Lithology and Mineral Resources最新文献

Lithogeochemical characteristics of the pelitic and silty–pelitic bottom sediment samples, collected during Cruise 89 of the R/V Akademik Mstislav Keldysh (September 2022), from several areas in the southwestern Kara Sea (Baidaratsk Bay, Pukhuchansk Depression, West Kara Step, and Novaya Zemlya Depression) are discussied. It has been established that the muds contain a significant proportion of the lithogenic component. This conclusion agrees well with the localization of sediment data points on various discriminant diagrams near the reference points of average Paleozoic graywackes and PAAS. Such component could be sourced either from the fine-grained suspended particulates of the Ob River or from the sedimentary rocks and friable sediments of the Yamal and Yugra Peninsulas, Vaigach, and Novaya Zemlya. Although the upper layer of bottom sediments in the southwestern Kara Sea contains a noticeable amount of the mafic igneous rock fragments from Novaya Zemlya, which should make a significant contribution to their erosion products in the mud composition, parameters of the chondrite-normalized REE distribution in the sediments are inconsistent with such assumption.

Modern data on the formation of the mineral composition, geochemical and isotope-geochemical features of sediments from large rivers in Africa (Zambezi, Nile, Congo), as well as U–Pb isotope ages of detrital zircon populations in sands, obtained during complex long-term studies by Prof. E. Garzanti (Universita’ Di Milano-Bicocca, Italy) and his colleagues are considered. Ideas about the influence of chemical weathering on the composition of both silts and sands of the named large rivers are briefly summarized. The influence of river segmentation on the composition of the transported aluminosiliciclastics is discussed. The key points of the research results presented in the overview are outlined for specialists studying ancient sedimentary sequences.

A comparative analysis of the carbonate sedimentation conditions in two Paleoproterozoic basins (Onega and Pana-Kuolajarvi), located in the southeastern and northern areas of the Late Archean Karelian Craton is presented. The carbonate accumulation began in both basins during the Late Jatulian. Carbonate rocks in the Onega succession are predominantly dolostones, including stromatolite varieties; in the Pana-Kuolajarvi succession, they comprise both dolostones and limestones. During the Late Jatulian, cyanobacteria thrived in coastal marine settings of the Onega Basin. Some areas of the basin lost connection with the open sea at this time, facilitating the development of evaporation processes. The Pana-Kuolajarvi Basin lacked such diversity of cyanobacterial communities and any evaporitization. The geological and lithological data suggest that shallow, lagoon, playa lake, and sabkha environments existed in the Onega Basin in the Late Jatulian. The Pana-Kuolajarvi Basin was characterized by shallow (with occasional increased water input from the continent) and open marine settings. The geochemical characteristics of carbonate rocks obtained in our work lead to the same facies conclusions. Stromatolites in the Onega Basin were formed mainly in the intertidal zone. Occasionally, the connection of basin with the open sea was reduced and the conditions approached the lagoonal type. The oxic conditions existed for a limited time during the Jatulian only in the Onega Basin. Basically, the oxygen content in both sedimentation basins was close to the disoxic/oxic transition boundary. Fluctuations in the Ce anomaly magnitude in stromatolite laminas reflect changes in the oxygen content in water at immediate contact with the stromatolite buildup, suggesting the existence of oxygen “oases” in the basin with disoxic and oxygen-deficient conditions. Conclusions about redox conditions existing in the basin, based only on geochemical markers, are not sufficient, whereas conclusions about the carbonate sedimentation conditions prevailing in the basin agree maximally with the geological and lithological data based on several geochemical characteristics, such as REE spectra, Ce and Eu anomaly values, and ratios of individual REEs supported by the pair correlations between redox-sensitive elements.

The results of a comprehensive lithological study of the Upper Neopleistocene polar (Ostashkovo) moraine (textural, structural, and mineral-petrographic features, as well as the chemical composition and typomorphism of garnets and zircons, carried out to identify its lithostratigraphic criteria and substantiate the division and correlation of Quaternary sections are considered. The moraine is widespread only in the northernmost part of the Pechora Lowland, where it forms the day surface relief. The study was carried out in lower reaches of the Pechora River and in coastal outcrops of the Kuya, Chernaya, and Shapkina rivers. The moraine, characterized by a high content of the pelite fraction, has a finer composition than the Middle Neopleistocene moraines widely developed here. The mineralogical spectra of the moraine in the studied area are of the same type and represented by epidote, garnets, amphiboles, siderite, and pyrite. Total amount of pyrite and siderite increases to 20–35% with the permanent dominance of siderite over pyrite. The petrographic spectrum of the polar moraine is characterized by the presence of single fragments of the crinoid–bryozoan limestones (guide boulders of the Novaya Zemlya demolition area), as well as a very consistent orientation of elongated rock fragments, suggesting their delivery from the north-northeast (Pai-Khoi and Novaya Zemlya). It was overlapped only in lower reaches of the Shapkina River by a glacial tongue extending from the northwest (Fennoscandinavia and northern Timan). The presence of garnets in the moraine is related to their supply from metamorphic and certain types of igneous rocks. Based on the ZrO₂/HfO₂ ratio, the predominant mass of zircon grains was formed in mafic and felsic igneous rocks. Zircons from the metamorphic rocks are subordinate.

The lithological features of Late Quaternary sediments deposited during the marine isotope stage (MIS) 3 in the Ura River valley on the Barents Sea coast (Kola region, northwestern Russia) have been studied. Seismo-induced soft-sediment deformation structures (SSDS) are preserved in the sandy–clayey deposits as five deformed layers separated by undisturbed deposits. These layers are marked by load casts, flame structures, injections, sedimentary breccia, and folds. The SSDS were produced by several processes: origination of debris flows in the subaqueous setting due to shear stress, gravity load of the overlying deposits, and liquefaction. The seismic shock and aftershocks could trigger the gravity flow activity and initiate the processes of liquefaction and fluidization of sediments. We believe that the main seismogenic zone was related to reactivation of the large Karpinsky oblique-slip fault, which separated the Baltic Shield from the Barents Sea Plate of the West Arctic Platform, contrast movements at the boundary of large structural elements, and development of strains at the front of the advancing Weichselian Ice Sheet at MIS 2.

The pyrolytic characteristics of dispersed OM were determined in clay pulp samples taken from 23 mud volcanoes of the Kerch–Taman area (Crimean–Caucasian region). The organic matter (OM) belongs to type III kerogen, and its alteration level corresponds to the earliest stages of oil generation. It is also shown that, in terms of the pyrolytic characteristics, the OM carried out by volcanoes is almost a complete analog of the dispersed OM present in clays of the Maikop Group. However, in comparison with the clays, the mud-volcanic pulp has a higher content of bitumoids. Relationship between the kerogen parameter Т_max and some temperature-dependent characteristics of the water (t(Mg-Li) and δ¹⁸O in H₂O) and gas (δ¹³C in CH₄) phases of mud volcanic ejecta was found for the first time in the mud volcanic systems of the Kerch–Taman region. These relationships reflect the general variation trend of fluid systems with the formation temperature increase and indicate the formation of solid, liquid, and gaseous phases of mud-volcanic ejecta in a single deep mud-volcanic formation. However, no discernible OM contamination of clay pulp from the surrounding sediments or walls of the mud-volcanic channel was found.

The results of a comparison of various ratios of trace elements-indicators of the composition of provenances for clay rocks of the Middle Riphean Avzyan Formation and the Upper Riphean Biryan Subformation of the Zilmerdak Formation (Bashkirian meganticlinorium, Southern Urals) are analyzed. The formation of these two objects is separated by a hiatus, with the maximum duration up to 250 Ma. The study is based on materials related to the content of trace elements in clay/fine-grained clastic rocks, respectively, of the Avzyan Formation (28 samples) and Biryan Subformation (16 samples) from the collections of E.Z. Gareev and the author, obtained by the ICP-MS method at the IGG Ural Branch of the Russian Academy of Sciences (Yekaterinburg). Distribution of individual and average data points of clay rocks of the named objects on La/Sc–Th/Co, Sc–Th/Sc, Eu/Eu*–Th/Sc, Ni–V–10Th, Th–La–Sc, Y/Ni–Cr/V, Cr/Th–Th/Sc, and Hf–La/Th diagrams are significantly comparable. The chondrite-normalized spectra of rare earth elements (REE) are also comparable. Only on the Th–Th/U diagram, the distribution of data points has a slightly different form, suggesting that either the provenance composition was invariable for almost 250 Ma, the duration of the pre-Upper Riphean hiatus was not so long, the author’s analytics are “lame”, or there are other reasons.

Chromites are a common component of the heavy fraction of sedimentary cover deposits in the platform areas, and their contents usually do not exceed some percents. Commonly, economic chromite placers are formed in vicinity of bedrock sources. Within the Lukoyanov placer district (Nizhny Novgorod region), high chromite contents (up to 100 kg/m³) were found in Middle Jurassic complex coastal-marine rare metal–titanium placers of economic importance. Placer bodies are localized on the periphery of domes in the sedimentary cover. The placers can be sourced from Upper Permian and Lower Jurassic rocks, which were eroded in the zone of positive tectonic structures of the cover and platform basement and within the adjacent land. The revealed patterns can serve as a basis for forecasting similar deposits within promising areas.

A new approach is proposed to assess the degree of defect density of kaolinite minerals using their IR spectra in the OH-stretching vibration region. Three linear equations were obtained that relate the ratios of spectroscopic parameters to each other: (frac{{Aleft( {{{nu }_{3}}} right)}}{{Aleft( {{{nu }_{3}}} right) + Aleft( {{{nu }_{2}}} right)}} = - {kern 1pt} 0.2177frac{{FWHMleft( {{{nu }_{1}}} right)}}{{FWHMleft( {{{nu }_{4}}} right)}}) + 1.247; (frac{{FWHMleft( {{{nu }_{3}}} right)}}{{FWHMleft( {{{nu }_{2}}} right)}} = - 0.5804frac{{FWHMleft( {{{nu }_{1}}} right)}}{{FWHMleft( {{{nu }_{4}}} right)}}) + 2.8696; (frac{{FWHMleft( {{{nu }_{3}}} right)}}{{FWHMleft( {{{nu }_{2}}} right)}} = 2.636frac{{Aleft( {{{nu }_{3}}} right)}}{{Aleft( {{{nu }_{3}}} right) + Aleft( {{{nu }_{2}}} right)}} - 0.4437), where: FWHM(ν_i) is a full width at half maximum and A(ν_i) is the integral intensity of Lorentzian absorption bands at ν₁ ~ 3697 cm^–1, ν₂ ~ 3670 cm^–1, ν₃ ~ 3652 cm^–1 and ν₄ ~ 3620 cm^–1, respectively. These equations made it possible to establish criteria for decomposing the IR spectra into individual bands (ν_i) and determining the optimal values for the FWHM(ν_i) and A(ν_i) parameters used for calculating the contents of high-ordered kaolinite (HOK) and low-ordered kaolinite (LOK) phases in natural samples with an accuracy of ~5%.

Clay minerals were studied in Pleistocene sediments from Hole 1038А (114.50 m deep) and Hole 1038Н (192.80 m deep) drilled near a hydrothermal vent with a temperature of 217°C on Central Hill, 275 m east of Hole 1038B. In sediments from Hole 1038A, at a depth of 8.52 m, <0.001-mm fraction consists completely of chlorite. In the rest of the sediment section in Hole 1038A, clay minerals consist of chlorite (from ~64 to ~98%) and illite. In sediments from Hole 1038H, clay minerals also consist of chlorite and illite. They were formed under conditions related to the intrusion of a basaltic melt as laccolith into the Escanaba Trough and the heating under its influence of a solution, during the interaction of which with sediments at a high-temperature stage biotite was formed. During the subsequent slow cooling of the laccolith and fluid, the newly formed biotite was replaced completely by chlorite. Illite was precipitated from a hydrothermal solution. At a depth of 183 m, in sediments from Hole 1038H, clay minerals consist of biotite, chlorite, and dioctahedral smectite, just as in sediments from Hole 1038B during their formation under conditions of rapid cooling of the laccolith flank and penetration of sea water into the sediments. The paper shows similarities and dissimilarities in the formation of clay minerals in Pleistocene sediments of the Central Hill, located above the slowly cooling part of the laccolith (Holes 1038A and 1038H) and in sediments located above the rapidly cooling laccolith flank (Hole 1038B).