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Vol. 18 (2015 year), No. 2

Кunakkuzin Е. L., Bayanova Т. B., Nerovich L. I., Borisenko Е. S., Serov P. А., Elizarov D. V.
New Nd-Sr isotope-geochemical research of the paleoproterozoic PGE-bearing Monchetundra massif rocks (the Fennoscandian Shield)

This paper presents results of Nd-Sr research for mafic rocks from the PGE-bearing Monchetundra massif, the Main Ridge. According to the new isotopic data mafic rocks of the massif different in age are characterized by various isotopic and geochemical characteristics....

(in Russian, стр.11, fig. 5, tables. 3, ref 20, Adobe PDF, Adobe PDF 0 Kb)

Vol. 20 (2017 year), No. 1, DOI: 10.21443/1560-9278-2017-20-1/1

Kaulina T. V., Nerovich L. I., Bocharov V. N., Lyalina L. M., Il'chenko V. L., Kunakkuzin E. L., Kasatkin I. A.
Raman spectra of impact zircons in the Jarva-varaka layered massif (the Monchegorsk ore region, the Kola Peninsula)

Zircon crystals from granophyre norites of the Jarva-varaka massif of the Monchegorsk ore region (the Kola Peninsula) have been studied by means of back-scattered electron (BSE) imaging and Raman spectroscopy. The Jarva-varaka massif according to geological and geochemical data has been compared with the Sudbury structure, for which an impact origin is assumed. Zircon study is stipulated by zircon ability to keep signs of shock metamorphism even under granulite-facies conditions, thus it can be used for identification of ancient impact structures. BSE images reveal complicated internal texture – darker central domains (cores) and light rims without texture. Mineral inclusions in zircon are represented by sillimanite and plagioclase which indicates that the studied zircon grains were inherited from the host aluminous gneisses. Zircon crystals show variation of Raman spectra from the core of crystals with typical zircon Raman pattern to complete absence of spectral bands in the marginal parts and rims. Mineral inclusions in zircon rims also have no Raman spectra. Such patterns may be associated with the transformation of crystalline zircon (and mineral inclusions in it) to diaplectic glass under the influence of shock metamorphism, core domains were screened by rims and thus preserved their structure. The received data suggest the participation of the meteorite impact in the formation of the Jarva-varaka massif that requires further investigation.

(in Russian, стр.11, fig. 4, tables. 0, ref 28, Adobe PDF, Adobe PDF 0 Kb)

Vol. 29 (2026 year), No. 1, DOI: 10.21443/1560-9278-2026-29-1

Ilchenko V. L., Kaulina T. V., Nerovich L. I.
Petrophysical properties of rocks and ring morphology of the probable impact Yarva-Varaka structure (Monchegorsk ore area of the Kola Region)

The morphology and physical properties (density, longitudinal wave velocities, and elastic anisotropy) of rock samples collected from the surface of the J?rva-Varaka site within the boundaries of the proposed astrobleme have been studied. Morphological analysis allows us to define the J?rva-Varaka structure as a multi-ring elliptical structure with a maximum diameter of approximately 10 km. The ring topography, although not reflecting the primary crater morphology, is associated with selective erosion caused by the concentric tilting of rock strata as a result of the meteorite impact. The largest variations in the physical properties of gneisses and granitoids are observed between the 2nd and 3rd rings of the structure. In most cases, a direct correlation is observed between density, longitudinal wave velocity, and anisotropy. Significant areal variations in the petrophysical properties of granitoids and gneisses, which represent the target rocks, have been established. Elastic anisotropy proved to be the most informative parameter. Within the ring structure, granitoids and gneisses exhibit increased anisotropy, while outside the ring, they often exhibit low to moderate anisotropy. Studying the petrophysical properties of the 2.5 Ga Jarva-Varaka astrobleme provides useful information that can be used in future searches and studies of ancient meteorite craters.

(in Russian, стр.11, fig. 4, tables. 1, ref 27, AdobePDF, AdobePDF 0 Kb)