Summary
This
study shows that ternary composite imaging from airborne gamma-ray spectrometry
survey data can be used to prepare lithology maps with very little geological
information.
Introduction
Airborne
Gamma-Ray Spectrometry (AGRS) exploration measures the equivalent Uranium (eU),
equivalent Thorium (eTh) and Potassium (K) content of the near surface. These
are very common radioelements found in varying amounts in different type of
rocks.
It
has been shown that the composite images of the three AGRS radioelements are
comparable to geological lithology maps in several geographical districts.
Theory/Method
In this study we researched
and developed an approach to accelerate geological mapping in Greenfield Areas
of Northern Canada using airborne AGRS. This approach consists of the
combination of the following techniques:
1) an automatic technique without any priory information, and,
2) a hierarchical classification technique with priory information.
The first technique combines
the three radioelements (eU, eTh, and K) in a statistical manner and defines
the relative abundances of those radioelements at each data location. The
results of this technique are illustrated
using composite ternary imaging procedures. We were able to distinguish felsic
Quartz Feldspar Porphyry (QFP) areas from mafic areas.
The second technique’s goal
was to complement the visual interpretation of ternary maps with more
quantitative measurements. We developed a quantitative method to establish the
relationship between the rock samples and their radioactivity content acquired
from the airborne system. Modeling was used to quantify the radiometry
signatures and rock samples were used to classify the radiometry data.
Conclusion
This approach allowed us to
extract a maximum of relevant information from the AGRS data and extend the
primary geology maps beyond areas where the geology is not known.
Acknowledgements
TerraNotes
and I would like to acknowledge the research and development contribution for
this study from the following agencies:
- National
Research Council Canada
(IRAP)
- Alberta
Ingenuity Fund (now Alberta
Innovates Technology Futures)
And finally, we would like to thank to GeoScience 2010
for accepting our abstract and giving us the opportunity to share our study’s
findings with you.
