Vol 54, No 6 (2016)

The mercury content is studied in fish from the European Russian lakes and rivers. The results revealed significant accumulation of mercury in fish as the uppermost trophic level of aquatic ecosystems even at extremely low (<10 ng/L) content of this element in water. The maximum accumulation was found in the predatory fishes from Middle and Lower Volga, Severnaya Dvina, and small lakes subjected to anthropogenic air pollution. The influence of temperature and geochemical factors on the penetrative ability of mercury in a fish organism is considered.

The results of ICP-MS trace-element (LILE, HFSE, REE) study of the Late Mesozoic–Early Cenozoic volcanic rocks of the Okhotsk and Japan seas and geochronological K-Ar dating of the Eocene volcanic rocks are presented. Specifics of volcanism developed on submarine rises of these seas was characterized for the first time, and magma sources and geodynamic settings of the volcanic complexes predating the formation of the deep-water basins were determined. It is established that the Late Mesozoic magmas were formed in a subduction setting from spinel peridotites of suprasubduction mantle wedge, which was metasomatically reworked by aqueous fluids that were released by dehydration of sedimentary layer of subducting oceanic plate. This follows from the elevated concentrations of H₂O, alkalis, potassium, LILE and LREE, and lowered HFSE (including Ta-Nb minimum) and HREE contents, at lowered Sm/Yb, Nb/Ta, Nb/Y and elevated La/Nb, Ba/La, and Zr/Y ratios. Eocene adakite-like volcanic rocks were identified for the first time in the Sea of Okhotsk. They vary from andesitic to more felsic compositions with elevated MgO (>4%) and elevated La/Yb (>14) and Sr/Y (50–60) ratios. Identification of adakite-like volcanic rocks serves as evidence in support of the transform continental-margin (or plate sliding) setting, which is characterized by breaking apart of subduction slab and formation of slab “windows” acting as pathways for the transfer of asthenospheric mantle into continental lithosphere. New geochemical data on the Late Mesozoic–Early Cenozoic volcanic rocks of the Okhotsk and Japan seas and analysis of literature data were used to distinguish two geodynamic settings within these seas: subduction and transform margin. Similar settings operated at that time in the adjacent continental- margin volcanic belts (Akinin and Miller, 2011; Martynov and Khanchuk, 2013; et al.).

We present the results of a comparative study of the geochemical changes of amphibolites and gneisses from the Belomorian mobile belt in response to plagiomigmatization, high-pressure metamorphism, two-feldspar migmatization, and secondary amphibolization during Paleoproterozoic (Svecofennian) tectonometamorphic activation. It is established that most of the Paleoproterozoic metamorphic processes are nonisochemical for major and trace elements, which is possibly caused by the interaction of protolithic rocks with metamorphic fluids. The finds of eclogites within the Belomorian mobile belt are spatially and genetically related to the large fields of apoamphibolite and apogneiss plagiomigmatites. Apoamphibolite eclogites, Grt–Aug eclogite-like rocks, apoamphibolite and apogneiss plagiomigmatites were formed by a single process initiated by the influence of an alkaline fluid on the amphibolite–gneiss complex. This was accompanied by the depletion of the rocks in HREE, enrichment in LREE, disappearance of the negative and formation of the positive europium anomaly. The formation of later two-feldspar migmatites was related to the reworking of the gneiss–migmatite–amphibolite complex by more acid fluids, which led to the depletion of microclinized rocks in LREE. Secondary amphibolization and epidotization of the basites and metabasites did not affect their REE distribution pattern.

The purpose of the study is to present the geothermal model of Mersin (Camili) region geothermal area with its geology, hydrogeology, hydrogeochemistry and isotope hydrology. The 1/25000 scale geology map obtained from the literature research is revised. In order to obtain a geothermal model, geological crosssections are extracted in certain points on the revised geology map. There are 3 hot water outlets. There are MC-1, C-1 and Uclu Cesme deep drillings. MC-1 well is 420 m, approximately 43.6°C temperature and 35 L/s flow rate and C-1 is 150 m, 40.3°C and 35 L/s. There is no exact information about the depth of Uclu Cesme well, but its average temperature is 37.5°C and it has a very low flow rate. Isotope analyses of the water samples obtained from these three wells and the Icme Dere are carried out by using the IRMS method with δ¹⁸O–δ²H (Deuterium) and IAEA method with ³H (Tritium). Radioactive Alpha-Beta determination and Physico-chemical and Bacteriological analyses of MC-1 well are made by using EPA 900.00. δ¹⁸O–δ²H isotope ratios clearly indicate a meteoric origin for the waters. In the light of all this information, the revised 1/25000 scare geology map of Mersin Guneyyolu (Camili) geothermal area is obtained; it is found out that hot waters are of meteoric origin; and the isotope hydrology and hydro-chemical assessment of the area is conducted to shape the geothermal model.