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Isotopic dating of the authigenic sanidine mineralization in the Lower-Upper Carboniferous rocks, southern Moscow syneclise. Morphotypes of the authigenic sanidine: (1) fine-crystalline aggregates, (2) authigenic fringes of the zoned grains; (3) schematic drawing of sections and sampling levels. All age values are given in Ma.
Source publication
The article presents data on numerous findings of authigenic K-feldspars in the Lower-Upper Carboniferous carbonate and terrigenous rocks in the southern limb of the Moscow syneclise, including the Oka-Tsna bar. In terms of the composition and crystalline structure, all feldspar morphotypes (idiomorphic monocrystalline fringes on the surface of san...
Citations
... The final stage of phosphate mineralization can be reconstructed taking into account the following fact: phosphatization was associated with the long-term impact of acid colloidal solution on rocks of the pre-Oxfordian paleovalley. Carboniferous rock sections studied near the Tuchkovo Settlement suggest that the Carboniferous limestone sequence eroded by the Bajocian-Bathonian paleoriver was relatively enriched with authigenic sanidine (Yashunskii et al., 2020). Judging by the currently known size of its grains, this mineral should be present in the psammite fraction of the Bajocian-Bathonian and Callovian rocks of the paleovalley. ...
... The presence of sanidine in the calcite skeleton of sponges is determined by its widespread occurrence in carbonate and terrigenous deposits of the Lower, Middle, and Upper Carboniferous in the southern part of the Moscow Syneclise (Yashunsky et al., 2017(Yashunsky et al., , 2018(Yashunsky et al., , 2020. In the Gzhelian Quarry, sanidine was identified (Yashunsky et al., 2016) in fine-grained limestones of the Noviy Milet Formation of the Dorogomilovian Horizon of the Kasimovian Stage, which occur at the base of the section (Fig. 2, bed 1). ...
... According to isotope dating by 40 Ar/ 39 Ar analysis, the age of this mineral falls within the range of 286 to 251 Ma, which corresponds to the second half of the Cis-Urals, Biarmian, and Tatarian epochs of the Permian period. The source of K-containing solutions was the highly mineralized brine of Permian evaporite marine basins, the temporary transgression of which covered the southern part of the Moscow Syneclise (Yashunsky et al., 2020). ...
A new genus and species of hypercalcified calcareous sponge, Gzhelistella cornigera gen. et sp. nov., is described from the Kosherovo Formation (Gzhelian Stage) of the Moscow region. The new genus is the first representative of hypercalcified calcareous sponges from the Upper Carboniferous with an “inozoanlike” internal structure and a characteristic spicular organization of the skeleton.
... It will be shown below that clay beds that do not contain pyroclastic components are composed of palygorskite, and this feature is characteristic of carbonate sediments within the studied stratigraphic interval. Other char-acteristic representatives of authigenic minerals are finely crystalline K-feldspar, which formed, according to isotope dating, in the Permian (Yashunsky et al., 2020), as well as dolomite and pyrite. ...
Traces of extremely powerful explosive volcanic eruptions are documented in the southern Moscow Syneclise; the eruptions occurred in the Moscovian Age about 309 million years ago in Variscan orogenic regions adjacent to the East European Platform. Interbeds of altered volcanic ash, 5–15 cm thick, can be traced over the distance of tens of kilometers in the sediments referring to the Podolskian and Myachkovian substages of the Moscovian Stage. These interbeds are composed of calcareous clays of montmorillonite composition and contain grains of zircon, apatite, ilmenite, biotite, K-feldspar, and quartz. Two types of K-feldspar (authigenic and volcanic) referring to the sanidine group are identified. U–Pb SIMS dating of pyroclastic zircons from the tuffaceous bed at the boundary between the Podolskian and Myachkovian showed an age of 308.9 ± 2.3 Ma, and 40Ar/39Ar dating of volcanic sanidine at a higher level showed the age of 305.5 ± 2.7 Ma, which agrees well with the available age estimates for the stage boundaries in the Pennsylvanian. Analysis of the Late Paleozoic volcanism in the nearby regions showed that the most likely area where catastrophic explosions took place, with subsequent transportation of volcanic ash to the southern Moscow Syneclise, is the zone of the North Caucasus.
The Shulepovo refractory clay deposit was discovered in the 1970s. It consists of subhorizontal kaolinite lenses located at different depths (1–20 m) in a clay–sand sequence tentatively assigned to the Neogene or, possibly, Late Pliocene (?). Application of the X-ray diffraction method coupled with the UV-VIS-NIR spectroscopy established an almost monomineral composition of lenses, with a minimal (not more than 5%) content of quartz, as well as admixture of halloysite and mixed-layer smectite–vermiculite. Calculation of the Hinckley index (HI) for kaolinite revealed a high ordering degree, suggesting its mainly authigenic origin. The bulk chemical composition of kaolinite samples is close to that of pure kaolinite, with an insignificant (not more than 2%) Fe and Ti. Zonation in the chemical composition alteration was not detected within the lens. Studies of the host sand–clay sequence revealed that it can be assigned to the alluvial (channel and oxbow) facies. The formation model of kaolinite lenses in the Shulepovo deposit includes the following processes: major transformations of the terrigenous–clastic kaolinite in stagnant waters, its crystallization, and formation of the authigenic kaolinite due to the decomposition of the clastic aluminosilicate minerals in a chemically aggressive medium.
