V. P. Molchanov

Carbonization and geochemical characteristics of graphite-bearing rocks in the northern Khanka terrane, primorie, Russian Far East

Regional carbonization was examined in Riphean metamorphic complexes in the northern part of the Khanka terrane. The results obtained by various techniques of physicochemical analysis indicate that all petrographic rock varieties of this complex bear elevated concentrations (from 10−4 to 10−6 wt %) of Au and PGE. XRF data were used to describe a wide spectrum of trace elements: Ti, V, Ni, Cr, Pt, Pd, Re, Rh, Os, Ir, Cu, Hg, Au, Ag, Ta, Nb, Sr, Rb, Zr, La, W, Sn, Pb, and Zn. The Rb/Sr-Ba diagram shows the fields of anatectic granite-gneisses, biotite granites, lamprophyres, graphitized crystalline schists, black shales, skarns, and quartz-graphite metasomatic rocks. The C isotopic composition in graphite from the metaigneous rocks (lamprophyres and crystalline schists of the amphibolite facies) corresponds to δ13C from −8.5 to −8.7‰, which suggests that the carbon could be of endogenic provenance. The carbon isotopic composition of the greenschist-facies black shales corresponds to δ13C from −19.9 to −26.6‰, as is typical of organogenic carbon. The concentrations of precious metals in the rocks are, on average, one order of magnitude lower than in the graphitized crystalline schists. The origin of the precious-metal ore mineralization was likely genetically related to the regional carbonization process.

Noble Metals in Carbon-Rich Metamorphic Rocks of the Khanka Terrane, Primorie

Carbon-rich metamorphic rocks of Riphean age in the northern part of the Khanka terrane were first analyzed for concentrations of noble metals (Au, Ag, Pt, Pd, Ir, Os, and Ru). According to the data of various physicochemical analytical techniques, the Au and Pt concentrations broadly vary: from 0.01 to 52 ppm for Pt and from 0.1 to 30 ppm for Au. Various techniques of sampling and analysis variably affect the losses of these metals because of difficulties in the decomposition of metal-carbon chemical bonds. The carbon isotopic composition (13C from −8.5 to −8.7‰) of the graphitized amphibolite-facies rocks widespread in the core of the Ruzhino paleodiapir suggest that their carbon is of mantle provenance. The Early Cambrian metaterrigenous rocks metamorphosed to the greenschist facies have 13C from −19.9 to −26.6‰, which testifies to its organic origin. The elevated concentrations of noble metals in these rocks suggest that the sources of carbon and metals were polygenetic and that the ore-forming system evolved over a long time span.

Platinum- and gold-bearing rodingites of the ust'-dep ophiolite block (middle amur region)

The Ust’-Dep ophiolite block, a part of the Selemdzha‐Zeya Belt, occupies an area of 350 km 2 and incorporates apoharzburgite serpentinite massifs intruded by numerous (>60) dikes of diabases and granitoids up to 100 m thick and more than 1 km long. Ophiolitic outcrops of this block make up a SW- to NW-trending band extending from the right bank of the Zeya River to the Gar River basin. Only small fragments of ophiolite massifs are preserved in spurs of the Tukuringr Ridge (Fig. 1). The Ust’-Dep and Gar protrusions in this area include dislocation zones with superimposed metasomatic alterations (development of listvenites and rodingites with gold mineralization). The majority of rodingite and listvenite occurrences are confined to outcrops of Lower Paleozoic‐Middle Cretaceous granitoid intrusions and dikes. Listvenites usually considered the source of placer gold are scrutinized in [1, 2]. However, data on the gold potential of rodingites in the Ust’-Dep block are lacking, although they are similar to rodingites in the Zolotaya Gora deposit (southern Urals) that was previously proposed as a holotype of the gold‐rodingite association [3]. Their similarity is manifested in the development of rodingites among listvenitized serpentinites. Therefore, the gold mineralization of Uralian rodingites is attributed to a younger process of listvenitization [4].

Modeling of gold mass transfer during the listwanitization and rodingitization using the example of the Ust’-Dep ophiolite complex in the upper Amur territory

Gold mass transfer with chloride and carbonate-chloride solutions was examined at the 300 and 400°C isotherms and Ptot = 1 kbar by means of experimental modeling and theoretical simulations. CO2 was confirmed to suppress Au solubility in fluids. The low Au solubility (mAu < 10−8) determined in the experiments explains the mechanism of its precipitation when serpentinites and listwanites interact with acidic mineralized solutions. Listwanitization, which was genetically related with the emplacement of orogenic granitoids, was determined to have overprinted serpentinites and rodingites and strongly affected Au transport in the oregeochemical system. The characteristics of the metasomatic processes in the Ust’-Dep ophiolites and the gold concentration in the rocks produced by these processes confirm this conclusion.

Producing low-ash crystalline graphite from high-carbon rocks of the Far East south

The possibilities of producing low-ash crystalline graphite from high-carbon rocks of the southern Far East have been investigated. Promising setups for purifying the natural graphite from impurities using the processes of hydrothermal treatment of flotation concentrates have been developed.

Noble metals in graphite-bearing rocks of the Liumao deposit (China)

Native gold, platinum, nickel, and other ore minerals have been discovered in graphite-bearing rocks of the Liumao deposit (Heilongjiang province, China). The results obtained are similar to the previously published materials on the mineralogy of carbon-rich formations of the Tamga and Turgenevo deposits (Primorye, Russian Far East) located in the same region of graphitization in the Khankai terrane as the Chinese object. The defined similarities are most likely explained by participation of deep reduced fluids in the process of ore genesis.

Development of the principles of an integrated process for extraction of high-purity graphite, gold, and rare earths from carbonaceous rocks

Graphite-bearing rocks of the Ruzhinskaya area (Primorskii Krai, Russia) were found to contain high concentrations of noble and rare earth metals. Industrial exploration of these reserves is restrained by the lack of concentration technique. The application of hydrometallurgy for the production of useful components was studied for the first time. A prospective plan of integrated extraction of high-purity graphite, gold and rare earths using hydrogen fluoride treatment of flotation concentrates was designed.

Plasma-chemical and hydrometallurgical processes for the synthesis of nanostructures from natural crystalline graphite

A flow chart for the extraction of high-purity (99.98%) crystalline graphite by hydrometallurgical methods from the high-carbon rocks of the Ruzhinskaya area was developed. The graphite was used as the starting material for plasma-chemical tests. Nano-sized carbon nanomaterials were isolated upon the experiment. Some of them could be inherited from the natural graphite-bearing rocks. The results of investigation will be used in the development of resource-saving process for extraction of useful components.

Approaches to the development of analytical methods and a technology for the extraction of useful components from graphite-bearing rocks

The capabilities of a new procedure for the rapid determination of carbon in graphite-bearing rocks containing noble metals from the south of the Far East were studied. A rational sample preparation procedure based on the fusion of samples with lithium metaborate was used for the determination of macroelements and trace elements (from petrogenic to Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Mo, Cd, Sn, Cs, Ba, Hf, Ta, W, Pb, Th, U, and rare-earth elements) in a single weighed sample. The development of new analytical methods makes it possible to solve a problem of the creation of a technology for the extraction of useful components from the high-carbon rocks.

Fundamentals of the technology for extracting useful components from overburden rocks of coal beds in the south Far East

The possibility of extracting building sand and by-products, first of all, noble metals, from overburden rocks of coal beds of the Pavlovskoe deposit in Primorskii Krai, Russia, has been studied. A fundamentally new resource-saving technology for coal mining waste management has been proposed.