Vast (about 7 billions km) almost wholly (98%) covered with ice continental mass of East Antarcti... more Vast (about 7 billions km) almost wholly (98%) covered with ice continental mass of East Antarctica is the central fragment of ancient supercontinents of Rodinia and Gondwana. Any information on its geologic structure is of the greatest importance for solving the problems of formation and amalgamation of lithosphere of ancient continents, processes of intraplate activity, denudation and peneplanation of the earth crust and for geodynamic reconstruction. Geologic structure of central part of the East Antarctica is still absolutely unknown due to the thick (up to 4000 m) ice cover, which is the obstacle even for modern drilling technology to sample directly the underlying rocks. The main goal of the study has been to make an attempt in fill up the hiatus in geologic knowledge on the origin of subglacial continental crust of the Antarctica.
We present the results of geostructural, mineralogic–petrographic, geochemical, and U–Pb geochron... more We present the results of geostructural, mineralogic–petrographic, geochemical, and U–Pb geochronological investigations of mafic, intermediate, and felsic igneous rocks from dikes in the Yana–Kolyma gold belt of the Verkhoyansk–Kolyma folded area (northeastern Asia). The dikes of the Vyun deposit and the Shumniy occurrence intruding Mesozoic terrigenous rocks of the Kular–Nera and Polousniy–Debin terranes were examined in detail. The dikes had diverse mineralogical and petrographic compositions including trachybasalts, andesites, trachyandesites, dacites, and granodiorites. The rocks showed significant similarities in distributions of REE, and their concentrations of most HFSEs were close to the intermediate ones between ocean islands basalts and enriched middle ocean ridge basalts. We propose that the subduction that was ongoing during the collision of the Kolyma–Omolon superterrane with Siberia led to melting in the asthenospheric wedge and in the lithosphere, which formed a mixe...
The Late Paleozoic sedimentary basins in the Northern Gemericum evolved gradually in time and spa... more The Late Paleozoic sedimentary basins in the Northern Gemericum evolved gradually in time and space within the collisional tectonic regime of the Western Carpathian Variscan orogenic belt. The detrital zircon age spectra, obtained from the Mississippian, Pennsylvanian and Permian metasediments, have distinctive age distribution patterns that reflect the tectonic setting of the host sediments. An expressive unimodal zircon distribution, with an age peak at 352 Ma, is shown by the basal Mississippian metasediments. These represent a relic of the convergent trench-slope sedimentary basin fill. In comparison, the Pennsylvanian detrital zircon populations display distinct multimodal distributions, with the main age peaks at 351, 450, 565 Ma and smaller peaks at ~2.0 and ~2.7 Ga. This is consistent with derivation of clastic detritus from the collisional suture into the foreland basin. Similarly, the Permian sedimentary formations exhibit the multimodal distribution of zircon ages, with m...
U–Pb (SHRIMP) detrital zircon ages from the Early Paleozoic meta-sedimentary rocks of the Norther... more U–Pb (SHRIMP) detrital zircon ages from the Early Paleozoic meta-sedimentary rocks of the Northern Gemericum Unit (the Smrečinka Formation) were used to characterize their provenance. The aim was to compare and reconcile new analyses with previously published data. The detrital zircon age spectrum demonstrates two prominent populations, the first, Late Neoproterozoic (545–640 Ma) and the second, Paleoproterozoic (1.8–2.1 Ga), with a minor Archean population (2.5–3.4 Ga). The documented zircon ages reflect derivation of the studied metasedimentary rocks from the Cadomian arc, which was located along the West African Craton. The acquired data supports close relations of the Northern Gemericum basement with the Armorican terranes during Neoproterozoic and Ordovician times and also a close palinspastic relation with the other crystalline basements of the Central Western Carpathians. In comparison, the detrital zircons from the Southern Gemericum basement and its Permian envelope indicat...
ABSTRACT In this paper we present new U − Pb zircon age, Sm–Nd isotopic and chemical composition ... more ABSTRACT In this paper we present new U − Pb zircon age, Sm–Nd isotopic and chemical composition data for rocks cropping out in a few isolated nunataks in Wilhelm II Land in East Antarctica, namely Mirny oasis, Mt Brown and Gaussberg volcano, which contains xenogenic crustal material. These outcrops were subjects of geological investigations during the Soviet Antarctic Expedition of 1956–1957. Our data show that this region is underlain by a uniform crust which experienced a high-grade metamorphic event at ca 980 − 920 Ma, co-eval with the Rayner Orogeny in Kemp Land and the northern Prince Charles Mountains. Extensive indications of a ca 500 Ma event in coastal areas (granitoid intrusions in Mirny oasis and inherited zircons found in Gaussberg volcano), together with the lack of indications of this age in Mt Brown, point to a concentration of ca 500 Ma processes (roughly co-eval with the Prydz Orogeny) in the coastal part of Wilhelm II Land and their attenuation inland. We also determined a ca 1480 Ma age for a mafic magmatic protolith in Mt Brown which may be correlated with roughly co-eval orthogneiss in the Bunger Hills area. These observations suggest the conjugate positions of these crustal blocks in the early Mesoproterozoic and argue against a Cambrian suture running between them. In Gaussberg volcano a range of zircon 206Pb/238U ages of ca 320 Ma, ca 500 Ma, ca 980 Ma, and ca 2000–1800 Ma has been determined. The presence of ca 2000–1800 Ma zircons indicates involvement of mid-Palaeoproterozoic rocks in the structure of Wilhelm II Land. This argues for possible conjugation of this region with other East Antarctic blocks experienced the Palaeoproterozoic tectonic evolution and which have been considered to comprise the Mawson palaeocontinent.
The Thala Hills area occupies a key position in Gondwanaland reconstructions near the India–Sri L... more The Thala Hills area occupies a key position in Gondwanaland reconstructions near the India–Sri Lanka–Antarctica junction. We present U–Pb zircon isotopic age determinations from SHRIMP II obtained on four granite gneiss samples. Three high-temperature tectonomagmatic episodes may be distinguished in the study area at c. 980–970, c. 780–720 and c. 545–530 Ma. The c. 980–970 Ma event corresponds to the Rayner Structural Episode that affected East Antarctica, including the Sør Rondane Mountains to the west and Kemp Land to the east. The c. 780–720 Ma episode included two events at approximately 780 Ma (high-grade anatexis) and 720 Ma (syntectonic granitoid emplacement), and was roughly coeval with tectonomagmatic events in Dronning Maud Land of East Antarctica, as well as in other Gondwanaland regions, such as Madagascar, Sri Lanka and eastern Africa. The c. 780–720 Ma episode may be correlated with the East African Orogeny. These correlations argue for a similar geological evolution ...
The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-s... more The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-sedimentary rock complexes, constitutes a record of the polyphase Cambrian–Ordovician continental volcanic arc volcanism. These metavolcanic rocks are characterized by the enrichment in K, Rb, Ba, Th and Ce and Sm relative to Ta, Nb, Hf, Zr, Y and Yb that are the characteristic features for volcanic arc magmatites. The new SHRIMP U–Pb zircon data and compilation of previously published and re-evaluated zircon ages, contribute to a new constrain of the timing of the Cambrian–Ordovician volcanism that occurred between 496 and 447 Ma. The following peaks of the volcanic activity of the Southern Gemericum basement have been recognized: (a) mid-late Furongian at 492 Ma; (b) Tremadocian at 481 Ma; (c) Darriwilian at 464 Ma prolonged to 453 Ma within the early Upper Ordovician. The metavolcanic rocks are characterized by a high zircon inheritance, composed of Ediacaran (650–550 Ma), Tonian–Stenian (1.1–0.9 Ma), and, to a lesser extent, Mesoproterozoic (1.3 Ga), Paleoproterozoic (1.9 Ga) and Archaean assemblages (2.6 Ga). Based on the acquired zircon populations, it could be deduced that Cambrian–Ordovician arc crust was generated by a partial melting of Ediacaran basement in the subduction-related setting, into which old crustal fragments were incorporated. The ascertained zircon inheritances with Meso-, Paleoproterozoic and Archaean cores indicate the similarities with the Saharan Metacraton provenance.
441 The Vostochnotagilskii massif (VTM; also known as Krasnoural’skii) is one of the largest in t... more 441 The Vostochnotagilskii massif (VTM; also known as Krasnoural’skii) is one of the largest in the Middle and North Urals [1]. This massif occurs in the merid ian direction for >300 km (Fig. 1, the southern part of massif) and controls the Serovsko–Maukskii ophiolite complex separating the Tagil and Magnitogorsk paleo island arc zones. The massif is composed of dunite and harzburgite serpentinized to various degrees. Chrysotile serpentinite prevails in the central part intruded by gabbro diabase and granitoid dykes, whereas antigorite serpentinite predominates in the marginal zones. The exocontact zones of dykes are characterized by bimetasomatic zoning with the for mation of vermiculite, chlorite–actinolite, talc, and talc–carbonate rocks. The freshest rock varieties are preserved in the central part of massif. Poor exposure does not provide unambiguous evidence for relation ships between dunite and harzburgite; according to the composition of chrome spinellids, ultramafic rocks form a continuous series [2]. At the same time, transi tional varieties between dunite and harzburgite were not found in the largest Kutuzovskii mine located at the latitude of Krasnoural’sk.
Zircons from charnockite-enderbite rocks (Aker Peaks, Napier Mountains), which we have dated by S... more Zircons from charnockite-enderbite rocks (Aker Peaks, Napier Mountains), which we have dated by SHRIMP-II, were analyzed earlier by conventional multigrain U-Pb ID-TIMS methods (Belyatsky et al., 1990) but gave equivocal ages. This study shows that the optimal way to evaluate geologic events in such rocks is local ion-probe analysis of complex zircons with preliminary study of CL, BSE, REE patterns. Due to this approach we have obtained, for the first time, reliable ages of magmatic crystallization for studied charnockite-enderbites (3620 ± 30 Ma) and the age of the primary enderbite’s protolith (3950 – 3970 Ma). Moreover, in all dated zircons a metamorphic event of 2450– 2480 Ma is clearly recorded that is in agreement with the granulite-facies metamorphism described by many authors. These conclusions coincide well with our Sm-Nd isotope data for these enderbite-charnockite gneisses.
Vast (about 7 billions km) almost wholly (98%) covered with ice continental mass of East Antarcti... more Vast (about 7 billions km) almost wholly (98%) covered with ice continental mass of East Antarctica is the central fragment of ancient supercontinents of Rodinia and Gondwana. Any information on its geologic structure is of the greatest importance for solving the problems of formation and amalgamation of lithosphere of ancient continents, processes of intraplate activity, denudation and peneplanation of the earth crust and for geodynamic reconstruction. Geologic structure of central part of the East Antarctica is still absolutely unknown due to the thick (up to 4000 m) ice cover, which is the obstacle even for modern drilling technology to sample directly the underlying rocks. The main goal of the study has been to make an attempt in fill up the hiatus in geologic knowledge on the origin of subglacial continental crust of the Antarctica.
We present the results of geostructural, mineralogic–petrographic, geochemical, and U–Pb geochron... more We present the results of geostructural, mineralogic–petrographic, geochemical, and U–Pb geochronological investigations of mafic, intermediate, and felsic igneous rocks from dikes in the Yana–Kolyma gold belt of the Verkhoyansk–Kolyma folded area (northeastern Asia). The dikes of the Vyun deposit and the Shumniy occurrence intruding Mesozoic terrigenous rocks of the Kular–Nera and Polousniy–Debin terranes were examined in detail. The dikes had diverse mineralogical and petrographic compositions including trachybasalts, andesites, trachyandesites, dacites, and granodiorites. The rocks showed significant similarities in distributions of REE, and their concentrations of most HFSEs were close to the intermediate ones between ocean islands basalts and enriched middle ocean ridge basalts. We propose that the subduction that was ongoing during the collision of the Kolyma–Omolon superterrane with Siberia led to melting in the asthenospheric wedge and in the lithosphere, which formed a mixe...
The Late Paleozoic sedimentary basins in the Northern Gemericum evolved gradually in time and spa... more The Late Paleozoic sedimentary basins in the Northern Gemericum evolved gradually in time and space within the collisional tectonic regime of the Western Carpathian Variscan orogenic belt. The detrital zircon age spectra, obtained from the Mississippian, Pennsylvanian and Permian metasediments, have distinctive age distribution patterns that reflect the tectonic setting of the host sediments. An expressive unimodal zircon distribution, with an age peak at 352 Ma, is shown by the basal Mississippian metasediments. These represent a relic of the convergent trench-slope sedimentary basin fill. In comparison, the Pennsylvanian detrital zircon populations display distinct multimodal distributions, with the main age peaks at 351, 450, 565 Ma and smaller peaks at ~2.0 and ~2.7 Ga. This is consistent with derivation of clastic detritus from the collisional suture into the foreland basin. Similarly, the Permian sedimentary formations exhibit the multimodal distribution of zircon ages, with m...
U–Pb (SHRIMP) detrital zircon ages from the Early Paleozoic meta-sedimentary rocks of the Norther... more U–Pb (SHRIMP) detrital zircon ages from the Early Paleozoic meta-sedimentary rocks of the Northern Gemericum Unit (the Smrečinka Formation) were used to characterize their provenance. The aim was to compare and reconcile new analyses with previously published data. The detrital zircon age spectrum demonstrates two prominent populations, the first, Late Neoproterozoic (545–640 Ma) and the second, Paleoproterozoic (1.8–2.1 Ga), with a minor Archean population (2.5–3.4 Ga). The documented zircon ages reflect derivation of the studied metasedimentary rocks from the Cadomian arc, which was located along the West African Craton. The acquired data supports close relations of the Northern Gemericum basement with the Armorican terranes during Neoproterozoic and Ordovician times and also a close palinspastic relation with the other crystalline basements of the Central Western Carpathians. In comparison, the detrital zircons from the Southern Gemericum basement and its Permian envelope indicat...
ABSTRACT In this paper we present new U − Pb zircon age, Sm–Nd isotopic and chemical composition ... more ABSTRACT In this paper we present new U − Pb zircon age, Sm–Nd isotopic and chemical composition data for rocks cropping out in a few isolated nunataks in Wilhelm II Land in East Antarctica, namely Mirny oasis, Mt Brown and Gaussberg volcano, which contains xenogenic crustal material. These outcrops were subjects of geological investigations during the Soviet Antarctic Expedition of 1956–1957. Our data show that this region is underlain by a uniform crust which experienced a high-grade metamorphic event at ca 980 − 920 Ma, co-eval with the Rayner Orogeny in Kemp Land and the northern Prince Charles Mountains. Extensive indications of a ca 500 Ma event in coastal areas (granitoid intrusions in Mirny oasis and inherited zircons found in Gaussberg volcano), together with the lack of indications of this age in Mt Brown, point to a concentration of ca 500 Ma processes (roughly co-eval with the Prydz Orogeny) in the coastal part of Wilhelm II Land and their attenuation inland. We also determined a ca 1480 Ma age for a mafic magmatic protolith in Mt Brown which may be correlated with roughly co-eval orthogneiss in the Bunger Hills area. These observations suggest the conjugate positions of these crustal blocks in the early Mesoproterozoic and argue against a Cambrian suture running between them. In Gaussberg volcano a range of zircon 206Pb/238U ages of ca 320 Ma, ca 500 Ma, ca 980 Ma, and ca 2000–1800 Ma has been determined. The presence of ca 2000–1800 Ma zircons indicates involvement of mid-Palaeoproterozoic rocks in the structure of Wilhelm II Land. This argues for possible conjugation of this region with other East Antarctic blocks experienced the Palaeoproterozoic tectonic evolution and which have been considered to comprise the Mawson palaeocontinent.
The Thala Hills area occupies a key position in Gondwanaland reconstructions near the India–Sri L... more The Thala Hills area occupies a key position in Gondwanaland reconstructions near the India–Sri Lanka–Antarctica junction. We present U–Pb zircon isotopic age determinations from SHRIMP II obtained on four granite gneiss samples. Three high-temperature tectonomagmatic episodes may be distinguished in the study area at c. 980–970, c. 780–720 and c. 545–530 Ma. The c. 980–970 Ma event corresponds to the Rayner Structural Episode that affected East Antarctica, including the Sør Rondane Mountains to the west and Kemp Land to the east. The c. 780–720 Ma episode included two events at approximately 780 Ma (high-grade anatexis) and 720 Ma (syntectonic granitoid emplacement), and was roughly coeval with tectonomagmatic events in Dronning Maud Land of East Antarctica, as well as in other Gondwanaland regions, such as Madagascar, Sri Lanka and eastern Africa. The c. 780–720 Ma episode may be correlated with the East African Orogeny. These correlations argue for a similar geological evolution ...
The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-s... more The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-sedimentary rock complexes, constitutes a record of the polyphase Cambrian–Ordovician continental volcanic arc volcanism. These metavolcanic rocks are characterized by the enrichment in K, Rb, Ba, Th and Ce and Sm relative to Ta, Nb, Hf, Zr, Y and Yb that are the characteristic features for volcanic arc magmatites. The new SHRIMP U–Pb zircon data and compilation of previously published and re-evaluated zircon ages, contribute to a new constrain of the timing of the Cambrian–Ordovician volcanism that occurred between 496 and 447 Ma. The following peaks of the volcanic activity of the Southern Gemericum basement have been recognized: (a) mid-late Furongian at 492 Ma; (b) Tremadocian at 481 Ma; (c) Darriwilian at 464 Ma prolonged to 453 Ma within the early Upper Ordovician. The metavolcanic rocks are characterized by a high zircon inheritance, composed of Ediacaran (650–550 Ma), Tonian–Stenian (1.1–0.9 Ma), and, to a lesser extent, Mesoproterozoic (1.3 Ga), Paleoproterozoic (1.9 Ga) and Archaean assemblages (2.6 Ga). Based on the acquired zircon populations, it could be deduced that Cambrian–Ordovician arc crust was generated by a partial melting of Ediacaran basement in the subduction-related setting, into which old crustal fragments were incorporated. The ascertained zircon inheritances with Meso-, Paleoproterozoic and Archaean cores indicate the similarities with the Saharan Metacraton provenance.
441 The Vostochnotagilskii massif (VTM; also known as Krasnoural’skii) is one of the largest in t... more 441 The Vostochnotagilskii massif (VTM; also known as Krasnoural’skii) is one of the largest in the Middle and North Urals [1]. This massif occurs in the merid ian direction for >300 km (Fig. 1, the southern part of massif) and controls the Serovsko–Maukskii ophiolite complex separating the Tagil and Magnitogorsk paleo island arc zones. The massif is composed of dunite and harzburgite serpentinized to various degrees. Chrysotile serpentinite prevails in the central part intruded by gabbro diabase and granitoid dykes, whereas antigorite serpentinite predominates in the marginal zones. The exocontact zones of dykes are characterized by bimetasomatic zoning with the for mation of vermiculite, chlorite–actinolite, talc, and talc–carbonate rocks. The freshest rock varieties are preserved in the central part of massif. Poor exposure does not provide unambiguous evidence for relation ships between dunite and harzburgite; according to the composition of chrome spinellids, ultramafic rocks form a continuous series [2]. At the same time, transi tional varieties between dunite and harzburgite were not found in the largest Kutuzovskii mine located at the latitude of Krasnoural’sk.
Zircons from charnockite-enderbite rocks (Aker Peaks, Napier Mountains), which we have dated by S... more Zircons from charnockite-enderbite rocks (Aker Peaks, Napier Mountains), which we have dated by SHRIMP-II, were analyzed earlier by conventional multigrain U-Pb ID-TIMS methods (Belyatsky et al., 1990) but gave equivocal ages. This study shows that the optimal way to evaluate geologic events in such rocks is local ion-probe analysis of complex zircons with preliminary study of CL, BSE, REE patterns. Due to this approach we have obtained, for the first time, reliable ages of magmatic crystallization for studied charnockite-enderbites (3620 ± 30 Ma) and the age of the primary enderbite’s protolith (3950 – 3970 Ma). Moreover, in all dated zircons a metamorphic event of 2450– 2480 Ma is clearly recorded that is in agreement with the granulite-facies metamorphism described by many authors. These conclusions coincide well with our Sm-Nd isotope data for these enderbite-charnockite gneisses.
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Papers by Nickolay Rodionov