VOLUME 50 (3)/December 2021

The liquid limit is one of the most commonly used index properties of soils. The paper compares liquid limit values determined by the Vasiliev cone penetrometer method and by the Casagrande cup method, based on 45 natural clay samples collected from the Kozloduy Town area (North Bulgaria). An empirical correlation based on these liquid limit results has been derived.

The main objective of this study is to present the distribution of different chemical elements in soil samples from the Mariovo region, North Macedonia. To determine the level of presence of chemical elements, soil samples were collected from a total of 33 locations in a 5×5 km area. From each location, two samples of soil were collected: topsoil (0–5 cm) and bottom soil (20–30 cm). The analyses of soil samples were used to assess the prevalence of the chemical elements and the presence of heavy metals in the studied area. The analysis was carried out, using two instrumental methods: atomic emission spectrometry with inductively coupled plasma (ICP-AES) for macro-elements, and mass spectrometry with inductively coupled plasma (ICP-MS) for trace elements. A factor analysis was applied to reveal the relationships between the investigated variables (chemical elements). From the obtained results, spatial distribution maps of factors for the separate groups were prepared, as well as distribution maps for the analyzed elements. It was found that the distributions of most elements follow the lithology of the examined area. Factor analysis revealed the relationships between the investigated variables and could provide dimensionality reduction based on them.

The epithermal high-sulphidation Cu-Au Chelopech deposit is characterized by a well-developed and well-traceable hydrothermal footprint manifested in the volcanic host rocks. The economic ore mineralization is embedded in the strong silicification, included among the advanced argillic zone of alteration, smoothly transitioning to quartz-sericite alteration that evolves into widespread propylitics. The quartz-sericite alteration zone is accessible for exploration only in underground mining galleries and exploration drillings. The main mineral assemblage in this zone is quartz, sericite, pyrite, minor rutile/anatase and relics of apatite and feldspar. According to XRD data from the studied samples, sericite was defined as illite and muscovite/sericite 2M₁ polytype. The abundance of heavy stable isotopes (D, ¹⁸O) in the structural water of two sericite samples is the object of this study. A special attention was paid to the separation of extraneous waters from the structural one by thermal fractionation. The extracted structural water was converted to hydrogen and carbon dioxide before the isotopic measurements. The obtained results, put into a δD vs. δ¹⁸O plot, indicate that sericite structural water is “heavier” than meteoric water, within uncertainty limits.