Vol 61, No 4 (2019)


Scale effect in a fluid-conducting fault network

Petrov V.A., Lespinasse M., Poluektov V.V., Ustinov S.A., Minaev V.A.


The data presented in the article consistently outlines the methodology for studying the orientation and morphogenetic characteristics of fracture systems of four scale levels including kilometers, meters, centimeters and millimeters. The Urtuisky granite massif, located in the South-Eastern Transbaikalia to the west of the Streltsovsky caldera, containing uranium deposits unique in their reserves was chosen as the object of the research. The massif is composed of Late Riphean granites and granite-gneisses, affected by dynamometamorphic and hydrothermal-metasomatic transformations in various degrees, and dissected by numerous faults with traces of fluid activity of various tectogenesis episodes. The interrelation between such geometrical parameters of fractures systems as specific density and specific length was established. It is shown that such geostructural data should be used for conceptual and numerical modeling of fluid filtration and radionuclides transport processes occurring in a three-dimensional fractured-pore space of crystalline rocks, as applied to the reconstruction and modeling of uranium ore formation and use of geological space for radioactive materials isolation.

Геология рудных месторождений. 2019;61(4):3-14
pages 3-14 views

Anorthosites of the low-sulfide platiniferous horizon (Reef I) in the upper riphean Yoko-Dovyren massif (Northern Cisbaikalia): new data on the composition, PGE-Cu-Ni mineralization, fluid regime and formation conditions

Orsoev D.A.


The carried out studies based on new data allowed to give mineralogical, petro- and geochemical characteristics to anorthosites, which are the main link and the major concentrator of PGE and Au in the composition of low-sulfide platinum metal mineralization, localized in a specific taxitic horizon (Reef I) of the Yoko-Dovyren massif. The revealed features of the composition and structure of this horizon indicate that the formation of anorthosites is caused by both the actual magmatic and the late- and postmagmatic processes with a high activity of volatile components. The horizon occurrence can be explained in terms of the “compaction” hypothesis and thermal shrinkage phenomenon. At the boundary of the rocks contrasting in composition and characteristics, when they are cooled, weakened zones form up to cracks and cavities, into which the interstitial leucocratic melt and volatiles squeezed out of the underlying horizons of the massif sucked as a result of the decompression effect. The revealed patterns of changes in the compositions of Pl (82-88% An), Ol (78-81% Fo), Cpx (40-44% En, 9-18% Fs, 41-47% Wo) and Opx (74-78% En, 16-24% Fs, 2-5% Wo) indicate fractional crystallization of the detrital melt. The processes of fluid-magmatic interaction led to a considerable heterogeneity of anorthosites and other rocks, the formation of disequilibrium mineral associations and concentration of ore-generating components. Sulfide associations are considered as products of the subsolidus transformation of solid solutions (mss and iss + poss) formed during the crystallization of an immiscible sulfide liquid enriched in Cu. It is demonstrated that noble metals were associated not only with a limited amount of sulfide liquid. The major part of noble metals with “crust” components (Sn, Pb, Hg, Bi, As, Sb, Te, S, etc.) entered the anorthosite cavities along with volatile components and chlorine, thus causing an abundance of native minerals among platinoids. The decisive role of reduced gases (H2, CH4, CO), H2O and Cl in the genesis of precious metal minerals is estimated.

Геология рудных месторождений. 2019;61(4):15-43
pages 15-43 views

Magmatic control of gold mineralization in Western Primorye (by geophisical data)

Kononets S.N., Valitov M.G., Kharchenko T.A.


An analysis of the regional gravitational field of the north-east of China, Korea and Western Primorye was carried out. The distribution of gold deposits was compared with the development of Mesozoic magmatism and negative anomalies of the gravitational field. Based on the analysis of geological, mineragenic, petrophysical and geophysical materials, geological and geophysical zoning of the western part of the Khanka massif was performed, and a scheme for interpreting geological and geophysical data with elements of minerageny was drawn up. A connection was established between the anomalies of the magnetic and gravitational fields and the position of the supposed gold-bearing ore regions and nodes located in the zone of joints of the North China Triassic-Jurassic volcanic-plutonic belt with the Proterozoic substrates of the Khanka massif. According to geophysical data, Early Jurassic intrusions were identified as, controlling the location of the gold nodes. It was concluded that the gold mineralization is related to the Jurassic magmatism, which increases the prospects for the discovery of gold mineralization in the Khanka district of the Western Primorye.

Геология рудных месторождений. 2019;61(4):44-60
pages 44-60 views

Ore potential of granitic rocks of the Gargan block, Eastern Sayan

Efremov S.V., Dril S.I., Goryachev N.A., Levitsky I.V.


Based on the analysis of modern genetic models, an algorithm for extracting the derivatives of potentially ore-bearing magmas among Precambrian rocks of the tonalite-trondhjemite-granodiorite associations (TTGA) is developed and tested. The algorithm is implemented as a sequence of geochemical criteria to identify the genetic nature of the sources of substance and on this basis to distinguish the products of melting of geochemical reservoirs enriched in Au and other ore elements. The proposed algorithm (a set of potential geochemical criteria of ore content) can be used for metallogenic zoning of TTGA rocks, within ancient cratons.

Геология рудных месторождений. 2019;61(4):61-71
pages 61-71 views

Mineral associations and Mo-W ore types of the Slepaya Zalezh' orebody at Tyrnyauz deposit

Gramenitskiy E.N., Kononov O.V.


Slepaya Zalezh is the largest ore body of the Tyrnyauz Mo-W deposit. It is the priority object on the renewal of its operation. A dissemination of molibdoscheelite, scheelite and molibdenite, controling ore concentrations, is confined to metasomatic rocks of the productive stage, laid on skarns, near-skarn rocks, hornfelses and marbles. The types of the ores are divided accordingly of ratio in them of different facies of ore-bearing metasomatic and initial rocks, which is a working out mass of ore. 7 types of the ores are divided and maped on the ore body vertical projection. Aposkarn ores predominate clearly in the I and II types, accordingly laid over endo- (substituting hornfelses) or exo- (apomarble) skarns. In the III type there are ores laid over endo-skarns and near-skarn rocks in equal parts. Relative to it the type IV contain less of of near-skarn rocks, but more of hornfelses. Ores replacing exo-skarns and to a lesser degree (up to 25%) – marbles dominate in the V type. The type VI is an intermediate one between the types III and IV. In the type VII all initial rocks are presented. Every of the types has a stable mineral and chemical composition inherited from the initial rocks. The ores of the specific type have convenient simple distinguishing features for a hand sorting of specimens, samples, and a preliminary ore separation. The types of ores have narrow change limits in size and form of ore mineral grains and their intergrowthes, percentage of minerals harmful for the flotation. Minor differences in contents of the useful components of each ore type offer possibilities of their selective working off and burdening. Mapping results contain data of the distribution of accompany sorts of mineral resources: garnet and wollastonite in the skarns and productive metasomatic rocks, pyroxene-plagioclase near-skarn rocks and hydrothermal alterated rocks with Cu, Au and other mineralization.

Геология рудных месторождений. 2019;61(4):72-91
pages 72-91 views

The new Massadou diamondiferous kimberlite field in Guinea

Afanasiev V.P., Nikolenko E.I., Glushkova N.V., Zolnikov I.D.


A new kimberlite field, called Massadou, has been discovered in southeastern Guinea near Macenta city. The field consists of numerous ~1 m thick kimberlite dikes with low diamond contents; altogether 16 dikes have been found so far. Mineralization occurs along a 600 m wide zone distinct in satellite images, which is oriented in the same way as the K4 kimberlite reported by Huggerty. The Massadou kimberlite is covered by a thick laterite weathering profile. Main kimberlite indicator minerals found in the area are pyrope, chromite, and ilmenite. The latter occurs as zoned grains with a high-Fe core (hemoilmenite) surrounded by a parallel-columnar aggregate in the rim. The aggregate has a composition of ordinary kimberlitic Mg ilmenite and results from interaction of hemoilmenite with the kimberlite melt. The kimberlite age is estimated as 140—145 Ma by analogy with the surrounding fields. The dikes independent products of kimberlite magmatism in the Guinea-Liberia shield rather than being roots of pipes as interpreted by Skinner (2004). Therefore, the erosion cutout is moderate, and there are no reasons to expect the presence of large and rich diamond placers.

Геология рудных месторождений. 2019;61(4):92-100
pages 92-100 views

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