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MORE THAN 40 YEARS OF EXPERIENCE IN AIRBORNE GEOPHYSICAL SURVEYS

WITHIN RUSSIA AND WORLWIDE

Airborne low frequency domain electromagnetic system

This system is dedicated to geological mapping and evaluation of project territories ore mineral prospect.

System features

The core of the system is frequency domain EM system EM-4H, airborne modification of dipole inductive profiling. Transmitting loop is mounted on aircraft (airplane or helicopter or towed below a helicopter), and installed in tow-bird receiver is towed under aircraft.

The obtained data processing includes conversion of output signals in effective resistance (conductivity), corrected for aircraft altitude and relative shift between transmitter and receiver.

The required component of EM-4H system is a high-accuracy airborne magnetometer, with the sensor installation in the tow-bird with EM receiver.

The GPS Navstar-Glonass satellite constellation is used for aircraft positioning.

Depending on the project task and geological-geophysical situation, the EM survey can be integrated with a gamma-ray spectrometry.

Helicopter MI-8 fitted with EM-4H system

Helicopter MI-8 fitted with EM-4H system

Geological tasks performed by EM-4H system:

  • Mapping of disjunctive zones of different ranges, permeable fracture and shatter zone, appeared as linear conductive zones
  • Research to internal structure of areal destructive zones
  • Tracing of ore controlling and ore localization agents within known ore fields
  • Extraction of perspective for ore bodies local conductive anomalies
  • Mapping of buried paleo-valleys for placers exploration
  • Detection of coal-bearing layers
  • Detection of buried weathering crusts and associated commercial mineral deposits
  • Mapping of geological targets with contrast electrical features
  • Mapping of permafrost boundary

Some survey samples:

Airborne low frequency domain electromagnetic surveying system

This system provides solutions to the task of geological mapping of a given area and assessment of the territory for the presence of various solid minerals.

System features

The core of the complex is a frequency domain EM system EM-4H, using a modified version of inductive dipole profiling. The obtained data processing includes conversion of output signals into effective resistance (conductivity), corrected for aircraft altitude and for relative shift between transmitter and receiver.

The required component of this system is a high-accuracy airborne magnetometer, with its sensor installed in the tow-bird with the EM sensor.

The GPS Navstar-Glonass satellite constellation is used for aircraft positioning.

Depending on the project task and geological-geophysical situation the EM system can be integrated with a gamma-ray spectrometer.

Geological tasks performed by this electromagnetic surveying system:

  1. Mapping of disjunctive zones of different ranges, permeable fracture and shatter zones, expressed as linear conductive zones.
  2. Research to internal structure of areal destructive zones.
  3. Tracing of ore controlling and ore localization signature within known ore fields.
  4. Identification of local conductive anomalies, perspective for ore bodies.
  5. Identification and mapping of buried paleo-valleys for placers exploration.
  6. Detection of coal-bearing layers.
  7. Detection of buried weathering crusts and associated commercial mineral deposits.
  8. Mapping of geological targets with contrasting electrical features.
  9. Mapping of permafrost boundary.

Some survey samples:

 

Effective conductivity and anomalous magnetic field maps. Kureyka river. Scale 1:25000

Effective conductivity and anomalous magnetic field maps.
Kureyka river. Scale 1:25000.

Geological map and combined local magnetic anomalies/ conductivity map. With red marked the perspective areas

Geological map and combined local magnetic anomalies/
conductivity map. With red marked the
perspective areas.

Results of integrated airborne geophysics. Maps of effective resistance, K-concentration, anomalous magnetic field. Polar Ural, scale 1:10000

Results of integrated airborne geophysics. Maps of effective
resistance, K-concentration, anomalous magnetic field.
Polar Ural, scale 1:10000

Geological map created by obtained in 90th data, and its renewed version by survey interpretation

Geological map created by obtained in 90th data, and its renewed version
by survey interpretation

After specialized data processing and geological-geophysical interpretation the geological map of project territory has been essentially defined. Beside that, has been created the predictive scheme for iron, cuprum, platinum minerals.

Predictive scheme for Fe, Cu, platinum minerals

Predictive scheme for Fe, Cu,
platinum minerals

Effective resistance cross-sections

Effective resistance cross-sections

High-accurate in-phase and quadrature measurements of vertical component of secondary EM fi eld allow to plot the geo-electrical cross-sections.

 

Сопоставление геоэлектрических разрезов с геологическими
Сопоставление геоэлектрических разрезов с геологическими


Comparison of geo-electrical and geological cross-sections.

Technical features

EM system ( Geotechnologies, Russia)

Technical specifications:

  • Work frequencies (sine signal) – 130, 520, 2080, 8320 Hц;
  • Loop square – 60 m2 (helicopter MI-8 configuration);
  • Loop installation - around aircraft or towed below helicopter;
  • Measure of 3 EM components;
  • Receiver installation – towed bird;
  • Tow-cable length – 70 m.

Airborne magnetometer (Aerogeophysica Inc., Russia)

Technical specifications:

  • Resolution – 0.001 nT;
  • Measurements rate – 20 Hz – 1000 Hz;
  • Tolerance – up to 20000 nT/m;
  • Measurements range – 17000 nT - 100000 nT.
  • Sensor – CS-3, Canada, installed in towed-bird.

Airborne gamma-ray spectrometer (Radiation Solutions, Canada)

Technical specifications:

  • Number of channels – 512 or 1024, optionally;
  • Detectors – NaI (Tl) crystal detectors with total volume of up to 48 L; energetic resolution on line
    0.662 MeV (Cs-137) better 10%;
  • Measurement range 0.38 – 5.0 MeV;
  • Measurement rate – 1 sec;
  • Automatic stabilization on Th line.

Data acquisition software and positioning:

This software collects and synchronizes data from EM, magnetometer, spectrometer (if employed), and navigation channels. As well, it provides flight steering and survey line approach with installed on cockpit panel pilot indicator. Using GPS data the system provides the positioning accuracy meeting the requirements for geophysical survey up to line spacing 50 m.

Ground equipment

For diurnal variations control and navigation task the base magnetometer and GPS stations are used.

 
Airborne low frequency domain electromagnetic system Wednesday, 20 September 2017