| 1. |
|
|
| 2. |
- Bogolepova, Olga K., et al.
(författare)
-
The Ordovician of the Severnaya Zemlya Archipelago, Russia
- 2006
-
Ingår i: Newsletters on stratigraphy. - : Schweizerbart. - 0078-0421. ; 42:1, s. 21-41
-
Tidskriftsartikel (refereegranskat)abstract
- The Ordovician strata belonging to the North Kara Basin are well exposed in the Severnaya Zemlya Archipelago. They are dominated by shallow marine sedimentation. Based on faunal evidence, the North Kara Terrane was located at tropical latitudes. Macro- and microfossil assemblages from Severnaya Zemlya contain elements typical of both Siberian and Baltic biotic provinces. An increasing number of taxa common to Laurentia is consistent with the closure of the Iapetus and the convergence between Baltica, Siberia, Laurentia and the North Kara Terrane positioned between them. Short descriptions of the main lithological, faunal features and ages of each stratigraphic unit are given.
|
|
| 3. |
- Gottlieb, Erik S., et al.
(författare)
-
Neoproterozoic basement history of Wrangel Island and Arctic Chukotka : integrated insights from zircon U–Pb, O and Hf isotopic studies
- 2018
-
Ingår i: Geological Society Special Publication. - 0305-8719 .- 2041-4927. ; 460:1
-
Tidskriftsartikel (refereegranskat)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).
|
|
| 4. |
- Hoiland, Carl W., et al.
(författare)
-
Detrital zircon U–Pb geochronology and Hf isotope geochemistry of metasedimentary strata in the southern Brooks Range : constraints on Neoproterozoic–Cretaceous evolution of Arctic Alaska
- 2018
-
Ingår i: Geological Society Special Publication. - 0305-8719 .- 2041-4927. ; 460, s. 121-158
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Hoiland, Carl W., et al.
(författare)
-
Greenschist Facies Metamorphic Zircon Overgrowths as a Constraint on Exhumation of the Brooks Range Metamorphic Core, Alaska
- 2018
-
Ingår i: Tectonics. - 0278-7407 .- 1944-9194. ; 37:10, s. 3429-3455
-
Tidskriftsartikel (refereegranskat)abstract
- Like many other mountain belts, the metamorphic core or hinterland of the Brooks Range fold and thrust belt in Arctic Alaska is characterized by multiply deformed and polymetamorphosed rocks whose histories have been challenging to decipher and thus difficult to relate to the supracrustal history of the orogen. The multiple greenschist and blueschist facies metamorphic events have been particularly difficult to resolve. This study provides petrologic context for recently identified low-temperature metamorphic zircon overgrowths at two localities across some 200km of orogenic strike that offer a unique and precise constraint on the timing of events recorded in the Brooks Range hinterland. In consideration of microstructural context, graphite thermometry, metamorphic mineral inclusions, and zircon trace element and Lu-Hf-isotope data, metamorphic zircon growth at 1145Ma in the southern Brooks Range is interpreted to coincide with greenschist facies metamorphism, most probably linked to decompression and/or increased temperatures within the orogenic core. Their age coincides with a proposed pulse of extension within a >600-km shear zone along the southern flank of the Brooks Range and a regional flare-up in magmatism and pronounced subsidence within hinterland depocenters (Yukon-Koyukuk Basin). These regional events are consistent with subduction retreat/rollback in mid-Cretaceous time. This study adds to a growing body of literature demonstrating the importance of searching for and characterizing metamorphic zircon growth in low- to medium-grade metamorphic terranes to provide better constraints on otherwise cryptic tectonic events. Plain Language Summary Rocks within mountain belts typically contain metamorphic minerals and textures that grew and developed in response to heating, burial, and deformation. In order to understand the evolution of mountains and the plate tectonic interactions that formed them, it is important to be able to determine when those metamorphic minerals and textures grew. The minerals best suited to directly dating tectonic events typically only grow at high temperatures (like >550 degrees C), whereas minerals that grow at lower temperatures are often easily disturbed during subsequent heating or tectonic events, rendering their ages suspect. In our study of the Brooks Range mountain belt in northern Alaska, we characterize low-temperature overgrowths on older zircon crystals that can provide excellent ages using the U-Pb radioactive decay scheme because of their closed system behavior with no loss of daughter products. In the case of the Brooks Range, these zircon overgrowths appear to have formed as enclosing rocks were uplifted toward the surface of the Earth. Their uplift coincided with formation of deep water marine basins and enhanced volcanic activity, which we interpret as due to southward rollback of the subduction zone beneath Alaska beginning similar to 115 million years ago.
|
|
| 6. |
- Ledneva, G. V., et al.
(författare)
-
Late Triassic siliceous-volcano-terrigenous deposits of the Chukchi Peninsula : composition of igneous rocks, U-Pb age of zircons, and geodynamic interpretations
- 2016
-
Ingår i: Russian Geology and Geophysics. - : GeoScienceWorld. - 1068-7971 .- 1878-030X. ; 57:8, s. 1119-1134
-
Tidskriftsartikel (refereegranskat)abstract
- Study of Late Triassic volcanic, subvolcanic, and volcanosedimentary rocks of the Chukchi Peninsula (Vel'may terrane) has shown their different geochemical types. Basalts, dolerites, and tuffs of the lower-middle strata of the Upper Triassic section bear evidence for their formation in suprasubductional geodynamic setting. Basalts and dolerites of the upper strata of this section correspond in composition to within-plate rocks and are similar to Middle-Late Triassic oceanic-plateau basalts and dolerites. U-Pb dating of magmatic zircons from tuffs of the lower-middle strata and from dolerites of the upper strata shows the almost synchronous magmatic activity in the suprasubductional (206 +/- 5 Ma) and within-plate (212 +/- 4 Ma) geodynamic settings. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS.
|
|
| 7. |
- Ledneva, Galina V., et al.
(författare)
-
Permo"Triassic hypabyssal mafic intrusions and associated tholeiitic basalts of the Kolyuchinskaya Bay, Chukotka (NE Russia) : Links to the Siberian LIP
- 2011
-
Ingår i: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120 .- 1878-5786. ; 40:3, s. 737-745
-
Tidskriftsartikel (refereegranskat)abstract
- In order to test tectonic hypotheses regarding the evolution of the Arctic Alaska-Chukotka microplate prior to the opening of the Amerasian basin, we investigated rocks exposed near Kolyuchinskaya Bay, eastern Chukotka. Hypabyssal mafic rocks and associated basaltic flows enclose terrigenous sediments, minor cherts and limestones in pillow interstices. The hypabyssal mafic rock yields a U-Pb zircon age of 252 +/- 4 Ma and indicates intrusion of basic magma at the Permo-Triassic boundary, contemporaneous with voluminous magmatism of the Siberian large igneous province (LIP). The lava flows and hypabyssal mafic rocks of the Kolyuchinskaya Bay region have trace elements, Sm-Nd and Rb-Sr isotope compositions identical to the tholeiitic flood basalts of the main plateau stage of the Siberian LIP, but differ from the latter in the major-element variations. We conclude that compositional variations in the hypabyssal rocks studied reflect their generation in an extensional environment that might be related to the Siberian super-plume activity at the time. Although the genetic and temporal links between intrusive mafic rocks and lavas are not well proved, compositional variations of the eruptive rocks still indicate their generation in an extensional environment.
|
|
| 8. |
- Miller, E. L., et al.
(författare)
-
Stratigraphy and U-Pb detrital zircon geochronology of Wrangel Island, Russia : Implications for Arctic paleogeography
- 2010
-
Ingår i: American Association of Petroleum Geologists Bulletin. - : American Association of Petroleum Geologists AAPG/Datapages. - 0149-1423 .- 1558-9153. ; 94:5, s. 665-692
-
Tidskriftsartikel (refereegranskat)abstract
- Wrangel Island represents a small but unique exposure of Neoproterozoic basement and its upper Paleozoic and Mesozoic cover within the mostly unexplored East Siberian Shelf. Its geology is critical for testing the continuity of stratigraphic units and structures across the Chukchi Sea from Alaska to Arctic Russia, for evaluating the hydrocarbon potential of this offshore region, and for constraining paleogeography and plate reconstructions of the Arctic. Upper Paleozoic platform carbonates and shales on Wrangel likely match those of the Chukchi Shelf and adjacent North Slope of Alaska (e.g., Sherwood et al., 2002), but Triassic basinal turbidites contrast with Alaska's thin shelfal units. Detrital zircon suites from upper Paleozoic strata on Wrangel reveal that local basement-derived detritus (similar to 500-800 Ma) decreases up section, replaced by 900-2000-Ma zircon populations compatible with a Baltic shield provenance. Cambrian-Ordovician-Silurian zircons (similar to 420-490 Ma) are present in lesser abundance in most samples and are inferred to have been derived from the Arctic part of the Caledonide belt. Triassic detrital zircon suites contrast with those from underlying strata: Precambrian zircons have less of an age range (1700-2000 Ma), and Devonian and younger (<400 Ma) zircons are much more abundant. This change reflects breakup of the carbonate platform during Permian-Triassic rifting, with zircon age populations in Triassic strata compatible with sediment sources in the Urals, Taimyr, and Siberia. Detrital zircon data suggest that Wrangel Island, Chukotka, and northern Alaska (the Arctic Alaska-Chukotka microplate) restore against the Lomonosov Ridge upon closure of the Amerasia Basin and to the edge of the Barents Shelf after closing the Eurasia Basin. The detrital zircon data thus suggest that the Barents Shelf lays close to the paleo-Pacific margin in the early Mesozoic and that subduction-driven tectonics may have been a greater factor in the evolution of the Amerasia Basin of the Arctic than previously suspected.
|
|
| 9. |
- Morris, George A., et al.
(författare)
-
Orogenic paleofluid flow recorded by discordant detrital zircons in the Caledonian foreland basin of northern Greenland
- 2015
-
Ingår i: Lithosphere. - 1941-8264 .- 1947-4253. ; 7:2, s. 138-143
-
Tidskriftsartikel (refereegranskat)abstract
- Concordant detrital zircon dates from Neoproterozoic to Paleozoic continental slope and trough deposits in northern Greenland indicate Late Archean and Paleoproterozoic sediment sources. Significant numbers of dates are, however, discordant and, together with a few apparently concordant dates, give ages younger than the depositional ages of overlying fossiliferous sediments. The discordance pattern implies partial or total radiogenic-Pb loss during the Middle Devonian, possibly facilitated by postdepositional fluid movement. Such timing of radiogenic-Pb loss is supported by results from a novel modeling method, which indicate that the greatest statistical similarity between concordant and discordant detrital populations occurs when Pb loss is constrained to the interval of 380-390 Ma, i.e., long after deposition. This radiogenic-Pb loss event is interpreted to reflect fluid flow associated with Caledonian orogenic uplift to the east.
|
|
| 10. |
- O’Brien, Timothy M., et al.
(författare)
-
Provenance, U-Pb detrital zircon geochronology, Hf isotopic analyses, and Cr-spinel geochemistry of the northeast Yukon-Koyukuk Basin : Implications for interior basin development and sedimentation in Alaska
- 2018
-
Ingår i: Geological Society of America Bulletin. - 0016-7606 .- 1943-2674. ; 130:5-6, s. 825-847
-
Tidskriftsartikel (refereegranskat)abstract
- The Yukon-Koyukuk Basin is a large depression that covers ∼118,000 km2 in western interior Alaska and is divided into two subbasins by a volcanic arc assemblage. Interpretations of the depositional setting of the northern Kobuk Koyukuk subbasin vary from a syncollisional forearc basin to a postorogenic successor basin formed by lithospheric extension. New results from sandstones and conglomerates collected from the Kobuk Koyukuk subbasin provide evidence for the timing of basin development, insight into the provenance of coarse siliciclastic sediments, and understanding of the nature of Cretaceous paleogeography and paleodrainage of Arctic Alaska.Early sedimentary rocks of the Kobuk Koyukuk subbasin contain abundant mafic to ultramafic volcanic and plutonic lithic fragments and mafic heavy minerals (e.g., spinel, clinopyroxene, and amphibole). They also contain abundant Middle Triassic to early Late Jurassic zircons (240−160 Ma; peak maximum ca. 200 Ma) that yield highly juvenile Hf isotopic compositions. Geochemistry of chromium spinels (Cr# = 0.17−0.86) suggests crystallization in an immature arc setting that likely developed over mid-ocean-ridge basalt−type crust. These early sediments originated from the mafic and ultramafic rocks of the Angayucham terrane, which was once much more extensive. These results suggest that the Angayucham terrane consists of an obducted Middle Triassic to early Late Jurassic oceanic arc complex that was coeval with oceanic- to continental-margin mafic arc magmatism in the Canadian Cordillera.Our generalized stratigraphy, along with U-Pb ages and Lu-Hf isotope analyses of zircons from sedimentary rocks of the Kobuk Koyukuk subbasin, reflects the tectonic and/or erosional unroofing of the adjacent southern Brooks Range and Ruby terrane. U-Pb ages of detrital zircons collected from the stratigraphically lowest mafic- to ultramafic-rich strata yield maximum depositional ages (107 Ma) that reflect initial erosion of the structurally highest Angayucham terrane and initiation of basin formation and deposition in the late Early Cretaceous. Continued uplift and erosion exposed structurally deeper metamorphic rocks, as revealed by incorporation of low-grade phyllites and eventually higher-grade metamorphic schistose lithic detritus and intermediate-composition (e.g., biotite) to metamorphic (e.g., chloritoid and xenotime) heavy mineral suites into the basin sediments. Differences in detrital zircon signatures between similar-age strata in the Colville foreland basin to the north of the Brooks Range and the Kobuk Koyukuk subbasin indicate that the sediments within the two basins were derived from two different sources, and the Brooks Range orogen acted as a drainage divide during late Early Cretaceous deposition.
|
|
| 11. |
- Pease, Victoria L., et al.
(författare)
-
The New Siberian Islands and evidence for the continuation of the Uralides, Arctic Russia
- 2015
-
Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 172:1, s. 1-4
-
Tidskriftsartikel (refereegranskat)abstract
- U–Pb detrital zircon results from New Siberian Islands sandstones illuminate the long-lived controversy regarding the continuation of the Uralian orogen into the Arctic region. A dominant age peak of c. 285 Ma from Permian sandstone requires proximal derivation from Taimyr’s Carboniferous–Permian granites, thought to reflect syn- to post-tectonic Uralian magmatism. The provenance of Devonian sandstone has Baltica affinities. The data record a dramatic change in provenance between Devonian and Permian time, from Baltica to a mixed Baltica + Uralian source. Our results confirm that the Uralian foreland basin extended from Taimyr to the New Siberian Islands.
|
|
| 12. |
- Robinson, Frank A., et al.
(författare)
-
A discussion on the tectonic implications of Ediacaran late‐ to post‐orogenic A‐type granite in the northeastern Arabian Shield, Saudi Arabia
- 2017
-
Ingår i: Tectonics. - 0278-7407 .- 1944-9194. ; 36:3, s. 582-600
-
Tidskriftsartikel (refereegranskat)abstract
- The transition from late‐orogenic to post‐orogenic magmatism following major orogenic episodes such as the Neoproterozoic to Cambrian East African Orogen (EAO) is an important, yet not well‐understood geological event marking the cessation of subduction‐controlled magmatism between buoyant lithospheric fragments. Forming the northern part of the EAO in the Arabian‐Nubian Shield are three granitic suites that successively intruded the same northeastern area and post‐date the ~640 Ma major orogenic episode: (1) 620–600 Ma alkali feldspar (hypersolvous) granite with alkaline/ferroan/A‐type geochemistry, (2) 599 Ma granite cumulates (some garnet‐bearing) with calc‐alkaline/magnesian affinities, and (3) 584–566 Ma alkali feldspar (hypersolvous) granite (aegirine‐bearing) with a distinctive peralkaline/ferroan/A‐type signature. Combining whole‐rock geochemistry from the southern and northern Arabian Shield, suites 1 and 2 are suggested to be products of late‐orogenic slab tear/rollback inducing asthenospheric mantle injection and lower crustal melting/fractionation toward A‐type/ferroan geochemistry. Suite 3, however, is suggested to be produced by post‐orogenic lithospheric delamination, which replaced the older mantle with new asthenospheric (rare earth element‐enriched) mantle that ultimately becomes the thermal boundary layer of the new lithosphere. Major shear zones, such as the 620–540 Ma Najd Fault System (NFS), are some of the last tectonic events recorded across the Arabian Shield. Data presented here suggest that the NFS is directly related to the late‐orogenic (620–600 Ma) slab tear/rollback in the northeastern Shield as it met with opposing subduction polarity in the southern Shield. Furthermore, this study infers that east and west Gondwana amalgamation interacted with opposing convergence reflected by the NFS.
|
|
| 13. |
- Scott, R., et al.
(författare)
-
Offset and curvature of the Novaya Zemlya fold-and-thrust belt, Arctic Russia
- 2010
-
Ingår i: The Petroleum Geology Conference series. - London : Geological Society. ; 7, s. 591-619
-
Tidskriftsartikel (refereegranskat)abstract
- The Eastern Barents, Kara, Laptev, East Siberian seas and the western Chukchi Sea occupy a large part of the Eurasian Arctic epicontinental shelf in the Russian Arctic. Recent studies have shown that this huge region consists of over 40 sedimentary basins of variable age and genesis which are thought to bear significant undiscovered hydrocarbon resources. Important tectonic events controlling the structure and petroleum geology of the basins are the Caledonian collision and orogeny followed by Late Devonian to Early Carboniferous rifting, Late Palaeozoic Baltica–Siberia collision and Uralian orogeny, Triassic and Early Jurassic rifting, Late Jurassic to Early Cretaceous Canada Basin opening accompanied by closure of the South Anyui Ocean, the Late Mesozoic Verkhoyansk–Brookian orogeny and Cenozoic opening of the Eurasia Oceanic Basin. The majority of the sedimentary basins were formed and developed in a rift and post-rift setting and later modified through a series of structural inversions. Using available regional seismic lines correlated with borehole data, onshore geology in areas with no exploration drilling, and recent Arctic-wide magnetic, bathymetry and gravity grids, we provide more confident characterization of the regional structural elements of the Russian Arctic shelf, and constrain the timing of basin formation, structural styles, lithostratigraphy and possible hydrocarbon systems and petroleum play elements in frontier areas.
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
- Spencer, C. J., et al.
(författare)
-
Crustal reworking and orogenic styles inferred from zircon Hf isotopes : Proterozoic examples from the North Atlantic region
- 2019
-
Ingår i: Geoscience Frontiers. - : Elsevier BV. - 1674-9871. ; 10:2, s. 417-424
-
Tidskriftsartikel (refereegranskat)abstract
- Zircon Hf evolutionary patterns are powerful tools to investiage magma petrogenesis and crustal evolution. The Hf-176/Hf-177 isotopic signature of a rock is particularly informative and can be used to derive an estimation of the time when mantle extraction and diagnose closed system reworking where successive samples through time define an Hf evolution array dependant on the source Lu/Hf ratio. However, many magmatic events require new mantle addition as the thermal impetus for melting pre-existing crust. In this situation, rather than simply reflecting reworking, the isotopic signature indicates mixing with contributions from both reworked crust and new radiogenic input. Different geodynamic settings have different propensities for either reworking or addition of new mantle-derived magma. Hence, Hf-time trends carry within them a record, albeit cryptic, of the evolving geodynamic environment as different tectonic configurations recycle and add new crust at different rates, magnitudes, and from different sources. As an example of the difference in apparent Hf evolution slopes, we present Hf-time compilations from three geographically distinct Meso-to Neoproterozoic orogenic belts in the North Atlantic Region whose geodynamic configurations remain a subject of debate. We use the epsilon Hf/Ma trajectory to assist in understanding their evolution. The epsilon Hf/Ma trajectory of the Sveconorwegian Orogen corresponds to a Lu-176/Hf-177 ratio of 0.012, which implies a process driven primarily by reworking of preexisting crust that is balanced with input from the depleted mantle resulting in a relatively shallow epsilon Hf/Ma slope. The Valhalla Orogen reveals a similar comparatively shallow epsilon Hf/Ma path. In stark contrast to these patterns is the steep epsilon Hf/Ma trajectory of the Grenville Orogen that requires a mixing process involving a greater contribution of old crust of at least similar to 1.8 Ga age. The degree of reworking required to produce the epsilon Hf/Ma trend of the Grenville Orogen is consistent with a continentecontinent collisional orogeny whereas both Sveconorwegian and Valhalla orogens appear more consistent with accretionary margins.
|
|
