Doklady Earth Sciences最新文献

Abstract

Sviatonossites are syenites with andradite garnet, a rare type of igneous rocks described by P. Eskola in 1913 on the Svyatoi Nos Peninsula (Lake Baikal). Due to the absence of zircon in the rocks, which makes it possible to date them reliably by the U‒Pb method, geochronological Sm–Nd studies of the bulk composition and minerals are carried out. As a result, two estimated periods of the formation of sviatonossites are obtained. According to the bulk composition and four minerals (garnet, pyroxene, potassium feldspar, and apatite), the age is 262 ± 21 Ma (RMSD = 1.6), and according to the bulk composition and garnet, it is 274 ± 25 Ma (RMSD = 0). The results obtained coincide with the timing of tectonic–metamorphic and igneous processes associated with the formation of the Eastern Transbaikalia segment of the Central Asian (Mongol–Okhotsk) folded belt. Sviatonossites in the complexes of mobile (folded) belts framed by the Siberian Craton are indicator rocks reflecting the manifestation of mantle–crustal interaction.

Abstract—

The age of formation of the explosion pipes of the Chapinskii complex in the Chingasan magmatic belt in the northern part of the Yenisei Ridge is determined. U–Pb dating of zircon megacrysts from alkaline ultramafic rocks has established the values of 657.7 ± 13.4 and 647.6 ± 9.7 Ma for the Natalyinskaya pipe and Pipe no. 3, respectively. The intrusion of alkaline ultramafic explosion pipes of the Chapinskii complex corresponds to the time of manifestation of alkaline ultramafic magmatism along the southern and southwestern margin of the Siberian Craton.

Abstract—The disturbances of the geomagnetic field in the surface atmosphere were considered during a series of strong earthquakes that occurred on April 2–3, 2024, in the vicinity of the island of Taiwan. The data from the Mikhnevo Geophysical Observatory of the Sadovskii Institute of Geosphere Dynamics, Russian Academy of Sciences, and the observatories of the international INTERMAGNET network were analyzed. It was shown that in the absence of sole-related global disturbances of the Earth’s magnetic field, earthquakes were accompanied by geomagnetic variations with a maximum amplitude of ~10 nT and a total duration of about four hours. The delay time of the magnetic effect relative to the main shock of the first earthquake was ~60 min. The ionospheric effect of the event considered was established in the form of variations in the critical frequency of the F2 layer of the ionosphere on the basis the ionograms of height–frequency sounding obtained at the Okinawa ionospheric monitoring station and freely available on the website of the Japanese National Institute of Information and Communication Technologies.

Abstract

The palynological analysis of the Paleogene and Neogene sequences of the southern part of West Siberia (borehole 2, Novosibirsk oblast) showed that the conifer bisaccate pollen in the spore–pollen spectra exhibits a series of morphological features allowing its comparison with the modern pollen of Cathaya argyrophylla Chun et Kuang. These palynomorphs belong to relict vegetation, which currently occurs in the wet subtropical climate of South China, and are important climate indicators. The palynomorphs are ascribed to the ancestral forms of the species Cathaya as Abietineaepollenites sellowiiformis (Zaklinskaja) Doweld 2018. The pollen is described, and its distribution along the section is shown. The maximum amount of the A. sellowiiformis pollen (up to 23.7%) is confined to the upper part of the Oligocene and the Lower Miocene and its last appearance is recognized in the Middle–Upper Miocene. These data expand our knowledge on the geographic range of the Cathaya ancestral form and its role in plant communities of Central Asia in the Cenozoic.

Abstract

In this study we describe a newly found frozen mummy of a young woolly rhinoceros (4–4.5 years old), dated to the Karginian Interstadial of the Late Neopleistocene (32 440 ± 140 years ago). The dimensional characteristics of this specimen are compared to those of 1- to 1.5-year-old juvenile, as well as adults, of Coelodonta antiquitatis found previously. Studies of the new find allowed to fill some of the information gaps concerning the features of the ontogenesis of the woolly rhinoceros, illustrate age-related changes in the color of its fur, and reveal a new anatomical peculiarity of C. antiquitatis—the presence of a fatty hump. Numerous remains of microscopic crustaceans were found in the wool, including representatives of the genus Moina (Cladocera: Moinidae), currently absent in the region. The latter were relatively common in Pleistocene temporary water bodies of Yakutia. The carcass of the rhinoceros was buried in a shallow (apparently temporary), fishless reservoir.

Abstract

The Chandler period of Mars is a new parameter determined from observational data that characterizes the properties of the planetary interior. Numerical modeling of the period of the Chandler wobble of Mars was performed for a number of internal structure models that satisfy not only geodetic data (moment of inertia, tidal Love number k₂), but also data obtained during a seismic experiment in the years 2019–2022. To reconcile the theoretical and observed values of the Chandler wobble, it is necessary to take into account the inelasticity of the mantle. To take into account the viscoelastic behavior of the interior, the Andrade rheological model was used. It is demonstrated how the value of the Chandler period depends on the rheological model parameters.

Abstract

In the study of the Khanmeikhoi Formation of the central zone of the Kharbei amphibolite–gneiss complex, it was shown that the amphibolites, schists, and plagiogneisses common here form two primary igneous series: low-alumina tholeiitic metabasalts of normal alkalinity and a differentiated series of high-alumina rocks from metatrachybasalts to metarhyolites with high alkalinity. According to the zoning of garnets, progressive and regressive branches of metamorphism are recorded, the peak conditions of which, according to calculations using the winTWQ program, correspond to the high-temperature stage of the amphibolite facies at high pressures (T = 690–750°C, P = 8.1–9.4 kbar). For the first time, metamorphic zircon from Grt-Bi plagiogneiss with low Th/U ratios of 0.01–0.04 and weakly expressed positive cerium (Ce/Ce* = 1.4–1.7) and negative europium (Eu/Eu* = 0.7–0.9) has been identified in the anomalies, the age of which, according to the results of the U–Pb LA-ICP-MS isotope method, is estimated to be Early Carboniferous (359–341 Ma). This time apparently characterizes the transition from the peak of metamorphism to the regressive stage associated with the exhumation of rocks. The results obtained indicate the formation of the Kharbei amphibolite–gneiss complex during the formation of the Ural orogen and allow us to consider it as an indicator of Paleozoic collision processes.

Abstract

The results of an analysis of the images of surface heat fluxes obtained from satellite microwave and infrared radiometric measurements in the areas of the origination of hurricanes in the Gulf of Mexico and tropical Atlantic are presented. It is stated that the intensity of the latent and sensible heat fluxes over 4–5 days preceding the origination of hurricanes increases and the fluxes are localized in certain areas—hurricane centers. The maximum values of the heat fluxes are reached simultaneously with the transition of tropical formations from the stage of a tropical storm to the stage of a tropical hurricane.

Abstract

In this study, the synthesis of poly(vinylidene fluoride) composite membranes incorporated with titania (TiO₂) nanoparticles and graphene oxide (GO) was demonstrated. The effect of GO on the surface morphology of the membrane was observed by scanning electron microscopy, indicating the typical membrane looseness and porosity caused by GO. The chemical properties and composition of the membrane were confirmed by X-ray diffraction and Fourier transform infrared spectroscopy, indicating the as-prepared membrane materials with reasonably doped TiO₂ and GO. The effect of the amount of doped GO on the microstructure and performance of the PVDF/TiO₂/GO membrane was systematically investigated. GO enhances the flux of the PVDF membrane in the early filtration stage and enhances the retention of pollutants. In addition, it was found that the synergistic filtration of large and small molecules improved the removal of small molecule contaminants. Therefore, the results of this study offered a new technology for the synergistic treatment of dye wastewater with macromolecule pollutants.

Abstract

The distribution of rare alkalis (Li, Rb, and Cs) is analyzed in spatially linked water objects of the Baikal geosystem: water of Baikal and its tributaries, underground water from boreholes and thermal springs, and the Angara River (the sole outlet), which are located in the Baikal rift zone. The rare alkali content differs significantly in some water objects, but the average and median contents are similar in the surface and deep water of Lake Baikal and the Angara River. The water of Barguzin thermal springs of the eastern shore of Lake Baikal contains the maximum amount of rare alkalis, but this affects the Baikal water insignificantly due to its natural self-cleaning and deep renewal of water during geodynamic movements. The similar rare alkali contents of Barguzin and some thermal springs of Kamchatka emphasize their indicator role in the genesis of water objects.