Abstract

The study of structural features along with carbon and oxygen isotope compositions made it possible to discriminate lithological rocks in deposits of the Karatau phosphorite basin (Kazakhstan) into the following types: high- and low-grade phosphorites; unaltered and altered dolomites (with and without phosphate) hosting phosphorites of the Chulaktau Formation (lower dolomite and Fe–Mn horizons); dolomites of the underlying and overlapping rocks of the Malokaroi and Dzhanat groups and the Shabakta Formation; calcareous schists, sandstones, as well as secondary calcite. The carbonate material in rocks of the studied deposits is heterogeneous and characterized by wide variations of the δ¹³C (–7.6 to 1.6‰ PDB) and δ¹⁸O (15.4 to 27.0‰ SMOW) values. The results obtained suggest that phosphorites and host rocks underwent intense postsedimentary transformations. Isotopic (δ¹³C, δ¹⁸O) composition of the carbonate material in rocks of the siliceous and productive (phosphorite) horizons, as well as, to a large extent, the Fe–Mn horizon of the Chulaktau Formation is nonprimary and related to the presence of carbonates of superimposed (secondary) generations during the late diagenesis or catagenesis. In this regard, data on the carbon isotope composition obtained for rocks of the studied Karatau deposits cannot be used for the chemostratigraphic reconstructions.

中文翻译：

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小卡拉陶（哈萨克斯坦）的同位素组成（δ13 C，δ18 O）和磷矿床的碳酸盐成因

摘要

对结构特征以及碳和氧同位素组成的研究使得有可能将Karatau磷矿盆地（哈萨克斯坦）沉积物中的岩性岩石区分为以下类型：高品位和低品位磷矿；保留了丘拉克陶组磷矿的未改变和改变的白云石（含或不含磷酸盐）（较低的白云石和Fe-Mn层位）；Malokaroi和Dzhanat组以及Shabakta组的下伏和重叠岩石的白云岩；钙质片岩，砂岩以及次方解石。在所研究的沉积物的岩石的碳酸盐材料是异质的，其特征在于由所述的δ大范围变化¹³ C（-7.6〜1.6‰PDB）和δ ¹⁸O（15.4至27.0‰SMOW）值。获得的结果表明，磷矿和基质岩经历了强烈的沉积后转变。同位素（δ ¹³ C，δ ¹⁸ O）在硅质和生产性（磷）的视野的岩石中的碳酸盐材料的组合物，以及，在相当大程度上，Chulaktau形成的铁-锰地平线是非主以及与在成岩作用或成岩作用晚期叠加（次生）碳酸盐的存在。在这方面，从研究的卡拉陶矿床的岩石中获得的碳同位素组成数据不能用于化学地层重建。