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This paper considers the results of the mineralogical and chemical study of sandstones and U–Pb isotope dating of detrital zircons from the Paleozoic–Early Mesozoic deposits of the Laoeling–Grodekovo terrane in western Primorye. It is shown that the sandstones of different age of the terrane differ markedly in their mineralogical and geochemical parameters and, hence, were derived from different sources. The sandstones of the Kordonka Formation are made up of fragments of basic and intermediate volcanic rocks of the oceanic island arc, as well as igneous and sedimentary rock associations of the oceanic island-arc basement. Eroded stable cratons and uplifted blocks representing crystalline basement inliers that are either flanked by rift zones or occurring along transform faults exerted a strong effect on the accumulation of sandstones of the Reshetnikovka, Barabash and Mangugai formations. The main suppliers of detritus were felsic igneous rocks with minor input from ancient sedimentary rocks. The rift margins and the eroded ensialic arc provided clastic material for the rocks of the Talmi Formation. The U–Pb geochronological studies of detrital zircons made it possible to constrain the age and possible position of igneous complexes that supplied clastic material to the sedimentary basins of the terrane. The sandstones were found to contain detrital zircons with concordant ages from 2553 to 205 Ma, which are dominated by Paleozoic zircons divided into several age groups. The zircons of Precambrian and Triassic ages are far fewer. In general, the revealed age ranges of detrital zircons from sandstones of the Laoeling–Grodekovo terrane agree fairly well with the known stages of granitoid magmatism in the eastern part of the Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

The geological and hydrogeological conditions of 19 occurrences of thermal waters in the southern Russian Far East are considered in this paper. Radon concentrations were measured in waters, and uranium and thorium concentrations were determined in host rocks and secondary minerals. The results were compared with the chemical composition of waters and gases in the mineral springs. It is established that water-bearing rocks are classified into rocks of low and normal radioactivity. The contents of uranium (<0.56 μg/L) and thorium (<0.1 μg/L) in the waters are low. Measurements of radon concentrations in mineral water springs in Primorye indicate that most of them are weakly radioactive (0.2–1.5 kBq/L), whereas two are moderately radioactive (1.5–7.5 kBq/L). From a medical-balneological point of view, waters in 7 of 19 springs were defined as radon waters, with 4 of them classified as nitrogen thermal water and 3 as CO2-rich mineral waters. The CO2-rich mineral waters of the Shetukha Group exhibit the highest level of radioactivity. Such natural objects reflect the state of the geological environment and can be utilized both for medical purposes and for monitoring a wide range of hydrogeochemical parameters. Based on the analysis of geological conditions and geochemical features of thermal water occurrences, the factors that determine the radioactivity level were identified and general schemes for the radon transport to the surface in different geological and hydrogeological conditions were proposed. [ABSTRACT FROM AUTHOR]

In this study, we consider the deep structure of the Earth's crust and the lithospheric mantle in the central part of the Lower Amur metallogenic zone and its western flank, which includes the Albazino gold ore cluster. Zones with a sharp change in density and magnetic properties associated with Late Cretaceous–Early Paleogene magmatism were established based on the calculated density and magnetic depth models of the territory. A ring structure ~200 km across was identified, which is characterized by the low-density lithospheric mantle and density and magnetic inhomogeneities in the Earth's crust, which are related with a wide development of intrusive bodies within it, as well as their spatial position and composition. The spatial relation of gold ore districts, clusters, and deposits to the density and magnetic inhomogeneities in the crust and lithospheric mantle has been analyzed and the main patterns in their distribution are shown. As a rule, they are confined to the low-density zones in the crust and marginal areas of deep-seated (12–20 km) magnetic intrusions. Based on the conclusions, new promising areas to prospect for gold deposits are proposed. In particular, it was concluded that the potential of the western part of the ring structure to the south of the Albazino deposit to host gold mineralization was underestimated. [ABSTRACT FROM AUTHOR]

The studies of peat stratigraphy in the upper reaches of the Milogradovka River made it possible to reconstruct changes in humidity as a source of moisture in the Sikhote-Alin middle mountains over the last 3400 years. High-resolution reconstructions were based on the biostratigraphic analyses (botanic and diatom) data; the ash content of peat was also studied. Radiocarbon dating of the events was carried out using an age–depth model. B–Tm cryptotephra of the Baitoushan caldera-forming volcano was found in the upper part of the section; it was identified from the volcanic glass chemical composition. Long-term rains are assumed to have caused a massive landslide with the formation of a dam and a shallow reservoir turned the river valley into a bog. The bioindicators of humidity variations in the river valley and of flood events were determined. The events were correlated with the data on the main watershed of the Sikhote-Alin Range, mountainous plateaus, lakes on the slopes of the ancient Solontsovsky Volcano, and the eastern Primorye coast. The peat section in the valley recorded the hydrological changes related to the nature of cyclogenesis in more detail. Paleoevents and large-scale atmospheric circulation anomalies were revealed to be interrelated. Long-term dry phases under global cooling were accompanied by the East Asia aridization caused by a slacking of the East Asian summer monsoon. According to the study results, floods occurred in the summer–autumn period even during dry phases. The flooding phases were related to the summer monsoon activation, as well as to more intensive cyclogenesis. The most complicated climate rhythmicity was established for the last 1340 years. [ABSTRACT FROM AUTHOR]

The absolute age of the Brusilovka paleo-caldera volcanic rocks has been determined for the first time through the LA-ICP-MS U–Pb zircon isotopic dating. The obtained results (~61–56 Ma) are consistent with the Paleocene magmatic stage of the Sikhote-Alin, and the patterns of their structural localization and spatiotemporal distribution are consistent with left-lateral displacements along the Vostochny and Pribrezhny faults. The distribution characteristics of early Paleogene igneous rocks both in the frontal and rear continental-marginal parts of the southern Sikhote-Alin can serve as a basis for paleogeodynamic reconstructions and subsequent metallogenic analysis. [ABSTRACT FROM AUTHOR]

Rare minerals represented by oxides, fluorides, F-carbonates and REE arsenates in association with monazite-Ce, monazite-Th, xenotime-Y and zonal REE fluorite were identified in the rare-metal ores of the Sn–W deposits of Lesser Khingan, Amur region. Rare lanthanide minerals are described, including fluocerite, bastnaesite, and gasparite-Ce, which was found for the first time in Russia in the Sn–W greisens, and chernovite-Y, the second find in the greisens of the Russian Far East. The influence of arsenic fluids at the late hydrothermal stage caused the replacement of xenotime-Y and monazite-Ce by diverse REE minerals with different lanthanide proportions. It is found that these minerals differ in chemical composition from the same minerals described in other deposits elsewhere. Due to the variable valence state of arsenic and the complete isomorphism between rare earths, arsenates can be used as indicators of redox conditions of their deposition. [ABSTRACT FROM AUTHOR]

The results of detailed study of the platinum-group minerals (PGM) from explosive breccias of the Poperechnoe Fe–Mn deposit (the Lesser Khingan Range, Russian Far East) are presented. Native PGMs are dominated by isoferroplatinum; rutheniridosmine, native iridium, platinum, and osmium are less common. Micron-sized segregations of laurite, bowieite, сuproiridsite, cuprorhodsite, hollingworthite, as well as new mineral phases of (Ir,Rh,Os)7(S,As)13, (Rh,Ir,Ru)7(S,As)13, and Pd3(Sb,As) were recognized as microinclusions in isoferroplatinum and on the surface of its grains. It is shown that the studied PGMs are derived from rocks of ultramafic formations: (1) vein pyroxenites, harzburgites, and dunites of metamorphic and cumulative complexes of the most depleted peridotite varieties of the suprasubduction wedge of island-arc ophiolites and (2) vein pyroxenites of cumulative high-pressure ultramafic complexes of the basement of the ensialic island arc and products of evolution of suprasubduction mantle melts. In terms of the contents of platinoids, the compositions of isoferroplatinum from explosive breccias are divided into four groups: group I: isoferroplatinum of fluid-metamorphogenic genesis from harzburgite, group II: isoferroplatinum of fluid-metamorphogenic genesis from dunites and magmatogenic-fluid-metasomatic genesis from vein pyroxenites; group III: isoferroplatinum of magmatogenic genesis from chromitites of dunites of the cumulative complex; and group IV: isoferroplatinum with an elevated Pd content, which is likely derived from the melt formed by explosive breccias. Three scenarios of PGM occurrence in the fluid-saturated andesite–dacite melt of explosive breccias at the Poperechnoe deposit are discussed: (1) directly from early ultramafic complexes in suprasubduction settings; (2) from the reservoir of ancient platinum placer deposits; and (3) from a mantle wedge above the Mesozoic subduction zone during the generation of initial island-arc melts. The first two petrogenetic models suggest "rejuvenation" of the 190Pt–4He age of isoferroplatinum grains as a result of the thermal effect of the andesite–dacite melt to the age of 125 ± 21 Ma. The third geodynamic scenario suggests that the Lower Cretaceous age of isoferroplatinum marks the processes of metamorphogenic-metasomatic transformation of the dunite–harzburgite mantle wedge and probably corresponds to the age of the subduction magmatism at the Poperechnoe Deposit in particular and within the Lesser Khingan terrane as a whole. PGM associations in andesite–dacite breccias of the Poperechnoe Deposit are a new type of potentially meaningful noble-metal mineralization in the Russian Far East, while explosive breccias themselves (fluidoliths) can serve as a criterion to search for lode and placer platinoid deposits of volcanogenic-explosive genesis in the territory of the Russian Federation. [ABSTRACT FROM AUTHOR]

Based on new ideas, the most studied sections of the Jurassic deposits have been described along the structural–formational zones within the Mongol–Okhotsk Fold System from the Upper Amur to the Sea of Okhotsk. The presented modern ideas on the geology of this region may provide a reliable base for geodynamic and mineragenic reconstructions. [ABSTRACT FROM AUTHOR]

The physical properties of rocks from the western Okhotsk region were studied and petrophysical maps were constructed to highlight the petrophysical features of tectonic elements of the territory. Petrophysical heterogeneities and anomalies of the respective geophysical fields were compared. The relationship between magnetic anomalies and subsurface rock complexes has been established only for the Mesozoic volcano-plutonic structures of the Okhotsk-Chukotka volcanic belt and partly for the Yudoma–Maya lithotectonic zone. In the ancient blocks of the Aldan–Stanovoy shield and the Uchur–Maya plate, the magnetic anomalies are mainly associated with activation of tectonic–magmatic processes and, to a lesser extent, with the magnetic properties of definite rocks. Inverse relationships have been established between the gravity anomalies and rock density anomalies within the regional gravity low (Tyrkan and South-Verkhoyansk gravity fields) and in the Vilyui syneclise, where gravity high corresponds to the low-density domains. [ABSTRACT FROM AUTHOR]

Rare-earth element (REE) mineralization in weathered granites of Primorye is localized in the basement rocks and rocks surrounding coal-bearing basins, which have been recently deformed and undergone argillic metasomatism. It was shown that the clay material from the zones of intense argillization can be a source of deficient REE and yttrium. The ion-sorbed and carbonate REE+Y species in them in combination with the clay composition of most of the ores make it possible to use inexpensive and low-toxicity salt and hydrochloric acid solutions during heap leaching. [ABSTRACT FROM AUTHOR]

Identification of magma sources and their role in the origination of basaltic magmas still remains one of the fundamental petrological problems. Based on new comprehensive isotope–geochemical and mineralogical data, the contribution of a pyroxenite mantle source was recognized for the first time for Oligocene basalts in the northern part of the East Sikhote Alin volcanic belt. The most important indicators of this source are significant variations in the first-row transition elements ratios (Zn/Fe = 11–17 and Zn/Mn = 6–10), Cr/Ni (1.8–6) and the Ni concentration (2000–3600 ppm) in olivine. The behavior of LIL elements suggests the presence of amphibole in a pyroxenite protolith. The obtained data can be used for the correct reconstruction of the magma generation and geodynamic environment in this territory in the Late Cenozoic. [ABSTRACT FROM AUTHOR]

The proposed complex Parameter of River Network Self-similarity (PRNS), which is a combination of the exponents in the equations for distribution of channel lengths, the fractal dimension of channels, and the fractal dimension of points of change of the order of the channel, matches neotectonic movements more accurately. A comprehensive analysis of the self-similarity of the southern Sikhote-Alin River network model derived from the Digital Elevation Model (DEM) based on the Shuttle Radar Topography Mission image (SRTM) has been performed. Comparison of the results of morphostructural and fractal analyses showed the good consistency of these two methods. The relative PRNS maxima coincide with areas with the largest amplitude of ascending neotectonic movements (increment of relief), while the minima coincide with the areas either with the lowest increment of relief or with greatest erosion rates. Most of the crustal earthquakes are confined to the boundaries between PRNS relative maxima and minima, that is, uplifts are surrounded by seismic areas, which is due to the block nature of neotectonic vertical movements. [ABSTRACT FROM AUTHOR]

The Sikhote-Alin orogenic belt is a key area for understanding the evolution of the lithospheric plate interaction in the East Asian paleocontinent margin. At the same time, only limited and fragmentary precision isotope–geochemical and geochronological data are available for this region. New age data on the Early Paleogene magmatism supplement the available material and substantiate a specific Middle Paleocene–Early Eocene magmatic stage (60.5–53.0 Ma) dominated by A-type acid rocks in the southern Russian Far East during the geodynamic reconstruction of the continental margin. [ABSTRACT FROM AUTHOR]

The most studied sections of the Triassic sequences in the lithotectonic zones along the Mongol–Okhotsk fold system from Eastern Transbaikalia to the Sea of Okhotsk are described. Changes in the composition, thickness, and characteristic biota are traced. Transgressive and regressive evolution stages are defined. The presented modern ideas on the geology of this region can serve as a reliable basis for geodynamic and metallogenic reconstructions. [ABSTRACT FROM AUTHOR]

Geochronological dating was performed on the detrital zircons of 20 sedimentary rock samples from the Khabarovsk, Samarka, and Zhuravlevka–Amur terranes in the northern Sikhote-Alin Orogenic Belt to establish that (1) the isotopic 206Pb/238U ages of the youngest detrital zircon populations of two sedimentary rock samples from the Gorin (K1b) and Pioner (K1b-v) formations, as well as one sample from the Svetlorechensk massif (J3t), were significantly younger than the upper limit of the accepted stratigraphic age of these rocks and (2) sedimentary rocks accumulating in the accretionary prisms matrix of the Khabarovsk–Voronezh tectonostratigraphic zone in the Khabarovsk Terrane and turbidites in the Gorin tectonostratigraphic zone pull-apart basin of the Zhuravlevka–Amur Terrane were derived from sources located within the eastern part of the Central Asian Belt. The source of sedimentary rocks accumulating in the turbidite matrix of the accretionary prisms in the Anyui tectonostratigraphic zone of the Samarka Terrane and turbidites in the pull-apart basin of the Koppi–Luzhki tectonostratigraphic zone of the Zhuravlevka–Amur Terrane was found in the North China Craton. [ABSTRACT FROM AUTHOR]

The 190Pt-4He age of isoferroplatinum from andesitic fluid-explosion breccias (fluidolites, a new type of platinum-bearing rock) of the Poperechnoye deposit (Malyi Khingan, Russia) was estimated as 125 ± 21 Ma. This age correlates well with peak magmatic activity in the eastern Central Asian orogenic belt caused by upwelling of slab-window asthenosphere in a transform continental margin setting. [ABSTRACT FROM AUTHOR]

The first paleomagnetic and petrochemical data on the Lower Cretaceous sedimentary rocks of the Komsomolsk Series from the Zhuravlevka–Amurian turbidite paleobasin are presented. The rocks are collected in coastal outcrops of Sakhalin Bay (54.09° N, 140.05° E). The studies reveal that (1) the petrochemical characteristics of the sedimentary rocks of the Gorinskaya and Pionerskaya formations (Berriasian–Valanginian) do not contradict the model of their formation in a setting of the transform continental margin; (2) the paleolatitude at which they attained pre-folding paleomagnetic direction (Dec = 303°, Inc = 27°, Ks/Kg = 6.2) was 10–18° N; (3) in the post-Valanginian time, before 95 Ma B.P., the block including these rocks moved northward by 3900–4800 km along the Eurasian transform continental margin at a mean rate of about 10–13 cm/yr. [ABSTRACT FROM AUTHOR]

The quantitative processing of gravimetric data is performed and the 3D density model is calculated for the southern part of the Russian margin of Eurasian continent. Based on the density model, new patterns of disjunctive tectonics at different depth levels are revealed and the position of the region at the global tectonic level is shown. It is established that the transition zone is an integrated lithospheric structure of the northeastern orientation, in which there are mantle blocks with the boundaries corresponding to the borders of depressions and major tectonic objects. The data obtained may be applied for refinement of the deep structure and paleogeodynamics of the studied area. [ABSTRACT FROM AUTHOR]

In southeastern Khabarovsk krai, in the basin of the Tumnin River, the foraminifera complex containing the characteristic species Ammosiphonia beresoviensis (Bulatova), represented by exclusively agglutinated shells, is revealed for the first time in sections of Albian deposits. In terms of composition and structure, the complex is closest to the associations widespread in the Albian in the Arctic paleogeographic zone. It differs from the coeval assemblages of Sakhalin and Japan in the absence of warm-water species. [ABSTRACT FROM AUTHOR]

The results of the study of natural gas in Peter the Great Bay from 2009 to 2014 are reported. The data on the distribution of natural gas in the water and bottom sediments are obtained. High concentrations of gas in the bottom water and sediments are registered in some areas of the bay. The probable sources of methane and other natural gases are suggested. [ABSTRACT FROM AUTHOR]

The fluidolites and genetically related igneous rocks of the Mokrusha area were formed as a result of the injection of the melt with a high proportion of the fluid component dominated by H2O, F, Cl, and hydrocarbons into the upper crustal layers. This particular had a significant impact on the mineralogical features of these rocks. In many aspects, in particular the mineralogy of the country rocks, the Paleocene explosive structures are similar to the lamproite pipes. The occurrence of rodingites and lamprophyre-like rocks in these structures, with prospects for commercial gold–palladium–platinum ore mineralization, is of special interest. [ABSTRACT FROM AUTHOR]

The sedimentation conditions and formation of the accumulative landscape of the Khanka Plain are reconstructed on the example of the floodplain deposits of the Mel'gunovka River. Two groups of processes are specified: soil formation (pedogenic stage) and alluvial sedimentation (lithogenic stage). It is revealed that the alternation of the lithogenic and pedogenic sedimentation stages on the floodplain mainly depended on the dynamics of climate humidity and that the temperature factor played a secondary role. The reconstructed climatic events of the second half of the Holocene correspond well to the colder and warmer periods on the GISP2 isotope curve. The correlation is the closest for the events of the Late Holocene, such as the warm periods of the 3rd-5th and 8th-10th centuries and the cold periods of the 6th and 14th-19th centuries. [ABSTRACT FROM AUTHOR]

Complex mineralogical, geochemical, and geochronological studies of the gabbroids from the Dzhigdinskii Massif located in the western part of the Dzhugdzhur-Stanovoy Superterrane are performed. It is established that the age of the rocks from the Dzhigdinskii Massif is Middle Triassic (244 ± 5 Ma), rather than Early Archean, as was previously assumed. The age of the Dzhigdinskii Massif is close to the age of the formation of the other Triassic gabbroid massifs, such as the Amnunaktinskii (~240 Ma), Lukindinskii (~250 Ma), and Luchinskii (~248 Ma) in the southeastern environ of the North Asian Craton. One of the stages in the formation of the Selenga-Vitim volcanoplutonic belt falls in this period as well. This indicates that the Selenga-Vitim volcanoplutonic belt, along with the granitoids and volcanic rocks, is composed of ultrabasic-basic and basic massifs and that this belt is superposed on the structures of the Selenga-Stanovoy Superterrane, as well as on the western part of the Dzhugdzhur-Stanovoy Superterrane. The gabbro, gabbro-diorite, and series of gabbro and gabbro-diorite with high sodic alkalinity from the Dzhigdinskii Massif show obvious geochemical features of duality, including combination of intraplate and super-subduction origin. In this relation, we can assume that the origin of the gabbroids of the Dzhigdinskii Massif is related to the detachment of the oceanic lithosphere and its subduction into the mantle with the formation of an “asthenospheric window.” [ABSTRACT FROM AUTHOR]

This paper presents data on the geological position, geochemistry, age, and isotopic characteristics of the granitoids of the southern part of the Voznesenka terrane, Southern Primorye (Muraviev-Amursky Peninsula and its vicinities). All of the studied granitoids were formed in three stages: the Ordovician, Silurian, and Permian. The Silurian and Permian ages of the granitoid intrusions have been previously determined (Ostrovorussky Massif, 432-422 Ma, and 250 ± 4 Ma, early and late associations, respectively; Sedanka massif, 261 ± 3 Ma). The granites of the Artem and Nadezhdinsky massifs define an U-Pb zircon age of 481 ± 6 and 452 ± 4 Ma, respectively. The geochemical and isotope data show mainly the crustal nature of the granitoids. Their formation was related to melting of relatively immature rocks of the continental crust (mafic-intermediate volcanic rocks). The Nd isotope composition of the granitods (TNd(DM-2) = 1.3 Ga) indicates the absence of the mature ancient crust at the basement of the southern Voznesenka terrane. The maximum contribution of mantle sources to the granite formation is recorded in the Permian associations. A comparison of the peaks of intrusive magmatism in the southern part of the Voznesenka terrane and adjacent territories suggests that the formation of the granitoids of the Muraviev-Amursky Peninsula and its vicinities was caused by the interaction of continental blocks with two oceanic basins: the Paleoasian (and its fragments) and Paleopacific ones. [ABSTRACT FROM AUTHOR]

The studied region is located at the junction between the Pacific and Central Asian seismoactive belts. Macroseismic data on earthquakes of this region are available for the last 150 years, while instrumental seismological observations began in the mid-20th century; however, the recurrence interval of strong earthquakes can be up to several centuries and even thousands of years. In this respect, many areas of the Amur region had been believed to be nearly aseismic until earthquakes occurred there. Paleoseismogeological studies of recent years have allowed the character of Holocene displacements to be estimated for some of the main regional structures. As a result, the main tendencies of the Late Quaternary geological evolution of the region remain uncertain and the potential seismogenerating structures are not completely known. Therefore the problem of revealing new zones and periods of seismic activity is topical for the entire Amur region. The importance of this problem is related to the weak degree of study of the region by contemporary methods of active tectonics, the intensive development of engineering infrastructure, which is vulnerable to seismic impacts, and the necessity of long-term seismic forecasting. The present work provides the results of paleoseismogeological studies of the active faults in the Amur region. On the basis of new data on the magnitude potential of seismogenerating structures based on the magnitudes of historical earthquakes and instrumentally recorded ones, we have estimated the seismic effects from strong deep-focus earthquakes and the attenuation coefficients and calculated radii of the first three isoseismals for crustal earthquakes. By using the methods of statistical modeling, we distinguish the periods when seismic effects increased from earthquakes with 2 ≤ M ≤ 6. It is shown that seismic hazard assessment should take into account the dynamics of the seismic regime, caused by the change of the earthquake source depth. It is found that the epicenters of earthquakes with 5 ≤ M ≤ 6 form non-crossing seismic zones in different phases of changes in the Earth’s annual rotation. [ABSTRACT FROM AUTHOR]

The Kiselyovka-Manoma accretionary complex, formed at the end of the Early Cretaceous, is a part of the Early Cretaceous Khingan-Okhotsk active continental margin. It is located at the front of the Amur accretionary complex and is composed of Jurassic-Lower Cretaceous oceanic volcanic-siliceous deposits. The structural study of this complex in the Lower Amur region hSas made it possible to clarify its overall structure and to subdivide the folds with different morphologies and orientations into five types. The analyzed folding sequence is compared to the folds of the Amur accretionary complex. The fold kinematics indicates various senses of motions that do not reveal systematic kinematic patterns of stacking of the accreted tectonic slices. [ABSTRACT FROM AUTHOR]

A great volume of original information on the formation of the ultrabasic rocks of the Siberian Platform has been accumulated owing to the study of melt inclusions in Cr-spinels. The inclusions show the general tendencies in the behavior of the magmatic systems during the formation of the ultrabasic massifs of the Siberian Platform, tracing the main evolution trend of decreasing Mg number with SiO2 increase in the melts with subsequent transition from picrites through picrobasalts to basalts. The compositions of the melt inclusions indicate that the crystallization conditions of the rocks of the concentrically zoned massifs (Konder, Inagli, Chad) sharply differ from those of the Guli massif. Numerical modeling using the PETROLOG and PLUTON softwares and data on the composition of inclusions in Cr-spinels yielded maximum crystallization temperatures of the olivines from the dunites of the Konder (1545-1430°C), Inagli (1530-1430°C), Chad (1460-1420°C), and Guli (1520-1420°C) massifs, and those of Cr-spinels from the Konder (1420-1380°C), Inagli (up to 1430°C), Chad (1430-1330°C), and Guli (1410-1370°C) massifs. Modeling of the Guli massif with the PLUTON software using the compositions of the melt inclusions revealed the possible formation of the alkaline rocks at the final reverse stage of the evolution of the picritic magmas (with decrease of SiO2 and alkali accumulation) after termination of olivine crystallization with temperature decrease from 1240-1230°C to 1200-1090°C. Modeling with the PLUTON software showed that the dunites of the Guli massif coexisted with Fe-rich (with moderate TiO2 contents) melts, the crystallization of which led (beginning from 1210°C) to the formation of pyroxenes between cumulate olivine. Further temperature decrease (from 1125°C) with decreasing FeO and TiO2 contents provided the formation of clinopyroxenes of pyroxenites. For the Konder massif, modeling with the PLUTON software indicates the possible formation of kosvites from picrobasaltic magmas beginning from 1350°C and the formation of clinopyroxenites and olivine-diopside rocks from olivine basaltic melts from 1250°C. [ABSTRACT FROM AUTHOR]

The Kiselyovka-Manoma accretionary complex formed at the end of the Early Cretaceous during subduction of the Pacific oceanic plate underneath the Khingan-Okhotsk active continental margin along the east of Eurasia. It is composed of Jurassic-Early Cretaceous oceanic chert, siliceous mudstone, and limestone that include a significant amount of basic volcanic rocks. The known and newly obtained data on the petrogeochemistry of the Jurassic and Early Cretaceous basalt from various parts of the accretionary complex are systemized in the paper. Based on the comprehensive analysis of these data, the possible geodynamic settings of the basalt are considered. The petrogeochemical characteristics provide evidence for the formation of basalt in different parts of the oceanic floor within the spreading ridge, as well as on oceanic islands far from the ridge. The basalts of oceanic islands are mostly preserved in the accretionary complex. The compositional variations of the basalts may be controlled by the different thickness of the oceanic lithosphere on which they formed. This is explained by the varying distances of the lithosphere from the spreading zone. [ABSTRACT FROM AUTHOR]

Graphitic and graphite varieties are distinguished in the carbonaceous shales of the Riphean Upper Nyatygran Subformation in the Melgin fragment of the Turan block, eastern Bureya Massif. The protolith of the graphitic shales had a terrigenous source related to island-arc volcanism. Pelagic sedimentation played a great role in the formation of the protolith of the graphite shale. These rocks were juxtaposed during the formation of an accretionary wedge on an active continental margin. The carbonaceous shales are characterized by high (>600 ppm) REE + Y contents, especially in the zones of brecciation and hydrothermal reworking. Detrial monazite enriched in LREE and MREE is the main carrier of REE mineralization in the graphitic shales. The main REE carrier in the graphite shales is REE phosphate (xenotime) formed during lithogenesis of sediments. Preliminary experimental treatment of the graphite shales of the Upper Nyatygran Subformation by ammonium hydrofluoride shows their potential for economic extraction of REE and Y. [ABSTRACT FROM AUTHOR]

The Bureya orogen is a special object among the geodynamic factors determining the high seismicity of the Lower Amur region. Its location and deep structure are studied on the basis of comprehensive geophysical and tectonic data. This orogen is a low-density lithospheric domain expressed by an intensive negative gravity anomaly and Moho sunken down to 40 km depth. Within the limits of this lithospheric structure, contemporary uplifting takes place to form a meridional dome peaking at more than 2000 m altitude. The position of the orogen in the regional structure gives us grounds to think that the Bureya orogen formed in the Paleogene, at the finishing stage of tectonic block movement along the Pacific margin represented by the NE-trending strike-slip faults of the Tang Lu Fault Zone. Compression was concentrated at the triple junction between the Central Asian, Mongolian-Okhotian, and Sikhote Alin tectonic belts. The meridional orientation of the Bureya orogen is associated with the parallel elongated Cenozoic depressions in the region. The united morphotectonic system may have formed resulting from lithospheric folding under horizontal shortening in the Paleocene-Eocene. The wavelength of the Lower Amurian fold system is 250 km, which is consistent with the theoretical estimates and examples of lithospheric folds in other regions. The contemporary activation of the Bureya orogen began in the Miocene, under the effect of the Amurian Plate front moving in the northeastern direction. As a result of shortening, the meridional cluster of weak (M ≥ 2.0) earthquakes formed along the western boundary of the orogenic dome. The most intensive deformations caused another type of seismicity associated with the activation-related uplift of the mentioned orogen. As a result, the so-called Bureya seismic zone formed above the apex of the dome, and it is here that the strongest regional earthquakes (M ≥ 4.5) occur. [ABSTRACT FROM AUTHOR]

Detailed geological observations and analytical studies make it possible to distinguish two groups of fluid-explosion breccias (FEB) in the Vysokogorskoe tin deposit of the Kavalerovo ore district. These breccias are assumed to be related to different stages of geological (geodynamic) evolution and played different roles in ore formation. The earlier breccias (79-69 Ma), which were altered by boron metasomatism and subsequent main tin mineralization, were most probably formed at the Cretaceous subduction stage. The later breccias (55-51 Ma) are syngenetic to the dacite (rhyolite) porphyry dikes of the Paleocene-Eocene transform stage. They were formed after precipitation of the majority of the cassiterite, but prior to the latest quartz-fluorite-carbonate stage of ore formation. According to the Sillitoe classification, the explosion breccias of the Vysokogorskoe deposit correspond to a magmatic-hydrothermal genetic type. They are characterized by multiple brecciation and intersection by small bodies of porphyritic rhyolites. [ABSTRACT FROM AUTHOR]

The spatial distribution of the epicenters and hypocenters is analyzed for earthquakes of 2 ≤ M < 6 that occurred in the northeastern segment of the Amur Plate in two phases of changes in the angular speed of the Earth's rotation. Groups of seismic events in the magnitude interval of 5 ≤ M < 6 are distinguished in the form of NE-trending seismic clusters regularly alternating along the plane of latitude. The seismic clusters are up to 1500 km long and 180-240 km wide and cover the seismic zones with different geodynamic and seismotectonic conditions of seismicity origination. In terms of the epicentral distributions for earthquakes with 2 ≤ M < 4, seismic activity zones are distinguished; these zones are seen as seimolineaments coupling the Tan Lu seismic zones and the eastern flanks of the latitudinal seismic zones. A scheme of distinguishing the compression and extension zones from the spatial clusters of earthquakes with 5 ≤ M < 6 in two phases of changes in the angular speed of the Earth's rotation is proposed. This scheme satisfactorily agrees with the model of seismotectonic reconstructions of the compression-extension fields and axes. [ABSTRACT FROM AUTHOR]

The Yakchi chert-volcanogenic formation is differentiated at the base of the stratigraphic succession in the Khor-Tormasu subzone of the Central Sikhote-clin structural-formational zone or the Samarka terrane of the Jurassic accretionary prism. The paper considers the results of biostratigraphic study of its deposits and petrogeochemical studies of its basalts. A tectonically disrupted sequence of the Yakchi Formation is restored on the basis of fossil conodonts and radiolarians, and its Late cermian-Middle Jurassic age is determined. The authors interpret the resulting stratigraphic succession in terms of changing depositional settings on the moving oceanic plate and recognize events of the ocean history recorded in it. Chert accumulated on the oceanic plate in pelagic canthalassa/caleopacifica from the Late cermian through to the Middle Jurassic. Deposition of siliceous claystone in the Late cermian-Early Triassic reflects the decline in productivity of radiolarians and a long anoxic event in Panthalassa. Chert accumulation resumed in the Triassic and persisted in the Jurassic, and it was interrupted by the eruption of basalts of different nature. Formation of the Middle-Late Triassic oceanic intraplate basalts likely occurred on the thick and old oceanic lithosphere and that of the Jurassic basalts on the thin and newly created lithosphere. In the Middle Jurassic, chert accumulation was replaced by accumulation of tuffaceous siltstone at a subduction zone along the csian continental margin. The middle Bathonian-early Callovian age of this siltstone closely predates accretion of the Yakchi Formation. The materials of the upper layer of the oceanic plate that formed over 100 million years in different parts of the ocean and on the lithospheric fragments of different ages were accreted to the continental margin. The bulk of the accreted material consists of oceanic intraplate basalts, i.e., fragments of volcanic edifices on the oceanic floor. accretion of this western part of the Khor-Tormasu subzone occurred concurrently with accretion of the southeastern part of the Samarka subzone in Primorye, which clarifies the paleotectonic zonation of the Central Sikhote-Alin accretionary prism. The cataclastic gabbroids and granitoids, as well as the clastic rocks with shallow-marine fossils in the Khor-Tormasu subzone, are considered as possible analogues of the Okrainka-Sergeevka allochthonous complex. [ABSTRACT FROM AUTHOR]

Petrophysical characteristics are determined for the rock complexes of the Okhotsk margin within the continent-ocean transition zone. Petrophysical maps showing the major inhomogeneities of the main tectonic elements of the studied area are constructed. Petrophysical inhomogeneities and the corresponding geophysical field anomalies are compared. A relationship between the magnetic field anomalies and subsurface rock complexes is revealed. The gravity field anomalies are related to deep inhomogeneities and are almost independent of the subsurface rock complexes of relatively low thickness. [ABSTRACT FROM AUTHOR]

The geochemical features of typical representatives of ferromanganese deposits are studied in the eastern Bureya and Khanka massifs (Russian Far East). Based on the major-, trace-, and rare-earth element distribution, the hydrothermal-sedimentary (with hydrogenic component) nature of their mineralization is established and the geodynamic setting and depth of ore formation are estimated. The differences in the depth and redox conditions of ore formation resulted in the metallogenic zonation of the Khingan block (Bureya Massif), which is expressed in a westward change in ore composition from the magnetite ores of the Kosten'ga-Kimkan zone to the hematite-magnetite and iron-manganese ores of the South Khingan zone. The conclusions about the participation of hydrothermal sources in the formation of ore mineralization of the studied deposits and the specifics of their localization require revision of the strategy of exploration and evaluation of ferromanganese ores in the southern Far East. [ABSTRACT FROM AUTHOR]

On the basis of partially published original data on the correlation of Permian sections, the stage boundaries of the standard (SSS) and general (GSS) stratigraphic scales are traced in different paleogeographic regions and climatic belts using reliably substantiated correlation levels. The analysis of the mixed west and east boreal Kungurian-early Ufimian and Middle Permian boreal-peri-Gondwanan-Tethyan brachiopod assemblages from southern Primorye using different stratigraphic methods (biostratigraphy, magnetostratigraphy, event-stratigraphy) and carbon isotope data make it possible for the first time to define five event-correlation levels traceable in remote paleogeographic regions. Presumable analogs of the Sheshma deposits of the GSS Ufimian Stage with the Kazanian biota established in Primorye and traced through the Boreal realm are attributed to the Middle (Biarmian) Series of the Permian System. The magnetostratigraphic method combined with strict biostratigraphic control allows correlation of the Roadian, Capitanian, Wuchiapigian, and Changhsinian stages and their boundaries in the standard stratigraphic scale with the Kazanian, Severodvinian, and Vyatkian stages (and boundaries) in the general stratigraphic scale and with similar units in the Tethyan scale to be specified. [ABSTRACT FROM AUTHOR]

Based on the data of magnetotelluric sounding (MTS) carried out in the Middle Amur sedimentary basin's northwestern side along three profiles running across the strike of the basin, geoelectric sections down to the 3 and 6 km depths were constructed. Based on the MTS data interpretation with the seismic (seismic reflection method-common depth point), electrical survey (vertical electrical sounding, differential-normalized electrical exploration), and drilling data involved, the complex geological-geophysical sections were constructed. Insight into the structure of the sedimentary cover and basement was obtained, the anomalous zones were distinguished, and the electrical properties of these zones were defined. [ABSTRACT FROM AUTHOR]

Carbonaceous matter (CM) in shales of some deposits and occurrences of the Russian Far East has been studied by scanning and transmission electron microscopy, Raman spectroscopy, and X-ray phase and differential thermal analyses. It was shown that the carbonaceous matter in the high-temperature shales (amphibolite facies) of the Soyuznoe deposit is represented by holocrystalline graphite, while the low-temperature (greenschist facies) shales of the Sutyr and Kimkan sequences contain mainly nanocrystalline graphite. It was substantiated for natural objects that platinum is assimilated by graphite at high temperatures. This should be taken into account in planning the prospecting works, as well as in developing a technique for enrichment of carbonaceous ore, because high-temperature carbonaceous shales with holocrystalline graphite are promising for Pt, unlike their low-temperature analogues with nanocrystalline graphite. [ABSTRACT FROM AUTHOR]

The early Jurassic-Early Cretaceous tectonic environments were reconstructed for the first time on the basis of the study of sandstones from the Soloni-Urgal interfluve (Bureya sedimentary basin, Far East). The mineralogical-petrographic and lithochemical studies revealed that the sandstones are mostly quartz-feldspathic and feldspathic graywackes of acid composition with less common litites, graywacke arkoses, and arkoses. It was shown that the Lower-Middle Jurassic sediments were formed in active continental margin and continental volcanic arc settings, while the Upper Jurassic-Lower Cretaceous sediments were accumulated in a passive continental margin setting. Orogenic events in the Toarcian-Aalenian, Late Bajocian, and Late Oxfordian-Kimmeridgian led to sedimentation gaps. [ABSTRACT FROM AUTHOR]

The Kiselevka-Manoma Complex, the youngest accretionary complex in the Russian Far East, is composed of Jurassic-Lower Cretaceous pelagic and hemipelagic oceanic deposits. The radiolarian biostratigraphic study made it possible to refine the stratigraphy of the upper portion of the siliceous sediments from the northeastern fragment of this accretionary complex in the vicinity of the Kiselevka settlement in the Lower Amur region. The transition from pelagic siliceous to hemipelagic siliceous-clayey sedimentation was established within the interval from the Late Barremian to the Middle Aptian in different parts of the complex. The age of the accretion of the oceanic rocks is defined as postmiddle Aptian. [ABSTRACT FROM AUTHOR]

Hydrothermally altered rocks and their relation to gold mineralization at the Svetloe deposit in the Ul'ya Trough, western sector of the Okhotsk-Chukotka volcanic belt, are studied. The rock composition and style of mineralization are typical of acid-sulfate type deposits. The hydrothermally altered rocks of the deposit are medium-temperature secondary quartzites with developed alunite facies. The upper structural level in the massif of secondary quartzites is made up of a sheetlike body 30 km in area and up to 300 m thick with gentle (5-10°) periclinal bedding relative to the arcuate axis of the volcanic range. Below the sheet, there are a number of local steep mostly carinate zones and small (a few hundreds of square meters) multilayered trough-shaped structures, the foot of which is located 100-150 m under the secondary quartzite sheet. All structures of the lower level are restricted to the volcanic range pericline, marked by elevated thicknesses of monoquartzites, and have a gradual transition to the sheetlike part of the massif. The massif of secondary quartzites shows symmetrical zoning. The central zone of the sheetlike body is composed of alunite quartzites framed by dickite varieties. Down the section, the latter grade into hydromica and hydromica-montmorillonite argillic rocks. Monoquartzites form axial zones in the structures of the lower level. In the blanketlike part of the deposit, monoquartzites occur as rare thin lenses and interlayers spatially related to local structures of the lower level. Gold mineralization at the deposit associates with porous monoquartzites. Gold precipitated after quartzite formation during infilling of pores and cavities with colloform silica with barite, and hypogene jarosite. [ABSTRACT FROM AUTHOR]

This paper addresses the hypotheses of the formation of the brown loams widely spread in the zone with hummocky relief within the intermontane Razdol'noe-Khanka Depression. These hypotheses were proposed in the 1970s-1980s. The accumulation of information on the loess formation in southern East Siberia, as well as obtaining new analytical data on the microtextural, mineralogy, and major and trace-element composition of the brown loams, and the comparative analysis of these deposits provided for the formulation of a more substantiated view concerning the place of the brown loams in the group of loess-type rocks. [ABSTRACT FROM AUTHOR]

Tens of gold deposits of different genetic classes (endogenous and exogenous), groups, and types were recognized in cratons, orogenic belts and magmatic arcs of the Transbaikal region and Russian Far East (T and RFE), evaluated to different extents, explored, and prepared (or are being prepared) for exploitation. The formation of the noble-metal mineralization of the region was related to the activity of different genetic types of ore systems, which were responsible for the magmatogenic- and metamorphogenic-hydrothermal, hydrothermal-sedimentary-metamorphogenic, and hydrogenic deposits. The concepts of geologic-genetic and economic types of gold deposits serve as the basis for such fundamental notions of metallogenic analysis as ore formations and geologic-economic types of mineralization. In recent years, the researchers of gold deposits (especially large ones) arrived at conclusions of their polygenous and polychronous formation, which is confirmed sometimes by the sufficiently long-term (up to hundreds of millions of years) conjugate development of ore formations, sedimentation, metamorphism, and magmatism of diverse geodynamic natures. The polygenous nature and significant duration of the formation of the gold deposits affect their economic significance and should be taken into account in the metallogenic forecasting and assessment of the potentially ore-bearing areas. [ABSTRACT FROM AUTHOR]

The role of the lateral structure of the lithospheric mantle in the seismotectonics and seismicity of the southern part of the Russian Far East has been investigated. The positions of the epicenters of all the major earthquakes in Sakhalin (M ≥ 6.0), as well as in the Amur region and the Primorye zones (M ≥ 5.0), are defined by the boundaries of the Anyui block of highly ferruginous mantle, which lies at the base of the Sikhote-Alin area. Three cycles of large earthquakes are recognized in the region: the end of the 19th-beginning of the 20th century, the mid-20th century, and end of the 20th-beginning of the 21st century. In the seismic zone of the Amur region (hereafter, the Amur seismic zone), the epicenters of the large earthquakes in each cycle migrate from the SW to NE along the Tan-Lu fault megasystem at a rate of 30-60 km/yr. The specific features of the seismicity of the region are explained by the repeated arrival of strain waves from the west. The waves propagate in the upper part of the mantle and provoke the activation of the deep structure of the region. The detailed analysis of the earthquakes in the Sikhote-Alin area (M ≥ 4.0) in 1973-2009 confirmed the clockwise tectonic rotation of the mantle block. The characteristics of the Primorye zone of deep-focus seismicity at the Russia-China boundary are stated. Since 1973, 13 earthquakes with M ≥ 6.0 have been recorded in the zone at a depth of 300-500 km. This number of earthquakes is at least twice as many as the number of large deep-focus earthquakes elsewhere in the Sea of Japan-Sea of Okhotsk transition zone. The unique genesis of the Primorye seismic zone is related to the additional compression in the seismofocal area due to the creeping of the Anyui mantle block onto the subduction zone during its rotation. The geodynamic implications of the seismotectonic analysis are examined, and the necessity of division of the Amur plate into three geodynamically independent lithospheric blocks is substantiated. [ABSTRACT FROM AUTHOR]

The supposedly second finding of rare arsenosilicate cervandonite-(Ce) in the world is characterized. The mineral was recognized in the ore-bearing metasomatic rocks of the Berezitovoe gold-base metal deposit (Upper Priamurye, Russian Far East) in association with quartz, biotite, muscovite, orthoclase, garnet (almandine-spessartine), tourmaline, basic plagioclase, and sulfides. The cervandonite is represented by optically homogeneous and heterogeneous aggregates with visible crystals from 10 fum to 0.1–0.3 mm in size. Based on the microprobe analysis, the average chemical composition of the homogeneous cervandonite-(Ce) aggregates is as follows (wt %): Ce2O3 - 13.00, La2O3 - 5.70, Nd2O3 - 5.20, Pr2O3 - 1.41, Y2O3 - 0.77, Sm2O3 - 0.77, Eu2O3 - 0.23, Gd2O3 - 0.54, Dy2O3 - 0.31, ThO2 - 1.12, UO2 - 0.30, TiO2 - 12.86, Al2O3 - 9.24, Fe2O3 - 8.93, FeO - 2.68, CaO - 0.14, SiO2 - 19.98, As2O3 - 16.19. The comparative study of the cervandonite-(Ce) from the Berezitovoe deposit and the analogous minerals from the Alpine mica gneiss of Mt. Pizzo Cervandone (Central Alps) showed that the former mineral can be assigned to a new variety of cervandonite-(Ce) in terms of its compositional features. This variety is characterized by an ordered stoichiometric composition corresponding to the simpler theoretical formula (Ce,Nd,La)(Fe3+, Fe2+, Ti4+, Al)3 (Si2As3+)3O12. [ABSTRACT FROM AUTHOR]

It is shown that the deep structure of the lithosphere played a decisive role in the recent deformations and seismicity in the Far East. The regional variations in the composition of the mantle xenoliths and Neogene-Quaternary basalts provided grounds for mapping the NE-extending wedge-shaped block of the Fe-rich mantle at the base of Sikhote Alin. Its boundaries continue the Yilan-Yiton and Fushun-Mishan strike-slip faults of the Tan-Lu zone, along which this mantle block was displaced along the continental margin in the Jurassic-Cretaceous. The localization of strong (M ≥ 5.0) earthquake epicenters in the Amur region shows that such a mantle structure determines the key features of the regional deformations and seismotectonics. Under the dominant western compression due to the Amur Plate’s motion, the mantle wedge is extruded in the northeastern direction to provide an additional stress at the Okhotsk Plate boundary. This process resulted in the formation of the Sakhalin high-seismicity zone at the front of the mantle block. In its characteristics, the zone is similar to the convergence area between the Indian and Eurasian plates. In both cases, the main deformation and seismicity features were caused by the horizontal pressure of the tectonic block, the frontal part of which is marked by regularly alternating compression and extension zones. In Sakhalin, strong earthquakes with M ≥ 6.0 are confined to the seismic suture 50 km wide with concentrated compression. This structure is discordant relative to the main faults of the island, being parallel to the front of the mantle wedge. The two migration cycles established for the Sakhalin earthquakes with M ≥ 6.0 correspond to periods of 1907–1971 and 1995–2007. During both cycles, the first shocks occurred in the north and subsequently migrated in the southeastern direction simultaneously decreasing in the depths of the earthquake foci. The systematic migration implies that asymmetrical compression is responsible for both the extrusion of the mantle wedge and its southeastward clockwise rotation. The latter plays the decisive role in the initiation of strong earthquakes on Sakhalin. [ABSTRACT FROM AUTHOR]

The formation of large accumulations of Au and Sn and independent metallogenic provinces, zones, and clusters is based on both the heterogeneous structure of the Earth’s crust and the upper mantle, which results in the diversity of the sources of magmas and ore-forming elements, and the differences in the geochemical properties of these elements. During the transport of Au and Sn by fluid-magma columns, the mobility of the metals is affected and polarized by their different affinity to the silicate-forming clusters of melt, oxygen, and other strong oxidizers. This influence promoted the divergence of the migration paths of these elements to ore concentration levels. By the moment of the release of the ore-forming fluids, the metallogenic characteristics of the melts with contrasting redox potentials were usually already established, which is supported by the preferential association of the tin and gold mineralization with ilmenite-and magnetiteseries granitoids, respectively. Combined concentrations of the metals could potentially be produced by fluid-magma systems with transitional degrees of the melt oxidation. However, even in such cases, the simultaneous concentration of tin and gold was hampered by the opposing redox reactions of the formation of the most common minerals of these metals: the main tin migration species — Sn2+— had to be oxidized with the formation of cassiterite, whereas the mobile gold species — Au+ or Au3+ — had to be reduced with the formation of native gold. Perhaps, this is why the combined concentrations of tin and gold are characterized by the dominance of one of the metals with a tendency for their accumulation in mineral complexes of different stages. The redox state of the melts controlling the migration activity of the metals depended on the duration of the movement of the fluid-magma columns toward the levels of ore concentrations. This parameter is a function of the depths of their generation and their movement velocity, which were controlled by the geodynamic conditions. [ABSTRACT FROM AUTHOR]

This study presents a brief description of the tectonic framework and Mesozoic-Cenozoic geodynamic evolution of the East Asian continental margin. The analysis of the geodynamic evolution enabled us to classify the oil-and-gas-bearing and potentially oil-and-gas-bearing basins within the studied area into three groups: (1) the continental paleorift and suprarift depressions; (2) the passive continental paleomargins; and (3) the active continental paleomargins, island arcs, and marginal seas collectively classified as subduction-related basins. The basins in the first two groups were formed by divergence of the lithospheric plates, whereas the basins of the third group were formed by plate convergence. The analysis of the structure, evolution, and hydrocarbon potential of each of the basins provided the basis for comparing the eastern Russian and SE Asian basins. Despite much higher hydrocarbon potential of SE Asia, which can be explained by the confinement to the “cluster” of sedimentary basins at the intersection of different-type continental margins, the conclusion was reached that extensive exploration activity may help to increase the density of the resources in the Russian Far East. [ABSTRACT FROM AUTHOR]

Being a relatively simple geological discipline, biostratigraphy requires accuracy and sequential logic. The incorrect use of the biostratigraphic method and inaccurate interpretation of biostratigraphic data lead to a distorted understanding of regional tectonics. Frequently occurring errors are analyzed using three recently published works on biostratigraphy of accretionary complexes in the Russian Far East as an example. [ABSTRACT FROM AUTHOR]

Palynological complexes from the coaliferous Talyndzhan and Dublikan formations of the Bureya sedimentary basin are analyzed. The palynological assemblage from the upper part of the Talyndzhan Formation is characterized by dominant gymnosperms largely close to Pinaceae and Ginkgocycadophytus. The content of ferns is insignificant against the background of their relatively high taxonomic diversity. The assemblage is marked by the last occurrence of Staplinisporites pocockii, Camptotriletes cerebriformis, C. nitida, and Cingulatisporites sanguinolentus spores typical of the Late Jurassic palynofloras. The palynological assemblage from the Dublikan Formation is dominated by Pteridophyts representing mainly by Cyathidites and Duplexisporites. In addition to the conifer, the role of Classopollis increased among the gymnosperms in this assemblage. It also includes the first-appearing Stereisporites bujargiensis, Neoraistrickia rotundiformis, Contignisporites dorsostriatus, Duplexisporites pseudotuberculatus, D. rotundatus, Appendicisporites tricostatus, and Concavissimisporites asper. These sporomorphs are characteristic of the Berriasian palynofloras. Thus, the Jurassic-Cretaceous boundary is most likely located between the Talyndzhan and Dublikan formations. [ABSTRACT FROM AUTHOR]