Pub Date : 2024-07-01DOI: 10.1134/s1028334x24602451
P. D. Kotler, S. V. Khromykh, K. E. Degtyarev, A. V. Kulikova, M. D. Tsareva, V. A. Penkina
Abstract
For the northeastern part of the Chingiz–Tarbagatai segment of the Boshchekul–Chingiz folded area, U‒Pb age estimates of Middle Paleozoic granitoid complexes were obtained for the first time and their geochemical features were described. The recent data indicate a wide distribution of Late Silurian granitoids, represented by I-type rocks, on this territory. Early Devonian rocks form a number of separate volcano-plutonic structures, the granitoids of which can be classified as A-type. The compositional features of granitoids formed during the Cambrian‒Devonian enable one to trace the evolution of the crust of this part of the Chingiz–Tarbagatai segment from an ensimatic island arc to a volcanic belt with a relatively mature continental-type crust.
摘要 在 Boshchekul-Chingiz 褶皱区的 Chingiz-Tarbagatai 段东北部，首次获得了中古生代花岗岩复合体的 U-Pb 年龄估计值，并描述了其地球化学特征。最新数据表明，以 I 型岩石为代表的晚志留纪花岗岩在该地区分布广泛。早泥盆世岩石形成了许多独立的火山-岩浆构造，其中的花岗岩可归类为 A 型。根据寒武纪-泥盆纪期间形成的花岗岩的成分特征，我们可以追溯出 Chingiz-Tarbagatai 地段这一部分的地壳演变过程，即从一个岛弧演变成一个具有相对成熟的大陆型地壳的火山带。
{"title":"Stages of Granitoid Magmatism in the Eastern Part of the Kazakhstan Composite Continent in the Early–Middle Paleozoic","authors":"P. D. Kotler, S. V. Khromykh, K. E. Degtyarev, A. V. Kulikova, M. D. Tsareva, V. A. Penkina","doi":"10.1134/s1028334x24602451","DOIUrl":"https://doi.org/10.1134/s1028334x24602451","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>For the northeastern part of the Chingiz–Tarbagatai segment of the Boshchekul–Chingiz folded area, U‒Pb age estimates of Middle Paleozoic granitoid complexes were obtained for the first time and their geochemical features were described. The recent data indicate a wide distribution of Late Silurian granitoids, represented by I-type rocks, on this territory. Early Devonian rocks form a number of separate volcano-plutonic structures, the granitoids of which can be classified as A-type. The compositional features of granitoids formed during the Cambrian‒Devonian enable one to trace the evolution of the crust of this part of the Chingiz–Tarbagatai segment from an ensimatic island arc to a volcanic belt with a relatively mature continental-type crust.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141524895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-01DOI: 10.1134/s1028334x24602621
S. G. Kovalev, S. S. Kovalev, A. A. Sharipova, V. M. Gorozhanin, A. V. Maslov
Abstract
This work presents new data on the Sm–Nd age of the Ishlya (1470 ± 62 Ma) and Misaelga (1481 ± 58 Ma) mafic/ultramafic complexes distributed along the western slope of the Southern Urals. The ages obtained are close to the Calymmian–Ectasian boundary (~1400 Ma) of the International Chronostratigraphic Scale. Based on calculated data, it is shown that the area of magma generation for the melts that formed the named complexes has been located in the “head” of a plume, which is the primary cause of the Mashak “magmatic event” in the Southern Urals.
{"title":"New Data on the Sm–Nd Age of Mafic/Ultramafic Intrusions on the Western Slope of the Southern Urals","authors":"S. G. Kovalev, S. S. Kovalev, A. A. Sharipova, V. M. Gorozhanin, A. V. Maslov","doi":"10.1134/s1028334x24602621","DOIUrl":"https://doi.org/10.1134/s1028334x24602621","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>This work presents new data on the Sm–Nd age of the Ishlya (1470 ± 62 Ma) and Misaelga (1481 ± 58 Ma) mafic/ultramafic complexes distributed along the western slope of the Southern Urals. The ages obtained are close to the Calymmian–Ectasian boundary (~1400 Ma) of the International Chronostratigraphic Scale. Based on calculated data, it is shown that the area of magma generation for the melts that formed the named complexes has been located in the “head” of a plume, which is the primary cause of the Mashak “magmatic event” in the Southern Urals.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141524896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-01DOI: 10.1134/s1028334x24602578
M. V. Slukovskaya, A. G. Petrova, L. A. Ivanova, I. A. Mosendz, T. K. Ivanova, S. V. Drogobuzhskaya, A. I. Novikov, A. A. Shirokaya, I. P. Kremenetskaya
Abstract
Factors influencing the geochemical migration of elements during the development of artificial phytocenoses on industrially polluted peat soil with a high level of copper and nickel content using serpentine-containing materials are considered. Monitoring of the remediation sites during a four-year field experiment showed that the grass cover is capable of sustainable functioning by neutralizing the acidity of peat soil, reducing the toxicity of soil solutions, and eliminating the imbalance of macronutrients. Serpentine minerals act as an alkaline barrier, reducing the intensity of migration of copper and nickel compounds.
{"title":"Geochemical Aspects of the Technology for Restoration of Vegetation Cover on Industrially Polluted Peat Soil Using Serpentine Materials","authors":"M. V. Slukovskaya, A. G. Petrova, L. A. Ivanova, I. A. Mosendz, T. K. Ivanova, S. V. Drogobuzhskaya, A. I. Novikov, A. A. Shirokaya, I. P. Kremenetskaya","doi":"10.1134/s1028334x24602578","DOIUrl":"https://doi.org/10.1134/s1028334x24602578","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Factors influencing the geochemical migration of elements during the development of artificial phytocenoses on industrially polluted peat soil with a high level of copper and nickel content using serpentine-containing materials are considered. Monitoring of the remediation sites during a four-year field experiment showed that the grass cover is capable of sustainable functioning by neutralizing the acidity of peat soil, reducing the toxicity of soil solutions, and eliminating the imbalance of macronutrients. Serpentine minerals act as an alkaline barrier, reducing the intensity of migration of copper and nickel compounds.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141524890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-01DOI: 10.1134/s1028334x24602797
G. K. Korotaev, V. N. Belokopytov, V. L. Dorofeev, A. I. Mizyuk, A. L. Kholod
Abstract
The thermohaline regime trends of the Black Sea basin in the period 2000–2021 were studied based on the data from three retrospective analyses (reanalyses) of the hydrophysical fields of the Black Sea. It is shown that the cumulative effect of an increase in the average sea surface temperature (SST) and increasingly milder winter conditions in the Black Sea over the last seven to eight years led to a record-breaking warming and then to the disappearance of the ventilated cold intermediate layer (CIL) of the Black Sea in its traditional meaning by 2020. In addition, in the past seven to eight years, accelerated warming of seawaters has been observed within the permanent (main) pycnocline. Changes in the thermal regime of the upper layer of the sea are accompanied by a continuing increase in salinity in the main pycnocline.
{"title":"Acceleration of Climate Change in the Upper Layer of the Black Sea","authors":"G. K. Korotaev, V. N. Belokopytov, V. L. Dorofeev, A. I. Mizyuk, A. L. Kholod","doi":"10.1134/s1028334x24602797","DOIUrl":"https://doi.org/10.1134/s1028334x24602797","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The thermohaline regime trends of the Black Sea basin in the period 2000–2021 were studied based on the data from three retrospective analyses (reanalyses) of the hydrophysical fields of the Black Sea. It is shown that the cumulative effect of an increase in the average sea surface temperature (SST) and increasingly milder winter conditions in the Black Sea over the last seven to eight years led to a record-breaking warming and then to the disappearance of the ventilated cold intermediate layer (CIL) of the Black Sea in its traditional meaning by 2020. In addition, in the past seven to eight years, accelerated warming of seawaters has been observed within the permanent (main) pycnocline. Changes in the thermal regime of the upper layer of the sea are accompanied by a continuing increase in salinity in the main pycnocline.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141524894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-01DOI: 10.1134/s1028334x24602682
A. A. Mezhueva, O. V. Karimova, L. A. Ivanova, N. D. Tolstykh, A. A. Zolotarev, N. N. Eremin
Abstract
A mineral with the composition Pd(Bi0.53Sb0.47), intermediate between sobolevskite, ideally PdBi, and sudburyite, PdSb, from the Chineiskii Deposit (Transbaikal region, Russia), was studied by the SEM and XRD methods. Its crystal structure was solved and refined (R = 3.02%) based on single crystal X-ray diffraction data. The structure is orthorhombic, and the space group is Cmcm. The unit-cell parameters are a = 4.1465(4) Å, b = 7.1782(6) Å, c = 5.6843(4) Å, V = 169.19(2) Å3, Z = 2. The series of the structures β-PdBi–Pd(Bi0.53Sb0.47)–PdSb and sobolevskite–sudburyite are discussed.
摘要 利用扫描电镜和 X 射线衍射方法研究了一种矿物，其成分为 Pd(Bi0.53Sb0.47)，介于索波列夫斯基（理想状态为 PdBi）和苏德伯里特（PdSb）之间，产自 Chineiskii 矿藏（俄罗斯外贝加尔地区）。根据单晶 X 射线衍射数据，解决并完善了其晶体结构（R = 3.02%）。晶体结构为正方晶系，空间群为 Cmcm。单位晶胞参数为 a = 4.1465(4) Å, b = 7.1782(6) Å, c = 5.6843(4) Å, V = 169.19(2) Å3, Z = 2。讨论了β-PdBi-Pd(Bi0.53Sb0.47)-PdSb 和 sobolevskite-sudburyite 结构系列。
{"title":"The Crystal Structure of a Mineral with the Composition Pd(Bi,Sb)","authors":"A. A. Mezhueva, O. V. Karimova, L. A. Ivanova, N. D. Tolstykh, A. A. Zolotarev, N. N. Eremin","doi":"10.1134/s1028334x24602682","DOIUrl":"https://doi.org/10.1134/s1028334x24602682","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>A mineral with the composition Pd(Bi<sub>0.53</sub>Sb<sub>0.47</sub>), intermediate between sobolevskite, ideally PdBi, and sudburyite, PdSb, from the Chineiskii Deposit (Transbaikal region, Russia), was studied by the SEM and XRD methods. Its crystal structure was solved and refined (<i>R</i> = 3.02%) based on single crystal X-ray diffraction data. The structure is orthorhombic, and the space group is <i>Cmcm</i>. The unit-cell parameters are <i>a =</i> 4.1465(4) Å, <i>b =</i> 7.1782(6) Å, <i>c =</i> 5.6843(4) Å, <i>V</i> = 169.19(2) Å<sup>3</sup>, <i>Z</i> = 2. The series of the structures β-PdBi–Pd(Bi<sub>0.53</sub>Sb<sub>0.47</sub>)–PdSb and sobolevskite–sudburyite are discussed.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141531939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-20DOI: 10.1134/s1028334x24602566
I. S. Volkov, E. O. Dubinina, S. A. Kossova, Y. N. Chizhova, Y. O. Larionova, V. M. Kozlovskii, A. N. Pertsev
Abstract
On the White Sea islands and coast of North Karelia, in the Chupa sector of the Belomorian mobile belt (BMB), carbonate–silicate and quartz veins are localized in bodies of Early Proterozoic metabasites and their contacts with host gneisses. The isotopic characteristics of coarse crystal vein carbonates (δ18O and δ13C), as well as associated quartz (δ18O) and biotite (δ18O and δD), were studied. The isotopic composition of oxygen suggests biotite–quartz–carbonate equilibria during the formation of veins at temperatures of 520–450°C. The O and H isotopic characteristics of biotite correspond to the equilibrium of the fluid with metamorphic rocks. At the same time, the isotopic compositions of O and C carbonates indicate different CO2 sources in fluids. There are three groups of carbonates according to δ18О and δ13С. The first group shows “magmatic” isotopic characteristics of the CO2 source (δ18ОVSMOW = 7.1…12.1‰; δ13СVPDB = –6.3…–4.5‰). Carbonates of the second group have high δ18О and δ13С, characteristic of Precambrian sedimentary carbonates (δ18ОVSMOW = 21.9…24.7‰; δ13СVPDB = –2.2…–2‰), similar to those described earlier in the neighboring Engozero sector of the BMB. In the third group, the δ13С values are similar to the carbonates of the first group, and δ18О, to the second group (δ13СVPDB = –1.7…0.9‰, δ18ОVSMOW = 6…12‰). The O and C isotopic compositions of carbonates of the third group can be obtained from the action of a putative magmatic fluid on both the primary sedimentary source of metamorphic fluids and redeposited vein carbonates.
摘要 在白海岛屿和北卡累利阿海岸的贝洛莫利亚移动带（BMB）丘帕区，碳酸盐-硅酸盐和石英脉分布在早新生代偏闪长岩体及其与主片麻岩的接触面上。研究了粗晶矿脉碳酸盐（δ18O 和 δ13C）以及相关石英（δ18O）和斜长石（δ18O 和 δD）的同位素特征。氧的同位素组成表明，在温度为 520-450°C 的矿脉形成过程中，生物岩-石英-碳酸盐达到了平衡。生物岩的 O 和 H 同位素特征与流体与变质岩的平衡相符。同时，O 和 C 碳酸盐的同位素组成表明流体中有不同的 CO2 来源。根据δ18О和δ13С，碳酸盐可分为三组。第一组显示出二氧化碳源的 "岩浆 "同位素特征（δ18ОVSMOW = 7.1...12.1‰；δ13СVPDB = -6.3...-4.5‰）。第二组碳酸盐岩的δ18О和δ13С含量较高，具有前寒武纪沉积碳酸盐岩的特征（δ18ОVSMOW = 21.9...24.7‰；δ13СVPDB = -2.2...-2‰），类似于早先在邻近的 BMB Engozero 地区描述的碳酸盐岩。第三组的δ13С值与第一组的碳酸盐岩相似，δ18О值与第二组相似（δ13СVPDB = -1.7...0.9‰, δ18ОVSMOW = 6...12‰）。第三组碳酸盐的 O 和 C 同位素组成可以通过推测的岩浆流体对变质流体原生沉积源和再沉积脉碳酸盐的作用获得。
{"title":"Isotope (δ18О, δ13С, δD) Characteristics of Biotite–Carbonate–Quartz Associations of Hydrothermal Veins in Metabasites of North Karelia","authors":"I. S. Volkov, E. O. Dubinina, S. A. Kossova, Y. N. Chizhova, Y. O. Larionova, V. M. Kozlovskii, A. N. Pertsev","doi":"10.1134/s1028334x24602566","DOIUrl":"https://doi.org/10.1134/s1028334x24602566","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>On the White Sea islands and coast of North Karelia, in the Chupa sector of the Belomorian mobile belt (BMB), carbonate–silicate and quartz veins are localized in bodies of Early Proterozoic metabasites and their contacts with host gneisses. The isotopic characteristics of coarse crystal vein carbonates (δ<sup>18</sup>O and δ<sup>13</sup>C), as well as associated quartz (δ<sup>18</sup>O) and biotite (δ<sup>18</sup>O and δD), were studied. The isotopic composition of oxygen suggests biotite–quartz–carbonate equilibria during the formation of veins at temperatures of 520–450°C. The O and H isotopic characteristics of biotite correspond to the equilibrium of the fluid with metamorphic rocks. At the same time, the isotopic compositions of O and C carbonates indicate different CO<sub>2</sub> sources in fluids. There are three groups of carbonates according to δ<sup>18</sup>О and δ<sup>13</sup>С. The first group shows “magmatic” isotopic characteristics of the CO<sub>2</sub> source (δ<sup>18</sup>О<sub>VSMOW</sub> = 7.1…12.1‰; δ<sup>13</sup>С<sub>VPDB</sub> = –6.3…–4.5‰). Carbonates of the second group have high δ<sup>18</sup>О and δ<sup>13</sup>С, characteristic of Precambrian sedimentary carbonates (δ<sup>18</sup>О<sub>VSMOW</sub> = 21.9…24.7‰; δ<sup>13</sup>С<sub>VPDB</sub> = –2.2…–2‰), similar to those described earlier in the neighboring Engozero sector of the BMB. In the third group, the δ<sup>13</sup>С values are similar to the carbonates of the first group, and δ<sup>18</sup>О, to the second group (δ<sup>13</sup>С<sub>VPDB</sub> = –1.7…0.9‰, δ<sup>18</sup>О<sub>VSMOW</sub> = 6…12‰). The O and C isotopic compositions of carbonates of the third group can be obtained from the action of a putative magmatic fluid on both the primary sedimentary source of metamorphic fluids and redeposited vein carbonates.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141524936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-20DOI: 10.1134/s1028334x24602372
V. N. Puchkov, Yu. L. Ronkin, N. D. Sergeeva
Abstract
The first results of 147Sm‒143Nd and Rb‒Sr ID-TIMS isotopic–geochronological results of a comparative study of 12 samples of volcanic rocks of the Bashkirian Meganticlinorium, which were previously dated by zircons from these samples using the U‒Pb SHRIMP-II method showing the predominance of the Paleozoic ages among three stratigraphic levels with Riphean magmatic events in the South Urals, are presented. New 147Sm‒143Nd and Rb‒Sr ID-TIMS isotopic data showed that the volcanic rocks evolved as a result of crustal–mantle interaction. The Nd model ages (TDM) (2302–2540 Ma) of volcanic rocks of the Taratash Anticlinorium represent the ages of the protolith characterized by εNd(t) values from –17.4 to –20.5. The TDM value (2033 Ma) of the Paleozoic volcanic rocks of the Yamantau Anticlinorium indicates a younger (Paleoproterozoic) substrate. The minimum Nd model ages (TDM = 1160–1233 Ma) are determined for the volcanic rocks, which are spatially related to metabasalts of the Igonin magmatic event (707‒732 Ma) in the Tirlyan Syncline. The smallest εNd(t) values (–3.2, –0.9, –0.7) indicating a decrease in the amount of a crustal component relative to the mantle material are determined for the Paleozoic metabasalts in the Tirlyan Syncline in the eastern wing of the Bashkirian Meganticlinorium, which is probably related to the activation of plume processes in the eastern part of the orogen. The Rb‒Sr and 147Sm‒143Nd ID-TIMS isotopic systematics of the studied volcanic rocks expands our understanding of mantle–crustal interactions within three stratigraphic levels with Riphean magmatic events of the South Urals.
{"title":"Basalts of the Riphean Sequences of the Bashkirian Meganticlinorium, South Urals: New 147Sm‒143Nd and Rb‒Sr ID-TIMS Isotopic Constraints","authors":"V. N. Puchkov, Yu. L. Ronkin, N. D. Sergeeva","doi":"10.1134/s1028334x24602372","DOIUrl":"https://doi.org/10.1134/s1028334x24602372","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The first results of <sup>147</sup>Sm‒<sup>143</sup>Nd and Rb‒Sr ID-TIMS isotopic–geochronological results of a comparative study of 12 samples of volcanic rocks of the Bashkirian Meganticlinorium, which were previously dated by zircons from these samples using the U‒Pb SHRIMP-II method showing the predominance of the Paleozoic ages among three stratigraphic levels with Riphean magmatic events in the South Urals, are presented. New <sup>147</sup>Sm‒<sup>143</sup>Nd and Rb‒Sr ID-TIMS isotopic data showed that the volcanic rocks evolved as a result of crustal–mantle interaction. The Nd model ages (<i>T</i><sub>DM</sub>) (2302–2540 Ma) of volcanic rocks of the Taratash Anticlinorium represent the ages of the protolith characterized by ε<sub>Nd</sub>(<i>t</i>) values from –17.4 to –20.5. The <i>T</i><sub>DM</sub> value (2033 Ma) of the Paleozoic volcanic rocks of the Yamantau Anticlinorium indicates a younger (Paleoproterozoic) substrate. The minimum Nd model ages (<i>T</i><sub>DM</sub> = 1160–1233 Ma) are determined for the volcanic rocks, which are spatially related to metabasalts of the Igonin magmatic event (707‒732 Ma) in the Tirlyan Syncline. The smallest ε<sub>Nd</sub>(<i>t</i>) values (–3.2, –0.9, –0.7) indicating a decrease in the amount of a crustal component relative to the mantle material are determined for the Paleozoic metabasalts in the Tirlyan Syncline in the eastern wing of the Bashkirian Meganticlinorium, which is probably related to the activation of plume processes in the eastern part of the orogen. The Rb‒Sr and <sup>147</sup>Sm‒<sup>143</sup>Nd ID-TIMS isotopic systematics of the studied volcanic rocks expands our understanding of mantle–crustal interactions within three stratigraphic levels with Riphean magmatic events of the South Urals.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141524940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-20DOI: 10.1134/s1028334x24602499
I. E. Stepanova, I. I. Kolotov
Abstract
The problem of interpreting heterogeneous and multiprecision geophysical data is considered from the point of view of combinatorics within the framework of the approximation approach. The discrete nature of information about physical fields and their sources imposes a number of limitations on the possibilities of adequate data interpretation. Combinatorial methods of discrete mathematics make it possible to describe accurately the criteria for selecting data to approximate the elements of anomalous potential fields, as well as for controlling the quality of the approximate solution of inverse problems, both linear and nonlinear.
{"title":"The Combinatorial–Variational Approach to Solving Linear and Nonlinear Inverse Problems in Geophysics","authors":"I. E. Stepanova, I. I. Kolotov","doi":"10.1134/s1028334x24602499","DOIUrl":"https://doi.org/10.1134/s1028334x24602499","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The problem of interpreting heterogeneous and multiprecision geophysical data is considered from the point of view of combinatorics within the framework of the approximation approach. The discrete nature of information about physical fields and their sources imposes a number of limitations on the possibilities of adequate data interpretation. Combinatorial methods of discrete mathematics make it possible to describe accurately the criteria for selecting data to approximate the elements of anomalous potential fields, as well as for controlling the quality of the approximate solution of inverse problems, both linear and nonlinear.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-20DOI: 10.1134/s1028334x2460230x
S. Yu. Sokolov, K. O. Dobroliubova, N. N. Turko, E. A. Moroz, A. S. Abramova, A. O. Mazarovich
Abstract
The morphology of the seafloor of the Madagascar Basin from Mauritius Island to the Southwest Indian Ridge (SWIR) is represented by a ridge-echeloned relief of the spreading basement. The azimuth of the relief differs by ~90° for the basin north of the SWIR and its wedge-shaped sublatitudinal rift system, separated by an abyssal escarpment. A genetic definition of this seafloor relief shape is given. This shape is formed when the ancient basement breaks up and accretion of the crust orthogonal to the azimuth, which existed before the rupture, begins. The formation of a wedge in the eastern part of the SWIR began about 41 Ma ago and is manifested by higher (±1100 m) amplitudes of relief variations than at the basement before the rupture (±250 m). The change in morphology is also associated with the change in the spreading azimuth of the lithospheric block by about 24° north of the SWIR, which opened up a new space for accretion. The morphology of the relief in the wedge and beyond shows the relationship of its parameters with slowdown in the spreading rate by almost three times when the kinematics of the plates have changed. The high-amplitude ridge-echeloned relief in the ultraslow segment of the SWIR with signs of nontransform displacement is combined with the maxima and minima of Bouguer anomalies. According to the published data, serpentized peridotites and basalts are obtained in the localization of the anomalies. These rocks indicate the presence of detachments with the exposure of ultramafic rocks and minimal magmatic output. Bouguer anomalies along the regional profile perfectly reflect deep density inhomogeneties. For intraplate volcanic edifices, they have a much greater deconsolidation in the upper mantle than near the active interplate boundary of the SWIR. According to the seismic tomography data, the absence of a deep upwelling under the newly formed SWIR segment and the presence of a “cold” gap in the “hot” lenses of the mantle indicates the action of tangential forces in the lithosphere that are not associated with general mantle convection. The formation of the new orthogonal rift system with ultraslow rates is an adaptation to variations in the kinematics parameters of the adjacent lithospheric plates.
{"title":"Geodynamic Settings of the Seafloor Relief Formation in the Madagascar Basin from Data of the 29th Cruise of R/V Akademik Nikolai Strakhov","authors":"S. Yu. Sokolov, K. O. Dobroliubova, N. N. Turko, E. A. Moroz, A. S. Abramova, A. O. Mazarovich","doi":"10.1134/s1028334x2460230x","DOIUrl":"https://doi.org/10.1134/s1028334x2460230x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The morphology of the seafloor of the Madagascar Basin from Mauritius Island to the Southwest Indian Ridge (SWIR) is represented by a ridge-echeloned relief of the spreading basement. The azimuth of the relief differs by ~90° for the basin north of the SWIR and its wedge-shaped sublatitudinal rift system, separated by an abyssal escarpment. A genetic definition of this seafloor relief shape is given. This shape is formed when the ancient basement breaks up and accretion of the crust orthogonal to the azimuth, which existed before the rupture, begins. The formation of a wedge in the eastern part of the SWIR began about 41 Ma ago and is manifested by higher (±1100 m) amplitudes of relief variations than at the basement before the rupture (±250 m). The change in morphology is also associated with the change in the spreading azimuth of the lithospheric block by about 24° north of the SWIR, which opened up a new space for accretion. The morphology of the relief in the wedge and beyond shows the relationship of its parameters with slowdown in the spreading rate by almost three times when the kinematics of the plates have changed. The high-amplitude ridge-echeloned relief in the ultraslow segment of the SWIR with signs of nontransform displacement is combined with the maxima and minima of Bouguer anomalies. According to the published data, serpentized peridotites and basalts are obtained in the localization of the anomalies. These rocks indicate the presence of detachments with the exposure of ultramafic rocks and minimal magmatic output. Bouguer anomalies along the regional profile perfectly reflect deep density inhomogeneties. For intraplate volcanic edifices, they have a much greater deconsolidation in the upper mantle than near the active interplate boundary of the SWIR. According to the seismic tomography data, the absence of a deep upwelling under the newly formed SWIR segment and the presence of a “cold” gap in the “hot” lenses of the mantle indicates the action of tangential forces in the lithosphere that are not associated with general mantle convection. The formation of the new orthogonal rift system with ultraslow rates is an adaptation to variations in the kinematics parameters of the adjacent lithospheric plates.</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-20DOI: 10.1134/s1028334x24602311
S. G. Soloviev, S. G. Kryazhev, D. V. Semenova, Ya. A. Kalinin, N. S. Bortnikov
Abstract
First data on the U–Pb isotopic (LA-ICP-MS) age of zircon from intrusive rocks of the Molo-Sarychat pluton, which is confined to a system of deep faults of the “V.A. Nikolaev line” in East Kyrgyzstan, are presented. The rocks of this pluton belong to high-K calc-alkaline and shoshonite series with spatially and genetically related intense Mo(‒W‒Cu‒Au) (mainly, porphyry Mo) mineralization. In addition to other Au, W, and Cu deposits and occurrences, this mineralization is part of an extended metallogenic belt of Tien Shan; however, the occurrences of porphyry Mo mineralization are few in number in this belt. The concordant U–Pb isotopic age of zircon autocrysts indicates the crystallization of quartz monzonites and monzogranites in the Early Permian: 293.3 ± 4.2 and 286.6 ± 2.4 Ma, respectively. The age of zircon antecrysts is 306‒320 Ma. The age of crystallization corresponds to the postcollision evolutionary stage of this territory, whereas the presence of antecrysts expands the period of the origination of the pluton in the Late Carboniferous–Early Permian, thus spanning the tectonic settings first of subduction and then of postcollision regimes. We therefore identified the postcollision nature of Mo(‒W‒Cu‒Au) (porphyry Mo) mineralization, which is related to the studied pluton and formed after the intrusion of quartz monzonites and monzonites (early and late-stage mineralization, respectively). A significant enrichment in Mo can be related to its progressive accumulation during magmatic differentiation, which led to the intrusion of quartz monzonites and, especially, monzogranites. These processes occurred under a more mature postcollision tectonic regime with the possible formation of intermediate magmatic sources in the Early Proterozoic substrate of metamorphic rocks and ancient granitoids. The age values of rocks of the Molo-Sarychat pluton are similar to those identified for metasomatic and igneous rocks of the large Kumtor Au deposit also confined to the “V.A. Nikolaev line.”
{"title":"Postcollision Porphyry Mo Mineralization of Central Tien Shan: First Data on U–Pb Isotopic (LA-ICP-MS) Dating of Zircon from Rocks of the Molo-Sarychat Productive Pluton, East Kazakhstan","authors":"S. G. Soloviev, S. G. Kryazhev, D. V. Semenova, Ya. A. Kalinin, N. S. Bortnikov","doi":"10.1134/s1028334x24602311","DOIUrl":"https://doi.org/10.1134/s1028334x24602311","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>First data on the U–Pb isotopic (LA-ICP-MS) age of zircon from intrusive rocks of the Molo-Sarychat pluton, which is confined to a system of deep faults of the “V.A. Nikolaev line” in East Kyrgyzstan, are presented. The rocks of this pluton belong to high-K calc-alkaline and shoshonite series with spatially and genetically related intense Mo(‒W‒Cu‒Au) (mainly, porphyry Mo) mineralization. In addition to other Au, W, and Cu deposits and occurrences, this mineralization is part of an extended metallogenic belt of Tien Shan; however, the occurrences of porphyry Mo mineralization are few in number in this belt. The concordant U–Pb isotopic age of zircon autocrysts indicates the crystallization of quartz monzonites and monzogranites in the Early Permian: 293.3 ± 4.2 and 286.6 ± 2.4 Ma, respectively. The age of zircon antecrysts is 306‒320 Ma. The age of crystallization corresponds to the postcollision evolutionary stage of this territory, whereas the presence of antecrysts expands the period of the origination of the pluton in the Late Carboniferous–Early Permian, thus spanning the tectonic settings first of subduction and then of postcollision regimes. We therefore identified the postcollision nature of Mo(‒W‒Cu‒Au) (porphyry Mo) mineralization, which is related to the studied pluton and formed after the intrusion of quartz monzonites and monzonites (early and late-stage mineralization, respectively). A significant enrichment in Mo can be related to its progressive accumulation during magmatic differentiation, which led to the intrusion of quartz monzonites and, especially, monzogranites. These processes occurred under a more mature postcollision tectonic regime with the possible formation of intermediate magmatic sources in the Early Proterozoic substrate of metamorphic rocks and ancient granitoids. The age values of rocks of the Molo-Sarychat pluton are similar to those identified for metasomatic and igneous rocks of the large Kumtor Au deposit also confined to the “V.A. Nikolaev line.”</p>","PeriodicalId":11352,"journal":{"name":"Doklady Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141507780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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