Biophilic microelements and carbon in the silty-pelitic sediments of mud volcanoes in the Northwestern Caucasus

Abstract

Relevance. Mud volcanism is of great interest to specialists in various fields. Its research is important for assessing energy resources, analyzing seismicity, forecasting the content of greenhouse gases in the atmosphere, including refinement the global methane balance. At the same time, research in the field of inorganic geochemistry of products of mud volcanism, as well as work aimed at studying the relationship of trace elements, including biophilic (Cu, Co, Zn, V, Ni, Mo, etc.), elements of silty-pelitic sediments with total (Сtot), carbonate (Сcarb) and organic (Сorg) carbon is still insufficient. Aim. This paper is intended to fill this gap to some extent based on the analysis of data on the content of a wide range of elements, as well as Ctot and Corg, in the silty-pelitic sediments of a number of mud volcanoes in the Northwestern Caucasus (Akhtanizovsky, Semigorsky, Gladkovsky, Shugo, Miska, Shkol’ny and Hephaestus). Methods. The determination of the content of biophilic elements was carried out using the ICP-MS method. Analysis of the Ctot and Corg content was carried out using infrared spectroscopy on a METAVAC CS-30 device. Statistical data processing included comparison of the content of the trace elements with their content in Post-Archaean Average Australian Shale (PAAS) and Maikopian clays, correlation analysis based on Spearman pair correlation coefficients and Principal Component Analysis (PCA). Results. The average content of biophilic elements, with the exception of Sr, was found to range from 50 to 90% of their content in such a reference object as PAAS. The average Corg content varies in samples from 0,41 to 1,49 wt %. A statistically significant relationship is observed between the concentrations of some biophilic elements and Corg in the silty-pelitic sediments of mud volcanoes. This suggests that the biophilic elements in the silty-pelitic sediments of the mud volcanoes listed above are quite strongly associated with organic matter. Analysis of the relationships between trace elements, Corg and Ccarb using the PCA showed that the first two principal components accounted for 58,8% of the total variance. Ccarb has a positive loading on PC1, while Corg has negative loadings. The identified factors may reflect both the composition of the sources and indicate the some extraction of the several elements during changes in the host rocks in the mud volcanic process.