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Russian Geology and Geophysics

2019 year, number 4

ZIRCONOLOGY OF THE LHERZOLITE BLOCK OF THE NURALI MASSIF (South Urals)

A.A. Krasnobaev1, A.I. Rusin1, P.M. Valizer2, I.I. Likhanov3
1Zavaritskii Institute of Geology and Geochemistry, Ural Branch, Russian Academy of Sciences, per. Pochtovyi 7, Yekaterinburg, 620075, Russia
2Ilmeny State Reserve
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Lherzolite, dunite, zircon, geochemistry, REE, Th and U, age, Nurali massif

Abstract

Data on the mineralogy, geochemistry, and geochronology of zircons from plagioclase and spinel lherzolite and dunites of the Nurali massif are presented. The age of the main-type zircons from lherzolites (plagioclase ones, 446.2 ± 2.8 Ma, and spinel ones, 433.3 ± 3.4 Ma) and dunites (443.8 ± 6.9 Ma) suggests their synchronous crystallization ( T av = 440 ± 5 Ma). The metamorphic age of zircons is 410-415 Ma. In addition to grains belonging to the main subset, the older grains with an age between 527 and 2045 Ma and newly formed metasomatic grains with an age of 380-385 Ma were found. The structure and REE patterns of most zircons from ultramafic rocks point to their magmatic origin, which is probably related to crystallization of a fluidized mantle melt.

DOI: 10.15372/RGG2019042