Abstract Mid-Palaeozoic assembly models for the Arctic Alaska–Chukotka microplate predict the presence of cryptic crustal sutures, the exact locations and deformational histories of which have not been identified in the field. This study presents data on the provenance of polydeformed and metamorphosed strata in the southern Brooks Range Schist Belt and Central Belt of presumed Proterozoic–Devonian depositional age, as well as for the structurally overlying strata, to help elucidate terrane boundaries within the Arctic Alaska–Chukotka microplate and to add new constraints to the palaeogeographical evolution of its constituent parts. The protoliths identified support correlations with metasedimentary strata in the Ruby terrane and Seward Peninsula and suggest a (peri-) Baltican origin in late Neoproterozoic–early Palaeozoic time. Proximity to Laurentia is only evident in what are inferred to be post-early Devonian age strata. By contrast, the North Slope and Apoon terranes originated proximal to Laurentia. The mid-Palaeozoic boundary between these (peri-) Baltican and (peri-) Laurentian terranes once lay between rocks of the Schist/Central belts and those of the Apoon terrane, but is obscured by severe Mesozoic–Cenozoic deformation. Whether this boundary represents a convergent or transform suture, when exactly it formed and how it relates to broader Caledonian convergence in the North Atlantic are still unresolved questions. Supplementary material: Details of the analytical methods together with zircon U-Pb and Lu-Hf isotopic data tables are available at https://doi.org/10.6084/m9.figshare.c.3805696

Abstract The tectonomagmatic evolution of eastern Chukotka, NE Russia, is important for refining the onset of Pacific plate subduction, understanding the development of the Amerasia Basin, and constraining Arctic tectonic reconstructions. Field mapping and strategic sample collection provide relative age constraints on subduction-related continental arc magmatism in eastern Chukotka. Ion microprobe U–Pb zircon ages provide absolute constraints and identify five magmatic episodes ( c. 134, 122, 105, 94 and 85 Ma) separated by three periods of uplift and erosion ( c. 122–105, 94–85 and post-85 Ma). Volcanic rocks in the region are less contaminated than their plutonic equivalents which record greater crustal assimilation. These data, combined with xenocrystic zircons, reflect the self-assimilation of a continental arc during its evolution. Proto-Pacific subduction initiated by c. 121 Ma and arc development occurred over c. 35–50 myr. Crustal growth was simultaneous with regional exhumation and crustal thinning across the Bering Strait region. Ocean–continent subduction in eastern Chukotka ended at c. 85 Ma. The timing of events in the region is roughly synchronous with the inferred opening of the Amerasia Basin. Simultaneous arc magmatism, extension and development of the Amerasia Basin within a back-arc basin setting best explain these coeval tectonic events. Supplementary material: Includes SIMS U–Pb and geochemistry data tables, detailed geological map and geochemical figures which are available at https://doi.org/10.6084/m9.figshare.c.3784565

Abstract The pre-Cenozoic kinematic and tectonic history of the Arctic Alaska Chukotka (AAC) terrane is not well known. The difficulties in assessing the history of the AAC terrane are predominantly due to a lack of comprehensive knowledge about the composition and age of its basement. During the Mesozoic, the AAC terrane was involved in crustal shortening, followed by magmatism and extension with localized high-grade metamorphism and partial melting, all of which obscured its pre-orogenic geological relationships. New zircon geochronology and isotope geochemistry results from Wrangel Island and western Chukotka basement rocks establish and strengthen intra- and inter-terrane lithological and tectonic correlations of the AAC terrane. Zircon U–Pb ages of five granitic and one volcanic sample from greenschist facies rocks on Wrangel Island range between 620 ± 6 and 711 ± 4 Ma, whereas two samples from the migmatitic basement of the Velitkenay massif near the Arctic coast of Chukotka yield 612 ± 7 and 661 ± 11 Ma ages. The age spectrum (0.95–2.0 Ga with a peak at 1.1 Ga and minor 2.5–2.7 Ga) and trace element geochemistry of inherited detrital zircons in a 703 ± 5 Ma granodiorite on Wrangel Island suggests a Grenville–Sveconorwegian provenance for metasedimentary strata in the Wrangel Complex basement and correlates with the detrital zircon spectra of strata from Arctic Alaska and Pearya. Temporal patterns of zircon inheritance and O–Hf isotopes are consistent with Cryogenian–Ediacaran AAC magmatism in a peripheral/external orogenic setting (i.e. a fringing arc on rifted continental margin crust). Supplementary material: Secondary ion mass spectrometry (SIMS) U–Pb zircon geochronology data, SIMS zircon 18 O/ 16 O isotopic data, laser ablation inductively coupled mass spectrometry zircon Lu–Hf isotopic data and zircon cathodoluminescence images are available at https://doi.org/10.6084/m9.figshare.c.3741314

Abstract This paper considers the lithospheric structure and evolution of the wider Barents–Kara Sea region based on the compilation and integration of geophysical and geological data. Regional transects are constructed at both crustal and lithospheric scales based on the available data and a regional three-dimensional model. The transects, which extend onshore and into the deep oceanic basins, are used to link deep and shallow structures and processes, as well as to link offshore and onshore areas. The study area has been affected by numerous orogenic events in the Precambrian–Cambrian (Timanian), Silurian–Devonian (Caledonian), latest Devonian–earliest Carboniferous (Ellesmerian–svalbardian), Carboniferous–Permian (Uralian), Late Triassic (Taimyr, Pai Khoi and Novaya Zemlya) and Palaeogene (Spitsbergen–Eurekan). It has also been affected by at least three episodes of regional-scale magmatism, the so-called large igneous provinces: the Siberian Traps (Permian–Triassic transition), the High Arctic Large Igneous Province (Early Cretaceous) and the North Atlantic (Paleocene–Eocene transition). Additional magmatic events occurred in parts of the study area in Devonian and Late Cretaceous times. Within this geological framework, we integrate basin development with regional tectonic events and summarize the stages in basin evolution. We further discuss the timing, causes and implications of basin evolution. Fault activity is related to regional stress regimes and the reactivation of pre-existing basement structures. Regional uplift/subsidence events are discussed in a source-to-sink context and are related to their regional tectonic and palaeogeographical settings.

Abstract The exhumation and shortening history associated with the Taimyr fold–thrust belt is determined using apatite fission track and balanced cross-section analysis. Eighteen samples from across northern, central and southern Taimyr are used for apatite fission track analysis. These include granite, meta-arenite and sandstone samples with stratigraphic ages ranging from the late Proterozoic to Early Cretaceous. Fission track lengths and central ages are used to model the thermal history of the region and indicate three episodes of cooling in the Early Permian, earliest Triassic and Late Triassic. The thermochronological data are integrated with two balanced regional cross-sections. The regional structural style of deformation reflects a thick-skinned thrust system with 15% shortening (minimum estimate). This is consistent with thickening during early Permian Uralian orogenesis, followed by later heating, uplift and cooling associated with Siberian Trap magmatism and/or Mesozoic transpression.

Abstract To better understand the sediment provenance and exhumation history of Novaya Zemlya’s Mesozoic fold–thrust belt, we apply detrital zircon U–Pb geochronology combined with zircon and apatite fission track analyses to samples from the Precambrian to late Permian siliciclastic successions of the southern and northern islands. The Silurian to early Devonian samples are dominated by zircons (1.14–0.9 Ga) characteristic of the Sveconorwegian Orogen. Zircon fission track ages for individual units are older than their stratigraphic ages and consistent with single-age population distributions. The zircon fission track results document no annealing after deposition and therefore preserve provenance information, which indicates that the source rock(s) of each sample most likely experienced the same thermal event. The results support the erosion and recycling of Sveconorwegian-aged zircon from the Fennoscandian shield during Caledonian orogenesis to the Barents Sea Shelf and Novaya Zemlya. Apatite fission track ages and thermal modelling identify a rapid cooling event at 220–210 Ma, consistent with late Triassic deformation on Novaya Zemlya. Supplemental material: Detrital zircon U–Pb LA-ICP-MS data of samples from Novaya Zemlya, is available at https://doi.org/10.6084/m9.figshare.c.3787364

Abstract Waveform tomography with very large datasets reveals the upper-mantle structure of the Arctic in unprecedented detail. Using tomography jointly with computational petrology, we estimate temperature in the lithosphere–asthenosphere depth range and infer lithospheric structure and evolution. Most of the boundaries of the mantle roots of cratons in the Arctic are coincident with their geological boundaries at the surface. The thick lithospheres of the Greenland and North American cratons are separated by a corridor of thin lithosphere beneath Baffin Bay and through the middle of the Canadian Arctic Archipelago; the southern archipelago is part of the North American Craton. The mantle root of the cratonic block beneath northern Greenland may extend westwards as far as central Ellesmere Island. The Barents and Kara seas show high velocities indicative of thick lithosphere, similar to cratons. The locations of intraplate basaltic volcanism attributed to the High Arctic Large Igneous Province are all on thin, non-cratonic lithosphere. The lithosphere beneath the central part of the Siberian Traps is warmer than elsewhere beneath the Siberian Craton. This observation is consistent with lithospheric erosion associated with the large igneous province volcanism. A corridor of relatively low seismic velocities cuts east–west across central Greenland. This indicates lithospheric thinning, which appears to delineate the track of the Iceland hotspot. Supplementary material: Figures with comparisons of different tomographic models at 50 and 200 km depths are available at https://doi.org/10.6084/m9.figshare.c.3817810

Abstract We use new models of crustal structure and the depth of the lithosphere–asthenosphere boundary to calculate the geopotential energy and its corresponding geopotential stress field for the High Arctic. Palaeostress indicators such as dykes and rifts of known age are used to compare the present day and palaeostress fields. When both stress fields coincide, a minimum age for the configuration of the lithospheric stress field may be defined. We identify three regions in which this is observed. In north Greenland and the eastern Amerasia Basin, the stress field is probably the same as that present during the Late Cretaceous. In western Siberia, the stress field is similar to that in the Triassic. The stress directions on the eastern Russian Arctic Shelf and the Amerasia Basin are similar to that in the Cretaceous. The persistent misfit of the present stress field and Early Cretaceous dyke swarms associated with the High Arctic Large Igneous Province indicates a short-lived transient change in the stress field at the time of dyke emplacement. Most Early Cretaceous rifts in the Amerasia Basin coincide with the stress field, suggesting that dyking and rifting were unrelated. We present new evidence for dykes and a graben structure of Early Cretaceous age on Bennett Island.

Abstract New high spatial resolution secondary ion mass spectrometry (SIMS) U–Pb zircon data from the Sadh gneiss complex and the intruding Marbat granodiorite of the Marbat region, southern Sultanate of Oman, yield Cryogenian magmatic protolith ages for gneisses ranging from c. 850 to 830 Ma. Zircon ages record a c. 815–820 Ma period of deformation and migmatization, followed by intrusion of a hornblende gabbro/diorite and the undeformed Marbat granodiorite at c. 795 Ma. Following break-up and rifting of Rodinia at c. 870 Ma, crustal growth in the Marbat region occurred via arc accretion at c. 850–790 Ma, possibly in the easternmost part of the Mozambique Ocean based on earlier cessation of accretion here compared to the Arabian–Nubian Shield. Similarity of the new zircon geochronology to peaks of detrital zircon ages in the unconformably overlying Ediacaran Marbat sandstone suggests relatively local derivation from uplifted basement for the latter. Supplementary material: Detailed petrographic descriptions and photographs of hand specimens and thin-sections are available at http://www.geolsoc.org.uk/SUP18685 .