Features of sedimentation and volcanism of the Tastauskaya rift structure in Central Kazakhstan

Research subject. A meridional Tastau rift structure located in the Famenian sub-latitude rift system of Central Kazakhstan was investigated, including the specific features of its constituent sediments and volcanism, as well as the stages of its development.

Materials and methods. The study was based on data collected during a long period of fieldwork, including a detailed study of the sequence of sedimentation processes, large-scale geocarting, sampling for various types of precision analyses.

Results. The typomorphic features of the main rock types were determined. It was shown that basaltoid rocks occurred in the form of pillow structures with a hyaloclastite matrix between the pillows. Siliceous shales are saturated with thin ash silicic acid material. A geological scheme of the Tastau structure and its specific features was presented in a series of cross-sections. The developmental stages of this structure were established. The structure was referred to the rift type.

Conclusion. The material and structural features of the investigated Tastau section are shown to be typical of the entire rift system of Central Kazakhstan. The pre-rift (Frasnian) stage is characterized by continental volcanism in the form of highpotassium and ultra-potassium rhyolite ignimbrites composing an encialic island-arc structure. These volcanites belong to the shoshonite and high-potassium lime-alkaline petrochemical series. The rift stage itself began in the Early Famenian age with the formation of a system of narrow deep troughs, into which the sea from the neighbouring Zhongaro-Balkhash sea region started to ingress. The conglomerates are characterized by thin flattened isometric pebbles, whose well-polished surface is similar to that of pebbles in modern sea beaches. The sandstones exhibit a high level of lamination and are characterized by poorly pelletized clastic material. The clastic material is represented by the underlying Frasnian rhyolitic ignimbrites carried in from the sides of the trough. The mature rift stage is characterized by the accumulation (under marine conditions) of pillow basalts and hyaloclastites and thin-layered silicite-clay-carbonate shales with abundant ash. The postrift stage is responsible for the formation of layered limestones of the Lower Tournaisian, developed also widely beyond the specified rift trough. 

1. Bakhteev M.K., Vasjukov Yu.A. (1980) Structural-facies zonation and tectonic development history of Atasui ore district (Central Kazakhstan) during Paleozoic. Izv. Vyssh. Uchebn. Zaved. Geol. Razved., (2), 51-59. (In Russian)

2. Burshtein E.F., Kosheleva I.A., Tevelev Al.V. (1996) Ultrakali volcanism of Central Kazakhstan: distribution, age, metallogenic significance. Moskovskaya shkola geologov v Kazakhstane. K 45-letiyu Tsentral’noKazakhstanskoi expeditsii geologicheskogo fakulteta MGU (Moscow school of geologists in Kazakhstan. To the 45th anniversary of the Central Kazakhstan expedition of Geology faculty of Moscow state University). Moscow, Moscow St. Univ. Publ., 94-109. (In Russian)

3. Evensen N.M., Hamilton P.J., OʼNions R.K. (1978) Rare earth abundance in chondritic meteorites. Geochim. Cosmochim Acta., 42(8), 1199-1212.

4. Geologiya i metallogeniya Uspenskoi tekctonicheskoi zony (Geology and metallogeny of the Uspenskaya tectonic zone). V. 5. (1969) Alma-Ata, Nauka Kazakh SSR Publ., 256 p. (In Russian)

5. Kurchavov A.M. (1995) Types of island-arc volcanic areals in the Devonian orogenic volcanic belt of the Central Kazakstan. 5-ya konferentsiya pamyati Zonenshaina poplitnoi tektonike (5th Zonenshain conference on plate tectonics). Abstracts. Moscow, GEOS Publ., 76-77. (In Russian)

6. Kurchavov A.M. (2002) Features of consruction and composition of Tastau rift magmatites structures of Central Kazakhstan. Rifty litosfery. Materialy Mezhdunarodnoi nauchnoi konferentsii (Rifts of the lithosphere. Proceedings of the International Scientific conference). Ekaterinburg, IGG UrO RAN, 242-43. (In Russian)

7. Kurchavov A.M., Grankin M.S., Malʼchenko E.G., Zhukovskii V.I., Khamzin B.S., Mazurov A.K., Khamza S.Kh. (2000) Zoning, Segmentation, and Paleogeodynamics of the Devonian Volcanic Belt in Central Kazakhstan. Geotektonika, (4), 32-43.

8. Mal’chenko E.G., Grankin M.S., Kurchavov A.M. (1998) On geodynamic situation of Upper Devonian volcanits formations of Uspenskaya, Akbastau and AkzhalAksoran zones in Central Kazakhstan. Geologiya i razvedka nedr Kazakhstana, (4), 28-30. (In Russian)

9. Pearce J.A. (1982) Trace element characteristics of lavas from destructive plate boundaries (Ed. R.S. Thorpe). Andesites. Wiley. Chichester, 525-548.

10. Pearce J.A., Gale G.H. (1977) Identification of oredeposition environment from trace element geochemistry of associated igneous host rocks. Geol. Soc. Spec. Publ., 14-24.

11. Weimarn A.B. (1991) Famenian volcanism as an indicator of geodynamic conditions and ore bearing. Magmatizm i rudonosnost’ Kazakhstana (Magmatism and ore-bearing of Kazakhstan). Alma-Ata, Gylym Publ., 203-211. (In Russian)

12. Weimarn A.B., Kapsamun V.I. (1981) Famen volcanism of Central Kazakhstan in connection with the problem of iron-manganese mineralization. Vulkanogenno-osadochnyi lito- i rudogenez (Volcanogenic-sedimentary litho- and ore genesis). Alma-Ata, Nauka Kazakh SSR Publ., 88-96. (In Russian)

13. Veimarn A.B., Milanovsky E.E. Famenian rifting on the example of Kazakstan and some other regions of Eurasia. Article 1. Bull. MOIP. Otd. Geol., 65(4), 34-47. (In Russian)

14. Yurina A.L., Kabanov Yu.F., Kagarmanov A.Kh., Kurchavov A.M. (1989) Paleobotanical justification of intra-Givetian disagreement in the Devonian of the NorthWestern part of the Jungar-Balkhash folded region (Central Kazakhstan). Zapiski Gornogo instituta, 119, 75-81. (In Russian)