Geodynamic Data Research Articles

Mesozoic clastic provenance during post-rift evolution of the Essaouira Agadir Basin, Northern Morocco

This study combines several provenance tools, analysis of published structural and geodynamic data, integrated with Low-Temperature Thermochronology (LTT) and time-Temperature Modelling (tTM) to reconstruct the evolution of source-to-sink systems feeding the Essaouira-Agadir Basin (EAB) during the Jurassic (Toarcian, Bathonian, and Kimmeridgian) and Lower Cretaceous (Hauterivian and Barremian).LTT and tTM define timing and rate of subsidence and exhumation of the hinterland and allows modelling of the predicted age and lithology of eroding rock units from the most-likely source locations through time. Extrapolation of predicted surface geology allows recognition of the lithology of sedimentary overburden in the hinterland, much of which has been subsequently eroded and is not preserved in the modern surfical geological record.Heavy mineral, petrography and detrital zircon data analysis was carried out on fluvial and shallow marine sandstones sampled from Jurassic and Cretaceous sections across in the EAB. The results document changing sediment source terrains through time. In the Early and Middle Jurassic, the heavy mineral and detrital zircon signature correlates with a Palaeozoic source, suggesting provenance was dominantly from erosion of Cambrian and Ordovician sandstone in the Central and Western Anti-Atlas. From the Late Jurassic to Early Cretaceous, the heavy mineral and zircon signatures have a strong affinity with Triassic sediments. This indicates a provenance switch to the exhuming West Moroccan Arch (MAM and Western Meseta), interpreted to have been largely covered by Triassic continental red beds at the time.The results help in predicting sediment delivery offshore, into the deep-water basin, where sandstones are a target for hydrocarbon exploration. Defining timing of input, location and composition helps to de-risk exploration. All the intervals examined contained discrete fluvial systems entering in the EAB, suggesting multiple periods of clastic delivery. Results suggest the Middle Jurassic and Hauterivian and Barremian intervals offer the optimum time for delivery of coarse clastics to the shelf margin, and potentially into the deep basin. The source to sink maps developed in this study further characterize these systems, their provenance and timing.

Geological-genetic structure of Irpin city, the role of lithological factors during engineering-geological zoning and construction assessment

The scheme of engineering-construction assessment created based on engineering-geological zoning of the city’s territory is desirable among additional graphic materials in the design of master plans projects as determined by building regulations. Engineering-geological zoning provides for different ranks’ selection of engineering-geological units (EG units), which have a particular range of common engineering-geological conditions that ultimately determine the construction sites’ affiliation to a specific suitability category. Geological-genetic structure of Irpin city of Kyiv region (Ukraine) is explored in this article. A variant of the creation of a large-scale engineering-geological map and corresponding geological-lithological sections by supporting boreholes in the borders of the city based on the engineering-geological survey conducted is presented. The obtained result allowed the selection of engineering geological zoning units – engineering geological districts by general conditions of geological development and subdistricts by engineering-geological complexes of Quaternary rocks’ thickness. The analysis of soils’ geomechanical properties (engineering-geological elements) lays the foundations for the selection of engineering-geological sites based on the comparison of this information with geomorphological, hydrogeological and geodynamic data. Accounting of geological-lithological factors in the preparation of the construction assessment scheme in the project of Irpin city’s master plan has become the ultimate result.

Fluid evolution and genesis of the Sankuanggou Fe[sbnd]Cu skarn deposit, Duobaoshan ore field, Northeast China: Evidence from fluid inclusions and H-O-S-Pb isotopes

The Sankuanggou FeCu skarn deposit is located in the Duobaoshan ore field in the northern Great Xing'an Range, Notheast China. The ore bodies occurred in the skarn of the contact zone between the Yanshanian granodiorite and the middle Ordovician Duobaoshan Formation marble. According to the field investigations and mineral crosscutting relationships, five paragenetic stages were identified: the anhydrous skarn (Stage I); hydrous skarn (Stage II); chalcopyrite-pyrite-quartz-molybdenite (Stage III); sphalerite-quartz stage (Stage IV) and quartz-calcite (Stage V). In the Stage I and II, the assemblage of fluid inclusions (FIs) in quartz is characterized by the development of daughter mineral-bearing three-phase FIs (S-type), vapor-rich two-phase aqueous FIs (LV-type) and liquid-rich two-phase aqueous FIs (VL-type). VL- and LV-type FIs were found in the Stage III quartz, whereas only VL-type FIs were present in the Stage IV quartz and Stage V calcite. The homogeneous temperatures of the FIs in Stages I to V were 364–495, 295–405, 243–360 and 135–207 °C, respectively, with salinities of 4.16–58.42, 4.17–47.99, 3.37–14.2, 1.03–11.11 and 3.53–8.4 wt% NaCl eqv., respectively. In general, the ore-forming fluids changed from high-temperature NaCl-H2O system fluids, that contained negligible amounts of CO2 and CH4 and exhibited obvious boiling, to a medium- to low-temperature and low-salinity NaCl–H2O system with fluid mixing. According to the HO isotopic analysis of Stages I and II (δ18OH2O = 0.3–6.3 ‰, δ18D = −112.6 to −79.9 ‰), the ore-forming fluid was identified as magmatic fluid. In contrast, the δ18OH2O and δ18D values in Stages III and IV gradually decreased (δ18OH2O = −9.6 to −2.3 ‰, δ18D = −133.1 to −118.9 ‰), implying a gradual meteoric water input into the fluid. The S isotopic analysis (δ34S range from −4 to −0.8 ‰) revealed that S mainly originates from the magma during the mineralization process. Further, the Pb isotopic (208Pb/204Pb = 37.64–38.725, 207Pb/204Pb = 15.45–15.606 and 206Pb/204Pb = 18.115 to 19.786) investigations indicated that the ore-forming materials of this deposit are derived from the crust-mantle mixing. Based on the previously reported geochronologic and geodynamic data, we can conclude that the Sankuanggou deposit is a typical FeCu skarn deposit and formed during the Early Jurassic Paleo-Pacific Plate subduction.

A Technology for Seismogenic Process Monitoring and Systematic Earthquake Forecasting

Earthquakes are a severe natural phenomenon that require continuous monitoring, analysis, and forecasting to mitigate their risks. Seismological data have long been used for this purpose, but geodynamic data from remote sensing of surface displacements have become available in recent decades. In this paper, we present a novel information technology for monitoring, analyzing seismogenic fields, and predicting earthquakes using Earth remote sensing data presented as a time series of surface displacement points for systematic regional earthquake prediction. We demonstrate, for the first time, the successful application of this technology and discuss the method of the minimum area of alarm, which was developed for machine learning and systematic earthquake prediction, as well as the architecture and tools of the GIS platform. Our technology is implemented as a network platform consisting of two GISs. The first GIS automatically loads earthquake catalog data and GPS time series, calculates spatiotemporal fields, performs systematic earthquake prediction in multiple seismically active regions, and provides intuitive mapping tools to analyze seismic processes. The second GIS is designed for scientific research of spatiotemporal processes, including those related to earthquake forecasting. We demonstrate the effectiveness of platform analysis tools that are intuitive and accessible to a wide range of users in solving problems of systematic earthquake prediction. Additionally, we provide examples of scientific research on earthquake prediction using the second GIS, including the effectiveness of using GPS data for forecasting earthquakes in California, estimating the density fields of earthquake epicenters using the adaptive weighted smoothing (AWS) method for predicting earthquakes in Kamchatka, and studying earthquake forecasts in the island part of the territory of Japan using the earthquake catalog and GPS. Our examples demonstrate that the method of the minimum area of alarm used for machine learning is effective for forecasting both catalog and remote sensing data.

Hydrogeological conditions of Irpin and their influence on the city’s engineering protection and construction assessment

The scheme of engineering-construction assessment, which is created based on engineering geological zoning of the city’s territory is desirable among additional graphic materials in the design of master plans projects as determined by state building norms [State…, 2012]. Engineering geological zoning provides for different ranks’ selection of taxonomic engineering-geological (EG) units, which have a particular range of common engineering geological conditions that ultimately determine the construction sites’ affiliation to a specific suitability category. Geological-lithological structure and hydrogeological conditions of the Irpin city, Kyiv region are investigated, and the types and degrees ofgroundwater aggressiveness, chemical composition, and mineralization of groundwater, the depths of the first aquifers from the day surface are highlighted in this article. A variant of the creation of large-scale maps of groundwater depth and chemistry based on a hydrogeological survey conducting is presented. The analysis of hydrogeological circumstances of the city’s territory lays the foundations for the selection of engineering-geological sites based on the comparison of this information with geomorphological, engineering-geological and geodynamic data. Complexity assessment of hydrogeological conditions and accounting of hydrogeological factors for the construction assessment scheme and selection of corresponding measures of engineering training and protection of the problem construction sites has become an ultimate result.

Anatolian plate active faults character using potential fields data

The paper investigates the features of the manifestation in potential fields methods (gravity and magnetic exploration) of faults in the territory of modern Turkey and their relationship with earthquakes. The relevance of the work is determined by the significance of studying active faults as seismogenerating structures that directly affect the degree of seismic hazard of the territory of Turkey. The purpose of the work: based on geophysical and geodynamic data, to study the active faults of modern Turkey and adjacent territories, trace them to a depth and compare them with the foci of earthquakes that occurred in Turkey, including in February 2023. The study used original methods of data interpretation potential fields methods: complex analysis of maps of gravimetric and magnetic fields, tracing of lineaments, construction of transformation maps, solving the inverse problem using “tomography of potential fields” technology. For the entire selected territory, the inverse problem was solved for gravity and magnetic exploration data using the “tomography of potential fields” technique. A great potential has been identified in the data of gravity and magnetic exploration for the assessment of inhomogeneities in the structure of the Earth’s crust.

Structural and geodynamic control of abnormal thermobaric conditions and physical properties of oil reservoirs in the Chezhen sag of the Jiyang depression, East China

Geologically, the rift system of East China has a complex block structure influenced by large-scale and differently directed tectonic movements which took place in the Earth’s crust many times in the geological history of East China. The neotectonic movements greatly complicated the geological structure and, naturally influenced formation of the modern fluid dynamical system. Exploration for oil within the Chezhen block of the Shengli field involves certain difficulties associated with the complex block geological structure, small size of most oil pools and varying thermobaric conditions within a pool (even in the range of two neighbor wells). This article describes the studies aimed at enhanced efficiency of exploration for oil, including shale oil which is a new petroleum source in East China. The physical properties of oil and the thermobaric conditions of oil occurrence in the Paleozoic and Paleogene deposits in the Chezhen sag are described. Well information is analyzed in package with geological and geodynamic data. It is for the first time found that in the Chezhen sag: the local areas of increased thermobaric conditions in the oil pools and the better quality oil (lower density and viscosity) occur at the faults of the younger age; the actual deviations from the classical geological and physical correlations (direct reservoir pressure–temperature–depth dependence, direct oil viscosity–temperature/depth dependence) are governed by the migrational geodynamics; the borderline between the notions of a reservoir and a non-reservoir (cap) is quite tentative. The authors propose two mechanisms of origination of the abnormally high reservoir-pressure zones in pools of oil, including shale oil, associated with the migrational geodynamics and with the formation and accumulation of hydrocarbons.

Extensive and ancient feldspathic crust detected across north Hellas rim, Mars: Possible implications for primary crust formation

Abstract Due to its size and observable record of ancient rock, Mars is key to understanding crustal formation on planetary bodies, including Venus and Earth, which may have derived their first stable crust from mantle-overturn melting. Recent evidence that ancient martian crust contains an evolved component supports inferences of a pervasive, buried feldspathic component to the crust. With data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), we searched for feldspathic lithologies in pre-Noachian (older than ca. 4.1 Ga) crustal blocks uplifted by the Hellas basin-forming impact. We present evidence for ancient feldspathic rocks exposed across an ~2200 × 600 km area north of Hellas. Given their pre-Noachian age and stratigraphic position directly above putative mantle material, it is possible that these outcrops represent martian primary crust. Our discovery supports the hypothesis that there exists a pervasive, subsurface feldspathic component to the martian crust—a hypothesis that has, until now, been supported only by inferences from geodynamic data and small-scale observations.

The effects of discontinuity topography in the mantle transition zone on global geodynamic observables and mantle heterogeneity

SUMMARYDespite progress in tomographic imaging of Earth's interior, a number of critical questions regarding the large-scale structure and dynamics of the mantle remain outstanding. One of those questions is the impact of phase-boundary undulations on global imaging of mantle heterogeneity and on geodynamic (i.e. convection-related) observables. To address this issue, we developed a joint seismic-geodynamic-mineral physical tomographic inversion procedure that incorporates lateral variations in the depths of the 410- and 660-km discontinuities. This inversion includes S-wave traveltimes, SS precursors that are sensitive to transition-zone topography, geodynamic observables/data (free-air gravity, dynamic surface topography, horizontal divergence of tectonic plates and excess core-mantle boundary ellipticity) and mineral physical constraints on thermal heterogeneity. Compared to joint tomography models that do not include data sensitivity to phase-boundary undulations in the transition zone, the inclusion of 410- and 660-km topography strongly influences the inference of volumetric anomalies in a depth interval that encompasses the transition zone and mid-mantle. It is notable that joint tomography inversions, which include constraints on transition-zone discontinuity topography by seismic and geodynamic data, yield more pronounced density anomalies associated with subduction zones and hotspots. We also find that the inclusion of 410- and 660-km topography may improve the fit to the geodynamic observables, depending on the weights applied to seismic and geodynamic data in the inversions. As a consequence, we find that the amplitude of non-thermal density anomalies required to explain the geodynamic data decreases in most of the mantle. These findings underline the sensitivity of the joint inversions to the inclusion of transition-zone complexity (e.g. phase-boundary topography) and the implications for the inferred non-thermal density anomalies in these depth regions. Finally, we underline that our inferences of 410- and 660-km topography avoid a commonly employed approximation that represents the contribution of volumetric heterogeneity to SS-wave precursor data. Our results suggest that this previously employed correction, based on a priori estimates of upper-mantle heterogeneity, might be a significant source of error in estimating the 410- and 660-km topography.

Dynamic Activity Index for Feature Engineering of Geodynamic Data for Safe Underground Isolation of High-Level Radioactive Waste

In this study, we developed a new approach for feature engineering in geosciences. The main focus of this study was feature engineering based on the implementation of the dynamic activity index (MDAI) as a function of the anomaly of the spatial distribution of data, using systems and discrete mathematical analysis. The methodology for calculating MDAI by groups, geomorphological variability, the density of tectonic faults, stress-strain state, and magnetic field anomalies, is presented herein for a specific area. A detailed analysis of the correlation matrix of MDAI revealed weak correlations between the development features. This showed that the considered properties of the geological environment are independent sets and can be used in the analysis of its geodynamic stability. As a result, it was found that most of the territory where high-level radioactive waste (HLRW) disposal is currently planned is in a relatively stable zone.

Theoretical Framework for Determination of Linear Structures in Multidimensional Geodynamic Data Arrays

The article addresses the issue of clustering of multidimensional data arrays with a noise using the methods of discrete mathematical analysis (DMA clustering). The theory of DMA clustering through the logical densities calculus is detailed, and the new algorithm Linear Discrete Perfect Sets (LDPS) is described. The main objective of the LDPS algorithm is to identify linearly stretched anomalies in a multidimensional array of geo-spatial data (geophysical fields, geochemistry, satellite images, local topography, maps of recent crustal movements, seismic monitoring data, etc.). These types of anomalies are associated with tectonic structures in the upper part of the Earth’s crust and pose the biggest threat for integrity of the isolation properties of the geological environment, including in regions of high-level radioactive waste disposal. The main advantage of the LDPS algorithm as compared to other cluster analysis algorithms that may be used in arrays with a noise is that it is more focused on searching for clusters that are linear. The LDPS algorithm can apply not only in the analysis of spatial natural objects and fields but also to elongated lineament structures.

Повышение геодинамической безопасности разрабатываемых месторождений углеводородов нефтегазоносного бассейна

The predominant area of application of the developed methodology is the construction of the distribution of the geodynamic state of the developed hydrocarbon fields in oil and gas basin, and the identification of the corresponding distribution law. A number of the hydrocarbon deposits in terms of geological conditions of occurrence, structure and other parameters are geodynamically hazardous during their development. The Federal Law «On Subsurface Resources» (Article 24) requires conducting a complex of geological, surveying, and other observations sufficient for ensuring a normal technological cycle of work, and the prediction of hazardous situations. The developed methodology based on the construction of aggregated additive models for each reservoir and field is presented. It includes four sequential stages (24 operations): first — prepare geodynamic data; second — determine the geodynamic state of productive strata; third — find the geodynamic state of the developed deposits subsoil; fourth — build the distribution of the bowels geodynamic state of these fields for the entire oil and gas basin and identify the relevant distribution law. Oil and gas basin in the west of the Orenburg Region (Volga — Ural and Caspian oil and gas provinces) is considered as an example of implementation. Unique data of twenty geodynamic parameters of 320 productive strata (56 fields) were used. It is revealed that in accordance with the Pearson criterion, the theoretical data with a high confidence probability (95 %) correspond to the law of normal distribution. Developed methodology has significant technical and economic advantages, since it allows to identify the geodynamic state of productive strata and subsoil of the fields being developed, to identify hazardous geodynamic processes and to choose rational modes for the development of hydrocarbon deposits.

Recent GPS results on the geodynamics of the area around Sofia (Central-Western Bulgaria)

The paper outlines recent results from estimation of 23 years GPS measurements on the geodynamic network around Sofia. The obtained result, clearly provide new more accurate GPS geodynamic data on the considered area. All velocities clearly exceed 1.5–2 mm/y reaching up to 3–4 mm/y. As a general tendency the velocities tend to increase from North to South. According to the new results analysis of geological processes is given. The newly acquired velocities from three campaigns 1997, 2000 and 2020 years confirm that the general tendency of movement of the stations in the region of Central West Bulgaria is in the south direction with respect to stable Eurasia. The velocities tend to increase from north to south. This pattern is in agreement with the extensive movement of southern Bulgaria and northern Greece. The new results provide much better accuracy, reliability and local details.

Type of crossing of coal waste dumps by geodynamical dangerous zones

The paper develops the concept of the existence geodynamically dangerous zones in the earth’s crust. These zones affects to the safety of the state of engineering structures and mining operations. The concept of geodynamic zoning is used, according to which geodynamically dangerous zones occurs during the interaction of blocks of the earth’s crust of various hierarchical ranks. On the example of the East Donbass, the typification of the intersection of coal waste dumps with geodynamically dangerous zones is considered. The position of 34 burning and burnt out dumps located near the cities of Shakhty and Novoshakhtinsk, Rostov Region, their size R and the width of geodynamically dangerous zones r are taken in account. Based on the use of geodynamic zoning data, an analysis is made of the nature of the mutual arrangement of carbon rock dumps and the boundaries of blocks of the earth’s crust (geodynamically dangerous zones). It is found 4 types of intersection of the block boundaries and the body of the dumps. The intersection of the first type occurs when R> r and the location of the intersection site entirely under the dump. The intersection of the second type occurs when R <r and the location of the dump entirely in the geodynamically dangerous zone. The intersection of the third type occurs at any ratio of R and r, but the common area overlaps the geodynamically dangerous zone only partially (touch). In the fourth type of intersection, the set of common points R and r is empty (do not intersect). Typification can be used when choosing places for dumping and computer modeling of their thermal state.

The Sensitivity of Joint Inversions of Seismic and Geodynamic Data to Mantle Viscosity

AbstractSeismic tomography has revealed the existence of large‐scale velocity heterogeneities in the mantle. The interpretation of seismic velocity anomalies in terms of temperature and chemical composition is nonunique. We use geodynamic observations including gravity, plate motions, dynamic topography, and excess ellipticity of the core‐mantle boundary combined with seismic observations to investigate the thermo‐chemical structure of the mantle through joint inversions. An outstanding issue, however, is the physical connection between mantle density anomalies and the surface geodynamic observations, which requires knowledge of the mantle viscosity structure. Here we perform joint inversions assuming different viscosity profiles and examine the dependence of the results on the viscosity. We first assume that mantle heterogeneity is due to thermal variations, which places a constraint on the relation between seismic velocity and density, and we subsequently relax the constraint to allow for potential nonthermal effects. In all of our joint inversions, a nonthermal origin of density anomalies is required to explain the geodynamic data, though the amount varies with the assumed viscosity structure. A common observation is a high‐density chemical signal in the center of the large low‐shear‐velocity provinces at the base of the mantle resulting in a near neutral or slightly dense overall buoyancy there. Using the derived density models and their corresponding viscosity profiles, we also calculate instantaneous mantle flow fields. The predicted flow fields derived from joint inversions are generally similar but are quite different from flow fields using density models derived from a posteriori scaling of pure seismic tomography models.

Pliocene–Holocene Alkali-Basaltoid Volcanism of the Tsushima Basin of the Sea of Japan: New Geochemical and Geodynamic Data

Abstract—The paper contains original data on the rock-forming and rare element compositions in the Pliocene–Holocene alkaline basaltoids of the Tsushima Basin Sea of Japan, obtained by the “wet chemistry” method, atomic emission spectrometry, and inductively coupled plasma mass spectrometry. Based on interpretation of these data, the geochemical and geodynamic features of this stage of volcanism were established; the source of magmogenesis was revealed, represented by garnet peridotites. The withinplate plume–continental nature of the alkaline basaltoids was established, indicated by the high alkalinity and potassium content of rocks, Ta–Nb maximum, high normalized La/Yb (22–28) and La/Sm (3–6) values, as well as high Ti/V, Nb/Y, Zr/Y, Zr/Hf, Th/Yb, and Nb/Ta indices close to chondrite. The withinplate nature is also to some degree confirmed by the closeness of the chemical features of Tsushima basaltoids to rocks of Zinbochu and Udalyanche volcanoes of the Central Asian withinplate province (CAWP) located to west from the Sea of Japan, and it was formed in the Late Cenozoic under the influence of the North Asian superplume.

Refinement of the Deep Structure and Tectonic Movement Kinematics in the Area of the 2001 Salsk Earthquake Based on New Geophysical Data

The article presents the results of a comprehensive study of seismotectonic, geological-geophysical, geodynamic, and seismological data in the region of the Salsk earthquake of May 22, 2001, M = 4.7, in the low-seismic region of the junction of the Scythian Plate and the East European Platform are presented. The parameters of this earthquake source associated with a deep tectonic structure identified by the microseismic sounding method (MSM) are estimated based on seismological and macroseismic data. The MSM section through the region of the Salsk earthquake was obtained by a submeridional profile about 65 km long across the strike of the Manych deflection zone. It was established that the hypocenter of the 2001 Salsk earthquake was confined to the Salsk fault zone included in the system of the Manych faults. This fault is expressed in a section in the form of a narrow subvertical strip with low seismic wave velocities traced from the Earth’s surface to a depth of more than 40 km. Immediately in the area of the earthquake below a depth of 10 km, the recognized fault zone has a local expansion at the point of transition through the plane when the sedimentary cover contacts with the Proterozoic basement. The assessment of the hypocentral position and source mechanism solution (a gently dipping thrust of the northern side at an angle of 25°–33°) correlates well here with the depth and inclination of the surface of the Proterozoic basement, the elements of which are also traced in the MSM section.

Geodynamic Complexes and Structures of Transbaikalia: Record in Gravity Data

Abstract —The Transbaikalian region comprises several known geologic structures: the Mesozoic Mongolia-Okhotsk orogen, the Cenozoic Baikal rift system, and the world largest Angara–Vitim granitic batholith. They all formed upon heterogeneous Neoproterozoic– Early Paleozoic continental-margin complexes of the Siberian craton. The region is subject to the influence of mantle plumes, which induced Mesozoic–Cenozoic volcanism and controlled structural and lithological changes in the crust in the early history. Transbaikalia, which has been a scene of multiple tectonic events, is a model area for geophysical (in particular, gravity) surveys for various geological and geodynamic applications. As a novel approach, we interpret geological and geodynamic data from the region with reference to the pattern of free-air and Bouguer gravity anomalies revealed by satellite altimetry. Bouguer anomalies highlight large structures in the lithospheric mantle which were produced in the Cenozoic mainly by the activity of mantle plumes. Basaltic lava fields were confirmed to be almost coeval with mantle anomalies and to record the presence of the plume head at the crustal base. However, the origin of the Late Paleozoic Angara–Vitim granitic batholith was only tentatively attributed to the plume activity, based on gravity data. Mesozoic metamorphic core complexes (MCC) and basins that formed during the evolution of the Mongolia–Okhotsk orogen show up clearly on the map of free-air anomalies. Most of the MCC revealed in Transbaikalia coincide with oval gravity highs and border negative elongate features corresponding to Mesozoic basins. The zone of Cenozoic tectonism stands out in the pattern of free-air anomalies as maximum gravity contrasts, with the values changing from –110 to –120 mGal in basins to + 90 or +100 mGal in ranges. This zone encompasses rift basins filled with Cenozoic or, locally, Mesozoic sediments, which jointly form a domino-like system of rhomb-shaped structures typical of the Baikal rift system and, in general, of Cenozoic Central Asia resulted from the far-field effect of the India–Eurasia collision.

Tectonic position, geological manifestations of sources, and aftershock processes for a series of strong earthquakes of 2016–2017 in central Italy

Based on seismological, geodynamic, and seismotectonic data on a series of strong earthquakes which occurred in 2016–2017 in central Italy, the tectonic positions and geological manifestations of these events are determined. The aftershock processes of these earthquakes are studied. It is found that epicentral clouds of mainshocks and aftershocks almost overlapped each other, so these earthquake sources in aggregate can be classified as a high-magnitude earthquake swarm.

An overview of the Mesozoic-Cenozoic magmatism and tectonics in Eastern Paraguay and central Andes (Western Gondwana): Implications for the composition of mantle sources

The amalgamation of the Western Gondwana (including the Greater Gondwana supercraton) occurred at 600 Ma during the Brazilian – Pan African orogeny. A plate junction related to this event is marked by the Transbrazilian lineament which separates the South American continent into two sectors: the Eastern Paraguay-Brazilian and Central Andean domains. An overview of the geodynamic data from these two sectors indicates that the two domains were subjected to distinct evolutions from the Proterozoic to the present. The Andean domain is characterized by long-lived subduction processes linked to the convergence and consequent collision of microplates since the Middle Proterozoic (western Amazonian Craton) with a peak at about 600–580 Ma. The Paraguay-Brazilian domain remained relatively stable but was affected by extension episodes that reactivated ancient (Early and Middle Proterozoic) suture zones. These different geodynamic evolutions seem to reflect broadly distinct mantle compositions. In the subduction zones of the Andean domain the mantle was deeply modified by metasomatic processes following the subduction of oceanic plates. Consequently, the Andean type magma sources show a clear HIMU imprint inherited from the MORB, whereas the Paraguay-Brazilian sector shows a prevalent EMI and subordinate EMII character. The petrological data mainly from Mesozoic and Cenozoic magmatic events in the two sectors are reviewed to investigate the current mantle plume and mantle dome models for the uprising of the asthenospheric (or sub-lithospheric) material.