Physical and chemical methods of researching rocks and minerals in the Analytical Centre of the Institute of the Earth's Crust, SB RAS

In the studied region, vast land areas are influenced by construction and operation of large linear facilities, such as oil-gas pipelines, power lines, motor roads and railways. In the areas along and inside the construction rightof-way zones, considerable changes occur in landscapes, microclimate conditions, hydrological features of water bodies, and geological engineering characteristics of the rocks. Furthermore, anthropogenic soil materials are produced. In our study, such materials are termed 'man-made / technogenic soils', which means the soil material displaced during stripping operations in the areas allocated for construction of linear objects, and the soil material resulting from coal mining and quarrying. The above-mentioned changes in the geological environment lead to intensive exogenous geodynamic processes (EGP) taking place during construction and in the first years of the object operation. In areas where such objects are located near and in residential areas, the EGP impact is observed in the zones that have been previously not at all influenced or only slightly affected by EGP. In our comprehensive study aimed at the assessment of the scale of the regional landslide and mudflow processes, the physical and chemical properties of technogenic soils were determined, their mineral and chemical composition was analyzed, and the levels of chemical contamination of the studied soils were estimated. The research results can be used in engineering-geological, construction, hydrometeorological surveys, as well as forecasting the development of EGP and their impact on the territory adjacent to the large linear objects.

Section: методика исследованийunclassified

Intensification of exogenous geodynamic processes in areas with large linear objects, associated with changes in the characteristics of soils displaced by construction and operation activities

Генсиоровский

Ухова

Shtel’makh

et al. 2019

“…Царева, Г.В. Бондарева) по методике [Revenko, 2014]. Содержания редких и редкоземельных элементов определены методом ICP-MS в Лимнологическом институте СО РАН, ОПЦКП «Ультрамикроанализ», на квадрупольном масс-спектрометре Agilent 7500ce (Agilent Technologies Inc., США) (аналитик С.В.…”

Section: методы исследованийunclassified

U-Pb (LA-ICP-MS) age of detrital zircons and the sources of terrigenous sediments of the Ipsit suite, Karagass series (Sayan segment of the Sayan-Baikal-Patom belt)

Motova

Донская

Гладкочуб

et al. 2018

The petrographic, lithogeochemical and U-Pb (LA-ICP-MS) geochronological studies were carried out to investigate the terrigenous rocks sampled from the lower part of the Ipsit suite of the Karagass series (Sayan segment of the Sayan-Baikal-Patom belt). These rocks include sandstones, aleurite sandstones and aleurolites, and their mineral compositions are close to that of arkose. Most of the studied rock samples show petrographic features typical of the epigenetic changes at the stage of catagenesis: regeneration of quartz clastic grains, pelitization of potassium-feldspar clastic grains, occurrence of clay-hydromica aggregate, sericitization of plagioclase, chloritization of biotite, and silicification of dolomite pieces, and occurrence of authigenous tourmaline. The above was confirmed by the analysis of the concentrations of petrogenic elements in the studied rocks from the lower part of the Ipsit suite. The analysis results show that the concentrations of K2O are elevated, while the concentrations of Na2O are relatively very low, which may be due to the redistribution of these elements during epigenetic transformations. According to the classification by genetic types on the basis of the system of petrochemical modules, the rocks of the lower part of the Ipsa suite are of the petrogenic nature. The acidic igneous rocks are dominant in the source area, as evidenced by the presence of granitoid and quartzite fragments in the clastogenic component, as well as the set of accessory minerals typical of the igneous rocks of the acidic composition, and the distribution pattern of rare and trace elements. According to the U-Pb (LA-ICP-MS) dating of detrital zircons from the aleurite sandstone sampled from the lower part of the Ipsit suite, the zircons are exclusively of the Archean-Early Proterozoic ages. Such ages correlate with the age of the granitoids of the Sayan complex and the felsic volcanites from the Maltsev layer of the Elash series (Biryusa block). Furthermore, the detrital-zircon age spectra of the aleurite sandstone of the lower part of the Ipsit suite are identical to the detrital-zircon age spectra of the terrigenous rocks from the underlying strata of the Shangulezh and Tagul suites of the Karagass series. This study suggests that sedimentation of the Ipsit suite of the Karagass series took place due to the influx of detrital material from the southern part of the Siberian craton into the sedimentation basin, and the acidic igneous rocks of the Biryusa block were one of the main sources of detrital material.

“…Определение основных петрогенных оксидов проведено методом силикат-ного анализа по методике [Revenko, 2014] (анали-тики Н.Н. Ухова, Н.Ю.…”

Section: литогеохимическая характеристикаunclassified

The Composition and Reconstruction of the Source Area for the Late Precambrian Terrigenous Rocks of the Oselkovaya Series (Biryusa Prisayanie)

Motova¹,

Донская²,

Гладкочуб³

2016

Abstract:We present results from petrographic and lithogeochemical studies of the Late Precambrian terrigenous rocks (sandstones, gravelites, and aleuritic sandstones) from the Oselkovaya series of Prisayanie. The studies were conducted to reconstruct the primary composition of the rocks in the source area. It has been found that the rocks in the lower part of the cross-section of this series (Marninskaya suite, and the lower part of the Udinskaya suites) are represented by more coarse-grained terrigenous rocks (gravelites, and sandstones) as compared to the upper part of the cross-section (the upper part of the Udinskaya suite, and the Aisinskaya suite) with sandstones and aleuritic sandstones. Gravelites and sandstones from the lower part of the Oselkovaya series show indicators of epigenetic changes that are less intensively expressed in the rocks from the upper part of the cross-section. The upper and lower parts of the Oselkovaya series are significantly different in terms of lithogeochemistry. The lower rocks show quite low contents of Na2O and ratios K2O/Na2O ranging between 10 and 75. In the terrigenous sediments of the upper part, values of K2O/Na2O do not exceed 1-2. Sandstones and gravelites in the lower part of the Oselkovaya series are characterized by reduced concentrations of radioactive, rare-earth, and highly charged elements, as well as lower concentrations of Ni and Co relative to concentrations of these elements in sandstones and aleuritic sandstones of the Oselkovaya series. The petrographic and lithogeochemical characteristics of the terrigenous sediments of the lower and upper parts of the Oselkovaya series suggest different sources of the denudation of these rocks into the sedimentation basin. It is suggested that acid rocks were the denudation source of the terrigenous rocks in the lower part of the series, and the sandstones and aleuritic sandstones in the upper part of the series were sourced from rocks of a mixed (acid-base) composition. The composition of the rocks in the source area was reconstructed, and the published ages of detrital zircons from the sandstones of the upper and lower parts of the Oselkovaya series were taken into account. The reconstruction suggests that the lower part of the Oselkovaya series resulted from the destruction of the basement rocks in the Siberian craton. The upper part of the Oselkovaya series seems to have formed in the basin, wherein the denudation took place from the orogen formed as a result of the accretion of micro-continents and island arcs of the Paleo-Asian Ocean to the south-western margin of the Siberian craton.