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This paper presents an integrated major and trace element data and crystal size distribution analysis for zoned clinopyroxene phenocrysts hosted in variolitic and massive picrobasalts of the Suisaari Formation, Karelian Craton, Eastern Fennoscandian Shield. Clinopyroxenes in variolitic and massive lavas occur as unzoned, reverse, and normally zoned crystal. Oscillatory-zoned clinopyroxenes are only observed in variolitic lavas. The obtained data were examined in order to evaluate the contribution of magmatic processes such as magma mixing, contamination and fractional crystallization to the formation of various zoning patterns of clinopyroxene phenocrysts. Clinopyroxene phenocrysts in both variolitic and massive lavas originate from similar primary melts from a single magmatic source. The obtained data on composition and texture of clinopyroxene phenocrysts together with the crystal size distribution (CSD) analysis suggest that crystallization of the massive lavas mainly involves fractionation in a closed magmatic system, whereas the crystallization of the variolitic lavas is determined by processes in an open magmatic system. The results provide novel information on the evolution of Paleoproterozoic magmatic systems in the Karelian Craton.

Raman spectroscopy together with the scanning electron microscopy and X‐ray diffraction were applied to study the firing parameters (temperature and atmosphere) of medieval pottery from Karelian hill forts in the North‐Western Ladoga region (Russia). Because the evidences of pottery manufacture including firing facilities were not discovered during the excavations of medieval Karelian fortresses, the application of Raman spectroscopy combined with the other techniques appeared to be an effective approach to reconstruct the technology of ceramic production in medieval Karelia. Scanning electron microscopy ‐energy‐dispersive X‐ray spectroscopy and X‐ray diffraction analysis showed that the Karelian pottery refers to noncalcareous and low‐temperature fired ceramics. Using the thermometer based on the thermal evolution of Raman spectral parameters of the charcoal identified in the ceramic paste of some specimens, the firing temperature for those was estimated to be close to 800 °C. These data are in accordance with the more frequent occurrence of anatase rather than rutile in the studied ceramic sherds that also corresponds to low firing temperature. The presence of hematite suggests firing in oxidizing atmosphere, in rare case the detected magnetite indicated the incomplete oxidizing atmosphere. The reconstruction of Karelian pottery firing procedure based on the obtained data supposes that the firing was carried out in bonfires. The present study contributes to the deciphering the firing conditions for noncalcareous and low‐temperature burnt ceramics, for which no significant modifications of starting minerals during heating are usually observed.

Raman spectroscopy has proven to be a useful tool for the study of carbonaceous material (CM). This method is used to distinguish various types of CM and to study the evolution of Raman spectra characteristics of CM during metamorphic transformations. In the present study, we applied the Raman spectroscopy and electron diffraction methods to investigate the evolution of structural ordering of CM of shungite rocks, Karelia (Russia), during weathering. The studies of the CM structure evolution during weathering are rare and ambiguous. The Raman spectra of weathered shungites are characterized by increase of FWHM‐D1, that is accompanied by the decrease of intensity‐based ratio R1 = ID/IG and the change of the intensity of the bands in second‐order region. The Raman spectral data indicate that weathering results in the alteration of both intralayer and interlayer ordering of shungites, but there are some peculiarities for the shungites subjected to the various types of weathering. The present study establishes that the Raman spectra characteristics of weathered shungites can be used as the indicators of weathering for CM from various carbon‐bearing rocks. Copyright © 2017 John Wiley & Sons, Ltd.

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