Institute of Geology, Karelian Research Center, Russian Academy of Sciences, Petrozavodsk, Russia:

O. V. Myasnikova, Researcher, Candidate of Engineering Sciences, okmyasn@krc.karelia.ru
A. V. Pervunina, Senior Researcher, Candidate of Geologo-Mineralogical Sciences

Aiming to expand minerals and raw materials base in the Republic of Karelia, deposits of low-carbon schungite-bearing rocks are discussed from the viewpoint of application in construction industry. These rocks are mostly developed within the Onega Paleo-Proterozoic structure inside the Ludicovian (1920–2100 million years) and Kalevian (1800–1920 million years) upper horizons in the south-east of the Fenno-Scandinavian Shield. The basic low-carbon schungite-bearing rocks in Karelia are argillite, siltstone, sandstone and lyddite. Schungite content of rocks ranges as 0.1–5%. Schungite is a metamorphosed Proterozoic organic substance at meta-anthracite stage of carbonization. Most often schungite occurs in rocks as a uniform dissemination from 1 to 10 μm in size. Schungite content is maximum in lyddite and minimum in sandstone. This study analyzes two types of low-carbon schungite bearing rocks—sandstone and siltstone—from four deposits. The mineral and chemical compositions of rocks are studied by the methods of electron microscopy and X-ray fluorescent spectrometry. The mineralogical and lithochemical singularities are revealed, and the petrophysical properties which govern processing and application trends are determined. In terms of the Nigozero and Myagrozero deposits, detailed laboratory experiments are carried out. Quality of the nonmetallic minerals is evaluated. The studies of physical and mechanical properties of rocks and gravel fractions are presented; applicability of gravel in production of construction materials is considered. In siltstone areas of the deposits, it is recommended to cut rocks into slabs for external and internal lining of building, and for other architectural and constructional works.

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