Geochemistry and U-Pb age of zircon from the platinum-bearing Vurrehuayvench massif. Monchegorsk complex. Kola Region
Rundkvist T. V., Balashov Yu. A., Skublov S. G., Pripachkin P. V., Grebnev R. A.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 3. P. 14-30
The paper displays data on geochemical and geochronological characteristics of zircons from mafic rocks of a part of Monchegorsk layered complex — Vurechuayvench massif. Ages of zircons (SHRIMP-II) in samples B-l-09 (anorthosites) and B-2-09 (gabbronorites) are dated as 2508 ± 7 and 2504 ± 8 Ma, respectively. Character of REE patterns normalized to chondrite confirms magmatic nature of these zircons. These data indicate clearly that the resulting U-Pb zircon age, as in gabbronorites so in anorthosites, — is the age of melt crystallization in magmatic chamber. Mantle origin of gabbroic rocks of the Vurechuayvench massif is confirmed by the nature of REE distribution spectra for zircons, including three their generations with different consequence of crystallization. The wide range of the Ce/Ce* ratio variations (9.96—105.24) has been revealed also for zircons from gabbroic rocks of the Vurechuavench massif; it corresponds to sharply oxidative conditions of the zircon crystallization. For deep mantle rocks, these data may be explained only by a significant contamination of melt with the wall rocks material.
Key words: Kola region, Monchegorsk layered complex, Vurechuayvench massif, zircon, geochemistry, U-Pb age, crystallization conditions, REE.