Sources Of Clastic Material Research Articles

Сходство и различие состава среднеюрских и нижнеплиоценовых отложений на северо-западном берегу Байкала: Оценка вклада обломочного материала Приморского хребта в аллювий средней части долины Пра-Манзурки

A comparative analysis is performed between compositions of pebbles and sandy filler of a pebble package that finalizes a section of the Lower Pliocene Buguldeyka alluvium horizon in the middle part of the Pra-Manzurka valley and those of pebbles and sandy cement of the Middle Jurassic conglomerates of the Nizhniy Koty sub-formation from outcrops of the Angara-Koty depression in the southeastern part of the Irkutsk coal basin. A partial similarity in major oxide and trace element contents in trachydacites and rhyolites of pebbles from Pliocene and Jurassic deposits is defined. From the difference in major oxide and trace element contents of the sand filler of the lower and upper layers of the pebble package of the Pra-Manzurka valley, the difference in their sources is inferred. It is proposed that the convergence between the composition of the sandy filler of the lower layers of the Pliocene pebble package and those of the trachydacite-rhyolite pebbles from this and of the sand cement of the Middle Jurassic conglomerates may reflect the erosion of the clastic material of the Middle Jurassic conglomerates and its removal into the middle part of the Pra-Manzurka valley in the initial phase of the uplift of the Primorsky Range. Occurrence of a Th/Co anomaly in the lower layers of the pebble unit, not typical for Jurassic conglomerates, indicates the formation of the pebbles from another source of clastic material.

Early Ediacaran and Middle Ediacaran Granitoids in the Provenances of Early Cambrian Coarse-Grained Rocks of the Bayan-Kol Formation of the Systyg-Khem Depression (Tuva)

Abstract —The Tuva segment of the Central Asian Orogenic Belt is characterized by the ubiquitous presence of conglomerates few tens of meters to a kilometer in thickness in early Paleozoic volcanosedimentary sequences. We present the first results of geochemical, isotopegeochemical (Sm–Nd and Rb–Sr), and U–Pb geochronological studies of granitoid boulders and pebbles from the conglomerate sequence of the early Cambrian Bayan-Kol Formation of the Systyg-Khem depression. These studies made it possible to establish several sources of clastic material as a result of the destruction of granitoids of different ages and isotope-geochemical compositions. At least two complexes of granitoids were denuded in the pre-Ediacaran tectonic block in the early Cambrian: (1) middle Ediacaran (~590 Ma) and (2) early Ediacaran (~630 Ma); the latter resulted from the melting of pre-Ediacaran island arc crust formed from a depleted mantle source (εNd(T) = +8.0 to +8.6). At present, no granitoids of this age and with such isotope-geochemical characteristics have been found within the Tuva segment. Probably, the granitoid complexes reconstructed from the results of study of clastic conglomerates are eroded or buried beneath younger deposits and do not expose. Thus, the study of clastic conglomerates from the Bayan-Kol Formation provided the first information about the Precambrian history of the tectonic block whose destruction led to the accumulation of this terrigenous sequence.

Specific features of sandstones of Upper Devonian Tayokuyakhinskaya Formation on southeastern slope of the Kanin Kamen range (Kanin Peninsula)

The results of studying the lithological and geochemical characteristics of sandstones of the Upper Devonian Tayaokuyakhinskaya Formation in the southeastern part of the Kanin Nos Peninsula are presented. The accumulation of sandstones of the Tayaokuyakhinskaya Formation occurred in the absence of volcanic activity in a shallow basin with small periodic fluctuations in sea level, which led to a change in the degree of maturity, sorting, and the ratio of clay and sandy components in the rock. The accumulation of the psammitic strata occurred due to the destruction and redeposition of weakly weathered sedimentary rocks in a moderately warm climate. It was established that the formation of the composition of sandstones was influenced by at least two sources of clastic material — garnet-bearing crystalline shales and feldspar-quartz sandstones metamorphosed into the greenschist facies. The latter, most likely, were the source of the indicative gold contents found in the Devonian clastic rocks.

The Mineral Composition of Sediments as an Indicator of the Supply Sources and Features of the Distribution of Clastic Material in the Sea of Okhotsk

The mineral composition of the heavy subfraction from surface sediments of the Sea of Okhotsk has been studied using two detailed profiles (the Magadan-Kuril Islands and the Shantar Islands-Central part of the Sea of Okhotsk) and data from the Sakhalin Gulf. The obtained data have been analyzed by the methods of multivariate statistics, which allowed us to identify the main associations of heavy minerals that show regional differences in the mineral complexes of marine sediments. A significant effect of the solid discharge of the Amur River on sedimentation processes has been recorded. Two large regional sources of clastic material, the Amur-Sakhalin and Kuril-Kamchatka supplying provinces, had a major influence on the formation of the mineral composition of the sediments.

Неоднородность источников кластического материала терригенных пород Таухинского аккреционного комплекса (Сихотэ-Алинь) на ранних стадиях его формирования

Неоднородность источников кластического материала терригенных пород Таухинского аккреционного комплекса (Сихотэ-Алинь) на ранних стадиях его формирования

Geochemistry of Metasedimentary Rocks, Sources of Clastic Material, and Tectonic Nature of Mesozoic Basins on the Northern Framing of the Eastern Mongol–Okhotsk Orogenic Belt

Abstract —We present results of geochemical studies of the upper Mesozoic deposits of the Strelka and Malaya Tynda depressions and U–Th–Pb (LA-ICP-MS) geochronological and Lu–Hf isotope-geochemical studies of detrital zircons from these deposits. It is shown that the Strelka and Malaya Tynda depressions, adjacent to the Mongol–Okhotsk Orogenic Belt in the north and extending along the boundary between the southern framing of the North Asian Craton and the orogenic belt, are marginal troughs. These troughs are filled with thick beds of Mesozoic marine (at the bottom) and continental (at the top) metaterrigenous rocks, with an increase in the grain size of clastic material up the section; the rocks should be regarded as molasses. The results of U–Th–Pb geochronological studies of detrital zircons from metaterrigenous rocks of the Strelka and Lesser Tynda depressions, on the one hand, and the eastern part of the Mongol–Okhotsk Orogenic Belt, on the other, show that orogenic processes in the east of the belt were completed at the Early–Middle Jurassic boundary. The depressions began to form after the complete closure of the Mongol–Okhotsk basin and the formation of an orogenic structure at its place. Then they were filled with material supplied both from the Selenga–Stanovoi and Dzhugdzhur–Stanovoi superterranes on the southern framing of the North Asian Craton and from the Mongol–Okhotsk Belt, which was a mountain-folded structure in the Middle Jurassic.

Roundness of neoarchean polymictic conglomerate clasts: calculation and interpretation (a case study from the Koikary area Central Karelia)

The method of roundness calculation based on the use of outcrop photos, the CorelDraw software and the PlotCalc plug-in was tested for the case of conglomerates from the Neoarchean molassoid complex of the Koikary area (Central Karelia). According to the results, the roundness of the debris depends on their composition and varies across the section of the molassoid complex. For the clasts of komatiite-basalt and andesitic composition the degree of roundness is the lowest, whereas for plagioporphyrygranites it is the highest. A lateral series of the potential sources of the clastic material is proposed. The mathematical calculation of roundness values is shown to be efficient, so that information can be obtained on the remoteness of the sources of clastic material needed for lithological and geodynamic studies.

Sources of clastic material of Cretaceous–Paleogene deposits in the southwestern part of the Amur–Zeya Basin: results of dating U–Pb detrital zircons

The results of our study indicate that at the Late Cretaceous–Paleogene boundary in the southeastern part of the Amur–Zeya Basin, the sedimentation conditions changed drastically, namely, the change of provenance areas of debris. In the Maastrichtian, the clastic material was mainly transported from the Bureya–Jiamusi Superterrane and the volcanic–plutonic belts of Khingan–Okhotsk and East Sikhote–Alin located to the east: sedimentation occurred simultaneously with magmatic activity. During the Danian Stage, the major source of debris to the southern part of the basin was located to the south of the young mountain system of the Lesser Khingan (the uplifted part of the basement of the Songliao Block).

Age, geochemistry, and sources of clastic materials and accumulation settings of the Glubokin Formation (Eastern Transbaikalia)

We report the results of geochemical, Sm–Nd isotope–geochemical, and U–Pb detrital zircon geochronological studies of metaterrigenous rocks of the Glubokin Formation assigned provisionally to the Upper Riphean. This formation is developed where the Mongol–Okhotsk belt is almost completely squeezed by the surrounding continental structures and, hence, bears important information on its evolution. The obtained results suggest the following conclusions: (1) the Glubokin Formation is Early Pennsylvanian or post-Early Pennsylvanian in age, not Riphean as previously suggested; (2) the Glubokin Formation belongs to the Mongol–Okhotsk Fold Belt rather than to the Argun continental massif, as suggested in the existing schemes of structural zoning; (3) the volcanogenic-terrigenous deposits of the Glubokin Formation were precipitated in a back-arc basin setting above the subduction zone subsiding beneath the southeastern margin of the North Asian Craton; and (4) the main sources of clastic material for the Glubokin Formation were igneous and metamorphic complexes of different ages from the southeastern margin of the North Asian Craton.

PALEOGEOGRAPHIC FEATURES OF THE FORMATION OF SHALE METACONGLOMERATES OF NOVOKRIVOROZHSKAYA SUITE OF KRYVYI RIH STRUCTURE

The paper considers the conditions of formation of novokrivorozhskaya suite that meets the basis of the section of Kryvyi Rih structure. Paleogeographic reconstructions novokrivorozhskaya suite was based on these methods: comparison of intensity factors of weathering and sedimentary differentiation of A.A. Predovsky, the attitude indicator elements and depositional facies conditions – the conditions of sedimentation. Using techniques of V.K. Golovenok, and by comparing the chemical composition of rocks novokrivorozhskaya suite with an average composition of rock-forming oxides clarke in magmatic rocks there was the attempt to reconstruct the climatic conditions of sedimentation suite. The formation analysis usage allowed to determine the likely sources of clastic material and ways of transportation.

Geochemical features and sources of clastic material in Paleozoic terrigenous deposits of the northeastern flank of the South Mongolia–Khingan orogenic belt

The results of geological and geochemical studies of terrigenous rocks of the main stratigraphic subdivisions in the northeastern flank of the South Mongolia–Khingan orogenic belt and also the results of U-Pb (LА-ICP-MS) geochronological studies of detrital zircons from these deposits are presented. It is demonstrated that the studied rocks differ significantly in the nature of distribution of detrital zircon ages and, consequently, they cannot be members of a single sedimentary sequence. The data obtained confirm the standpoint according to which the northeastern flank of the South Mongolia–Khingan orogenic belt represents a “joint” zone separating the Argun and the Bureya-Jiamusi Superterranes. This joint zone was formed as the result of closure of the oceanic basin separating the specified continental massifs in the Paleozoic era. The geochemical features of the studied rocks indicate their formation in the conditions of the island arc or the active continental margin. Lack of zircon generations younger than Ordovician age in the studied samples allows assuming that the sedimentary sequences identified within the northeastern flank of the studied belt as the Necla, Dagmara, siltstone-sandstone, and Gramatukha sequences that formed from the end of the Vendian (?) to the Devonian correspond to the youngest stages of belt formation. These sediments in the current structural plan evidently represent fragments of accretion complexes cropping out in fragments among the Cenozoic sequences of the Amur-Zeya Depression.

Возраст нижнепалеозойских пород останцов выветривания хр. Маньпупунер (Северный Урал)

The article presents the first U-Pb data on the age of the rocks composing scenic erosional outliers located on the Manpupuner Ridge in the Northern Urals. Based on the analysis of the ages of detrital zircons micaceous quartzites exposed on the Manpupuner Ridge are thought to belong to Lower Ordovician Telpos Formation. Sources of clastic material are supposed.

Geochemical features, depositional settings, and provenances of Lower Paleozoic rocks in the Mamyn terrane, Central Asian Fold Belt

New data on geochemical features of the Lower Paleozoic terrigenous rocks in the Mamyn terrane (eastern Central Asian Fold Belt) and U–Pb geochronological studies of the detrital zircon from these rocks are presented. The obtained results suggest the following conclusions. 1. At present, the Kosmataya sequence includes different age Lower Cambrian terrigenous–carbonate and Lower Ordovician terrigenous rocks or represents Lower Ordovician olistostromes including limestone blocks with the Lower Cambrian fauna. Lower Ordovician terrigenous rocks were formed in an island arc or active continental margin, mainly, owing to the erosion of Cambrian–Early Ordovician plutons and volcanics that are widespread in structures of the Mamyn terrane and weakly reworked by the chemical weathering. 2. The Silurian Mamyn Formation was developed at a passive continental margin. The main sources of clastic material for this formation were the same Cambrian–Early Ordovician igneous rocks as for the Cambrian sequence, with the participation of Early Silurian and Vendian igneous complexes. The obtained data significantly refine concepts about the geological structure of the Mamyn terrane, which is a member of the Argun Superterrane, one of the largest tectonic structures in the eastern Central Asian Fold Belt.

Provenance analysis for Middle Eocene sediments in the West Kamchatka sedimentary basin (Tigil area)

The paper presents the results of reconstruction of Middle Eocene provenances for the West Kamchatka sedimentary basin (WKSB) corresponding to the Tigil area. It has been established that the early (Eocene) evolution stage of WKSB was marked by the deposition of terrigenous sediments in intermontane depressions followed by the accumulation of shallow-marine sediments after transgression. In terms of the composition, sandstones of the Middle Eocene Snatol Formation correspond to graywackes. With respect to the geochemistry of sandstones, their provenances were confined to an active continental margin and island arc. The mineral composition of the heavy fraction suggests an alternating dominance of felsic and mafic rocks in the provenances. Dating of the clastic zircon from sandstones of the Snatol Formation by the LA-ICP-MS method revealed a wide variation range of their age. The most significant peak is close to the age of calc-alkaline magmatism in the Okhotsk–Chukotka volcanic belt. This fact provides insight into the Eocene paleogeography: the major rock provenances were located in the Okhotsk–Chukotka volcanic belt and the eastern Achaivayam–Valagin island arc. Local sources of clastic material were represented by the Utkholok and Kinkil volcanic belts.

Local tectonics and sedimentation in grabens of the Central Russian aulacogen (East European Platform)

The influence of local tectonic processes that determined individual development of each particular graben in the Central Russian aulacogen is best reflected in the asynchronous appearance of compositionally different clastic materials in their sedimentary sections, which accumulated with variable intensity. Against the background of the stable composition of the clastogenic framework of the terrigenous Molokovo Group, there are intervals of the sedimentary section from tens to a few thousands of meters thick, where the heavy fraction of sandstones is highly enriched (35–95%) with acute-angled epidote grains. Several features (relative instability of epidote in the hypergenesis zone, angular and fresh appearance of clasts, absence of correlation between the epidote influx and content of the main rock-forming components) imply the formation of epidote anomalies owing to local sources. Analysis of probable geodynamic mechanisms, which could determine development of the Central Russian aulacogen and its grabens, structure and composition of the upper part of the consolidated crust, made it possible to assume that the specific clastic material originates from epidote-rich blastomylonites occurring among metamorphic rocks of the basement in form of strata with anomalous petrogeophysical properties. Comparison between crystals and grains of epidote from blastomylonites and sediments shows that they are characterized by similar habit, sizes, and optical parameters and contain 25–30% of the pistacite component, which is typical of secondary epidote that forms pseudomorphs after biotite and amphibole under conditions of partial melting. Regularities in the distribution of epidote-rich intervals in the sedimentary section are explained by relations between attitude elements of planes of Neoproterozoic normal faults and Paleoproterozoic blastomylonite strata, which served as local sources of clastic material. The same factor also determined the facies properties of sedimentary complexes and structural evolution of sedimentation basins. Crosscutting normal faults stimulated the formation of grabens with the rheologically determined subsidence limit (Molokovo type), particularly, in situations characterized by the gentle attitude of blastomylonite bodies. In such a situation, the subsidence of granitoid rocks into the denser amphibolite substrate was limited by isostatic leveling forces. Under the stationary regional strain field after reaching the subsidence limit, grabens of this type experienced lateral extension, which resulted in the accumulation of regressive sedimentary successions with the irreversible transition from the lacustrine to the fluvial–proluvial facies. Such grabens are characterized by the one-act manifestation of the local source of clastics regardless of the structure development stage. The development of more expedient (in terms of energy) normal faults along blastomylonite strata (Roslyatino type) did not disturb the isostatic equilibrium and resulted in the formation of narrow deep grabens, where depositional environments remained virtually unchanged. The epidote influx was in progress during the entire life of the accommodation space, since progressive deepening of the graben stimulated constant activity of its local source.

Composition and formation settings of cretaceous terrigenous rocks of the West Sakhalin terrane

The source areas and formation settings of Cretaceous rocks of the West Sakhalin terrane are established on the basis of the composition of terrigenous rocks. Sedimentation along the continent–ocean boundary was accompanied by large-scale left-side transform slides of the Izanagi Plate relative to the Eurasian continent with a minor role of volcanic processes. The ensialic island arc, granite-metamorphic rocks of the mature continental margin, and fragments of ancient accretionary prisms with ophiolites and cherts were the sources of clastic material.

Sources of clastic material in the Carnian diamond-bearing horizon of the northeastern part of the Siberian Platform

Sources of clastic material in the Carnian diamond-bearing horizon of the northeastern part of the Siberian Platform

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.

Trace elements and characteristics of the sources of clastic material in the Devonian and Carboniferous sedimentary formations of the eastern zones of the Southern Urals

This paper focuses on the characteristics of possible provenances for the Devonian and Carboniferous clastic complexes of the eastern zones of the Southern and, in part, Central Urals on the basis of the investigation of trace- and rare-earth element geochemistry, accounting for petrographic evidence. It was found that the material of basic and silicic volcanics, ultrabasic rocks, and metamorphic complexes influenced the geochemical characteristics of the clastic rocks. It was shown that the main sources of the Devonian clastic material were probably subalkaline volcanic rocks from an ensialic oceanic island arc similar to the Silurian arc of the Central Urals, including displaced ones, and the main sources of the Carboniferous sediments were Devonian island-arc complexes and, in part, continental margin volcanics. An eastern source of material existed probably in the Carboniferous in the southern part of the Eastern Ural megazone. The geochemical features of the sedimentary rocks of the Irendyk Formation (upper Emsian-Eifelian) indicate a differentiated source of clastic material.

The relationships between Late Ordovician sea-level changes and faunal turnover in western Baltica: Geochemical evidence of oxic and dysoxic bottom-water conditions

The late Sandbian to the early Katian (Late Ordovician) in southeastern Norway is dominated by marine mudstones that contain an exceptional spectrum of macrofauna and trace element geochemistry, recording both abrupt and gradual faunal changes during major sea-level and environmental shifts. This study investigates the relationships between sea-level changes and their influence on the source of clastic material, oxygen levels in the bottom water and faunal changes, with special emphasis on the brachiopod fauna. Trace element ratios indicate that nearly stable upper dysoxic bottom-water conditions prevailed in the northwestern part of the Baltoscandian Sea. The exception is during the major shallowing in the earliest Katian, when there was an abrupt shift to oxic conditions as the sea bottom came within a normal storm wave base. Nonetheless, the pre-shallowing epibenthic fauna (though not the shelly endobenthic) in this area was rich and diverse and two major immigration phases of new brachiopod taxa are seen well before the shallowing. This indicates that the immigration of new taxa was not the result of an increase in oxygen content in the bottom water. More brachiopod genera stayed during the abrupt shallowing and increased oxic level than did during the following gradual return to deeper, dysoxic environments. The major brachiopod immigration phases took place markedly earlier in this northwestern part of the Baltoscandian Sea than in the central part (Eastern Baltic) and possibly also the comparable faunal turnover in Laurentia. The following disappearance of taxa during an early Katian transgressive event coincided with the faunal turnover in the shallow-water environments of the East Baltic. The depositional history was consistent within the investigated mudstone-dominated offshore facies of the Oslo Region, which are comparable to the Central Baltoscandian Confacies Belt of Baltoscandia. The composition of the siliciclastic material which was deposited in the basin was nearly constant through the sequence, though the land area expanded to include ophiolites, expressed by Cr enrichment, coinciding with the major sea-level drop. The Cr enrichment indicates that, by that time at least, the ophiolite complexes north of the Oslo Region became subaerially exposed. This enrichment thus forms a potential geochemical marker horizon representing the basal Katian Stage.