McPhar provides comprehensive survey solutions for mining exploration clients, whether corporate or government, and whatever the objective; finding minerals, precious or base metals, locating kimberlites or just mapping the natural resources of the land.   Our experienced professionals can help you to determine what type of survey you should conduct to provide the information needed to meet your objectives.

Geophysical surveys for mining are varied, and have the following applications:

Airborne Geophysical Surveying

Airborne geophysical surveying for mining exploration may be conducted using both fixed-wing airplanes or helicopters.   The choice of aircraft depends largely on project size, location, budget and application.   Fixed-wing and helicopter-borne geophysical systems are designed for use in different terrains, although helicopter-borne systems are undertaking high-resolution surveys in areas traditionally the domain of fixed-wing systems.

Our airborne geophysical survey techniques include:

Airborne geophysical surveys, whether installed on helicopters or fixed-wing aircraft, are the most effective and rapid means of evaluating the potential for mineral resources in both unexplored areas and mature mining regions.   The use of GPS satellite navigation and powerful microcomputers onboard the aircraft to control the systems and to record data; and on the ground to process, plot, interpret and model the data; has made airborne geophysical surveying a powerful and necessary tool in man's search for materials beneath the ground.

Fixed-Wing Surveys

A fixed-wing airplane has a number of advantages in addition to its lower operating costs.   First, it has a payload and cabin space larger than a helicopter and thus can carry more instrumentation.   Second, its operating range is generally three or four times greater than that of a helicopter.    Surveys can be flown farther from population centres, thereby reducing some of the logistical problems of a helicopter-borne survey.  

The fixed-wing systems we can provide for mining applications include:

The twin- engined airplanes may also be equipped with a multi-sensor gammaray spectrometer system.

Instrumentation

A typical fixed-wing survey aircraft is equipped with a variety of sensors and other ancillary instruments.   For example, an aircraft equipped for a high-sensitivity magnetometer and gammaray spectrometer survey would be equipped as follows:

Airborne High Sensitivity Magnetometer

A high-sensitivity, optically-pumped, Scintrex CS-2 or Geometrics G822A airborne cesium magnetometer, with a sensitivity of 0.0006 nT is utilised.   This high-sensitivity magnetome­ter will be deployed either in a tail stinger on the fixed-wing aircraft, or in a towed-bird airfoil for the helicopter, and will perform continuously in areas of high magnetic gradient with the ambient range of the sensor approximately 20,000-100,000 nT.   Aerodynamic magnetometer noise will not exceed 0.10 nT for either system.    Magnetic compensation of the acquired “raw” magnetometer data is undertaken as a post-flight correction on the ground using proprietary software ( CCMAG ) at the survey base.  

Gammaray Spectrometer System

A Pico Envirotec GRS-410 multi-channel gamma-ray spectrometer with 33.6 litres "downward looking" NaI sensor and 8.4 litres "upward looking" NaI sensor will be utilised, and will sample data once per second. The thermally isolated sensors are installed in the cabin of the aircraft.  

The GRS-410 is a self-stabilizing spectrometer, and tracks and corrects for the spectral drift by following a spectral peak, typically thorium.   T he standard regions of interest are recorded and processed.

All McPhar’s gammaray spectrometer surveys are conducted following the recommendations of the International Atomic Energy Agency, as published in their guidelines - IAEA-TECDOC-1363 / Guidelines for radioelement mapping using gamma ray spectrometry data.  

The Navigation System

Two GPS navigation receivers are used onboard the aircraft.   One is an OMNISTAR real-time differentially corrected GPS receiver, used to provide a visual indication of the flight path to the pilot during flight.   The second GPS receiver is a geodetic quality dual-frequency GPS receiver recording the full GPS suite of data to be used to obtain post-survey differentially corrected positions for the acquired survey data.   Another geodetic quality dual-frequency GPS receiver is set up as a base station with a PC-based datalogger at the base of operations.

The real-time OMNISTAR DGPS receiver on the aircraft is a CSI-Wireless DGPS-MAX system.   The dual-frequency GPS receiver is a NovAtel MiLLennium GPS receiver.   A 3D pilot steering indicator and Navigation Computer provides steering and vertical and horizontal track guidance to the pilot.

The Geo-iMAGe-Lite Digital Imaging System

The primary focus of this digital imaging system is to replace the traditional 8mm “VCR” with a digital picture recording mechanism.    Any standard CD-ROM may be used to view the frame or frames of choice on a computer, using any variety of commercial imagery software.   Alternatively, imagery processing may be undertaken using software such as ER-MAPPER.

To record digital imagery of the ground over which the aircraft flies, McPhar uses a Dev-Tech Geo-iMAGe Colour Digital Imaging System.

Radar Altimeter

A TRA-3000 (or equivalent model) radar altimeter system is used to record the ground clearance to an accuracy of less than 1 meter (about 3 ft), over a range of 40 ft to 2,500 ft (12m to 770m).   This altimeter is installed on the aircraft and is interfaced to the data acquisition system with an update rate of 0.1 second, and is digitally recorded together with all other geophysical and navigation data.  

The Data Acquisition System

Survey data is digitally recorded on a Pico-Envirotec AGIS Airborne Geophysical Information System.   The AGIS is not only a powerful data acquisition system; it is also a fully PC-compatible microcomputer, built around a PENTIUM CPU board. All data collection routines, checking, buffering, recording and verification are software controlled for maximum flexibility. A modular concept has been used for both the software and the hardware to allow for future expandability.   The five main functions fulfilled by the DAS are: 1) system control and monitoring, 2) data acquisition, 3) real-time data processing, 4) navigation, and 5) data playback and analysis. The AGIS is controlled and operated by a standard keyboard   and is supplied with a number of expansion slots, into which may be installed various processor modules.

Base Station Magnetometer

A Pico Envirotec GMAG magnetometer base station and cesium magnetometer sensor is utilized as a base station, with digital recording, and is operated continuously throughout the survey operations. This base station is synchronized with the airborne system by GPS time.   The resolution of this magnetometer is 0.01 nT.   During survey operations, the magnetometer is usually sampled at a rate of once every second.

The magnetometer sensor is either a Scintrex H8 or CS-2 model, installed in a dust-proof/water-proof housing.

Every effort will be made to ensure that the magnetometer sensor is placed in a location with a low magnetic gradient.   In addition, it is sited away from moving ferrous objects, such as vehicles, and electric power transmission lines, such that these sources of man-made noise will not exceed 0.5 nT.

Pico Envirotec GMAG Cesium magnetometer base station – sensor is housed in a dust-proof / water-proof housing

Field Data Verification Workstations

Field Data Processing Workstations (FWS) are dedicated PC-based microcomputer systems for use at the technical base in the field. The workstation are designed for use with a variety of QC and data processing programs, including Geosoft’s MONTAJ Data Processing Software.    The FWS has a data replot capability, and may be used to produce pseudo-analog charts from the recorded digital data within less than 12 hours after the completion of a survey flight, if this is necessary.   It is also capable of processing and plotting all of the geophysical and navigation data acquired during the survey, producing semi-final, preliminary-leveled maps in either black-line contours or full colour contours on paper.   

Fixed-wing Aircraft

McPhar utilizes a variety of fixed-wing survey aircraft, including the Cessna C208B Grand Caravan, the Beech C90 King Air, Piper PA-31 Navajo and Cessna C206 Station Air aircraft.

Cessna C208B Grand Caravan survey aircraft

Beech C90 King Air Survey Aircraft featuring an extended tail-boom for a cesium vapour magnetometer

Piper PA-31 Navajo Survey Aircraft featuring horizontal magnetic gradiometers measuring the horizontal transverse and longitudinal gradients.   An optional tail-boom assembly for this aircraft will permit 3-Axis gradiometry.

Cessna 206 Survey Aircraft featuring a horizontal magnetic gradiometer with a cesium vapour magnetometer installed on each wingtip

Drape Flying

To obtain high resolution geophysical data, fixed-wing survey airplanes should be flown at a consistent height above the ground, maintaining a consistent and safe altitude (the drape surface) on the two orthogonal survey line directions.   When and where appropriate, we operate a computer-assisted system, 3DNAV, to enable our flight crews to maintain an optimal flight altitude (drape surface) during surveying while at the same time ensuring that primary and control lines intersect at the same altitude. The result can be a considerable improvement in the quality of the high resolution data acquired, particularly in hilly or mountainous terrain.

Helicopter-borne Surveys

Undoubtedly, helicopter-borne electromagnetics (EM), combined with total field magnetics and gamma-ray spectrometry, have been the most productive and useful of these airborne system developments to date, and have accounted for the discovery of billions of dollars worth of mineral resources, tapped into numerous ground water reservoirs and provided immense volumes of data for environmental site evaluations.   These systems are ideally suited for working in rugged, mountainous terrain, or over small claim block-sized properties, and are the techniques of choice for most mining companies to locate base metal and precious metal deposits and/or kimberlites.

Helicopter systems we can provide for mining applications include:

Bell 206 L3 Jet Ranger helicopter featuring HeliMAG 1- a towed-bird high-sensitivity magnetometer system

Eurocopter AS315 LAMA helicopter featuring HeliMAG 2 - a rigid-boom high-sensitivity magnetometer system

Robinson R44 helicopter featuring HeliGRAD - a rigid-boom horizontal magnetic gradiometer system with a cesium vapour magnetometer installed at each end of the boom

Eurocopter AS350BA A-Star helicopter featuring HUMMINGBIRD – a multi-sensor system with a 5-frequency digital EM and high-sensitivity magnetometer system

Eurocopter AS350BA A-Star helicopter featuring THEM – a multi-sensor system with a Time-domain EM sensor and a high-sensitivity magnetometer

HeliMAG /Radiometrics system installed on a Bell 206B3 Jet Ranger helicopter

Quality Control

McPhar ensures Quality Control by using a team concept.   The instrumentation onboard the survey aircraft permits basic quality control procedures.   The team concept is continued at the Survey Base where a McPhar Geophysicist undertakes a more comprehensive QC analysis of the data, and performs preliminary data processing.   The data is then given a second, and more complete review, wherein all the systems onboard the aircraft are tested for compliance to the survey’s specifications.   Any problematic or unacceptable data is identified and flagged for reflying by the survey crew.   On a daily basis, this preliminary processed data is sent to McPhar’s data processing centre, where other geophysicists commence the Final Data Processing work.

McPhar almost always undertakes Quality Control and preliminary data processing in the field.   For this purpose all our airborne systems are mobilized with a geophysicist and a PC-based data processing system to support them.   The Field Data Verification Workstation (FWS), as this system is known, can process airborne geophysical data of all kinds, and produce plots and maps in full-colour of the survey data, often within hours of the survey flight ending.   The FWS software, which is the core of this system, permits the Q.C. geophysicist to differentially correct the GPS navigation data; carry out flight path recovery; perform magnetic compensation and leveling; undertake radiometric corrections and preliminary processing; EM leveling and processing; and generally to perform filtering, gridding and contouring of data, imaging of selected data and plotting to any map scale and layout.

In-field QC of airborne data in a forward field camp and in the friendlier environment of a field office

Data Processing

After the infield QC of the data has been completed, the data are then sent to McPhar’s data processing center in Markham , Canada where the final processing mapping are completed.   Colour contour maps, sometimes black-line contour maps, and offset and stacked profiles are then produced.   A survey report is provided.   A full range of products is routinely derived from the data.   Our data processing center features a network of powerful PENTIUM microcomputers and state-of-the-art software for data reduction and compilation.   Image and map products are produced on HP colour plotters.

McPhar’s data processing center in Markham, Ontario, Canada

Total Magnetic Intensity, IGRF removed and the First Vertical Derivative colour contour maps of a survey area recently flown in Alaska

Interpretation & Modeling

The interpretation/modeling of geophysical results into meaningful geological parameters is the prime function of any interpreter.   The manipulation of geophysical data is only a means to an end, and the final product of the interpretation is the compilation of a series of maps showing interpreted geological parameters.   The data processing routines and mathematical operators applied to the data by McPhar are not the end product of the interpretation; they help delineate geologic and economic targets to be discussed in the final report.   Many techniques are available to apply to an interpretation project; to determine depths to causative sources, to delineate discontinuities and boundaries, and to draw conclusions regarding geological structure beneath the survey.   A wide variety of contour and interpretation maps, profiles, cross-sections and models, and a written report are usually the result of the interpretation.

Ground Geophysical Surveying

A variety of ground geophysical survey methods are available and include:

• Land Gravity & GPS
• Induced Polarization & Resistivity
• Electromagnetics
• Magnetics and Gradiometry

Land Gravity & GPS survey underway, using a Scintrex CG-3 AUTOGRAV gravity meter and a geodetic quality GPS receiver

Induced Polarization survey underway, using a Scintrex IPR-12 IP receiver

Vertical magnetic gradiometer survey underway, using two Scintrex “SMARTMAG” high-sensitivity cesium magnetometers