Hasil untuk "Engineering geology. Rock mechanics. Soil mechanics. Underground construction"

SUN Zhoujing 1, YAN Liming 1, LI Wentao 1, 2 , WANG Jinghao 1, CHEN Yin 1

The traditional reactive magnesium oxide (MgO) carbonation technology is an emerging soil stabilization method. However, since this technique requires CO₂ to be introduced at specific concentrations and pressures, it is challenging to control in practical engineering applications, often leading to uneven solidification, especially for clayey soils. To address this issue, the sodium bicarbonate (NaHCO3) is used as a CO₂ carrier to treat the MgO-stabilized clay by an indirect carbonation method. The UCS, moisture content and XRD tests are conducted to investigate the effects of MgO and NaHCO3 ratios, curing age, temperature and acidic conditions on the mechanical properties and expansibility of clay reinforced by the indirect carbonation. The results indicate that the UCS initially increases and then decreases with the addition of NaHCO3, reaching its peak at an MgO: NaHCO3 ratio of 2:1. With extended curing time and elevated temperatures, the strength generally increases. In terms of strength and anti-expansion performance, the MgO: NaHCO3 ratio of 2:1 outperforms direct carbonation-stabilized soil. The XRD results show that the UCS of carbonated soil is mainly provided by hydromagnesite, or dypingite.

Kaistrenko, Victor M., Willis, Pascal, Razjigaeva, Nadezhda G. et al.

On October 4(5), 1994, one of the strongest tsunamigenic earthquakes in the history of the Southern Kuril Islands occurred, which was accompanied by large-scale tectonic manifestations. Intense shaking led to the collapse of the entire infrastructure on Shikotan and Kunashir Islands; 11 people died. The tsunami that followed the earthquake reached a height of about 10 m on the ocean side of Shikotan Island and was recorded along the entire coast of the Pacific Ocean. Generally, the study of the manifestations of this event had been carried out since October 1994 and ended in 1997 with the publication of extensive reviews. For the first time, the data on the specific effects on the ocean surface (seaquake) that accompanied this earthquake have been collected and systematized. In the following years, the interest in this extraordinary event initiated further research. At the same time, the study of the deposits of the tsunami of October 4(5), 1994, in the general context of study of ancient tsunami (paleotsunami) deposits in this region came to the fore. These studies allowed us to obtain estimates of the "preservation"/ "erasure" of the traces of this tsunami and more ancient events on the coast of the Southern Kuril Islands. Some important data presented in this review are being published for the first time.

ZHOU Yanguo 1, CAO Yuan 1, ISHIKAWA Akira 2, CHEN Yunmin 1

The soil-cement grid has been widely applied as an effective liquefaction countermeasure due to its capability to effectively mitigate the shear load and deformation of the enclosed soil under seismic loadings. In terms of its long service period, two dynamic centrifuge model tests are conducted to study the effects of strong shaking history on the liquefaction responses of the enclosed soil. The model ground consists of a 15 m-thick liquefiable clayey fine sand and an underlain 2.5 m-thick coarse sand layer. The liquefiable layer is improved by the soil-cement grid in one model, while the other without any improvement affording a contrast. Both models are subjected to a sinusoidal input motion with amplitude of 0.15g. Several more severe shaking events with amplitude of 0.4g are applied to the models prior to this 0.15g event as strong shaking history. The results imply that the damage patterns of the walls are mainly vertical penetrating cracks, partly accompanied by local diagonal cracks, and the outer cells show a "shielding effect" on the center cell similar to that of a group pile foundation. After the strong vibration history, the central cell of the soil-cement grid still has satisfactory anti-liquefaction effects, leading to a much lower excess pore pressure than free field. At the same time, due to the weakening of the overall stiffness of the soil-cement grid, the shear deformation between the soil-cement grid and the underlying coarse sand layer is significantly reduced.

Rui Wang, Chaosheng Tang, Xiaohua Pan et al.

This study proposed an improved bio-carbonation of reactive magnesia cement (RMC) method for dredged sludge stabilization using the urea pre-hydrolysis strategy. Based on unconfined compression strength (UCS), pickling-drainage, and scanning electron microscopy (SEM) tests, the effects of pre-hydrolysis duration (T), urease activity (UA) and curing age (CA) on the mechanical properties and microstructural characteristics of bio-carbonized samples were systematically investigated and analyzed. The results demonstrated that the proposed method could significantly enhance urea hydrolysis and RMC bio-carbonation to achieve efficient stabilization of dredged sludge with 80% high water content. A significant strength increment of up to about 1063.36 kPa was obtained for the bio-carbonized samples after just 7 d of curing, which was 2.64 times higher than that of the 28-day cured ordinary Portland cement-reinforced samples. Both elevated T and UA could notably increase urea utilization ratio and carbonate ion yield, but the resulting surge in supersaturation also affected the precipitation patterns of hydrated magnesia carbonates (HMCs), which weakened the cementation effect of HMCs on soil particles and further inhibited strength enhancement of bio-carbonized samples. The optimum formula was determined to be the case of T = 24 h and UA = 10 U/mL for dredged sludge stabilization. A 7-day CA was enough for bio-carbonized samples to obtain stable strength, albeit slightly affected by UA. The benefits of high efficiency and water stability presented the potential of this method in achieving dredged sludge stabilization and resource utilization. This investigation provides informative ideas and valuable insights on implementing advanced bio-geotechnical techniques to achieve efficient stabilization of soft soil, such as dredged sludge.

Siemaszko Paweł

This study highlights the possibility of determining the shear stress distribution along the skin of a pile, which represents skin resistance. Geotechnical engineering is plagued by the challenge of designing appropriate piles as a sufficient foundation construction while being economically justified solution. Static load testing facilitates verification if the pile satisfies these requirements. In most cases, the pile skin resistance is undervalued. This study first introduces the general approach based on static load test results using an appropriate mathematical approach in the presence of linear, vertical shear stress distribution boundary conditions as well as phenomena such as pile shortening and Kirchhoff's principle. Moreover, a scientific approach for pile compression and shear stress distribution is presented. Further, the study expands upon previous work by applying mathematical calculus to displacement piles. The promising results indicate that further work on greater number of piles may lead to a better understanding of pile–soil interaction and a more accurate design process.

Cuimei XIA, Nan WANG, Jingyu LIU et al.

Objective Black carbon is a carbonaceous mixture formed by the incomplete combustion of biomass and fossil fuels. Since black carbon has a high carbon content and an aromatized molecular structure, it can persist in the natural environment, suggesting that black carbon is an important component of the global carbon cycle. Although pioneering studies have advanced the understanding of nature, circulation fluxes, and reserves of black carbon in the geosphere, it is still necessary to further clarify the source-sink processes of black carbon and explore the importance of black carbon in the global carbon cycle. Methods Here, this study reviews the available data on pathways, fluxes, and time scales of the global black carbon cycle and analyses and summarizes the migration mechanisms and constraints in the source-sink process of marine black carbon. Results This paper concludes that marine sediments serve as a large reservoir for black carbon, with a reserve of 569-1 380 Pg. Black carbon can persist over millennia in marine sediments, which is associated with a long turnover time as an "effective carbon sink" in the context of "carbon neutrality". Moreover, black carbon exerts a negative feedback effect on global warming due to its longer turnover cycle time than biomass carbon. The deposition of black carbon into the sea is an effective means to enhance carbon sequestration in the ocean and could be an effective way to implement the carbon capture, utilization, and storage (CCUS) strategy. Conclusion In this paper, we propose that human-induced production of black carbon from biogenic combustion may be actively regulated and that the deposition pathways and burial areas of black carbon into the sea should also be optimized given the premise of ecological and environmental friendliness based on a summary and assessment of the strategic value and climate significance of black carbon in marine sediments in the context of "carbon neutrality". Therefore, the positive role of black carbon in "negative ocean carbon emissions" can provide a basic theoretical framework for achieving the goals of "carbon neutrality".

Yuanhua XIE, Guowei ZHANG, Zongwei CAO et al.

Objective Surface displacement and crack development are the most intuitive manifestations of landslide deformation and evolution. Therefore, revealing the characteristics and evolution stages of landslide deformation and failure through displacement monitoring and surface crack survey is highly practical. Methods In this study, the Baishuihe landslide in the Three Gorges Reservoir Area is selected as the research case, and monitoring data from 2003-2016 for this landslide are systematically collected and analyzed, taking monitoring points ZG93 and ZG118 as example. First, the fractal parameter Hurst index R/S analysis is carried out for the displacement data. Second, the multiple fractal dimensions of the displacement of the two monitoring points are calculated every year. Finally, the theory of stage matching of landslide cracks is introduced, and the crack fractal dimension of the Baishuihe landslide is determinated. Results The results show that there is a certain positive correlation between the landslide displacement sequences, and the fractal dimension H index of the two monitoring points is greater than 0.5. The evolution process of the Baishuihe landslide can be divided into a steady deformation state (from June 2003 to June 2007), an accelerated deformation state (from June 2007 to December 2009), and a steady deformation state (from December 2009 to December 2015). According to the matching law of crack stages, the development of the landslide is the initial deformation stage. Conclusion The research results have a certain guiding significance for revealing the evolutionary state of reservoir landslides.

زهرا شیخی آلمان آباد, حسین پیرخراطی

زمینه و هدف: به جهت وجود اهمیت کیفیت خاک در بستر حیات و محیط زیست، روش‌های ارزیابی مختلفی برای توصیف تأثیر آلاینده‌هایی همچون فلزات سنگین بر کیفیت خاک پیشنهاد شده‌اند. در این مطالعه ما با استفاده از مدل ریاضی، شاخص بهبود یافته وزنی به عنوان رویکردی نو، کیفیت خاک اطراف مجتمع سرب و روی زنجان واقع در شهرستان زنجان را مورد ارزیابی قرار داده و با نتایج حاصل از شاخص‌های آلودگی نمرو و شاخص بار آلودگی مورد مقایسه قرار دادیم.مواد و روش‌ها: در این مطالعه، نتایج حاصل از 71 ایستگاه نمونه‌‌‌برداری خاک اطراف مجتمع سرب و روی زنجان، واقع در شمال غربی ایران، توسط دستگاه اسپکترومتری نشری پلاسمای جفت شده القایی برای قرائت غلظت فلزات سنگین سرب، روی، آرسنیک، کادمیوم، تالیوم، باریم، آنتیموان، وانادیوم، کبالت، مولیبدن، نیکل و مس مورد استفاده قرار گرفت. همچنین مقدار اسیدیته خاک مورد آنالیز قرار گرفت. در این رویکرد، در طی محاسبه‌ی شاخص بهبود یافته وزنی، وزن‌ها با استفاده از ابزارهای آماری، از جمله تجزیه و تحلیل خوشه‌ای سلسله مراتبی و تحلیل مؤلفه‌های اصلی، به فلزات سنگین مختلف اختصاص داده شد. نتیجه‌ی حاصل از شاخص به صورت کمّی مقدار آلایندگی را مشخص می‌سازد.یافته‌ها: براساس شاخص بهبود یافته وزنی، 9/19 درصد نمونه‌ها در آلودگی متوسط و 2/4 درصد نمونه‌ها در آلودگی شدید، و سایر نمونه‌ها فاقد آلودگی و یا با آلودگی اندک بودند. برحسب شاخص بار آلودگی 8/5 درصد نمونه‌ها در آلودگی متوسط و 8/2 درصد در آلودگی شدید و شاخص آلودگی نمرو 9/19 درصد نمونه‌ها در آلودگی متوسط و 2/42 درصد در آلودگی شدید قرار دارند. مقایسه همبستگی نتایج حاصل از مدل با شاخص بهبود یافته وزنی با شاخص بار آلودگی، مقدار همبستگی 907/0 و با شاخص نمرو، مقدار همبستگی 701/0 می‌باشد که نشان دهنده‌ی نزدیکی بیشتر آن با شاخص بار آلودگی بود. نتایج شاخص بهبود یافته وزنی نشان داد که فلزات سنگین روی، سرب، کادمیوم و آرسنیک با منشأ انسان‌زاد و در نتیجه‌ فعالیت‌های صنعتی مجتمع سرب و روی زنجان نشان می‌دهد. در حالی که فلزات سنگین باریم، وانادیوم، تالیوم، مولیبدن، کبالت، مس، نیکل و آنتیموان دارای منشأ زمین زاد می‌باشند.نتیجه‌گیری: نتایج نشان داد که شاخص بهبود یافته وزنی با شاخص‌های قبلی تطابق خوبی داشته و می‌توان در محدوده‌های وسیع بکار برده شود. همچنین کاستی‌های شاخص‌های قبلی را برطرف نموده و به عنوان یک مدل جدید می‌تواند برای ارزیابی آلودگی خاک و خطر اکولوژیکی خاک مورد استفاده قرار گیرد. از این شاخص می‌توان در جهت شناسایی و تعیین منابع محتمل آلودگی استفاده نمود.

TANG Liansheng 1, 2, 3, 4, CHEN Yang 1, 3, 4, YE Yanghai 1, 3, 4, ZHOU Zixiao 1, 3, 4, CHENG Zihua1, 3, 4

The change of hydrochemical environment of granite residual soil will affect its physical and mechanical properties and microstructure. In order to explore the effects of immersion in Na2SO4 solution with different concentrations for 7 and 14 days on the physical and mechanical properties of the granite residual soil, the self-developed water and soil chemical cycle system is used to study the change rules of its resistivity, boundary moisture content, compressibility, shear strength, mineral composition and microstructure. The tests show that increasing the concentration of Na2SO4 solution can reduce its resistivity and limit moisture content. With the increase of the salt concentration, the compressibility of the granite residual soil increases first and then decreases after soaked for 7 days. When soaked for 14 days, the compressibility of the granite residual soil exhibits an overall upward trend. The shear strength, cohesion and internal friction angle first decrease and then increase with the increase of the salt concentration. After soaked for 14 days, the internal friction angle of the granite residual soil increases as the salt concentration increases. The SEM images show that the granite residual soil is in flocculation structure after soaked in Na2SO4 solution, and the soil particles are obviously coarsened. The research results may provide a certain reference value for the change laws of physical and mechanical properties of Na2SO4 solution after it affects the soil.

FAN Xu 1, 2, WANG Yongzhi 1, 2, LIANG Xiaocong 3, 4, CHEN Pingshan 3, 4, WANG Tiqiang 1, 2

Change of clogging and drainage performances of stone columns under many earthquakes is one of the focus issues in construction of artificial dredging island reef and port engineering. The dynamic centrifugal model tests on the composite foundation with stone columns in coral sand are carried out, and the change of clogging and drainage performances of stone columns is discussed through the image observation of the excavation profile of the stone columns, the grain-size distribution tests on the stone columns before and after earthquakes, and the change analysis of the dissipation rate of pore water pressure. The results show that liquefaction occurs at the buried point of 1.25 m, the pore pressure ratio reaches 1.0, and no liquefaction occurs at the buried point of 7.5 m under the seven times of intense dynamic loading. After the tests, no obvious fine particle infiltration is found in the sections of the 9 stone columns excavated from top to bottom, and the grain-size distribution curves of the stone columns tested before and after earthquakes are basically consistent, indicating that clogging pores do not appear in the stone columns. At the buried point of 1.25 m, the pore pressure dissipation rates are respectively 0.027 s-1 and 0.029 s-1 under the first and sixth times of intense dynamic loading, which proves that the drainage performance of the stone columns has not changed significantly.

Biao Shi, Feng Wu, Shuxin Li et al.

On the southeastern margin of the Ordos Basin, the mineral composition of marine-continent transitional facies deposits is complex. The shale, sandstone, coal, and related lithofacies frequently interact, and the lithology changes rapidly in the vertical direction. Due to the low resolution of conventional logging method and borehole enlargement which is a common while drilling, the commonly used methods for identification of lithology including high-quality shale which is prevailing in marine shale gas evaluation are less effective for the study area. First, deconvolution technology was used to improve the resolution of natural gamma rays, gamma rays without uranium and uranium logging curves. Then, a log cross-plot was used to identify the lithology including shale of marine-continent transitional facies, and the uranium-spontaneous potential curve overlap method was proposed to identify high-quality shale from marine-continent transitional facies. The results show that the deconvolution method can effectively improve the vertical resolution of natural gamma rays, gamma rays without uranium and uranium logging curves. The cross-plot of natural gamma-density logging data has a better effect on identifying the lithology of the marine-continent transitional facies, and the cross-plot of uranium logging data and gamma ray data without uranium can further identify three types of shale lithofacies (calcareous siliceous shale, siliceous clay shale and clay shale). In the marine-continent transitional facies, the newly proposed uranium-spontanous potential overlap method is better than the traditional ΔlogR method inidentifying high-quality shale. This research can provide theoretical support for reservoir evaluation of marine-continent transitional shale gas and improve the accuracy of high-quality shale identification.

Hang Ning, Zongxing Wang, Futian Liu et al.

The karst groundwater system has a complex spatial structure, strong aquifer permeability and poor anti-pollution performance. Once pollution occurs, the pollutants spread rapidly, and the repair is difficult. This study takes the pollution of a large karst spring in South China as an example. On the basis of a karst hydrogeological survey, combined with hydrochemical characteristics and multiple-tracer technology, the boundary of karst groundwater system and the distribution of underground river pipelines were analyzed, and the main pollution sources and pollution routes of the karst spring were identified. In addition, the genetic model of karst groundwater pollution was also explored. These results showe that the Q1 karst groundwater system was a typical "multi-source, single-sink" groundwater circulation pattern with two main runoff channels in the north and south. Manganese, total bacterial counts, ammonia nitrogen and total phosphorus were the main substances exceeding the standard, which were 17, 14, 7.2 and 3.8 times the groundwater quality standard threshold, respectively. The construction waste blocked the original channel of the underground river, forcing the groundwater to divert and flow under the landfill. Engineering investigation and dynamic compaction activities destroyed the natural clay impermeable stratum under the landfill, resulting in the early transport of domestic garbage and leachate entered into the karst pipeline, both of which caused the pollution of karst groundwater. This study provides an important reference for the prevention and control of karst groundwater pollution.

TONG Yan-mei, ZHANG Hu-yuan, ZHOU Guang-ping et al.

During the operation of underground repository of high-level radioactive waste, the highly alkaline solution generated by groundwater corroding lining concrete will diffuse into the bentonite buffer barrier, resulting in the degradation of barrier property. The KOH solution with different pH values was used to simulate the alkaline solution, and a one-year contact diffusion test at room temperature was conducted. Then, X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were performed to investigate the effect of slow diffusion on the mineralogy of bentonite. The XRF test results show that when the pH of KOH solution was greater than 12.6, the content of silicon began to decrease, that is, montmorillonite, quartz, cristobalite and other Si-containing minerals in bentonite were dissolved. At the same time, the content of K increased, indicating that the bentonite had an ion exchange reaction with the alkaline solution, a large amount of K+ ions in the solution entered the montmorillonite crystal layer. The XRD test results show that the 001 peak of montmorillonite mineral started to shift to the right at pH=12.6, the peak widths widened, and the peak intensity reduced considerably. When the pH>13, the crystal interlayer space decreased from 1.385 3 nm (13.853 Å) to 1.221 0 nm (12.210 Å), indicating that the crystal layer of montmorillonite was compressed. With the increase of the pH value, the content of minerals such as montmorillonite and quartz decreased significantly, and the contents of illite, clinoptilolite and feldspar minerals increased slightly. The SEM test results show that part of the montmorillonite crystal layer overlapped with the pH of the solution increasing, and then some cracks and holes were generated. As a result, the cracks can accelerate the dissolution of montmorillonite. In the one-year contact diffusion test, the diffusion depth of the KOH solution with pH=13.8 exceeded 7.5 mm, and the newly formed illite crystallites were observed on the contact surface between the alkaline solution and the bentonite. It is confirmed that the strong alkaline solution will cause montmorillonite dissolution and illitization.

Lifeng Xu, Qi Li, Yongsheng Tan et al.

It is important to understand the process of multiphase carbon dioxide (CO2) leakage in faults for the risk assessment of carbon capture and storage (CCS). To quantitatively characterize the CO2 leakage process in the fault, pressure sensors, fiber Bragg grating (FBG) temperature and strain sensors were simultaneously used to monitor CO2 leakage in the fault. Ten experiments were carried out, including five groups of gaseous CO2 leakage tests with initial pressures of 1–5 MPa and five groups of liquid CO2 leakage tests with initial pressures of 6–10 MPa. The results indicate that when liquid CO2 leaked with an initial pressure of 7–10 MPa, the pressure and temperature of CO2 dropped rapidly in the first few seconds and then remained unchanged. The behavior that CO2 continues to leak while maintaining temperature and pressure unchanged is defined as “temporary pseudo-sealing (TPS)” behavior, which continues for the first 1/3 of the leakage period. However, this TPS behavior did not occur in gaseous CO2 leakage. If only the pressure and temperature data were used to evaluate whether CO2 leakage occurred, we would misjudge the risk of leakage in CCS projects during the TPS period. The causes and conditions of TPS behavior were further studied experimentally. The results show that: (1) TPS behavior is caused by the phase transition energy generated when liquid CO2 leaks. (2) The condition for TPS behavior is a small leak aperture (0.2 mm). Only a small leakage rate can make the phase transition energy and pressure change from a dynamic equilibrium, and (3) The compression zone caused by the Bernoulli effect and fault “barrier” could reduce the CO2 leakage rate and further promote the occurrence of TPS behavior. This study provides technical and theoretical support for the quantitative characterization of the CO2 leakage process in faults of CCS projects.

Fengwen Lai, Fuquan Chen, Songyu Liu et al.

Pit-in-pit (PIP) excavations in an aquifer–aquitard system likely undergo catastrophic failures under the hydraulic uplift, the associated undrained stability problem, however, has not been well analyzed in the past. To this end, a hypothetical model of PIP braced excavation in typical soil layers of Shanghai, China is developed using the finite element limit analysis (FELA) tool. The FELA solutions of safety factors (FSs) against hydraulic uplift are verified with the results from the finite element analysis with strength reduction technique (SRFEA) and existing design approaches. Subsequently, FELA is employed to identify the triggering and failure mechanisms of PIP braced excavations subjected to hydraulic uplift. A series of parametric studies considering the various geometric configurations of the PIP excavation, undrained shear strengths of aquitard, and artesian pressures are carried out. The sensitivities of relevant design parameters are further assessed using a multivariate adaptive regression splines (MARS) model that is capable of accurately capturing the nonlinear relationships between a set of input variables and output variables in multi-dimensions. A MARS-based design equation used for predicting FS is finally presented using the artificial dataset from FELA for practical design uses.

Jianhua Lu, Songlin Xu, Chunhe Miao et al.

Abstract The wave velocity analysis of rock medium is the main method used to explore the internal compositions in the crust and research seismic. In this paper, a compression–shear coupled nonlinear elastic constitutive relation is established, which is consistent with the mechanical properties of rock and mineral medium under high pressure. On this basis, numerical solutions of the wave equation and plane wave analytical solutions for the primary and secondary wave velocities are obtained. As is indicated by the comparison with the linear elastic constitutive theory, the results reflect the compression–shear coupling characteristics of the rock, including the stress path effect and the compression–shear coupling wave effect. With different parameter values, the velocity of the secondary wave changes from lower than that of the elastic shear wave, to higher than that of the elastic shear wave. The research results are expected to provide meaningful explanations for the physical mechanisms of the supershear wave and sub‐Rayleigh wave, and guidance for the detection of rock and soil composition and the observation of seismic waves.

Manmohan On Thu

P. S. Zhegunov, E. V. Starikova, D. A. Petrov et al.

Research subject. This article presents data on the geological position of the Oyu hypabyssal complex. The aim of the study was to investigate the mineralogical, petrographic and petrological characteristics of dolerites deposited herein and to carry out their isotope dating.Materials and methods. The material for research was obtained during the course of geological fieldwork across. Field research and sampling of the Oyu complex was carried out in the southern part of the Yamb-Pe ridge. The subsequent investigation was performed for 21 dolerite samples (petrographic description, XRF and ICP-MS methods) and 26 zircon grains isolated from a single dolerite sample for isotopic dating (SHRIMP-II method).Results. The rocks of the Oyu complex are identified in the Lower Palaeozoic sequences of the Lemva zone of Pai-Khoi, where they form swarmof layered bodies and dykes with the thickness of the first meters–tens of meters and a length from 100 m to 1.5–2 km. The intrusions are located in the Middle-Late Ordovician sequences of the Khengur and Talbeytyvis formations and uncover in the Yamb-Pe structures and the right bank of the Bol’shaya Oyu river. The rocks of the complex have a distinct hypabyssal appearance, which is expressed in developed amygdaloidal, porphyry and glassy textures. According to petrographic data, two varieties of rocks – dolerites and leucodolerites – have been identified. Secondary changes have been described as propylitization and albitization. The rocks in the complex are enriched with SiO2 (43.05–51.10 wt %) and correspond to the subalkaline series (sodium and potassium-sodium type of alkalinity). Oys dolerites are enriched in LILE (Rb, Ba, K, Sr), though being depleted in HFSE (Th, Nb, Ta, Ti, Zr, Hf). The total content of REE (La + Sm + Yb) is established to be 21.17 (13.57–33.65) ppm, with the distribution showing a downward trend and the Eu-anomaly being not pronounced. The isotope dating of zircons (SHRIMP II) has confirmed the absolute age of dolerites in the Oyu complex to be 313.2 ± 2.6 Ma.Conclusions. The conducted comparison of the obtained data with those for gabbro and gabbrodolerites in the Khengur hypabyssal complex has revealed a paragenetic connection of the magmatic chambers of the Oyu and Khengur intrusions. A hypothesis has been proposed that links submarine hydrothermal processes with the intrusions of hypabyssal dolerite bodies. Such a hydrothermal activity is likely to have resulted in paleohydrothermal structures of "white smokers" and barite hydrothermal-sedimentary ore bodies, which are localized in the Lower-Middle Carbon Lemva formation.

K. Sassa, K. Dang