I.B. Tsoy, Ye.P. Terekhov, M.T. Gorovaya, V.V. Shastina, A.V Mozherovskiy
Cenozoic sedimentation on the western slope of the Yuzhno-Okhotsk Basin, Sea of Okhotsk

We describe the Oligocene through Pleistocene sediments recovered from dredge hauls along the western slope of the Yuzhno-Okhotsk (Kuril) Basin and relate the sediment parameters and compositions to the geologic and oceanographic histories of the Cenozoic Sakhalin-Hokkaido continental margin. New data, including ages, sediment grain-size parameters, and mineralogical composition are combined with interpretations of Cenozoic regional geology to evaluate the sediment sources, transport agents, and depositional environments.

 R.G. Kulinich, A.I. Obzhigov
Barite-carbonate mineralization, methane anomalies and their geophysical fields in the Deryugin Basin(Sea of Okhotsk)

The paper offers the results of gravity and magnetic anomalies interpretation in the area of anomalous assemblage of barite-carbonate mineral associations and active methane emanations within the limits of the eastern part of the Deryugin Basin (Sea of Okhotsk) with the purpose of identifying their possible deep sources. It has been established that the above-mentioned mineral associations and methane emanations are concentrated within the limits or on the periphery of a volcanogenic-sedimentary depression. The observed attributes of fluid activity, active emission of methane and a high heat flow revealed near the area under study can be a manifestation of remnant postmagmatic low-thermal processes within the limits of the described volcanogenic structure. Barite-carbonate mineral genesis can be a secondary effect of the above-mentioned processes.

Reconstruction of ice conditions in the Sea of Okhotsk in the last 24000 years basing on the distribution of ice-rafting material

The oxygen isotope records, radiocarbon AMS data, carbonate and opal stratigraphy, sediment magnetic susceptibility, tephrachronology and paleontological results were used to obtain a detailed sediment stratigraphy and an age model of the studied cores. To study the ice cover measurements, the analysis of the lithogenic grain number in a fraction of bottom sediments larger than 0.15 mm was carried out. For the quantitative estimation of intensity variations of the IRD particles supply per unit of time, the authors calculated the IRD accumulation rate. The obtained results allowed us to plot AR IRD distribution for the first isotope stage (0–12.5 C14 kyr) and for the second stage (12.5–24 C14 kyr). The first isotope stage was subdivided into the latest deglaciation and the beginning of the Holocene (6–12.5 C14 kyr) (transitive period), when the sea level was changing significantly, and the second part of the Holocene (0–6 C14 kyr), whose climate conditions and the sea level were similar to the modern estimates. Data clearly show strong increase in ice formation in the glacial Sea of Okhotsk and its extent in the middle part of the sea. The average annual duration of ice coverage during glaciation was longer than that for interglaciation. However, the sea ice was not continuous the whole year round and was disappearing in the Sea of Okhotsk in summer time except the far northwestern part adjoining the Amur River estuary.

N.G. Razjigaeva, T.A. Grebennikova, L.M. Mokhova
Middle Pleistocene littoral deposits, Iturup Island, Kurils

The Middle Pleistocene age of the 25-30 m marine terrace of Iturup Island was established on the basis of diatom (Proboscia barboi diatom zone) and pollen data. The studied sections include two sedimentological rhythms, recording two transgressive phases correlated with 11 and 9 oxygen isotopic stages. The facial features and paleogeographical environments were reconstructed. The Mindel-Riss Interglacial climate was warmer than the Present temperature conditions and possibly warmer than the Holocene Optimum. Shallow straits developed on the place of the isthmuses, and water exchange between the Sea of Okhotsk and the Pacific was more intense. The tectonic uplift of Itutup Island was slower than it is estimated. The Iturup block uplift magnitude was less than that of the Kunashir block.

 B.L. Stolov
Geoelectric Model of the main ore districts of Primorye

The paper deals with the geoelectric model of the main ore districts of Primorye which is regarded as a system of two interrelated components: generalized conceptual notions of geoelectric objects, participating in the structure of the ore districts (1) and electrical fields caused by them (2). The model is based on the characteristic features of the geoelectric structure of the Kavalerovo, Dalnegorsk and Armin ore districts. The modal section of the ore districts of Primorye includes 3 geoelectric complexes with different electric parameters. The model shows the structure of the upper part of the section (up to 2-3 km), which can be studied by electric methods of prospecting.

T.M. Okuneva
Biostratigraphy of marine Jurassic deposits of the East Transbaikal region, and some problems of correlation of the Lower Mesozoic, Southeast Russia

Three main sections of the marine Jurassic in the East Transbaikal region are described. Data on the distribution of stratigraphically significant Bivalvia genera, Galinia in particular, and assemblages of bivalve mollusks of the Toarcian units, especially of the upper stage, have been substantially supplemented. The Pliensbacian-Toarcian boundary has been identified in the section of the Talangui River. It runs within the Sivachinskaya suite. Simultaneous start of sedimentation in the Onon-Undinskaya and Borzin-Gazimurskaya structural-and-facial zones has been proved. Correlation between the Lower Mesozoic in Southeast Russia and sections from other regions has been made. Portraitures of genera and index-species of Triassic fauna-bearing zones and layers, and also of some rare and new bivalve species: Langvophorus amurensis, Pseudoclaraia beltenevi, P.bobylevi, P.zakharovi are given.

A.V. Ivanov, S.V. Rasskazov, M.N. Maslovskaya, Ye.I. Demonterova, I.S. Brandt, S.B. Brandt, Ye.V. Saranina, M.Ye. Markova, Yu.V. Koshkov, A.V. Pipich
The Early Jurassic age and Middle-Late Jurassic tectonic exposure of granitoids from the basement bulge, northern part of the Amur-Zeya depression: Rb-Sr and K-Ar isotope data

The disturbance of Rb-Sr and K-Ar isotope systems has been established in minerals from samples taken from two massifs of calc-alkaline granitoids in the basement bulge of the northern part of the Amur-Zeya depression. Both studied massifs crystallized in the Early Jurassic at 191 Ma. The redistribution character of radiogenic strontium between minerals and the loss of radiogenic argon attributed to biotite indicate closing of the Rb-Sr and K-Ar isotope systems in the Middle-Late Jurassic in the interval 169-155 Ma. In terms of their age and chemical composition, the studied rocks are similar to the palingenic granitoids of the western and central Mongol-Okhotsk fold belt intruded during collision of the Amur microcontinent with the Siberian continent. The final stage of collision processes in the Middle-Late Jurassic was accompanied by the start of destruction of the eastern part of the Amur microcontinent, which was, probably, obvious at the initial stage of formation of the Amur-Zeya depression and a tectonic move of the studied massifs into the near-surface conditions of low temperatures.

I.V. Buchko, A.A. Sorokin, A.I. Lobov
Mineralogy and geochemical features of the "Tomskoye" gold deposit

The "Tomskoye" ore deposit located in granites of Late Paleozoic age is established within the northern margin of the Argun terrane. The ore bodies identified in the bedrock are NS-trending with a thickness up to 60 cm and quarts-galena-arsenopyrite composition. Gold content is up to 30 ppm (by atomic-absorption analysis), lead content is up 10%, zinc content is up to 10%, and cooper content, up to 1%. Host-rock alterations are characteristic of the beresite and the argillizite formation. The presence of tourmaline is indicative of high boron content in fluids. It is suggested that mineralization is related to the formation of I-type granitoids of the Urusha intrusive rock complex in the environment of an active continental margin.

E.L. Shkolnik, Ye.A. Zhegallo, V.M. Novikov
Different nature of kaolinite in rocks of the coal-bearing unit of the Pavlovsk brown coal field, Primorye Territory

Three morphogenetic types of kaolinite in clay carboniferous deposits of the Pavlovsk brown coal field in the Primorye Territory are established using modern methods of research, including electronic microscopy. Kaolinites 1 form vermicular crystals; and kaolinites 2, sliced crystals being the products of mechanical redeposition of various zones of the profile of crust of weathering of basement rocks. Kaolinites 3 are a diagenetic formation; they form complete biomorphoses on carbonificated plant remains and easily decompose due to acidification. These data should be taken into account in the estimation of kaolinite-bearing rocks as mineral products.