Exploring For Diamonds in North America
One of the most common forms of exploring is till and stream sampling.  This process involves looking for indicator minerals that are associated with diamonds.  Like diamonds, they also weather very slow and are heavy.  Another reason companies look for indicator minerals is because there are more of these minerals than diamonds, making diamonds easier to locate.  According to the Natural Museum of History, "some of the more important indicator minerals associated with diamonds are: garnet, chromite, ilmenite, clinopyroxene, olivine, and zircon."  Below is a map showing indicator minerals, diamond bearing kimberlite and kimberlite occurrences. (Diamonds- American Museum of History)
 
 


This is a map of a Ground Geophysical Survey.  Image taken from New Blue Ribbon Resources Inc.

Conducting a Ground Geophysical Survey is another method for testing for indicator minerals.  The primary type though is using a seismic method.  These are methods that send a material wave into the ground and listen for the response from the subsurface.  When the wave comes back is interpreted to represent what is below the surface.  The most basic form of this is reflection seismology with an impulsive source. (Anthony Hoch)

There are two other types of exploring that are done using an airplane.  They are airborne magnetic and electromagnetic surveys.  Almost every type of rock on the earth has a magnetic signature.  Most of this is due to the condition of the earths poles at the time the rock cooled.  When a body of rock cools it basically becomes a big magnet with the same orientation the earth had at that time.  Flying a magnetic meter over the earth will show how the fields change when flying over the area being surveyed..  This helps detect when rocks cooled, giving them certain geophysical properties.  The picture below with the circle shows a different magnetic signature than the surround area.  Inside the circle is a circular pattern which could be kimberlite pipe. (Anthony Hoch)


Image taken from New Blue Ribbon Resources Inc.

Airborne Electromagnetic is the use of non material sources (electromagnetic radiation, microwaves) which are used to detect differences in conductivity of material.  The source influences objects in the ground to produce a signal, which will be similar to the original.  After turning the source off, listen for the signal that is produced. After recording the signals, plot them on a map, which looks like the one above.  There is a similarity between maps in the same general location.  (Anthony Hoch)


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