Ore Petrography, Mineralogical and Chemical Composition of New Iron Meteorite (Al-Sherqat Meteorite) from Iraq

The meteorite with a single total mass of 630 gm as a visible meteorite has fallen on 22 March 2021, at 10:00 a.m. in Al-Sherqat subdistrict within Salah Al-Din, northern Iraq; and therefore, was named Al-Sherqat meteorite by the authors. It is characterized by a uniform structure of coherent and medium degree of malleability. It is of a well-crystalline structure and not homogeneous in composition. The Al-Sherqat meteorite is composed of metallic phases of 7.6 gm/cm3 density exhibiting an oriented intergrowth of kamacite (α-FeNi) with taenite showing a Widmanstätten pattern on an etched polished section with the finest octahedrite kamacite bandwidth of less than 0.2 mm. It is composed of Fe (86.9 wt%), Ni (9.63 wt%), P (1.31 wt%), S (0.628 wt%), Ti (0.623 wt%), Co (0.446 wt%), Mo (0.146 wt%), Cr (0.103 wt%), Cu (0.141 wt%), V (300 ppm), Nb (220 ppm), W (53 ppm), Ag (50 ppm), Pb (30 ppm), Zn (20 ppm), Sb (16 ppm), Sn (10 ppm) and As (3 ppm). Al-Sherqat meteorite was structurally classified as an iron meteorite belongs to the plessitic group (Opl)) with octahedrite finest bands (less than 0.2 mm) of the kamacite lamellae. Kamacite platelets in Al-Sherqat meteorite are almost not a continuous plate network. Chemically, it belongs to the IIC type of magmatic group based on the amount of nickel (9.63%), where IIC is typically octahedrites has 9.3 – 11.5% Ni. The presence of kamacite, taenite, schreibersite, daubréelites, pentlandite, chromite, and wusite in Al-Sherqat meteorite are in accordance with IIC group of the iron meteorites. Al-Sherqat meteorite belongs to M-type considering a metallic core fragmented by impact asteroid. The most probable source of this meteorite is the core of an asteroid that melted early in its history.

Evolution of Subduction Cusps From the Perspective of Trench Migration and Slab Morphology

The geometries of trenches vary worldwide due to continuous plate boundary reorganization. When two trenches intersect to generate a corner, a subduction cusp is formed. Although subduction cusps are frequently observed throughout historical plate movement reconstructions, few studies have been conducted to explore the controlling factors of trench migration and slab morphology along subduction cusps. Here, we use a 3-D dynamic subduction model to explore the influence of the overriding plate strength, initial slab-pull force, and initial cusp angle on the evolution of subduction cusps. Our numerical model results suggest the following: 1) subduction cusps have a tendency to become smooth and disappear during the subduction process; 2) the slab dip angle is smallest in the diagonal direction of the subduction cusp, and a larger cuspate corner angle leads to a larger slab dip angle; 3) the asymmetric distribution of the overriding plate strength and initial slab-pull force determine the asymmetric evolutionary pathway of subduction cusps. Our results provide new insights for reconstructing the evolution of subduction cusps from seismological and geological observations.

Enhanced Quaternary Exhumation in the Central Three Rivers Region, Southeastern Tibet

The roles of tectonics and climate in the global increased erosion rates during the Quaternary have been the subject of active debate. The Three Rivers Region, strongly influenced by continental convergence between India and Eurasia and change in Asian monsoon climate, is an ideal place to study the interactions between tectonics and surface processes. Here we report new apatite (U-Th)/He data from an elevation transect that reveal a phase of rapid exhumation since ∼2.6 Ma in the Dulong batholith in the central Three Rivers Region, southeastern Tibetan Plateau. Based on stream profile analysis and compiled thermochronological data in the region, we demonstrate that the tectonic uplift caused by the high-strain at the corner of Indian-Eurasia convergence is responsible for the enhanced exhumation in the central Three Rivers Region in the Quaternary. Our new results highlight that the continuous plate convergence towards the plateau interior has dominated the uplift and deformation in the southeastern Tibet in the Quaternary.

Analysis of a 4-span continuous plate in one direction using Matlab programming

The present study presents a computer approach based on polynomial shape functions application for analysis of continuous plate in one direction using Matlab. A 4-span continuous plate in the x-direction comprises of boundary conditions SSSC, SCSC, SCSC and SCSS single panels’ plate was analyzed. It was assumed that, the external edges were simply supported while the internal edges of each panel were clamped. The bending moments of the clamped edges were calculated for each panel using appropriate boundary conditions which formed the fixed end moments (FEMs). Stiffness method was used based on beam analogy to analyze the continuous plate. Matlab codes were applied to develop a computer program for this analysis. To validate the results of this present study, the values of the moments obtained were compared with those of earlier studies using manual method. The percentage difference for fixed end moments were all 0.00% and that of support moments had the maximum value of 0.016%. Thus, it was concluded that the present study program based on Matlab is adequate and a faster approach for a 4-span continuous plate in one direction analysis. Keywords: Matlab Programming, Continuous Plate, Polynomial Shape Functions, Beam Analogy, Fixed Edge Moment.

Numerical solutions of the flexure equation

The 4th order differential equation describing elastic flexure of the lithosphere is one of the cornerstones of geodynamics, key to understanding topography, gravity, glacial isostatic rebound, foreland basin evolution and a host of other phenomena. Despite being fully formulated in the 1940’s, a number of significant issues concerning the basic equation have remained overlooked to this day. We first explain the different fundamental forms the equation can take and their difference in meaning and solution procedures. We then show how numerical solutions to flexure problems in general as they are currently formulated, are potentially unreliable in an unpredictable manner for cases where the coefficient of rigidity varies in space due to variations of the elastic thickness parameter. This is due to fundamental issues related to the numerical discretisation scheme employed. We demonstrate an alternative discretisation that is stable and accurate across the broadest conceivable range of conditions and variations of elastic thickness, and show how such a scheme can simulate conditions up to and including a completely broken lithosphere more usually modelled as an end loaded, single, continuous plate. Importantly, our scheme will allow breaks in plate interiors, allowing for instance, the creation of separate blocks of lithosphere which can also share the support of loads. The scheme we use has been known for many years, but remains rarely applied or discussed. We show that it is generally the most suitable finite difference discretisation of fourth order, elliptic equations of the kind describing many phenomena in elasticity, including the problem of bending of elastic beams. We compare the earlier discretisation scheme to the new one in 1 dimensional form, and also give the 2 dimensional discretisation based on the new scheme.We also describe a general issue concerning the numerical stability of any second order finite difference discretisation of a fourth order differential equation like that describing flexure where contrasting magnitudes of coefficients of different summed terms lead to round off problems which in turn destroy matrix positivity. We explain the use of 128 bit, floating point storage for variables to mitigate this issue.

ДОСЛІДЖЕННЯ ЕНЕРГОВИТРАТ ТАРІЛЧАСТИХ ЖИВИЛЬНИКІВ ДЛЯ СИПКИХ МАТЕРІАЛІВ

Creation of mathematical models that allow determining the relationship between the design and technological parameters of the plate feeders and the energy consumption arising during their operation. Methodology. The work uses the classical mechanics principles, the contact interaction of solids theory and the mathematical modeling method. Findings. The paper considers the design and operation principle of a continuous plate feeder, defines its main design and technological parameters. The factors that create mechanical loads on the drive of the feeder plate are investigated. Mathematical models have been developed that make it possible to determine the moments of resistance and the power consumed by an electric motor during the equipment operation. The proposed models make it possible to determine the load on the drive in static and dynamic operation modes and take into account the design, technological parameters of the equipment and the bulk material physical and mechanical properties. The study results of the friction coefficients influence, the knife position and the force of its pressing on the plate surface, the plate rotation speed on the loads acting on the electric drive are presented. It has been found that the drive calculation is expedient for the mode in which the distance between the knife edge and the rotation axis of the plate is maximum, which corresponds to the operation at maximum load. It has been determined that a change in the feeder technological parameters (plate rotation speed, knife position) can lead to a change in the load on the electric drive by 86%, which must be taken into account when choosing a drive. Originality. Mathematical models of the continuous plate feeder operation have been developed, which make it possible to determine the relationship between the design and technological parameters of the plate feeders and energy consumption. Practical value. The results obtained make it possible to determine the load on the plate drive by the known design, technological parameters and bulk material physical and mechanical properties.

Molecular mechanics of single layer graphene sheets

Получены наборы материальных и геометрических параметров силового поля DREIDING и балочного элемента, точно воспроизводящие механические модули графена в рамках стандартного метода ММ и метода МСМ. Эти методы реализованы в компьютерных кодах Pioner и MSC.Marc соответственно. Компьютерное моделирование частот и форм собственных колебаний однослойного графенового листа показало, что как частоты, так и соответствующие им формы собственных колебаний, полученные обоими методами, близки между собой, а также близки к частотам и формам колебаний почти квадратной сплошной пластинки, моделирующей ОГЛ. Sets of material and geometric parameters of the DREIDING force field and beam element, which accurately reproduce the mechanical modules of graphene in the framework of the standard MM method and the MSM method, are obtained. These methods are implemented in computer codes Pioner and MSC.Marc, respectively. Computer simulation of the frequencies and modes of natural vibrations of a single-layer graphene sheet showed that both the frequencies and the corresponding modes of natural vibrations obtained by both methods are close to each other, as well as close to the frequencies and modes of vibration of an almost square continuous plate simulating a single-layer graphene sheet.