Journal
PETROLOGY
Volume 23, Issue 1, Pages 22-44Publisher
PLEIADES PUBLISHING INC
DOI: 10.1134/S0869591115010063
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Funding
- Russian Foundation for Basic Research [14-05-00920, 12-05-33069-mol-a-ved]
- Russian Federation [Mk-766.2013.5]
- Earth Science Division of the Russian Academy of Sciences
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Rhyolite-granite volcanoplutonic association was identified among the Precambrian basement complexes of the Aktau-Mointy Massif, Central Kazakhstan. This association comprises rhyodacites, rhyolites, subalkaline rhyolites, tuffs, and felsic volcanogenic-sedimentary rocks of the Altyn Syngan and Urkendeu formations, as well as granitoids of the Uzunzhal Complex. U-Pb (ID-TIMS) dating of accessory zircons from the volcanic rocks and granites showed that the association was formed in the Neoproterozoic (Tonian, 925-917 Ma). The Neoproterozoic volcanic rocks and granites are the youngest Precambrian magmatic complexes and mark the final stage in the formation of the Precambrian crust of the Aktau-Mointy Massif. In terms of major and trace element composition, the volcanic rocks and granites resemble A-type granites, thus indicating the within-plate settings of their formation. It was established that their primary magma could be derived by melting of metatonalitic or metagraywacke protolith at T a parts per thousand yen 940A degrees C and P similar to 8-10 kbar in response to mantle magma underplating. Sm-Nd isotope data on the volcanic rocks and granites (T-Nd(DM) = 1.9-1.7 Ma, E >(Nd)(T) from -1.9 to -3.5) testify the Paleoproterozoic age of their crustal protolith. Available data have revealed strong similarity between the Neoproterozoic tectonomagmatic evolution of the Aktau-Mointy Massif and the Congo-So Francisco paleocontinent, which, with other cratons, composed the southern Rodinia supercontinent. This suggests that the formation of the Tonian anorogenic volcanoplutonic association of the Aktau-Mointy sialic massif was related to the global-scale divergent processes in the southern Rodinia supercontinent (Congo-So Francisco paleocontinent).
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