Large-scale and detailed forecast maps, methods for compiling them
Large-scale and detailed forecasting is completed by compiling a forecast karg of scales 1: 50000 (1: 25000) and 1: 10000 ... 1: 2000. The initial materials for them are:
& gt; maps of geological, geophysical, exploratory study of the territory,
& gt; maps of aerial photo interpretation,
& gt; structural-tectonic map and lithologic-stratigraphic columns, sections,
& gt; hole map,
& gt; map of secondary geochemical anomalies,
& gt; gravimetric, magnetic, electrometric maps,
& gt; map of minerals,
& gt; maps-schemes of depth sections of productive structures and horizons.
Schemes of paleotectonic, paleofacial, paleovolcanic reconstructions are compiled. The results of hydrochemical, biochemical, atmo- chemical, thermobarogeochemical studies are summarized. The model of the forecast object is refined and all the results are displayed on the map of the prerequisites, features of mineralization and on the forecast map (see Figures 24, 41).
Fig. 41 . Geophysical anomalies over hidden ore bodies
(according to VV Aristov, 1975).
I - deposits that create distinct magnetic anomalies: a - a plan for the isodines of a magnetic survey, b a section of the magnetite deposit buried under a platform cover of loose sediments; over the field, distinct magnetic anomalies. II - deposits creating complex geophysical anomalies: a - plan of gravity (dashed lines) and magnetic (solid lines) anomalies of iron ore KMA, b - section of deposit buried in Precambrian basement by iodine of Paleozoic platform cover
Methods for compiling large-scale and detailed forecast maps
Maps of geological , geophysical , exploratory of the territory include a list of works performed in the area on the appropriate scale. They are made in the framework of nomenclature sheets for each type of work and are accompanied by a catalog of used materials (Figure 42).
Fig. 42. Map of geological study of the Kyzyl-Tashtygsky deposit area (according to OI Orekhova):
1-4 - geological exploration and detailed search by a set of methods (1 - exploratory and prospecting and evaluation works at the Kyzyl-Tashtygsky deposit on a scale of 1: 2000, VI Berman, 1956 1964, 2 - search and prospecting - Evaluation works on the southern part in the scale of 1: 2000 NS Bukharov, 1965, AD Toporkov, 1972-19X3, 3 - areas of prospecting works of scale 1: 10000 by geological survey methods, EP electrical survey, geochemical sampling on secondary aureoles and opening of anomalies with mine workings, PE Yegorchenkov, 1969, 4 - geological survey of scale 1: 10000 in a set KSE with magnetic prospecting and geochemical sampling of unconsolidated sediments on the network 100 * 20 m, AD Toporkov, 1973); 5-7 - geochemical prospecting (5 - testing of loose sediments on a 100 * 20 m network, VA Gabeev, 1967, MA Zhukov, 1969, 6 - testing of loose sediments on the network 100 * 40 m , A.Yu. Toporkov, 1987, 7 - testing of loose sediments on the network 250 * 50 m, AD Toporkov, 19X7); 8-15 - geophysical prospecting (X - electrical reconnaissance using the EP method via the 50 * 10 m network, 9 - electrical reconnaissance using the EP method over a network of 100 * 20 m, 200 * 20 m, VA Golev, ZA Kunda. ., VA Podrugin, MP Zyuzin, 1967, 10 - electrical reconnaissance by the method of combined electrical profiling on the network 100 * 20 m, IA Golovin, 1959, 11 electrical reconnaissance by the charge method of scale 1: 2000 and 1: 5000, IV Golovin, 1959, 12 - gravimstroevaya survey of the network 250 * 50 m PE Yegorchenkov, MP Zyuzin, 1959, 13 - electrical exploration by induction of scale 1: 2000 , IA Golovin, 1959, 14 - magneto-prospecting on the network 500 * 100 m, NS Bukharov, 1987, MP Zyuzin, Yu.G. Ivanov, 1977, 15 - aeromagnetic and gravimetric survey of the whole area on a scale of 1: 25000. Southern geophysical expedition, 1987)
Aerial photo interpretation maps reflect the variety of sculptural forms of terrain identified by remote studies. New structures are discovered, which were unnoticed by terrestrial geological and geophysical work, but play an important role in the placement of mineralization (Figures 36, 43). Such structures include tectonomagmatic, ring volcano-plutonic, subvolcanic, caldera, volcanic vents, extrusions, latent faults, fracture zones of rocks, metasomatism zones, granite-gneiss domes, shock-meteorite formations
Fig. 43 . The deep structure of the Estyuninskoye deposit based on the modeling of materials of aeromagnetic surveys
(according to A. N. Avdonin et al., 1987):
1 - the value of the magnetic susceptibility ac, n (4l) 10 " SI; 2 - contour of ore bodies for mathematical modeling; 3 - the contour of magnetic foams; 4-6 - ore bodies: 4 - established before 1970; 5 - identified in 1983; 7-8 - DT curves: 7 - observed, 8 - calculated from the model of the deposit; 9 - values of field measurement heights, m
Aerogammaspectrometric survey allows contouring of anomalies and zones of alkaline metasomatism with possible gold-rare metal mineralization. Aeromagnetic and gravitational anomalies may indicate the largest magnetite-hematite deposits in ferruginous quartzites. In addition to the search function, remote methods provide the material for the compilation of the structural and mineralogical basis of prediction.
Structural-geological map is compiled on the basis of structural-tectonic studies in the region. It shows stratigraphic subdivisions in accordance with the achieved detail of the dismemberment-the stage, the suite, the subsuite, the stratum, the horizon with petrographic-lithological filling. Folded structures are displayed by stratozoliniums indicating elements of bedding, strata, strike, and declination of fold axes (Figures 44, 45). Discontinuous structures, their types and morphological features are reflected. The faults are divided in scale (1-4 orders), age (reflecting the time of establishment and renovation), the nature of the formed structural blocks and their role in oreogenesis. Morphological features of magmatites accompanying contact metamorphites, metasomatites, deposits of deposits and ore occurrences are shown. Intrusive complexes are distinguished, the main and additional phases, vein, facies of rocks, unified on the basis of quantitative-mineralogical and petrochemical classifications. The map should reflect the position of mineralization in geological terms, links with magmatism, metasomatism, placement in tectonic structures, including volcanic-plutonic, terrane (Fig. 45). Such a map allows us to develop geological prerequisites and indications of industrial ore content in the area.
Fig. 44. Geological structure models of ore region (a) and ore zero (b) of Kempirsai type
(Comprehensive .... 1986).
1 - troctolite, gabbro; 2 - intermittency of apodunite serpentinites, verlites, pyroxenites; 3 - apogartzburgitic serpentinites; 4
- intermittency of apodunite and apogartzburgite serpentinites; 5 - apoduntic serpentinites; 6 - non-serrated ultrabasites; 7 - enclosing volcanic-sedimentary rocks; 8 - tears with intense serpentinization; 9 - near-ore serpentinites; 10 - solid and gustovkplennye ore; 11 - medium and poorly graded ore; 12 - chromite ores: a -stratiform low chromite hromntites; secant (b) and stratiform (in) high chromite ores
The " reflects the results of the mineralogical analysis of the schlich samples. Anomalous zones and areas of high content of minerals in loose sediments are distinguished on it. It reflects the general mineralogy in the region.
Geochemical maps . Geological basis includes secondary lithochemical haloes, scattering flows, primary lithochemical anomalies, hydrochemical, biochemical, atmo- chemical data and all ore loading. The metals and accompanying elements of the expected mineralization are reflected. This creates a theoretical basis for analyzing the geological position of the anomalous sections and revealing their interrelations with ore-bearing structures. The nature of specific anomalies and their potential for industrial mineralization are determined. Intensive complex mineralogical-geochemical anomalies usually outline areas of deposits and manifestations. Less intense but broad anomalies are combined with the boundaries of ore fields and zones of hydrothermal metasomatism with productive mineralization. The halos of the accompanying elements allow us to judge the levels of erosion cutting of ore fields and deposits (Figures 23, 46-48). Fig. 45. Scheme of placement of kidney and contact metasomatic formations in the contact aureole of the Lower Paleozoic granitoid intrusion (Solgonsky Massif) of the Kuznetsk Alatau (Kommunarovskoe ore field)
(according to AF Korobeinikov, LG Osipov).
1 - upper Proterozoic, midday suite, PR3pl; 2 - diabase, porphyrites; apodiabasic albite-chlorite shales; 3 - lithoclastic tuffs of the main effusives; 4 - gabbro-diabase, gabbro-diorite of syllable bodies. PR & quot ;; 5 - gabbro-porphyritic dykes; 6 - diorites, gabbro-diorites, сениенито-диориты, гранодиориты of the Solgonsky massif Є3-О; 7-gabbro, metasomatic hornblendites, Є3-O; 8 - granites of the Lower Paleozoic complex, Є 3 -О; 9 - dykes of diorites, diorite porphyrites, lamprophyres. ЄZ-О; 10-dyke append, pegmatite, quartz diorite porphyry. orthophyres. Є3- О; 11 - zones of schist formation; 12 - zones of milinitization and crushing of rocks; 13 - gaps traced and suspected; 14 - geological boundaries established and presumed; 15 - elements of occurrence of rocks; 16 - elements of schist formation; 17 - banding of igneous rocks; 18 - plan-parallel texture of rocks; 19 - zones of hornfels; 20 - contact-metasomatic rocks (skarns of calcareous and post-scark amphibole-carbonate-chlorite metasomatites); 21 - skarn-magnetite lenses; 22 - gold-bearing skarn-magnetite bodies: 1 - Northern lens, 2 - South lens, 3 - Ninth lens
Fig. 46. Mono-element anomalies of gold in the Saralin ore field
(by AF Korobeinikov ):
1 - carbon terrigenous-volcanogenic strata of the Lower Cambrian; 2 - granitoids of the Ararat Massif Є 3 ; 3 - tears; 4 - 6 - halos of gold in bedrock; 4 - 11-15 mg/t Au, 5-5-10 mg/t Au, 6 - up to 3-5 mg/t Au
Fig. 47 . Geochemical zoning of the Central ore field
Geophysical maps are compiled on the basis of geophysical surveys of scales 1: 50000 and 1: 25000 and are corrected by results of more detailed geophysical work. The analysis of gravimetric and magnetometric maps makes it possible to clarify the characteristics and structure of magmatic, metasomatic complexes, to reveal hidden faults and belting belts, latent intrusions, zones of hybridism, contact metasomatism, the manifestation of magmatic masses at deep horizons, regularities in the location of ore objects in geophysical fields (Fig. 29, 49, 50). Such maps are used in the creation of paleotectonic, paleofacial, paleovolcanic reconstructions and serve as the basis for compiling the cargas of the deep structure and for isolating productive horizons. The results of interpretation of geophysical fields, anomalies, plotted on the map, are used to refine forecasting and search criteria and attributes.
Fig. 48. Models of geochemical zoning of the Central gold ore field, vertical sections
(by Voroshilov ):
1 - the contour of the Central granitoid massif; 2 - directions of movement of paleo-hydrothermal streams; 3 - contour of endogenous geochemical halos: a - in quartz-feldspar auto-metasomatites; b - in berezites with quartz-arsenopyrite-molybdenite-scheelite early veins; in - in berezites with quartz-gold-polysulphide veins
Fig. 49. Petrophysical and ore zoning of the Olkhov granitoid protuberance:
1 - the contact of the granitoid protrusion (arrow on the contact falling); 2 - the same, under the enclosing rocks; 3 - boundaries of petrophysical zones; 4-8 - granitoids of different magnitudes: 4 - low magnetic, 5 - moderately magnetic, 6 - high magnetic, 7 - anomalous magnetic, 8 - reduced magnetic; 9 - limestones, marbles, volcanic-sedimentary rocks; 10-13 - transformation of rocks; 10 - graphitization, 11 - marble. 12 - skarning, 13 - homatization; 14 - the border of the belly belt; 15 - deposits: a - contact-metasomatic, b - quartz-viable. II-III - variational curves of magnetic susceptibility of granitoids: I - biotitized, silicified podrudnyh, II - ore-bearing; III - albitized podrudnyh
Fig. 50. Magneto-geological position of a vein deposit in a granodiorite massif
(by AF Korobeinikov and others):
1 - gold-quartz-sulphide veins; 2 - K-feldspar and Kaleshpat-epidote metasomatites according to geological and geophysical data; 3-5 - isolines of the averaged magnetic field: 3 - zero, 4 - positive, 5 negative
Such maps are used in the creation of paleotectonic, paleofacial, paleovolcanic reconstructions and serve as the basis for drawing maps of deep structure and for isolating productive horizons. The results of interpretation of geophysical fields, anomalies, plotted on the map, are used to refine forecasting and search criteria and attributes.
Maps of deep sections of productive structures represent a series of schematic horizon plans for a prospective area with a step of 100 ... 300 m vertically. The basis of such sections is the geological-structural map, reference wells, geological-geophysical reference sections, gravimetric, magnetometric maps and the results of their geological interpretation. The main ore-bearing structures - ore-supplying, ore-localizing faults, intrusions, metamorpho-intrusive domes, volcanic-tectonic, folded local forms, ore-bearing horizons, geological screens, zones of metasomatism with ore mineralization are carried to these sections. The combination of map charts and basic geological and physical profiles makes it possible to identify the features of the geological structure of a potentially ore-bearing structure as a three-dimensional figure and reflect the prospects of its deep horizons (Figures 34, 51, 52).
Fig. 51. Map of local forecast map of copper-pyrite deposits (according to AI Krivtsov):
1-3 - super-ore space: 1 - peripheral (NRP), 2 - flank (NRF), 3 - proper super-ore (NRM); 4-5 - ore space: 4 - flank (RF), 5 - ore (PM); 6-8 - podrudnoe space: 6 - the actual pearl (PRM), 7 - (PRP); 8 - ' peripheral (PRP). The numbers in the circles of the g line, equivalent to the variants of the erosion cut
Fig. 52. Vertical section of a geometrized model of pyrite family deposits (according to AI Krivtsov):
1 - flanking metasomatic zones; 2 - pyrite deposits and metasomatites of rare space; 3 - podrod metasomatic zones; 4 - the boundaries of the distribution of metasomatites; 5 - variants of location of erosion cut with different perspectives
The map of forecasting and search criteria contains all the information on the patterns of mineralization and reflects the established ore-bearing structures, zones and facts indicating the possibility of discovering new ore objects in the territory ore deposits, ore deposits within previously identified ore fields. On the maps of ore fields, specific ore sites, ore bodies are noted. The map summarizes all the geological prerequisites for forecasting and searching for industrial mineralization - geophysical and geochemical anomalies, schist halos, metasomatic zones and hydrothermalites. To develop a scale of significance criteria and signs of forecasting, it is necessary to analyze typical deposits of the area and develop models of objects of different ranks. Models of real and predicted ore objects (ore fields, deposits) are used to estimate the scale of the expected mineralization.
There are three groups of forecasting and search criteria on the map. Their significance for the localization of industrial mineralization is reflected:
1) stratigraphic, lithologic-facial - sections of the strata, sediments, facial types of deposits favorable for mineralization, ore levels and mineralized horizons of rocks, layers of ore-clastic, fluidites, geological-geochemical screens, etc.
2) structural-tectonic indicators - ore-bearing folded, volcanotectonic structures, magmatic ore supply, ore-distributing, ore-concentration, ore-localizing faults, their feathering rills, zones of schistose;
3) magmatic factors - ore-bearing intrusives, stocks, dikes, their contact areas, explosive-hydrothermal breccias, volcanic-plutonic structures. There are direct and indirect signs. The first include exits, subsections of minerals, primary and secondary halos and fluxes of scattering of minerals, ore elements. To the second - minerals-satellites of mineralization, geophysical anomalies, hydrothermally altered rocks, archaeological data. The significance of all geological factors is estimated in points on the computer.
Such a map serves as the basis for compiling a forecast map.
Large-scale and local forecast maps contain the selected ore-prospective areas and sites for setting search, evaluation works of the first, second, third order (Figures 26, 35, 36, 38) .
Large-scale forecast maps are compiled on a scale of 1: 50000-1: 25000. The fulfilled forecasting provides allocation of ore-prospecting areas corresponding to the ranks of the ore field or ore site. Analysis of forecasting and search criteria and attributes when taking into account models of ore objects is the basis for constructing a forecast map. As in the case of medium-scale forecasting, the method of geometrical zoning of ore factors based on a square grid is used. The cell dimensions should ensure the reliability of the allocation of the minimum size of the projected ore object and make up 2x2 cm or 4x4 cm on the map scale. To refine complex sections of the map, use the sliding window method. Gradations of the scale are justified using reference ore objects known in the region under study. The isolines that outline the area of the reference objects serve as the boundaries of the prospective areas of the corresponding rank. The allotted sites are differentiated according to their rank and degree of prospects, reflecting the type and size of the expected ore fields, deposits, the sequence of subsequent prospecting operations required to implement the forecasts. The final stage of forecasting is the calculation of the forecast resources by categories P2 and P1, and their geological and economic assessment is given. Perspective sites on the forecast map are numbered, in their contours are the categories of resources and their quantities.
Detailed forecasting is performed within known ore fields, ore zones, ore prospecting sites in scales 1: 10000 ... 1: 1000. These tasks solve the problem of assessing the industrial prospects of previously established ore-bearing structures with the aim of optimizing the direction of further prospecting, evaluation or exploration work. Such tasks define the set of represented graphics and its content. The set of submitted schedules for performing detailed forecasting includes the following documents:
1. The position of the ore field under study or the perspective zone, the structure of the region, and its regular connections with elements of the geological structure.
2. Zoning of the ore field, the perspective zone, the structure, the deposit according to the degree of exploration by geological, geophysical, geochemical methods.
3. Geological and lithological features of the perspective object. On the geologolithological map, in a single legend, detailed materials on stratigraphy, lithology, structures, magmatism, metasomatism are reduced. The map is the basis for making special cuts, projections, etc.
4. Placement, internal structure, composition of the zones of hydrothermal metasomatism - from contact and to late hydrothermal differences. Detailed dismemberment of metasomatites provides for the allocation of zones of pre-ore, syndrome and post-ore transformation of ore-bearing rocks. Their connections with geological structures are reflected and zonal placement of different types of metasomatites in the general structure of the ore field is shown. Such maps reveal the links between hydrothermal-metasomatic processes and mineralization.
5. Structural-mineragenic features of the ore field, ore zone, deposit or promising area. Such a specialized map reflects the heterogeneous structure of the object, folded and discontinuous structures, magmatic and metasomatic associations, their facial varieties, as well as ore horizons, geological screens, mineralization zones, ore bodies or their projections (for hidden bodies). The map shows geophysical and geochemical anomalies reflecting ore-bearing structures and zones of productive mineralization.
6. The systems of transverse and longitudinal geological sections are reconstructed, special block diagrams giving representations of the volumetric internal structure of the ore object.
7. Elements of ore-magmatic or ore-metasomatic zoning of the ore field, characterizing the formation and internal structure of the former ore-forming system.
Other methodical methods for compiling complex large-scale and detailed forecast maps were developed, including using geological modeling on a computer. For example, interactive and automated computer forecasting systems, as well as simulation programs for geochemical prospecting of mineral deposits.
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