Noble metal-graphite mineralization: A comparative study of the carbonaceous granite-gneiss complex and shales of the Russian Far East |
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| Institution: | 1. Far East Geological Institute, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. Stoletiya Vladivostoka, Vladivostok, 660022, Russia;2. Kosygin Institute of Tectonics and Geophysics, Far Eastern Branch, Russian Academy of Sciences, 65, Ul. Kim Yu Chena, Khabarovsk, 680000, Russia;1. Institute of Experimental Mineralogy, Russian Academy of Sciences, Academician Ossipyan str., 4, Chernogolovka, Moscow 142432, Russia;2. Department of Petrology, Moscow State University, Moscow, Russia;3. Department of Geology, University of Johannesburg, Johannesburg, South Africa;4. Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia;1. British Geological Survey, Columbus House, Cardiff, CF15 7NE, UK;2. Department of Earth Sciences, The University of Western Ontario, London, Ontario N6A 5B7, Canada;3. Department of Earth and Environmental Science, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada;4. National Museum of Wales, Cathays Park, Cardiff, CF10 3NP, UK;5. NERC Isotope Geoscience Laboratory, Keyworth, Nottingham, NG12 5GG, UK;1. Lithospheric Organic Carbon (LOC) Group, Department of Geoscience, Aarhus University, 8000, Denmark;2. Department of Reservoir Geology, Geological Survey of Denmark and Greenland (GEUS), Dk-1350 Copenhagen K, Denmark;3. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;4. Geological Survey of Canada (GSC) Commission géologique du Canada, Natural Resources Canada (NRCan) Ressources naturelles Canada, Calgary, AB, Canada;5. FG & Partners Ltd., Calgary, AB, Canada;1. Western Australian School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, WA 6102, Australia;2. Institute of Chemical Engineering and Technology, Fuzhou University, Fuzhou 350108, China |
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| Abstract: | A new noble metal-graphite mineralization has been revealed in the Ruzhino amphibolite-facies rocks of the northern Khanka block. It is characterized by Au and PGE (platinum group elements) contents (up to tens g/t, Pt > Au) as high as those in world-class deposits hosted by sedimentary and magmatic rocks, but is distinguished from them by isotopic composition of carbon, hydrogen and oxygen, all suggesting a distinct mantle contribution (δ13СVPDB from − 8.5 to − 10.5‰ in graphite, δDVSMOW from − 82.5 to − 106.7‰ and δ18OVSMOW from 8.2 to 10.1‰ in biotite). The Ruzhino-type mineralization is highly resistant to common chemical treatments, so that detection of their metals requires that some special methods be developed. Atomic Absorption Spectrophotometry and Inductively Coupled Plasma Mass Spectrometry following severe chemical treatments and ignition at 600–650 °C, as well as Ion Mass Spectrometry allowing a direct detection of elements in solid materials were employed in this study. These methods increased noble-metal contents of the graphitized rocks compared to standard analyses including a conventional fire assay. In addition, electron microscopy surveys discovered extremely diverse native-metal and intermetallic complexes with C, O, Cl, F, REE and other elements. The microinclusions, however, represent a minor part of the mineralization. Major constituents seem to form carbonaceous nanocompounds invisible under a microscope. These graphite-based nanocomplexes, which are especially developed in the case of Pt, seem to be responsible for the highly resistant character of the Ruzhino mineralization. They also may be present in the latent form among the common Au ± PGE ores hosted by carbonaceous shales like those we studied in the close vicinity of the Ruzhino amphibolite-facies rocks and in the northeastern Bureya–Jiamusi terrane. |
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