Agate mineralization in effusives of Suysar complex located in Central Karelia

The paper is concerned with the results of mineralogical and geochemical study of agates from pillow lavas of the Suysar volcanic complex (Central Karelia, Onega Lake Pin’guba). The results were obtained by the complex of modern research methods: optical and electron microscopy, electron microprobe, X-ray diffraction analysis, Raman spectroscopy, mass spectrometry with inductively coupled plasma. It is shown that the main role in the agates’ structure is executed by the silica minerals: quartz and fine-grained fibrous chalcedony, the individual layers are actively pigmented with chlorite and iron oxides. Coarse-crystalline calcite, microinclusions of epidote, pyrite, titanite, albite are typical of agate. The carried out research has shown that the contrasting rhythms’ presence within agate is marked not only by the change in the alloy composition of mineral phases and their morphology, but also by different concentrations of trace elements. This phenomenon may be conditioned by the heterogeneity of the feed solution, in which “chemical exhaustion” effect, demonstrating dependence upon circulation duration, was observed.