Sediments of northeastern shelf of the sea of Okhotsk in the area of South Kirin hydrocarbon deposits: microstructure, mineral, chemical and trace element composition

• Published in: Proceedings of higher educational establishments. Geology and Exploration
• Main Authors: T. G. Ryashchenko, S. I. Shtel'makh, N. N. Ukhova, G. S. Lonshakov, S. S. Kolesnikov
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Sergo Ordzhonikidze Russian State University for Geological Prospecting 2019
• Subjects: охотское море; шельф; осадки; микроструктура; минеральный состав; химический состав; микроэлементы; показатель загрязнения; коэффициент концентрации; Geology; QE1-996.5; Okhotsk; Sakhalin
• Online Access: https://doi.org/10.32454/0016-7762-2019-3-21-31; https://doaj.org/article/658f3af582f3499e9186b6e07b88ed32

The study results of the microstructure, mineral, chemical and trace element composition of the northeastern shelf sediments in the area of the South Kirin hydrocarbon deposits of the Sea of Okhotsk in the Sakhalin region are considered. Sediment samples were taken during well drilling from the «Trias» special vessel at the depth of 25—30 m from the bottom surface (by the sea depth of 200—220 m). Interval coring (every one meter) was carried out by the pressing-in method. Analytical studies were performed for 30 air-dry samples (firmly cemented cylinders with a diameter of 4 cm, a height of 3 cm, and a weight of 50—70 g) of well No. 49 (30 m). According to lithological characteristics, three intervals are distinguished in the section which are represented by clay sands (0,0—4,0 m), sandy, silty clays (4,0—21,0) and clays (21,0—30,0). REM images of the sediment microstructure were obtained using a scanning microscope JEOL JIB-Z4500 (xlOOO-6000) for each interval. The scientific imaging was performed for ten thin undisturbed plates from the top part of air-dry sample-cylinder. Fauna residues and micropores were found. The content of aggregates, primary (free) particles and the volume of real clay content were determined by the «Microstructure» method. On the basis of these data, grouping of samples was carried out using the Q-type cluster analysis program which confirmed the picked intervals in the studied section. Changes in the mineral composition were determined by powder diffraction in the sediment thickness. The quartz content decreases with depth, and the clay phase increases in which hydromica dominates, and the almost complete absence of kaolinite is noted. The content of rock-forming oxides (method of silicate analysis) and statistical data processing showed a homogeneous distribution of silicon, aluminum and potassium oxides in the section, the coefficient of variation (V, %) was only 1—3 %. Augmentation of variability was found for БегОз (P12). Values of geochemical coefficients and statistical data ...