Airborne Magnetic Surveys – Airborne Magnetic Surveys are used to Discover Minable Commodities Such as Iron and Petroleum.

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Airborne Magnetic SurveysIn the past several decades, airborne magnetic surveys have become a common means of acquiring data required for mineral and hydrocarbon exploration. The information uncovered during a magnetic survey is often the first phase of an exploration program to detect valuable minable magnetic ores such as kimberlites, chrome, and magnetic iron ores, as well as hyrdrocarbons, precious metals, uranium and water.
 
The exploration process usually commences with a regional airborne magnetic survey producing relatively low-resolution data, to be followed up with a detailed survey.  Detailed surveys tend to be smaller in scale, with closer line spacing producing higher resolution, more detailed data, and are typically flown with secondary geophysical technologies such as gravity and VLF-EM, which may lead to further mineral exploration such as exploratory drilling.
 
In an airborne magnetic survey, a magnetometer or series of magnetometers are attached to an aircraft and measure variations in the earth's magnetic fields from the air. Anomalies may indicate where minerals are present.
 
While mining companies uses airborne magnetic surveys in the prospecting stages of mineral exploration, others also rely on these methods as a means of uncovering concentrations of non-metallic commodities such as petroleum and coal.
 
Airborne magnetic surveys provide sufficient data for mapping lithologies and structure.
 
Types of airborne magnetometer setups include;
  1. Single sensor (typically a tail stinger, or heli boom, which generally gets the best data due to greater separation)
  2. Horizontal magnetic gradiometry (data acquired from two wingtip pod magnetometer sensors)
  3. Vertical gradiometer (two tail stinger mags mounted in a vertical orientation)
  4. Total magnetic intensity surveys (A combination of several magnetic sensors, typically three, but potentially four)
Airborne magnetic surveys work by identifying the frequencies and disturbances of the ambient magnetic fields existent as a result of the concentration of magnetic minerals present in the Earth's crust.
 
Typically magnetic minerals that can be detected using an airborne magnetic survey are:
  • Magnetite
  • Maghemite
  • Titanomagnetites
  • Titanomaghemites
  • Pyrrhotite
When it comes to economics of airborne magnetic surveys, carefully executed surveys are vital as the costs of executing remote airborne operations are high. Delays can be costly. The costs of airborne surveys are affected by inclement weather, permitting delays, and scheduled and unscheduled aircraft maintenance. Further, as airborne surveys are the first stage of the exploration process, they are highly speculative.
 
Important factors in the cost of an airborne survey are;
  1. Location of Survey – remote surveys typically increase costs substantially
  2. Fuel costs (highest in remote regions requiring airborne fuel lifts, and drummed fuel)
  3. The size of Survey (large surveys have a lower cost per km)
  4. Time of year, weather conditions
  5. Price variations in the type of data acquisition system used
  6. Delivery products (optional deliverables, map products etc.)
An experienced survey crew and a high quality geophysical aircraft and system are important factors in the success of an airborne magnetic survey. If the data acquired is questionable, it can lead to re-flights, complications during data processing and ultimately further exploration costs.
 
Look for the following characteristics when sourcing a data acquisition system:
  • Adaptive signal processing techniques
  • Immediate quality control
  • Flight planning
  • Navigation interface for a wide range of GPS instrumentation
  • No need for post flight corrections
  • Multi-channels of analog recording
In summary, when surveys are completed with an experienced crew and a high quality geophysical system, an airborne magnetic survey can result in highly useful data that is integral to the exploration program of a mining exploration company.
 
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