GEOLOGY AND GEOCHEMISTRY OF SYNPLUTONIC DYKES IN THE CHELYABINSK GRANITOID MASSIF, SOUTH URALS

We present the results of geological, petro‐geochemical and mineralogical studies of synplutonic intrusive formations in the Chelyabinsk granitoid massif, South Urals. Numerous synplutonic intrusions in the study area are in early phases, composed of quartz diorites and granodiorites of the Late Devonian – Early Carboniferous. Such intru‐ sions are represented by a bimodal series of rocks from gabbro‐diorite to plagioleic granite. Both the mafic and salic members of the series form separate independent dykes and, jointly, compose the dyke bodies of complex structures. With respect to the relationships with host rocks, two types of the studied dykes are distinguished: (1) ‘classical’ synplutonic dykes with monolithic bodies that are split along strike by the enclosing granodiorite into separate frag‐ ments; and (2) ‘post‐granite’ dykes that clearly break through the host quartz diorites and granodiorites that are older that the dykes, but show similar isotope ages: the U‐Pb‐Shrimp ages of zircon in the samples taken from the dyke and the host quartz diorite are 362±4 и 358±5 Ma, respectively. The first group includes the dyke of melanocratic diorite, the second – granitoid dykes and dykes of gabbro‐diorites and diorites. The intrusion of acid rocks preceded the basites and was completed after their formation. As a result of the nearly simultaneous intrusion of both, the dykes of complex structures were formed. The material compositions of mafic rocks in these two groups are significantly dif‐ ferent. The ‘post‐granite’ dioritoids are moderately alkaline. Melanodiorite in the synplutonic dyke belongs to normal alkaline rocks. It has a very high content of MgO (12.5 mass %) and is sharply enriched with chromium (~700 ppm vs. 100–350 ppm in the ‘post‐granite’ dykes). It is thus closer to sanukitoids. The acid ‘post‐granite’ dykes vary in compo‐ sition from plagoleic granite and adamellite to tonalite. They are normal‐alkaline. Their chemical compositions often do not correspond to cotectic ones. The dioritoids have nearly zero values of ɛNd (from +1 to –2), and the values of (87Sr/86Sr)I vary from 0.70485 to 0.70571. The granitoids are typically characterized by negative values of ɛNd (from –2 to –5) and, generally, more radiogenic strontium ((87Sr/86Sr)i=0.70517–0.70567). The established isotopic com‐ positions of Nd and Sr in the synplutonic dykes of the Chelyabinsk Massif give evidence of different sources for the coexisting salic and mafic melts, but do not fit a model of simple mixing of the two components. 

1. Barbarin B., 1991. Enclaves of the Mesozoic calc-alkaline granitoids of the Sierra Nevada Batholith, California. In: J. Didier, B. Barbarin (Eds.), Enclaves and granite petrology. Development in petrology, vol. 13. Elsevier, Amsterdam – Oxford – New York – Tokyo, p. 135–153.

2. Barbarin B., 2005. Mafic magmatic enclaves and mafic rocks associated with some granitoids of the central Sierra Nevada batholith, California: nature, origin, and relations with the hosts. Lithos 80 (1–4), 155–177. https://doi.org/10.1016/j.lithos.2004.05.010.

3. Burmakina G.N., Tsygankov A.A., 2010. Mantle magmatism in granitoid petrogenesis of the Western Transbaikalia. In: Modern problems of geology and mineral exploration. Proceedings of the International Conference. TPU Publishing House, Tomsk, p. 31–35 (in Russian) [Бурмакина Г.Н., Цыганков А.А. Мантийный магматизм в гранитоидном петрогенезисе Западного Забайкалья // Современные проблемы геологии и разведки полезных ископаемых: Материалы международной конференции. Томск: Изд-во ТПУ, 2010. С. 31–35].

4. Castillo R.C., 2012. Adakite petrogenesis. Lithos 134–135, 304–316. https://doi.org/10.1016/j.lithos.2011.09.013.

5. Collins W.J., Richards S.R., Healy B.E., Ellison P.I., 2000. Origin of heterogeneous mafic enclaves by two-stage hybridisation in magma conduits (dykes) below and in granitic magma chambers. Transactions of The Royal Society of Edinburgh: Earth and Environmental Science 91 (1–2), 27–45. https://doi.org/10.1017/S0263593300007276.

6. D’Lemos R.S., 1992. Magma-mingling and melt modification between granitic pipes and host diorite, Guernsey, Channel Islands. Journal of the Geological Society 149 (5), 709–720. https://doi.org/10.1144/gsjgs.149.5.0709.

7. Fedorovsky V.S., Khromykh S.V., Sukhorukov V.P., Kuibida M.L., Vladimirov A.G., Sklyarov E.V., Dokukina K.A., Chamov S.N., 2003. Metamorphic mingling (a new type of mingling structure). In: Tectonics and geodynamics of continental crust. Proceedings of the XXXVI Tectonic conference. Vol. II. GEOS, Moscow, p. 255–259 (in Russian) [Федоровский В.С., Хромых С.В., Сухоруков В.П., Куйбида М.Л., Владимиров А.Г., Скляров Е.В., Докукина К.А., Чамов С.Н. Метаморфический минглинг (новый тип минглинг-структур) // Тектоника и геодинамика континентальной литосферы: Материалы XXXVI тектонического совещания. М.: ГЕОС, 2003. Т. II. С. 255–259].

8. Fershtater G.B., Bea F., Montero M.P., Scarrow J., 2004. Hornblende gabbro in the Urals: types, geochemistry, and petrogenesis. Geochemistry international 42 (7), 610–629.

9. Frost T.P., Mahood G.A., 1987. Field, chemical, and physical constraints on mafic-felsic magma interaction the Lamarck granodiorite, Sierra Nevada, California, USA. Geological Society of America Bulletin 99 (2), 272–291. https://doi.org/10.1130/0016-7606(1987)99<272:FCAPCO>2.0.CO;2.

10. Karmysheva I.V., Vladimirov V.G., Vladimirov A.G., Shelepaev R.A., Yakovlev V.A., Vasyukova E.A., 2015. Tectonic position of mingling dykes in accretion-collision system of early Caledonides of West Sangilen (South-East Tuva, Russia). Geodynamics & Tectonophysics 6 (3), 289–310. https://doi.org/10.5800/GT-2015-6-3-0183.

11. Litvinovsky B.A., Zanvilevich A.N., Kalmanovich M.A., 1995a. Multiple mixing of coexisting syenitic and basaltic magmas and its petrological implications, Ust’-Khilok massif, Transbaikalia. Petrologiya (Petrology) 3 (2), 133–157 (in Russian) [Литвиновский Б.А., Занвилевич А.Н., Калманович М.А. Многократное смешение сосуществующих сиенитовых и базитовых магм и его петрологическое значение, Усть-Хилокский массив, Забайкалье // Петрология. 1995. Т. 3. № 2. С. 133–157].

12. Litvinovsky B.A., Zanvilevich A.N., Lyapunov S.M., Bindeman I.N., Davis A.M., Kalmanovich M.A., 1995b. Model of composite basite-granitoid dike generation (Shaluta pluton, Transbaikalia). Geologiya i Geofizika (Russian Geology and Geophysics) 36 (7), 3–22 (in Russian) [Литвиновский Б.А., Занвилевич А.Н., Ляпунов С.М., Биндеман И.Н., Дэвис А.М., Калманович М.А. Условия образования комбинированных базит-гранитных даек (Шалутинский массив, Забайкалье) // Геология и геофизика. 1995. Т. 36. № 7. C. 3–22].

13. Marshall L.A., Sparks R.S.J., 1984. Origin of same mixed-magma and net-veined ring intrusions. Journal of the Geological Society 141 (1), 171–182. https://doi.org/10.1144/gsjgs.141.1.0171.

14. Martin H., Smithies R.H., Rapp R., Moyen J.-F., Champion D., 2005. An overview of adakite, tonalite–trondhjemite– granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos 79 (1–2), 1–24. https://doi.org/10.1016/j.lithos.2004.04.048.

15. Mazhari S.A., 2016. Petrogenesis of adakite and high-Nb basalt association in the SW of Sabzevar zone, NE of Iran: Evidence for slab meltemantle interaction. Journal of African Earth Sciences 116, 170–181. https://doi.org/10.1016/j.jafrearsci.2015.12.026.

16. Pitcher W.S., 1991. Synplutonic dykes and mafic enclaves. In: J. Didier, B. Barbarin (Eds.), Enclaves and granite petrology. Development in petrology, vol. 13. Elsevier, Amsterdam – Oxford – New York – Tokyo, p. 389–391.

17. Popov V.S., 1984. Magma mixing as petrogenetic process (review). Proceedings of the All-Union Mineralogical Society 113 (2), 229–240 (in Russian) [Попов В.С. Смешение магм – петрогенетический процесс (обзор иностранной литературы) // Записки Всесоюзного минералогического общества. 1984. Т. 113. № 2. С. 229–240].

18. Popov V.S., Tevelev A.V., Belyatsky B.V., Bogatov V.I., Petrova A.Yu., Zhuravlev D.Z., Osipova T.A., 2003. The isotopic composition of Nd and Sr in granitoids of the Urals as an indicator of the mantle–crust interaction. Proceedings of the All-Russia Mineralogical Society 132 (3), 16–38 (in Russian) [Попов В.С., Тевелев А.В., Беляцкий Б.В., Богатов В.И., Петрова А.Ю., Журавлев Д.З., Осипова Т.А. Изотопный состав Nd и Sr в гранитоидах Урала как показатель взаимодействия мантия–кора // Записки Всероссийского минералогического общества. 2003. Т. 132. № 3. C. 16–38].

19. Pribavkin S.V., 2000. Petrology of Basic Rocks in Granitoids of the Shabrov and Shartash massifs. Author's Abstract of PhD Thesis (Candidate of Geology and Mineralogy). Ekaterinburg, 28 p. (in Russian) [Прибавкин С.В. Петрология основных пород в гранитоидах Шабровского и Шарташского массивов: Автореф. дис. … канд. геол.-мин. наук. Екатеринбург, 2000. 28 с.].

20. Pribavkin S.V., Pushkarev E.V., 2011. The age of late orogenic granitoids of the Urals based on U-Pb isotope dating of zircons (Exemplified by the Shartash and Shabry massifs). Doklady Earth Sciences 438 (1), 627–631. https://doi.org/10.1134/S1028334X11050369.

21. Puchkov V.N., 2010. Geology of the Urals and Cis-Urals (Actual Problems of Stratigraphy, Tectonics, Geodynamics and Metallogeny). DesignPoligraphService, Ufa, 280 p. (in Russian) [Пучков В.Н. Геология Урала и Приуралья (актуальные вопросы стратиграфии, тектоники, геодинамики и металлогении. Уфа: ДизайнПолиграфСервис, 2010. 280 с.].

22. Pushkarev E.V., Osipova T.A., 1993. Granitoid inclusions in basic rocks of the Shabrov massif. Yearbook–1992. IGG UrB RAS, Ekaterinburg, p. 44–47 (in Russian) [Пушкарев Е.В., Осипова Т.А. Гранитоидные включения в базитах Шабровского массива // Ежегодник–1992. Екатеринбург: ИГГ УрО РАН, 1993. С. 44–47].

23. Qian Q., Hermann J., 2010. Formation of High-Mg diorites through assimilation of peridotite by monzodiorite magma at crustal depths. Journal of Petrology 57 (7), 1381–1416. https://doi.org/10.1093/petrology/egq023.

24. Sklyarov E.V., Fedorovskii V.S., 2006. Magma mingling: tectonic and geodynamic implications. Geotectonics 40 (2), 120–134. https://doi.org/10.1134/S001685210602004X.

25. Sun S.S., 1980. Lead isotopic study of young volcanic rocks from mid-ocean ridges, ocean islands and island arcs. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 297 (1431), 409–445. https://doi.org/10.1098/rsta.1980.0224.

26. Sun S.S., McDonough W.E., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: A.D. Sanders, M.J. Norry (Eds.), Magmatism in the oceanic basins. Geological Society, London, Special Publications, vol. 42, p. 313–345. https://doi.org/10.1144/gsl.sp.1989.042.01.19.

27. Tatsumi Y., 2008. Making continental crust: The sanukitoid connection. Chinese Science Bulletin 53 (11), 1620–1633. https://doi.org/10.1007/s11434-008-0185-9.

28. Titov A.V., Litvinovsky B.A., Zanvilevich A.N., Shadaev M.G., 2000. Hybridization in composite basic-rock-leucogranite dikes of the Ust’-Khilok massif (Transbaikalia). Geologiya i Geofizika (Russian Geology and Geophysics) 41 (12), 1714–1728.

29. Wiebe R.A. 1973. Relations between coexisting basaltic and granitic magmas in a composite dike. American Journal of Science 273 (2), 130–151. https://doi.org/10.2475/ajs.273.2.130.

30. Wiebe R.A., Ulrich R., 1997. Origin of composition dikes in the Gouldsboro granite, coastal Maine. Lithos 40 (2–4), 157–178. https://doi.org/10.1016/S0024-4937(97)00008-X.

31. Zin’kova E.A., Fershtater G.B., 2007. Synplutonic dykes in Verkhisetsk granitoid massif (Middle Ural). Litosfera (Lithosphere) (2), 141–151 (in Russian) [Зинькова Е.А., Ферштатер Г.Б., 2007. Синплутонические дайки в гранитоидах Верхисетского массива (Средний Урал) // Литосфера. 2007. № 2. C. 141–151].