Petrology最新文献

{"title":"The Great Dyke of the Kola Peninsula as a Marker of an Archean Cratonization in the Northern Fennoscandian Shield","authors":"A. V. Stepanova,&nbsp;A. V. Samsonov,&nbsp;E. B. Salnikova,&nbsp;S. V. Egorova,&nbsp;Yu. O. Larionova,&nbsp;A. A. Arzamastsev,&nbsp;A. N. Larionov,&nbsp;M. A. Sukhanova,&nbsp;R. V. Veselovskiy","doi":"10.1134/S086959112206008X","DOIUrl":"10.1134/S086959112206008X","url":null,"abstract":"<div><p>The results of geochronological and petrological studies of the largest mafic dyke in the northern part of the Fennoscandian Shield, called the Great Dyke of the Kola Peninsula (GDK), are presented. According to U-Pb D-TIMS baddeleyite dating, the GDK crystallization age is 2680 ± 6 Ma. The age of host granites is 2.75–2.72 Ga (U-Pb, zircon, SHRIMP-II). The dyke has a simple internal structure with no signs of multistage melt injection. It comprises equigranular and plagioclase-porphyritic dolerites and gabbro that are amphibolitized to varying degrees. All rocks are low-Mg (Mg# less than 0.37) with low concentrations of Cr and Ni, and were derived through differentiation of more primitive melts. The analysis of geochemical and Sr-Nd isotopic data suggests that GDK melts could be formed by mixing of two types of mantle melts: depleted asthenospheric melt and enriched melt formed via melting of a lithospheric mantle. The weakly fractionated HREE patterns indicate that primary GDK melts originated at shallow (&lt;60 km) depths outside the garnet stability field. The generation and injection of melts of the Neoarchean GDK occurred immediately after large-scale granitic magmatism and main crustal growth event in the Murmansk Craton and marked the cratonization of the continental lithosphere in the northeastern part of the Fennoscandian Shield.</p></div>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4624539","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}

{"title":"А History of Coronitic Metagabbronorites in the Belomorian Province, Fennoscandian Shield: U-Pb (CA-ID-TIMS) Dating of Zircon–Baddeleyite Aggregates","authors":"E. B. Salnikova,&nbsp;A. V. Stepanova,&nbsp;P. Ya. Azimov,&nbsp;M. A. Sukhanova,&nbsp;A. B. Kotov,&nbsp;S. V. Egorova,&nbsp;Yu. V. Plotkina,&nbsp;E. V. Tolmacheva,&nbsp;A. V. Kervinen,&nbsp;N. V. Rodionov,&nbsp;V. S. Stepanov","doi":"10.1134/S0869591122060066","DOIUrl":"10.1134/S0869591122060066","url":null,"abstract":"<div><p>The estimation of crystallization and metamorphic reworking ages of mafic rocks in the polycyclic Precambrian areas is a difficult problem. Magmatic baddeleyite can be partially or completely replaced by polycrystalline zircon within a wide range of temperature and pressures, from greenschist to granulite facies. Evaluation of the age of each phase of the zircon–baddeleyite aggregates can provide information on both the age of the magmatic crystallization and metamorphism. U-Th-Pb (SHRIMP-II) and U-Pb (ID-TIMS) geochronological studies were carried out for single baddeleyite grains and zircon–baddeleyite aggregates from gabbronorites (“drusites”) of the Ambarnsky massif (Belomorian Province, Fennoscandian Shield). The petrological studies indicate the simultaneous growth of coronas at the olivine–plagioclase boundary and zircon rims around baddeleyite. U-Pb (ID-TIMS) dating of single baddeleyite grains yielded 2411 ± 6 Ma crystallization age of gabbronorites of the Ambarnsky massif. U-Pb (ID-TIMS) dating coupled with the discrete chemical abrasion give an age of 1911 ± 35 Ma for metamorphic zircon rims. The obtained results indicate that coronitic textures in the gabbronorites were formed 500 million years later than the magmatic crystallization of rocks as a result of the granulite-facies metamorphism that was probably related to the Lapland-Kola orogeny.</p></div>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4628653","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}

{"title":"Eocene Calc-Alkaline Volcanic Rocks from Central Iran (Southeast of Khur, Isfahan Province); an Evidence of Neotethys Syn-Subduction Magmatism","authors":"Paniz Shadman,&nbsp;Ghodrat Torabi,&nbsp;Tomoaki Morishita","doi":"10.1134/S0869591122060042","DOIUrl":"10.1134/S0869591122060042","url":null,"abstract":"<p>Eocene volcanic rocks with basaltic-trachyandesite and trachybasalt composition which cross-cut the Cretaceous sedimentary rocks, are exposed in the northwestern part of the Central-East Iranian Microcontient (CEIM) (SE of Khur, Isfahan Province, Iran). The rock-forming minerals of these volcanic rocks are olivine (chrysolite and hyalosiderite, Mg# = 0.69–0.71), clinopyroxene (augite with Mg# = 0.74–0.84), orthopyroxene (enstatite with Mg# = 0.61–0.62) and plagioclase (andesine and labradorite with <i>An</i>_48.3-65.1). Phenocrysts set in a fine-grained matrix of the same minerals plus sanidine (<i>Or</i>_59.1<i>Ab</i>_36.6<i>An</i>_4.3) with minor amounts of opaque minerals (magnetite and ilmenite). Secondary minerals are chlorite and calcite. The main textures of these volcanic rocks are porphyritic, microlitic porphyritic, poikilitic, and glomeroporphyritic. The Eocene volcanic rocks of the Khur area are characterized by SiO₂ content of 51.8 to 54.9 wt %, Al₂O₃ amounts of 14.35 to 16.47 wt %, and TiO₂ values of 0.88 to 0.92 wt %. They exhibit strong enrichment in light rare earth elements (LREE) relative to heavy REE (HREE) (La/Lu ratio up to 102.35), enrichment in large ion lithophile elements (LILEs), depletion in high field strength elements (HFSE), and present negative anomaly in Eu (Eu/Eu* = 0.72–0.87). Chemical characteristics and homogeneity of these volcanic rocks reveal their calc-alkaline nature and suggest that they were derived from a same parental magma and underwent a similar melt extraction. Major and trace elements geochemical features of the analyzed samples indicate that the parental magma was possibly derived from relatively low degrees of partial melting of a mantle wedge spinel lherzolite which was previously enriched by fluids/melts released from the Neo-Tethyan subducted slab.</p>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4627359","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}

{"title":"Comparative Characteristics of the Layering of Mafic–Ultramafic Intrusions of the Oulanka Group, Northern Karelia","authors":"A. R. Tskhovrebova,&nbsp;E. V. Koptev-Dvornikov,&nbsp;D. A. Bychkov","doi":"10.1134/S0869591122060091","DOIUrl":"10.1134/S0869591122060091","url":null,"abstract":"<p>The Oulanka group is a compact group of three peridotite–gabbronorite intrusions that is convenient for testing various petrogenetic concepts. The three intrusions are similar in age and occur not far from one another but differ in the composition of their original magmas, are characterized by different sets of cumulus mineral assemblages, and are different in inner structure and rhythmic layering. We applied cluster analysis of the contents of major elements to reproduce the cumulus mineral assemblages of the isochemically altered rocks of the Tsipringa and Lukkulaisvaara massifs. Although the parental magmas of the Kivakka and Tsipringa massifs were of different composition and their crystallization sequences were also different, the vertical sections of these massifs can be clearly subdivided into zones according to their cumulus mineral assemblages, with the limited development of rhythmic interbedding (with individual rhythms ranging from a few to a few dozen meters in thickness). Conversely, the Lukkulaisvaara intrusion does not possess any clearly distinguishable cumulus zones, and large-scale rhythmic layering is traceable throughout the entire thickness of the massif (with rhythms ranging from a few dozen to a few hundred meters in thickness). The different character of the rhythmic layering of the three intrusions may provide an insight into the different scenarios of magma convection in the chambers.</p>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4627358","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}

{"title":"The Effect of CO2 Reduction in Low-Water Melts at Low Hydrogen Fugacity: Experiment at 500 MPa and Thermodynamic Model","authors":"A. G. Simakin,&nbsp;V. N. Devyatova,&nbsp;G. V. Bondarenko","doi":"10.1134/S0869591122060078","DOIUrl":"10.1134/S0869591122060078","url":null,"abstract":"<div><p>Formation of graphite was observed in experiments on synthesis of dry carbon-bearing albite glasses in platinum capsules in an Internally Heated Pressure Vessel at 500 MPa and <i>Т</i> = 1200–1250°С. A thermodynamic model is proposed that explains the achievement of low oxygen fugacity near QFM-2 in the melt at low fugacity of hydrogen formed due to the decomposition of trace amounts of water in a compression medium (Ar gas). The unexpectedly low fugacity of oxygen is explained by the shift of equilibrium between the gases dissolved in the melt CO₂ + H₂ = H₂O + CO to the right due to the low activity of molecular water at a low total content of H₂O ~ 0.1–0.5 wt %. The high local СО concentrations in the melt lead to the platinum dissolution in form of carbonyl, corrosion of capsule walls, and redeposition of the metal at the contact with melt. With increase of water concentration in the melt (&gt;1 wt %), the effect of reduction disappears.</p></div>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4629163","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}

{"title":"Eastern Margin of the Neoarchean Tunguska Superterrane: Data from Boreholes in the Central Part of the Siberian Platform","authors":"A. V. Samsonov,&nbsp;K. G. Erofeeva,&nbsp;Yu. O. Larionova,&nbsp;A. N. Larionov,&nbsp;N. B. Kuznetsov,&nbsp;T. V. Romanyuk,&nbsp;N. V. Solovyova,&nbsp;O. M. Zhilicheva,&nbsp;A. S. Dubenskiy,&nbsp;V. S. Sheshukov","doi":"10.1134/S0869591122050058","DOIUrl":"10.1134/S0869591122050058","url":null,"abstract":"<p>The paper presents data on granites and gneisses recovered by Kulindinskaya-1 hole drilled in the central part of the Siberian Craton. The biotite granites retain a porphyritic texture, correspond to I-type according to their compositional features, are enriched in LREE and moderately depleted in HREE, and have negative Eu, Sr, and Nb and positive Zr anomalies. The U−Pb zircon age of the granites is Neoarchean (2525 ± 10 Ma), with single cores of zircon grains dated at about 2.6 Ga, which likely suggests a crustal source of the granitic magmas. The model age T_Nd(DM) = 2.77 Ga of the granite shows that the crust from which the initial melts were derived had been formed shortly before the melting episode. In terms of age and all characteristics, the granites are close to those of the Yurubchen massif, which was drilled through in the western part of the Tunguska superterrane. The biotite gneiss was apparently derived from sedimentary rocks and was heavily reworked when the granites were emplaced. The enrichment of the gneiss in Cr and Ni is probably inherited from the sedimentary protolith, whereas the REE, HFSE, and LILE concentrations and distribution in the gneiss are similar to those of the granite. The concordant (<i>D</i> &lt; 1%) U−Pb zircon ages (according to LA-ICP-MS data) broadly vary from 3284 to 2620 Ma, with two major peaks at 2717 and 2678 Ma. The model age of the gneiss T_Nd(DM) = 2.91 Ga confirms a contribution of the ancient crustal component to the sedimentary protolith of the rock. The minimum age of the detrital zircon, 2.62 Ga, determines the maximum age limit for sedimentation, and the minimum age limit is set by the age of the granite intrusions at 2.53 Ga. According to our data, the Archean gneisses and granites recovered by the Kulindinskaya-1 drillhole probably compose the eastern part of the Neoarchean Tunguska superterrane. Ereminskaya-101 drillhole, which was drilled 20 km northeast of Kulindinskaya-1, recovered gneisses with model ages T_Nd(DM) from 2.30 to 2.37 Ga, which belong to the adjacent Taimyr−Baikal suture zone with widespread Paleoproterozoic rocks. The contrasting crustal history of the adjacent complexes provides grounds to suggest that they were tectonically combined, which is an additional reason to consider the Taimyr−Baikal suture zone as a Paleoproterozoic collisional orogen.</p>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0869591122050058.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4624540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tantalite Solubility in Granitoid Melts and Evaluation of the Ta and Nb Diffusion Coefficients","authors":"V. Yu. Chevychelov","doi":"10.1134/S0869591122060030","DOIUrl":"10.1134/S0869591122060030","url":null,"abstract":"<p>The paper presents experimental data on tantalite solubility in water-saturated granitoid melts with various alumina and alkaline elements concentrations at <i>T</i> = 650–850°C and <i>P</i> = 100 MPa. The maximum Ta concentration (effective solubility) in melt is shown to be always higher than the Nb concentration. As the melt composition is changed from alkaline to Al₂O₃-enriched, the Ta and Nb concentrations decrease by one to two orders of magnitude, and the Nb/Ta ratio simultaneously decreases (from ~0.8–0.7 to ~0.4–0.1) because the Nb concentration decreases notably more rapidly than that of Ta. This effect is enhanced at decreasing temperature. The effective Ta solubility in melt is demonstrated to be practically independent of the composition of the dissolving mineral of the columbite-tantalite series. The Ta, Nb, Mn, and Fe diffusion coefficients in granitoid melts are estimated. The Ta and Nb diffusion coefficients at <i>T</i> = 750°C and <i>P</i> = 100 MPa are ~10^–10 cm²/s, and those of Fe and Mn are ~10^–8.5 cm²/s. With an increase in temperature from 740 to 980°C, all of the diffusion coefficients increase by approximately 1.5 orders of magnitude. The configurations of the diffusion profiles of Ta concentration in melts change differently depending on change in the composition of the melt, temperature, or pressure.</p>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4629135","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}

{"title":"Re-Os Isotope and HSE Abundance Systematics of the 2.9 Ga Komatiites and Basalts from the Sumozero-Kenozero Greenstone Belt, SE Fennoscandian Shield: Implications for the Mixing Rates of the Mantle","authors":"Igor S. Puchtel","doi":"10.1134/S0869591122060054","DOIUrl":"10.1134/S0869591122060054","url":null,"abstract":"<p>Rhenium-Os isotope and highly siderophile element (HSE, including Re, Os, Ir, Ru, Pt, and Pd) abundance systematics of Archean komatiites can be used to estimate the stirring rates of the mantle for the HSE and the timing of homogenization of late accreted materials within the mantle. In this study, we report Re-Os isotope and HSE abundance data for ~2.9 Ga komatiites and basalts from the Sumozero-Kenozero greenstone belt in the SE Fennoscandian Shield. The lavas are characterized by excellent preservation of the primary textural, chemical, and Re-Os isotope characteristics. The Re-Os isotopic data for spinifex-textured and cumulate komatiite and massive basalt samples from the lowermost sequences define a precise 10-point isochron (MSWD = 2.6) with an age of 2904 ± 18 Ma and an initial ¹⁸⁷Os/¹⁸⁸Os = 0.10758 ± 18 (γ¹⁸⁷Os(2904) = +0.45 ± 0.17). This is the first direct age determination for the Sumozero-Kenozero lower komatiite-basalt sequences. Our modeling indicates that the mantle source of the komatiites and basalts evolved with a time-integrated ¹⁸⁷Re/¹⁸⁸Os = 0.418 ± 6. This ratio is well within the uncertainty of the bulk chondritic average ¹⁸⁷Re/¹⁸⁸Os = 0.410 ± 51 (2SD), also consistent with the chondritic evolution of the majority of komatiite mantle sources observed globally. The mantle source of the Sumozero-Kenozero komatiites has been calculated to contain the total HSE abundances of 58 ± 7% of those in the estimates for modern Bulk Silicate Earth (BSE). This estimate is in the middle of the range for other late Archean and Proterozoic komatiite systems. Using the estimated HSE abundances in the sources of komatiite systems as a function of their ages and ISOPLOT regression analysis, we calculated the average time in the past by which late accreted materials have been completely homogenized within the mantle to be 2.48 ± 0.23 Ga. These data require that the residence times of the late accreted planetesimals within the mantle, before complete homogenization, were on average 1.92 ± 0.23 Ga. This estimate represents a constraint on the average mixing rates of the mantle in terms of the HSE abundances in the Hadean and the Archean.</p>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4626498","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}

{"title":"The Kulikovs: A Family of Geologists. Vyacheslav Stepanovich Kulikov, Viktoria Vladimirovna Kulikova, and Yana Vyacheslavovna Bychkova (Kulikova)","authors":"","doi":"10.1134/S0869591122060108","DOIUrl":"10.1134/S0869591122060108","url":null,"abstract":"","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4064103","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}

{"title":"Mineralogical, Geochemical, and Nd-Sr Isotope Characteristics of Amphibolites from the Alag-Khadny High-Pressure Complex (SW Mongolia): Intracontinental Rifting as a Precursor of Continental-Margin Subduction","authors":"S. Yu. Skuzovatov,&nbsp;M. A. Gornova,&nbsp;A. A. Karimov","doi":"10.1134/S0869591122040051","DOIUrl":"10.1134/S0869591122040051","url":null,"abstract":"<div><p>Within subduction-accretion complexes, high-pressure rocks (blueschists, eclogites) are commonly juxtaposed with lower-grade rocks, which represent their retrograded counterparts or were involved into accretionary event at later stages, and thus characterize distinct stages of evolution of accretionary belts. In SW Mongolia, the Central Asian Orogenic Belt includes Neoproterozoic–Early Paleozoic paleosubduction complexes represented by eclogites and associated rocks of the Alag-Khadny accretionary complex. This paper reports the results of mineralogical, geochemical and isotopic studies of amphibolites from this complex, the geochemical nature and relationships of which with eclogites have been yet uncertain. The texture of the studied rocks varies from fine- and medium-grained granoblastic and nematoblastic amphibole–plagioclase–epidote rocks to medium-grained nematoblastic amphibole–epidote–albite–titanite amphibolites, which experienced intense recrystallization as a response to late deformations. Primary assemblages include pargasite and Mg-hornblende (^[B]Na = 0.07–0.16, ^IVAl = 0.79–1.69, ^[A](Na + K + 2Ca) = 0.14–0.64, ^[C](Al+ Ti + Fe³⁺) = 0.58–1.29, Fe²⁺/(Fe²⁺ + Mg) = 0.18–0.46 at Fe³⁺/(Fe³⁺+Al) = 0.18–0.77), low-to-medium-Ca plagioclase (<i>An</i>_24–36), and epidote–clinozoisite (0.08 &lt; <span>({{X}_{{{text{F}}{{{text{e}}}^{{{text{3 + }}}}}}}})</span> &lt; 0.16), whereas the retrograde assemblage is represented by albite and Mg-hornblende. Calculations using amphibole composition and amphibole/amphibole–plagioclase thermobarometry revealed peak <i>P-T</i> conditions up to 570–630°С and 7–9 kbar ascribed to the high-<i>T</i> epidote-amphibolite facies with subsequent greenschist-facies retrogression. The major-element composition of the amphibolites corresponds to low-alkali moderate-Ti tholeiites, although their trace-element composition varies significantly from N-MORB to E-MORB-type basalts, which are variably enriched in LREE, Nb, Ta, Th, U, and show negative Eu and Ti anomalies due to fractionation of parental melts for precursor rocks. Isotopic composition of Nd (ε_Nd(550) from +5.1 to –9.1) and Sr ((⁸⁷Sr/⁸⁶Sr)₅₅₀ = 0.7057–0.7097) indicates distinct mainly moderately-depleted nature of mantle sources for the mafic rocks, but also highlights the involvement of “anomalous” mantle domains with unradiogenic Nd composition. The data supports that the precursor rocks of the amphibolites were formed during intracontinental extension of a continental margin, which was likely linked to opening of a limited Neoproterozoic oceanic basin with a subsequent Late Vendian–Early Cambrian convergence. The medium- to high-pressure metamorphism of amphibolites had similar <i>P-T</i> conditions to that of retrograde metamorphism of eclogites and associated metasediments and was directly related t","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2022-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4279408","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}