Most films used to preserve foodstuffs are made from synthetic plastic materials. However, for en... more Most films used to preserve foodstuffs are made from synthetic plastic materials. However, for environmental reasons, attention has recently turned to biodegradable films. Gelatin has been extensively studied for its film forming capacity and applicability as an outer covering to protect food against drying, light, and oxygen. Moreover, it is one of the first materials proposed as a carrier of bioactive components. Gelatins from alternatives to mammalian species are gaining prominence, especially gelatins from marine fish species. Because of their good film-forming abilities, fish gelatins may be a good alternative to synthetic plastics for making films to preserve foodstuffs. The mechanical and barrier properties of these films depend largely on the physical and chemical characteristics of the gelatin, especially the amino acid composition, which is highly species specific, and the molecular weight distribution, which depends mainly on processing conditions. Different film formulations can be developed to extend the films' physical and chemical properties and to add new functional attributes. This paper reviews the most recent scientific literature dealing with films based on gelatins from different fish species and considers various strategies intended to improve the physical properties of such films by combining fish gelatins with such other biopolymers as soy protein isolate, oils and fatty acids, and certain polysaccharides. The use of plasticizers and cross-linking agents is also discussed. Specific attributes, such as antimicrobial and antioxidant activities, may be also conferred by blending the gelatin with chitosan, lysozyme, essential oils, plant extracts, or vitamin C to produce an active packaging biomaterial.
A characterisation of non-protein nitrogen (NPN) was carried out in the muscle of three species o... more A characterisation of non-protein nitrogen (NPN) was carried out in the muscle of three species of cephalopods: volador (Illex coindetii), pota (Todaropsis eblanae) and octopus (Eledone cirrhosa). These species were classified according to sex, sexual development (immature, mature) and anatomical zone (mantle, arms). There were no major differences in the NPN contents of the three species studied. The anatomical zone clearly marks the difference in NPN content, with the content being greater in the mantle than in the arms for all the species. The trimethylamine oxide-nitrogen levels in volador were greater in the mantle than in the arms and these differences were not observed in the other two species. In pota and octopus, however, it is the stage of sexual development that exhibited differences, with a greater quantity of trimethylamine oxide-nitrogen in the immature specimens than the mature ones. The trimethlyl and total volatile basic nitrogen behaviour had no clear trend, the TVB-N levels were probably so low that these differences were not important. The same thing occurred with the pH, where the lowest values were recorded in octopus and the highest in pota. The free amino acid (FAA) compositions varied to a great extent, depending on the species and, to a less extent, depending on the sex, stage of sexual development and anatomical zone. The total FAA content was virtually the same in volador and pota, while it was about 75% lower in octopus. The highest concentrations of FAA in the three species were for proline, arginine and alanine, but in different proportions.
High pressure, at 250 and 400 MPa, for 10 or 20 min, was applied at either of two stages: during ... more High pressure, at 250 and 400 MPa, for 10 or 20 min, was applied at either of two stages: during pre-treatment in acid at 10 8C to facilitate destabilisation of acid labile crosslinks, or during extraction in water at 45 8C to accelerate collagen hydrolysis. The resulting gelatins were evaluated in terms of yield of extraction, molecular weight distribution by SDS-PAGE, and viscoelastic properties of gelatin newly dissolved and after overnight cold maturation. Pressure level and time of treatment induced noticeable changes in molecular weight distribution and consequently affected viscoelastic properties. The use of high pressure to extract gelatin from fish skins is a useful alternative to the conventional procedure. Its utility lies basically in that the longest phase of the treatment can be drastically shortened, thus making it possible to produce a gelatin of high gelling quality in only a few minutes.
U-Pb ion-microprobe zircon dating of the Moneiga quartz-diorites, located within the Katherine ri... more U-Pb ion-microprobe zircon dating of the Moneiga quartz-diorites, located within the Katherine ring-complex of the Sinai, reveals a crystallization age of 844±4Ma and the presence of 1045Ma pre-magmatic zircon cores. These rocks are much older than previously believed, and represent the oldest magmatic rocks so far dated in the Sinai. Their chemical composition corresponds to mildly silicic, low- to medium-K,
ABSTRACT The Awsard-Tichla zone, in the Moroccan sector of the Reguibat Rise, comprises three lit... more ABSTRACT The Awsard-Tichla zone, in the Moroccan sector of the Reguibat Rise, comprises three lithodemic units, the TTG Aghaylas Suite, the Tichla greenstone belt, and the intrusive feldspathoidal syenites of the Awsard-Lechuaf group. The Aghaylas suite consists of Mesoarchean tonalites and trondhjemites with minor granodiorites and granites that are locally migmatised. These rocks are notably depleted in HREE, Y, Nb, Ta, and U, with elevated Th/U and K/Rb, 87Sr/86Sr(t) from 0.7003 to 0.7030, ɛNd(t) from +2 to +5, and Nd model ages in the range TCR = 3.03 - 2.92 Ga. Eight TTG gneisses yielded SHRIMP U-Pb zircon crystallisation ages between 3.04 Ga and 2.92 Ga. One TTG leucocratic gneiss from the neighbouring Oulad Dlim sector has a TCR = 3.09 and a zircon crystallisation age of 2.94 Ga but also contains a 3.11 Ga population of pre-magmatic zircons. The Tichla greenstone belt, on the other hand, was formed between 3.03 Ga and 3.01 Ga, though Nd model ages suggest the contribution of an older crust. Field evidence and the chemical and isotopic compositions of the TTGs are consistent with crustal recycling of slightly younger juvenile TTG. After 2.92 Ga there is no trace of magmatic activity until the intrusion of the Awsard feldspathoidal (kalsilite and nepheline) syenites at 2.46 Ga. This reveals that, for reasons that are not yet well understood, the Archean crust in this sector of the Reguibat Rise stabilised long before than any other surrounding cratonic area. Furthermore, the crust stayed stable until the Archean-Proterozoic transition that, here, was marked by a peculiar high-K silica-subsaturated magmatism more extreme in composition than in any other known Archean terrane.
New U-Pb zircon data from metagranites and metavolcanic rocks of the Schist-Graywacke Complex Dom... more New U-Pb zircon data from metagranites and metavolcanic rocks of the Schist-Graywacke Complex Domain and the Schistose Domain of Galicia Tras-os-Montes Zone from central and NW Iberia contribute to constrain the timing of the Cambro-Ordovician magmatism from Central Iberian and Galicia Tras-os-Montes Zones which occurred between 498 and 462 Ma. The crystallization ages of the metagranites and metavolcanic rocks from the Northern Schist
ABSTRACT The Khalifan pluton of the Sanandaj-Sirjan Zone is composed of A-type peraluminous leuco... more ABSTRACT The Khalifan pluton of the Sanandaj-Sirjan Zone is composed of A-type peraluminous leucogranites with Nd model ages around 1.2 Ga. It intrudes an unfossiliferous sedimentary sequence previously considered as Cretaceous by analogy with neighboring areas. However, zircon U-Pb SHRIMP and Pb-Pb sequential evaporation dating have revealed that Khalifan granites are Carboniferous, with a precise age of 315 2 Ma. This is the first reliable Variscan age obtained so far in this area, but there are geological indicators that other small plutonic bodies might also be Variscan. The existence of Carboniferous granite rocks in the Sanandaj-Sirjan Zone casts doubts on whether it was a part of the Cimmerian superterrane detached from east Gondwanide terranes because these characteristically lack Variscan magmatism. The age, chemical features and Nd isotopes of Khalifan granites are similar to those of the southernmost Urals and Tien Shan, so that we tentatively suggest that this area bears a Middle Asian instead of Cimmerian linkage.
The crustal structure in the Baltic Shield is determined by a system of geological blocks, which ... more The crustal structure in the Baltic Shield is determined by a system of geological blocks, which formed at different evolutionary stages of this largest stable Precambrian domain. Cratonization of the Archean Karelian, Kola, and Belomorian domains terminated after the Svecofennian orogeny 1.88-1.75 Ga ago [1]. Up to now, the principal structural elements of the shield formed by that time have remained practically unchanged over its entire area. The Paleozoic lithospheric plume-related processes that were responsible for the formation of the Kola alkaline province 0.38-0.36 Ga ago [2] did not provoke systemic transformations of the Precambrian basement. Thus, the geological history of the ancient Archean core of Fennoscandia included a long-term (>1.3 Ga) amagmatic period. However, structural reorganization related to the Sveconorwegian orogenesis took place in the southwestern areas of the shield considered as a continuation of the Grenvillian foldbelt of North America [3]. This stage, manifested 1.20-0.93 Ga ago as substantial deformations of the basement and formation of high-grade metamorphic belts, was accompanied by bimodal magmatism ranging from mantle-related basites to typically crustal late orogenic granitoids. Basites represented by
This paper is an attempt to summarize current knowledge of Uralian magmatism, focusing on those a... more This paper is an attempt to summarize current knowledge of Uralian magmatism, focusing on those aspects relevant for understanding its geodynamic evolution. The Urals consist of three tectonomagmatic domains: a Suture Sector, in the west, and two N-S imbricated Island-Arc Continental Sectors in the east. The Suture Sector comprises lower Palaeozoic mafic-ultramafic complexes which show eastward impoverishment in LILE, thus reflecting the transition of the subcontinental lithospheric mantle of the Russian plate to the suboceanic lithospheric mantle of the subducted Uralian palaeo-ocean. The two Island-Arc Continental Sectors represent the transition from oceanic to continental environments in the middle and south Urals. Collisional magmatism started in the Silurian and persisted till the Permian, migrating progressively eastward and increasing in abundance of LILE and 87Sr/S6Sri,~. Magmatic polarity is very similar to that of modern subduction zones and indicates that the subducted slab was dipping eastward during that period. The Northern and Southern Island-Arc Continental Sectors show many similarities regarding the nature and spatial-temporal distribution of magmatism, but there are also some important differences which probably indicate somewhat different geodynamic regimes. In the Northern Sector, Carboniferous tonalite-granodiorite batholiths have features compatible with an origin by melting of the oceanic crust in the subducted slab. In the Southern Sector, however, Carboniferous tonalite-granodiorite batholiths have features more consistent with a melting event within the lower continental crust above the subduction zone than with melting within the subducted slab. Upper Carboniferous-Permian granites have high 87Sr/86Srinitial in the north (e.g., 0.7120 in the Murzinka batholith) but very low 87Sr/~Sri,i~ in the south (e.g., 0.7045 in the Dzhabyk batholith) in spite of rocks from both batholiths being equally peraluminous and showing evidence of derivation by anatexis of metasediments. The low 87Sr/86Srinitial at Dzhabyk might indicate that in the Southern Sector the accretionary prism grew very rapidly, thus allowing involvement in upper Palaeozoic melting events.
In order to elucidate evolutionary paths for the alkaline ultramafic series of the Kola province,... more In order to elucidate evolutionary paths for the alkaline ultramafic series of the Kola province, we studied distribution of rare earth elements (REE) in rocks and constituent minerals of the rock sequence dunite, clinopyroxenite, melilitolite, meltejgite, ijolite, nepheline syenite. Abundances of REE and other trace elements were measured in olivine, melilite, clinopyroxene, nepheline, apatite, perovskite, titanite, and magnetite. Distribution of most trace elements in Kovdor-type rocks is shown to differ fundamentally from that in the Khibiny alkaline ultramafic suite and to have been controlled by perovskite crystallization. Primary olivine melanephelinitic melts of the Kovdor series are demonstrated to be characterized by early crystallization of perovskite, the most important REE mineral. Perovskite co-precipitating with olivine and clinopyroxene leads to a sharp REE depletion of the residual melt, to produce REE-depleted derivatives, ijolites and nepheline syenites. By contrast, the genesis of the Khibiny alkaline ultramafic series was complicated by mixing of minor batches of phonolitic melt with the primary olivine melanephelinitic magma, which led to changes in the crystallization order of REE-bearing titanates and Ti-silicates and to enrichment of late melt batches in the most incompatible elements. As a result, Khibiny ijolites have the highest REE abundances, which are accommodated by high-REE apatite and titanite.
Single zircon U-Pb dating by ion microprobe and Pb-evaporation techniques, combined with Sr-Nd is... more Single zircon U-Pb dating by ion microprobe and Pb-evaporation techniques, combined with Sr-Nd isotopic and geochemical data, constrain the pre- and early Uralian evolution of the Marun-Keu eclogite-facies metamorphic complex. Polar Urals, Russia. The complex is interpreted as a part of the Early Palaeozoic East European passive margin, subducted, metamorphosed and exhumed during Uralian arc-continent collision. In the Marun-Keu complex, a variety of meta-igneous and metasedimentary rocks documents different evolutionary stages of the northeastern margin of Baltica. Both the oldest, polystage detrital zircon population, which is 570 to 700 Ma in age, and the dominant zircon population in an island arc-type magmatic suite (c. 550 Ma) are related to the Neoproterozoic Timanian orogeny, which resulted in continental growth of northeastern Europe by accretion of juvenile oceanic and island arc material. A distinct magmatic event at c. 490 Ma is documented in zircons from metagranites, a...
Most films used to preserve foodstuffs are made from synthetic plastic materials. However, for en... more Most films used to preserve foodstuffs are made from synthetic plastic materials. However, for environmental reasons, attention has recently turned to biodegradable films. Gelatin has been extensively studied for its film forming capacity and applicability as an outer covering to protect food against drying, light, and oxygen. Moreover, it is one of the first materials proposed as a carrier of bioactive components. Gelatins from alternatives to mammalian species are gaining prominence, especially gelatins from marine fish species. Because of their good film-forming abilities, fish gelatins may be a good alternative to synthetic plastics for making films to preserve foodstuffs. The mechanical and barrier properties of these films depend largely on the physical and chemical characteristics of the gelatin, especially the amino acid composition, which is highly species specific, and the molecular weight distribution, which depends mainly on processing conditions. Different film formulations can be developed to extend the films' physical and chemical properties and to add new functional attributes. This paper reviews the most recent scientific literature dealing with films based on gelatins from different fish species and considers various strategies intended to improve the physical properties of such films by combining fish gelatins with such other biopolymers as soy protein isolate, oils and fatty acids, and certain polysaccharides. The use of plasticizers and cross-linking agents is also discussed. Specific attributes, such as antimicrobial and antioxidant activities, may be also conferred by blending the gelatin with chitosan, lysozyme, essential oils, plant extracts, or vitamin C to produce an active packaging biomaterial.
A characterisation of non-protein nitrogen (NPN) was carried out in the muscle of three species o... more A characterisation of non-protein nitrogen (NPN) was carried out in the muscle of three species of cephalopods: volador (Illex coindetii), pota (Todaropsis eblanae) and octopus (Eledone cirrhosa). These species were classified according to sex, sexual development (immature, mature) and anatomical zone (mantle, arms). There were no major differences in the NPN contents of the three species studied. The anatomical zone clearly marks the difference in NPN content, with the content being greater in the mantle than in the arms for all the species. The trimethylamine oxide-nitrogen levels in volador were greater in the mantle than in the arms and these differences were not observed in the other two species. In pota and octopus, however, it is the stage of sexual development that exhibited differences, with a greater quantity of trimethylamine oxide-nitrogen in the immature specimens than the mature ones. The trimethlyl and total volatile basic nitrogen behaviour had no clear trend, the TVB-N levels were probably so low that these differences were not important. The same thing occurred with the pH, where the lowest values were recorded in octopus and the highest in pota. The free amino acid (FAA) compositions varied to a great extent, depending on the species and, to a less extent, depending on the sex, stage of sexual development and anatomical zone. The total FAA content was virtually the same in volador and pota, while it was about 75% lower in octopus. The highest concentrations of FAA in the three species were for proline, arginine and alanine, but in different proportions.
High pressure, at 250 and 400 MPa, for 10 or 20 min, was applied at either of two stages: during ... more High pressure, at 250 and 400 MPa, for 10 or 20 min, was applied at either of two stages: during pre-treatment in acid at 10 8C to facilitate destabilisation of acid labile crosslinks, or during extraction in water at 45 8C to accelerate collagen hydrolysis. The resulting gelatins were evaluated in terms of yield of extraction, molecular weight distribution by SDS-PAGE, and viscoelastic properties of gelatin newly dissolved and after overnight cold maturation. Pressure level and time of treatment induced noticeable changes in molecular weight distribution and consequently affected viscoelastic properties. The use of high pressure to extract gelatin from fish skins is a useful alternative to the conventional procedure. Its utility lies basically in that the longest phase of the treatment can be drastically shortened, thus making it possible to produce a gelatin of high gelling quality in only a few minutes.
U-Pb ion-microprobe zircon dating of the Moneiga quartz-diorites, located within the Katherine ri... more U-Pb ion-microprobe zircon dating of the Moneiga quartz-diorites, located within the Katherine ring-complex of the Sinai, reveals a crystallization age of 844±4Ma and the presence of 1045Ma pre-magmatic zircon cores. These rocks are much older than previously believed, and represent the oldest magmatic rocks so far dated in the Sinai. Their chemical composition corresponds to mildly silicic, low- to medium-K,
ABSTRACT The Awsard-Tichla zone, in the Moroccan sector of the Reguibat Rise, comprises three lit... more ABSTRACT The Awsard-Tichla zone, in the Moroccan sector of the Reguibat Rise, comprises three lithodemic units, the TTG Aghaylas Suite, the Tichla greenstone belt, and the intrusive feldspathoidal syenites of the Awsard-Lechuaf group. The Aghaylas suite consists of Mesoarchean tonalites and trondhjemites with minor granodiorites and granites that are locally migmatised. These rocks are notably depleted in HREE, Y, Nb, Ta, and U, with elevated Th/U and K/Rb, 87Sr/86Sr(t) from 0.7003 to 0.7030, ɛNd(t) from +2 to +5, and Nd model ages in the range TCR = 3.03 - 2.92 Ga. Eight TTG gneisses yielded SHRIMP U-Pb zircon crystallisation ages between 3.04 Ga and 2.92 Ga. One TTG leucocratic gneiss from the neighbouring Oulad Dlim sector has a TCR = 3.09 and a zircon crystallisation age of 2.94 Ga but also contains a 3.11 Ga population of pre-magmatic zircons. The Tichla greenstone belt, on the other hand, was formed between 3.03 Ga and 3.01 Ga, though Nd model ages suggest the contribution of an older crust. Field evidence and the chemical and isotopic compositions of the TTGs are consistent with crustal recycling of slightly younger juvenile TTG. After 2.92 Ga there is no trace of magmatic activity until the intrusion of the Awsard feldspathoidal (kalsilite and nepheline) syenites at 2.46 Ga. This reveals that, for reasons that are not yet well understood, the Archean crust in this sector of the Reguibat Rise stabilised long before than any other surrounding cratonic area. Furthermore, the crust stayed stable until the Archean-Proterozoic transition that, here, was marked by a peculiar high-K silica-subsaturated magmatism more extreme in composition than in any other known Archean terrane.
New U-Pb zircon data from metagranites and metavolcanic rocks of the Schist-Graywacke Complex Dom... more New U-Pb zircon data from metagranites and metavolcanic rocks of the Schist-Graywacke Complex Domain and the Schistose Domain of Galicia Tras-os-Montes Zone from central and NW Iberia contribute to constrain the timing of the Cambro-Ordovician magmatism from Central Iberian and Galicia Tras-os-Montes Zones which occurred between 498 and 462 Ma. The crystallization ages of the metagranites and metavolcanic rocks from the Northern Schist
ABSTRACT The Khalifan pluton of the Sanandaj-Sirjan Zone is composed of A-type peraluminous leuco... more ABSTRACT The Khalifan pluton of the Sanandaj-Sirjan Zone is composed of A-type peraluminous leucogranites with Nd model ages around 1.2 Ga. It intrudes an unfossiliferous sedimentary sequence previously considered as Cretaceous by analogy with neighboring areas. However, zircon U-Pb SHRIMP and Pb-Pb sequential evaporation dating have revealed that Khalifan granites are Carboniferous, with a precise age of 315 2 Ma. This is the first reliable Variscan age obtained so far in this area, but there are geological indicators that other small plutonic bodies might also be Variscan. The existence of Carboniferous granite rocks in the Sanandaj-Sirjan Zone casts doubts on whether it was a part of the Cimmerian superterrane detached from east Gondwanide terranes because these characteristically lack Variscan magmatism. The age, chemical features and Nd isotopes of Khalifan granites are similar to those of the southernmost Urals and Tien Shan, so that we tentatively suggest that this area bears a Middle Asian instead of Cimmerian linkage.
The crustal structure in the Baltic Shield is determined by a system of geological blocks, which ... more The crustal structure in the Baltic Shield is determined by a system of geological blocks, which formed at different evolutionary stages of this largest stable Precambrian domain. Cratonization of the Archean Karelian, Kola, and Belomorian domains terminated after the Svecofennian orogeny 1.88-1.75 Ga ago [1]. Up to now, the principal structural elements of the shield formed by that time have remained practically unchanged over its entire area. The Paleozoic lithospheric plume-related processes that were responsible for the formation of the Kola alkaline province 0.38-0.36 Ga ago [2] did not provoke systemic transformations of the Precambrian basement. Thus, the geological history of the ancient Archean core of Fennoscandia included a long-term (>1.3 Ga) amagmatic period. However, structural reorganization related to the Sveconorwegian orogenesis took place in the southwestern areas of the shield considered as a continuation of the Grenvillian foldbelt of North America [3]. This stage, manifested 1.20-0.93 Ga ago as substantial deformations of the basement and formation of high-grade metamorphic belts, was accompanied by bimodal magmatism ranging from mantle-related basites to typically crustal late orogenic granitoids. Basites represented by
This paper is an attempt to summarize current knowledge of Uralian magmatism, focusing on those a... more This paper is an attempt to summarize current knowledge of Uralian magmatism, focusing on those aspects relevant for understanding its geodynamic evolution. The Urals consist of three tectonomagmatic domains: a Suture Sector, in the west, and two N-S imbricated Island-Arc Continental Sectors in the east. The Suture Sector comprises lower Palaeozoic mafic-ultramafic complexes which show eastward impoverishment in LILE, thus reflecting the transition of the subcontinental lithospheric mantle of the Russian plate to the suboceanic lithospheric mantle of the subducted Uralian palaeo-ocean. The two Island-Arc Continental Sectors represent the transition from oceanic to continental environments in the middle and south Urals. Collisional magmatism started in the Silurian and persisted till the Permian, migrating progressively eastward and increasing in abundance of LILE and 87Sr/S6Sri,~. Magmatic polarity is very similar to that of modern subduction zones and indicates that the subducted slab was dipping eastward during that period. The Northern and Southern Island-Arc Continental Sectors show many similarities regarding the nature and spatial-temporal distribution of magmatism, but there are also some important differences which probably indicate somewhat different geodynamic regimes. In the Northern Sector, Carboniferous tonalite-granodiorite batholiths have features compatible with an origin by melting of the oceanic crust in the subducted slab. In the Southern Sector, however, Carboniferous tonalite-granodiorite batholiths have features more consistent with a melting event within the lower continental crust above the subduction zone than with melting within the subducted slab. Upper Carboniferous-Permian granites have high 87Sr/86Srinitial in the north (e.g., 0.7120 in the Murzinka batholith) but very low 87Sr/~Sri,i~ in the south (e.g., 0.7045 in the Dzhabyk batholith) in spite of rocks from both batholiths being equally peraluminous and showing evidence of derivation by anatexis of metasediments. The low 87Sr/86Srinitial at Dzhabyk might indicate that in the Southern Sector the accretionary prism grew very rapidly, thus allowing involvement in upper Palaeozoic melting events.
In order to elucidate evolutionary paths for the alkaline ultramafic series of the Kola province,... more In order to elucidate evolutionary paths for the alkaline ultramafic series of the Kola province, we studied distribution of rare earth elements (REE) in rocks and constituent minerals of the rock sequence dunite, clinopyroxenite, melilitolite, meltejgite, ijolite, nepheline syenite. Abundances of REE and other trace elements were measured in olivine, melilite, clinopyroxene, nepheline, apatite, perovskite, titanite, and magnetite. Distribution of most trace elements in Kovdor-type rocks is shown to differ fundamentally from that in the Khibiny alkaline ultramafic suite and to have been controlled by perovskite crystallization. Primary olivine melanephelinitic melts of the Kovdor series are demonstrated to be characterized by early crystallization of perovskite, the most important REE mineral. Perovskite co-precipitating with olivine and clinopyroxene leads to a sharp REE depletion of the residual melt, to produce REE-depleted derivatives, ijolites and nepheline syenites. By contrast, the genesis of the Khibiny alkaline ultramafic series was complicated by mixing of minor batches of phonolitic melt with the primary olivine melanephelinitic magma, which led to changes in the crystallization order of REE-bearing titanates and Ti-silicates and to enrichment of late melt batches in the most incompatible elements. As a result, Khibiny ijolites have the highest REE abundances, which are accommodated by high-REE apatite and titanite.
Single zircon U-Pb dating by ion microprobe and Pb-evaporation techniques, combined with Sr-Nd is... more Single zircon U-Pb dating by ion microprobe and Pb-evaporation techniques, combined with Sr-Nd isotopic and geochemical data, constrain the pre- and early Uralian evolution of the Marun-Keu eclogite-facies metamorphic complex. Polar Urals, Russia. The complex is interpreted as a part of the Early Palaeozoic East European passive margin, subducted, metamorphosed and exhumed during Uralian arc-continent collision. In the Marun-Keu complex, a variety of meta-igneous and metasedimentary rocks documents different evolutionary stages of the northeastern margin of Baltica. Both the oldest, polystage detrital zircon population, which is 570 to 700 Ma in age, and the dominant zircon population in an island arc-type magmatic suite (c. 550 Ma) are related to the Neoproterozoic Timanian orogeny, which resulted in continental growth of northeastern Europe by accretion of juvenile oceanic and island arc material. A distinct magmatic event at c. 490 Ma is documented in zircons from metagranites, a...
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