S.О. Zorina *, K.I. Nikashin **, N.I. Afanasieva ***, N. Hamada ****
Kazan Federal University, Kazan, 420008 Russia
E-mail: *svzorina@yandex.ru, **kostya97@inbox.ru,
***n-afanasieva@rambler.ru, ****nadia.m.hamada@gmail.com
Received August 4, 2022; Accepted November 15, 2022
ORIGINAL ARTICLE
DOI: 10.26907/2542-064X.2023.2.295-307
For citation: Zorina S.О., Nikashin K.I., Afanasieva N.I., Hamada N. Surface microtextures of quartz grains and origin of the paleogene sands in the Ulyanovsk-Syzran Volga Region. Uchenye Zapiski Kazanskogo Universiteta. Seriya Estestvennye Nauki, 2023, vol. 165, no. 2, pp. 295–307. doi: 10.26907/2542-064X.2023.2.295-307. (In Russian)
Abstract
Quartz grains were separated by standard sieving of the Paleogene sands from the Sosnovka Formation of the Ulyanovsk-Syzran Volga region, which are a scarce and valuable raw material for glass making and construction. In order to establish the origin of the sands and restore the facies conditions of their formation, the surface microtextures of the separated quartz grains were examined by optical and electron microscopy. It was shown that the clastic grains of the Sosnovka sands bear the signs of a multi-stage formation process under the conditions of subaquatic (beach zone), eolian, mixed subaquatic-eolian (coastal dunes), injective, and continental pedological settings. For the first time, a complex of microtextures characteristic of the extrusion of grains from deep horizons under pressure and inherent in the injection mechanism of sand formation was described. The diagnostic complex of injectites includes rotational microtextures, notched microtroughs, and deformed fluid inclusions. The rather fresh appearance of the listed microtextures suggests that they were superimposed on the coastal-marine and eolian stages of the evolution with the subsequent formation of sand intrusions. At the final stage of the geological history of the Sosnovka sands, the grains were shaped by the continental pedological conditions, when secondary silica in the form of globules and their clusters cemented the quartz grains, the surface of which concatenated the features of the previous stages. Based on the results of the study, an interpretation scheme summarizing various microtextural features of the reconstructed paleoenvironments and the stages of formation the Sosnovka sands was developed. The finding that the Sosnovka sands are sand intrusions is of great practical importance, as it necessitates new approaches to the discovery and prediction of glass and quartz sand deposits confined to the Paleogene Sosnovka Formation of the Ulyanovsk-Syzran Volga region.
Keywords: microtextures, grains, sands, Sosnovka Formation, Paleogene, Ulyanovsk-Syzran Volga region, Russian Platform
Acknowledgements. This study was supported by the Russian Science Foundation (project no. 22-27-00070, https://rscf.ru/project/22-27-00070/).
Figure Captions
Fig. 1. Location of the Eastern Tashlinsky and Kuchurovsky quarries on the geographical (a) and general geological (according to Lichman, 1968f) (b) maps; lithological composition of the upper part of the Sosnovka Formation in the Eastern Tashlinsky (c) and Kuchurovsky (d) quarries and the sampling sites.
Fig. 2. SEM images of Sm-1 grains, fraction < 0.16 mm: a) well-rounded grain with a smooth surface and a fresh sickle-shaped dent (1); b) medium-rounded grain with a rough surface and V-shaped impact pits (2). Micrographs of Sm-2 grains; c) semi-rounded grain with a rough surface, as well as multiple sickle-shaped splits (1) and impact fractures (3). Fraction 0.315–0.63 mm; d) poorly rounded grains with slightly rough surfaces, convex edges, as well as smoothed dents and conchoidal chips. Fraction 0.16–0.315 mm.
Fig. 3. a) SEM image of a fragment of the medium-rounded grain with clusters of silica globules in the dents and troughs. Sm-2 sample, fraction 0.63–1.25 mm; b) micrograph of small-sized quartz grains cemented by secondary silica. Kuch-1 sample, fraction 0.63–1.25 mm.
Fig. 4. Rotational microtextures characteristic of injectites. Kuch-1 sample: a) SEM image of a grain with the traces of stepped indentation and rotation of a smaller grain; b) micrograph of the matt surface of a grain with parallel sickle-shaped impact dents (dotted oval) and a rotational microtexture (dotted rectangle); c) enlarged fragment of the grain surface with a rotational microtexture. The direction of indentation (1), rotation (2), and movement (3) of a small grain is shown with the arrows.
Fig. 5. Microtroughs as indicators of the injection mechanism: a) SEM image of a well-rounded grain with unidirectional microtroughs (1) and stepped sickle-shaped dents (2); b) micrograph of a semi-rounded grain with parallel trough-like grooves on a smooth hummocky and pitted surface. Kuch-1 sample, fraction 0.315–0.63 mm; c) enlarged fragment of the microtroughs with small notches along the sides (2). The movement of “scratching” grains in shown with the arrows.
Fig. 6. Internal deformations of the fluid inclusion. Kuch-1 sample, fraction 0.63–1.25 mm. Fractures around the inclusion coinciding with the direction of the grain squeezing are shown with the arrows.
References
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