Archival data collection and arrangement; electronic database development; exploration data analysis by results of the foregoers; ALS/SLS decoding; landscape indication, structural and tectonic analysis with outlining of prospecting prerequisites and signs.
The methods of morphometric and neotectonic simulation are based on the principles of morphometric analysis by Filosofov V.P. adjusted to modern digital data on the relief surface.
Filosofov’s morphometric analysis methods have been refined and adapted to modern digital data and the scale of research. At the present stage, almost all methods of morphometric analysis are integrated into modern computer technologies of Spatial Analysis by means of the analytical apparatus of geographic information systems (GIS).
The main objectives of morphometric and neotectonic simulation are:
1) obtaining of an informational basis for interpreting geological and geophysical data;
2) the selection of morphological structures of different genesis for purposes of prospecting and exploration of mineral resources;
3) paleoreconstruction and morphotectonic analysis of neotectonic conditions based on the morphometric simulation;
4) localization of possible zones of mineralization in the studied areas that reduces the time for exploration and verification drilling and reduces the scope of exploration.
The task to be addressed during simulation is to obtain the following data:
1) creation of a topologically correct large-scale digital relief model (hereinafter referred to as DRM) based on radar satellite survey and topographic base;
2) decoding of visible tectonic dislocations of the Earth’s crust based on materials of Remote Probing of the Earth (hereinafter referred to as RPE);
3) geomorphological analysis of the territory;
4) morphometric analysis and simulation of orogenesis and tectogenesis at various stages of the modern relief formation;
5) making a morphotectonic model of the territory under study;
6) allocation of residual structures and degree of denudation.
The work results in the models of ancient geological structures:
1) paleoreconstruction of orogenesis with allocation of morphotectonic structures;
2) allocation of residual structures and degree of denudation, as the basis of the forecast model.
Geological study of the territory begins with a preliminary stage. Experts of our company study archival geological materials of the studied territory and nearby regions. Therefore, even before starting the field work, geologists form a spatial model of geological structure of the site to be surveyed that makes it possible to identify promising areas for primary and placer types of deposits.
As the field geological routes begin, the study and large-scale mapping of areas identified as promising, as well as implementation of geological routes through a pre-approved network, is performed. A description of the outcrops, sampling for various types of field and laboratory analyzes, mining, description and documentation of the mines.
Field data is being office processed, the results of which correct the further exploration program.
Geochemical studies help outlining and localizing prospective areas for the presence of mineral resources. Investigations by dispersion areolas of the material composition and accessory elements. Implementation of geochemical survey, data analysis, geochemical anomaly mapping represents an important stage of the exploration. Analysis and re-interpretation of the results of geochemical works by predecessors.
Our Company is focused on modernization and application of field exploration methods, highly confident and fast in execution, to the exploration train that allows us to solve certain exploratory tasks of the Customers under various geological conditions due to innovative high-precision proximity geoelectric prospecting methods, which is predominant in our production train, and classical contact geophysical techniques. Our Company owns a wide spectrum of contact and proximity equipment for geoelectric prospecting meeting all modern safety and magnetic compatibility requirements.
Geophysical electric prospecting methods based on the study of changes in the electromagnetic field due to its artificial excitation by grounded electrodes, along which direct or alternate current is applied. Contact geoelectric prospecting methods are widely used to search for mineral resources, both metallic and nonmetallic, water bearing zones and aquifers, increased mineralization zones, tectonic zones, karsts, etc.
RESISTIVITY TECHNIQUE – VES; ELECTROTOMOGRAPHY
The method of vertical electrical sounding (VES) is based on the study of the apparent electrical resistivity of rocks with galvanic direct contact induced by electromagnetic field of a generator. This allows obtaining characteristics of electrical conductivity of rocks and measuring changes in the electromagnetic field of the rock.
Different rocks and their different states show different electromagnetic characteristics; hence, this changes the electrical amplitude, which is converted to electrical resistance (R). Based on this data, you can model vertical profiles.
VES, the vertical electrical sounding, allows us to carve up a profile between two measured points.
Electrotomography is a modification of VES and differs from it by a more detailed field observation method, in which the observation points form denser network. The electrotomography method allows obtaining a higher resolution profile.
Hardware complexes based on the study of electrical resistance of rocks are single-channel or multi-channel (multi-electrode). The range of generators and recorders covers from unit Hertz to unit Kiloherz. The depth of research is influenced by the generator power and the length of line to be measured (the distance between the electrodes). The current is alternate or direct.
POLARIZATION METHOD – EP, IP, IP-VES, IP-SG, IP-DP; ELECTROTOMOGRAPHY
The EP method of the natural field allows you to measure changes in the electromagnetic field of the rock during direct galvanic contact without any induced field.
The IP method of induced polarization makes it possible to measure changes in the secondary electromagnetic field of the rock with direct galvanic contact, with a generator-induced electromagnetic field generated by the secondary electric charges.
The range of generators and recorders is from units to hundreds of Hertz. The depth of research is influenced by the generator power and the length of line to be measured (the distance between the electrodes). The current is alternate or direct.
Measurements are made during and after application of electric current; the ratio of these voltages is expressed in percent (%).
The IP effect is more noticeable if electron-conducting minerals are present in the medium and have an increased electrical capacity as compared to the enclosing medium.
Modern recorders allow you to measure and calculate two methods, IP and VES, simultaneously.
EXCITATION-AT-THE-MASS METHOD – EM, CBM (charged body method)
It is used in ore geoelectric prospecting at the exploration stage and allows assessing dimensions of ore bodies and their occurrence elements; determining connections between individual ore occurrences exposed by different mining operations; searching for new ore bodies in the vicinity of the exposed ones;
The essence of the method is in the study of the electric field reaction formed by an electrode in contact with the body under study, which has a higher conductivity than the host rocks. In this case, the body under study becomes the field source itself, and this field provides information about its properties and geometry. Characteristics of the electric field are measured in the areas of sharp contrast of the specific electrical conductivity of the studied objects and host rocks, if the objects have elongated or close to isometric shapes (veins or lenses) and at any occurrence of them up to the horizontal. Successful work performance requires good grounding conditions of the receiving circuit.
Proximity geoelectric prospecting is an alternative method of classical contact gejelectric prospecting for solving geological problems under severe conditions, where the use of the grounding principle is impossible or inefficient. Proximity geoelectric prospecting methods are used to search for mineral resources of various types and genesis, water bearing zones and aquifers, increased mineralization zones, tectonic zones, karsts, etc. As compared with the contact options of the geoelectric prospecting, proximity methods allow us to obtain a continuous vertical profile of electrical resistances consistent with the geological data.
The main advantages over contact geoelectric prospecting are that measurements can virtually be performed on any surface, for example, rock glaciers, boggy areas, sands, water bodies, snow, ice, etc., and almost at any season and any weather conditions.
HPGP (HIGH-PRECISION PULSE GEOELECTRIC PROSPECTING)
The method of high-precision pulse geoelectric prospecting refers to non-contact methods that measure the response of electromagnetic fields when an artificial high-power electromagnetic pulse is induced (generated). This allows you to measure damping electrical amplitude and its phase. This method is a modified analogue of the NCEFM method. Measurements are carried out in the range Hertz to Megahertz, and then the data are complexed. The measuring lines represent symmetric isolated electric dipoles; however, the configuration of these measuring lines can be replaced by asymmetrical half-dipoles, as applicable.
The basic principles are non-contact measurements of electromagnetic fields, which is advantageous when working under severe conditions, where the use of contact grounding methods is impossible.
Type of field generation – pulse
Generator frequency range:
10 — 100ns; 100 — 1,000kHz; 100 — 1,000Hz.
Recorder frequency range:
2 — 10,000ns (500MHz — 0.1MHz)
2ns (500MHz); 2 — 1,000μs (500kHz — 1kHz);
2µs (500kHz); 2 — 1,000ms (500 — 1 Hz);
Generator power is up to 10MW per pulse.
The effective depth of exploration is 400 meters.
This hardware complex was developed by our Company’s Design Bureau with active participation and consulting with experts from IZMIRAN (Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences) and Schmidt Institute of Physics of the Earth, RAS.
NCEFM (NON-CONTACT ELECTRIC FIELD MEASUREMENTS)
The method of non-contact electric field measurement allows you to measure changes in the electromagnetic field in the form of a damped amplitude of electric signal by metal wire lines isolated from the ground under generator-induced electromagnetic field. The field technique for acquisition of data is different from similar resistance methods in a contact grounded design.
Different types of rocks and their different physical and mechanical states have also different electromagnetic characteristics. This provides variable electrical amplitude converted to electrical resistance (R). The NCEFM method is the electric sounding method that allows obtaining electric field data between two measured lines in the form of a vertical geoelectric profile. Based on this data, vertical geoelectric profiles can be simulated. This method is a non-contact analogue of VES.
The recorder frequency is 1 — 2,500Hz.
The generator frequency is 1 — 2,500 Hz.
The measuring lines represent symmetric isolated dipole.
Equipment type: The measuring complex «ERA-MAX».
NTES (NEAR-FIELD TRANSIENT ELECTROMAGNETIC SOUNDING)
Near-field transient electromagnetic sounding (NTES) is one of non-contact techniques for electromagnetic field measurement. In this case, electromagnetic field is sourced from an ungrounded generating loop, through which the current pulse is passing. After switching off the pulse generator, the damped amplitude response is measured. Electrical amplitudes are converted to electrical resistances and conductivities. According to damping curves of the apparent resistivity, a vertical conductivity profile is composed. Next, a geoelectric profile approximating to the geological data is simulated. In the international format, these methods are known and categorized as Time – Domain Electromagnetic Method (TDEM).
The measurement time is 0.1–100µs.
The square-pulse generator of 4-20µs.
The measurement pitch is 2µs.
Measurements are made inside a rectangular insulated loop.
Type of equipment: TEM FAST 48.
The method refers to non-contact electromagnetic measurement of the field excited by a pulse generator and allows you to measure changes in damped amplitude and phase of the signal after short pulse generation. Based on these data, a vertical geoelectric profile is composed and geological structures are simulated.
The frequency of data acquisition is from 2ns that provides detailed data on the textural features of the internal structure of rocks in the upper part of the geological profile.
The measurement frequency of the recorder is 2ns (500MHz).
The measurement time of the recorder is 2 to 2,000ns.
The generator frequency is 100 to 1,000MHz.
Equipment type: ground-penetrating radar LOZA, GROT.
Magnetic survey is a geophysical non-contact method of searching for mineral resources, metalliferous ores, tectonic zones, and associated “magnetic anomalies”.
The principle of measurement is based on the emission of electromagnetic field pulses and the field response recording by a receiver. Measurements are recorded as graphs of magnetic amplitudes (nT).
At the qualitative level, areal maps are drawn up in color palettes based on the results of the work, necessary “magnetic anomalies” are interpreted and selected manually or using processing programs. At the quantitative level, one can indirectly estimate the bodies geometry.
“Magnetic anomalies” represent deviations or “jumps” in the density of induced magnetic field produced by underground objects to the higher or lower side and differ from the total magnetic background in the given area. They usually form the so-called “magnetic dipole”.
The aero-magnetic data acquisition technique is performed from aircrafts at a height of the first hundred meters and is used for regional surveys of large squares at low span time.
The method of ground-based magnetic data acquisition is the most effective for rejecting aeromagnetic data, localizing and delineating ore objects and further setting of drilling works, but it takes a lot of time.
We apply a modern method of aerial survey using quadrotors at altitudes up to tens of meters, which has a higher information content and the execution rate compared with pedestrian and classical aerial survey. This technique allows you to receive data comparable with the pedestrian information value, while significantly reducing the span time.
Generally, for pedestrian measurements, proton magnetometers with sensitivity up to 0.01nT are used.
Among the great number of magnetometers at the market, MMP203 and MINIMAG models have proven themselves well.
Radiometric survey methods are based on identifying radiation halos around uranium-ore or rare-metal clusters, their primary and secondary halos in bedrock and loose sediments, as well as identifying halos of radioactive propagation in loose sediments and soils.
Gamma spectrometry is based on the registration of natural gamma radiation from uranium, thorium and potassium. The data is recorded by scintillator sensors, and the records represent the level (density) of gamma radiation, as well as the outlining of keV spectra.
The depth of gamma ray penetration in rocks and overlapping loose sediments does not exceed a single meter. However, due to the development of secondary scattering halos in them, the depth of radiometric methods is often much greater.
The essence of all varieties of gamma methods is reduced to the measurement of the total (integral) radioactive gamma radiation or to its differential registration in certain energy intervals of particles with the subsequent outlining of increased radioactivity areas.
For evaluation purposes, areal maps of isoconcentrations of uranium (radium), thorium, potassium, and the integral intensity of gamma fields are compiled. A comparative study of such maps helps to identify both the elevated concentrations of uranium (radium) origin and halos, zones and fields of metasomatic changes in host rocks, many rare-metal and uranium-ore fields being spatially associated with. Among unchanged rocks, such fields manifest themselves by anomalous ratios of radioactive elements, which are of low probability, both statistically and geochemically, for the background environment.
Pedestrian gamma-spectrometric surveys are carried out in the areas with relatively good rock exposure, in landscape conditions that contribute to the formation of open halos of uranium scattering. High-altitude and mountainous areas are most favorable for pedestrian surveys, where, along with good rock exposure, the mechanical halos of uranium scattering in the form of stone and block placers, as well as moderately dissected areas with good primary rock exposure and wide development of loose autochthon deposits are widely developed.
Gamma-spectrometric maps and data complement well the geochemical surveys and maps and make it possible to localize bodies and placers more accurately.
For ground-based gamma and ground-based gamma spectrometry surveys, instruments SRP 68 and MKS-AT6101D (made in Russia) are used.
All stages of geological, geophysical, engineering-geological and other works, starting with preparation till reporting, are provided with high-quality Mapping Support. A high level of digital map-making is maintained due to the use of modern tools, ACS (Automated Map Systems) and GIS (Geographic Information Systems).
The main tasks of map-making works are:
Digitization of archival materials and preparation of digital grounds based on the data obtained in the previous years of surveying.
The results of complex geological works carried out over 15-20 years ago, contain a significant amount of real and analytical information. These data are usually stored in hard copies. Proper transfer of the accumulated materials into the digital format allows us to use efficiently the accumulated knowledge for further updating, taking into account the information already available, which significantly reduces the costs and timing of the geological works.
Combining topical map information, materials of Remote Probing of the Earth (RPE), and field studies into the integrated system of coordinates and heights.
This allows us to use data obtained from various sources in a single set of spatial analysis and mathematical digital simulation. Due to the specifics of the primary data and technical features of obtaining information, the source materials are presented in various geographic projections, altitude systems and units of measure. Providing compatibility and accurate mathematical representation of the original components of spatial analysis and simulation ensures the required accuracy and relevance of the works performed.
Preparation of digital mapping bases for pre-field and field works.
Including for field navigation devices and specialized equipment. The field work is a significant part of the research complex required for project implementation. The Mapping Support at the field work planning stage allows the most effective “laying” of routes and patterns for special surveys. Directly in the field, digital mapping data provides accurate positioning and navigation, correlation of routes and reference points (pickets). In general, the preparation of digital mapping bases provides sufficient precision of works and optimization of material costs and span time.
Compilation of digital topographic bases resulting from topographic geodetic and mine surveys.
Digital topographic bases resulting from instrumental survey:
— provide high accuracy;
— ensure the information relevance;
— form the basis for creating and adjusting digital surface models for spatial analysis and simulation.
Preparation of topical digital maps resulting from specialized and research works.
Proper presentation of survey materials and simulation results in the form of topical layers or maps ensures the required precision and correct interpretation of the data obtained.
Preparation of reporting digital maps and printed layouts.
Reporting digital maps give the results of studies based on the work complex carried out within the project. Any digital map contains topical layers and attributes with precise geo-referencing, generalization of the scale corresponding to the project, the possibility of using for further studies for either production or commercial purposes, the ability to edit and customize the display of topical layers.
The digital map is the basis for creating printed layouts.
Laboratory analysis of samples during exploration provides geologists with on-line information for accurate simulation of ore formation processes, determination of the zoning and material composition of the ore areas sought. Implementation of a broad spectrum of lab analysis in an accredited laboratory warrants high-quality and precise data that increases confidence of the final results.
Basing on the purpose of the exploration performed, the Customers can select the required reporting standard and form. According to Customer’s Terms of Reference, the reports are presented in one of the following International Reporting Keys: JORC (Joint Ore Reserves Committee), CRIRSCO (Committee for Mineral Reserves International Reporting Standards), SAMREC (The South African Mineral Resource Committee), and so on, including GOST (Russia).