Volume 28, 1, 2009 |
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Yekaterina A. Radkevich (100th bith anniversary) 3 V.G. Gonevchuk, T.L. Krylova, A.A. Orekhov, G.A. Gonevchuk, D.K. Kokorina. Fluid regime peculiarities of the formation of systems with copper-molybdenum-gold and copper-tin mineralization (Primorye) 5 I.I. Fatyanov, V.G. Khomich, N.G. Boriskina. Reconstruction of the ore-forming system of the Mnogovershinnoe gold-silver deposit based on data on the structure of ore-bearing zones and isotopic studies (Lower Priamurye) 21 P.E. Mikhailik, A.N. Derkachev, O.V. Chudaev, N.V. Zarubina. Ferromanganese crusts from the Kashevarov Trough undersea rises (Sea of Okhotsk) 32 I.A. Tararin, V.M. Chubarov. Granitization and magmatic replacement in the contact aureole of the Yurchiksky gabbronorite massif, Ganal Ridge of Kamchatka 44 S.V. Vysotskiy, V.V. Yakovenko, A.V. Ignatyev, A.A. Karabtsov. Oxygen isotope relations as an indicator of the “basalt” corundum genesis 66 V.I. Gvozdev. Bismuth mineralization in the ores of the Skrytoe scheelite deposit, and problems of its genesis (Primorye) 72 S.V. Yefremov. Geochemistry and genesis of ultrapotassic and potassic magmatites of the eastern shore of Chaun Bay (Chukotka), and their implication for metallogenic specialization of tin-bearing granitoids 84 V.G. Nevstruev. A change in the silver/gold ratio in hydrothermal ore bodies 96 V.P. Molchanov, G.R. Sayadyan, E.I. Medvedev. Native gold from titanium-bearing placers of the Ariadnensky unit and its native sources (Primorye) 105 V.G. Gonevchuk, T.L. Krylova, A.A. Orekhov, G.A. Gonevchuk, D.K. Kokorina Fluid regime peculiarities of the formation of systems with copper-molybdenum-gold and copper-tin mineralization (Primorye The main peculiarities of fluid regime of two ore-magmatic systems located in the south-western part of the Kavalerovo ore district (Primorye) are considered. One system is accompanied with mineralization of porphyry copper type (Lazurnoe deposit), the other is attended by tin (copper-tin) mineralization of hydrothermal type (Iskra deposit). It is shown that the main distinction of the magmatic stage of development of the study systems is a high chlorine content of the copper-gold and high fluorine content of the copper-tin system. It is confirmed that such systems differ in the”oxidation-reduction” parameter, and different evolution of this parameter in the investigated systems is shown. The results of the study of fluid inclusions in quartz of postmagmatic assemblages indicate that the ore formation process at the Lazurnoe deposit is characterized by a wide temperature range and heterogeneity of the mineral-forming environment. Its early period is marked by coexistence of water-saline brines, mainly of Na-Ca-Mg-chloride composition, and low-density gas-water fluids, while at the end of ore formation common hydrothermal solutions dominated. The Iskra deposit formed in a relatively narrow temperature range from homogeneous fluids of essentially Na-chloride composition noted for moderate and low salinity. I.I. Fatyanov, V.G. Khomich, N.G. Boriskina Reconstruction of the ore-forming system of the Mnogovershinnoe gold-silver deposit based on data on the structure of ore-bearing zones and isotopic studies (Lower Priamurye) The reconstruction of the hydrothermal ore-forming paleosystem of the Mnogovershinnoe gold-silver deposit was accomplished with regard to the mechanisms of formation of structural-material elements composing the ore-bearing zones, their position on the conventional chronological scale of hydrothermal activity, and isotopic data. The employment of the structure-and-substance elements for the interpretation of the ore genesis events made it possible to take account of both synchronically and successively developed components of the ore bodies. This improved substantially the quality of reference data when constructing the dynamic model of the deposit. The suggested approach for reconstruction of the hydrothermal paleosystem of the Mnogovershinnoe deposit can be applied to the modeling of other ore objects. P.E. Mikhailik, A.N. Derkachev, O.V. Chudaev, N.V. Zarubina Ferromanganese crusts from the Kashevarov Trough undersea rises (Sea of Okhotsk Non-volcanic undersea rises (tilted blocks) were studied in the area of the Kashevarov Trough during Cruise 178 of the R/V ”Sonne”. Sedimentary rocks (conglomerates), metamorphic (biotite hornfels and tectonic breccias consisting of fragments of biotite hornfels) and intrusive (granodiorites) rocks as well as Fe-Mn crusts with a thickness of up to 15 cm were dredged from one of the tilted blocks. Structural and textural research, detailed mineral and chemical study, including rare earths and yttrium distribution, indicate that Fe-Mn crusts from the Kashevarov Trough are of hydrogenic origin. I.A. Tararin, V.M. Chubarov Granitization and magmatic replacement in the contact aureole of the Yurchiksky gabbronorite massif, Ganal Ridge of Kamchatka It is shown that the high-temperature granulite-like rocks of the Ganal Ridge resulted from contact metamorphism of the Yurchiksky gabbronorite intrusive during its emplacement into the sedimentary-volcanic rocks of the Vakhtalkinskaya rock sequence of the Ganal Group. A temperature of 700-800° C is estimated in the inner parts of the contact aureole, and basic volcanics of the sequence were transformed into double-pyroxene-plagioclase, clinopyroxene-amphibole-plagioclase and amphibole-plagioclase hornfels; and sedimentary rocks, into garnet-biotite and garnet-cordierite-biotite hornfels. Locally, hornfelsized basic volcanics were subjected to metasomatic alteration with subsequent formation of bodies of biotite-orthopyroxene-plagioclase metasomatites. In the zones of most intense fluid filtration, metasomatites experienced local magmatic replacement resulting in the formation of biotite-orthopyroxene-plagioclase±garnet streaks and segregations. Bodies of garnet enderbites were forming at the expense of sedimentary interbeds. The thermodynamic conditions of formation of the former were 700-800°Ñ and 3.2-4.8 kbar of lithostatic pressure. The comparison of the chemical composition of the Vakhtalkinskaya basic volcanics and products of their transformation suggest that chemically, metasomatic alterations and magmatic replacement correspond to siliceous-alkaline metasomatosis (granitization) and causes successive and unsteady supply of Si, Al, Na, K, Rb, Ba, Zr, Nb è Cl into the replaced rocks and removal of Fe, Mg, Mn, Ca and some other trace components – Cr, Co, Ti, Y and S. The processes of metamorphism and metasomatosis are presumed to be affected by highly mineralized mantle fluids, which were filtrated along magmatic channels, along which gabbroid magma also rose. S.V. Vysotskiy, V.V. Yakovenko, A.V. Ignatyev, A.A. Karabtsov Oxygen isotope relations as an indicator of the “basalt” corundum genesis Investigation results of oxygen isotopes in corundum and associated minerals from Yogo lamprophyres (Montana, USA), plagioclase-corrundum inclusion from alkaline basalt (Tunkin depression, Russia), and recent alluvium of Podgelbanochnyy alkaline-basaltic Volcano (Primorye, Russia). It is shown that all sapphires, whose origin is related to mafic magmatic rocks, have a nearly similar isotope composition (varying within 2.5‰), and most of them fall within a range of +4.5‰ to +7.0‰ relative to SMOW. Oxygen isotope relations of both corundum-associated minerals (olivine, pyroxene, mica, etc.) and enclosing rocks also fall within this range. This indicates that sapphire crystallization occurs in the course of evolution of parent basic magma. However, xenogenic corundum also exists for which basaltic magma is a mere transport agent from the place of its origin to the Earth’s surface. It has an essentially different isotope composition, it is in nonequilibrium with the enclosing lavas, and is of unlike genetic nature. V.I. Gvozdev Bismuth mineralization in the ores of the Skrytoe scheelite deposit, and problems of its genesis (Primorye) The mineral composition of ore veinlets of the Skrytoe scheelite deposit (Malinovsky ore node, Primorye) has been studied in detail in the core samples of drill holes. It has been recognized that elevated bismuth and tellurium concentrations in the ores are attributed to the presence of native bismuth, silver-lead-bismuth sulfosalts of the lillianite-gustavite series (gustavite, schirmerite, tregerite, and others), sulfides (bismuthine, ikunolite) and sulfotellurides (joseite-A) of bismuth. The chemical composition of bismuth minerals is given, and their structural interrelations are described. Conditions of formation of bismuth mineralization and also features making it similar to mineralization at the likely-type deposits of the region are considered. The problems of the genesis and formational belonging of the deposit are discussed. S.V. Yefremov Geochemistry and genesis of ultrapotassic and potassic magmatites of the eastern shore of Chaun Bay (Chukotka), and their implication for metallogenic specialization of tin-bearing granitoids Basite magmatism preceding the intrusion of abundant acid magmas becomes evident only during periods of substantial tectonic reconstructions embracing both continental crust and lithosphere mantle. The study of this magmatism makes it possible to solve genetic problems and derive essential information concerning matter sources and processes responsible for granitoid magmatism. This paper reports the results of geochemical study of potassic and ultrapotassic magmatites preceding the intrusion of the granitoid complex and directly included into it. In terms of geochemical features, the studied Chukotka magmatites correspond to derivatives of potassic and ultrapotassic magmas, which allow us to use models of formation of ultrapotassic basites for interpreting the genetic features of tin-bearing granitoids, in particular, for explaining the anomalous contents of incoherent elements in these rocks. Based on recent genetic models and geologic, geophysical and geochemical data, it has been established that the source of this specialization was the mantle domain located within the lithosphere mantle. The domain was formed within the convergent geologic boundary as a result of metasomatic transformations of rocks of the mantle wedge by fluids, segregated during dehydration of the oceanic lithosphere. A new model of tin-bearing granitoid genesis in collision orogens is proposed based on the derived results. The conception of the specialized lithosphere source is basic in this model. Its geochemical specific character and metallogenic specialization are realized under intense tectonic transformations, which affect the lithosphere mantle. This specialization is inherited by magmas formed during melting within this domain. V.G. Nevstruev A change in the silver/gold ratio in hydrothermal ore bodies The silver/gold ratio in the ore bodies of deposits of different formational type has been investigated. It has been established that the value of the ratio is functionally related to the relative sulfur content of ores (the relation of the product of lead, zinc and copper content to gold). The functional dependence is most reliably approximated by the power function. As exemplified by 85 geochemical characteristics of 29 deposits, differences in the values of the silver/gold ratio in the ore bodies of the volcanogenic and volcanogenic–plutogenic type are shown. V.P.Molchanov, G.R. Sayadyan, E.I. Medvedev Native gold from titanium-bearing placers of the Ariadnensky unit and its native sources (Primorye) Centuries-old intensive mining of precious metals from placers of the south of the Far East has led to a depletion of their geological reserves. Strengthening of a raw-material base of the region is associated with complex exogenetic deposits where precious metal minerals are secondary constituents. The structure of native gold from titanium-bearing placers spatially and genetically connected with the Areadnensky massif of basic-ultrabasiñ rocks (left bank of the Bolshaya Ussurka River) has been studied. Data obtained let us draw a conclusion that the placer origin occurred with the participation of polygenetic native sources. Mafite-ultramafites were copper and mercury gold suppliers. Apparently, quartz veined formations containing gold and antimony were the other mineral source for the placers. |