Doklady Earth Sciences

Petrov, O. V.; Ryabchuk, D. V.; Sergeev, A. Yu.; Budanov, L. M.; Zhamoida, V. A.; Neevin, I. A.; Taldenkova, E. E.; Prishchepenko, D. V.; Nosevich, E. S.; Pushina, Z. V.; Grigoriev, A. G.; Bashirova, L. D.; Ponomarenko, E. P.

doi: 10.1134/s1028334x23601657pmid: N/A

The paper deals with results of geological and geophysical study of the East Siberian Sea coastal areas are reported. Research activities started in 2018 in the frame of the State Geological Mapping Project (GK-1000/3) and continued in 2022 under support of the Russian Science Foundation. A seismo-stratigraphic scheme of the Quaternary sediment sequence has been compiled, and a conception of the paleogeographical evolution in the Late Pleistocene–Holocene has been proposed.

Degtyarev, K. E.; Luchitskaya, M. V.; Tretyakov, A. A.

doi: 10.1134/s1028334x23601712pmid: N/A

The complex of felsic to intermediate volcanic rocks intruded by plagiogranitic bodies is first revealed in the western part of the Tekturmas ophiolite zone of Central Kazakhstan. The U–Pb (SIMS) geochronological study of one of the plagiogranitic bodies dated back to the Early Cambrian (537 ± 5 Ma) is conducted for the first time. The peculiarities of the volcanic rocks and the composition of plagiogranites indicate their formation in a suprasubduction setting within the Early Cambrian primitive volcanic island arc. The formation of this arc was not related to the evolution of the Ordovician oceanic structures, the complexes of which participate in the structure of the Tekturmas zone.

Skolotnev, S. G.; Fedonkin, M. A.; Korniychuk, A. V.

doi: 10.1134/s1028334x23601736pmid: N/A

The age of magmatic rocks of basic composition sampled at the Alpha–Mendeleev Rise in the Arctic Ocean by a research submarine was studied based on the measurement of the U/Pb age of zircons separated from them. Early Cretaceous rocks of the moderately alkaline series, which had been formed at the turn of 112 million years, are most common on the Rise. These rocks contain a large number of ancient xenogenic zircons the age analysis of which shows that the subalkaline melts interacted with the crust at two levels including the horizon of Early Cretaceous sandstones and with rocks of the Late Archean crystalline basement aged 2675.1 ± 11.6 Ma. They also contain a small number of younger zircons aged 83 to 87 Ma, which probably arose during the recrystallization of Early Cretaceous zircons under the influence of Late Cretaceous magmatism.

Biakov, A. S.; Vedernikov, I. L.; Goryachev, N. A.; Gareev, B. I.

doi: 10.1134/s1028334x23601724pmid: N/A

A detailed record of the δ13Сorg value has been obtained for the first time in Permian mudstones of the Taskan Basin (Omulevka Block, Northeast Asia) covering the interval from the Upper Kungurian, Roadian, Wordian, Capitanian, and Lower Wuchiapingian stages. The value of δ13Сorg varies from –23.81‰ (mid-Kungurian) to –26.97‰ (lower Wuchiapingian). Three δ13Сorg negative excursions were clearly distinguished in the section including the upper part of the Kungurian Stage of the Lower Permian, the lower part of the Capitanian, and the boundary between the Capitanian and Wuchiapingian stages. These excursions are in good agreement with the episodes of mass extinction that we established earlier [12], and they are most likely associated with periods of activity of island-arc magmatism in the region during the Permian.

Alexeiev, D. V.; Rojas-Agramonte, Y.; Tretyakov, A. A.; Gerdes, A.

doi: 10.1134/s1028334x2360189xpmid: N/A

In the present contribution, we aim to better constrain the age of the oldest arc-related volcanic units in the North Tianshan of Kyrgyzstan (NTS) in order to improve our understanding of the early evolution of subduction systems in the western part of the Central Asian Orogenic Belt. We conducted zircon U–Pb dating (LA-ICP-MS) on andesitic tuffs from the Sultansary and Tashtambektor formations, which were previously believed to be of early Cambrian and middle Cambrian to early Ordovician age, respectively. The results reveal ages of 491 ± 3 and 487 ± 3 Ma for these formations, indicating that both units are of Late Cambrian age. We conclude that these volcanic rocks belong to a major magmatic arc that evolved on a heterogeneous basement in the NTS during the Late Cambrian and Early Ordovician.

Ebrahimi, Karamat; Pourkermani, Mohsen; Almasian, Mahmud; Bouzari, Soheila

doi: 10.1134/s1028334x23600755pmid: N/A

Zarrindasht County is a county in Fars Province in the south of Iran. This county is located between the folded parts of Zagros. In this area, there are many anticlines and synclines. The present study was performed to assess active tectonic using morphometric indices for the Zarrindasht area (South of Iran). In these studies, the topographic map of the Zarrindasht area, scale 1 : 50 000 and different satellite images were utilized to evaluate the morphometric features of the study area and to measure morphometric indices. Also, information related to lithology, faults, and other geological parameters was obtained from the geological map of the Zarrindasht area, scale 1 : 100  000. A total of 4 geomorphic indices such as the Mountain-front sinuosity index (Smf), drainage basin shape index (Bs), hypsometric integral index (Hi), and the ratio of valley-floor width to valley height (Vf) were studied in the selected locations. The results of these studies showed that most regions of the study area are moderate in terms of tectonic activity. So, in all of these basins, tectonic activity is more than erosion. The final result of the analysis of geomorphic indices showed that in the basins that have high and moderate tectonic movements, there are fault valleys, alluvial fans of the fault mountain front, fault escarpments, etc. Also, the formation of these shapes is affected by the active tectonics in the region.

Zolnikov, I. D.

doi: 10.1134/s1028334x23700526pmid: N/A

The problem of differentiation and correlation of the Upper Quaternary sediments comprising the valleys of the main rivers in Western Siberia (primarily the Ob and Yenisei) was actively discussed in the second half of the 20th century and has not been solved conclusively at the end of the first quarter of the 21st century. Traditionally, the regional Quaternary history of the river valleys was considered as the “terrace staircase” paradigm, under which, in the Neogene–Quaternary, alluvial terraces formed sequentially from the older upper to the younger lower ones. Neotectonics, paleoclimate dynamics that changed the water abundance of the rivers, sea transgressions and regressions that affected the erosion base level, and frequent blocking of river valleys by northern glaciers leading to the formation of dammed lakes and the periglacial alluvium in the extraglacial zone were considered to be the factors that controlled their formation. However, the heights, age, and even the number of terraces differ significantly not only in the published works, but also on the official maps of Quaternary deposits. Significant data have been accumulated that contradict the concepts about a vertical staircase of successively downcut cycloclimatic terraces and periglacial alluvium facies that replaced the glacier-dammed northern lakes in the southern part of Western Siberia. A refined concept of the sediment structure in the Upper Neopleistocene in the main valleys of this region that takes into account the data on three glacier outburst floods from intermountain basins to the plain has been formulated and substantiated. The intense erosional and accumulative activity has continued to be underestimated.

Rudko, D. V.; Rudko, S. V.; Shatsillo, A. V.; Latysheva, I. V.; Kolesnikov, A. V.; Fedyukin, I. V.; Pokrovsky, B. G.

doi: 10.1134/s1028334x23601827pmid: N/A

A cyclostratigraphic study of the Late Precambrian Zhuya Group (Nikolskoye and Chencha Formations), and Torgo formation in the southern part of the Siberian Platform was carried out to determine the duration of the C-isotope anomaly imprinted in them. The similarity of the ratios of the period lengths of the cyclic components of the magnetic susceptibility in the coeval deposits of the remote sections of the Nikol’skoye and Torgo Formations indicates the connection between the revealed cyclicity and the basin-scale environment changes. According to the astrochronological model, the duration of the formation of the studied intervals of the Nikol’skoye (57 m) and Chencha (147 m) formations was 850 and 2500 ky, respectively. Extrapolation of the data obtained shows that the duration of the C-isotope anomaly of the Zhuya Group in the Vendian reference section on the Ura uplift was about 10 My, which is consistent with most estimates of the Shuram anomaly’s duration and its stratigraphic analogues.

Rasskazov, I. Yu.; Gurman, M. A.; Shcherbak, L. I.

doi: 10.1134/s1028334x23601748pmid: N/A

The material composition and structural and textural features of porphyry–copper–gold ore reflect the conditions of ore formation and are of decisive importance for predicting the technological properties of ore and for improving the integrated approach to using mineral raw materials. A sequence of ore formation is presented, in which three stages were singled out within the studied interval of the ore body including the greisen stage, the sulfide (productive) stage, and the stage of explosive microzones. The features of ore and of ore-forming minerals which determine their flotation behavior and the properties that affect flotation activity were identified. The complex composition of the studied ore was established.

Letnikova, E. F.; Zhdanov, A. A.; Ivanov, A. V.; Maslov, A. V.; Izokh, A. E.; Letnikova, A. F.; Soloshenko, N. G.

doi: 10.1134/s1028334x23601694pmid: N/A

The Sr-isotopic composition in carbonate rocks aged 980–920 Ma has been defined in only one place in the world, the Huainan Formation of the North China Platform, with the accumulation time limited by U–Pb data of detrital zircon grains. The upper part of the Nizhny Tunguska Formation in the Turukhansk uplift is found to contain altered volcanic rocks, as well as weathering crust products along them, such as poor bauxite and chamosite ores, among carbonate deposits. Based on U–Pb zircon isotope dating, the age of the volcanic rocks is 963 Ma. For the least altered limestones in the upper part of the Nizhny Tunguska Formation, the 87Sr/86Sr values were obtained equal to 0.70532–0.70578, which are close to those found in the rocks of the Huainan Formation. These data about the geochronological age of the studied limestones make it possible to obtain more accurate data, which allows refining the previously proposed configuration of the Sr-isotopic composition variation curve in the Early Neoproterozoic. The Nizhny Tunguska Formation compares favorably with the Huainan Formation in being the world’s only Early Neoproterozoic carbonate sequence that is correctly geochronologically substantiated (based on zircon from subsynchronous volcanic rocks).