The Karaotkel deposit of fossil Ti-Zr placers is situated in the north-western edge of the Zaysan intermontane depression in Eastern Kazakhstan. The geological structure of the mineral sands is characterized by complex morphology and a two-layered assembly, formed as the result of long-term regional geodynamic processes during the Meso- and Cenozoic.

Our study is aimed to establish a genetic model for the formation of the continental Karaotkel Ti-Zr placers by utilising novel data on geology, mineralogy, geochemistry and geochronology. Sedimentological facies analyses indicate an environment of coastal wave-built formation of the Late Cretaceous kaolin-dominated weathering crust and Paleogene sediments of the North Zaysan formation. A set of geochemical indices is applied on the base of key geochemical parameters of placer composition to allow quantitative and qualitative assessment and to establish genetic trends.

Mineralogical composition of the heavy fraction of the productive sediments of the Ti-Zr placer (horizon “A” of the North Zaysan formation) was determined by XRD and microprobe-probe analyses. Microprobe analyses determined the elemental composition of mineral grains of zircon, ilmenite, monazite, staurolite, titanite, epidote and gold. Gold and monazite were found also as micro-inclusions in minerals. The sediments of the horizon “A” are characterized by elevated grades of light rare-earth elements (LREE) over heavy rare-earth elements (HREE).

The weathering processes reveal a gradual transition from a moderately warm and humid climate to a cold and dry climate as the placer deposit was formed. The intercalations between horizontal- and crossbedding characterize the conditions of placers’ sedimentation by eluvial, eluvial-alluvial, alluvial-lacustrine and lacustrine environments. U-Pb dating of zircons from the productive horizon “A” of the Karaotkel placer deposit showed a crystallization age of 287 ± 1 Ma. This is identical with the age of the Karaotkel-Preobrazhenka multi-phase igneous intrusion suggesting that it can be considered as the source of the Karaotkel Ti-Zr placer. In addition, comparative analyses of elemental composition of zircons confirmed that monzonites and syenites of earlier phases of the Karaotkel-Preobrazhenka intrusion are the likely source rocks for the Karaotkel mineral sands.

The formation of these Ti-Zr placers comprise the following stages: 1) establishment of the bedrock of the Karaotkel-Preobrazhenka multiphase igneous intrusion of the Permian Cisuralian epoch; 2) development of weathering crust during Upper Cretaceous period; 3) washing-out of the weathering crusts during the North Zaysan formation in the Paleogene, and 4) differential redeposition by temporary streams that resulted in the accumulation of Ti and Zr minerals.

Ti-Zr化石砂岩的Karaotkel矿床位于哈萨克斯坦东部Zaysan山区间洼地的西北边缘。矿物砂的地质结构以复杂的形态和两层组合为特征，这是中，新生代长期区域地球动力学过程的结果。

我们的研究旨在通过利用地质，矿物学，地球化学和地球年代学方面的新数据，为大陆Karaotkel Ti-Zr砂矿的形成建立遗传模型。沉积相分析表明，晚白垩世高岭土为主的风化壳和北Zaysan组的古近纪沉积物形成了沿海岸波构造的环境。在砂矿成分的关键地球化学参数的基础上，应用了一组地球化学指标，以进行定量和定性评估并确定遗传趋势。

通过X射线衍射（XRD）和探针探针分析确定了Ti-Zr砂矿的大量生产沉积物（北Zaysan组的地平线“ A”）的矿物学组成。微量探针分析确定了锆石，钛铁矿，独居石，十字沸石，钛铁矿，山石和金矿矿物元素的元素组成。还发现金和独居石也是矿物中的微量夹杂物。地平线“ A”的沉积物的特征是轻稀土元素（LREE）的等级高于重稀土元素（HREE）的等级。

风化过程揭示了随着砂矿沉积物的形成，从中等温暖和潮湿的气候逐渐过渡到寒冷干燥的气候。水平垫层和交叉垫层之间的夹层表征了砂砾岩，砂砾冲积，冲积湖和湖泊环境的砂矿沉积条件。从Karaotkel砂矿生产层“ A”开始的锆石U-Pb测年表明，其结晶年龄为287±1 Ma。这与Karaotkel-Preobrazhenka多相火成岩侵入的年龄相同，表明它可以被视为Karaotkel Ti-Zr砂矿的来源。此外，

这些Ti-Zr砂矿的形成包括以下几个阶段：1）建立二叠纪Cisuralian时代的Karaotkel-Preobrazhenka多相火成岩的基岩；2）上白垩纪风化壳的发育；3）在古近纪的北部Zaysan组中洗去了风化壳，以及4）临时流的差异性再沉积，导致Ti和Zr矿物的积累。