Home – Home – Jornals – Russian Geology and Geophysics 2018 number Неопубликованное

The gas composition of bottom sediments of the Laptev-Siberian geostructural zone (LSZ) was determined to include: helium and hydrogen in concentrations of 0.0028–0.2092 and 0.0012–0.8727 cm³/kg, hydrogen sulfide – 0.0006–0.0072, carbon monoxide – 0.0016–0.0577, carbon dioxide – 0.1482–21.1602, methane – 0.0017–8.3047 and its homologues (in total) – 0.00001–0.0355 cm³/kg. It was found that the values of average concentrations of gases in bottom sediments increase with the depth of their occurrence and exceed the anomaly criteria established for the East Arctic shelf by 2.6–27.7 times, including: CO₂, CO and H₂S – by 2.6, 3.0 and 3.4 times; ΣC₂-C₅ and He – by 9.3 and 10.8 times; CH₄ – by 27.7 times, which actually indicates a high degree of gas saturation of the bottom sediments of the region. The formation of CO₂, CO, H₂S, H₂, CH₄ and ΣC₂-C₅ anomalies in the sediments of the upper and the base of the middle sampling horizon is determined by relatively high contents of sapropelic and humic organic matter and gas influx from the lower horizon. Distribution of anomalies with maximum concentrations of natural gases and He in sediments of the lower horizon, with minimum contents of C_org, is associated with zones of faults, large disturbances, tectonomagmatic and seismic activity, which are the main routes of diffusion-migration of gas transfer to bottom sediments. Formation of concentrations of gases and their anomalies in sediments of the LSZ obeys the rules of additivity, that is, successive accumulation of migration natural gases of different genesis with prevalence of gas phase and isotopic indicators of more gas-saturated epigenetic and syngenetic sediments of the parent source. It was established that maximum values of average gas saturation of CH₄, ΣС₂-С₅, He and H₂ in the LSZ are characteristic of bottom sediments of the wings of troughs, CO and CO₂ - of the arch parts of uplifts. In the sediments of monoclinal folds (structural terraces), minimal values of average gas saturation are observed, with the exception of the South Anyui fault zone. In general, the gas saturation of the LSZ sediments is determined by the complex impact of geological factors, the main ones being: gas content of rock complexes and gas saturation of underlying sediments, fault and fold tectonics, a high degree of tectonomagmatic and seismic activity, geostructural position, coal content, oil and gas content, as well as the depth of occurrence, organic saturation and material composition of organic matter in bottom sediments. The influence of the latter predetermined the formation and distribution of five geochemical fields of CH₄, three of CO, ΣС₂-С₅, He and one each of CO₂ and H₂ in the LSZ area.