No 2 (2025)
- Year: 2025
- Articles: 5
- URL: https://journals.eco-vector.com/0016-853X/issue/view/13665
- DOI: https://doi.org/10.31857/S0016-853X20252
Full Issue
Articles
A Giant Quasi-Ring Mantle Structure Beneath the Eastern Mediterranean: Interpretation of New Seismic-Tomography, Magnetic Field, and Paleobiogeographic Data
Abstract
In the presented article, a quantitative reinterpretation of the residual satellite gravity anomaly is carried out. Additional necessary confirmation is provided by the distribution of anomalies in the regional magnetic field ΔZ, reduced to a height of 2.5 km above sea level. Based on the analysis of detailed paleomagnetic studies, the average rotation rate of the surface projection of the deep structure over the past 70 million years is estimated at about 18 mm/year. The authors constructed a paleobiogeographic map showing the counterclockwise displacement of the typical Ethiopian fauna to the northwest. The influence of the rotating deep structure on stress in the overlying blocks of the Earth’s crust and lithosphere before the catastrophic earthquakes with magnitudes M=7.9 and M=7.8 that occurred on 06.02.2023 in Turkey is shown. The synthesis of seismic tomography profiles made it possible to construct a seismotomographic scheme of the location of the deep structure. This scheme agrees with the analysis of satellite gravity and marine/terrestrial gravity studies, geoid anomalies, magnetic anomaly distributions, paleomagnetic data, regional GPS vector directions, seismological and tectonic-structural, and mineralogical-petrological data. The integrative combination of all these factors is indisputable to confirm the existence of an anomalous deep rotating structure beneath the Eastern Mediterranean and adjacent regions.
3-31
Evolution, Geodynamics and Morphology of the Lentis-Shaped Extension Zones of Transform Faults: Comparative Analysis and Kinematic Model
Abstract
The article presents a new type of morphostructural objects defined by the author, these are intra-transform lens-shaped extensions confined to active troughs of transform faults. A morphostructural analysis is carried out using geophysical data. It has been revealed that such structures are formed in active zones of transform faults with the maximum offset of the segments of the mid-oceanic ridge. A classification of intratransform lenticular extension zones was carried out, according to which types I‒III of morphostructures were identified, which illustrate not only various evolutionary stages, but also various kinematic scenarios. Type I is a lenticular area. This type includes small young (<10 Ma) lenticular extension zones of the local level, occurring mainly in the transform fault of the southern hemisphere. Type II is a lenticular transformed basin. It is a lenticular formation at the regional level with a large (~100 – ~300 km) offset formed on a large transform fault with a block of highly deformed lithosphere in the axial part of the lens and the implementation of shear movements along one of their fringing arc troughs, but without internal spreading segments. Type III is a multitransform lenticular system. This is a global level lenticular formation, located on a large transform boundary with extreme offset, limited by passive arc-shaped ledges and enclosed between them by several closely spaced transform trough valleys and internal spreading zones. A kinematic model is constructed for I‒III identified types of morphostructures in accordance with the classification of intratransform lenticular extension zones.
32-53
Structural signs of brittle-ductile transitions during exhumation of basement rocks of Southwestern Forland of the Paleoproterozoic Lapland‒Cola Collision Orogen (the White Sea Region, Lyagkomina Dam Site): Analogue modelling of deformation stages
Abstract
The Late Paleoproterozoic structural evolution of Archean polymetamorphic rock complexes at the Lyagkomina Dam site, located in the central part of the White Sea region, has been studied. Four stages of deformation were identified using methods of geological-structural mapping and geometric analysis. Under conditions of regressive metamorphism from granulite to amphibolite facies, at each stage of deformation, the properties of rocks change from plastic to predominantly brittle. It is shown that the Paleoproterozoic structural evolution is associated with the exhumation of a fragment of the continental crust of the central part of the White Sea region during the formation of the Lapland-Kola collision orogen.
54-67
The Transverse Structural Zoning of the Lower Cambrian Uda‒Vitim Island-Arc System (Western Transbaikalia, Russia)
Abstract
The new petrochemical data on the Lower Cambrian volcanites of the Oldynda Formation of the Uda-Vitim island-arc system are presented. The high level of REE content, the high degree of spectrum light part differentiation, enrichment in large-ion lithophile elements, and Nb-minimum presence in the studied volcanites were analyzed, confirming their island-arc origin. Transverse structural zoning of volcanites in the cross-strike of the Uda-Vitim island-arc system was determined. For the first time the structural zoning has been traced by the degree of volcano differentiation, as well as by the mineral and chemical rock composition. The depths of the mineral subduction zone have been calculated. It as assumed that this zone is located in the area of the Eravna lakes within the Eravna structure, what is confirmed by a large gravity stage of northeastern strike.
68-87
Structure and Petrological-Geochemical Characteristics of Rocks of the Kabak-Taiga Ophiolite Complex of the Altai-Sayan Folded Region (Mountain Altai)
Abstract
The Kabak- Taiga ophiolite complex is represented by serpentinite melange, including blocks of gabbro- pyroxenite-ultramafic and gabbro-d iabase, intruded by leucoplagiogranite dikes. The melange is located at the base of the accretionary complex composed of tectonic sheets of basalts and rhythmically layered terrigenous and siliceous rocks altered in the greenschist facies of metamorphism. It was revealed that the gabbro- diabases belong to low-titanium tholeiites, the leucoplagiogranites are calcic and belong to M-type granites, and the basalts belong to moderately alkaline high-titanium volcanics. The microelement composition of the gabbro-d iabases and basalts, as well as features of the composition of chrome- spinelides from ultrabasic rocks, indicates their formation during spreading in the rear of the island arc. The set of new geological and petrological- geochemical data obtained on the rocks of the Kabak-T aiga ophiolite complex and basalts of the accretionary complex allows us to combine them into a single ophiolite association. Together with the ophiolites of Southern Tuva, they represents the Vendian-C ambrian back-arc basin of the Tannuol island arc, fragments of which have been preserved in the Early- Middle Paleozoic Charysh- Terekta- Ulagan-S ayan suture- shear zone. The new data obtained are an important aspect in substantiating the geodynamic nature of the global suture- shear zone dividing the Altai- Sayan folded region into two large tectonic segments represented by collisional and accretionary orogens on the southern framing of the Siberian paleocontinent.
88-112