Volume 28, 6, 2009 |
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M.V. Goroshko, V.A. Guryanov, N.V. Berdnikov, V.Ye. Kirillov.
Gold potential of volcano-plutonic zones, southeastern Siberian
Platform, and physical-and-chemical conditions of the deposits
formation 3 A.S. Karetnikov. Paleomagnetism of ultrabasites in the Konder massif and its age assessment 23 I.A. Tararin, Z.G. Badredinov, Ye.A. Nozdrachev, O.I. Sharova. Composition and origin of metamorphosed ferromanganese rocks in metavolcanics of Eastern Kamchatka 43 I.V. Buchko, A.A. Sorokin. Petrochemical and geochemical peculiarities of the Chek-Chikan gabbro-norite massif and the problems of its genesis, south-eastern framing of the North Asian craton 55 N.G. Razjigaeva, L.A. Ganzey, T.A. Grebennikova, L.M. Mokhova, T.A. Kopoteva, A.V. Rybin, A.A. Kharlamov. Peat bog of Ketoi Island – Middle-Late Holocene reference section of the Central Kuriles 65 G.F. Ufimtsev, S.N. Alekseenko, F.S. Onukhov. Morphotectonics of the Lower Priamurye 81 G.Z. Gil’manova, V.G. Prokudin. Density model of the lithosphere of the Tsushima Basin, Sea of Japan 94 A.V. Kudymov. Conditions of sedimentation in the Hauterivian-Cenomanian sea basin of the Sikhote-Alin and Lower Amur Region 102 V.I. Roslikova. Geographic features of new forms of landscapes in the southern Far East 115 L.A. Nikolaenko. Landscape-and-ecological analysis of the territory of Komsomolsk-on-Amur 120 M.V. Goroshko, V.A. Guryanov, N.V. Berdnikov, V.Ye. Kirillov Gold potential of volcano-plutonic zones, southeastern Siberian Platform, and physical-and-chemical conditions of the deposits formation Numerous gold deposits and shows are recognized in the south-eastern part of the Siberian Platform in the regions of tectono-magmatic activation. They are located in the four metallogenic zones: Ket-Kap (skarns, quartz veins and stockworks, gold-bearing lodes in silicitolites, argillisite-sericite metasomatites), Ulkan (clay-micaceous metasomatites, quartz veins), Preddzhugdzhur (quartz veins, skarns, sericite-hydromicaceous metasomatites), and Uda (sericite-hydromicaceous metasomatites). Skarn mineralization is of Mesozoic age. Mineralization in quartz veins, quartz in hydromicaceous metasomatites and quartz-sulfide veins may be Mesozoic, Paleozoic or Late Proterozoic. The highest-temperature processes of ore formation could occur in the Preddzhugdzhur skarns (500–715°C) and hydromicaceous metasomatite assemblages of the Ket-Kap zone (510–539°C). The composition of gas-liquid inclusions in the minerals of these rocks is dominated by water solutions of Na, K and Ca chlorides with concentrations of 40 % NaCl eq. They are characterized by CO2 presence in the fluid. Quartz veins and stockworks in the Ket-Kap zone formed at high ( 465°C) and moderate temperatures with solutions concentration of 32 % NaCl eq. Sometimes the minerals of these rocks hold inclusions of low-density carbon dioxide. The gold-bearing lodes of the Preddzhugdzhur zone formed at 225–230°C and solutions concentration of 1–2 % NaCl eq. The gold-bearing lodes of the Ulkan zone are distinguished by potassium-sodium-chloride specialization of the ore-forming solutions with concentrations of 2–10 % NaCl eq.., and the temperature of their formation is 220–280°C. Key words: gold, volcano-plutonic zones, deposits, ore formations, metasomatites, physical-and-chemical conditions of formation, southeastern Siberian Platform. A.S. Karetnikov Paleomagnetism of ultrabasites in the Konder massif and its age assessment Petro- and paleomagnetic study of ultrabasic rocks (dunites, clinopyroxenites, koswites) was carried out in the Konder massif. The arguments in favor of the priority and thermal remanence nature of the distinguished characteristic magnetization components are given. The calculated paleomagnetic pole coordinates are the following: a) Plat = -4°, Plong = 178°, dp = 5°, dm = 8° , for dunites; b) Plat = -2°, Plong = 181°, dp = 6°, dm = 10°, for clinopyroxenites; c) Plat = 71°, Plong = 206°, dp = 5°, dm = 6° , for koswites. Based on paleomagnetic and petromagnetic data, the age of dunites and clinoperoxenites is presumed to be Early Proterozoic; and that of koswites, Early Cretaceous. Generally, the massif is dated as Early Neoproterozoic (1000–950 Ma). Key words: paleomagnetic studies, ultrabasites, petrographic analysis, poles, the age of the massif, Konder, the Aldan Shield. I.A. Tararin, Z.G. Badredinov, Ye.A. Nozdrachev, O.I. Sharova Composition and origin of metamorphosed ferromanganese rocks in metavolcanics of Eastern Kamchatka The paper presents the detailed mineralogical and geochemical data on the metamorphosed ferromanganese rocks, which form rare lens-like bodies among the metavolcanics of the Khavyven Highland and the Ganal Ridge in Eastern Kamchatka. They are peculiar porphyry-like rocks with banded structure composed of bands of manganic garnet and bands of amphibole with large (1–5 mm) porphyroblasts of magnetite confined to them. In the ferromanganese rocks of the Khavyven Highland, greenschist-facies metamorphosed, ilmenohematite occurs together with magnetite. Magnetite of the analogous rocks of the Ganal Ridge, altered under amphibolite-facies conditions, is characterized by decay structures and contains thin lamellas of manganic ilmenite surrounded with fine crystals of iron-aluminiferous zinc-bearing spinel. Comparison of iron-titanium oxides of the ferromanganese rocks of the Khavyven Highland and the Ganal Ridge shows that the metamorphism of these structures differed not only in temperature and pressure levels, but also in oxygen volatility. Metamorphism in the Khavyven Highland occurred under higher oxidizing conditions than in the analogous rocks of the Ganal Ridge. Garnets of the studied rocks have progressive zonality, which is evidenced in the increasing content of iron, magnesium, and calcium and decreasing concentration of manganese from the center to the rims. A progressive type of zonality characterizes also amphiboles of the ferromanganese rocks of the Khavyven Highland in which the crystal cores are composed of manganic actinolite, and marginal zones, of calcium-sodium amphibole (vinchite and less often, barroisite) testifying to an increase of temperature, pressure, and oxygen volatility in the metamorphism process. Higher-temperature rocks of the Ganal Ridge usually contain magnesia hornblende and tchermakitic hornblende. The lens-like morphology of the ferromanganese rocks in Eastern Kamchatka, their restriction to the essentially volcanogenic deposits, high contents of iron oxide (up to 20% and more) and manganese oxide (about 7 to 10 %), higher concentrations of Ni and Cu, and lower contents of Ba, Sr, and Pb allowed us to compare the studied rocks with the ferromanganese crusts of the oceanic areas and to suggest their sedimentary (hydrogenic) origin and formation under conditions of the back-arc basin of island-arc systems of the Pacific-type active continental margin during the periods of abrupt waning of volcanic activity and intensive underwater currents evacuating the bulk of the lithogenic sedimentary material. Key words: basic metavolcanics, ferromanganese rocks, Ti-Fe-Mn oxides, Eastern Kamchatka. I.V. Buchko, A.A. Sorokin Petrochemical and geochemical peculiarities of the Chek-Chikan gabbro-norite massif and the problems of its genesis, south-eastern framing of the North Asian craton The Chek-Chikan massif is a typical representative of basic magmatism, which is widespread within the south-eastern framing of the North Asian craton. Gabbro-norites and amphibole-gabbro, gabbro-anorthosites and anorthosites occur in the massif. The geochemical affinity between gabbro-norites, amphibole gabbro and anorthosites suggests their genetic similarity and allows us to consider them as products of intrachamber differentiation. The enrichment in the large ion lithophylic elements Sr (424–1018 ppm), Ba (50–754 ppm), and moderate and low concentration of highly charged Nb (1–15 ppm), Hf (0.4 - 1.0 ppm) and Th (0.05–1.14 ppm) is characteristic for the rocks of the study massif. According to the model calculations the composition of the initial melt was close to that of basalt, which was crystallized at a temperature of ~ 1180°C and pressure 4 kbar. The age of the massif is 203+1 Ma (U-Pb zircon method). The geochemical peculiarities and location of the massif within the northern framing of the eastern segmennt of the Mongolian-Okhotsk fold belt allows us to presume that its formation was conditioned by either the development of the Siberian superplume or by one of the stages of the closure of the Mongolian-Okhotsk paleoocean. Key words: gabbro-norites, geochemistry, petrology, south-eastern framing of the North Asian craton. N.G. Razjigaeva, L.A. Ganzey, T.A. Grebennikova, L.M. Mokhova, T.A. Kopoteva, A.V. Rybin, A.A. Kharlamov Peat bog of Ketoi Island – Middle-Late Holocene reference section of the Central Kuriles The results of complex study of the Holocene peat bog section of southern Ketoi Island, which is proposed as a reference section for the Central Kuriles, are considered. Stratigraphical division of the peat bog is based on botanical, spore-and-pollen and diatom analysis. 16 14Ñ-dates were obtained. Volcanic ash composition was studied. Peat formation began about 6500 yr B.P. Vegetation changes during the Middle-Late Holocene were discussed, phases of vegetation development were established, and the age of paleolandscape changes, connected with climatic variations and volcanic eruption impact, was determined. Key words: peat bog, Holocene, stratigraphy, climatic changes, paleolandscapes, Ketoi Island, Central Kuriles. G.F. Ufimtsev, S.N. Alekseenko, F.S. Onukhov Morphotectonics of the Lower Priamurye Morphotectonics of the Lower Priamurye is determined by marginal-continental areal rifting and its relation with general uplifting and moderate tectonic thickening on the rim of the “stable” continent. Marginal-continental rifts are part of the general evolutional series of forms of the continent-to-ocean transition zone, and are the morphotectonic expression of the initial stage of thinning and transformation of continental lithosphere. The rim of the stable continent in the southern Far East is of complex configuration arranged with large scarps – continuous or composite, coinciding spatially with large high-gradient gravity zones. Key words: marginal-continental rift, thinning of lithosphere, large scarp, linear warping of lithosphere, transition zone, southern Far East. G.Z. Gil’manova, V.G. Prokudin Density model of the lithosphere of the Tsushima Basin, Sea of Japan 2-D density modeling along the sublatitudinal deep seismic sounding profile in the Tsushima Basin of the Sea of Japan was performed. The available data allow us to presume that the opening of the Tsushima Basin occurred in conditions of an abnormally heated mantle and was accompanied with intrusion of mantle material into the crust of the basin and the zone of transition from the basin to the continental margin of the Korean Peninsula attended by formation of oceanic crust. As compared with the normal oceanic crust thickness, the increased thickness of the crust of the basin was conditioned by accumulation of a large amount of terrigenous material and volcanogenic rocks in the upper part of the crust and underlying of mantle material in its lower part. Key words: density modeling, lithosphere, Tsushima Basin, Sea of Japan. A.V. Kudymov Conditions of sedimentation in the Hauterivian-Cenomanian sea basin of the Sikhote-Alin and Lower Amur Region Close orientations of mechanoglyphs and oblique bedding in the Hauterivian-Cenomanian sediments of the Amur-Zhuravlyovka and Tumnin turbidite complexes have been obtained. They suggest similar hydrodynamic conditions of sedimentation. These deposits are assemblages of gravitational flows, and in a lesser degree, bottom currents and background sedimentation. Sediments of the Zhuravlyovka trough accumulated in the north-western margin of the paleocontinent in immediate proximity to the foot of its continental slope. The available data on the orientations of mechanoglyphs and oblique bedding suggest the existence of large-scale vortex of constant bottom currents. The direction of the bottom current along the feeding province (the extreme outer branch of the vortex) was north-eastern. Away from the foot the direction of the bottom current changed to north, and then to west. The fragmental material on the continental slope was transported from south-east to north-west into the deep parts of the basin. In the zone of the foot of continental slope turbidity flows interacted with bottom currents. Sandy turbidites accumulated from the deviated meridional turbidity flows; and sandy argillite and silty argillite cyclites, from the most weakened sublatitudinal flows. In pauses between turbidity flows contourites and background sediments formed under circulation conditions. Key words: turbidite, mechanoglyphs, oblique bedding, hydrodynamic regime, Lower-Upper Cretaceous, Sikhote-Alin, Lower Amur Region. V.I. Roslikova Geographic features of new forms of landscapes in the southern Far East The paper is devoted to the results of investigation of different forms and substance composition of new forms of humid landscapes in the southern Russian Far East. It is reported that they hold vast information, and as indicators can substantially raise mapping expectancy. Key words: soils, forest-steppe landscapes, southern taiga, mid-taiga, concretionary and non-concretionary new forms, substance composition, Priamurye. L.A. Nikolaenko Landscape-and-ecological analysis of the territory of Komsomolsk-on-Amur The paper contains information about the ecological conditions and the structure of natural and anthropogenic landscapes of Komsomolsk-on-Amur, which is the result of technogenic landscape estimation of its territory. Key words: landscape and ecological analysis, locality, group of tracts, technogenic stress, urban landscape complexes, degree of landscape change, Far East. |