Fraction Of Rocks Research Articles

Radiogenic Ca isotopes confirm post-formation K depletion of lower crust

Heat flow studies suggest that the lower crust has low concentrations of heat-producing elements. This could be due to either (i) greater fractions of basaltic rock at depth or (ii) metamorphic depletion of radioactive elements from rocks with more evolved (andesitic to granodioritic) compositions. However, seismic data suggest that lower crust is not predominantly basaltic, and previous studies (using Pb and Sr isotopes) have shown that lower crustal rocks have experienced significant losses of U and Rb. This loss, however, is poorly constrained for K, which is inferred to be the most important source of radioactive heat in the earliest crust. Our high precision Ca isotope measurements on a suite of granulite facies rocks and minerals from several localities show that significant losses of K (~60 % to >95 %) are associated with high temperature metamorphism. These results support models whereby reduction of heat production from the lower crust, and consequent stabilisation of continental cratons in the Precambrian, are largely due to high temperature metamorphic processes. Relative changes in whole rock K/Ca suggest that 20-30 % minimum (granitic) melt removal can explain the K depletions.

Effect of rock shape representation in DEM on flow and energy utilisation in a pilot SAG mill

The impact of the shape representation used for rock particles in a DEM model of a SAG mill on charge dynamics and energy utilisation is investigated. A 1.8-m diameter pilot scale SAG mill which includes realistic end walls and a discharge grate is used. This size of mill is used for scale-up and design processes for industrial SAG mills so understanding the effect of approximating the particles as being spherical or non-round is important. The cataracting component of the flow is found to be insensitive to the particle shape used in the model but the cascading part of the flow is moderately sensitive with the shoulder moving slightly higher, the bulk toe moving closer into the charge and the centre of circulation moving more strongly higher. The end walls are found to have a strong effect on the flow dominating the dynamics in the outmost parts of the charge and strengthening the particle microstructure via the axial compression induced by the transfer of the weight of the charge to the end walls. The cataracting stream consists of coherent bands of predominantly finer material being thrown on ballistic trajectories. Its form is a superposition of one component formed by the flow from the belly lifters and a second from the flow along the radial end wall lifters. The net power draw is found to increase slightly, but larger changes in the pattern of energy usage within the mill are identified. Rock shape has a significantly stronger impact on the large size classes in the charge and leads to strong migration of energy usage from the finer material to the coarser and from the rock fractions to the media.

Experimental evidence for mineral-controlled release of radiogenic Nd, Hf and Pb isotopes from granitic rocks during progressive chemical weathering

The role of accessory minerals in the incongruent release of Hf and Pb during continental weathering and its implications for the generation of distinct seawater isotope compositions is subject of debate. While it has been suggested that radiogenic Hf and Pb isotope signatures released during the dissolution of rocks are controlled by the relative abundances of minerals with distinct isotope compositions and differences in their resistance to dissolution there has not been a comprehensive experimental investigation of these processes to date. We carried out systematic sequential leaching experiments on fresh and partly weathered granitic rock samples as well as separated zircons from the Central Aar Granite in Switzerland. Combined with major and rare earth element concentrations our new quantitative experimental data reveal systematic preferential release of radiogenic Nd, Hf and Pb isotopes primarily controlled by dissolution characteristics of the host rock's easily dissolvable accessory and major minerals, in particular apatite and sphene, during weak chemical weathering. Moreover, Pb isotope signatures of incipient weathering conditions, contrary to expectations, indicate initial congruent release of Pb from freshly exposed mineral surfaces that becomes subsequently incongruent. During more advanced chemical weathering stages, as well as enhanced physical weathering conditions, the dissolution of major minerals (i.e. feldspars) becomes dominant for Nd and Pb isotope signatures, whereas Hf isotopes are still dominated by contributions from highly radiogenic accessories.Additional leaching experiments of zircon separates were performed to test the specific role of zircons for Hf isotope compositions of riverine runoff. It is demonstrated that zircon is more efficiently dissolved when physical weathering is enhanced. This increased Hf release originating from partial dissolution of zircons, however, is quantitatively not sufficient to explain less radiogenic Hf isotope signatures in seawater during episodes of enhanced mechanical erosion alone. Moreover, the observed addition of Hf from the more congruent dissolution of the zircon-free fractions of the parent rock due to enhanced physical weathering indicates that these minerals also play an important role in controlling Hf isotope signatures released under deglacial conditions.

Feed Size Distribution Feedforward Control for a Grinding Mill Circuit

This paper proposes a method to measure and reject disturbances caused by changes in the ore distribution of the feed to a grinding mill circuit. A computer vision system is presented to measure the fraction of rocks in the feed, using only basic equipment and algorithms. A feedforward controller is designed to reject the measured feed size disturbance within the mill before causing further disturbances downstream. The feedforward controller is implemented in simulation to control a nonlinear mill model, and is compared to conventional feedback control. The allowable plant-model mismatch and practicality of feedforward control for industrial applications are investigated. It was found that feedforward control has a noticeable advantage over feedback control if well tuned. The most significant disturbance is the efficiency of the mill to break ore into fine material. Since this is not currently measured in real-time, it limits the performance of a feedforward controller in practice.

A geochemical investigation of the free and carbonate-bound organic matter in the clay-sized fraction of argillaceous source rocks and its significance for biogenic interpretation

The molecular composition and biomarker distribution of various occurrences of organic matter in argillaceous source rocks developed in fresh and saline lacustrine environments were revealed by successive treatments of solvent extraction followed by acid hydrolysis using gas chromatography–mass spectrometry. The free fraction obtained by solvent extraction provided abundant geochemical information concerning the sedimentary environment, thermal maturity and biogenic origin, and obvious differences existed between fresh and saline lacustrine source rock samples. Our research results indicate that the carbonate-mineral-bound (CM-bound) fraction released by successive acid hydrolysis could also serve as a significant biogenic indicator, as the bicyclic sesquiterpenoids, indicative of Botryococcus braunii origin, were specifically detected in quite high abundance in the acid-soluble fraction. In addition, the light end hydrocarbons were much better preserved in the acid-soluble fraction, and elemental sulfur was only detected in the CM-bound fraction, suggesting a relatively confined environment for the CM-bound fraction, which thus could preserve additional geochemical information compared to that of the free fraction. The CM-bound fraction also exhibited discernable differences between fresh and saline lacustrine samples. Therefore, it can be concluded that comprehensive analysis of free and CM-bound fractions in the argillaceous source rocks can provide a more authentic and objective interpretation of geologic conditions.

Linking oral bioaccessibility and solid phase distribution of potentially toxic elements in extractive waste and soil from an abandoned mine site: Case study in Campello Monti, NW Italy

Oral bioaccessibility and solid phase distribution of potentially toxic elements (PTE) from extractive waste streams were investigated to assess the potential human health risk posed by abandoned mines. The solid phase distribution along with micro-X-ray fluorescence (micro-XRF) and scanning electron microscopy (SEM) analysis were also performed. The results showed that the total concentrations of PTE were higher in <250 μm size fractions of waste rock and soil samples in comparison to the <2 mm size fractions. Mean value of total concentrations of chromium(Cr), copper (Cu), and nickel (Ni) in waste rocks (size fractions <250 μm) were found to be 1299, 1570, and 4010 mg/kg respectively due to the parent material. However, only 11% of Ni in this sample was orally bioaccessible. Detailed analysis of the oral bioaccessible fraction (BAF, reported as the ratio of highest bioaccessible concentration compared with the total concentration from the 250 μm fraction) across all samples showed that Cr, Cu, and Ni varied from 1 to 6%, 14 to 47%, and 5 to 21%, respectively. The variation can be attributed to the difference in pH, organic matter content and mineralogical composition of the samples. Non-specific sequential extraction showed that the non-mobile forms of PTE were associated with the clay and Fe oxide components of the environmental matrices. The present study demonstrates how oral bioaccessibility, solid phase distribution and mineralogical analysis can provide insights into the distribution, fate and behaviour of PTE in waste streams from abandoned mine sites and inform human health risk posed by such sites .

A Rock Model for the Cold and Hot Spots in the Chang’E Microwave Brightness Temperature Map

Thermal anomaly spots (both hot and cold) have been found in the global 37-GHz brightness temperature (TB) map of the moon based on the Chang’E (CE) microwave radiometer measurements. To explain their origin, a rock model is proposed to simulate the TB variation against latitude along the profile of a fresh crater in a single track way, which is selected to highlight the topographic effect and avoid any modification to the data. A mixed upper layer made up of rock and soil (regolith and dust) was employed into our previous multilayer model. The thermal properties (thermal conductivity and heat capacity) of the mixture layer are presumed to be linear with the fraction of rocks. Given that high-frequency (37 GHz) measurements are chosen, only the meter size and larger rocks of the upper mixed layer are considered to avoid scattering effects. Several fresh craters poor/rich in ilmenite are selected as testing sites. Despite uncertainties in parameters such as rock abundance (RA), and iron and titanium abundances, three conclusions can be reached from these cases: 1) RA has a significant effect on both the TB value and TB variation trend against latitude; its contribution over some craters may be as high as 15 K; 2) the simulations based on our rock model fit the CE observations better than those when rocks are not included; and 3) the rock and ilmenite contributions could be the main cause for the cold and hot spots found in the CE microwave map.

Diagenesis of volcanic-rich tight sandstones and conglomerates: a case study from Cretaceous Yingcheng Formation, Changling Sag, Songliao Basin, China

Thick conglomerate and sandstone lithofacies of Yingcheng Formation in Changling Sag are tight gas reservoirs. The formation contains a fair amount of volcanic clasts and accumulated in a deltaic system that spans from delta plain to prodelta depositional setting. High-quality reservoirs are only a small fraction of these thick siliciclastic rocks. Petrographic analysis has been used to assess diagenetic processes, paragenetic sequence, and their effects on the reservoir qualities. The major loss of primary porosity is due to compaction along with grain-coating, pore-filling clay, and quartz cements. Alteration of volcanic rock fragments supplied alkali cations which favored formation of chlorite, smectite, and zeolite cements. The thickness of the chlorite coating decreases from the delta plain to the distal part of the delta front. On the contrary, the content of the zeolite cement increases toward the distal part of the delta front. Quartz and feldspar cements were ubiquitous due to high SiO2 concentration and alkali cations. Early dissolution of volcanic rock fragments and feldspars by freshwater increased porosity but did not contribute much to the permeability because pore-throats are predominantly occluded with clay and pseudomatrix. Late-stage dissolution of the zeolite cement was caused by organic acid expelled from maturation of organic matter. Although the reservoirs with chlorite coatings have moderate porosity, the permeability in situ is very low and pore-throat sizes are small. The high-quality reservoirs are medium- to fine-grained zeolite-dissolved sandstones developed in the distal part of the delta front and shallow lacustrine.

МЕТАЛЛОНОСНОСТЬ ОРГАНИЧЕСКОЙ И МИНЕРАЛЬНОЙ ЧАСТИ НЕФТЕБИТУМИНОЗНОЙ ПОРОДЫ

Heavy high-viscosity oils and natural bitumen are increasingly attracting research attention as al-ternative sources of hydrocarbon raw materials. The development and rational use of their deposits is considered to be essential for extracting synthetic oil and rare earth metals, as well as for obtaining astringent materials for road construction. Since natural bitumen is rich in microelements, this research sets out to investigate their distribution across the mineral and organic fractions of the rock, as well as in the tar-asphaltene substances contained in natural bitumen. The concentration of nickel, vanadium and accompanying trace elements is found to be uneven in all kir constituents. The largest share of the metals is observed to be concentrated in high-molecular compounds. The data obtained on the distribution of metals in the mineral and organic fractions of petroleum bituminous rock, as well as in the tar-asphaltene substances obtained from natural bitumen are deemed useful for developing technological schemes for their comprehensive processing. In addition, complete utilization of oil bituminous rock can be achieved.

Mercury in grain size fractions of aggregates and extractive waste from hard coal mining

Abstract Hard coal production is closely linked to the generation of significant quantities of extractive waste that require further use, in practice recognized as waste or as a raw material. It is therefore important to seek further or improve existing methods of waste material management. Studies conducted in earlier works have shown that it is possible to obtain a low-sulfur grain size fraction (grain class) so that it can be used in excavations requiring reclamation by filling. The purpose of the research presented in this paper is to determine the mercury content in hard coal mining by-products. The presence of mercury in the waste material is known and documented in the literature. However, the level of the content of this element in aggregates or wastes is important. This paper presents the problem of determining the minimum size of rock fractions meeting the specified limits for mercury content above which the material can be considered as safe are used to fill post-mining excavations. The total mercury content was determined using the classical atomic absorption method for all the collected and isolated samples (Altec AMA-254 analyzer). The total mercury content of the samples in the analytical state (Hga) was determined. Laboratory research included waste material directly from production (mining and processing of rock) from the one of the hard coal mine USCB. Coal sludge (silt) (after dewatering on filter presses) and 13 aggregates samples were analyzed, and then separated into 15 grain size fractions. The mercury determination method used in the study allowed its content in the range of 0.0568 to 0.0787 mg/kg, on an average mean of 0.0649 mg/kg (average moisture of the samples - 4.3%). On the other hand, the total mercury content of all the fractions extracted from 13 samples of aggregates showed a high variability in the content of this element, with a noticeabletendency of decreasing mercury content along with the increase in grain size. The average values of the total mercury content decrease from 0.4030 mg/kg for the finest fraction (0-6 mm) to 0.0291 mg/kg for the thickest fraction (120-200 mm) (aggregate sample moisture at approximately 1%). In general, it can be stated that the analyzed samples of coal sludge and grain fractions of aggregates meet the criteria for inert mining waste with respect to the mercury content. Based on the studies conducted, it can be concluded that due to the presence of mercury there is no need to discard fine fractions from aggregates. However, the removal of waste rock material less than 8 mm significantly increases the quality of the material. The obtained results and the statistical analysis clearly indicate a strong correlation between the occurrence of mercury and total sulfur in the material (R2 linear coefficient of determination at 0.9151), where no weathering has yet occurred. In the case of weathering, however, there is no correlation between the occurrence of mercury and sulfur, which may be due to the differences in the processes that govern the transformation and migration of mercury and sulfur compounds.

Assessment of Potential Nutrient Release from Phosphate Rock and Dolostone for Application in Acid Soils

Finding alternative local sources of plant nutrients is a practical, low-cost, and long-term strategy. In this study, laboratory column experiments were conducted in a completely randomized design to evaluate the feasibility of using phosphate rock and dolostone as fertilizers or acid-neutralizing agents for application in tropical acid soils. The dissolution rates of different particle-size fractions (0.063–0.25, 0.25–0.5, and 0.5–2 mm) of both rocks were studied by citric acid solution at pH 4 and 2 and water, with extraction times of 1, 3, 5, 7, 12, 24, 72, 144, 240, and 360 h. The results showed that the dissolution of both rocks depended on the particle size, leaching solution, and extraction time. The dissolution rate of rock-forming minerals increased as the specific surface area increased, corresponding to a decrease in particle size. In all cases, the release kinetics was characterized by two phases: 1) a first stage of rapid release that lasted 24 h and would ensure short-term nutrient release, and 2) a second stage of slow release after 24 h, representing the long-term nutrient release efficiency. Both rocks were suitable as slow-release fertilizers in strongly acid soils and would ensure the replenishment of P, Ca, and Mg. A combination of fine and medium particle-size fractions should be used to ensure high nutrient-release efficiency. Much work could remain to determine the overall impact of considerable amounts of fresh rocks in soils.

Occurrence, origin, and significance of melagranites in the South Mountain Batholith, Nova Scotia

Melagranites (colour index &gt; 20, with biotite &gt; garnet &gt; cordierite) constitute ∼0.1% of the area of the 7300 km2 peraluminous South Mountain Batholith (SMB), Nova Scotia. The melagranites occur as small bodies showing sharp to gradational contacts against the Meguma Supergroup country rocks, and coeval mingling contacts against other facies of the batholith. They also occur as elliptical or blocky metre-scale enclaves elsewhere in the SMB. Characteristic petrological features of the melagranites include high modal abundances of sulphide minerals, strongly reacted metasedimentary xenoliths, mafic mineral-rich clots, apparent porphyritic textures with highly variable proportions of alkali feldspar megacrysts, and allotriomorphic-granular textures. Chemically and isotopically, melagranite rocks have wide compositional variations. In most major-element, trace-element, and isotopic variation diagrams, the melagranites lie on mixing lines between the more abundant granodioritic and monzogranitic phases of the SMB and the metasedimentary rocks of the Meguma Supergroup. Textural evidence, supported by published experimental evidence, suggests that the garnet, cordierite, and K-feldspar are peritectic phases resulting from incongruent melting of the pelitic fraction of the Meguma metasedimentary country rocks. The field relations, mineral assemblages, textural features, and chemical compositions of the melagranites all point to the melagranites as highly concentrated contamination zones in the SMB, representing small portions of the batholith that have failed either to complete the assimilation process or to disperse their contaminants widely in the batholith. As such, these rarely preserved melagranites provide petrogenetic information disproportionate in importance to their abundance in the batholith, especially about the significant role of contamination and assimilation in determining the physical and chemical composition of the SMB. Without preservation of melagranites in the SMB, and by extension all granite bodies, the petrogenetic importance of contamination is difficult to assess, even with trace-element and isotopic data. The present study shows that high quality field observations are as important in deciphering petrogenesis as chemical data.

δ34S character of organosulfur compounds in kerogen and bitumen fractions of sedimentary rocks

Hydropyrolysis (HyPy) of S-containing oil mature rock samples from two geologic settings each produced much higher concentrations of organosulfur compounds (OSCs) compared to their free occurrence in the bitumen. The δ34S values of the most abundant OSCs from the kerogen and in the bitumen, were measured by gas chromatography inductively coupled plasma mass spectrometry (GC-ICP-MS). DBT and mDBTs from the HyPy processed kerogen fractions showed a distinct 34S depletion, with δ34S values up to 12‰ lighter than their bitumen occurrence. The different δ34S values of OSCs from the kerogen and bitumen fractions is likely reflective of differences in timing of production, reduced sulfur sources or organic sulfurisation mechanism.

Application of Portland cement to control acid mine drainage generation from waste rocks

Cement has been little investigated as a control for acid mine drainage, despite having advantages over cheaper alternatives. Leaching column experiments (set up in triplicate) investigated the effect of applying Portland cement slurries with three different water/cement (w/c) ratios (0.8, 1.0, 1.2) to pyrite-bearing waste rock from Brukunga mine in southeastern Australia. After application of the cement, leachate from the cemented columns showed a reduction in acidity compared to the control columns of ∼85% and 100% for w/c ratios of 0.8 and both 1.0 and 1.2 respectively. This was due to direct neutralisation of acidity by cement dissolution and encapsulation of the pyrite-bearing rock fragments by the cement (as shown by a reduction in oxygen consumption rates of up to 70%). In columns with the higher w/c ratios (1.0, 1.2), the cement slurry penetrated to the base of the columns and greatly decreased the permeability. The greater coverage of the waste rock by the cement and increased contact time between the leachate and cement meant that no acid drainage leached from these columns (pH 7–8, Fe, Al, Mn, Zn and Cu concentrations rarely above detection limits). In columns with a w/c ratio of 0.8, the cement slurry was mostly retained in the upper 30–50% of the waste rock, leaving a large fraction of the waste rock below without any cement coverage. Leachate drained relatively quickly from these columns, probably through a small number of pathways through the cement plug and carried relatively small loads of acidity and metals from uncemented waste rock beneath the cement. Thus cement may be a viable method for controlling acid mine drainage generation from waste rock dumps, and could be applied with both lower and higher w/c ratios could be used to achieve an optimal balance between deep penetration and surficial retention.

Technogenic Rock Dumps Physical Properties' Prognosis via Results of the Structure Numerical Modeling

Understanding of internal structure of the technogenic rock dumps (gob dumps) is required condition for estimation of using ones as filtration massifs for treatment of mine wastewater. Internal structure of gob piles greatly depends on dumping technology to applying restrictions for use them as filtration massifs. Numerical modelling of gob dumps allows adequately estimate them physical parameters, as a filtration coefficient, density, etc. The gob dumps numerical modelling results given in this article, in particular was examined grain size distribution of determined fractions depend on dump height. Shown, that filtration coefficient is in a nonlinear dependence on amount of several fractions of rock in gob dump. The numerical model adequacy both the gob structure and the dependence of filtration coefficient from gob height acknowledged equality of calculated and real filtration coefficient values. The results of this research can be apply to peripheral dumping technology.

Enhancement of Operating Efficiency Of The Central Coal-Preparation Plant of “MMK - UGOL” Ltd. Under Current Conditions

In this article the subject of enhancement of operating efficiency of the central coal-preparation plant of OOO “MMK-UGOL” is encompassed. Modern trends in the development of technologies and equipment for coal beneficiation are due to the following requirements: improving competitiveness of coal products, improvement of quality of marketable products, reduction of coal production cost, environmental requirements: polluting emission abatement, prepared coal saving, improvement of the effectiveness of resource conservation; complex mechanization and beneficiation process automation. In the article the contemporary problems of raw coal benefication under current conditions of the increased dilution of withdrawable coals with rock fractions are considered. Comparative analysis of efficiency of application of modern concentrating equipment under the conditions of the CCPP of OOO “MMK-UGOL” is carried out on the basis of research works. Particular attention is paid to dehydration of produced coal concentrate with content of volatile agents of more than 35.0% and content of fine-dispersed particles in flotation concentrate of more than 50.0%. Comparative analysis of the coal concentrate dehydration technologies is conducted.

Correlations of suspended sediment size with bedrock lithology and glacier dynamics

ABSTRACTThe hypothesized link between glacier surging and bedrock geology motivates this study of the suspended sediment size distributions (SSSD) from surge-type and non-surge-type glaciers. We analyze SSSDs from proglacial streams in 20 individual basins comprising various fractions of metasedimentary (MS) and felsic plutonic rocks. We compare the size distributions by performing tests of significance on the distribution statistics, and a principal component analysis on discrete grain sizes. We find that surge-type and non-surge-type glaciers underlain solely by MS rocks have significantly different SSSDs, while surge-type glaciers as a whole have remarkably similar SSSDs, regardless of the underlying bedrock geology. These observations hint at a relationship between sediment characteristics and glacier surging, though causation in either direction cannot be established without additional data.

الاستقصاء المعدني والخصائص المعدنية المائية لليورانيوم وعناصر الأرض النادرة ، تمعدن رواسب الحمامات ، ج.قطار ، الصحراء الشرقية - مصر

يعتبر تواجد اليورانيوم من GV بمثابة رواسب يورانيوم perigranitic بينما تعتبر جميع الأنواع الأخرى ترسبات داخل الحبيبات. تم فصل وتحديد المعادن الاقتصادية الرئيسية. تم العثور على اليورانوفان لتمثيل معدن اليورانيوم الرئيسي بينما تحدث العناصر الأرضية النادرة في شكل حبيبات منتشرة دقيقة للغاية من العناصر الخفيفة أو في شكل عناصر ثقيلة مرتبطة بأكاسيد الحديد وجزء الطين من الصخور المضيفة. بالنسبة للأعمال الجيوكيميائية والمعدنية المائية ، تم جمع عينة تكنولوجية (4000 جزء في المليون من اليورانيوم و 3500 جزء في المليون من العناصر الأرضية النادرة) في الجزء الشمالي من الصحراء الشرقية ، وتمعدن الحمامات GV لـ G. Gattar. تم بعد ذلك إخضاع المادة الخام التي تم جمعها لمعالجة كيميائية تتضمن ترشيح حمض الكبريتيك وتم فصل U و REE المذاب من سائل الترشيح الناتج. تمت دراسة بديلين ، وهما التبادل الأيوني لـ U بعد ترسيب الأكسالات في الكيانات الأرضية النادرة أو الترسيب المتتالي الانتقائي.

Evaluation of Rock Mechanical Properties Alteration During Matrix Stimulation With Chelating Agents

Well stimulation using acidic solutions is widely used to treat carbonate formations. The acidic fluids remove the near-wellbore damage and create channels around the wellbore by dissolving fraction of the carbonate rocks. Many stimulation fluids have been used such as hydrochloric acid (HCl) acid, organic acids, and chelating agents to stimulate carbonate reservoirs. Wormholes that are created by these fluids are very effective and will yield negative skin values and this will enhance the well productivity. In addition to the wormhole creation, the diffusion of these fluids inside the pores of the rock may create significant and permanent changes in the rock mechanical properties. These changes can eventually lead to weakening the rock strength, which may lead to future formation damage due to the wellbore instability. In this paper, the effect of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) chelating agents on the carbonate rocks elastic properties was investigated. The effect of wormholes created by chelating agent on the rock mechanical properties was investigated. Computed tomography (CT) scan and acoustic measurements were conducted on the core samples before and after matrix stimulation treatments. Experimental results showed that the mechanical properties of strong rocks such as Indiana limestone (IL) cores were not affected when chelating agents were used to stimulate those cores. On the other hand, less strong rocks such as Austin chalk (AC) show significant alteration on the rock elastic properties when chelating agents were used as stimulation fluids.

Behavior of isotope (18O/16O, 234U/238U) systems during the formation of uranium deposits of the “sandstone” type

The uneven character of the distribution of 18O/16O and 234U/238U values was established in the vertical cross section of the productive sequence of the Dybryn uranium deposit (Vitim uranium-ore region, Buryatia). Both a deficiency and an excess of 234U in relation to the equilibrium 234U/238U ratio in the vertical sequence may provide evidence for the extremely low rate of the infiltration water flow. The behavior of oxygen isotope characteristics for different size fractions of terrigenous rocks provides evidence for active uranium redistribution and openness of the isotope system of this element during interaction of terrigenous–sedimentary rocks with infiltration waters.