THE LOWER SILURIAN TERRIGENOUS DEPOSITS OF THE LAOELING-GRODEKOVO TERRANE (SOUTH PRIMORYE): MATERIAL COMPOSITION AND FORMATION SETTINGS

This paper studies the original results of the material composition analysis of the Early Silurian terrigenous deposits of the Kordonka formation of the Paleozoic – Early Mesozoic Laoeling-Grodekovo terrane of the South Primorye. The research is aimed at reconstructing paleogeodynamic setting of the deposition of sediments of the formation, and determining the type and mother rock composition of the feed sources based on the complex genetic interpretation of the material composition of rocks. It was established that mineralogically and geochemically formation of the rocks correspond to the typical graywackes and represent petrogenic or “first cycle” rocks formed mainly through the source rock failure. They are characterized by a low maturity, low lithodynamic recycling rate of mother rocks and their rapid burial. The interpretation of the results of the complex study of the material composition of the rocks was carried out on the basis of its comparison with the compositions of ancient rocks and modern sediments formed in the well-known geodynamic settings. The obtained data indicate that deposits of the Kordonka formation accumulated in a sedimentary basin connected with an oceanic island arc. Being built by basic and intermediate volcanic rocks as well as by igneous and sedimentary rocks that constituted its base, this island arc was the source area that supplied clastic material to the aforementioned sedimentary basin.

GEODYNAMICS AND MAGMATISM OF THE PACIFIC-TYPE TRANSFORM MARGINS. ASPECTS AND DISCRIMINANT DIAGRAMS

Transform margins represent lithospheric plate boundaries with horizontal sliding of oceanic plate, which in time and space replaced the subduction related convergent margins. This happened due to: spreading ridge–trench intersection (California; Queen Charlotte–Northern Cordilleran, West of the Antarctic Peninsula, and probably the Late Miocene–Pleistocene Southernmost South America) or ridge death along continental margin (Baja California); change in the direction of oceanic plate movement (Western Aleutian–Komandorsk; Southernmost tip of the Andes); and island arc-continent collision (New Guinea Island). Post-subduction magmatism is related to a slab window that resulted either from the spreading ridge collision (subduction) with a continental margin or slab tear formation, or slab break-off after subduction cessation due to other reasons. Igneous magmatic series formed in consequence of these events show diversity of tholeiitic (sub-alkaline), alkaline or calc-alkaline, high-alumina and adakitic rocks. The comprehensive geochemical dataset (more than 2400 analyses) on igneous rocks of the model transform and convergent geodynamic settings allowed to substantiate the most informative triple diagrams for the petrogenic oxides TiO2 × 10 – Fe2O3Tot – MgO and trace elements Nb – La– Yb. Mostly approved for the rock compositions with SiO2 < 63 wt. %, the new plots are capable of distinguishing igneous rocks formed above zones of subduction at an island arc and continental margin (related to convergent margins), from those formed in the tectonic setting of transform margins along continents or island arcs.

MESOZOIC RADIOLARIANS FROM RHYTHMICALLY LAYERED SEDIMENTS OF THE RIMSKY-KORSAKOV ISLANDS (PETER THE GREAT BAY, JAPAN SEA) AND THEIR SIGNIFICANCE FOR DETERMINING THE TRIASSIC-JURASSIC BOUNDARY

The results of the biostratigraphic study based on the radiolarian analysis of the rhythmically layered terrigenous deposits from the Islands of the Rimsky-Korsakov Archipelago (Peter the Great Bay, Japan Sea) have been presented. These deposits are most similar to the medium-grained turbidites. For the first time the distribution and stratigraphic division of the boundary sediments of the upper Triassic and lower Jurassic separated by a marking layer were substantiated in the research area. On the basis of comparisons with isochronous zonal units of the Pacific and Tethyan areas in the upper Triassic sediments of the studied sections, layers with Globolaxtorum tozeri (upper Rhaetian) were established, and in the lower Jurassic zone Pantanellium tanuense Zone (Hettangian) was traced and layers with Parahsuum simplum (Sinemurian – Pliensbachian) were established.

CRUST AND UPPER MANTLE IN THE ZONE OF JUNCTION BETWEEN THE CENTRAL ASIAN AND PACIFIC FOLD BELTS

Spatial distributions of gravity sources and density contrast of geological media, which is reflected by the values of parameter μz , into the crust and upper mantle of Northeast China are analyzed. Features of rheological layering of the tectonosphere and deep spatial relationships of tectonic structures (cratonic blocks, marginal terranes, and sedimentary basins) are defined. In the density contrast distributions the formal signs of Paleozoic subduction of the North-China Craton and Mesozoic subduction of the Pacific Plate under the Amurian Plate were revealed. Crustal deformations are in sharp contrast with upper mantle deformations in structural planes resulting from different directions of tectonic stresses in the Paleozoic and Mesozoic. Thrusting of marginal terranes (Jamusi, Khanka) over the Amurian Plate lithosphere is revealed. Rheology and deep structure of North East China bear many similarities to other regions of the Pacific western margin in Asia and Australia.

APATITE-ALBITE METASOMATITES (ACEITES) OF THE EASTERN ALDAN-STANOVOY SHIELD

The paper summarizes the findings of research on Riphean ore-bearing apatite-albite metasomatites (aceites) identified in metamorphic, volcanic and intrusive rocks in the eastern Aldan-Stanovoy shield. The characteristic features of lithological and structural control of aceites, their mineral and petrochemical composition, geochemical associations, ontogeny, metasomatic zoning, and geochemical specialization are outlined. Aceites in metamorphic rocks are assigned to the albite-chlorite-apatite facies and in igneous rocks to the albite-apatite facies. Apatite-albite metasomatites host mineralization of two types: uranium (in aceites after metamorphic rocks) and uranium – rare earth element – rare metal (in aceites after volcanic and intrusive rocks).

APPLICATION OF ONE-DIMENSIONAL PALEOTEMPERATURE MODELING TO ESTIMATE THE HYDROCARBON POTENTIAL OF CRETACEOUS SEDIMENTS OF THE MIDDLE AMUR SEDIMENTARY BASIN

The prospects of oil and gas content of the Cretaceous-Paleogene deposits of the Middle Amur sedimentary basin within the Pereyaslavsky graben are clarified on the basis of updated data on the tectonic-stratigraphic complexes of the basin using the method of one-dimensional paleotemperature modeling. It is established that throughout the history of formation of the studied part of Pereyaslavsky graben hydrocarbon generation could occur in lower Cretaceous sediments of the Assikaevsky and Alchansky/Strelnikovsky suites. The gas generation conditions for the Assykaevsky formation are still maintained.

THE WAVE GEODYNAMIC IMPACT OF TECTONIC PROCESSES ON THE AMURIAN PLATE

The analysis of data on the migration of earthquakes and slow deformations from the Indo-Eurasian collision and the Western Pacific subduction zones is given, and the wave “geodynamic impact” of these tectonic processes on the Amurian plate and surrounding structures is shown. The interaction and a relative contribution of collision and subduction to the recent geodynamics of the Amurian plate are discussed. A scheme is constructed showing localizations of the slow strain wave manifestation in the areas of central and eastern Asia. The calculations are performed aimed at revealing a transverse migration of earthquakes (M ≥ 6.5) directed from the Japan and the Kuril-Kamchatka trenches toward the Asian continent during the time period from 1960 to 2015. The migration of earthquakes along the profile crossing Hokkaido Island occurs at velocities of 15 and 23 km/yr, whereas the migration velocity from the Kuril-Kamchatka Trench via Sakhalin Island is evaluated from 20 to 40 km/yr at different depths. We focus on an insufficient study of the influence of the Western Pacific subduction on the formation of the deformation field in continental Asia.

AUTHIGENIC MINERALS OF VOLCANOGENIC-SEDIMENTARY ROCKS OF THE PALEOZOIC–CENOZOIC AGE OF THE SOUTHERN PRIMORYE

Authigenic minerals in volcanogenic-sedimentary and sedimentary rocks of Southern Primorye from Permian to Miocene time have been studied. Corrensite, rectorite, highly ordered mixed-layer differences of the chlorite-smectite (corrensite-like) and mica-smectite (rectorite-like) types, mica, vermiculite-like differences (?), chlorite, defective chlorite, kaolinite, smectite, calcite, and zeolites were found. Such a set of minerals indicates that the sedimentary layer in the studied sedimentary basins could be three to five kilometer thick, and the temperature of their formation is more than 150°C. The formation of the Lower Cretaceous and Paleocene sedimentary strata has similar features, and probably proceeded first in a shallow sea basin setting of the continental margin (rift stage), sometimes under conditions close to evaporitic (presence of corrensite?), with a frequent change of the facial situation from shallow to deep sedimentation, episodic supplies of volcanic material, and gradual deepening of sedimentation basins. It can be assumed that in Early Cretaceous and Paleogene times, a series of discrete sedimentation basins along the northeastern Asia continental margin developed in a single mineralogical, tectonic, and sedimentological regime of crustal extension: minerals accumulated in the sediments, which in the process of epigenesis transformed in the following directions: a) smectite-rectorite-mica; and b) smectite (palygorskite, sepiolite?) - corrensite-chlorite. In the studied sedimentary complexes three mineralogical «layers» are distinguished: 1) chlorite-mica – mica-chlorite (Permian - Cretaceous); 2) transitional from chlorite and mica to smectite - developed are corrensite, rectorite and highly ordered mixed-layer corrensite-like and rectorite-like minerals (Cretaceous - Paleocene-Eocene), and 3) smectite (from Oligocene to the present).

MAPPING OF THE NW-TRENDING HIDDEN FAULTS FROM ANALYSIS OF THE RELIEF AND GEOPHYSICAL FIELDS IN THE PRIAMURYE REGION

The paper investigates indications of the NW-trending hidden faults in the Priamurye region. Four maijor fault zones and a series of lower-rank faults are mapped, which are indicated by lineaments of the relief, magnetic anomalies and arranged earthquake foci sequences. The NW-trending faults control the block divisibility of the upper part of the lithosphere in the region and are currently seismically active. Two NW-trending hidden faults are characterized by a considerable amount of the seismic energy released which should be accounted for in the seismic hazard assessment of the region.

THE CARBONACEOUS ROCKS IN CRETACEOUS DEPOSITS OF THE KAMCHATSKY MYS PENINSULA: GEOCHEMISTRY, METAL ACCUMULATION AND SEDIMENTATION CONDITIONS

In the Cretaceous paleoceanic deposits of Eastern Kamchatka, carbonaceous beds have been studied, the origin of which relates to the oceanic anoxic events. In carbonaceous rocks, the contents of trace elements and noble metals: Ba, Cu, Ni, Zn, Mo, V, U, Y, Au, rare-earth elements and platinoids are increased in comparison with the hosted jaspers and limestones. In particular, the Au content in ash-laden carbonaceous rocks reaches 0.8 ppm, and Pt 2.1 ppm. The geochemical proxies Mo/Mn and V/(V + Ni) indicate the accumulation of carbonaceous deposits in euxinic conditions. The significant non-lithogenic excess Ba indicates a high bio-productivity in the upper part of the water column. High bio-productivity and euxinic conditions of sedimentation caused the enrichment of carbonaceous rocks with many trace elements. Phosphorus trapped into the sediments with bone detritus, which subsequently sorbed rare-earth elements and yttrium from sea water during its fossilization. Copper, zinc and vanadium are associated with the Fe-sulfide phase (framboidal pyrite). Noble metals accumulated during sedimentation and early diagenesis were deposited with organic matter and/or directly from seawater. In carbonaceous rocks, they appear to be in the form of organometallic compounds or enter into the composition of framboidal pyrite. The sedimentation occurred at the top of a seamount in the Pacific Ocean. The studied deposits are similar to the Cretaceous sediments that formed at the tops of seamounts in the northwestern Pacific, where carbonaceous beds are also present in the sections. Organic-rich sediments were deposited within the oxygen minimum zone during periods of maximum bio-productivity of plankton.