Karatau Phosphorite-Bearing Basin

one of the largest such basins in the world, located in Dzhambul and Chimkent oblasts, Kazakh SSR; a 25-km-wide belt stretching more than 120 km along the northeastern slopes of the Karatau Mountains.

Phosphorite, or phosphate rock, was first exploited in the Karatau Basin during the Great Patriotic War of 1941–45. The rock is found associated with Lower Cambrian Chulaktau series. The total thickness of the productive horizon reaches 60 m; the phosphorite seams within may be as much as 30–35 m across. In the best monomineral or carbonate ores the P₂O₅ content may be as high as 25–30 percent. The ore bed is broken up by several longitudinal and transverse cracks into about 45 independent sectors that are considered individual deposits.

The Karatau Basin’s total ore reserve comes to 1.6 billion tons. Three deposits were being worked in 1970, the Aksai and the Zhanatas by the open pit method and the Chulaktau (which is today a suburb of Karatau), by an underground system of layered drifts.

There is a chemical-mining combine in the city of Karatau that produces phosphorite meal and flotation concentrate with a P₂O₅ content higher than 28 percent and market ore with more than 23 percent P₂O₅. The negative feature of the ores is their high magnesium oxide content. The city of Dzhambul has a superphosphate plant and a double-superphosphate plant. The 1971–75 Five-Year Plan for the Development of the National Economy of the USSR envisions a significant increase in the extraction capacities of the Karatau Phosphorite-Bearing Basin and the completion of construction on the Chimkent phosphorus plant and the Dzhambul double-superphosphate plant.