Uralides Research Articles

Early Mesozoic sinistral transpression along the Pai-Khoi–Novaya Zemlya fold–thrust belt, Russia

Abstract The NW–SE-trending Pai-Khoi fold–thrust belt links the Permian Uralian Orogen in the Polar Urals with the early Mesozoic fold belt on Novaya Zemlya. An interpretation of structural lineaments present in southern Novaya Zemlya suggests that the NW–SE-trending fold belt in southernmost Novaya Zemlya may have formed contemporaneously with parallel sinistral strike-slip faults. Analysis of regional-scale geological maps of the adjacent Pai-Khoi fold–thrust belt reveals large-scale structural relationships indicative of sinistral shear along the fold–thrust belt, including the presence of left-stepping en echelon folds within the Kara Shale Allochthon. This interpretation is corroborated by a field study of the allochthon-bounding Main Pai-Khoi Thrust, which reveals a consistently oblique tectonic stretching lineation, pitching 56° towards the east, suggesting tectonic displacement towards the west. It is therefore proposed that the Pai-Khoi fold–thrust belt is best described as a zone of sinistral inclined transpression. The interpretation of the Pai-Khoi fold–thrust belt as a zone of sinistral transpression has important implications for the interpretation of this tectonic boundary. This is reflected in a new structural cross-section through southernmost Novaya Zemlya, which is characterized by thick-skinned tectonics and steep strike-slip faults. These faults may link at depth with the Baidaratsky Fault.

Thrust and strike-slip deformations on the southern part of polar Urals based on the rock magnetic data

Petromagnetic characteristics rocks croup out in the Main Uralian Fault zone and Voikar- Synya ophiolites confirmed that multistage deformation led to formation of modern structure of Ural. Analysis of the anisotropy of the magnetic susceptibility of rock minerals detects orienta- tion formed by the thrust (reverse faults) and strike-shear strain at an early stage of the Uralian orogeny. The main axes of the ellipsoid of the anisotropy of magnetic susceptibility associated with regional thrusting - the main stage of formation of structure of the Urals have been revealed rarely. It indicates almost complete resetting thrust petrofabric by later shear deformations.

TIMING OF LOWER CRUST GENERATION IN THE VOYKAR OPHIOLITE MASSIF, POLAR URALS, RUSSIA: U-Pb (LA-ICP-MS) DATA FROM PLAGIOGRANITE ZIRCONS

The Uralide Orogen is one of the main Paleozoic belts formed during the assembly of Pangea. The present-day Urals (Uralian Mountains, N-S-trending through northern Eurasia) expose the relics of this Paleozoic orogen. The Voykar Massif, located at the Polar Urals, is an ophiolite assemblage composed mainly of mantle tectonite, gabbroic to ultramafic plutonic sequence and sheeted dikes with a MORB-type source. Geochronological data for this region show a wide range of ages and are mainly based on U-Pb zircon data, although some Rb-Sr and Sm-Nd are available. We present high-resolution U-Pb (LA-ICP-MS) analyses performed on zircon crystals extracted from a plagiogranite vein associated with a porphyritic dolerite dike. Magmatic zircon grains yielded a U-Pb age of 428.1±7.4 Ma, corresponding to the Wenlock Period (middle Silurian). This age suggests a late stage of oceanic crust generation in the Voykar basin. Different ages from plagiogranite and gabbroic bodies suggest that oceanic spreading lasted from ca. 490 to 425 Ma, i.e., at least 65 Ma or even longer, in the Voykar basin.

Evidence for Late Triassic provenance areas and Early Jurassic sediment supply turnover in the Barents Sea Basin of northern Pangea

We used detrital zircon fractions from the Late Triassic to Early Jurassic sedimentary succession in the Norwegian Barents Sea to constrain the role of eastern provenance areas in the basin infill history of the Northern Pangea Boreal basin. Geochronological data from sedimentary rocks in this succession reveal detrital zircon ages that are very close to the biostratigraphically defined maximum depositional age of the two lowermost intervals: The Norian to Rhaetian Fruholmen Formation show U-Pb minimum ages of 208.3 ± 4.2 Ma (discordant by -0.58) and 213.8 ± 5 Ma (discordant by 0.8), and the Rhaetian to Sinemurian Tubaen Formation is 200.6 ± 4.9 Ma (discordant by -3.99) at its minimum. These are the youngest ages thus far documented in the Norwegian Barents Sea, and they demonstrate that a provenance area was magmatically active while, or shortly before, these formations were being deposited. Such protolith ages have not been documented close to the study area, but based on the regional tectonic setting and paleogeography, we argue that the Novaya Zemlya protrusion of the northern Uralian orogen was the most likely provenance area in the region. The Sinemurian to Pliensbachian Nordmela Formation samples yielded, with an exception of a single detrital zircon age of 211 ± 4.3 Ma, a consistent 240–237 Ma minimum detrital zircon age, which suggests that either the magmatic activity or the sediment supply had come to an end by Sinemurian times. This turnover can be explained by a change in the hinterland drainage pattern. This study documents that eastern provenance areas were actively supplying sediments into the Norwegian Barents Sea Basin later than previously assumed, and our data offer age constraints for tectonic activity in the basin and its hinterland inferred from the changes in sediment supply to the basin.

Provenance of Triassic sandstones on the southwest Barents Shelf and the implication for sediment dispersal patterns in northwest Pangaea

Thick Triassic siliciclastic units form major reservoir targets for hydrocarbon exploration on the Barents Shelf; however, poor reservoir quality, possibly associated with variation in provenance, remains a key risk factor in the area. In this study, sandstone dispersal patterns on the southwest Barents Shelf are investigated through petrographic and heavy mineral analysis, garnet and rutile geochemistry and zircon U-Pb geochronology. The results show that until the Early Norian Maximum Flooding Surface, two contrasting sand types were present: (i) a Caledonian Sand Type, characterised by a high compositional maturity, a heavy mineral assemblage dominated by garnet and low chrome-spinel:zircon (CZi) values, predominantly metapelitic rutiles and mostly Proterozoic and Archaean detrital zircon ages, interpreted to be sourced from the Caledonides, and (ii) a Uralian Sand Type, characterised by a low compositional maturity, high CZi values, predominantly metamafic rutiles and Carboniferous zircon ages, sourced from the Uralian Orogeny. In addition, disparity in detrital zircon ages of the Uralian Sand Type with contiguous strata on the northern Barents Shelf reveals the presence of a Northern Uraloid Sand Type, interpreted to have been sourced from Taimyr and Severnaya Zemlya. As such, a coincidental system is inferred which delivered sand to the Northern Barents Shelf in the late Carnian/early Norian. Following the Early Norian Maximum Flooding Surface, a significant provenance change occurs. In response to Late Triassic/Early Jurassic hinterland rejuvenation, supply from the Uralian Orogen ceased and the northern Scandinavian (Caledonian) source became dominant, extending northwards out on to the southwest Barents Shelf. The data reveal a link between reservoir quality and sand type and illustrate how provenance played an important role in the development of clastic reservoirs within the Triassic of the Barents Shelf.

Zirconology of miaskites from the Ilmeny Mountains, South Urals

It is shown that the replacement and long evolution of miaskitic zircons led to the formation of two main age groups: 420–380 Ma (I) and 260–240 Ma (II). The age of miaskites is estimated at 440–445 Ma. Zircons I bear traces of fragmentation, dissolution, and replacement; they have “flat” REE patterns typical of metasomatic (hydrothermal) types, which is caused by allochthonous nature of the studied miaskites. Zircons II with differentiated REE patterns are similar to magmatic varieties, but have metamorphic origin. Mineralogical–geochemical and age characteristics of zircons in combination with structural–compositional features of miaskites define their metasomatic nature. The origin of the early zircon generations was related to the Ordovician rifting, while late generations were formed during shear deformations at the final stage of the evolution of the Uralian orogen.

Geochemistry and isotopic ages of granitoids of the Bashkirian Mega-Anticlinorium: Evidence for several pulses of tectono–magmatic activity at the junction zone between the Uralian orogen and East European Platform

The study provides the first evidence for post-Riphean phases of granite emplacement in the Bashkirian Mega-Anticlinorium (BMA) at the boundary between the East European Platform and Uralian orogen. The tectono-thermal activity in the BMA is well-constrained by emplacement of the Kusa–Kopan plagiogranitoid intrusion (660 Ma) and late gneiss–granites of the Yurma complex (540 Ma). The geochemical features of these rocks are transitional between within-plate rift and orogenic suites. It was shown that the Paleozoic stage of the BMA was marked by emplacement of granites of the Kialim massif (314 Ma) and Semibratka complex (300 Ma). The age and geochemical features of these rocks are similar to those of Carboniferous granites of the Uralian orogen, which are interpreted to mark the end of subduction and beginning of collision. This similarity suggests that the BMA was adjoined to the Uralian orogen in the Carboniferous and Paleozoic granite emplacement in both structures was the result of their common geological evolution and protoliths of a similar geochemical composition.

Geochronologic Constraints on the Permian–Triassic Northern Source Region of the Sverdrup Basin, Canadian Arctic Islands

Detrital zircon U–Pb ages are used to provide constraints on the geologic evolution of the sediment source area(s) north of the Sverdrup Basin from the middle Permian to Late Triassic. Previous research on facies relationships and sediment progradation patterns of late Paleozoic and Triassic strata from the northern portion of Sverdrup Basin indicate that substantial sediment was derived from north of the basin. Utilizing LA-ICP-MS U–Pb geochronology we have analyzed detrital zircons from these northerly derived strata, including sandstones of four Late Triassic (Norian) outcrop samples the northeast Sverdrup Basin, and two Triassic (Olenekian and Carnian) and two Permian (Roadian and Wordian) samples from wells in the northwestern Sverdrup Basin.The samples from northwestern Sverdrup Basin contain abundant Early Mississippian (350Ma) to Early Ordovician (460Ma), late Cambrian (500Ma) to Cryogenian (650Ma), and early Tonian (960Ma) to Orosirian (2050Ma) detrital zircon. The detrital zircon ages from these samples are similar to zircon age components of Late Devonian siliciclastic strata of the Franklinian foreland basin, and we suggest a similar source area, a low-lying landmass north of the Sverdrup basin, which included extensive Devonian foreland basin strata.The U–Pb detrital zircon age components of northerly-derived Late Triassic strata of northeastern Sverdrup Basin samples are similar to the Permian and Triassic Northwestern Sverdrup Samples, but also contain a substantial age component of Triassic (201Ma) to Middle Mississippian (340Ma) detrital zircons, suggesting an additional source area. The only well documented source for such zircons in the Arctic region is the Ural Orogen. Consequently, it is postulated that, in the Late Triassic, sediment was transported ~1500km from the northern Urals, across the northern landmass, all the way to the shoreline of northeastern Sverdrup Basin.

The Ural–Herirud transcontinental postcollisional strike-slip fault and its role in the formation of the Earth’s crust

The paper considers the morphology, deep structure, and geodynamic features of the Ural–Herirud postorogenic strike-slip fault (UH fault), along which the Moho (the “M”) shifts along the entire axial zone of the Ural Orogen, then further to the south across the Scythian–Turan Plate to the Herirud sublatitudinal fault in Afghanistan. The postcollisional character of dextral displacements along the Ural–Herirud fault and its Triassic–Jurassic age are proven. We have estimated the scale of displacements and made an attempt to make a paleoreconstruction, illustrating the relationship between the Variscides of the Urals and the Tien Shan before tectonic displacements. The analysis of new data includes the latest generation of 1: 200000 geological maps and the regional seismic profiling data obtained in the most elevated part of the Urals (from the seismic profile of the Middle Urals in the north to the Uralseis seismic profile in the south), as well as within the sedimentary cover of the Turan Plate, from Mugodzhary to the southern boundaries of the former water area of the Aral Sea. General typomorphic signs of transcontinental strike-slip fault systems are considered and the structural model of the Ural–Herirud postcollisional strike-slip fault is presented.

Reconstruction of tectonic events on the northern Eurasia margin of the Arctic, from U-Pb detrital zircon provenance investigations of late Paleozoic to Mesozoic sandstones in southern Taimyr Peninsula

The Taimyr fold-and-thrust belt records late Paleozoic compression, presumably related to Uralian orogenesis, overprinted by Mesozoic dextral strike-slip faulting. U-Pb detrital zircon analyses of 38 sandstones from southern Taimyr were conducted using laser ablation–inductively coupled plasma–mass spectrometry to investigate late Paleozoic to Mesozoic sediment provenance and the tectonic evolution of Taimyr within a regional framework. The Pennsylvanian to Permian sandstones contain detrital zircon populations of 370–260 Ma, which are consistent with derivation from the late Paleozoic Uralian orogen in northern Taimyr and/or the polar Urals. Late Neoproterozoic through Silurian ages (688–420 Ma), most consistent with derivation from Timanian and Caledonian age sources, suggest an ultimate Baltica source. Southern Taimyr represents the proforeland basin of the bivergent Uralian orogen in the late Paleozoic. Triassic sedimentary rocks contain detrital zircon populations of Carboniferous–Permian (355–260 Ma), late Neoproterozoic to Early Devonian (650–410 Ma), and minor Neoproterozoic (1000–700 Ma) ages, which suggest a similar provenance as the Carboniferous to Permian strata. The addition of a Permian–Triassic (260–220 Ma) zircon population indicates derivation of detritus from Siberian Trap–related magmatism. Jurassic samples have a dominant age peak at 255 Ma and a distinct reduction in Carboniferous–Permian and late Neoproterozoic to Early Devonian input, suggesting that erosion and contributions from Uralian sources ceased while greater input from Siberian Trap–related rocks of Taimyr dominated. Comparison of these results to the published literature demonstrates that detritus from the Uralian orogen was deposited in Taimyr, Novaya Zemlya, and the New Siberian Islands in the Permian, but not in the Lisburne Hills or Wrangel Island. In the Triassic, Taimyr, Chukotka, Wrangel Island, the Kular Dome in the northern Verkhoyansk of Siberia, Lisburne Hills, Franz Josef Land, and Svalbard shared sources from Taimyr, the Siberian Traps, and the polar Urals, indicating that there were no geographic barriers among these locations prior to opening of the Amerasia Basin. Detritus from the Uralian orogen in Taimyr was shed northward into the retroforeland basin and was then transported farther 20–30 m.y. after Uralian orogenesis. The widespread distribution of material eroded from Taimyr and the polar Urals during the Triassic is likely due to the arrival of, and sublithospheric spreading associated with, the Siberian mantle plume head at ca. 250 Ma. The subsequent motion of the lithosphere relative to the plume-swell likely caused a northwestward migration of the uplifted regions. Taimyr and the polar Urals were probably affected. In the Jurassic, detrital zircon spectra from Taimyr, Chukotka, the Kular Dome, and Svalbard show great differences, suggesting that these locations no longer shared the same provenance from Taimyr and the Urals. The restricted distribution of detritus from Taimyr and the Urals indicates that erosion of the Uralian orogen was reduced. In the Late Jurassic, the depositional setting of southern Taimyr probably changed from a foreland to an intracratonic basin.

Regional development and sequence stratigraphy of the Middle to Late Triassic Snadd Formation, Norwegian Barents Sea

The Middle to Late Triassic Snadd Formation represents one of the later stages of Early Mesozoic infilling of the Barents Sea Basin, expressed by a silicilastic wedge prograding from the southeast, where sediments were shed from the Uralide Orogeny. The formation was deposited in a shallow (100–500 m) basin facing the Boreal part of the Panthalassa Ocean, and the progradation reached its peak at the Svalbard Archipelago which has since been uplifted and where outcrops are exposed as the time-equivalent Botneheia and De Geerdalen formations. The Snadd Formation includes depositional environments ranging from offshore shale through shallow marine to fluvial, arranged in discrete stratigraphic sequences.Here we present a refined sequence stratigraphic framework for the Snadd Formation. Two second order sequences have been interpreted within the limits of the study area, divided into six third order sequences. The two second order sequences are split along an Intra Carnian maximum flooding surface. Depositional elements inherent to the sequence stratigraphic framework are also interpreted and extrapolated so as to describe the regional distribution of potential reservoir sandstones and the control exerted on the development of third order sequences.Different depositional environments from various datasets and scales of observation show the progressive development of a prograding delta across more than 700 km from a proximal position on the Finnmark Platform to a distal position on Edgeøya. Regional correlation of well logs and 2D seismic coupled with detailed depositional environment interpretation from 3D seismic and core has resulted in basin-wide palaeogeographic reconstruction of the formation throughout the Norwegian part of the Barents Sea, with implications for understanding the distribution and evolution of depositional systems during this large-scale basin infill.

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.

Метаморфогенные плагиоклазиты зоны ГУР как результат мезозойского этапа формирования Уральского орогена

Метаморфогенные плагиоклазиты зоны ГУР как результат мезозойского этапа формирования Уральского орогена

The New Siberian Islands and evidence for the continuation of the Uralides, Arctic Russia

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. Supplementary material: Sample co-ordinates, sediment petrography and heavy mineral analysis, U–Pb data tables and description of analytical methods associated with detrital zircon and granite analyses are available at http://www.geolsoc.org.uk/SUP18784 .

The recent tectonics of the Caspian Sea region

Recent uplifts and depressions complicated by lineaments, many of which are faults, were found within the Caspian depression using complex structural and geomorphological studies, which included visual interpretation of different-scale topographic maps, as well as an analysis and computer processing of radar satellite images. In many respects, the latest dislocations correlate with the structures and sedimentary cover of the basement and are also determined by salt tectonics. Their formation is substantially influenced by the Ural Orogen and the Scythian plate is involved in the entire uplift at the latest stage.

Provenance of Late Paleozoic-Mesozoic Sandstones, Taimyr Peninsula, the Arctic

The sedimentary and provenance characteristics of seven Permo-Carboniferous and two early Cretaceous samples from the Taimyr Peninsula provide information about the latest evolution of Uralian orogeny and the opening of the Amerasian Basin. The Permo-Carboniferous samples have a mixed provenance of recycled and first cycle sediment, sourced from metamorphic and igneous terranes. U-Pb detrital zircon ages represent a mixture of Precambrian-Paleozoic grains with euhedral, penecontemporaneous late Carboniferous and Permian grains consistent with derivation from the Uralian Orogen, plus additional Timanian and Caledonian material presumably derived from Baltica. Differences between the late Permian sample and the other Carboniferous and early Permian samples are interpreted to reflect the final collisional stage of Uralian orogeny. Early Cretaceous sediments deposited at the time of the Amerasian Basin opening preserve a mixed provenance of mainly first cycle metamorphic and igneous source material, as well as an unstable heavy mineral assemblage dominated by staurolite, suggesting local derivation. Detrital zircon ages fall almost exclusively into one late Permian-early Triassic cluster, indicating a Siberia Trap-related magmatic source. The detrital zircon age spectra support a passive margin setting for Taimyr during the opening of the Amerasian Basin in the early Cretaceous.

Structural controls in the western offshore Midland Valley of Scotland: implications for Late Palaeozoic regional tectonics

AbstractNew detailed mapping and related field studies, together with re-assessment of prior investigations, have revealed that three groups of faults, orientated broadly NE, N and NW, have been the primary controls on stratigraphical, structural and geomorphological evolution in the upper Firth of Clyde since their initiation by proto-Variscan stresses in Late Devonian time. Extended control has been achieved through repeated episodic reactivation, during which existing lines of fracture were rejuvenated and others of similar orientation initiated. Movements on two (if not all three) groups of faults persisted until middle Palaeogene time at least. The faults have been augmented by two sets of irregularly distributed, open, plunging folds, broadly N–S and E–W in their axial orientations. Some N–S folds may be attributed to oblique or strike-slip movement on reactivated caledonoid faults, others to intermittent transpression, probably in Namurian–Westphalian times, affecting mainly the northeastern Midland Valley but stretching beyond the massif of the Clyde Lava Plateau to register a weakened presence as far W as the upper Firth. The N–S folds and dextral strike-slip movements on some faults may be far-field expressions of the Uralian Orogeny, whereas earlier, sinistral displacements on NE faults and the development of small, later and less-significant E–W folds may be related to different phases of long-lived Variscan compression from the S.

Geology and ore deposits of the Urals

The Urals is a N-S trending mountain range forming thegeographic boundary between Europe and Asia. It repre-sents a 2000 km long Paleozoic orogen, extending from theIslands of Novaya Zemlya in the north to the Aral Sea in thesouth. For a long time the information about Uralian geol-ogy was very scarce in the international literature. A signif-icant breakthrough took place at the end of 20th centurywhen the EUROPROBE and GEODE international projectsstarted. In the frame of these projects, several seismic crosssections trough the Urals, together with detailed geologicalinvestigations, were carried out. The main results of thesestudies were published in a special Issue of Tectonophysics(1997) and in the Geophysical Monograph 132 “MountainBuilding in the Uralides: Pangea to the Present” publishedby American Geophysical Union (AGU) in 2002 and innumerous other papers. In the last decade a lot of newmineralogical, petrological and geochemical data, particu-larly in isotope geochemistry andgeochronology,weregath-ered. These new data represents the base for the need for afurther look onto Uralian geology. This special issue ofMineralogy & Petrology contains a profound collections ofnew data, interpretations and discussional aspects on Urali-an geology since 2002.The Urals belongs to the western flank of the hugetranscontinental Uralo-Mongolian fold belt and comprisesat least three billion years of geological history. Today wecan distinguish between five major structural levels andepochs of the Urals development (see Puchkov 2013). Theearliest Archean and later Meso-Neoproterozoic complexes,although related to the development of the Baltic craton andits eastern periphery, far before the Uralides existed, areincorporated in the Uralian orogen structure and sometimesthey display traces of young Paleozoic events of the foldbelt. The Archean rocks are represented by granulites of theTaratash complex, showing similarities to the granulites inthe basement of the East-European platform. The Meso-Neoproterozoic sedimentary and magmatic complexes wit-ness the geotectonic development along the eastern marginof the Baltic Shield. This time was very productive regard-ing the formation of some important mineral deposits, suchas siderite and magnesite within metasedimentary sequences(Prochaska and Krupenin 2012) and titano-magnetite oreassociated with rift-related layered gabbro intrusions andothers.The Paleozoic–Lower Jurassic period of time may beconsidered as the main stage of the development of theUralides, covering a complete Wilson cycle: starting fromthe rifting of the Baltic continent after the Timanian oroge-ny, through formation of an oceanic basin, a passive conti-nental margin and microcontinental blocks, to subduction,accompanied by a significant amount of volcanic eruptions,then arc-continent collision, continent–continent collisionwith granite magmatism, formation of a long chain of bath-oliths, and finally post-collisional extension with flood-basalt magmatism. The most important and famous volca-nic, intrusive, metamorphic and sedimentary complexes andrelated deposits in the Urals were formed during this periodof time. The world-class podiform chromite deposits relatedto the Kempirsay ophiolite complex in the Southern Uralswere formed during oceanic-island arc development. Thegiant Gay, Sibay and Uchaly volcanic massive sulfidedeposits and many numerous small ones are located withinthe Devonian island-arc volcanics of the Magnitogorsk zone

The main features of the Uralian Paleozoic magmatism and the epioceanic nature of the orogen

The 2000 km Uralian Paleozoic orogen is situated on the western flank of the Uralo-Mongolian folded belt. It is characterized by an abundant variety of magmatic rocks and related ore deposits. Uralian Paleozoic magmatism is entirely subduction-related. It is proposed that the Uralian orogen represents a cold mobile belt in which the mantle temperature was 200 to 500 °C cooler than in the adjacent areas; a situation which is similar to the modern West Pacific Triangle Zone including Indonesia, the Philippine Islands, and southern Asia. During the course of the geological evolution of the Uralian orogen, the nature of the magmatism has changed from basic rocks of indisputable mantle origin (460–390 Ma) to mantle-crust gabbro-granitic complexes (370–315 Ma) followed by pure crustal granite magmatism (290–250 Ma). This order in rock type and age reflects the evolution of Paleozoic magmatic complexes from the beginning of subduction to the final stages of the orogen development.

Chapter 18 Geology and petroleum potential of the Timan–Pechora Basin Province, Russia

Abstract The Timan–Pechora Basin Province represents the northeastern-most cratonic block of Eastern European Russia. More than 16 billion barrels of oil (BBO) and 40 trillion cubic feet of gas (TCFG) have been discovered in this basin. Three geological assessment units (AU) were defined for assessing the potential for undiscovered oil and gas resources. The NW Izhma Depression AU encompasses all potential structures and reservoirs in the northwestern part of the Izhma–Pechora Depression, but this part of the basin contains little source and reservoir rocks and so was not assessed quantitatively. The Main Basin Platform AU includes all structures and reservoirs that developed in the central part of the basin where the tectonic evolution and development of petroleum systems were complex. The Foredeep Basins AU includes all potential reservoirs within the thick sedimentary section of the foredeep basins developed during the Permo-Triassic Uralian Orogeny. For the Timan–Pechora Basin Province, the estimated means of undiscovered resources are 3.3 BBO, 17 TCFG and 0.3 billion barrels of natural gas liquids (BBNGL). For the areas of the AUs north of the Arctic Circle in the Timan–Pechora Basin Province, the estimated means of undiscovered resources are 1.7 BBO, 9.0 TCFG and 0.2 BBNGL. The Pechora Sea was assessed with the South Barents Sea Province and is not included in this assessment. Supplementary material: Supplementary Appendices 1–3 are available at http://www.geolsoc.org.uk/SUP18474 .