Airborne GeophysicsMagnetics

Airborne magnetic surveys map the variation of the Earth's magnetic field strength caused by magnetic minerals in the Earth's upper crust.

The Earth's magnetic field is directly influenced by geological structures, geological composition and magnetic minerals, most often due to changes in the percentage of magnetite in the rock. Developments in instrumentation and data processing techniques can map sedimentary basin structure and lithology, geological faults, lineaments and fracture systems, and magnetic anomaly targets.

Airborne magnetic surveys are an important component in mineral, hydrocarbon, coal and geothermal exploration projects.

GPX Surveys has a variety of fixed wing and helicopter platforms available to suit any job, regardless of location or size. Surveys are conducted to gather the best possible data for the client whilst employing the safest and most practical methods of data gathering.

Our state of the art systems enable us to resolve magnetic field changes to a resolution of 0.2pT.

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APPLICATIONS

Minerals
Magnetic measurements are an integral part of most mining related airborne geophysical surveys. They provide a valuable addition to other data sets such as electromagnetic and radiometric data. As a standalone tool magnetic data has moved far beyond target hunting and can now be used for detailed mapping of geological structures and lithology. Survey parameters such as line spacing and survey height can be tailored to meet client requirements. Please click here for information about our uranium exploration techniques.

Oil & Gas
Improved resolution in magnetometers, sensors and aircraft positioning has resulted in more use being made of airborne magnetic surveys for hydrocarbon exploration. High Resolution Aeromagnetic data is now being used for the detection and detailed mapping of faults and fracture systems throughout the sedimentary section. This is in addition to the traditional task of mapping basement structure and lithology. Please click here for a flyer.

Coal
Modern aeromagnetics are increasingly being used in the exploration, feasibility and development stages of the coal mining sector to provide detailed structural (fault) mapping and identification of intrusive volcanic plugs and sills. Accurate mapping of these geological features is extremely important in the initial estimation of calculated reserves and the development and planning of mining methods and associated costs. Please click here for a flyer.

Geothermal Energy
The use of aeromagnetic data in the geothermal energy exploration sector is important to create a detailed structural interpretation which assists with accurate placement of geothermal injection and recovery wells.

Geological Survey Mapping
For many years various government geological mapping agencies and international aid agencies (eg World Bank) have funded country scale geological / geophysical mapping programs to provide useful and affordable databases designed to encourage exploration investment. These programs have utilised both detailed and regional aeromagnetics as the primary database to encourage this investment.

Geotechnical Engineering
Airborne magnetic data has the ability to accurately map geological structures and lithology. Geotechnical engineering applications include assessing geological stability, earthquake fault zone identification and delineating groundwater control structures.

TECHNIQUE

Typically a single magnetometer sensor is mounted on a fixed wing aircraft or helicopter. As the aircraft flies through the air it measures the magnetic field, attitude of the aircraft, GPS position and altimeter data. An onboard computer records the raw data and corrects the magnetic data for aircraft attitude variations.

The final data is tie line levelled and/or micro-levelled and includes corrections for diurnal fluctuations, IGRF and system parallax.

EQUIPMENT SPECIFICATIONS

Pico Envirotec AGIS - Airborne Geophysical Information System
The Airborne Geophysical Information System (AGIS) is an advanced, software driven instrument specifically designed for airborne or ground geophysical survey work. The

AGIS is a fully integrated survey system incorporating the state of the art MMS4
Magnetometer Processor and is automatically synchronised to GPS time.

Pico Envirotec MMS4 - Multiple Magnetometer Sensor Processor
The MMS4 is a high resolution (0.2pT), fast sampling (20Hz) magnetometer processor unit that continuously measures the magnetic signals from up to four magnetometer sensors. It has the option to provide real time magnetic compensation of the airframe motion.

This magnetometer was designed to work with the AGIS acquisition system or a computer communicating on a serial protocol RS232. It contains synchronisation input for the GPS pulse per second (pps) to assure precise signal sampling without quantising errors.

Specifications
Input:	Coaxial - Larmour signal over DC Power Supply
Resolution:	0.0002nT(Gamma) = 0.2 picoTesla
Sampling Rates:	5, 10, 20, 25,50, 100 Hz
Dynamic Range:	15,000 to 100,000nT
Synchronization:	GPS - PPS (Pulse Per Second)

Geometrics G-822A Magnetometer sensor
The Geometrics G-822A magnetometer sensor is an optically pumped cesium-vapour atomic magnetic resonance system.

Specifications
Operating Range:	20,000 - 100,000 nT
Sensitivity:	Typically 0.002 Nt P-P at 20Hz sample rate
Heading Error:	< 0.15 nT over entire 360°
Output:	Larmour frequency, 3.498572 Hz/nT