Rocks Of Complex Research Articles

Use of Electrical Resistivity Tomography for Joint Geophysical and Geotechnical Landslide Characterization: A Case Study

Abstract Slope movement processes include complex soil and rock failure mechanisms. Their study benefits from a multidisciplinary approach based on a wide range of information including geological and geomorphological mapping, and geotechnical and geophysical investigations. This research paper focuses on the characterization of the Tamentout landslide that occurs in the southeast of Jijel province. The study area belongs to the Tellian domain in which the geological outcrops are dominated by Senonian formations, composed of marl deposits overlain by Numidian flysch of Aquitano-Burdigalian age, with a sloping topography ranging from 20° to 30°. The geophysical approach consists of processing the available geophysical data of resistivity, obtained by the Electrical Resistivity Tomography (ERT). This study aims to characterize the internal structure, and the changes in water saturation within the unstable mass and locate the depth of slip surface associated with this landslide. Through this work, we combined geological and geotechnical investigations with electrical resistivity tomography (ERT). This combination gave a more detailed image of the substrate geology and structure of the landslide zone. The 2D resistivity results show that the basement consists of two main formations. The first one is a highly conductive formation with a resistivity range between 2 and 25 Ωm, a depth of 0-8 m, and is interpreted as a saturated marl-clay overlaying. The second, a hard and compact formation with a resistivity range between 50 and 200 Ωm and a depth range of 8 to 40 m, was interpreted as a substrate of tellian marls. The presence of boulders of Numidian sandstone within the two formations is materialized by a very high resistivity value ranging from 500 to 1000 Ωm. The slip surface was located on the layer with low resistivity (2-25 Ωm). The precise determination of the depth of the shear zone is of vital use in implementing mitigation measures and carrying out the stabilization work of this unstable zone. Through this work, we will highlight the advantage of the combination of available results of the geological, geotechnical investigations and electrical resistivity tomography (ERT) carried out in the study area.

Petrogenesis of the early Permian Hongliujing granite complex in the Chinese Eastern Tianshan orogen: Evidence for crustal growth in the Central Tianshan microcontinent

The generation and modification of silicic magma systems are essential processes in resolving the differentiation of continental crust. This understanding motivated the geochronological and geochemical study of the early Permian Hongliujing granite complex, consisting of quartz monzonite, granite, and leucogranite in the Central Tianshan microcontinent of the southern Central Asian Orogenic Belt. Laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) zircon U-Pb dating of the Hongliujing complex rock units revealed almost identical ages (279 ± 2 Ma to 270 ± 2 Ma). The high-silica leucogranite and granite are characterized by positive Rb and negative Eu anomalies and Ba, Sr, P, and Ti depletions. The zircon trace elements are characterized by relatively low Ti and Th/U and high Yb/Gd. In contrast, the quartz monzonite and its mafic microgranular enclaves display minor negative Ba, Sr, P, Ti, and Eu anomalies, while the zircon trace elements are characterized by relatively high Ti and Th/U and low Yb/Gd. The complex has similar zircon Hf and whole-rock Nd isotopic compositions, with Hf and Nd model ages younger than 1.4 Ga, suggesting that their magmas were derived from an isotopically depleted mantle, with some contributions from crustal melts. The leucogranites further showed relatively large variations of εHf(t) and lower εNd(t) values, implying that their magma was affected by higher amounts of crustal contamination. We suggest that crystal-melt segregation was the major mechanism responsible for the evolution of the magmatic system, and that the early Permian magmatism represents a crust-forming episode triggered by slab rollback of the subducting South Tianshan oceanic plate beneath the eastern Central Tianshan microcontinent. Thus, our study reveals that microcontinents with Precambrian crustal basement were major sites of juvenile continental growth during the accretionary evolution of the Central Asian Orogenic Belt.

Engineering geological characterization and assessment of complex rock slope failures in Mudurnu, Turkey

Engineering geological characterization and assessment of complex rock slope failures in Mudurnu, Turkey

Model based impact assessment on groundwater vulnerability during aggregate quarry operation

A general methodological approach is proposed for the preliminary assessment of the potential impact on groundwater during the operation of quarries for aggregates. The practical application and effectiveness of this approach are by using a numerical model to predict groundwater and soil contamination during the implementation of a project in the region of Breznik, Western Bulgaria. The spread of highly mobile pollutants in both the unsaturated and saturated zones of the rock complex is simulated after emergency spills and prolonged discharges of contaminated water in the quarry area. The forecast is made for a period of 100 years. The numerical model was compiled using the VS2DI program.

Fabric controls on fracture surface roughness of an architected rock material

Fluid flow through fractures is intimately linked to the fracture surfaces that define the void geometry through which fluids flow. Thus, an understanding of what controls fracture surface roughness is essential to the development of models for predicting fluid transport through fractured rock. The difficulty in predicting surface roughness arises from the complexity of rock which is inherently heterogeneous and nonuniform in composition, fabric, and structural components, even when samples are acquired from the same rock mass. Here, a benchmarked-simulation approach motivated from geo-architected 3D printed synthetic gypsum rocks is used to provide insight into the competing contributions from fabric and layering on fracture roughness formation. Simulation results from a discrete element model (Particle Flow Code, Itasca Consulting Group, Inc.) clearly indicate that the relative orientation between mineral layers and in-layer mineral fabric, and the variability in mineral bonding strengths determine whether anisotropic corrugated surfaces or isotropic surfaces are formed. Weak mineral layers oriented perpendicular to the applied load resulted in strong roughness anisotropy. Peak failure loads were found to vary up to 30% depending on the strength of the mineral fabric at the location of fracture initiation, which provides insight into the observed high variability in strength values of natural rock. The uniqueness of induced fracture roughness and peak failure load is intimately linked to layering, mineral fabric, and their distribution in the rock. These findings have important implications for any architected material fabricated through serial printing of layers with local compositional heterogeneity.

Reference seismic crustal model of the Dinarides

Abstract. Continental collision zones are structurally one of the most heterogeneous areas intermixing various different units within a relatively small space. A good example of this is the Dinarides, a mountain chain situated in the central Mediterranean, where thick carbonates cover older crystalline basement units and remnants of subducted oceanic crust. This is further complicated by the highly variable crustal thickness ranging from 20 to almost 50 km. In terms of spatial extension, this area is relatively small but covers tectonically differentiated domains making, any seismic or geological analysis complex, with significant challenges in areas that lack seismic information on crustal structure. Presently there is no comprehensive 3D crustal model of the Dinarides (and surrounding areas). Using the compilations of previous studies and employing kriging interpolation, we created a vertically and laterally varying crustal model defined on a regular grid for the wider area of the Dinarides, also covering parts of Adriatic Sea and the SW part of the Pannonian Basin. The model is divided by three interfaces, Neogene deposit bottom, carbonate rock complex bottom and Moho discontinuity, with seismic velocities (P and S waves) and density defined at each grid point. To validate the newly derived model, we calculated travel times for an earthquake recorded on several seismic stations in the Dinarides area. The calculated travel times show significant improvement when compared to the simple 1D model used for routine earthquake location in Croatia. The model derived in this work represents the first step towards improving our knowledge of the crustal structure in the complex area of the Dinarides. We hope that the newly assembled model will be useful for all forthcoming studies (e.g., as a starting model for seismic tomography, as a model for earthquake simulations) which require knowledge of the crustal structure.

A New Multi-Scale Method to Evaluate the Porosity and MICP Curve for Digital Rock of Complex Reservoir

The evaluation of rock porosity and the mercury injection capillary pressure (MICP) curve is fundamental for oil and gas exploration and production. Digital rock (DR) technology, incorporating 3D micro-CT imaging and numerical methods, has been widely employed to predict these properties. However, analyzing the pore structure of heterogeneous rocks, such as fractured rocks or glutenite, solely through single-scale DR analysis poses challenges. Existing upscaling methods have limitations in fully representing the complete range of pore structures at different scales, with limited comparison to experimental data. To address this, we propose a novel method that upscales porosity and simulates the MICP curve from nano-scale to core scale by merging results from micro-CT (at resolutions of 35 μm and 2 μm) and SEM (at resolutions of 6.5 nm and 65 nm). We validate the developed DR model by applying it to sandstones, glutenite, and igneous rocks, and achieve excellent agreement between the experimental data and the multi-scale DR model across 67 samples. The results demonstrate that the multi-scale model effectively captures the porosity and pore structures across the entire range. In contrast, the single digital rock (DR) model underestimates the porosity measurements for both homogeneous sandstones and heterogeneous cores. While the MICP model based on a single DR proves suitable for homogeneous rock samples, it introduces noticeable discrepancies when applied to heterogeneous rock samples. The developed multi-scale method significantly enhances the confidence in using DR to assess the pore structure of complex rocks.

SELECTION OF DRILLING MUD TO PENETRATE COMPLICATED HORIZON S2V WATER INJECTION WELL AT NODA PRODUCTION SITE

Drilling wells under conditions of production from the S2V reservoir in the territory is a difficult task, which is associated with various technical and geological difficulties. These complications include increased well construction time and the potential for wellbore loss. The drilling process can disrupt the equilibrium of the rocks forming the walls of the well, especially in the case of complex clay formations. For successful drilling and risk minimization, special attention must be paid to the choice of drilling fluid and mud formulations. Various types of drilling fluids have been considered, including High Inhibition Systems (HPWBM) and Triple Inhibition Flushing Fluids, which contribute to improving drilling conditions in difficult geological conditions. Particular attention is paid to the drilling interval from 1650 to 2220 meters, which is represented by complex rocks, including limestones, mudstones and dolomitic areas with a porous structure. Potential problems such as caving, collapses, loss of drilling fluid, and differential sticking have been considered and mud formulations have been proposed to effectively combat these problems. To assess the impact of the solutions on the rocks, a study of the change in permeability of core samples was carried out using the permeability recovery factor. The results of the primary studies make it possible to make a preliminary conclusion on the compliance of the solution of smalllinous lime-inhibited with the necessary characteristics. Overall, this study highlights the importance of selecting the right mud formulations to ensure safe and efficient drilling of wells in challenging geological conditions.

Effects of pre-test heating temperature on microstructure, chemical and mineralogy of lateritic soil

Pre-test drying methods are known to have a significant impact on the properties of lateritic soils. Nevertheless, there has not been sufficient investigation into the impact of pre-test drying temperature on the mineralogical and microstructural characteristics of lateritic soils, which are particularly sensitive to moisture variation. This work aims to investigate the impact of the temperature used for pre-test drying on the microstructure and mineralogy properties of three lateritic soils from Ado-Ekiti, Southwest Nigeria, which developed over different Precambrian basement complex rocks. Samples of disturbed lateritic soils were collected and tested at their natural moisture content (NMC) as well as at three other states obtained through air-drying and oven-drying at 60 °C and 110 °C. X-ray diffraction and scanning electron microscope (SEM) analyses were performed to explore the mineralogy and microstructural properties of the soils. Results show that the lateritic soils at their NMC consist mainly of kaolinite, quartz, and k-feldspar, while minerals like clinopyroxene, mica, and plagioclase feldspar, hematite are present in minor quantity. The increase in the pre-test drying temperature had no significant impact on the mineralogy or elemental composition of the lateritic soil, possibly due to the fact that the temperature was not sufficiently high to trigger mineral transformation. As the pre-test drying temperature rose, SEM micrographs indicated that the structure of the air-dried and oven-dried soil samples became increasingly aggregated and clumped, particularly when the temperature reached 110 °C. This suggests that the oven-drying process caused particle aggregation, which altered the structure of the lateritic soils and, in turn, affected properties such as plasticity and particle size distribution.

Veined Rock Performance under Uniaxial and Triaxial Compression Using Calibrated Finite Element Numerical Models

Geotechnical rockmass characterization is a key task for design of underground and open pit excavations. Hydrothermal veins influence excavation performance by contributing to stress-driven rockmass failure. This study investigates the effects of vein orientation and thickness on stiffness and peak strength of laboratory scale specimens under uniaxial and triaxial compression using finite element numerical experiments of sulfide veined mafic igneous complex (CMET) rocks from El Teniente mine, Chile. The initial numerical models are calibrated to and validated against physical laboratory test data using a multi-step calibration procedure, first of the unveined Lac du Bonnet granite to define the model configuration, and second of unveined and veined CMET. Once calibrated, the numerical experiment involves varying the vein geometry in the veined CMET models by orientation (5 to 85°) and thickness (1, 4, 8 mm). This approach enables systematic investigation of any vein geometry without limitations of physical specimen availability or complexity of physical materials. This methodology greatly improves the value of physical laboratory test data with a limited scope of vein characteristics by using calibrated numerical models to investigate the effects of any other vein geometry. In this study, vein orientation and thickness were both found to have a significant impact on the specimen stiffness and peak strength.

Provenance of far-traveled nappes in the eastern Mediterranean (Uppermost Unit, Crete): constraints from U–Pb zircon ages of detrital and igneous zircons

New U–Pb ages of detrital and igneous zircons of the Uppermost Unit of Crete shed light on its provenance and on Eohellenic to Eoalpine imprints in the eastern Mediterranean. The detrital zircons of all nappes show Variscan ages and are characterized by a Minoan-type age spectrum, which is typical for the NE margin of Gondwana. Parts of the metasedimentary rocks are unexpectedly young. Their detrital zircon ages continue via the Permian until the Late Triassic, Middle Jurassic and Early Cretaceous. The high-grade metamorphic rocks of the Asterousia crystalline complex are likely equivalents of the low-grade metamorphic trench and fore-arc deposits of the Vatos nappe pointing to Late Cretaceous slab roll back. The presence of both late Permian detrital zircons and Late Cretaceous arc-type granitoids suggest that the Uppermost Unit of Crete is derived from the late Permian/Late Cretaceous magmatic belt situated north of the Sava–Vardar–Izmir–Ankara Suture in the Strandja–Rhodope area. To achieve their recent position on Crete, the nappes had to travel more than 500 km. The traveling path is well tracked by rocks of the Upper Cycladic Unit, which are similar to those of the Uppermost Unit of Crete. The large displacement of the Cretan nappes was controlled not only by nappe transport, but probably also by dextral strike–slip along the North Anatolian Fault Zone and related counterclockwise rotation of the Anatolian block since the Eocene.Graphical abstract

Hornblende in ultramafic-mafic rocks of the Khudolaz Complex of the Southern Urals: Crystallization conditions and petrological implications

Subject research. Morphology and chemical composition of amphiboles from ultramafic-mafic rocks of the Khudolaz complex. Methods. Morphological studies were carried out using optical (Carl Zeiss Axioskop 40A) and electron (Tescan Vega Compact) microscopes. The chemical composition of minerals was determined using CAMECA SX 100 and JEOL JXA-8230 electron probe microanalyzers. Results. The rocks under study are dominated by xenomorphic brown titanium hornblende crystals, formed mainly due to the reaction of clinopyroxene with a residual water-saturated melt at 920–1040°C. Euhedral brown hornblende, which crystallized directly from the residual water-saturated melt in the same temperature range, was found in small amounts. Green hornblende originated along the edges and cracks in brown hornblende crystals during the late magmatic stage and early hydrothermal stage (670–830°C) at the subsolidus transformation. At the hydrothermal stage (620–650°C and below), brown and green hornblende were partially replaced by actinolite and cummingtonite. Conclusions. The nature of changes in the composition of brown hornblende indicates similar petrogenesis conditions at the late magmatic stage in all intrusions of the Khudolaz complex. The process of transition from brown hornblende to green hornblende occurred with a gradual increase in oxygen fugacity (ΔNNO from –0.2…+0.4 to +0.9…+2.5), and was accompanied by decrease of Ti, Fe2+, Na and the increase of Si, AlVI, Mg, and K in the mineral structure. The low concentrations of F and Cl in hornblende crystals indicate their formation after migration of halogens from the melt.

THE FIRST FIND OF CAMBRIAN VOLCANITES AND PLAGIOGRANITES IN TEKTURMAS OPHIOLITE ZONE (CENTRAL KAZAKHSTAN): AGE AND COMPOSITION

The complex of felsic rocks, intruded by plagiogranitic bodies are first revealed in the west of the Tekturmas ophiolite zone of Central Kazakhstan. The U–Pb (SIMS) geochronological study of one of the plagiogranitic bodies was carried out and the Early Cambrian age (537 ± 5 Ma) was first obtained. The peculiarities of effusives and plagiogranites composition indicate their formation in the supra-subduction setting within primitive volcanic island arc. Formation of this arc was not related to the evolution of the oceanic structures, which complexes participate in the structure of the Tekturmas zone.

Evaluation of Groundwater Potentiality and Subsurface Structural Setting by Using Geophysical Data in Wadi Hubuna, Southwest Najran, Saudi Arabia

A geophysical study was conducted to explore the shallow groundwater aquifer and to identify the subsurface structure on the basis of resistivity and geomagnetic surveys. The study area is situated in the southwestern portion of Saudi Arabia, southwest of the Najran region. The total intensity magnetic map is reduced to the northern magnetic pole. The estimated mean depths of the regional and residual magnetic sources are 3 km and 1.4 km respectively. Eighty vertical electrical soundings were measured using the Schlumberger configuration with AB/2 spacing of up to 700 m. Four geoelectrical layers were identified, and could be described from ground surface to deeper layers as the following: The first layer encompasses wadi deposits with true resistivity values ranging from 452 Ω.m to 1353 Ω.m and thicknesses of 2-4 m. The second layer is comprised of dry fine to medium grain-sized deposits with true resistivity values ranging from 104 Ω.m to 451 Ω.m, and thickness varying between 2 and 16 m. The third layer consists of water-bearing friable deposits beside the topmost part of the underlying weathered (fractured) basement. The true resistivity of this layer ranges from 22 Ω.m to 188 Ω.m, whereas the thickness of this layer is highly variable and ranges from 5 to 35 m. Generally, the resistivity values and the thickness of these three layers exhibit an increasing trend toward the main wadi stream. A fourth layer was also detected and is represented by a thin clay layer directly overlying the hard rocks of the basement complex. The dominant tectonic trends controlling the shallower parts are N-S and NNW-SSE. Meanwhile, the structural trend controlling the deeper parts is NE-SW, E-W, and. NNE-SSW. The ideal areas for drilling wells, according to the interpreted cross-sections, are along the main stream of Wadi hubuna and other small wadis, as well as the lower portions of the wadi in the extreme east direction.

Subduction initiation recorded in the Dadeville Complex of Alabama and Georgia, southeastern United States

Abstract The Dadeville Complex of Alabama and Georgia (southeastern United States) represents the largest suite of exposed mafic-ultramafic rocks in the southern Appalachians. Due to poor preservation, chemical alteration, and tectonic reworking, a specific tectonic origin for the Dadeville Complex has been difficult to deduce. We obtained new whole-rock and mineral geochemistry coupled with zircon U-Pb geochronology to investigate the magmatic and metamorphic processes recorded by the Dadeville Complex, as well as the timing of these processes. Our data reveal an up-stratigraphic evolution in the geochemistry of the volcanic rocks, from forearc basalts to boninites. Our new U-Pb zircon crystallization data—obtained from three amphibolite samples—place the timing of forearc/protoarc volcanism no later than ca. 467 Ma. New thermobarometry suggests that the Dadeville Complex rocks subsequently experienced deep, high-grade metamorphism, at pressure-temperature conditions of >7 kbar and >760 °C. The data presented here support a model for formation of the Dadeville Complex in the forearc region of a subduction zone during subduction initiation and protoarc development, followed by deep burial/underthrusting of the complex during orogenesis.

Geology, Petrology, and Mineralogy of Hornfels-like Rocks (Beerbachite) in the Early Paleozoic Olkhon Collisional Orogen (West Baikal Area, Russia)

Geological, mineralogical, and petrological observations are reported for hornfels-like fine-grained granular mafic rocks in the Early Paleozoic Olkhon collisional orogen (West Baikal area, Russia). The rocks are composed of orthopyroxene, clinopyroxene, amphibole, plagioclase, and ilmenite; some samples also contain olivine, phlogopite, spinel, and titanomagnetite (Opx+Cpx+Amp+Pl+Ilm±Ol±Bt±Spl±Ti-Mag). There are three occurrences of these rocks in the area: a 500 m × 1000 m field in the Shirokaya Valley, another occurrence within the Tazheran Massif (a complex of igneous and metamorphic rocks), and dismembered dikes on the southern margin of the Birkhin gabbro intrusion. The Shirokaya field is located between two 500 Ma intrusions of the Birkhin gabbro; the Tazheran occurrence coexists with syenite, including nepheline syenite, subalkaline gabbro, and marble protrusions; and the dismembered dikes coexist with carbonates and display progressive alteration of dolerite through typical granular varieties. The dikes associated with granite and marble veins mark a part of a large arc-shaped shear zone that traverses the whole intrusive body produced by rotation of a rigid gabbro block during the peak of tectonic deformation at 470–460 Ma. All three occurrences of the hornfels-like rocks lack any evident source of heat that would be responsible for the thermal alteration of the igneous protolith. We hypothesize that the precursor, subvolcanic dolerite, may have undergone autometamorphism maintained by self-generated heat. Mafic magma intruded during high-rate strike–slip faulting, which caused rapid recrystallization of magmatic minerals and produced the observed metamorphic structures. Proceeding from the controversy in the formation mechanisms, with a heat source required for hornfels but lacking from the sampled occurrences of hornfels-like rocks, we suggest identifying the latter as beerbachite, though the term has mostly fallen into disuse. The reason is that the Olkhon rocks we study have a mineralogy, structure, and texture that are perfectly identical to those of beerbachites described in publications from the first half of the 20th century.

Field and petrographic studies of Basement Complex rocks in Saigbe and Environs, North-Central, Nigeria

Geological mapping and petrographic studies of rocks provide useful information on texture and mineralogical composition of rocks which can be used in the exploration and exploitation of any associated mineralization. However, few regional studies have been conducted in Minna and environs. Here, preliminary field mapping and petrography of out crops in Saigbe environ were conducted to determine their identification, structural and mineralogical composition. Twenty-one rock samples were collected, eight of which were used for thin section analysis. Joint directions were measured and plotted on rose diagram. Results show that Saigbe is underlain by schist, amphibolite and granite with minor pegmatite intrusions. Joints, faults, fold and foliations constitute main structures. Joints in the schists trend NE-SW, while those in the granites trend NW-SE, suggesting different episodes of emplacement for both rocks. Petrography revealed that the schists comprised quartz, biotite, muscovite, plagioclase and opaque mineral, while the amphibolites are composed largely of quartz, hornblende, plagioclase feldspar and opaque minerals. The granites are composed of quartz, microcline, plagioclase feldspar, muscovite and opaque minerals. The pegmatite dykes in the granites comprised quartz, plagioclase feldspar, orthoclase feldspar, muscovite and gemstones, hence interpreted as product of residual melt. The pegmatites make interesting target for mineral exploration.

TECTONIC STRESSES IN THE CHERSKY FAULT ZONE (BAIKAL RIFT SYSTEM

Based on the kinematic and structural-paragenetic approaches, there were performed the reconstructions of tectonic stresses in the Chersky fault zone. Rank analysis as applied to specialized mapping of fault zones was made for heterochronous rock complexes: Paleozoic, Upper Oligocene – Lower Pliocene and Upper Pliocene – Quaternary. There are distinguished three regional stress fields: Pre-Cenozoic compressive stress field with the NW-SE striking principal axis and two Cenozoic tensile stress fields with different axial orientations. The Cenozoic tensile stress field with a sub-meridionally striking minimum compression axis may be an earlier occurrence because it was found to exist in the Paleozoic and Oligocene – Early Pliocene rocks, and the tensile stress field, with the NW-SE axial orientation, may be later occurrence as reconstructed for all rock complexes including Quaternary pebbles. No evidence was found of tectonic shear stresses within the studied segment of the Chersky fault zone. Consideration is being given to probable reasons for the absence of residual shear deformations in the region and to the problems in the study of hierarchy of the upper crustal tectonic stresses.

THE GENESIS OF GARNET-PYROXENE SYENITES (SVIATONOSSITES) OF THE MALOBYSTRINSKY MASSIF (SLYUDYANKA COMPLEX, SOUTH BAIKAL REGION): RESULTS OF GEOCHEMICAL AND ISOTOPIC STUDIES

This paper deals with the study of syenites and sviatonossites (andradite-bearing syenites) of the Malobystrinsky massif of the Slyudyanka complex (South Baikal region, Siberia), and a large monzonite dike similar in age and composition to the rocks of the massif considered. The studied rocks belong to a series of highly ferriferous and metaluminous A-type granitoids (ASI index <1). They are characterized by SiO2 45–65 wt. %, K2O+Na2O up to 12 wt. %, MgO <4 wt. %, TiO2 up to 2.5 wt. %, and Al2O3 up to 17 wt. %. CaO varies in a wide range, from 2.2 to 14.7 wt. %. The rocks are similar to each other in trace element composition and show patterns with troughs for Th-U, Nb-Ta and Ti. Low-amplitude negative Eu anomaly is observed in the distribution spectra of rare earth elements for the entire rock complex. The obtained Sm-Nd age of sviatonossites in the Malobystrinsky massif is 487.1±6.1 Ma (MSWD=0.99). Our results indicate that syenites and monzonites have εNd(t) –1.9…–2.8, at εSr(t) 21–30, and sviatonossites have εNd(t) –3.8…–4.1 at εSr(t) – 26. Model ages TNd(DM) for all rock types are Mesoproterozoic (1.3–1.4 Ga). Based on the chemical and Sr-Nd isotopic composition of the magmatic rocks studied, it can be assumed that they have been generated by partial melting of lower crustal rocks (amphibolites). Crystallization of andradite garnet in syenite magma can occur due to melt contamination with metamorphic host rocks of the Slyudyanka complex.

Dynamic physical-geological model of complex folding according to paleomagnetic data

The purpose of the study is to evaluate the possibility of using the mathematical apparatus of spatial rotations to solve the determination issues of the nature and age of natural remanent magnetization vectors under complex tectonic dislocations of rocks manifested in the areas of modern folded structures of platform framing. Dynamic physical-geological models are shown to be useful when forming complex tectonic-magmatic systems. Mathematical (computer) modeling in comparison with other methods of studying geological processes features higher accuracy, cost-effectiveness and unambiguity of data interpretation in achieving the set goal. On the basis of dynamic physical-geological model of complex folding, an algorithm is developed and the results of mathematical modeling of natural remanent magnetization vectors are given for solving direct and inverse problems on correct application of the fold test under complex rock deformations. The dynamic physical-geological model of complex folded structure formation shows that the characteristic natural remanent magnetization vectors identified in laboratory experiments on demagnetization can be used to determine their age relative to the folding stages, and, depending on this, fully or partially restore the number, sequence and direction of tectonic dislocations. This will enable us to solve the mineralogenic and geodynamic problems of folded region development more effectively on the basis of paleomagnetic data.