Pub Date : 2021-12-15DOI: 10.5800/gt-2021-12-4-0567
S. M. Makeev
The article deals with the fundamental concepts of a new method of interpretation of regional gravimetry (scale 1:1 000 000) based on the idea of the deformational nature of low-frequency gravity anomalies. The method provided an opportunity to identify the direction of tectonic compression in the Yakut diamond-bearing province, to localize segments and axes of inter-shear compression and extension of different kinematics and on that basis to distinguish the shear interaction zones spatially correlating with the location of kimberlite pipes. Particularly, the whole area is characterized by four transpressive compression directions: a pair of orthogonal (dextral with azimuth 8° and sinistral with azimuth 98°) and a pair of diagonal (dextral with azimuth 38° and sinistral with azimuth 128°). These data correlate to those from the regional tectonophysical studies not only within the compression direction azimuths but also within kinematics of transpressive motions for two main phases in geodynamical evolution of the Yakutsk diamond-bearing province (YDP) predominantly dextral for the first phase of the northeastern compression and sinistral for second phase of the northwestern compression. The article also shows that the Alakit-Olenek mineragenic zone is an extensive (~500 km) area of plastic deformation of rocks ~90 km in width with the right-lateral kinematics of apparent motions of the rocks along its northern and southern boundaries. The southern boundary of the mineragenic zone exhibits the northeaststriking continuity whereas its northern boundary is discontinuous. The boundaries of the Alakit-Olenek mineragenic zone are controlled by the zones of shear interaction of different dynamics and kinematics, which are spatially related to kimberlite pipes and diamond placer deposits. The results of this study imply that the method proposed for interpretation of gravity field can predict the occurrence of structures of geodynamic control of kimberlite magmatism of the Yakut diamond-bearing province.
{"title":"STRUCTURAL-GEODYNAMIC CONTROL OF KIMBERLITE PIPES OF THE YAKUT DIAMOND PROVINCE ACCORDING TO THE DATA OF GRAVISTRUCTURAL ANALYSIS","authors":"S. M. Makeev","doi":"10.5800/gt-2021-12-4-0567","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0567","url":null,"abstract":"The article deals with the fundamental concepts of a new method of interpretation of regional gravimetry (scale 1:1 000 000) based on the idea of the deformational nature of low-frequency gravity anomalies. The method provided an opportunity to identify the direction of tectonic compression in the Yakut diamond-bearing province, to localize segments and axes of inter-shear compression and extension of different kinematics and on that basis to distinguish the shear interaction zones spatially correlating with the location of kimberlite pipes. Particularly, the whole area is characterized by four transpressive compression directions: a pair of orthogonal (dextral with azimuth 8° and sinistral with azimuth 98°) and a pair of diagonal (dextral with azimuth 38° and sinistral with azimuth 128°). These data correlate to those from the regional tectonophysical studies not only within the compression direction azimuths but also within kinematics of transpressive motions for two main phases in geodynamical evolution of the Yakutsk diamond-bearing province (YDP) predominantly dextral for the first phase of the northeastern compression and sinistral for second phase of the northwestern compression. The article also shows that the Alakit-Olenek mineragenic zone is an extensive (~500 km) area of plastic deformation of rocks ~90 km in width with the right-lateral kinematics of apparent motions of the rocks along its northern and southern boundaries. The southern boundary of the mineragenic zone exhibits the northeaststriking continuity whereas its northern boundary is discontinuous. The boundaries of the Alakit-Olenek mineragenic zone are controlled by the zones of shear interaction of different dynamics and kinematics, which are spatially related to kimberlite pipes and diamond placer deposits. The results of this study imply that the method proposed for interpretation of gravity field can predict the occurrence of structures of geodynamic control of kimberlite magmatism of the Yakut diamond-bearing province.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74694827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0559
I. Prokopyev, A. Doroshkevich, A. Malyutina, A. Starikova, A. Ponomarchuk, D. Semenova, S. A. Kovalev, I. A. Savinsky
The Chadobets alkaline ultramafic carbonatite complex is located on the Siberian craton within the southern boundary of the Permian-Triassic plume activity. The dating of xenogenic zircons from the weathering crust of carbonatites of the Chuktukon complex yielded four clusters with ages of 1870–1820, 495–385, 290–210 and 215–162 Ma. The first two clusters correspond to the dates of activity of Paleoproterozoic granitoid magmatism and Paleozoic alkaline-mafic tectono-magmatic activity, widely occurred in the Siberian craton and its southern framing. The age of crystallization of alkaline rocks of the Chadobets complex falls within the interval of 255–240 Ma. Ar-Ar dating of damtjernite and carbonatite minerals of the Chuktukon complex falls within the intervals of 250.5±3.7 and 247.1±5.7 Ma, respectively. The crystallization ages of the mela-aillikites and damtjernites of the Terina complex, according to the Ar-Ar dating, correspond to the intervals of 257.4±3.9, 241.1±3.7, and 240±3.6 Ma. The age interval of 215–162 Ma based on zircons from the carbonatite weathering crust of the Chuktukon complex reflects the geochronology of superimposed processes and indicates the different stages of alteration of igneous rocks of the Chadobets complex. The data obtained on the age of crystallization of alkaline rocks of the Chadobets complex are consistent with the age interval of Siberian plume activity within a large igneous province (LIP).
{"title":"GEOCHRONOLOGY OF THE CHADOBETS ALKALINE ULTRAMAFIC CARBONATITE COMPLEX (SIBERIAN CRATON): NEW U-Pb AND Ar-Ar DATA","authors":"I. Prokopyev, A. Doroshkevich, A. Malyutina, A. Starikova, A. Ponomarchuk, D. Semenova, S. A. Kovalev, I. A. Savinsky","doi":"10.5800/gt-2021-12-4-0559","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0559","url":null,"abstract":"The Chadobets alkaline ultramafic carbonatite complex is located on the Siberian craton within the southern boundary of the Permian-Triassic plume activity. The dating of xenogenic zircons from the weathering crust of carbonatites of the Chuktukon complex yielded four clusters with ages of 1870–1820, 495–385, 290–210 and 215–162 Ma. The first two clusters correspond to the dates of activity of Paleoproterozoic granitoid magmatism and Paleozoic alkaline-mafic tectono-magmatic activity, widely occurred in the Siberian craton and its southern framing. The age of crystallization of alkaline rocks of the Chadobets complex falls within the interval of 255–240 Ma. Ar-Ar dating of damtjernite and carbonatite minerals of the Chuktukon complex falls within the intervals of 250.5±3.7 and 247.1±5.7 Ma, respectively. The crystallization ages of the mela-aillikites and damtjernites of the Terina complex, according to the Ar-Ar dating, correspond to the intervals of 257.4±3.9, 241.1±3.7, and 240±3.6 Ma. The age interval of 215–162 Ma based on zircons from the carbonatite weathering crust of the Chuktukon complex reflects the geochronology of superimposed processes and indicates the different stages of alteration of igneous rocks of the Chadobets complex. The data obtained on the age of crystallization of alkaline rocks of the Chadobets complex are consistent with the age interval of Siberian plume activity within a large igneous province (LIP).","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89762861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0558
I. Derbeko, G. Kirillova, E. Bugdaeva, V. Markevich
The Mongol-Okhotsk orogenic belt, finally formed in the end of the Mesozoic as a result of later tectonic events, is divided into two flanks: western and eastern. Its formation is obviously due to a regular change in geodynamic events significantly obscured by late tectonic and magmatic processes in the western flank and more clearly defined in the eastern flank from both magmatic and stratified formations. The early changes in geodynamic environment are most clearly determined by the formation of magmatic complexes whose completion is usually accompanied by the strata formation. Stratons framing the eastern flank of the Mongol-Okhotsk orogenic belt in the Mesozoic were formed in sedimentary basins, which are currently isolated to the Krestovkinsky and Ogodzhinsky basins along the southern border and to the Strelkinsky, Malotyndinsky, Toromsky and Udsky basins along the northern border. The deposition environment varied from deep-sea marine to continental. The article attempts to correlate the cross-sections of sedimentary basins on the framing of the eastern Mongol-Okhotsk orogenic belt and considers similarity or difference in their structure, conditions of sedimentation, tectonic positions and dependence of their evolution on geodynamic processes in the region.
{"title":"THE ROLE OF MESOZOIC GEODYNAMIC EVENTS IN FORMATION OF SEDIMENTARY BASINS ON THE FRAMING OF THE EASTERN MONGOL-OKHOTSK OROGENIC BELT","authors":"I. Derbeko, G. Kirillova, E. Bugdaeva, V. Markevich","doi":"10.5800/gt-2021-12-4-0558","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0558","url":null,"abstract":"The Mongol-Okhotsk orogenic belt, finally formed in the end of the Mesozoic as a result of later tectonic events, is divided into two flanks: western and eastern. Its formation is obviously due to a regular change in geodynamic events significantly obscured by late tectonic and magmatic processes in the western flank and more clearly defined in the eastern flank from both magmatic and stratified formations. The early changes in geodynamic environment are most clearly determined by the formation of magmatic complexes whose completion is usually accompanied by the strata formation. Stratons framing the eastern flank of the Mongol-Okhotsk orogenic belt in the Mesozoic were formed in sedimentary basins, which are currently isolated to the Krestovkinsky and Ogodzhinsky basins along the southern border and to the Strelkinsky, Malotyndinsky, Toromsky and Udsky basins along the northern border. The deposition environment varied from deep-sea marine to continental. The article attempts to correlate the cross-sections of sedimentary basins on the framing of the eastern Mongol-Okhotsk orogenic belt and considers similarity or difference in their structure, conditions of sedimentation, tectonic positions and dependence of their evolution on geodynamic processes in the region.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86866633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0564
D. Safonov
ABSTRACT. The study has been done on the field of the principal tectonic stresses direction at intermediate depths of earthquakes of the southern flank of the Kuril-Kamchatka subduction system separately for the upper and lower double seismic focal zones. Use has been made of the NIED and GlobalCMT catalogue data. The computation-based results are presented on schemes of the stressed state of the investigated areas and in tables. In the context of the southern Kuril Islands, evidence has been provided for predominance of the maximum compressive stresses along the slab plane in the upper layer and minimal compressive stresses (deviatoric extension) in the lower layer. However, the principal axes of maximum and minimum compression are displaced in direction relative to the slab dip: by 30–40° counterclockwise for the compression axis in the upper layer, which coincides with the direction of plate movement, and clockwise for the extension axis in the lower layer. This might be caused by the right-lateral strike-slip component of the Pacific Plate subduction. Unlike the general trend, the orientation of the principal axes of the stress field beneath the central Hokkaido-related segments in the upper layer is almost identical to that in the lower layer. There have also been found the segments exposed to shear stress, with the most extensive located opposite the northern Kunashir Island and beneath the southern Hokkaido Island. The results obtained for major large groups of clusters show good accordance with those published by other authors. The discrepancies relate primarily to small groups of isolated clusters showing local stress field heterogeneities.
{"title":"TECTONIC STRESS FIELD AT INTERMEDIATE DEPTHS OF THE SOUTHERN FLANK OF THE KURIL-KAMCHATKA SEISMIC ZONE","authors":"D. Safonov","doi":"10.5800/gt-2021-12-4-0564","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0564","url":null,"abstract":"ABSTRACT. The study has been done on the field of the principal tectonic stresses direction at intermediate depths of earthquakes of the southern flank of the Kuril-Kamchatka subduction system separately for the upper and lower double seismic focal zones. Use has been made of the NIED and GlobalCMT catalogue data. The computation-based results are presented on schemes of the stressed state of the investigated areas and in tables. In the context of the southern Kuril Islands, evidence has been provided for predominance of the maximum compressive stresses along the slab plane in the upper layer and minimal compressive stresses (deviatoric extension) in the lower layer. However, the principal axes of maximum and minimum compression are displaced in direction relative to the slab dip: by 30–40° counterclockwise for the compression axis in the upper layer, which coincides with the direction of plate movement, and clockwise for the extension axis in the lower layer. This might be caused by the right-lateral strike-slip component of the Pacific Plate subduction. Unlike the general trend, the orientation of the principal axes of the stress field beneath the central Hokkaido-related segments in the upper layer is almost identical to that in the lower layer. There have also been found the segments exposed to shear stress, with the most extensive located opposite the northern Kunashir Island and beneath the southern Hokkaido Island. The results obtained for major large groups of clusters show good accordance with those published by other authors. The discrepancies relate primarily to small groups of isolated clusters showing local stress field heterogeneities.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73266852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0563
O. Polyansky, A. Babichev, A. Semenov, V. Reverdatto
Deviations of the РТ parameters from the background values, corresponding to the lithostatic pressure and the standard geotherm characteristic of the neighboring crustal blocks of the Yenisei Ridge, were recorded by geothermobarometry in the zones of dislocation metamorphism of the Yenisei regional shear zone (Eastern Siberia). To explain the reason for large deviations from metamorphic conditions for shear and collision, we worked out 3D and 2D thermomechanical numerical models. The paper presents twoand three-dimensional models of dissipative heating during friction and visco-plastic deformations. The modelling results are compared with geological observations on the metamorphic grade and the scale of deformations of the Yenisei regional shear zone. A detailed consideration is being given to the ratio of heat released during friction at the contact of shear fault blocks, or during viscous deformations of the rheologically layered zone of tectonic flow and blastomylonitization. Estimates of the magnitude of dissipative heating are obtained for typical parameters of shear zones. The model of viscous deformation of a shear zone of finite width, taking into account the rheological layering of the crust, predicts dissipative heating by 200–310 °C at strain rates of 2–4 cm/year. The model of obduction of the tectonic plate with a thrusting velocity of 5 cm/year yields estimates of frictional heating of rocks at the contact of blocks no higher than 130–190 °C. The characteristic time period of the stationary dissipative regime formation is 6–8 million years. Dissipative heating could be a heat source for the metamorphic complexes of the Yenisei regional shear zone, though melting conditions of metapelite were not attained.
{"title":"MODELLING HEAT GENERATION DURING FRICTION AND VISCOPLASTIC DEFORMATION BASED ON THE EXAMPLE OF THE YENISEI SHEAR ZONE (EASTERN SIBERIA)","authors":"O. Polyansky, A. Babichev, A. Semenov, V. Reverdatto","doi":"10.5800/gt-2021-12-4-0563","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0563","url":null,"abstract":"Deviations of the РТ parameters from the background values, corresponding to the lithostatic pressure and the standard geotherm characteristic of the neighboring crustal blocks of the Yenisei Ridge, were recorded by geothermobarometry in the zones of dislocation metamorphism of the Yenisei regional shear zone (Eastern Siberia). To explain the reason for large deviations from metamorphic conditions for shear and collision, we worked out 3D and 2D thermomechanical numerical models. The paper presents twoand three-dimensional models of dissipative heating during friction and visco-plastic deformations. The modelling results are compared with geological observations on the metamorphic grade and the scale of deformations of the Yenisei regional shear zone. A detailed consideration is being given to the ratio of heat released during friction at the contact of shear fault blocks, or during viscous deformations of the rheologically layered zone of tectonic flow and blastomylonitization. Estimates of the magnitude of dissipative heating are obtained for typical parameters of shear zones. The model of viscous deformation of a shear zone of finite width, taking into account the rheological layering of the crust, predicts dissipative heating by 200–310 °C at strain rates of 2–4 cm/year. The model of obduction of the tectonic plate with a thrusting velocity of 5 cm/year yields estimates of frictional heating of rocks at the contact of blocks no higher than 130–190 °C. The characteristic time period of the stationary dissipative regime formation is 6–8 million years. Dissipative heating could be a heat source for the metamorphic complexes of the Yenisei regional shear zone, though melting conditions of metapelite were not attained.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72837476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0557
V. Simonov, A. V. Kulikova, A. Kotlyarov, T. B. Kolotilina
The Geochemical and mineralogical studies showed, that harzburgites of the Chagan-Uzun massif are restites with a degree of partial melting 15–20 %, which formed at temperatures 1520–1420 °С under the conditions of the mid-oceanic ridge and transformed during the evolution of paleooceanic structures under the influence of magmatic processes at the initial stages of subduction and manifestation of boninite magmatism. The combined use of data on the geochemistry of rare and rare earth elements, as well as on the compositions of pyroxenes, Cr-spinels, melt inclusions in Cr-spinels and computational modeling, indicates the formation of clinopyroxenites of Chagan-Uzun ophiolites at the mid-oceanic ridge during crystallization of picrite and picrobasalt melts at temperatures 1315–1245 °C and pressures 4–2 kbar. The study of amphiboles showed high metamorphic parameters of transformation of harzburgites (5.1–1.9 kbar, 820–700 °С) and clinopyroxenites (2.6–1.4 kbar and 740–680 °С) of the Chagan-Uzun massif, typical for ultrabasites from the modern mid-oceanic ridges. In general, results of comprehensive studies made it possible to determine the sequence of paleogeodynamic processes of formation of ultramafic rocks of the Chagan-Uzun massif. Initial formation of harzburgites in the course of partial melting of mantle and crystallization of clinopyroxenites in the magma chamber occurred under the conditions of the mid-oceanic ridge. At the next stage, ultramafic rocks fell within the subduction-zone initiation area, where they were exposed to the influence of boninite melts.
{"title":"PALEOGEODYNAMICS OF MAGMATIC AND METAMORPHIC PROCESSES OF FORMATION OF ULTRAMAFIC ROCKS OF CHAGAN-UZUN MASSIF (OPHIOLITES OF GORNY ALTAI)","authors":"V. Simonov, A. V. Kulikova, A. Kotlyarov, T. B. Kolotilina","doi":"10.5800/gt-2021-12-4-0557","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0557","url":null,"abstract":"The Geochemical and mineralogical studies showed, that harzburgites of the Chagan-Uzun massif are restites with a degree of partial melting 15–20 %, which formed at temperatures 1520–1420 °С under the conditions of the mid-oceanic ridge and transformed during the evolution of paleooceanic structures under the influence of magmatic processes at the initial stages of subduction and manifestation of boninite magmatism. The combined use of data on the geochemistry of rare and rare earth elements, as well as on the compositions of pyroxenes, Cr-spinels, melt inclusions in Cr-spinels and computational modeling, indicates the formation of clinopyroxenites of Chagan-Uzun ophiolites at the mid-oceanic ridge during crystallization of picrite and picrobasalt melts at temperatures 1315–1245 °C and pressures 4–2 kbar. The study of amphiboles showed high metamorphic parameters of transformation of harzburgites (5.1–1.9 kbar, 820–700 °С) and clinopyroxenites (2.6–1.4 kbar and 740–680 °С) of the Chagan-Uzun massif, typical for ultrabasites from the modern mid-oceanic ridges. In general, results of comprehensive studies made it possible to determine the sequence of paleogeodynamic processes of formation of ultramafic rocks of the Chagan-Uzun massif. Initial formation of harzburgites in the course of partial melting of mantle and crystallization of clinopyroxenites in the magma chamber occurred under the conditions of the mid-oceanic ridge. At the next stage, ultramafic rocks fell within the subduction-zone initiation area, where they were exposed to the influence of boninite melts.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80486216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0565
A. O. Agibalov, V. Zaitsev, A. Sentsov
The paper presents the results of comparative neogeodynamic analysis of the Baltic syneclise and northern Voronezh anteclise based on structural-geomorphological interpretation, digital elevation model (DEM) processing procedure using LESSA program [Zlatopolsky, 2011], seismic analysis, and computer geodynamic modeling. Both regions are seismically active areas of the East European Platform. The automated DEM analysis showed that they are dominated by NW-striking lineaments oriented across the strike of the neoextension axis. Computational neogeodynamic models imply that the areas under consideration develop in shear environment, with the compression axis oriented northwest. Another important result of modeling is numerical correlation between earthquake energy, interpolated over the Baltic syneclise, and the probability of occurrence of ruptures: the Pearson correlation coefficient is 0.58 for the sedimentary cover and 0.42 for the basement. For the northern Voronezh anteclise, a correlation was found between the epicentral density of earthquakes and "Fracture regions" parameter, with reference to which there were distinguished the areas with the probable occurrence of new short-extension ruptures (the Pearson correlation coefficient is 0.41). This parameter is informative for contouring seismically active parts since the areas with probable occurrence of new ruptures, occupying 39 % of the northern Voronezh anteclise, account for 71 % of earthquake epicenters. Structuralgeomorphological interpretation yielded a high degree of correlation between relief and active faults identified as "weak" zones to which the earthquake epicenters are largely confined. Therefore, both regions considered are characterized by high sedimentary-cover seismic activity, develop in shear stress field, with the stress axis oriented northwest, and have similar orientations of linear elements of relief and "weak" zones. The analysis of the earthquake recurrence curves shows considerable differences between seismic regimes of the northern Voronezh anteclise and the Baltic syneclise, and those between the sedimentary-cover and basement seismicity of the latter. These differences may be due the fact that the stressed state of the Voronezh anteclise is affected by active structures of the Urals and Caucasus, and that the upwarping Fennoscandian shield is largely responsible for neodeformations of the Baltic syneclise. Practical significance of the study is concerned with the identification of earthquake source zones.
{"title":"COMPARATIVE ANALYSIS OF NEOGEODYNAMICS OF THE BALTIC SYNECLISE AND THE NORTHERN SLOPE OF THE VORONEZH ANTECLISE A","authors":"A. O. Agibalov, V. Zaitsev, A. Sentsov","doi":"10.5800/gt-2021-12-4-0565","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0565","url":null,"abstract":"The paper presents the results of comparative neogeodynamic analysis of the Baltic syneclise and northern Voronezh anteclise based on structural-geomorphological interpretation, digital elevation model (DEM) processing procedure using LESSA program [Zlatopolsky, 2011], seismic analysis, and computer geodynamic modeling. Both regions are seismically active areas of the East European Platform. The automated DEM analysis showed that they are dominated by NW-striking lineaments oriented across the strike of the neoextension axis. Computational neogeodynamic models imply that the areas under consideration develop in shear environment, with the compression axis oriented northwest. Another important result of modeling is numerical correlation between earthquake energy, interpolated over the Baltic syneclise, and the probability of occurrence of ruptures: the Pearson correlation coefficient is 0.58 for the sedimentary cover and 0.42 for the basement. For the northern Voronezh anteclise, a correlation was found between the epicentral density of earthquakes and \"Fracture regions\" parameter, with reference to which there were distinguished the areas with the probable occurrence of new short-extension ruptures (the Pearson correlation coefficient is 0.41). This parameter is informative for contouring seismically active parts since the areas with probable occurrence of new ruptures, occupying 39 % of the northern Voronezh anteclise, account for 71 % of earthquake epicenters. Structuralgeomorphological interpretation yielded a high degree of correlation between relief and active faults identified as \"weak\" zones to which the earthquake epicenters are largely confined. Therefore, both regions considered are characterized by high sedimentary-cover seismic activity, develop in shear stress field, with the stress axis oriented northwest, and have similar orientations of linear elements of relief and \"weak\" zones. The analysis of the earthquake recurrence curves shows considerable differences between seismic regimes of the northern Voronezh anteclise and the Baltic syneclise, and those between the sedimentary-cover and basement seismicity of the latter. These differences may be due the fact that the stressed state of the Voronezh anteclise is affected by active structures of the Urals and Caucasus, and that the upwarping Fennoscandian shield is largely responsible for neodeformations of the Baltic syneclise. Practical significance of the study is concerned with the identification of earthquake source zones.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73869313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0556
E. Sklyarov, A. V. Lavrenchuk, A. Mazukabzov
The Olkhon terrane in the Western Baikal area accommodates four types of carbonate-silicate mixtures: injection (protrusion), metamorphic-boudinated, mingling, and tectonite marble mélange. The outcrops of injection mélange consist of a carbonate matrix with inclusions of native silicic rocks found in the immediate vicinities, commonly cover large areas and lack any distinct linearity in the map view. Mélange of the metamorphic boudinage type comprises diopsidite and tremilote-diopsidite fragments in a dolomitic or calcite-dolomitic matrix. Its origin is apparently due to tectonism and related metamorphism of quartz sandstones in Neoproterozoic strata on the passive margin of the Siberian craton. Mingling mélange appears as calcite marble or carbonate-silicate (calciphyre) veins with metadolerite and granite inclusions of different sizes. The veins formed by intrusion of carbonate and silicate melt batches and subsequent fragmentation of silicate rocks that crystallized earlier. Marble tectonites localized in narrow zones record the late phase of ductile marble injection.
{"title":"MARBLE MÉLANGE: COMPOSITION VARIATIONS AND FORMATION MECHANISMS","authors":"E. Sklyarov, A. V. Lavrenchuk, A. Mazukabzov","doi":"10.5800/gt-2021-12-4-0556","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0556","url":null,"abstract":"The Olkhon terrane in the Western Baikal area accommodates four types of carbonate-silicate mixtures: injection (protrusion), metamorphic-boudinated, mingling, and tectonite marble mélange. The outcrops of injection mélange consist of a carbonate matrix with inclusions of native silicic rocks found in the immediate vicinities, commonly cover large areas and lack any distinct linearity in the map view. Mélange of the metamorphic boudinage type comprises diopsidite and tremilote-diopsidite fragments in a dolomitic or calcite-dolomitic matrix. Its origin is apparently due to tectonism and related metamorphism of quartz sandstones in Neoproterozoic strata on the passive margin of the Siberian craton. Mingling mélange appears as calcite marble or carbonate-silicate (calciphyre) veins with metadolerite and granite inclusions of different sizes. The veins formed by intrusion of carbonate and silicate melt batches and subsequent fragmentation of silicate rocks that crystallized earlier. Marble tectonites localized in narrow zones record the late phase of ductile marble injection.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82178337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0560
T. V. Dudkin, A. Marfin, A. Ivanov, V. Kamenetsky
The paper considers the Pd/Pt ratio in the ores of the Norilsk-1 and Talnakh deposits associated with the Permian-Triassic intrusions of the Norilsk type in comparison with that in the lavas of the same age in the Norilsk region. The Pd/Pt mean ratio is 1 in lavas and 2–4 times higher than that in ores and barren horizons of the Norilsk-1 and Talnakh intrusions. Such an increase implies that these elements were borrowed by magma from small and medium-sized crust deposits associated with the previous stage of Permian island-arc volcanism.
{"title":"Pd/Pt IMBALANCE IN LAVAS AND INTRUSIONS OF THE NORILSK-TALNAKH ORE REGION","authors":"T. V. Dudkin, A. Marfin, A. Ivanov, V. Kamenetsky","doi":"10.5800/gt-2021-12-4-0560","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0560","url":null,"abstract":"The paper considers the Pd/Pt ratio in the ores of the Norilsk-1 and Talnakh deposits associated with the Permian-Triassic intrusions of the Norilsk type in comparison with that in the lavas of the same age in the Norilsk region. The Pd/Pt mean ratio is 1 in lavas and 2–4 times higher than that in ores and barren horizons of the Norilsk-1 and Talnakh intrusions. Such an increase implies that these elements were borrowed by magma from small and medium-sized crust deposits associated with the previous stage of Permian island-arc volcanism.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78953518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-14DOI: 10.5800/gt-2021-12-4-0561
S. K. Sahoo, M. Katlamudi, G. Udaya Lakshmi
We analyzed the ground geomagnetic data obtained from a 3-component fluxgate magnetometer at the Eyrewell Geomagnetic Observatory (New Zealand) (43.474 °S, 172.393 °E) from October 1 to December 31, 2016. The study aimed to investigate electromagnetic precursors associated with the M 7.8 New Zealand earthquake of November 13, 2016. This earthquake occurred 54 km northeast of Amberley (New Zealand). Its epicenter was located 158 km from the Eyrewell Observatory. We used three methods focused on the polarization ratio, fractal dimension and principal component analysis to identify anomalies in the geomagnetic data. The time series showed an enhanced polarization ratio at two times, October 20 and October 30, 2016, i.e. before the occurrence of the New Zealand earthquake, and a value ~1 or more during these instances. Since the global geomagnetic indices Kp and Dst were normal in these cases, the enhanced polarization ratio may be related to the preparation phase of the New Zealand earthquake. To further classify them, we applied the principal component analysis to the magnetic data on component H. The first three principal components showed more than 90 % of the variance of the original ultra-low frequency (ULF) magnetic field time series. The first principal component was found to be well correlated with the storm index (Dst) recorded during this period. Again, the second principal component was dominated by daily variations, which were the periodic component of the recorded ULF magnetic field. The temporal variation of the third principal component was analyzed to verify a possible correlation between the ULF emissions and the occurrence of the earthquake. The fractal dimension of components D and Z of the magnetic data decreased initially and sharply increased three days before the New Zealand earthquake.
{"title":"OBSERVATION OF ULF ELECTROMAGNETIC EMISSIONS BEFORE THE M 7.8 NEW ZEALAND EARTHQUAKE OF NOVEMBER 13, 2016","authors":"S. K. Sahoo, M. Katlamudi, G. Udaya Lakshmi","doi":"10.5800/gt-2021-12-4-0561","DOIUrl":"https://doi.org/10.5800/gt-2021-12-4-0561","url":null,"abstract":"We analyzed the ground geomagnetic data obtained from a 3-component fluxgate magnetometer at the Eyrewell Geomagnetic Observatory (New Zealand) (43.474 °S, 172.393 °E) from October 1 to December 31, 2016. The study aimed to investigate electromagnetic precursors associated with the M 7.8 New Zealand earthquake of November 13, 2016. This earthquake occurred 54 km northeast of Amberley (New Zealand). Its epicenter was located 158 km from the Eyrewell Observatory. We used three methods focused on the polarization ratio, fractal dimension and principal component analysis to identify anomalies in the geomagnetic data. The time series showed an enhanced polarization ratio at two times, October 20 and October 30, 2016, i.e. before the occurrence of the New Zealand earthquake, and a value ~1 or more during these instances. Since the global geomagnetic indices Kp and Dst were normal in these cases, the enhanced polarization ratio may be related to the preparation phase of the New Zealand earthquake. To further classify them, we applied the principal component analysis to the magnetic data on component H. The first three principal components showed more than 90 % of the variance of the original ultra-low frequency (ULF) magnetic field time series. The first principal component was found to be well correlated with the storm index (Dst) recorded during this period. Again, the second principal component was dominated by daily variations, which were the periodic component of the recorded ULF magnetic field. The temporal variation of the third principal component was analyzed to verify a possible correlation between the ULF emissions and the occurrence of the earthquake. The fractal dimension of components D and Z of the magnetic data decreased initially and sharply increased three days before the New Zealand earthquake.","PeriodicalId":44925,"journal":{"name":"Geodynamics & Tectonophysics","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81257267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：