O.A. Vyshnevskyi, COMPOSITIONAL ZONING IN PYROPE FROM SEDIMENTARY DEPOSITS OF BUG AREA (UKRAINE): IMPLICATIONS FOR UNDERSTANDING THEIR PROVENANCE

English

https://doi.org/10.15407/mineraljournal.42.03.017

UDC 549.621.98 (477)

COMPOSITIONAL ZONING IN PYROPE FROM SEDIMENTARY DEPOSITS OF BUG AREA (UKRAINE): IMPLICATIONS FOR UNDERSTANDING THEIR PROVENANCE

O.A. Vyshnevskyi, PhD (Geology & Mineralogy), Senior Research Fellow, Leading Researcher

M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine

34, Acad. Palladin Ave., Kyiv, Ukraine, 03142

E-mail: vyshnevskyy@i.ua

http://orcid.org/0000-0002-7206-2185

Language: English

Mineralogical journal 2020, 42 (3): 17-26

Abstract: According to earlier concepts detrital pyrope crystals from Paleogene, Neogene and Quaternary sediments of the Upper and Middle Bug area are of kimberlitic origin. In this paper we present another hypothesis on their provenance. A purposeful microprobe examination of more than 1000 grains showed that in each sediment sample 1 to 2% of pyrope crystals are chemically inhomogeneous. With the exception of this feature, the discovered zoned garnets are completely identical in chemical composition as well as morphologically to the bulk of the detrital pyropes of the mentioned area, which indicates their single primary sources. In these crystals of 200—300 µm in size the Fe and partly Mn contents gradually increase and Mg decreases from one edge to the other, while contents of other components (Ti, Ca and Cr) do not change, or change very slightly. The (Fe + Mn) — Mg zoning is strongest in a narrow area of 40—100 µm width near the grain rim. Maximum and minimum values of Mg and Fe content and their ranges in each garnet crystal are individual and differ from each other, but their average gradients of about 0.01 apfu per 10 μm are approximately the same. The total range for Mg in analyzed garnets is 1.38—2.34 apfu (normalized to 12 oxygen), which corresponds to 46—75 mol.% of pyrope component; for Fe it is 0.45—1.09 apfu and 14 to 37 mol.% of almandine component. The character of chemical patterns (continuous smooth concentration profiles for Mg and Fe, together with an almost uniform distribution of Ti, Cr, Ca) indicates that most likely in the studied garnets there is a primary retrograde diffusion-induced zoning. Application of classical thermobarometry suggests that diffusion started to occur at temperature of about 850 °C and froze at 650°C, while pressure remained almost unchanged near 2.0 GPa. An estimation of cooling rates required to fit zoning profiles in studied garnets yields values of about 2 to 10°C/Ma. In summary, in terms of the chemical composition and character of zoning the detrital pyropes of the Upper and Middle Bug area are most comparable to pyropes of orogenic peridotites. Given this, peridotites or similar rocks are suggested as the most probable primary sources of detrital pyropes within this region. However, the question on their location, proximal-regional or far distal, has no clear answer.

Keywords: pyrope, compositional zoning, diffusion, cooling rates, provenance, Upper and Middle Bug area.

References:

  1. Afanasiev, V.P., Nikolenko, E.I., Tychkov, N.S., Titov, A.T., Tolstov, A.V., Kornilova, V.P. and Sobolev, N.V. (2008), Geologyia i Geofizyka, Vol. 49, No. 2, Novosibirsk, RU, pp. 120-127 [in Russian]. https://doi.org/10.1016/j.rgg.2008.01.001
  2. Vyshnevskyi, О.А., Pavliuk, О.V. and Pavliuk, V.М. (2012), Mineral. Journ. (Ukraine), Vol. 34, No. 1, Kyiv, UA, pp. 25-34 [in Ukrainian].
  3. Vyshnevskyi, О.А. (2014), Dopov. Nac. akad. nauk Ukr., No. 3, Kyiv, UA, pp. 98-103 [in Ukrainian]. https://doi.org/10.15407/dopovidi2014.03.098
  4. Vyshnevskyi, О.А. (2015), Zap. Ukr. mіneral. tov., Vol. 12, Kyiv, UA, pp. 130-133 [in Ukrainian].
  5. Heiko, Yu.V., Hurskyi, D.S., Lykov, L.I., Metalidi, V.S., Pavliuk, V.N., Prykhodko, V.L., Tsymbal, S.N. and Shymkiv, L.M. (2006), Perspektivy korennoi almazonosnosti Ukrainy, Tsentr Europy publ., Kyiv-Lviv, UA, 223 p. [in Russian].
  6. (1998), Geologicheskaya karta Ukrainy i Moldovy, 1 : 1000000.
  7. Druzhynin, L.M., Hritsik, K.P., Lavrov, D.A. and Smirnov, G.I. (1976), Dopov. AN UkrRSR, Ser. B, No. 6, UA, pp. 491-493 [in Ukrainian].
  8. Lazko, Е.Е. and Serenko, V.P. (1983), Izvestiya AN SSSR, Ser. Geol., No. 12, RU, pp. 41-53 [in Russian].
  9. Serenko, V.P., Nikishov, K.N. and Lazko, Е.Е. (1982), Dokl. AN SSSR, Vol. 267, No. 2, RU, pp. 438-441 [in Russian].
  10. Sobolev, N.V. (1974), Glubinnye vkliucheniya v kimberlitakh i problema sostava verkhnei mantii, Nauka, Novosybirsk, RU, 261 p. [in Russian].
  11. Tychkov, N.S., Pokhilenko, N.P., Kuligin, S.S. and Malygina, E.V. (2008), Geologyia i Geofizyka, Vol. 49, No. 4, Novosibirsk, RU, pp. 302-318 [in Russian]. https://doi.org/10.1016/j.rgg.2007.11.009
  12. Burgess, S.R. and Harte, B. (1999), Proc. 7th Kimberlite Conf. (Dawson volume), Cape Town, pp. 66-80.
  13. Das, S. and Basu, A.R. (2019), Int. Geol. Rev. https://doi.org/10.1080/00206814.2019.1703223
  14. Ganguly, J., Cheng, W. and Chakraborty, S. (1998), Contribs Mineral. and Petrol., Vol. 131, pp. 171-180. https://doi.org/10.1007/s004100050386
  15. Grütter, H.S., Gurney, J.S., Menzies, A.H. and Winter, F. (2004), Lithos, Vol. 77, Iss. 1-4 [special issue], P. 841—857. https://doi.org/10.1016/j.lithos.2004.04.012
  16. Grütter, H., Latti, D. and Menzies, A. (2006), J. Petrol., Vol. 47, No. 4, pp. 801-820. https://doi.org/10.1093/petrology/egi096
  17. Hunter, W.C. and Smith, D. (1981), Contribs Mineral. and Petrol., Vol. 76, pp. 312-320. https://doi.org/10.1007/BF00375458
  18. Jollands, M.C., Hanger, B.J., Yaxley, G.M., Hermann, J. and Kilburn, M.R. (2018), Earth. Planet. Sci. Lett., Vol. 481, pp. 143-153. https://doi.org/10.1016/j.epsl.2017.10.021
  19. Kargin, A.V., Sazonova, L.V., Nosova, A.A. and Tretyachenko, V.V. (2016), Lithos, Vol. 262, pp. 442-455. https://doi.org/10.1016/j.lithos.2016.07.015
  20. Medaris, G.Jr., Wang, H., Jelınek, E., Mihaljevic M., and Jakes, P. (2005), Lithos, Vol. 82, pp. 1-23. https://doi.org/10.1016/j.lithos.2004.12.004
  21. Medaris, G.Jr., Ackerman, L., Jelinek, E., Toy, V., Siebel, W. and Tikoff, B. (2009), J. Geosci., Vol. 54, pp. 301-323. https://doi.org/10.3190/jgeosci.052
  22. Nimis, P. and Trommsdorff, V. (2001), J. Petrol., Vol. 42, No. 1, pp. 103-115. https://doi.org/10.1093/petrology/42.1.103.
  23. O’Neill, H.S.C. and Wood, B.J. (1979), Contribs Mineral. and Petrol., Vol. 70, pp. 59-70. https://doi.org/10.1007/BF00371872
  24. Smith, D. and Boyd, F.R. (1992), Contribs Mineral. and Petrol., Vol. 112, pp. 134-147. https://doi.org/10.1007/BF00310960
  25. Spengler, D., van Roermund, H.L.M. and Scheffler, F. (2019), Lithos, Vol. 350-351. https://doi.org/10.1016/j.lithos.2019.105217
  26. Taylor, L.A. and Neal, C.R. (1989), J. Geol., Vol. 97, pp. 551-567. https://doi.org/10.1086/629334
  27. van Roermund, H.L.M. (1989), The Caledonide Geology of Scandinavia, London, Graham and Trotman, pp. 205-219. https://doi.org/10.1007/978-94-009-2549-6_17
  28. van Roermund, H.L.M., Drury, M.R., Barnhoorn, A. and De Ronde, A. (2001), J. Petrol., Vol. 42, pp. 117-130. https://doi.org/10.1093/petrology/42.1.117
  29. Vrabec, M. (2010), Geologija, Vol. 53, No. 1, pp. 21-36. https://doi.org/10.5474/geologija.2010.002
  30. Vyshnevskyi, O.A. (2019), Abstr. Sci. conf., dedicated to the 50th Anniversary of M.P. Semenenko Inst. of Geochemistry, Mineralogy and Ore Formation NAS of Ukraine, Kyiv, May 14-16, 2019, in 2 vol. M.P. Semenenko IGMOF NAS of Ukraine, Kyiv, UA, Vol. 1, pp. 134-135.
  31. Wang, L., Essene, E.J. and Zhang, Y. (1999), Contribs Mineral. and Petrol., Vol. 135. pp. 164-178. https://doi.org/10.1007/s004100050504

PDF

File_attachments: 
PDF icon 17-26.pdf