Zones of concentrated deformation (flower structures): field observations and modeling data

Abstract

Our study was focused on narrow linear zones that penetrate to different depths the crust and have complex infrastructure. Rocks in such zones are more intensively tectonically altered in comparison with the background. ‘Flower structures’ and ‘zones of concentrated deformation’ (ZCD) are the terms to describe these zones. The field study results combined with the data of tectonophysical and computational modeling data and supplemented by the literature analysis gave grounds for the following conclusions. In the experiments, as well as in nature, ZCDs show similar and, in some cases, identical morphological and infrastructural features and have similar stages of their evolution. A ZCD is mainly a reflection of the transpression setting. Its formation is accompanied by 3D plastic shear flow of matter and dilatancy of the deformed volume. A ZCD may be associated with the development of the ‘basement – cover’ system. It may also occur due to the intra-cover tectogenesis that does not influence the basement. Locations of ZCDs are spatially regular and predetermine the tectonic divisibility of the crust and lithosphere.

Deformation Regimes and Low-Rank Paleotectonic Stresses of the Western Tian Shan in the Mesozoic – Cenozoic

“…Следует отметить, что полученные результаты перестройки палеотектонодинамических обстановок с чередованием режимов «сжатий» и «растяжений» могут быть связаны с более сложными факторами, чем это постулируется как боковое латеральное давление, формирующееся при поступательном движении «литосферных плит». Последним также трудно объяснить наличие специфических линейных узких структур в виде шовных зон, которые в работе [Leonov et al, 2018] были отнесены к типу структур «цветка», образованных как следствие проявления «зон концентрированной деформации» ввиду несоответствия показателя ранга. Авторы этой работы отмечают, что зоны концентрированной деформации отражают преимущественно обстановки транспрессии и их формирование сопровождается 3D пластическим сдвиговым течением вещества и дилатансией деформируемого объема.…”

“…В структуре региона наблюдаются линейные узкие депрессии, выполненные платформенными отложениями юры -эоцена и альпийской молассой неоген-четвертичного возраста. Они представляются в качестве шовных зон и отнесены к типам структур, которые являются следствием возникновения «зон концентрированной деформации» [Leonov et al, 2018].…”

Structural evolution of the Earth crust of the East European platform: evidence from the Sarmatian plate. 1. Intra-plate tectonic and stages of the evolution of the Earth’s crust

“…During the era of platform activation, movements of blocks and their ensembles and lateral movements of rock massifs within their boundaries took place along the deformation grids (Goryainov et al, 2009;Timurziev, 2014;Kopp et al, 2017;Orlyuk, Ishchenko, 2019;Bartashchuk, Suyarko, 2018, 2020. The consequence of the manifestation of lateral movements is the tectonic flow of rock massifs and deformational structure formation, which led to the transformation of the original fracture-block structure of the Earth's crust into a folded-dislocated one (Chebanenko, 1977;Patalaha, 1979;Chikov, 2011, Kopp et al, 2017Leonov et al, 2018).…”

Unusual metasomatites (phyolithites) in the Kolvitskiy gabbro-anorthosite rock mass: composition and structural position

“…Thus, the Sredniye Ludy archipelago is the junction of the Riphean and probably Devonian grabens. It is the areas of rift deflections closure and the places where the inversion of structural-forming faults occurs (the so-called accommodation zones) that are characterized by the presence of areas of increased fracturing, pseudotachylites, dikes and metasomatites of various compositions, as well as increased concentrations of hydrocarbon emanations [9,25]. A characteristic feature of the framing of the Onega-Kandalaksha rift is conglomeratelike rocks of non-sedimentary genesis.…”

“…Fig.5. Electron microscopic images (BSE mode) of metasomatite (A), garnet with inclusions of chlorite, Muscovite-phengite, microcline (B) (b, dmode SE)Grtgarnet (light gray),points of analysis(1,8,9,33,34,36, 45, 46); Cpxclinopyroxene diopside (gray), (39-41, 49-51), Chl -chlorite (grey),(31,35, 38, 43, 47); Ampamphibole (gray), (6a, 7, 32); Sel -Ba-aluminoseladonite(white),(2,3,22); Ms -Muscovite-phengite (dark gray),(6,21,23,25, 37, 44); Btbiotite (gray), (1); Abalbite (black), (4, 42);Ananorthite (gray),(4,5,7,24); Kfsmicrocline (gray), (2); Ploligoclase (gray), (5а, 9а)…”