Ground geophysics
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Geofisica TMC S.A. de C.V. is proud to offer to its clients a whole range of geophysics technique and related services to assist them in all their exploration works. Used for mining exploration, geophysics makes it possible to discover base metals, gold, diamonds and conductive geological units. Associated with mine development, it also makes it possible to define boundaries and size of conductive ore bodies. Finally, geophysics is also a good mean to reduce drilling by exploring between holes at the time of the mine production.
You will find below, further information about all of our services offered.
GEOPHYSICAL SURVEYS
Magnetic
IP
Electromagnetic
SQUID Sensor
RELATED SERVICES
Line cutting and picketing
Soil sampling
Reports and interpretation
Magnetometer
A magnetometer is used to measure the intensity of the earth's magnetic field. Deviations of magnetic intensity are caused by changes in concentrations of natural ferrous minerals (e.g. magnetite) or by the presence of ferrous metals.
Magnetic measurements can be used for geological mapping to provide an estimate of the thickness of non-magnetic sediments overlying magnetic rock and location of structure and faults within magnetic rock. Magnetic measurements are commonly used for locating and mapping buried ferrous metals (i.e. metal wastes, drums or underground tanks and utilities).
Map geological structure and stratigraphy
Identify natural and man-made ferrous objects
Map karst features within magnetic soils and rock
Advantages
Measurements are relatively easy to make
Does not require intrusive ground contact
Carried by hand or vehicle-mounted
Also in continuous mode and/or assisted by integrated GPS
Advantageous in open rugged terrain areas
Very economic since no line cutting is required
Data Presentation
After data processing, the magnetic results are presented as a contour color map showing the magnetic deviation intensity; from the lowest readings (blue) to the highest (pink)
The measurements can also be presented as a profile map including the readings at their location point
When the measurements are taken with a gradiometer system, those results are also presented as a color contour map
Electrical Resistivity Survey (IP)
Electrical Resistivity measurements are made by placing several electrodes in contact with the soil or rock. A current is caused to flow in the earth between one pair of electrodes while the voltage across the other pair of electrodes is measured. The depth of measurements is related to the electrode spacing. The resistivity measurement represents the apparent resistivity averaged over a volume of earth determined by the soil, rock, and pore fluid resistivity, along with the electrode geometry and spacing. The method is called Induced Polarization (IP).
Detect non-conductive disseminated but polarizable mineralization (porphyry copper) as well as massive mineralization (massive sulphides)
Determine the depth and thickness of geologic strata
Detect lateral changes and locate anomalous geologic conditions
Azimuthal measurements to determine fracture orientation
Advantages
Depth range of up to 100 meters
Various electrode configurations are available for different applications
Data Presentation
IP measurements are presented as contour coloring of the resistivity and chargeability. The factor metal is also presented on the pseudo sections. A pseudo section is a small plan of the measurements for a specific line
A color contour map of the resistivity for the entire grid. Same presentation is done for the chargeability
If asked, all the pseudo can be shown on a single map given a good view of the progression of the anomalies line by line
Electromagnetic (EM) measurements are primarily used to detect and map lateral changes in natural geologic and hydrogeologic conditions. The method is also applicable to detecting and mapping contaminant plumes and can be used for locating and mapping buried wastes, metal drums and tanks, and metal utilities. There are two general types of EM measurements: Frequency Domain and Time Domain.
Frequency Domain (HLEM)
Frequency domain electromagnetics measures the magnitude and phase of induced electromagnetic currents, which are related to the subsurface electrical conductivity. Electrical conductivity is a function of the soil and rock matrix, percentage of saturation, and the conductivity of the pore fluids. EM instruments provide two measurements simultaneously, the electrical conductivity data and the in-phase component, which responds to magnetic susceptibility and metal. This survey is done using the horizontal loop EM (Apex Maxmin I).
Detect conductive semi-massive to massive sulphide bodies(VHS)
Inexpensive tool for ground follow-up of airborne survey
Frequency domain electromagnetic measurements are primarily used for profiling to detect and map lateral changes in natural geologic and hydrogeologic conditions
Electromagnetic measurements are also applicable to detecting and mapping contaminant plumes
Advantages
Measurements are relatively easy to make
Data do not require extensive processing and corrections
Does not require ground contact
Electromagnetic measurements provide excellent lateral resolution
Continuous data may be acquired with hand-carried equipment
Provides measurements with depths ranging from a few meters to 100 meters
Data Presentation
The measurements are presented as profiles of the In-phase and Quadrature along the survey line for each frequency surveyed
Time Domain (TDEM)
Time domain electromagnetics (TDEM) measures the bulk electrical resistivity of subsurface conditions by inducing pulsed currents in the ground with a large transmitter coil. The decay of the induced currents over time results in a decaying secondary magnetic field at a rate that is governed by the electrical resistivity of the earth. The decay of the secondary magnetic field is then monitored at increments in time with a separate receiver coil.
Geofisica TMC S.A. de C.V. use the PEM System from CRONE GEOPHYSICS & EXPLORATION LTD This method is powerful for surface and borehole mineral exploration.
Applications
Defining location, boundaries and size of conductive ore
Reducing drilling by exploring between holes
Surveying underground drill holes, even flat or inclined ones
Measuring the magnetic field along the drill holes with the RAD tool
Differential and clay weathering, conductive weathered layer at surface
Graphite rich rocks, including graphitic schist, shale, slate and argillite
Advantages
Depth range of approximately 10 to 3,000 meters
Requires less space than resistivity measurements to reach the same depth
Detect and locate with precision an off-hole conductor within a radius of 100 to 150 meters
Determine the extension of an in-hole conductor for subsequent drilling
Can read the magnetic field (MAG) along the hole
Data Presentation
Surface
Logarithmic profiles of channels measured presented along the survey line. This map shows all lines read using the same transmit loop for a specific component. The position of the loop is also on the map
Logarithmic profiles of the channels measured on a US letter paper size. One line per plan for a specific component
Linear profiles of the channels measured on a US letter paper size. One line per plan for a specific component
Borehole
Logarithmic profiles of the channels measured shown vertically in the way that represent the drill hole. One diagram for each component
Logarithmic profiles of the channels measured on a US letter paper size. One plan for each component measured
Linear profiles of the channels measured on a US letter paper size. One plan for each component measured
Rad tool
Presentation of the drill hole lithology and the information measured using the RAD tool
SQUID = Super-conducting QUantum Interference Device.
The B field can be accurately measured in surface time-domain EM surveys.
The CSIRO HT-SQUID Magnetic sensor can be use as a direct replacement of the coil sensor in the CRONE Pulse EM System.
The combination of SQUID sensors and the moving in-loop survey method have been shown to be an excellent method for the detection of deeply buried, highly conductive massive sulphides, such as nickel, while being able to effectively maximize the response from conductive cover and formational conductors.
The example below shows comparison of COIL and SQUID responses over the Tripod Lens, Zone 5-8at Falconbridges Raglan in far north Quιbec.
Line cutting are always a grid measured with GPS which is picketed every 25 or 50 meters. In regard of our social responsibility, our crew leaders will hire local members of the closest community from the project to cut and mark the lines necessary according to the geophysics surveys requirements. Crew leaders will quickly train then manage the line cutting team which can have up to 30 men per single contract.
Obtaining representative soil samples are the key to a successful soil testing program. A clear statement of the study's objectives for data quantity, quality, reliability and speed will be made before heading out on the field so clients will get the optimum production and most importantly maximum return from the laboratory results.
Every geophysical survey can be followed by a detailed report made by one of our affiliated senior geophysicists who have more then 30 years of experience. A complete report can bring a considerable help for future exploration and/or exploitation on the project.