Volume 29, 3, 2010 |
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I.I. Fatyanov, V.G. Khomich.The problem of specialization of granitoid fluid -magmatic systems
regarding gold or tin (as exemplified by the Russian Far East) 3 A.S. Vakh, O.V. Avchenko, A.A. Karabtsov. Cervandonite-(Ce) in the ores of the Berezitovoye deposit: the world’s second finding 14 I.S.Golubenko. Quantitative estimation of spatial distribution of geological objects and gold mineralization in the Degdekan-Arga-Yuryakh mineral district (Russian Northeast) 24 Ye. G. Glushkova, Z. S. Nikiforova. Comparative description of typomorphic features of native gold of the middle Lena basin (southeast of Siberian platform) 34 M.A. Mishkin, A.M. Lennikov, T.B. Bayanova, G.M. Vovna, V.G. Sakhno, R.A Oktyabrskiy, Z.G. Badredinov. The first results of U-Pb geochronology investigation of Precambrian granitoids of the Batomga block, Aldan shield 45 A.A. Stepashko. Deep roots of seismotectonics in the Far East: Sakhalin zone 50 S.V. Trofimenko. Tectonic interpretation of the statistic model of azimuth distribution of gravimagnetic fields anomalies on the Aldan shield 64 V.A. Glagolev, A.M. Petrishchevskiy. Simple algorithm for sections construction using 3D document files of geologic-geophysical data 78 G.F. Ufimtsev. Pediments of Asia 86 Ye. P. Terekhov, A.V. Mozherovskiy, M.T. Gorovaya, I.B. Tsoi, N.G. Vashchenkova. Material composition of Kotikovo Group rocks, and the main stages of development of Terpeniya Peninsula in the Late Cretaceous-Paleogene (Sakhalin Island) 97 Anniversaries Izosov L. A. (to the 70-th anjniversary) 111 I.I. Fatyanov, V.G. Khomich The problem of specialization of granitoid fluid-magmatic systems regarding gold or tin (as exemplified by the Russian Far East Not only the heterogeneous structure of the Earth’s crust and upper mantle resulting in diverse sources of magmas and ore elements, but also different geochemical properties of Au and Sn are responsible for isolation of their large concentrations followed by the formation of independent metallogenic provinces, zones, and ore clusters. During transportation of Au and Sn by fluid-magmatic columns, the polarizing impact on metal mobility manifested itself in their different relation to silicate-forming melt clusters, oxygen, and other strong oxidizers. This impact favored individualization of migration ways of the elements to the levels of ore concentration. By the moment when the ore-bearing fluids became isolated, the metallogenic specific character of the melts, contrasting in their redox potential , had been already defined. This is confirmed by the dominating association of tin mineralization with granitoids of the ilmenite series; and gold mineralization, with the magnetite series. The fluid-magmatic systems with an intermediate degree of the melts reduction-oxidation could be potential producers of the combined metal concentrations. In these cases, however, the combined concentrating of tin and gold was hampered by the reverse direction of oxidation-reduction reactions when their most common minerals formed: the basic migration form of tin Sn+2 must be oxidized (with cassiterite isolation), and the forms of gold – Au+ or Au+3 must be reduced (with metal isolation in its native form). Probably, that is why the combined tin and gold concentrations are dominated by one of the metals with a tendency of their accumulation in different-stage mineral complexes. The degree of oxidation-reduction of melts which “regulated’ the migration activity of the metals, depended on the duration of the fluid-magmatic column movement to the levels of ore concentration – the function of the depth of their origin and the rate of movement which were controlled by geodynamic regimes. A.S. Vakh, O.V. Avchenko, A.A. Karabtsov Cervandonite-(Ce) in the ores of the Berezitovoye deposit: the world’s second finding This paper characterizes the world’s supposedly second finding of rare arsenosilicate cervandonite-(Ce), which was recognized in the ore-bearing metasomatic rocks of the Berezitovoye gold-polymetallic deposit in Upper Priamurye, Russian Far East. The cervandonite occurs in the association with quartz, biotite, muscovite, orthoclase, almandine-spessartine garnet, tourmaline, basic plagioclase, and sulfides. It is represented by optically homogenous as well as heterogenous aggregates with visible crystals measuring 10 µm up to 0.1–0.3 mm. The average chemical composition of homogenous aggregates of cervandonite-(Ce), as determined by microprobe analysis, 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 comparison study of cervandonite-(Ce) of the Berezitovoye deposit and the analogous mineral of the Alpine mica gneiss veins of Mt Pizzo Cervandone in the Central Alps showed that the former mineral by its compositional features can be assigned to a new variety of cervandonite-(Ce) which is characterized by the ordered stoichiometric composition corresponding to the simpler theoretical formula (Ce,Nd,La)(Fe3+,Fe2+,Ti4+,Al)3(Si2As3+)3O12. I.S.Golubenko Quantitative estimation of spatial distribution of geological objects and gold mineralization in the Degdekan-Arga-Yuryakh mineral district (Russian Northeast) An attempt was made to use GIS technologies for development of the methods of forecast evaluation of metal presence in the local territory based on mathematical statistics. The Degdekan-Arga-Yuryak mineral district (Magadan region) was chosen as the subject of research in whose territory spatial database of geology and minerals was established. The use of the methods of spatial and statistical analysis of diverse cartographical-geological information made it possible to quantitatively assess the spatial location of geological objects and gold mineralization in the territory of the district. As a result, spatial analysis was made of location conditions of gold deposits, and their relation to geological characteristics was recognized. Based on the revealed geological features, favorable for location of mineralization, two areas were distinguished promising for commercial mineralization prospecting. The work showed sufficient effectiveness of the used methods in large-scale ore cluster-level metallogenic investigations. Ye. G. Glushkova, Z. S. Nikiforova Comparative description of typomorphic features of native gold of the middle Lena basin (southeast of Siberian platform) Typomorphic features of native gold in placer occurrences in the basin of the Lena middle reaches have been studied for the first time. Generally, it is supposed that placer gold occurrences were formed basically by repeated redeposition of fine native gold (0.1–0.25 mm, 900–1000 ‰ of essay standard of gold) from the ancient deposits into the younger ones. Extensive important gold occurrences are apparently connected with the ancient basement protrusions and, apparently, with the Precambrian stage of ore genesis. A number of placer deposits of the Vitim-Pilkin watershed were formed by the local gold-bearing native sources, which is indicated by the discovery of gold larger than 0.5 mm in that area. They are related to “sheet” metal, and are not transported to large distances. The discovery of poorly rounded gold of ore type measuring more than 0.25 mm of low and medium essay standard of 500–800 ‰, points to new nearby native sources associated with zones of ancient faults, which were repeatedly renewed in Mesozoic time. M.A. Mishkin, A.M. Lennikov, T.B. Bayanova, G.M. Vovna, V.G. Sakhno, R.A Oktyabrskiy, Z.G. Badredinov The first results of U-Pb geochronology investigation of Precambrian granitoids of the Batomga block, Aldan shield The paper offers the first results of U-Pb geochronology investigation of Precambrian granitoids of the Batomga block (Aldan shield). U-Pb results indicate that the amphibole diorites of the Batomga block are recognized to have an age of 2062±14 Ma; and the biotite plagiogranites, 2055±7 Ma. These granitoids experienced metamorphism of the epidote-amphibolite facies 1920±8 million years ago.. A.A. Stepashko Deep roots of seismotectonics in the Far East: Sakhalin zone The key role of the lithosphere deep structure in the present-day deformations and seismicity in the Far East is indicated. Judging by the regional variations in the composition of mantle xenoliths and Neogene-Quaternary basalts, a wedge-shaped block of NE-striking highly ferruginous mantle was mapped. The Yilan-Yitong and the Fushun-Mishan strike-slip fault of the Tan-Lu megazone are the continuation of the referred block’s boundaries, on which the mantle block was transported along the continental margin in Jurassic-Cretaceous time. The distribution of strong earthquake epicenters of Priamurye with Ì >= 5.0 demonstrates that such mantle structure governs the key features of deformations and seismicity of the region. The dominance of W-oriented compression caused by the drift of the Amur plate results in NE pinching-out of the mantle block, which imposes extra compression at the Okhotsk plate boundary. As a result, the highly seismic Sakhalin zone, characteristically similar to the convergence area of the Indian plate and Eurasia, formed on the front of the mantle block. In both cases the main features of deformations and seismicity are brought about by horizontal pressure of the tectonic block, along whose front there was objectively regulated alternation of compression and extension zones. Strong earthquakes of Sakhalin with Ì >= 6.0 are concentrated in a seismic suture 50 km wide, where compression is concentrated. It has a cross-cut position with respect to the general faults of the island; however, it runs parallel to the front of the mantle wedge. Two cycles of migration are recognized for Sakhalin earthquakes with Ì >= 6.0: 1907–1971 and 1995–2007. During both cycles the first earthquake shocks occur on the north, and then they migrate southeast, which is also accompanied with a decrease in the depth of the earthquake foci. Patterns of this migration indicate that affected by asymmetric compression the mantle wedge is not only pinched out to the northeast but also rotates clockwise to the southeast. This rotation contributes considerably to the genesis of strong earthquakes of Sakhalin. S.V. Trofimenko Tectonic interpretation of the statistic model of azimuth distribution of gravimagnetic fields anomalies on the Aldan shield The paper presents results of static analysis of azimuths of anomalies of the gravitational and the magnetic field, and the leveled sectors of hydronetwork. Seven mutually orthogonal systems of preferred directions are defined based on statistically significant maxima of azimuth distribution and anomaly indicators. Geometric constructions show the presence of increased density zones of anomaly indicators, which form regular and quasiregular domain cells. The increased density zones of anomaly indicators of the distinguished systems are comparable with the known models of the Aldan shield structure and the spatial field of strong earthquakes. V.A. Glagolev, A.M. Petrishchevskiy Simple algorithm for sections construction using 3D document files of geologic-geophysical data The algorithm providing automated construction of section maps and sections from discrete values of geologic-geophysical parameters described by 3D document files has been developed. Data input and output are based on standard formats of the Word, DOS and Surfer-8 operational systems, which makes it possible to use it by small scientific-technical teams when processing geologic information and interpreting local GIS. Examples of realization in practice of the algorithm for the study of density properties of the Earth’s crust and upper mantle in the Transbaikal Region and Sikhote-Alin are discussed. G.F. Ufimtsev Pediments of Asia Gently sloping denudation plains – pediments, widely distributed in different climatic and morphotectonic regions of Asia are described. Their general classification is suggested, including false pediments, which is based on morphological properties and positions in the structure of morphological landscape. The main features of pediment formation and the place of pedimentation in the process of generation of leveling planes are considered. Ye. P. Terekhov, A.V. Mozherovskiy, M.T. Gorovaya, I.B. Tsoi, N.G. Vashchenkova Material composition of Kotikovo Group rocks, and the main stages of development of Terpeniya Peninsula in the Late Cretaceous-Paleogene (Sakhalin Island) Substance composition of Kotikovo Group rocks (Uchirskaya, Zaslonovskaya, Turovskaya, and Ol'donskaya Formations) of Terpeniya Peninsula (East Sakhalin) has been studied. It is conjectured that Cenozoic deposits unconformably overlie Maastrichtian-Danian ones with basal conglomerate in the basement. Investigation results allow recognition of two major stages of development of Terpeniya Peninsula in the Late Cretaceous-Paleogene. The first stage involves the formation of Maastrichtian-Danian volcaniclastic and volcanogenic-sedimentary rocks of the Uchirskaya Formation; and the second, the formation of Paleocene-Eocene sedimentary rocks of the Zaslonovskaya, Turovskaya, and Ol'donskaya Formations. At the end of the first stage (at the boundary of the chirskaya and the Zaslonovskaya Formation) there was a change of tectonic regime. It manifested itself in substantial slackening of tectonic activity, rise of the territory and appearance of new sources of removal. During the second (Early Paleogene) stage, the area of the East Sakhalin Mountains, Terpeniya Peninsula and Terpeniya submarine Ridge were a shallow-sea sedimentation basin being the western side of the Cenozoic Pogranichny basin. The formation of the anticlinal structure East Sakhalin Mountains – Terpeniya Peninsula – Terpeniya submarine Ridge was in the Late Cenozoic period of development of East Sakhalin. |