The last decade of structural and isotope-age dating studies in Svalbard and East Greenland has provided strong support for the close correlation of these segments of the Caledonide Orogen, as had previously been inferred from stratigraphic evidence. Prior to Tertiary opening of the Norwegian-Greenland Sea, Svalbard's Caledonian terranes were an essential part of the Laurentian margin, as witnessed not only by the Early Palaeozoic depositional environments and fauna, but also by the character of the Palaeoproterozoic basement, the Meso-to Neoproterozoic cover, the evidence of late Grenvillian tectono-thermal activity, Caledonian structural style and timing of movements, Caledonian granitic magmatism and Old Red Sandstone (ORS) deposition.Recently published maps of East Greenland show the hinterland allochthons of central East Greenland to strike out obliquely into the continental shelf. The hypothesis promoted here requires that they continue offshore northwards, extending to the northern edge of the NE Greenland shelf and that most of the Svalbard terranes were northerly continuations of the East Greenland Caledonides. Only along the west coast of central Spitsbergen are 'foreign' terranes exposed that have affinity with Pearya, having been located north of the North Greenland foldbelt, apparently unrelated to Laurentia, prior to Ellesmerian Orogeny,The unambiguous affinity of the Svalbardian and Greenlandian (Laurentian) Caledonides contrasts markedly with the Timanide evolution of northeastern Baltica. It confirms previous interpretations that an important Caledonian suture-zone transgresses northeastwards across the Barents Sea, separating Laurentian domains in the NW from the Timanides of Baltica in the SE. The Timanides of northeastern Europe are truncated by, and terminate in the Barentsian Caledonides of the Barents Shelf.

No abstract

Svalbard is located in the north-west corner of the Barents Sea shelf and the Eurasian Plate, in a key area for interpreting Caledonian and older orogens in the Arctic region. Recent U-Pb dating in the Nordaustlandet Terrane of eastern Svalbard shows this terrane to consist of a Grenville-age basement, overlain by Neoproterozoic to early Palaeozoic platformal sediments, and intruded by Caledonian anatectic granites. Deformation, metamorphism and crustal anatectic magmatism occurred both during the Grenvillian (960-940 Ma) and Caledonian (450-410 Ma) orogenies. This evolution shows great similarities with

No abstract

The basement of the island of Nordaustlandet, northeastern Svalbard, consists of a complex of metasedimentary and metavolcanic rocks, granites and augen gneisses, unconformably overlain by the Neoproterozoic Murchisonfjorden Supergroup. Earlier U-Pb dating of the Laponiafjellet and Kontaktberget granites has shown them to be late Grenvillian, with ages of c. 960 Ma and 940 Ma, respectively. Here, we present conventional U-Pb zircon and monazite data, single zircon Pb-evaporation data and ion microprobe data from the Kapp Hansteen Group and Svartrabbane Formation volcanic and subvolcanic rocks, and from the Fonndalen and Ringåsvatnet augen gneisses of central Nordaustlandet. The combined evidence suggests late Grenvillian magmatic ages of 940–970 Ma for all these rocks, with inherited zircons ranging in age from c. 1200 Ma to 2600 Ma. The investigated rocks vary in chemical composition from andesites to rhyolites and granites, and show generally similar trace and rare earth element patterns, with trace element compositions suggesting a volcanic arc or syn-collisional tectonic setting, and major element compositions suggesting a large sedimentary input to the magmas. Contributions from older crustal material are also supported by Nd isotope data and the presence of inherited zircons.The Grenvillian magmatic rocks thus originated in a series of magmatic events along a continental margin over a time span not longer than 30 Ma. The volcanic rocks were extruded onto folded strata of the Brennevinsfjorden Group–Helvetesflya Formation, which must have been deposited in the time interval 1200–960 Ma. Folding of the metasediments preceded the volcanism, but was synchronous with intrusion of the augen gneiss protolith, and was followed by crustal stabilisation, uplift and erosion. This newly formed Grenvillian crust then served as basement for the deposition of the Neoproterozoic Murchisonfjorden Supergroup. The present outcrop pattern of the Grenvillian rocks is largely the result of large-scale Caledonian folding and doming.

The Nordaustlandet Terrane of NE Svalbard forms an exposed part of the Barentsia microcontinent. Augen gneisses, migmatites, granites and gabbros dominate the scattered outcrops along the northeastern coast of Nordaustlandet, and on the smaller islands to the north and east, as far as Kvitøya. These outcrops probably represent the deepest exposed crustal levels within the folded Caledonian basement of the Nordaustlandet Terrane. In the present study, a variety of rock types have been analysed by different U-Pb dating techniques (conventional, Pb-evaporation and ion microprobe) on zircon, titanite and monazite The major and trace element compositions and Sm-Nd isotope geochemistry of these rocks have also been investigated.The augen gneisses yield U-Pb ages of c. 950 Ma, indicating that they are deformed late Grenvillian granites, similar to the Grenville-age granites and augen gneisses of northwestern and central Nordaustlandet. Migmatites, grey granites, aplitic dykes and a syenite (boulder) yield U-Pb ages mainly falling in the 430–450 Ma range, slightly older than the 410–420 Ma late-tectonic Caledonian granites further west. Both the Grenvillian and Caledonian granites are of crustal anatectic origin, and the Caledonian granites and migmatites may have formed largely by remelting of Grenvillian crust. The ages of the mafic rocks are uncertain, but Sm-Nd data indicate a possible emplacement age of c. 700 Ma for two of the gabbros, suggesting that they may be the result of rift-related magmatism in connection with the opening of the Iapetus Ocean. A few enigmatic inherited zircons of similar late Neoproterozoic age found in younger granites may possibly be related to this event. No evidence for late Neoproterozoic orogenic activity, similar to that in the Timanides of northern Russia, is seen in eastern Svalbard. At this time, eastern Svalbard (Barentsia) was probably part of the Laurentian margin, and probably located far away from northern Baltica.

Ryungenen, G. I. 1995: Grenvillian U-Pb zircon ages from quartz-porphyry and rhyolite clasts in a metaconglomerate at Vimsodden, southwestern Spitsbergen. Polar Research 14(3), [291][292][293][294][295][296][297][298][299][300][301][302] Proterozoic metasupracrustal rocks form a NNW-SSE trending basement zone along the western coast of Spitsbergen. The rocks show complex structures as a result of both Caledonian and Tertiary deformation, and most of the subordinate metaigneous rocks are not suitable for isotopic age determination. Some zircon-bearing rocks were found in the southwestern part of Spitsbergen and an attempt of U-Pb dating was performed.U-Pb dating was carried out on zircon fractions from quartz porphyry and rhyolite clasts in a metaconglomerate unit of the Pyttholmen Formation northwest of Hornsund. southwestern Spitsbergen. The Pyttholmen Formation is considered to be a lateral equivalent of the upper part of the Gulliksenfjellet quartzite and in the same time as the upper part of the SkiUfjellet metavolcanites. Therefore, the obtained ages are applicable to the age of the Skilfjellet igneous activities. Some of the dated samples are strongly schistose and their magmatic origin is difficult to confirm; the interpretation of the isotopic results is not well constrained; however, some explanations are possible which refer to the known geological conditions; an igneous age of siliceous volcanic rocks of ca. 1200 Ma, inherited zircon ages of ca. 2500 Ma and a regional metamorphic age of ca. 930 Ma. The last age belongs to the Grenvillian period and is conformable with the Rb/Sr whole rock age obtained from the garnet-biotite schists of the Isbj~rnhamna Group underlying the Skilfjellet metavolcanites.

No abstract