2.5 dimensional model of mantle heterogeneities under the Ukrainian shield according to the gradients of the velocities of seismic waves

Shumlianska, L.O.; Dubovenko, Y. I.; Pigulevskyy, Petro H.

doi:10.15421/112039

Cited by 6 publications

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“…Data from seismic tomographic kinematic meth ods was used to recalculate data on Pwave velocities in the mantle beneath the Ukrainian Shield [6]. Pwave velocities data served to determine seismic boundaries in the mantle us ing the first derivative of the Pvelocity depth curve, v p (z) [7]. Each of these curves represents a distinct mantle domain lo cated beneath the Ukrainian Shield.…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional density model of the mantle beneath the Ukrainian shield

Shumlianska,

Pigulevskiy,

Vilarrasa

2024

Nauk. visn. nat. hirn. univ.

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Purpose. Mantle density models are key tools for understanding the fundamental geological and physical processes occurring within the Earth and are essential to our scientific and applied understanding of the planet. Methodology. The tasks were solved by a complex research method, including analysis and generalization of literary and patent sources, analytical, experimental studies, using computer and mathematical modelling methods. Findings. One-dimensional models simplify the mantle density distribution by assuming that it is uniform only in the vertical direction. This limitation does not allow for horizontal variations in mantle density, which may be important on a regional scale. 3D models are more complex and require more data and computational resources, so their use may be limited. In this study, we present a quasi-three-dimensional model of mantle density beneath the Ukrainian Shield. This 3D model is obtained using a basic set of one-dimensional seismic tomographic velocity models calculated for 21 mantle domains in the depth range from 50 to 2,600 km. The process of converting the P-wave velocity model into a density model includes the following stages: 1) determining seismic boundaries in the mantle based on P-wave velocity curves for each mantle domain; 2) creating a synthetic mantle model beneath the Ukrainian Shield for the P,S-wave velocity curves; 3) solving the Adams-Williamson equation for each domain, considering polynomial corrections to extract heterogeneities during its solution; 4) analysing existing models by comparing the calculated gravitational potential at the central point of the Ukrainian Shield as the standard reference for selecting one of 5 reference models. Here, we focus on the final stages of constructing the mantle density model by: 1) balancing the mass of the upper and lower mantle for each domain when determining density using the Adams-Williamson equation and introducing polynomial corrections; 2) calculating densities for each of the 21 mantle domains and their 3D integration. Originality. The obtained mantle-density model of the Ukrainian Shield aligns well with the division of the mantle into three main layers: lithosphere, upper mantle, and lower mantle. Each of the mantle’s structural layers has its representation pattern in density heterogeneities. Anomalies of decreased density in the lithosphere of the Ukrainian Shield correlate with thermal anomalies, whereas anomalies of increased density correspond to tectonic zones dividing its megablocks. Practical value. Regions of increased density gradient are associated with mantle thrust faults, which in some cases can be boundaries between different petrological formations and serve as channels for magma ascent into the Earth’s crust at certain stages of geological development of the Ukrainian shield and, in turn, be sources of minerals.

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Section: Introductionmentioning

confidence: 99%

“…In turn, the isoline pitch directly depends on the resolution of the seismic tomography method, i.e., on the Fresnel zone's size. It has been shown that for the upper man tle, the resolution of the method is 30 km, and for the lower mantle it is 50 km [7].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional density model of the mantle beneath the Ukrainian shield

Shumlianska,

Pigulevskiy,

Vilarrasa

2024

Nauk. visn. nat. hirn. univ.

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“…Методика визначення опорних (реперних) точок значень густини. У нашій роботі (Shumlianska et al, 2020) докладно описано метод отримання сейсмічних границь по перегинах перших похідних швидкісної кривої та наведено результати для мантії під УЩ. Ці дані можуть бути використані для визначення опорних точок (сейсмічних границь) для створення матриці реперних значень густини, узятих із точок, найбільше просторово близько розташованих до референтної моделі, що отримані із зіставлення швидкісних кривих -експериментальної та теоретичної (для референтної моделі).…”

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“…• дані щодо глибин сейсмічних границь, що відповідають нашим координатам, розраховані у роботі (Shumlianska et al, 2020);…”

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Application of Polynomial Corrections to Construct an Optimal One-Dimensional Density Model of the Mantle

Shumlianska¹,

Pigulevski²

2022

VKNUGEOL

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In this work, an optimal one-dimensional density model was obtained, corresponding to the velocity curve for one of the mantle domain under the Ukrainian shield. When obtaining a one-dimensional density model, only the Earth's mass and seismic velocities are known physical parameters. The density is obtained by solving the Adams-Williamson equation, the use of which is possible under the assumption that the density is created only by the weight of the upper layers, with a homogeneous composition of the mantle. Some approximation to the real density distribution gives a seismic parameter that scales the obtained densities in accordance with the geometry of the seismic velocity distribution, while, as shown by our studies, the obtained density values are not absolute, but only an approximation corresponding to the equation is used. In order to obtain a density distribution we transform the first approximation obtained from the Adams-Williamson equation. This paper shows several options for transformation; based on the arithmetic mean correction for 5 reference mantle models (PEMC, PEMA, PREM, AK135, IASP91); using control points representing seismic boundaries to determine the intervals for computation of density using the Adams-Williamson equation; when introducing corrections in the form of the difference between the polynomials for the theoretical density curve and that obtained by the Adams-Wilmson equation for the IASP91 model. The density curve obtained by the last method is not distorted by the introduced density jumps from the IASP91 model, correspond to positions of seismic boundaries along the inflections of the P-velocity curve. The density curve obtained from the Adams-Williamson equation is transformed into a curve that is as close as possible to the geometry of the inherent curve seismic velocity of P and S waves. In our opinion, the density curve obtained using the difference polynomial shows the most approximate solution to the optimal density model for a given seismic velocity distribution, in our case, for the mantle domain under the Ukrainian shield with center coordinates 28.25Å 49N.

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Geodense section of the lithosphere of the Ukrainian shield along the Shepetivka – Zhytomyr – Dnipro – Volnovakha traverse

Pigulevskiy,

Shumlianska

2024

IOP Conf. Ser.: Earth Environ. Sci.

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Based on the results of transformation of one-dimensional density models using polynomial corrections to reference model AK135 for different domains of mantle of the Ukrainian Shield, a preliminary reconstruction of the Earth’s geodensity structure to depth of 2600 km was performed. The one-dimensional density models are properly correlated with gravitational field and mass of each mantle layer. Based on these constructions, the integration of the horizontally layered model with seismic stratigraphy data and the vertically block model with gravity field calculations to depth of 275 km along the Shepetivka-Zhytomyr-Dnipro-Volnovakha geotraverse was carried out. The results significantly increased the informativeness of data from two methods regarding the features of deep lithospheric tectonics within the Ukrainian Shield. The results of geological interpretation along the geotraverse show that the megablocks of the shield are best reflected in density anomalies, characterized by different densities both horizontally and in depth. The obtained features of the lithospheric structure of the Ukrainian Shield indicate the need for further research of upper and lower mantle to obtain a comprehensive interconnected model of its structure to refine the petrophysical characteristics that affect the formation of the Earth’s crust and mineral resources.

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2.5 dimensional model of mantle heterogeneities under the Ukrainian shield according to the gradients of the velocities of seismic waves

Cited by 6 publications

References 0 publications

Three-dimensional density model of the mantle beneath the Ukrainian shield

Three-dimensional density model of the mantle beneath the Ukrainian shield

Application of Polynomial Corrections to Construct an Optimal One-Dimensional Density Model of the Mantle

Geodense section of the lithosphere of the Ukrainian shield along the Shepetivka – Zhytomyr – Dnipro – Volnovakha traverse

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