NUMERICAL SIMULATION OF MAGMA MINGLING (CASE OF BAYANKOL GABBRO‐GRANITE SERIES, SANGILEN, TUVA)

A new numerical model has been developed that makes it possible to describe the process of formation of a dyke of a combined composition on the basis of the dynamics of a viscous compressible fluid. The numerical thermo‐mechanical model shows the processes of magma mingling and taking into account multiphase interaction of melts which are different in composition and properties. The models suggest a mechanism for uplifting of high‐density mafic enclaves in a chamber/dyke filled with salic magma by gravitational floating in the enclosing gran‐ ite magma that has been cooled and lost volatile components. The performed simulation shows that the main parame‐ ter controlling the shape and size of the ascending bodies is the difference in densities. The viscosity contrast determines whether interpenetration and hybridization of magmas occur. The limiting ratio of felsic material in the mix‐ ture, which is capable of uplifting denser mafic enclaves, is estimated. The duration of melt uplifting in combined dykes is estimated with respect to the viscosity parameters. At a typical rate of 2–3 km per year, it amounts to almost 12 months.

magma mingling, mixing, convection, melt, viscosity, crystallization, numerical modeling, combined dyke

1. ANSYS Fluent Theory Guide, 2009. Release 12.1.

2. Asimow P.D., Ghiorso M.S., 1998. Algorithmic modifications extending melts to calculate subsolidus phase relations. American Mineralogist 83 (9–10), 1127–1132. https://doi.org/10.2138/am-1998-9-1022.

3. Bohrson W.A., Spera F.J., Ghiorso M.S., Brown G.A., Creamer J.B., Mayfield A., 2014. Thermodynamic model for energyconstrained open-system evolution of crustal magma bodies undergoing simultaneous recharge, assimilation and crystallization: the magma chamber simulator. Journal of Petrology 55 (9), 1685–1717. https://doi.org/10.1093/petrology/egu036.

4. Burmakina G.N., Tsygankov A.A., 2013. Mafic microgranular enclaves in Late Paleozoic granitoids in the Burgasy quartz syenite massif, western Transbaikalia: Composition and petrogenesis. Petrology 21 (3), 280–303. https://doi.org/10.1134/S086959111303003X.

5. Dokukina K.A., Konilov A.N., Kaulina T.V., Vladimirov V.G., 2010. Interaction between mafic and felsic magmas in subvolcanic environment (Tastau igneous complex, Eastern Kazakhstan). Russian Geology and Geophysics 51 (6), 625–643. https://doi.org/10.1016/j.rgg.2010.05.004.

6. Fischer L.A., Wang M., Charlier B., Namur O., Roberts R.J., Veksler I.V., Cawthorn R.G., Holtz F., 2016. Immiscible iron- and silica-rich liquids in the Upper zone of the Bushveld Complex. Earth and Planetary Science Letters 443, 108–117. https://doi.org/10.1016/j.epsl.2016.03.016.

7. Ghiorso M.S., Sack R.O., 1995. Chemical mass-transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated-temperatures and pressures. Contribution to Mineralogy and Petrology 119 (2–3), 197–212. https://doi.org/10.1007/BF00307281.

8. Gutierrez F., Parada M.A., 2010. Numerical modeling of time-dependent fluid dynamics and differentiation of a shallow basaltic magma chamber. Journal of Petrology 51 (3), 731–762. https://doi.org/10.1093/petrology/egp097.

9. Hopson C.A., Mattinson J.M., 1994. Chelan migmatite complex: Field evidence for mafic magmatism, crustal anatexis, mixing and protodiapiric emplacement. In: D.A. Swanson, R.A. Haugerud (Eds.), Geology field trips in the Pacific Northwest. GSA Annual Meeting. University of Washington, Seattle, p. 2001–2021.

10. Karmysheva I.V., Vladimirov V.G., Vladimirov A.G., 2017. Synkinematic granitoid magmatism of Western Sangilen, South-East Tuva. Petrology 25 (1), 87–113. https://doi.org/10.1134/S0869591117010040.

11. 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.

12. Kozakov I.K., Sal’nikova E.B., Bibikova E.V., Kirnozova T.I., Kotov A.B., Kovach V.P., 1999. Polychronous evolution of the paleozoic granitoid magmatism in the Tuva-Mongolia massif: U-Pb geochronological data. Petrology 7 (6), 592–601.

13. Litvinovsky B.A., Zanvilevich A.N., Kalmanovich M.A., 1995. 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].

14. Persikov E.S., Bukhtiyarov P.G., 2009. Interrelated structural chemical model to predict and calculate viscosity of magmatic melts and water diffusion in a wide range of compositions and T-P parameters of the Earth's crust and upper mantle. Russian Geology and Geophysics 50 (12), 1079–1090. https://doi.org/10.1016/j.rgg.2009.11.007.

15. Petrelli M., Perugini D., Poli G., 2006. Time-scales of hybridisation of magmatic enclaves in regular and chaotic flow fields: petrologic and volcanologic implications. Bulletin of Volcanology 68 (3), 285–293. https://doi.org/10.1007/s00445-005-0007-8.

16. Petrova A.Yu., 2001. Rb-Sr Isotope System of Metamorphic and Magmatic Rocks of the Western Sangilen (SouthEastern Tuva). Author’s brief thesis (Candidate of Geology and Mineralogy). IMGRE, Moscow, 26 p. (in Russian) [Петрова А.Ю. Rb-Sr изотопная система метаморфических и магматических пород Западного Сангилена (Юго-Восточная Тува): Автореф. дис. … канд. геол.-мин. наук. М.: ИМГРЭ, 2001. 26 с.].

17. Ponomareva A.P., Izokh E.P., Andreeva N.V., 1994. Interaction of mantle and crustal melts during the formation of the Magadan batholith. Geologiya i Geofizika (Russian Geology and Geophysics) 35 (2), 25–34 (in Russian) [Пономарева А.П., Изох Э.П., Андреева Н.В. Взаимодействие мантийных и коровых расплавов при формировании Магаданского батолита // Геология и геофизика. 1994. Т. 35. № 2. С. 25–34].

18. Rosenberg C.L., Handy M.R., 2005. Experimental deformation of partially melted granite revisited: implications for the continental crust. Journal of Metamorphic Geology 23 (1), 19–28. https://doi.org/10.1111/j.1525-1314.2005.00555.x.

19. Semenov A.N., Polyansky O.P., 2017. Numerical modeling of the mechanisms of magma mingling and mixing on the example of the complex intrusions formation. Russian Geology and Geophysics 58 (11) (in press) (in Russian) [Семенов А.Н., Полянский О.П. Численное моделирование механизмов минглинга и миксинга магмы на примере формирования сложных интрузивов // Геология и геофизика. 2017. Т. 58. № 11 (в печати)].

20. Shelepaev R.A., 2006. Evolution of Basic Magmatism, Western Sangilen (South-Eastern Tuva). Author’s brief thesis (Candidate of Geology and Mineralogy). Novosibirsk, 16 p. (in Russian) [Шелепаев Р.А. Эволюция базитового магматизма Западного Сангилена (Юго-Восточная Тува): Автореф. дис. … канд. геол.-мин. наук. Новосибирск, 2006. 16 с.].

21. Simakin A.G., Bindeman I.N., 2012. Remelting in caldera and rift environments and the genesis of hot, “recycled” rhyolites. Earth and Planetary Science Letters 337–338, 224–235. https://doi.org/10.1016/j.epsl.2012.04.011.

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

23. Spera F.J., Schmidt J.S., Bohrson W.A., Brown G.A., 2016. Dynamics and thermodynamics of magma mixing: Insights from a simple exploratory model. American Mineralogist 101 (3), 627–643. https://doi.org/10.2138/am-2016-5305.

24. Veksler I.V., Dorfman A.M., Borisov A.A., Wirth R., Dingwell D.B., 2007. Liquid immiscibility and evolution of basaltic magma. Journal of Petrology 48 (11), 2187–2210. https://doi.org/10.1093/petrology/egm056.

25. Vladimirov V.G., Karmysheva I.V., Yakovlev V.A., 2016. Two groups of magmatic mingling (on the example of the Early Caledonides of Western Sangilen, South-Eastern Tuva). In: Correlation of the Altaides and Uralides: magmatism, metamorphism, stratigraphy, geochronology, geodynamics and metallogeny. Proceedings of the 3rd International scientific conference. Publishing House of SB RAS, Novosibirsk, p. 52–53 (in Russian) [Владимиров В.Г., Кармышева И.В., Яковлев В.А. Две группы магматического минглинга (на примере ранних каледонид западного Сангилена, Юго-Восточная Тува) // Корреляция алтаид и уралид: магматизм, метаморфизм, стратиграфия, геохронология, геодинамика и металлогения: Материалы Третьей международной научной конференции. Новосибирск: Изд-во СО РАН, 2016. C. 52–53].

26. Vladimirov V.G., Vladimirov A.G., Gibsher A.S., Travin A.V., Rudnev S.N., Shemelina I.V., Barabash N.V., Savinykh Ya.V., 2005. Model of the tectonometamorphic evolution for the Sangilen block (Southeastern Tuva, Central Asia) as a reflection of the Early Caledonian accretion–collision tectogenesis. Doklady Earth Sciences 405 (8), 1159–1165.

27. Weidendorfer D., Mattsson H.B., Ulmer P., 2014. Dynamics of magma mixing in partially crystallized magma chambers: textural and petrological constraints from the basal complex of the Austurhorn intrusion (SE Iceland). Journal of Petrology 55 (9), 1865–1903. https://doi.org/10.1093/petrology/egu044.