Andrei V. Prokopiev

The paleo–Lena River—200 m.y. of transcontinental zircon transport in Siberia

An immense wedge of Carboniferous to Jurassic siliciclastic strata accumulated on the Verkhoyansk passive margin of the Siberian craton. U-Pb ages of detrital zircons from Pennsylvanian to Middle Jurassic sandstones are remarkably consistent and show a systematic change in the proportion of age populations. Most zircons originated from the southern margin of Siberia, which was tectonically active in the Paleozoic and early Mesozoic, and were transported to the Verkhoyansk margin by a major transcontinental river system that existed for ~200 m.y., the paleo–Lena River. Specific sources are the Angara-Vitim batholith of Transbaikalia (315 and 291–288 Ma age peaks), plutons of the Altay-Sayan region of the Central Asia fold belt (494–482 Ma), Proterozoic granitoids of northern Transbaikalia and the East Sayan Range (1888–1832 Ma), and minor contributions from the Siberian Platform and Aldan Shield (2900–2300 Ma). The paleo–Lena River met its demise when the Verkhoy-ansk margin was deformed in the Late Jurassic and Cretaceous, and sediment was diverted north to the Arctic Ocean. Thus, the life span of major transcontinental drainage systems can be comparable to that of the plate boundaries that surround them.

Cretaceous frontal thrusts of the Verkhoyansk fold belt, eastern Siberia

Cretaceous thrust structures are found along the front of the Verkhoyansk miogeoclinal fold belt along the eastern boundary of the Siberian platform in northeast Asia. The Verkhoyansk thrust front is subdivided into a number of segments, each of which has its own thrust system geometry. Balanced cross sections have been constructed for each segment on the basis of the structural study of surface geology and available seismic and drilling data. Distinctions between the segments are also expressed in gravity anomalies and modern topography. Analysis of vitrinite reflectance shows that folding of the Verkhoyansk thrust front was initiated during sedimentation as early as in the Late Jurassic. This period marks the beginning of the collision between the Siberian continent and the Kolyma-Omolon superterrane, now located 500 km to the east of the Verkhoyansk thrust front. Deformation of the thrust front ended by the late Late Cretaceous; erosion of the frontal anticlines began in the early Late Cretaceous. The frontal thrust structures formed in the Late Cretaceous were rejuvenated during a middle to late Pleistocene reactivation, which produced the modern mountain topography. The least amount of erosion of the Verkhoyansk thrust front, 840 m, is observed in its central part, in the Kuranakh segment. To the north and south the erosion increases to 1500 m and 2100 m, respectively. The general configuration of the Verkhoyansk fold belt and its frontal structures are defined by the geometry of Devonian rift-related structures on the eastern Siberian platform and the principal direction, approximately east–west, of Late Cretaceous compressional stresses.

Detrital zircon ages and provenance of the Upper Paleozoic successions of Kotel’ny Island (New Siberian Islands archipelago)

Plate-tectonic models for the Paleozoic evolution of the Arctic are numerous and diverse. Our detrital zircon provenance study of Upper Paleozoic sandstones from Kotel’ny Island (New Siberian Island archipelago) provides new data on the provenance of clastic sediments and crustal affinity of the New Siberian Islands. Upper Devonian−Lower Carboniferous deposits yield detrital zircon populations that are consistent with the age of magmatic and metamorphic rocks within the Grenvillian-Sveconorwegian, Timanian, and Caledonian orogenic belts, but not with the Siberian craton. The Kolmogorov-Smirnov test reveals a strong similarity between detrital zircon populations within Devonian−Permian clastics of the New Siberian Islands, Wrangel Island (and possibly Chukotka), and the Severnaya Zemlya Archipelago. These results suggest that the New Siberian Islands, along with Wrangel Island and the Severnaya Zemlya Archipelago, were located along the northern margin of Laurentia-Baltica in the Late Devonian−Mississippian and possibly made up a single tectonic block. Detrital zircon populations from the Permian clastics record a dramatic shift to a Uralian provenance. The data and results presented here provide vital information to aid Paleozoic tectonic reconstructions of the Arctic region prior to opening of the Mesozoic oceanic basins.

U-Pb SHRIMP Ages of Granitoides from the Main Batholith Belt (North East Asia)*

U-Pb SHRIMP-dating of zircons from twenty five intrusions representative of the Main granitoid batholith belt and associated dike swarms (Yano-Kolyma gold bearing province, North East of Asia) are mostly ∼150 ± 3 Ma (Kimmeridgian-Tithonian). Two less widespread impulses of magmatism dated at 160–155 Ma and 146–143 Ma representing the full range of ages present in the Main belt. Paleoproterozoic (∼1.8 Ga) inherited zircons were found in three intrusions from the south-western part of the belt where Precambrian crust of the North-Asia craton is inferred to underlie it.

Tectonic evolution of the Siberian Platform during the Vendian and Phanerozoic

This paper presents characteristics of the structural regions surrounding the Siberian Platform and discusses the Vendian-present time evolution of the Siberian Paleocontinent with the Siberian Craton making up its nucleus. It shows that the paleocontinent underwent significant intraplate compressional deformations with vertical movements and formation of inversion structural features within broad areas. Such epochs of deformation took place at the Riphean-Vendian time boundary, during the Late Paleozoic, Late Triassic, Early Cretaceous, and during the Late Cenozoic. The principal rifting events took place during the Middle-Late Devonian. The paper presents paleotectonic reconstructions of East Siberia at several key time intervals.

Reconstruction of provenances and carboniferous tectonic events in the North-East Siberian Craton framework according to U-Pb dating of detrital zircons

The U-Pb dating of detrital zircons from Carboniferous rocks in the northern frontal zone of the Verkhoyansk Fold-and-Thrust Belt (Kharaulakh Anticlinorium) at the boundary with the Siberian Platform is carried out for the first time. The age distribution of detrital zircons from the four dated samples has much in common, indicating that the same sources of clastic material were predominant. All of the samples are dominated by Precambrian zircons; the majority of them are Paleo- and Neoproterozoic grains. Early Ordovician and Late Devonian-Early Carboniferous detrital zircons are also numerous. The igneous rocks of the Taimyr-Severnaya Zemlya and/or Central Asian foldbelts extending along the northern, western, and southwestern margins of the Siberian continent probably were the main source areas of the studied sedimentary successions. The clastic material was transferred at a great distance by large river systems similar to the present-day Mississippi River and deposited in submarine fans at the passive margin of the Siberian continent. The occurrence of the detrital zircons whose age is synchronous to the time of sedimentation of the Carboniferous successions in the northern Verkhoyansk region (320–340 Ma) allows us to suggest that they were derived from the Taimyr-Severnaya Zemlya Foldbelt and that collision of the Kara Block with the Siberian continent began in the Early Carboniferous. The performed study shows the dating of detrital zircons is very helpful for the paleogeographic and tectonic reconstructions.

U/Pb dating of detrital zircons from late Palaeozoic deposits of Bel’kovsky Island (New Siberian Islands): critical testing of Arctic tectonic models

Detrital zircon U/Pb ages provide new insights into the provenance of Upper Devonian–Permian clastic rocks of Bel’kovsky Island, within the New Siberian Islands archipelago. Based on these new data, we demonstrate that Upper Devonian–Carboniferous turbidites of Bel’kovsky Island were derived from Grenvillian, Sveconorwegian, and Timanian sources similar to those that fed Devonian–Carboniferous deposits of the Severnaya Zemlya archipelago and Wrangel Island and were probably located within Laurentia–Baltica. Detrital zircon ages from the lower Permian deposits of Bel’kovsky Island suggest a drastic change in provenance and show a strong affinity with the Uralian Orogen. Two possible models to interpret this shift in provenance are proposed. The first involves movement of these continental blocks from the continental margin of Laurentia–Baltica towards the Uralian Orogen during the late Carboniferous to Permian, while the second argues for long sediment transport across the Barents shelf.

New data on Upper Carboniferous–Lower Permian deposits of Bol'shevik Island, Severnaya Zemlya Archipelago

We present here a detailed study of the Upper Carboniferous–Lower Permian stratigraphy of Bolshevik Island in the Severnaya Zemlya Archipelago, consisting of the analysis of sedimentary structures and lithostratigraphy, U/Pb detrital zircon dating and structural studies. The preserved sedimentary structures suggest that the studied strata were deposited in a relatively small meandering fluvial system. U/Pb dating of detrital zircons reveals that the Upper Carboniferous–Lower Permian sandstones contain a primary age population ranging from 450 to 570 millions of years, with a predominance of Early–Middle Ordovician zircons. This detrital zircon distribution indicates that the studied formations were derived locally from the erosion of Lower Ordovician deposits of Bolshevik Island or elsewhere in the archipelago. Our structural studies suggest that Upper Carboniferous–Lower Permian deposits are deformed into a series of west–north-west verging open asymmetric folds, suggesting a west–north-west direction of tectonic transport and that deformation across the island is post-Early Permian in age.

Detrital zircon U-Pb geochronology of Mesozoic sandstones from the Lower Yana River, northern Russia

The formation of the Amerasian Basin of the modern Arctic remains enigmatic in terms of both timing and method of formation. Most models used to describe its formation involve movement of the Arctic Alaska-Chukotka microplate across the basin’s current location. Detrital zircon U-Pb geochronology has been shown to be an inexpensive yet powerful method by which the tectonic correlation and proximity between multiple terranes over geologic time can be approximated. Five detrital zircon samples were collected from Late Jurassic sandstones from the Lower Yana River area and compared to previous results from detrital zircons collected from nearby Triassic strata. Jurassic samples had detrital zircon age populations of 147–210 Ma, 223–396 Ma, 1639–2183 Ma, and 2281–3116 Ma. Comparison of all detrital zircon ages from the Lower Yana River to those dated from Triassic and Jurassic sandstones of Chukotka, the Verkhoyansk fold-and-thrust belt, and the In’yali-Debin synclinorium supports the interpretation that Chukotka was separated from the Kular area during the Triassic. Jurassic detrital zircon age populations suggest that the Anyui Ocean had closed by the Tithonian, bringing Chukotka to a location where it could be fed by similar depositional systems as the Verkhoyansk fold-and-thrust belt and the Lower Yana River area. Sedimentological and detrital data presented here also suggest that the Yana fault does not represent a regional suture between the Kolyma-Omolon superterrane and the Siberian craton.

Results of U–Pb (LA–ICPMS) dating of detrital zircons from metaterrigenous rocks of the basement of the North Kara basin

The U–Pb (LA–ICPMS) age was established for detrital zircons from the oldest, intensely deformed metasedimentary complexes without reliable fossils’ record, which represent the folded basement of the North Kara basin and are exposed on Bol’shevik and Troinoi islands (Severnaya Zemlya and Izvestii TSIK archipelagoes, respectively). Our data suggest the common evolution of the Cambrian–Ordovician sequences exposed on the islands of both archipelagoes.