Spherules with “titanium” shells in debris of carbonate composition among metagravelites of the black shale sequence of the Neoproterozoic Akshiryak Ridge (Middle Tien Shan)

Research subject. Various carbonate spherical formations having shells of different compositions and forming clusters in the composition of limestone fragments in metagravelites of the flyschoid black shale section of the Vendian hanging wall of the ore-bearing structure of the Kumtor deposit.

Aim. To assess the entire diversity of the population of carbonate spherules with similar shells, from the point of view of establishing possible variants of the nature of their formation and the material composition of the spherule shells.

Materials and methods. A series of sections of the Vendian flyschoid black shale sequence of the hanging wall of the ore-bearing structure of the Kumtor deposit with horizons of specific metagravelites containing carbonate fragments with clusters of spherules was studied. Samples of metagravelites from borehole cores were studied by optical methods, with diagnostics of mineral formations in thin sections, polished sections and polished sections. A scanning electron microscope (SEM) was used to work with one of the samples. Individual areas of the polished thin section were analyzed to obtain energy-dispersive X-ray spectra (EDS) and multi-level elemental EDS maps.

Results. Metagravelites are observed as a marker horizon in the composition of the terrigenous rhythmite sequence – flyschoid interbedding of carbonaceous phyllites, psammitic phyllites, and polymictic sandstones with carbonate cement in the section of rocks of the hanging wall of the ore-bearing structure of the Kumtor gold deposit. In the composition of most carbonate fragments of metagravelites, various spherical formations with individual sizes, external shells and, often, internal structure were found. They form clusters of different density, the distribution of which does not go beyond the carbonate fragments in metagravelites. In the composition of the studied external shells of spherules, the presence of titanium in the mineral form of rutile has been established to date.

Conclusions. The observed spherules belong to syn-, diagenetic formations of pelitomorphic carbonate sediments, destroyed and redeposited later as gravel-sized limestone fragments in terrigenous sediments of a later age, which were subsequently metamorphosed. Based on their appearance and size, such spherule clusters were initially classified as peloids in carbonate rocks. However, the presence of specific external shells in all spherules, the diversity of their shapes and sizes, and, in some cases, their internal structure suggest the presence of objects of biological nature among them. The formation of mineral “titanium” shells around spherules within carbonate fragments occurred either during regional metamorphism or is associated with diagenesis of carbonate sediments containing spherules of biogenic origin with elevated titanium contents. These mineral shells contributed to the preservation of spherule shapes during subsequent transformations of terrigenous rocks under greenschist metamorphism.

1. Astaf’eva M.M., Gerasimenko L.M., Geptner A.R. et al. (2011) Fossil bacteria and other microorganisms in terrestrial rocks and astromaterials. Moscow, PIN RAN Publ., 172 p. (In Russ.)

2. Astaf’eva M.M., Rozanov A.Yu. (2012) Ancient weathering crusts as a habitat for terrestrial biota. Series “Geo-biological systems in the past”. Moscow, PIN RAN Publ., 57-68. http://www.paleo.ru/institute/files/early_colonization.pdf (In Russ.)

3. Bgatov A.V. (1999) Biogenic classification of chemical elements. Filosofiya Nauki, 2(6), 80-90. (In Russ.)

4. Cavalazzi B., Westall F., Cady S.L., Barbieri R., Foucher F. (2011) Potential fossil endoliths in vesicular pillow basalt, coral patch seamount, Eastern North Atlantic Ocean. Astrobiol., 11, 619-632.

5. Dick A.B. (1928) On Needles of Rutile in the Test of Bathesiphon argenteus. Trans. Edinburgh Geol. Soc., XII, 18-21.

6. Fedonkin M.A., Sergeev V.N. (2018) Pseudofossils, contaminants and other hazards of Archean and Proterozoic micropaleontology. Stratigr. Geol. Korrel., 26(3), 127-128. (In Russ.)

7. Fossil calcareous algae. (1987) Novosibirsk, Nauka Publ., 224 p. (Proceedings of the Institute of Geology and Geophysics SB USSR Academy of Sciences, Iss. 674). (In Russ.)

8. Fossil problems of the USSR. (1990) Moscow, Nauka Publ., 57-63. (In Russ.)

9. Foucher F., Westall F., Knoll A. (2012) Biosignatures observed by Raman mapping in silicified materials. European Geosciences Union, General Assembly. Vienna, Austria. V. 14, p. 4287.

10. Geptner A.R., Ivanovskaya T.A., Pokrovskaya E.V. (2005) Hydrothermal fossilization of microorganisms at the Earth’s Surface in Iceland. Lithol. Miner. Resour., 40, 505-520.

11. Johnston M.R., Raine J.I., Watters W.A. (1987) Drumduan group of east nelson, New Zealand: Plant-bearing Jurassic arc rocks metamorphosed during terrane interaction. J. Royal Soc. New Zealand, 17, 275-301.

12. Korolyuk I.K. (1960) Stromatolites of the Lower Cambrian and Proterozoic of the Irkutsk Amphitheater. Geological and geochemical research of oil and gas areas of the USSR. Moscow, AN SSSR Publ., 112-161. (In Russ.)

13. Lekele Baghekema S.G., Lepot K., Riboulleau A., Fadel A., Trentesaux A., El Albani A. (2017) Nanoscale analysis of preservation of ca. 2.1 Ga old Francevillian microfossils, Gabon. Precambr. Res., 301, 1-18.

14. Lisitsyn A.P., Lukashin V.N., Emel’anov E.M. et al. (1980) Titan. Ch. 4. Geochemistry of hydrolyzed elements. Moscow, Nauka Publ., 117-149. (In Russ.)

15. Liu Z.-R.R., Zhou M.-F., Williams-Jones A.E. et al. (2019) Diagenetic mobilization of Ti and formation of brookite/anatase in early Cambrian black shales, South China. Chem. Geol., 506(20), 79-96. https://doi.org/10.1016/j.chemgeo.2018.12.022

16. Logvinenko N.V. (1944) On the lithology and paleogeography of coal deposits in the northeast of Donbass. Dokl. Akad. Nauk, (5), 228-230. (In Russ.)

17. Meinhold G. (2010) Rutile and its applications in earth sciences. Earth-Sci. Rev., 102, 1-28. http://www.elsevier.com/locate/earscirev

18. Ogurtsova R.N., Sergeev V.N. (1989) Megaspheromorphids Chuaria from the Chichkan Formation of the Upper Precambrian of Southern Kazakhstan. Paleontol. Zhurn., (3), 119-122. (In Russ.)

19. Pitkovskaya P.N. (1953) On the geochemical facies of the Givetian and Frasnian periods in the territory of Western Bashkiria. Geological collection. In 3 v. V. 2. Leningrad; Moscow, Gostoptekhizdat Publ., 319 p. (In Russ.)

20. Precambrian microfossils of the USSR. (1989) (Ed. T.V. Jankauskas). Leningrad, Nauka Publ., 191 p. (In Russ.)

21. Preobrazhenskii I.A. (1941) About authigenic minerals and mineral formation. Tr. Inst. Geol. Nauk AN SSSR, ser. petrogr., 40(13), 41-54. (In Russ.)

22. Pustovalov L.V. (1956) Secondary changes in sedimentary rocks and their geological significance. On secondary changes in sedimentary rocks. Moscow, AN SSSR Publ., 3-52. (Tr. GIN AN SSSR, Iss. 5). (In Russ.)

23. Rengarten N.V. (1956) Titanium minerals in coal-bearing sedimentary rocks. On secondary changes in sedimentary rocks. Moscow, AN SSSR Publ., 125-134. (Tr. GIN AN SSSR, Iss. 5). (In Russ.)

24. Rojas-Agramonte Y., Kröner A., Alexeiev D.V., Jeffreys T., Khudoley A.K., Wong J., Geng H., Shu L., Semiletkin S.A., Mikolaichuk A.V., Kiselev V.V., Yang J., Seltmann R. (2014) Detrital and igneous zircon ages for supracrustal rocks of the Kyrgyz Tianshan and palaeogeographic implications. Gondw. Res., 26, 957-974.

25. Saburin M.Yu. (2004) Phytocenoses of the Black Sea cystoseira: structure, restoration and prospects for use. Disse. ... cand. biol. sci. Moscow, RGB OD Publ., 146 p. (In Russ.)

26. Sagyndykov K.S. (1987) Development of a stratigraphic scheme and working legend of the Precambrian–Lower Paleozoic of the Akbel Party’s work area. Frunze, IG AN Kyrgyzstan. SSR Publ., 105 p. (In Russ.)

27. Sapurin S.A., Mizens G.A. (2014) On the formation conditions of peloidal limestones of the eastern slope of the Middle Urals. Tr. IGG UrO RAN, vyp. 161, 108-111. (In Russ.)

28. Schopf J.W. (1999) Fossils and pseudofossils: lessons from the hunt for early life on Earth. Size limits of very small microorganisms. Washington DC, National Academy Press, 88-93.

29. Serdyuchenko D.P., Dobrotvorskaya L.V. (1949) On some mineral neoformations in sedimentary rocks. Dokl. Akad. Nauk SSSR, LXIX(3), 421-424. (In Russ.)

30. Sergeev V.N. (1992) Silicified microfossils of the Precambrian and Cambrian of the Urals and Central Asia. Moscow, Nauka Publ., 139 p. (Tr. GIN AN SSSR, Iss. 474). (In Russ.)

31. Shevkunov A.G., Kornitskii A.I., Bashkirov A.P., Aidarkulov T.N. (2023) Kumtor gold deposit (Middle Tien Shan, Kyrgyzstan) and the application of three-dimensional modeling in the program Leapfrog Geo (Seequent) during geological exploration. Rudy i Metally, (2), 18-43. (In Russ.)

32. Sirantoine E., Wacey D., Bischoff K., Saunders M. (2021) Authigenic anatase within 1 billion-year-old cells. Geobiol., 19, 3-17.

33. Stratified formations of Kyrgyzstan. (2015) (A.V. Dzhenchuraeva, I.L. Zakharov, Yu.V. Zhukov et al.). Bishkek, Izd-vo KRSU, 338 p. (In Russ.)

34. Terbishalieva B., Timmerman M.J., Mikolaichuk A., Altenberger U., Sláma J., Schleicher A.M., Sudo M., Sobel E.R., Cichy S.B. (2021) Calcalkaline volcanic rocks and zircon ages of the late Tonian: early Cryogenian arcrelated Big Naryn Complex in the Eastern DjetimToo Range, Middle Tianshan block, Kyrgyzstan. Int. J. Earth Sci., 110, 353-375 https://doi.org/10.1007/s00531-020-01956-z

35. Timofeev B.V. (1969) Proterozoic spheromorphids. Leningrad, Nauka Publ., 67 p. (In Russ.)

36. Toporski J.K.W., Steele A., Westall F., Avci R., Martill D.M., McKay D.S. (2002) Morphologic and spectral investigation of exceptionally well-preserved bacterial biofilms from the Oligocene Enspel formation, Germany. Geochim. Cosmochim. Acta, 66(10), 1773-1791. https://doi.org/10.1016/S0016-7037(01)00870-5

37. Tucker M., Wright P. (2002) Carbonate sedimentology. Oxford: Blackwell Science Ltd., 482 p.

38. Veis A.S. (1993) Precambrian organ-wall microfossils are the most important component of ancient biota. Problems of pre-anthropogenic evolution of the biosphere. Moscow, Nauka Publ., 265-282. (In Russ.)

39. Vernadskii V.I. (1954) Essays on geochemistry. Selected works. V. I. AN SSSR, 61-89. (In Russ.)

40. Vologdin A.G. (1962) The oldest algae of the USSR. Moscow, AN SSSR Publ., 655 p. (In Russ.)

41. Yudovich Ya.E., Ketris M.P., Rybina N.V. (2018) Geochemistry of titanium. Syktyvkar, IG Komi NTs UrO RAN Publ., 432 p. (In Russ.)