Rb-Sr and K-Ar age of globular phyllosilicates and biostratigraphy of the Riphean deposits of the Olenek Uplift (North Siberia)

This work presents results of the complex mineralogical, geochemical, and isotope-geochronological investigation of globular dioctahedral 2: 1 phyllosilicates (GPS) of the illite–glauconite series from the Riphean sequences of the Olenek Uplift. It is established that GPS (glauconite, Al-glauconite, Fe-illite) in deposits of the Arymass, Debengda, and Khaipakh formations are represented by mixed-layer varieties of two types: (1) with relatively low (<10%) and (2) higher (10–20%) contents of expandable layers. Among the mixed-layer varieties are those with disordered alternation of micaceous and smectite layers (R = 0), as well as with tendency to ordering (R ≥ 1). The parameter b of an elementary cell of minerals varies from 9.18 to 9.72 Å. The Rb–Sr age dating of GPS was first carried out in combination with the calculation of theoretical pattern of the cation distribution in the mineral structure and comparison of the calculation results obtained with the Mössbauer and IR spectroscopy data. This approach is based on the assumption that development and evolution of isotope systems in GPS are synchronous with the evolution of the crystalline structure of the mineral at various stages of the geological and geochemical history of the development of sedimentary units. Analysis of the obtained data allows us to state that the structural features of the Riphean GPS from the Olenek section reflect the early diagenetic stages of the formation of the minerals studied. The 87Sr/86Sr initial ratios in the studied sediments are consistent with the range of variations in this ratio in the Middle Riphean Ocean (0.7049–0.7061). The Rb–Sr and K–Ar ages of the GPS of the Arymass (1305 ± 8 and 1302 Ma, respectively), Debengda (1265 ± 12 and 1284 ± 22 Ma), and Khaipakh (1172 ± 18 and 1112 ± 24 Ma) formations in the Olenek Uplift section are close to the accumulation time of corresponding deposits and, correspondingly, have significance for stratigraphic correlations.     

Hydrochemical and microbiological characteristics of bog ecosystems on the isthmus of Svyatoi Nos Peninsula (Lake Baikal)

Presented are the results from hydrochemical and microbiological investigations into Arangatui bog ecosystems on the isthmus of Svyatoi Nos Peninsula on the shores of Lake Baikal. The formation features of bog waters as a result of a rise in the lake’s water level.     

Mineral composition of soils and bottom sediments in bays of Novaya Zemlya

We have analyzed the specific features of the mineralogical composition of bottom sediments of Blagopoluchiya, Tsivol’ki, and Abrosimov bays and soils on Cape Zhelaniya and the coasts of Abrosimov and Stepovoi bays. The data were obtained during two scientific expeditions of the R/V Professor Shtokman in 2014 (cruise 128) and R/V Akademik Mstislav Keldysh in 2015 (cruise 63). These investigations revealed patterns in the transportation of terrigenous material in the coastal zone of the bays: a decrease in the share of nonclay minerals and an increase in that of clay minerals with distance from shore. The increase in kaolinite and smectite content in soil horizons is related to biochemical weathering, while illite is mainly formed as a result of physical weathering.

     

Structural and Crystal-Chemical Features and Rb–Sr Age of Globular Glauconite in the Ust-Il’ya Formation (Lower Riphean,Anabar Uplift)

Lithology and Mineral Resources - For the first time, mineralogical, structural, crystal-chemical and isotope-geochronological data were obtained for a glauconite sample from the Lower Riphean...     

Mineralogical,Crystal-Chemical,and Rb–Sr Isotope Data on Terrigenous Globular Phyllosilicates of the Maastakh Formation (Lower Vendian,Olenek Uplift)

Lithology and Mineral Resources - The mineralogical, structural, crystal-chemical, and isotope-geochronological data were obtained for the first time in two samples of globular phyllosilicates...