams alluvium, mostly of bauxite composition. Valleys 500 to 1600 meters wide are filled with proper alluvium consisting of bauxite gravels, cross-bedded quartz clayey sands as well as with sheet-wash slope deposits, Within large valleys (2 to 3 kilometers wide) alluvium section includes two distinct members: lower member consists of cross-bedded coarse quartz sands, upper member mostly consists of horizontal layers of thin sands including large lenses and strata of kaolinite refractory clays.

Bauxite deposits types depend on the paleo-topographic position: sheet deposits on low flat interfluves, linear dipping bodies on slopes of paleo-valleys, ribbon-like deposits within gullies and small valleys and lenticular deposits forming separate bodies at the base of alluvium in valleys up to 1 kilometer wide.