Petrologic and geochemic features of the ore-containing substratum in hydrothermal gold deposits. Part 1. Petrology of the near-ore metasomatism

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The relevance of the research is caused by the necessity to correct and elaborate on geological (metallogenical) component of the hydrothermal gold deposits formation theory within the framework of which the conflicting ideas about ore-formation geological making (energy and metalliferous fluids sources) go in four competing hypotheses eliminating one other. Therefore it is impossible to develop a complex of effective forecast-search mineralization criteria. The main aim of the study is to prove the belonging epigenetic mineral associations at the ore-formation stage in near-ore alterating black shales series to metasomatic formations, contrary to the wide-spread ideas, and, as consequence, material-genetic similarity of apoblackshales zoning metasomatic columns (haloes) with those, formedin non-shale (crystalline) substratum; external (non-rock) sources of gold and other metals, concentrated in deposits formed in black shales series. The methods used in the study: 1) formation of geological cross sections of near-ore metasomatic haloes (columns) with selection of multipurpose samples (mass 1,5-2,0 kg); 2) preparation of samples for analysis in licensing laboratories; 3) diagnosis up to a species of minerals chemical compositions using optical and electron microscopes; 4) complete chemical silicate analysis of rocks samples; 5) atomabsorption (sensitivity 1.10-8 wt. for gold, silver, 5.10-7wt. for mercury), controlling neutron-stimulate, chemical-spectrum analysis for gold (sensitivity 1.10-8and 3.10-8 wt. accordingly); 6) petrochemical conversions of the results of complete chemical silicate rock analysis in volume-atomic method; 7) balance calculations of petrogenic chemical elements migration in near-ore metasomatic columns; 8) calculations of statistical parameters of metal distribution and balance in near-ore expanse of deposits using two-level system of selections, to ensure reconstruction of chemical elements geological history and proper appraisal of donor potential of the rocks including black shales. The results. In sixteen gold-ore deposits of south mountain-folded frame of Siberian craton two-, three-stage history of formation of non-shale and black-shale ore-bearing substratum was reconstructed and common petrologic-geochemical model of near-ore zone metasomatic haloes (columns) was developed. The haloes represent a combination of beresitic and propylitic formations in inside, intermediate chloritic and frontal zones accordingly. Polymineral composition of rear (beresite) zone, different from two-component (quartz, sericite) composition of the theoretical model (D.S. Korzhinsky), is formed in rock-fluid system, opened to carry out (Na, Si) and addition of components coming with metalliferous fluids from outside and fixed into own mineral new-formations and as trace elements mainly in inside zones. According to balance calculations potassium (sericite), reduced sulphur (sulphides), oxidized (carbonates) and reduced (kerogen, hydrocarbons) carbon, oregenous (Au, Ag, As, Hg and other) and petrogenous elements including femic Ti, P, Mg, Fe, Ca, Mn come into haloes and ores. The contrast of anomalies reaches many hundreds and thousands per cents. Ti and P form their own mineral phases - rutile, leucoxene, apatite, Mg, Fe, Ca Mn form a part of carbonates, other metals are concentrated in proper minerals and admixtures. Distribution of gold and accompanying metals in near-ore space is subject to metasomatic zoningnear-ore geochemical haloes always take up lesser volumes comparatively with the near-ore metasomatic ones. It is expressed in subclark contents (0,5-1,2 mg/t) and low distribution dispersion of gold, silver, mercury in various rocks, including black shales regionally metamorphosed on muscovite-biotite paragenesis level outside and in weak alteration subzone of frontal zone of near-ore metasomatic haloes, and in sequential increase of these parameters, as well as Au-Ag-relation and correlative connections between gold and silver from one mineral-petrochemical zone to another at intensification of near-ore metasomatic rocks alterations with achievement of maximum quantities in rear zone the more the higher metal contents in ores. The results obtained prove the material-genetic similarity of derivatives of ore-formation processes in non-shale and black-shale substratum and sinore origin of contrasting geochemic anomalies (their beyondclarc contents) in near-ore mesothermal gold deposits space. The first part of the paper introduces the results of study of near-ore metasomatic haloes (columns). The second part introduces the results of the study of oregenous (Au, Ag, Hg) elements distribution in near-ore space, the petrologic-geochemic materials are discussed and the conclusions are stated.

Original languageEnglish
Pages (from-to)55-68
Number of pages14
JournalBulletin of the Tomsk Polytechnic University, Geo Assets Engineering
Issue number4
Publication statusPublished - 2016


  • Black shales
  • Crystalline (non-shale) substratum
  • Geochemic haloes
  • Hydrothermal gold deposits
  • Near-ore (ore-containing) zoned metasomatic

ASJC Scopus subject areas

  • Economic Geology
  • Geotechnical Engineering and Engineering Geology
  • Fuel Technology
  • Management, Monitoring, Policy and Law
  • Waste Management and Disposal
  • Materials Science (miscellaneous)

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