Petrology and thermobarometry of eclogite rocks in the Krasnaya Guba dike field, belomorian mobile belt

Kozlovskii, V. M.; Aranovich, L. Ya.

doi:10.1134/s0869591110010029

Cited by 25 publications

(6 citation statements)

References 17 publications

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“…The absence of omphacite inclusions is regarded as an argument of that Archean eclogites do not exist. Paleoproterozoic eclogites were derived after gabbroic rock dikes and locally make up boudins or their fragments [14,26,27,[32][33][34]. The Paleoproterozoic age of these eclogites is reliably supported by heavy REE-depleted zircons with mineral inclusions of omphacite, garnet, and kyanite, as well as Sm-Nd and Lu-Hf mineral isochrons.…”

Section: Introductionmentioning

confidence: 99%

Archean Zircons with Omphacite Inclusions from Eclogites of the Belomorian Province, Fennoscandian Shield: The First Finding

et al. 2021

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Early Precambrian retrogressed eclogites are abundant in the central and northern parts of the Belomorian Province of the Fennoscandian Shield (Gridino + Keret and Salma + Kuru-Vaara study areas, respectively). Older and younger eclogites are recognized and their Archean and Paleoproterozoic ages are argued. Archean eclogites are intensely retrogressed and occur in amphibolite boudins in the tonalite-trondhjemite-granodiorite (TTG) gneiss matrix of the Archean Gridino eclogite-bearing mélange. Less retrogressed Paleoproterozoic eclogites form patches in mafic dikes and some amphibolite boudins; their Paleoproterozoic age is supported by U-Pb/SIMS data on zircons depleted in heavy rare earth elements (REE) with omphacite, garnet, and kyanite inclusions, and Sm-Nd and Lu-Hf mineral isochrons. Archean eclogites contain Archean heavy rare-earth elements (REE)-depleted zircons with garnet and zoisite inclusions and Archean garnets. No omphacite inclusions were found in these zircons, and this fact was considered as evidence against the existence of Archean eclogites. This study reports on the first finding of omphacite (23–25% Jd) inclusions in 2.68 Ga metamorphic zircons from eclogites from the Gridino eclogite-bearing mélange. The zircons are poorly enriched in heavy REE and display a weak negative Eu-anomaly but a poor positive Ce-anomaly typical of eclogitic zircons. Thus, zircons with these decisive features provide evidence for an Archean eclogite-facies metamorphism.

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Section: Introductionmentioning

confidence: 99%

Archean Zircons with Omphacite Inclusions from Eclogites of the Belomorian Province, Fennoscandian Shield: The First Finding

et al. 2021

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“…Mafites of Krasnaya Guba are intensively eclogitized (gabbro norites along zones of shear deformations, gabbro almost completely). Based on mineral geother mobarometry [3], formation of eclogite like rocks (plagioclase + garnet + omphacite) took place at P-T conditions corresponding to HP-HT amphibolite facies metamorphism (T = 700 ± 40°С and Р = 10.0 ± 0.5 kbar. The P-T parameters of formation of cli nopyroxene-plagioclase symplectites after omphacite are 7.9-8.2 kbar and 630-660°C.…”

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“…The fea tures of the mineral compositions of eclogite like rocks of Krasnaya Guba can be explained well by the assumption of mobile behavior of silica and desilica tion of mafites [1,3] as a result of fluid rock interac tion in tectonic zones.…”

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confidence: 99%

“…It seems evident that fluid acts in the eclogitization process not only as a catalyst for mineral reactions, but also as the medium of heat exchange and mass exchange. This work is aimed at revealing regularities of pos sible geochemical changes in mafites from the exam ple of two spatially juxtaposed complexes of different ages, which formed in different geodynamic set tings, but they were subjected simultaneously to the Paleoproterozoic metamorphic event.The object of this study is the Krasnaya Guba dike field, which comprises more than 30 small gabbro norite intrusions and dikes of more ferruginous (gar net) gabbro [3]. The age of their formation is probably the same as that of analogical rocks in this region (2.44-2.36 and 2.14-2.12 Ga, respectively) [5].…”

mentioning

confidence: 99%

“…The object of this study is the Krasnaya Guba dike field, which comprises more than 30 small gabbro norite intrusions and dikes of more ferruginous (gar net) gabbro [3]. The age of their formation is probably the same as that of analogical rocks in this region (2.44-2.36 and 2.14-2.12 Ga, respectively) [5].…”

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Geochemistry of metabasites of Krasnaya Guba, Belomorian Mobile Belt

et al. 2012

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The modern ideas on evolution of the Early Pre cambrian continental crust are based on the geochem istry of mafites, which is a direct indicator of geodynamic settings. Within the ancient complexes, the Baltic Shield, in particular, mafites are often metamorphosed. In con nection with this, there is a question whether their geochemistry corresponds to that of the primary mag matic rocks. Considering the regional metamorphism as an isochemical process, all the geochemical differ ences between metamorphosed rocks usually are explained by differences in the probable protolith compositions. However, currently, more and more data on the geochemistry of metamorphosed mafites derived from a similar protolith appear. Accordingly, differences in their geochemistry are possible, if mobility of particular components during metamor phism is suggested. The results of studying Proterozoic komatiites and komatiitic basalts (certainly, magmatic formations of Karelia (the eastern area of the Baltic Shield)) allow us to suggest that variations in the dis tribution of some of their major and minor elements are due to superimposed metamorphism [4,[12][13][14].Study of fluid inclusions in minerals from rocks metamorphosed under high pressure conditions (Nor wegian eclogites and granulites, in particular) has shown the occurrence of volatile and alkaline compo nents in these rocks, along with H 2 O and CO 2 [10]. All this testifies to the possibility of dissolution and mobil ity of a great amount of components in dependence on the physicochemical conditions. It should be noted that the role of deformations and associated fluid flows in the formation of eclogite mineral parageneses is of particular interest [1]. As an example, in high salt fluid inclusions in omphacite from eclogites of the Bergen Arcs (Norway), confined to the deformation zone, some 18 daughter phases with significant rare element concentrations were established [10]; i.e., formation of these eclogites is controlled not only by the protolith composition and metamorphism condi tions and but also depends on increasing fluid activity in the deformation zone. Eclogitization of rocks in the Gridinskaya mélange zone of the Belomorian Mobile Belt also probably resulted from shear deformations and fluid interaction [7]. It seems evident that fluid acts in the eclogitization process not only as a catalyst for mineral reactions, but also as the medium of heat exchange and mass exchange. This work is aimed at revealing regularities of pos sible geochemical changes in mafites from the exam ple of two spatially juxtaposed complexes of different ages, which formed in different geodynamic set tings, but they were subjected simultaneously to the Paleoproterozoic metamorphic event.The object of this study is the Krasnaya Guba dike field, which comprises more than 30 small gabbro norite intrusions and dikes of more ferruginous (gar net) gabbro [3]. The age of their formation is probably the same as that of analogical rocks in this region (2.44-2.36 and 2.14-2.12 Ga, respectively) [5]. ...

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Zircon and muscovite ages, geochemistry, and Nd–Hf isotopes for the Aktyuz metamorphic terrane: Evidence for an Early Ordovician collisional belt in the northern Tianshan of Kyrgyzstan

Kröner

Алексеев

Hegner³

et al. 2012

Gondwana Research

170

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Petrology and thermobarometry of eclogite rocks in the Krasnaya Guba dike field, belomorian mobile belt

Cited by 25 publications

References 17 publications

Archean Zircons with Omphacite Inclusions from Eclogites of the Belomorian Province, Fennoscandian Shield: The First Finding

Archean Zircons with Omphacite Inclusions from Eclogites of the Belomorian Province, Fennoscandian Shield: The First Finding

Geochemistry of metabasites of Krasnaya Guba, Belomorian Mobile Belt

Zircon and muscovite ages, geochemistry, and Nd–Hf isotopes for the Aktyuz metamorphic terrane: Evidence for an Early Ordovician collisional belt in the northern Tianshan of Kyrgyzstan

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