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Post-collision mafic-ultramafic magmatism of the Ukrainian shield (1800
Ma)
Leonid Shumlyanskyy
M.P. Semenenko Institute of geochemistry, mineralogy and ore formation,
Kyiv, Ukraine
lshumlyanskyy@yahoo.com
Application of the methods of in situ geochronology provides
growing evidence about importance of the still poorly understood
geological event that occurred at c. 1800 Ma. There are at least several
magmatic events occurred at this time among which are: (1) emplacement
of the “old anorthosite” (Amelin et al., 1994; Verkhogliad, 1995) and
oldest granites (Shumlyanskyy and Bogdanova, 2009) of the Korosten
plutonic complex; (2) intrusion of dolerite dykes and layered gabbroic
massifs in the North-Western region of the Ukrainian shield (Shumlyanskyy
et al., 2012; Bogdanova et al., 2012); (3) emplacement of some of the
dolerite dykes of the Korosten plutonic complex (Shumlyanskyy and Mazur,
2010). Beside these, zircons of the similar age were revealed in various
metamorphic rocks. For instance,
1779 ± 10
Ma zircons were found in amphibolite of the Novokryvorizhska suite (Stepanyuk
et al., 2011);
1747 ± 68
Ma zircons present in c. 2090 Ma migmatites of the North-Western region
of the Ukrainian shield while
1792,5 ± 8,5
Ma zircons were revealed in the Teteriv Series metasediments
metamorphosed at c. 2100 Ma.
These magmatic and metamorphic events coincide with collision (or
“docking”) of two segments of the East-European craton – Sarmatia
(already joined with Volgo-Uralia) and Fennoscandia (Bogdanova et al.,
2006; Elming et al., 2010). Supposedly, collision-related processes
(post-collision extension caused by rotation of Sarmatia) led to
destabilization of lithosphere, mantle melting and moderate
metamorphism.
Numerous and widely varying in composition (including kimberlite) mafic
dykes are abundant in the Kirovograd block; these emplaced probably at
the same time. The same can be said about ultramafic alkaline rocks of
the Gorodnytsya Complex present in the North-Western region of the
Ukrainian shield.
Post-collision magmatism of the Ukrainian shield embraces wide range of
the rocks: (1) dykes of subalkaline dolerites and various plutonic rocks
of the Korosten complex, including gabbro, anorthosite and granite; (2)
numerous dykes of Ni-bearing dolerite and layered massifs of the
Prutivka-Kamenka complex; (3) rather rare dykes of subalkaline olivine
gabbro of the Strybizh complex; (4) alkaline ultramafic rocks of the
Gorodnytsya complex; (5) numerous dykes of the Kirovograd block. All
these rocks are related to the same process – collision of Sarmatia and
Fennoscandia and destabilization of lithosphere.
Geochemical and isotope data indicate formation of the initial melts for
these rocks from different sources located at various depths, and
variably contaminated by the crustal material. Depth of the source of
melting gradually increases in the mentioned above sequence while degree
of melting decreases.
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the Korosten complex,
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V., Gintov O.
B., Kurlovich D.,
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V., Nilsson M.,
Orlyuk M.
I., Pashkevich I.
K., Shumlyanskyy L.
V., Starostenko
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caused by rotations during the assembly of supercontinent Columbia.
Submitted to Lithos
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Kozlovskaya, E., Motuza, G., Skridlaite, G., Starostenko, V., Taran, L.,
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Elming S.-Å., Shumlyanskyy L., Kravchenko S., Layer P., Söderlund U.
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Shumlyanskyy L., Billström K., Hawkesworth C., Elming S.-Å. U-Pb age and
Hf isotope compositions of zircons from the north-western region of the
Ukrainian shield: mantle melting in response to post-collision
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geochemistry of the rhyolites of the Ovruch depression. Mineral.
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