Isotopic and Geochemical Characteristics of Cambrian Phosphorites of Karatau Basin (southern Kazakhstan)

The article is devoted to studying of isotope-geochemical characteristics of phosphorite and the enclosing carbonate Karatau Phosphorus deposit. As a result of the work on the identification of the least altered rocks, the primary isotopic composition of Sr, C and O in the water of the Karatau basin was established, as well as the isotopic composition of Nd phosphorites. Kyrshabakty Formation underlying phosphorite characterized Sr-87/Sr-86 ratio 0.70839, delta C-13 value ranges from +0.2 to 0.6 parts per thousand. The primary Sr isotopic composition of the phosphate-bearing Chulaktau Formation, varies from 0.70877 to 0.70905, and the carbon isotope composition ranges from -3.1 to 0.8 parts per thousand. Based on these data, the sedimentation interval of these rocks was established. Phosphate accumulation within the Karatau basin occurred in the range of 520-509 million years ago as a result of biogenic precipitation of the phosphorus of ocean water on the shelf of the passive margin of the continent.