Petrophysical zoning of the Natalka ore field

Шарафутдинов, В. М.; Khasanov, I. M.; Михалицына, Т. И.

doi:10.1134/s1819714008050072

Cited by 3 publications

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“…Productive (and arsenopyrite) mineralization at these deposits is isolated from the areas of the most magnetic (pyrrhotinized) rocks. This universal mineralogic and petrophysical zoning was observed at deposits with gold-arsenopyrite-pyrite-pyrrhotite ores in different regions and for different metallogenic epochs: the Chertovo Koryto deposit (Patom Upland, Riphean), the Natalka deposit (Yana-Kolyma folded area, Mesozoic), and others (Kolmakov et al, 2010;Sharafutdinov et al, 2008;and others). In laboratory conditions, this zoning was simulated with the use of a metasomatic column with a gold-bearing pyrite-arsenopyrite paragenesis by the method of "a flow-through reactor" (Obolensky et al, 2011).…”

Section: Genetic Reconstruction Of the Petrophysical Zoningmentioning

confidence: 90%

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

Kolmakov

2014

Russian Geology and Geophysics

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Data on geophysical fields and petrophysical heterogeneity, parageneses and the thermodynamic conditions and age of their formation, and fluid inclusions were used for the genetic reconstruction of petrophysical zoning at the Blagodatnoe gold-sulfide deposit. Petrophysical associations of the preore and ore stages of the deposit formation are clearly reflected in anomalies of the magnetic and natural electric fields and the aureoles of radioactive elements. At the early preore stage (752 Ma), reduced solutions with high activity of K, enriched in U, Th, and, probably, Au, were supplied to intensely foliated tectonic zones. Their interaction with initial metasedimentary rocks gave rise to contiguous zones of quartz-muscovite and chlorite metasomatic rocks. Accompanying graphitization led to a high electrochemical activity of the metasomatic rocks, which generated anomalies of up to -300 mV in the natural electric field; the most intensely carbonized zones became enriched with U (up to 6.5 × 10 -4 %) and, probably, Au. The quartz-muscovite metasomatic rocks accumulated Th and K (up to 29 × 10 -4 % and 4%, respectively), whereas the chlorite metasomatic rocks accumulated rock-forming elements (particularly Fe), which led to the compaction of these rocks and the acceleration due to gravity in local positive anomalies. The nonmagnetic character of the fresh pre-ore metasomatic rocks suggests the predominantly pyritic composition of early sulfides. At the ore stage (698 Ma), the minerals were deposited from H 2 O-CO 2 -As-S solutions at 560 to 315 ºC. The activity of these solutions caused a redistribution of radioactive elements and a high petrophysical differentiation of the ore-bearing structure. The amplitudes of the anomalies above this structure vary from 500 to 80 nT in the magnetic field and from -130 to +10 mV in the natural electric field. It has been found that the hydrothermal fluid hardly affected the polarization properties of graphitized rocks at the maximum temperatures but caused an intense removal of U and the development of magnetic pyrrhotite after pyrite. The temperature decrease in the mineral-forming system was favorable for the formation of siderite. Carbonaceous schists which experienced carbonatization lost their electrochemical activity. The binding of carbon dioxide in the solid phase influenced the migration capability of trace elements and their zonal distribution. With this evolution of the solution, Th accumulated at the lower levels of the mineralized zone, whereas the upper levels of the deposit became enriched with U. Productive gold-arsenopyrite-pyrite-pyrrhotite paragenesis with anomalous magnetic susceptibility evolved at the ore stage. The late galena-sphalerite-chalcopyrite paragenesis (365 Ma) was of strictly local occurrence and reduced the magnetic susceptibility of ores.

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Section: Genetic Reconstruction Of the Petrophysical Zoningmentioning

confidence: 90%

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

Kolmakov

2014

Russian Geology and Geophysics

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“…The occurrence of this intrusive body is validated by physical properties of ore-bearing sedimentary rocks in deep holes, the enrichment of these rocks in pyrrhotite and As-bearing pyrite with depth (Sharafutdinov and Khasanov, 2006;Tyukova and Voroshin, 2007), and an increase in the amount of visible gold and its grain size in this direction (Struzhkov et al, 2006).…”

Section: Geologymentioning

confidence: 96%

The world-class Natalka gold deposit, northeast Russia: REE patterns, fluid inclusions, stable oxygen isotopes, and formation conditions of ore

et al. 2008

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mined out from primary ore and 105 t from the Omchak placer, related to the Natalka deposit. The follow-up exploration of the deposit in 2004-2007 resulted in the estimation of resources at 1760 t with a Au grade of 1.7 g/t (Grigorov, 2006). This deposit is a typical example of orogenic deposits localized in collision belts composed of volcanosedimentary and terrigenous rocks metamorphosed under conditions of greenschist facies (Goldfarb et al., 2005).Abstract -REE patterns of hydrothermally altered rocks, fluid inclusions, and stable oxygen isotopes of quartz were studied at the Natalka gold deposit. Metasomatic rocks formed under decompression reveal gradual depletion in LREE and HREE relative to siltstone of the protolith. The HREE patterns of metasomatic rocks formed under decompression are uniform; an insignificant removal of LREE can be noted. The progressive extraction of REE with increasing alteration of rocks could have been due to the effect of magmatogenic or meteoric fluid. Because a Ce anomaly is absent, the participation of oxidized meteoric water was limited. The inverse correlation between the total REE content and the Eu anomaly value in altered rocks indicates a substantial role of magmatogenic fluid. The REE patterns of altered rocks formed under compression show that the role of metamorphic fluid was not great. All metasomatic rocks are enriched in LREE, so that the enrichment of fluid in LREE as well may be suggested. Three fluid compositions were captured as fluid inclusions: (1) H 2 O-CO 2 -NaCl-MgCl 2 with a salinity of 1.0-4.9 wt % NaCl equiv, (2) CO 2 -CH 4 , and (3) H 2 O-NaCl-MgCl 2 with a salinity of 7.0-5.6 wt % NaCl equiv. Compositions (1) and (2) coexisted in the mineral-forming system at 250-350 ° C and 1.1-2.4 kbar as products of phase separation under conditions of decreasing P and T . The interaction of this fluid with host rocks resulted in the formation of extensive halos of beresitized rocks with sulfide disseminations. The precipitation of arsenopyrite and pyrite led to the substantial depletion of mineral-forming fluid in H 2 S and destabilization of the Au(HS) 2-complex. The fluid with the third composition arose due to the boiling of the H 2 O-CO 2 -CH 4 -NaCl-MgCl 2 liquid and was responsible for metasomatic alteration of host rocks. The late mineral assemblages were deposited from this fluid at the initial stage of ore formation. The high methane concentrations in the ore-forming fluid were likely caused by interaction of hydrothermal ore-bearing solutions with carbonaceous host rocks. The δ 18 O values of quartz from quartz-scheelite-pyrite-arsenopyrite and sulfide-sulfosalt mineral assemblages vary from +11.6 to +14.1‰ and +11.2 to +13.5‰, respectively. The parental fluids of the early and late mineral assemblages probably were derived from a magmatic source and were characterized by δ 18 = +6.3 to +8.8‰ at 350 ° C and +3.6 to +5.9‰ at 280 ° C, respectively. The narrow interval of oxygen isotopic compositions shows that this source was homogeneous. The data obtained ...

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Platinum Group Elements in Arsenopyrites and Pyrites of the Natalkinskoe Gold Deposit (Northeastern Russia)

et al. 2020

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The peculiarities of the distribution and binding forms of platinum group elements (Pt, Pd, Ru, Rh, Os and Ir) in the arsenopyrites and pyrites of the Natalkinskoe gold ore deposit (Northeastern Russia) were examined using atomic absorption spectrometry with analytical data selections for single crystals (AAS-ADSSC), a “phase” chemical analysis (PCA) based on AAS of different size-fractions of minerals, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The arsenopyrites and pyrites of the Natalkinskoe gold deposit were found to concentrate not only Au but also platinum group elements (PGEs) such as Pt, Pd, Ru and Rh. The PCA showed that the highest contents (in ppm) were found in the monofractions of arsenopyrite—Pt up to 128, Pd up to 20, Ru up to 86 and Rh up to 21—and comparably lower in monofractions of pyrite—Pt to 29, Pd to 15, Ru to 58 and Rh to 5.9. The AAS-ADSSC method revealed two forms of uniformly distributed Pt, Pd and Ru corresponding to the chemically bound element in the structure of the mineral and in the superficial non-autonomous phase (NAP). The superficially bound form dominates over the structural form and presumably exists in a very thin surface layer of the crystal (~100–500 nm). The maximum contents of these PGE, chemically bound in the structure of arsenopyrite, reached values of (in ppm) 48, 5.9 and 48; and in pyrite structure, 68, 5.2 and 34 for Pt, Pd and Ru respectively. The contents of Pt, Pd and Ru related to NAP on the surface of the crystal were significantly higher and amounted (in ppm) for arsenopyrite to 714, 114 and 1083; and for pyrite 890, 62 and 690 for Pt, Pd and Ru, respectively. Preliminary results for the Rh form in arsenopyrite crystals suggest that the surface-related form (154–678 ppm) is more abundant than the structural form (17–45 ppm). Data from studying the surfaces of sulphide minerals by SEM-EDX and LA-ICP-MS confirmed the presence of Pt, Pd, Ru and Rh on the surface of arsenopyrite and pyrite crystals. These methods generated primary data on the content of Os and Ir in arsenopyrite and pyrite in the surface layer. The maximum content of Os and Ir found in arsenopyrites was up to 0.7 wt%. PGE-enriched fluids (up to ~3 ppm Pt) may exist in the gold ore deposit. It is assumed that there is a common mechanism of impurities uptake associated with the active role of the crystal surface and surface defects for gold-bearing arsenopyrites and pyrites. The surface enrichment is due to peculiarities in the crystal growth mechanism through the medium of NAP and the dualism of the element distribution coefficient in the system of mineral–hydrothermal solution, which is higher for NAP, compared to the volume of the crystal. Although mineral forms of Pt, Pd, Ru, Rh, Os and Ir have not been found at the Natalkinskoe gold deposit, their existence in the form of nano-scale particles is not excluded. This follows from the evolutionary model of surficial NAPs, assuming their partial transformation and aggregation with the formation of nano- and micro-sized autonomous phases of trace elements. The presence of PGE in the ores and the possibility of their extraction significantly increase the quality and value of the extracted raw gold materials at the Natalkinskoe deposit, and adds to the list of known platiniferous ore formations.

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Petrophysical zoning of the Natalka ore field

Cited by 3 publications

References 0 publications

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

The Blagodatnoe gold-sulfide deposit (Yenisei Ridge, Russia): the nature of geophysical anomalies and the succession and causes of formation of petrophysical zoning

The world-class Natalka gold deposit, northeast Russia: REE patterns, fluid inclusions, stable oxygen isotopes, and formation conditions of ore

Platinum Group Elements in Arsenopyrites and Pyrites of the Natalkinskoe Gold Deposit (Northeastern Russia)

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