Pub Date : 2021-01-01DOI: 10.21638/spbu07.2021.208
A. A. Peshkov, A. Chernyshov
The objects of study are the Agardag and Ulor ultramafic massifs, which are part of the South Tuva ophiolite belt. The aim of this work is to study the petrographic, petrochemical and geochemical features of harzburgites and dunites of the studied massifs. As a result of petrographic study, the main types of rocks that make up the studied massifs were identified. Harzburgites predominate in the Agardag massif, while dunites are more common in the Ulor massif. In the Ulor massif, dunites and harzburgites are often plastically deformed by syntectonic recrystallization with the formation of porphyroclastic structures. The chemical compositions of olivine and Cr-spinels in harzburgites and dunites in both massifs are similar. The composition of olivine corresponds to forsterite, while the ultramafic rocks of the Ulor massif show large variations in Fa and a tendency towards a decrease in NiO. Chromium spinels in ultramafic rocks of the Ulor massif have wider compositional variations and are represented by chromites, alumochromite and subferrial alumochromite; they are completely free of V2O5. According to the composition of Cr-spinels, the degree of melting of ultramafic rocks was determined, which turned out to be similar for both massifs, ~40–50%. A higher chromium content of the ultramafic rocks of the Agardag massif is noted, which is probably responsible for its increased potential chromite content. Ultramafic rocks of the Agardag and Ulor massifs are intensely depleted formations that arose in similar conditions, which determines the closeness of their rock and material compositions. The revealed differences are due to variations in the degree of depletion and the conditions of their consolidation in the earth's crust, determined by the structural position, as well as metamorphism of the enclosing frame and the introduction of later intrusions.
{"title":"Petrographic and petrogeochemical features of harzburgites and dunites of the Agardag and Ulor massifs (South-Eastern Tyva)","authors":"A. A. Peshkov, A. Chernyshov","doi":"10.21638/spbu07.2021.208","DOIUrl":"https://doi.org/10.21638/spbu07.2021.208","url":null,"abstract":"The objects of study are the Agardag and Ulor ultramafic massifs, which are part of the South Tuva ophiolite belt. The aim of this work is to study the petrographic, petrochemical and geochemical features of harzburgites and dunites of the studied massifs. As a result of petrographic study, the main types of rocks that make up the studied massifs were identified. Harzburgites predominate in the Agardag massif, while dunites are more common in the Ulor massif. In the Ulor massif, dunites and harzburgites are often plastically deformed by syntectonic recrystallization with the formation of porphyroclastic structures. The chemical compositions of olivine and Cr-spinels in harzburgites and dunites in both massifs are similar. The composition of olivine corresponds to forsterite, while the ultramafic rocks of the Ulor massif show large variations in Fa and a tendency towards a decrease in NiO. Chromium spinels in ultramafic rocks of the Ulor massif have wider compositional variations and are represented by chromites, alumochromite and subferrial alumochromite; they are completely free of V2O5. According to the composition of Cr-spinels, the degree of melting of ultramafic rocks was determined, which turned out to be similar for both massifs, ~40–50%. A higher chromium content of the ultramafic rocks of the Agardag massif is noted, which is probably responsible for its increased potential chromite content. Ultramafic rocks of the Agardag and Ulor massifs are intensely depleted formations that arose in similar conditions, which determines the closeness of their rock and material compositions. The revealed differences are due to variations in the degree of depletion and the conditions of their consolidation in the earth's crust, determined by the structural position, as well as metamorphism of the enclosing frame and the introduction of later intrusions.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82657054","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 : 2021-01-01DOI: 10.21638/spbu07.2021.407
T. Isachenko, G. A. Isachenko, S. Ozerova
The results of research on the key area "Sestra River" (229 km2), located within St. Petersburg and the Leningrad region, are considered. The study of recreational development of the territory was carried out in 2009-2010 and 2019-2020 using field surveys, analysis of topographic maps of different times and satellite images. Maps of recreational development of the model territory for the 1960s, 2010, and 2020 were compiled. In 2010, 16 types of land use were identified as the territories that have a recreational function as the main or additional one; this number does not include complexes with a primary residential and additional recreational function (cottage settlements, etc.). In 2020, 17 types of such territories were identified. Comparison of maps of recreational development revealed qualitative changes in various recreational complexes in 2010-2020: collective gardens, social dachas, year-round and seasonal complexes with low-rise buildings, cultural entertainment and sports-entertainment centers, etc. Over 10 years, the share of the area of recreational and residential-recreational complexes at the "Sestra River" key area has increased from 4.8 to 5.2 %. Recreational activities are being diversified. While preserving its traditional types, new types appear: farms with a recreational function, rope parks, entertainment complexes, etc. Recreational complexes for year-round use with low-rise buildings on forest land are being created. Cottage development becomes comparable to recreational development of the territory. A significant part of the houses in cottage and dacha settlements and collective gardens are used as permanent residence; at the same time, their recreational function becomes additional. Increasing the area of cottage settlements on forest land reduces the availability of landscapes of high recreational value for the population. Recreational transformation of territories, which is inseparable from suburbanization in the zones of influence of major cities, is rapidly changing the landscapes.
{"title":"Dynamics of the spatial organization of recreation in the zone of influence of St. Petersburg in the second decade of the 21st century","authors":"T. Isachenko, G. A. Isachenko, S. Ozerova","doi":"10.21638/spbu07.2021.407","DOIUrl":"https://doi.org/10.21638/spbu07.2021.407","url":null,"abstract":"The results of research on the key area \"Sestra River\" (229 km2), located within St. Petersburg and the Leningrad region, are considered. The study of recreational development of the territory was carried out in 2009-2010 and 2019-2020 using field surveys, analysis of topographic maps of different times and satellite images. Maps of recreational development of the model territory for the 1960s, 2010, and 2020 were compiled. In 2010, 16 types of land use were identified as the territories that have a recreational function as the main or additional one; this number does not include complexes with a primary residential and additional recreational function (cottage settlements, etc.). In 2020, 17 types of such territories were identified. Comparison of maps of recreational development revealed qualitative changes in various recreational complexes in 2010-2020: collective gardens, social dachas, year-round and seasonal complexes with low-rise buildings, cultural entertainment and sports-entertainment centers, etc. Over 10 years, the share of the area of recreational and residential-recreational complexes at the \"Sestra River\" key area has increased from 4.8 to 5.2 %. Recreational activities are being diversified. While preserving its traditional types, new types appear: farms with a recreational function, rope parks, entertainment complexes, etc. Recreational complexes for year-round use with low-rise buildings on forest land are being created. Cottage development becomes comparable to recreational development of the territory. A significant part of the houses in cottage and dacha settlements and collective gardens are used as permanent residence; at the same time, their recreational function becomes additional. Increasing the area of cottage settlements on forest land reduces the availability of landscapes of high recreational value for the population. Recreational transformation of territories, which is inseparable from suburbanization in the zones of influence of major cities, is rapidly changing the landscapes.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75289869","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 : 2021-01-01DOI: 10.21638/spbu07.2021.402
A. V. Moiseev, S. Sokolov, T. N. Palechek
Geological structure and age of the volcanogenic-sedimentary complex of the Cape Svyatoi Nos (Svyatonosskaya formation) are presented. The rocks of Cape Svyatoi Nos are located on the border of the Novosibirsk-Chukotka and Verkhoyansk–Kolyma fold belts, on the coast of the Laptev and East- Siberian Seas. Field studies indicate that the rocks belong to a single volcanogenic-sedimentary complex. The maximum thickness of individual sections reaches up 700 m. Coarse-grained pyroclastic rocks with rare lava flows prevail on the north (on the coast of Laptev Sea). The proportion and dimension of volcanics and pyroclastic rocks decrease in the south, terrigenous rocks appear. In the modern structure, the rocks are deformed.Zircons of several populations were separated from the flow of basalts. Two, the most representative zircon populations are characterized by close subconcordant ages. The structure and U-Pb ages of zircons from the first population suggest their formation during magmatic crystallization with a superimposed postmagmatic thermal event. Zircons of the second population have a xenomorphic appearance, which is typical of zircons formed at the late or postmagmatic phases. The weighted average age (MSWD = 3) of the first two populations is 149.3 ± 1.2 Ma (Tithonian age). It corresponds to the age of crystallization of basalts and the superimposed (close in time) postmagmatic thermal event.The third population of zircons is represented by two rounded grains with Archean U-Pb ages. It is assumed that these grains were trapped by magmatic melt from pre-Jurassic clastic rocks.Late Jurassic-Early Cretaceous radiolarians were identified from different horizons of tuff-terrigenous and terrigenous rocks. This is confirm the obtained U-Pb ages and the coeval of all the studied sections. The Titonian age of volcanic-sedimentary rocks allows us to classify them as suprasubduction complexes of the Late Jurassic - Early Cretaceous, widespread in the Verkhoyansk-Chukotka Mesozoids.
{"title":"Age of volcanic-sedimentary complex from Сape Svyatoi Nos (Eastern Arctic)","authors":"A. V. Moiseev, S. Sokolov, T. N. Palechek","doi":"10.21638/spbu07.2021.402","DOIUrl":"https://doi.org/10.21638/spbu07.2021.402","url":null,"abstract":"Geological structure and age of the volcanogenic-sedimentary complex of the Cape Svyatoi Nos (Svyatonosskaya formation) are presented. The rocks of Cape Svyatoi Nos are located on the border of the Novosibirsk-Chukotka and Verkhoyansk–Kolyma fold belts, on the coast of the Laptev and East- Siberian Seas. Field studies indicate that the rocks belong to a single volcanogenic-sedimentary complex. The maximum thickness of individual sections reaches up 700 m. Coarse-grained pyroclastic rocks with rare lava flows prevail on the north (on the coast of Laptev Sea). The proportion and dimension of volcanics and pyroclastic rocks decrease in the south, terrigenous rocks appear. In the modern structure, the rocks are deformed.Zircons of several populations were separated from the flow of basalts. Two, the most representative zircon populations are characterized by close subconcordant ages. The structure and U-Pb ages of zircons from the first population suggest their formation during magmatic crystallization with a superimposed postmagmatic thermal event. Zircons of the second population have a xenomorphic appearance, which is typical of zircons formed at the late or postmagmatic phases. The weighted average age (MSWD = 3) of the first two populations is 149.3 ± 1.2 Ma (Tithonian age). It corresponds to the age of crystallization of basalts and the superimposed (close in time) postmagmatic thermal event.The third population of zircons is represented by two rounded grains with Archean U-Pb ages. It is assumed that these grains were trapped by magmatic melt from pre-Jurassic clastic rocks.Late Jurassic-Early Cretaceous radiolarians were identified from different horizons of tuff-terrigenous and terrigenous rocks. This is confirm the obtained U-Pb ages and the coeval of all the studied sections. The Titonian age of volcanic-sedimentary rocks allows us to classify them as suprasubduction complexes of the Late Jurassic - Early Cretaceous, widespread in the Verkhoyansk-Chukotka Mesozoids.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72425889","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 : 2021-01-01DOI: 10.21638/SPBU07.2021.209
J. D. Ponomarev, A. Doroshkevich, I. Prokopyev, Dmitry A. Chebotarev
Apatite-bearing ore occurrence Muostalaah and phosphate deposit Birikeen are magnesiocarbonatite complexes of the Seligdar type, located within the Nimnyrskaya submeridional metallogenic domain in the Aldan-Stanovoy shield in South Yakutia, Russia. This study presents geochemical characteristics of carbonatites and adjacent apatite-bearing silicate rocks of the Birikeen apatite deposit and Muostalaah apatite occurrence. Comparison of these complexes with the Seligdar deposit and other magnesiocarbonatite complexes of the world was made. Based on the chemical analysis of the petrogenic components of the Muostalaah and Biriken carbonatites, it was concluded that these rocks belong to magnesiocarbonatites, similar to the magnesiocarbonatites of the Seligdar deposit. The chondrite-normalized REE spectra of magnesiocarbonatites and apatite rocks are characterized by LREE enrichment relative to HREE with average La/Yb(cn) ratios of 45 and 100 for the Muostalaah and Birikeen rocks, respectively. Most of the REE patterns are within the field of the world magnesiocarbonatites. The trace-elements abundances of carbonatites and apatite rocks record negative Nb, Pb, Sr, Zr, Hf and Ti anomalies and Th, U and REE enrichment. Сoncentrations of Th, U, Zr, and Hf are characterized by a wide spread of values. The trace-element patterns of the Birikeen and Muostalaah carbonatites are generally similar to the patterns of the world magnesiocarbonatites, including Seligdar rocks. Based on the results of isotopic studies of the Sm/Nd and Rb/Sr systems, it was concluded that the primary melts for the Muostalah and Birikeen carbonatites were formed from a long-lived enriched mantle source that separated from the depleted mantle in the Late Archean.
含磷灰石矿床Muostalaah和Birikeen磷矿床均为Seligdar型镁碳酸盐杂岩，位于俄罗斯南雅库特Aldan-Stanovoy盾域中的Nimnyrskaya俯冲成矿域中。本文研究了Birikeen磷灰石矿床和Muostalaah磷灰石产状的碳酸盐岩及其邻近含磷灰石硅酸盐岩的地球化学特征。并将这些配合物与Seligdar矿床及世界上其他镁碳酸盐配合物进行了比较。通过对Muostalaah和Biriken碳酸盐岩成因成分的化学分析，认为它们属于镁质碳酸盐岩，与Seligdar矿床的镁质碳酸盐岩相似。镁碳酸盐和磷灰石岩石的球粒陨石归一化稀土谱特征为轻稀土相对于重稀土富集，Muostalaah和Birikeen岩石的平均La/Yb(cn)比值分别为45和100。大部分稀土元素分布在世界菱镁碳酸盐场内。碳酸盐岩和磷灰石的微量元素丰度记录了Nb、Pb、Sr、Zr、Hf、Ti负异常和Th、U、REE富集。Th, U, Zr和Hf的Сoncentrations的特征值分布广泛。Birikeen和Muostalaah碳酸盐岩的微量元素模式与包括Seligdar岩石在内的世界镁质碳酸盐岩的模式大致相似。根据Sm/Nd体系和Rb/Sr体系的同位素研究结果，认为Muostalah和Birikeen碳酸盐岩的主要熔体形成于晚太古代从枯竭地幔分离出来的长寿命富集地幔源。
{"title":"Geochemical characteristics of magnesiocarbonatites from Muostalaah apatite occurrence and Birikeen apatite deposit (Aldan-Stanovoy shield, South Yakutia, Russia)","authors":"J. D. Ponomarev, A. Doroshkevich, I. Prokopyev, Dmitry A. Chebotarev","doi":"10.21638/SPBU07.2021.209","DOIUrl":"https://doi.org/10.21638/SPBU07.2021.209","url":null,"abstract":"Apatite-bearing ore occurrence Muostalaah and phosphate deposit Birikeen are magnesiocarbonatite complexes of the Seligdar type, located within the Nimnyrskaya submeridional metallogenic domain in the Aldan-Stanovoy shield in South Yakutia, Russia. This study presents geochemical characteristics of carbonatites and adjacent apatite-bearing silicate rocks of the Birikeen apatite deposit and Muostalaah apatite occurrence. Comparison of these complexes with the Seligdar deposit and other magnesiocarbonatite complexes of the world was made. Based on the chemical analysis of the petrogenic components of the Muostalaah and Biriken carbonatites, it was concluded that these rocks belong to magnesiocarbonatites, similar to the magnesiocarbonatites of the Seligdar deposit. The chondrite-normalized REE spectra of magnesiocarbonatites and apatite rocks are characterized by LREE enrichment relative to HREE with average La/Yb(cn) ratios of 45 and 100 for the Muostalaah and Birikeen rocks, respectively. Most of the REE patterns are within the field of the world magnesiocarbonatites. The trace-elements abundances of carbonatites and apatite rocks record negative Nb, Pb, Sr, Zr, Hf and Ti anomalies and Th, U and REE enrichment. Сoncentrations of Th, U, Zr, and Hf are characterized by a wide spread of values. The trace-element patterns of the Birikeen and Muostalaah carbonatites are generally similar to the patterns of the world magnesiocarbonatites, including Seligdar rocks. Based on the results of isotopic studies of the Sm/Nd and Rb/Sr systems, it was concluded that the primary melts for the Muostalah and Birikeen carbonatites were formed from a long-lived enriched mantle source that separated from the depleted mantle in the Late Archean.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85632536","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 : 2021-01-01DOI: 10.21638/spbu07.2021.403
E. Akimova, S. Skublov
The distribution of rare-earth elements (SIMS method) in minerals from the rocks of the Khitoostrov occurrence (Belomorian mobile belt of Eastern Fennoscandia) was studied: corundum-bearing metasomatites with anomalous isotopically light oxygen and hydrogen and garnet amphibolites after gabbro with normal isotopic composition. The study was accompanied by estimates of P-T parameters of rock formation using multi-equilibrium thermobarometry (TWEEQU method). Temperatures calculated for garnet amphibolites after gabbro fall within the range of 730–770 ° C, pressures - 13–14 kbar; for corundum-bearing rocks, temperatures were 680–710 ° C, pressures - 6.5–7.5 kbar. Corundum-bearing rocks were formed at slightly lower temperatures and at significantly lower pressures than garnet amphibolites after gabbro. The REE distribution spectra in garnets from apogabbroic amphibolites are characterized by a clearly pronounced slope from light to heavy REE, while in garnets from corundum-bearing rocks they have a less pronounced positive slope, which is associated with a noticeable enrichment of garnets in LREE and an insignificant depletion of HREE. Calcium amphiboles from corundum-bearing rocks are significantly enriched in rare-earth elements as compared to amphiboles from garnet amphibolites after gabbro, especially LREE (by more than an order of magnitude) and, to a lesser extent, MREE. Plagioclases from corundum-bearing rocks are also enriched in LREE against the background of garnet amphibolites. Thus, in all the studied minerals of corundum-bearing rocks LREE enrichment is recorded. It isn’t manifested in the minerals of amphibolites and, obviously, isn’t related to the difference in P-T parameters of rock formation. Consequently, LREE was transferred by a specific fluid during mineral-forming processes, which led to the formation of metasomatites with an anomalous isotopic composition of oxygen and hydrogen.
{"title":"Distribution of rare-earth elements in rock-forming minerals of corundum-bearing rocks of the Khitoostrov deposit (North Karelia)","authors":"E. Akimova, S. Skublov","doi":"10.21638/spbu07.2021.403","DOIUrl":"https://doi.org/10.21638/spbu07.2021.403","url":null,"abstract":"The distribution of rare-earth elements (SIMS method) in minerals from the rocks of the Khitoostrov occurrence (Belomorian mobile belt of Eastern Fennoscandia) was studied: corundum-bearing metasomatites with anomalous isotopically light oxygen and hydrogen and garnet amphibolites after gabbro with normal isotopic composition. The study was accompanied by estimates of P-T parameters of rock formation using multi-equilibrium thermobarometry (TWEEQU method). Temperatures calculated for garnet amphibolites after gabbro fall within the range of 730–770 ° C, pressures - 13–14 kbar; for corundum-bearing rocks, temperatures were 680–710 ° C, pressures - 6.5–7.5 kbar. Corundum-bearing rocks were formed at slightly lower temperatures and at significantly lower pressures than garnet amphibolites after gabbro. The REE distribution spectra in garnets from apogabbroic amphibolites are characterized by a clearly pronounced slope from light to heavy REE, while in garnets from corundum-bearing rocks they have a less pronounced positive slope, which is associated with a noticeable enrichment of garnets in LREE and an insignificant depletion of HREE. Calcium amphiboles from corundum-bearing rocks are significantly enriched in rare-earth elements as compared to amphiboles from garnet amphibolites after gabbro, especially LREE (by more than an order of magnitude) and, to a lesser extent, MREE. Plagioclases from corundum-bearing rocks are also enriched in LREE against the background of garnet amphibolites. Thus, in all the studied minerals of corundum-bearing rocks LREE enrichment is recorded. It isn’t manifested in the minerals of amphibolites and, obviously, isn’t related to the difference in P-T parameters of rock formation. Consequently, LREE was transferred by a specific fluid during mineral-forming processes, which led to the formation of metasomatites with an anomalous isotopic composition of oxygen and hydrogen.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82299597","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 : 2021-01-01DOI: 10.21638/spbu07.2021.404
V. A. Krylova, G. Gutiérrez-Alonso, I. Gertner, T. S. Krasnova
The article presents the results of petrostructural and mineralogical studies of olivine grains from ultrabasic and basic rocks of different genesis. In particular, they correspond to cumulative dunites of the Yoko-Dovyren layered massif (Northern Cisbaikalia), restite hyperbasites of the Velvet massif (Kuznetskiy Alatau), and xenoliths of peridotites from basalts of the Canary Islands (Spain). The relationship between the petrostructural and mineralogical features of ultrabasic rocks is shown, which makes it possible to identify their cumulative and restite varieties. An important element of the petrostructure of ultrabasites is the orientation of olivine, which reflects either the conditions for the formation of primary crystals in the magmatic melt, or the conditions for its recrystallization as a result of plastic deformations during exhumation to the Earth's surface. The mineral composition of rocks is an additional feature that reflects the real conditions of formation. In the presence of basic plagioclase, it is already quite difficult to speak about the restitic nature of these ultrabasic rocks. On the other hand, plastic deformations of olivine are characteristic of restitic hyperbasites, in which plagioclase is absent. The results of mineralogical studies in ultrabasic xenoliths of the Canary Islands showed the presence of basic plagioclase (labradorite), as well as chrysolite-type olivine (12-16 Fa), which corresponds to the attributes of ultrabasic layered intrusions such as the Yoko-Dovyren dunite-troctolite-gabbro pluton. For restite hyperbasites (by the example of the Kuznetsk Alatau), the iron content of olivine does not exceed 9-10% of the fayalite end, while plagioclase and clinopyroxene are absent. A characteristic feature of the xenoliths of the Canary Islands is the presence of endiopside, which is present in layered intrusions, but is absent in the restrained fragments of the upper and lower mantle. It is assumed that the xenoliths in the basalts of the Canary Islands are not of a mantle nature, but are fragments of a deep magma chamber. The studies of the optical orientation of olivine in xenoliths of the rocks of Lanzarote Island confirm these conclusions. The geochemical parameters of ultramafic xenoliths on Tenerife Island may well correspond to deeper formations.
{"title":"Petrofabric and geochemical features of ultramafic rocks on the example of restite metamorphites of the Kuznetsk Alatau (Western Siberia), olivine cumulates of the Yoko-Dovyren layered massif (Northern Cisbaikalia) and their analogues from ultrabasic xenoliths of the Canary Islands (Spain)","authors":"V. A. Krylova, G. Gutiérrez-Alonso, I. Gertner, T. S. Krasnova","doi":"10.21638/spbu07.2021.404","DOIUrl":"https://doi.org/10.21638/spbu07.2021.404","url":null,"abstract":"The article presents the results of petrostructural and mineralogical studies of olivine grains from ultrabasic and basic rocks of different genesis. In particular, they correspond to cumulative dunites of the Yoko-Dovyren layered massif (Northern Cisbaikalia), restite hyperbasites of the Velvet massif (Kuznetskiy Alatau), and xenoliths of peridotites from basalts of the Canary Islands (Spain). The relationship between the petrostructural and mineralogical features of ultrabasic rocks is shown, which makes it possible to identify their cumulative and restite varieties. An important element of the petrostructure of ultrabasites is the orientation of olivine, which reflects either the conditions for the formation of primary crystals in the magmatic melt, or the conditions for its recrystallization as a result of plastic deformations during exhumation to the Earth's surface. The mineral composition of rocks is an additional feature that reflects the real conditions of formation. In the presence of basic plagioclase, it is already quite difficult to speak about the restitic nature of these ultrabasic rocks. On the other hand, plastic deformations of olivine are characteristic of restitic hyperbasites, in which plagioclase is absent. The results of mineralogical studies in ultrabasic xenoliths of the Canary Islands showed the presence of basic plagioclase (labradorite), as well as chrysolite-type olivine (12-16 Fa), which corresponds to the attributes of ultrabasic layered intrusions such as the Yoko-Dovyren dunite-troctolite-gabbro pluton. For restite hyperbasites (by the example of the Kuznetsk Alatau), the iron content of olivine does not exceed 9-10% of the fayalite end, while plagioclase and clinopyroxene are absent. A characteristic feature of the xenoliths of the Canary Islands is the presence of endiopside, which is present in layered intrusions, but is absent in the restrained fragments of the upper and lower mantle. It is assumed that the xenoliths in the basalts of the Canary Islands are not of a mantle nature, but are fragments of a deep magma chamber. The studies of the optical orientation of olivine in xenoliths of the rocks of Lanzarote Island confirm these conclusions. The geochemical parameters of ultramafic xenoliths on Tenerife Island may well correspond to deeper formations.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88630561","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 : 2020-10-12DOI: 10.21638/spbu07.2020.409
E. S. Przhiyalgovskii, Y. Morozov, M. G. Leonov, A. K. Rybin, E. V. Lavrushina
The article presents data on the structure of transition zones from areas of relative downwarping (intramountain depressions) to anticlinor uplifts dividing them. The geological and geophysical data obtained by the authors in recent years in different areas of the Northern Tien Shan are considering and discussing to compare the structure and tectonic evolution of key objects. A comparative analysis of the depression / uplift tectonic zones in different regions indicates a fundamental similarity in their structure. These areas of gradient vertical movements are zones of concentrated deformation. We described ensembles of structures formed at the same time in the sedimentary cover and in the basement rocks. Similar structural features are due to the common tectonic evolution of basins and ridges as parts of a unified activation structure of the Paleozoic folded belt. Over a long period of time, from the Oligocene to the Pliocene inclusive, the depressions of the Northern Tien Shan had developed under conditions of sedimentary subsidence, probably by the type of pool-apart structures in a latitudinally oriented region of plastic shear deformation. The relatively quiet tectonic setting of this stage is reflected in the lithological features of the sedimentary complexes. The next stage, which began about 3 Ma b.p., was marked not only by the emergence of a high-altitude relief and the accumulation of molasses, but also by a change of tectonic regime to transpression. The generally flexible bending of the foundation surface in the steep sides of the depressions, to some extent complicated by uplifts, was accompanied by the formation of extensive detachments and thrust-folded structural ensembles in the sedimentary cover of the depressions. Contrary to popular point of view volumes of disintegrated basement rocks demonstrate significant plasticity. The lateral pressure of the side ledges inside the sedimentary cover was transmitted for many kilometers towards the depression’s center. At the same time, contrary to traditional ideas, the volumes of disintegrated rocks of the basement demonstrate significant plasticity, while the lateral pressure of the side ledges was transmitted for many kilometers into the depressions inside the sedimentary cover.
{"title":"Tectonic structure and development of the “depression/ uplift” transition zones, Northern Tien Shan","authors":"E. S. Przhiyalgovskii, Y. Morozov, M. G. Leonov, A. K. Rybin, E. V. Lavrushina","doi":"10.21638/spbu07.2020.409","DOIUrl":"https://doi.org/10.21638/spbu07.2020.409","url":null,"abstract":"The article presents data on the structure of transition zones from areas of relative downwarping (intramountain depressions) to anticlinor uplifts dividing them. The geological and geophysical data obtained by the authors in recent years in different areas of the Northern Tien Shan are considering and discussing to compare the structure and tectonic evolution of key objects. A comparative analysis of the depression / uplift tectonic zones in different regions indicates a fundamental similarity in their structure. These areas of gradient vertical movements are zones of concentrated deformation. We described ensembles of structures formed at the same time in the sedimentary cover and in the basement rocks. Similar structural features are due to the common tectonic evolution of basins and ridges as parts of a unified activation structure of the Paleozoic folded belt. Over a long period of time, from the Oligocene to the Pliocene inclusive, the depressions of the Northern Tien Shan had developed under conditions of sedimentary subsidence, probably by the type of pool-apart structures in a latitudinally oriented region of plastic shear deformation. The relatively quiet tectonic setting of this stage is reflected in the lithological features of the sedimentary complexes. The next stage, which began about 3 Ma b.p., was marked not only by the emergence of a high-altitude relief and the accumulation of molasses, but also by a change of tectonic regime to transpression. The generally flexible bending of the foundation surface in the steep sides of the depressions, to some extent complicated by uplifts, was accompanied by the formation of extensive detachments and thrust-folded structural ensembles in the sedimentary cover of the depressions. Contrary to popular point of view volumes of disintegrated basement rocks demonstrate significant plasticity. The lateral pressure of the side ledges inside the sedimentary cover was transmitted for many kilometers towards the depression’s center. At the same time, contrary to traditional ideas, the volumes of disintegrated rocks of the basement demonstrate significant plasticity, while the lateral pressure of the side ledges was transmitted for many kilometers into the depressions inside the sedimentary cover.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75797240","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 : 2020-09-30DOI: 10.21638/spbu07.2020.404
Yu. V. Simonova, A. Rusakov, E. Korkina
Humid conditions do not encourage the formation of salt-affected soils enhancing leaching salts out of soil profiles. Nevertheless, the occurrence of salt-affected soils under humid climate is evident as a result from another factors but not the climatic one. Soil salinity in these landscapes is caused by anthropogenic salinization. The objective of this study was to identify types of chemical composition and salinity level of soils forming within the impact zone of artesian water discharge. This paper also provides determining the degree of contrast to adjacent non-saline soils and salt contamination boundaries. Soil and water samples were collected from three sites located in the Yaroslavl’ region, the Upper Volga. Sampling was released in June 2017. In the Upper Volga region high-mineralized water rises from saline aquifers via abandoned exploration wells drilled in the 1960s. These soils are found under an average annual rainfall of about 500-700 mm in taiga zone. This type of climate and vegetation cover normally should lead to the formation of Albic Retisols. Saline waters affecting soils are dominantly Na-Cl or Ca-Na-Cl-SO4 brines. Total dissolved solids in the saline waters range from 10000 to 259500 mg·L-1. Salt-affected soils have from low to high salinity (0,1-0,8%) but salt content does not exceed 1%. In the study areas maximum of salinity in the soils investigated was fixed near the water table or was associated with lithic discontinuity or abrupt textural change. Salt leaching from the upper horizons prevails in the course of annual cycle and that is what differs them from hydromorphic saline soils formed in arid climate. Field electrical surveys of salinity indicated the local zones of salinization. The salinization phenomenon in humid climate is not of the main pedogenic processes but the additional process. The upper horizons of salt-affected soils tend to have similar morphological features to zonal and intrazonal soils. The salt-affected soils studied were classified according to WRB as Orthofluvic Fluvisol (Humic, Loamic, Endosalic, Technic), Orthofluvic Gleyic Fluvisol (Humic, Siltic, Endosalic, Raptic), Amphistagnic Albic Retisol (Siltic, Anoaric, Cutanic, Endosalic), Albic Retisol (Siltic, Anoaric, Cutanic, Endosalic, Raptic).
{"title":"Soil salinization processes in the impact zone of mineralized water discharge by the case study in the Yaroslavl Volga region, Russia","authors":"Yu. V. Simonova, A. Rusakov, E. Korkina","doi":"10.21638/spbu07.2020.404","DOIUrl":"https://doi.org/10.21638/spbu07.2020.404","url":null,"abstract":"Humid conditions do not encourage the formation of salt-affected soils enhancing leaching salts out of soil profiles. Nevertheless, the occurrence of salt-affected soils under humid climate is evident as a result from another factors but not the climatic one. Soil salinity in these landscapes is caused by anthropogenic salinization. The objective of this study was to identify types of chemical composition and salinity level of soils forming within the impact zone of artesian water discharge. This paper also provides determining the degree of contrast to adjacent non-saline soils and salt contamination boundaries. Soil and water samples were collected from three sites located in the Yaroslavl’ region, the Upper Volga. Sampling was released in June 2017. In the Upper Volga region high-mineralized water rises from saline aquifers via abandoned exploration wells drilled in the 1960s. These soils are found under an average annual rainfall of about 500-700 mm in taiga zone. This type of climate and vegetation cover normally should lead to the formation of Albic Retisols. Saline waters affecting soils are dominantly Na-Cl or Ca-Na-Cl-SO4 brines. Total dissolved solids in the saline waters range from 10000 to 259500 mg·L-1. Salt-affected soils have from low to high salinity (0,1-0,8%) but salt content does not exceed 1%. In the study areas maximum of salinity in the soils investigated was fixed near the water table or was associated with lithic discontinuity or abrupt textural change. Salt leaching from the upper horizons prevails in the course of annual cycle and that is what differs them from hydromorphic saline soils formed in arid climate. Field electrical surveys of salinity indicated the local zones of salinization. The salinization phenomenon in humid climate is not of the main pedogenic processes but the additional process. The upper horizons of salt-affected soils tend to have similar morphological features to zonal and intrazonal soils. The salt-affected soils studied were classified according to WRB as Orthofluvic Fluvisol (Humic, Loamic, Endosalic, Technic), Orthofluvic Gleyic Fluvisol (Humic, Siltic, Endosalic, Raptic), Amphistagnic Albic Retisol (Siltic, Anoaric, Cutanic, Endosalic), Albic Retisol (Siltic, Anoaric, Cutanic, Endosalic, Raptic).","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2020-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78461449","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 : 2020-08-26DOI: 10.21638/spbu07.2020.310
V. Podkovyrov, L. N. Kotova
A lithochemical and chemostratigraphic study of the boundary Upper Vendian–Lower Cambrian deposits of the Baltic monocline in the well sections of Leningrad Oblast and northeastern Estonia was carried out in the volume of the Redkino, Kotlin and Lontova horizons. Both common features and differences in the rock associations of individual horizons in different wells are revealed, which is a consequence of local variations of sedimentation conditions. The deposits of the Redkino horizon uncovered in the central and eastern parts of the region are characterized by a similar composition of rocks, represented by moderately deep-water sandy-clayey sediments of small thickness, formed in disoxidic and anoxic environments with pronounced processes of bacterial sulfate reduction. The deposits of the Kotlin horizon are represented by two groups of rocks. In the sections of wells in the east and west of Leningrad Oblast, a variety of sandy-siltstone rocks, representing coastalmarine sediments of oxidative conditions in the basin, predominate. In sections of the central part of the Baltic monocline (district of St. Petersburg), fine-grained deep-water disoxic and ferrigenous anoxic environments with a marked accumulation of siderite are common. Marine sandy-clay deposits of the Lontova horizon of the Lower Cambrian have similar lithochemical characteristics with the Kotlin deposits of the “eastern” and “western” sections of the territory, but they were formed under conditions of some oxygen deficiency (disoxic facies). Petrochemical analysis of core material showed that all the sediments studied belong to lithogenic sediments in which no presence of volcanic or pyrogenic material is observed. The formation of the sedimentary sequence of the Upper Vendian–Lower Cambrian of the Baltic monocline took place under the conditions of a passive continental regime with a gradual change of humid climatic conditions with semiarid ones.
{"title":"Lithogeochemistry and depositional environments of sedimentary rocks of the upper Vendian and lower Cambrian of the North-West Baltic monocline","authors":"V. Podkovyrov, L. N. Kotova","doi":"10.21638/spbu07.2020.310","DOIUrl":"https://doi.org/10.21638/spbu07.2020.310","url":null,"abstract":"A lithochemical and chemostratigraphic study of the boundary Upper Vendian–Lower Cambrian deposits of the Baltic monocline in the well sections of Leningrad Oblast and northeastern Estonia was carried out in the volume of the Redkino, Kotlin and Lontova horizons. Both common features and differences in the rock associations of individual horizons in different wells are revealed, which is a consequence of local variations of sedimentation conditions. The deposits of the Redkino horizon uncovered in the central and eastern parts of the region are characterized by a similar composition of rocks, represented by moderately deep-water sandy-clayey sediments of small thickness, formed in disoxidic and anoxic environments with pronounced processes of bacterial sulfate reduction. The deposits of the Kotlin horizon are represented by two groups of rocks. In the sections of wells in the east and west of Leningrad Oblast, a variety of sandy-siltstone rocks, representing coastalmarine sediments of oxidative conditions in the basin, predominate. In sections of the central part of the Baltic monocline (district of St. Petersburg), fine-grained deep-water disoxic and ferrigenous anoxic environments with a marked accumulation of siderite are common. Marine sandy-clay deposits of the Lontova horizon of the Lower Cambrian have similar lithochemical characteristics with the Kotlin deposits of the “eastern” and “western” sections of the territory, but they were formed under conditions of some oxygen deficiency (disoxic facies). Petrochemical analysis of core material showed that all the sediments studied belong to lithogenic sediments in which no presence of volcanic or pyrogenic material is observed. The formation of the sedimentary sequence of the Upper Vendian–Lower Cambrian of the Baltic monocline took place under the conditions of a passive continental regime with a gradual change of humid climatic conditions with semiarid ones.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2020-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73229590","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 : 2020-01-01DOI: 10.21638/spbu07.2020.403
P. Golubkin, Julia Smirnova, Vsevolod S. Kolyada
In this study possible changes in sea surface temperature (SST) caused by passage of polar lows and analyzed. Polar lows are extreme atmospheric phenomena inherent to high latitudes. They develop sea surface wind speeds from 15 m/s up to hurricane force values and are characterized by small sizes (on average, 300 km) and lifetimes (less than two days), which complicates their detection and studies. It is assumed that as in case of tropical cyclones, which may considerably lower SST due to intense mixing and entrainment of colder waters to the ocean upper mixed layer, polar lows could similarly influence SST. Moreover, in the high latitude areas, where salt stratification may be present instead of temperature stratification, SST may increase due to mixing with deeper warmer layer. In this study 330 polar lows were analyzed using satellite passive microwave radiometer measurements of SST. In result, 47 cases when average SST values changed in polar low forcing areas were found. Out of these cases, in six cases SST increase of at least 0.5 °С was found, and in fifteen cases SST decrease of at least 0.5 °С was found. This indicates that upper ocean response to polar lows is quite rare phenomenon, which should be further analyzed along with its possible role in the ocean-ice-atmosphere system.
{"title":"Sea surface temperature changes due to polar lows over the Nordic Seas","authors":"P. Golubkin, Julia Smirnova, Vsevolod S. Kolyada","doi":"10.21638/spbu07.2020.403","DOIUrl":"https://doi.org/10.21638/spbu07.2020.403","url":null,"abstract":"In this study possible changes in sea surface temperature (SST) caused by passage of polar lows and analyzed. Polar lows are extreme atmospheric phenomena inherent to high latitudes. They develop sea surface wind speeds from 15 m/s up to hurricane force values and are characterized by small sizes (on average, 300 km) and lifetimes (less than two days), which complicates their detection and studies. It is assumed that as in case of tropical cyclones, which may considerably lower SST due to intense mixing and entrainment of colder waters to the ocean upper mixed layer, polar lows could similarly influence SST. Moreover, in the high latitude areas, where salt stratification may be present instead of temperature stratification, SST may increase due to mixing with deeper warmer layer. In this study 330 polar lows were analyzed using satellite passive microwave radiometer measurements of SST. In result, 47 cases when average SST values changed in polar low forcing areas were found. Out of these cases, in six cases SST increase of at least 0.5 °С was found, and in fifteen cases SST decrease of at least 0.5 °С was found. This indicates that upper ocean response to polar lows is quite rare phenomenon, which should be further analyzed along with its possible role in the ocean-ice-atmosphere system.","PeriodicalId":41676,"journal":{"name":"Vestnik of Saint Petersburg University Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83258950","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：