With the higher resolution scans from the SR-6500 spectroradiometer, it is easier
to see the subtle shift from hydrothermal illite to diagenetic illite.
Can illite be used as a pathfinder mineral in
uranium exploration?
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In unconformity-type uranium deposits like those in the
Athabascan basin, illite is often one of the clay minerals found
along with sudoitic chlorite, dravite, dickite, and kaolinite. Illite
can be considered a pathfinder mineral for uranium deposits.

Illite  types can be diagenetic (coarse grained and platy)  or
hydrothermal (hairy/wispy). There is a small increase in aluminum
(Al) content in hydrothermal illite relative to diagenetic illite. The
shift  to greater Al content can be more easily seen near 2200
nanometers using Spectral Evolution’s new ultra high resolution
SR-6500 portable spectroradometer.

Resolution at FWHM for the SR6500 is:
  • 1.5nm @ 700nm
  • 3.0nm @ 1500nm
  • 3.8nm @ 2100nm

Resolution is achieved using three high density solid state
thermoelectrically cooled photodiode arrays:
  • 1024 element TE-cooled silicon phtotodiode array detector
  • 512 element TE-cooled InGaAs photodiode array detector
    (SWIR 1)
  • 512 element TE-cooled extended InGaAs photodiode array
    detector (SWIR 2)

Illite typically has two absorption peaks at 1400 and 2200nm.. The
1400 feature is derived from the OH-overtone stretching
vibration while the 2200 feature is related to the Al-OH bending
combined with OH stretching. To see the shift in illite associated
with uranium deposits, the hydrothermal illite will have a small
but higher concentration of Al as opposed to the diagenetic illite
and will show absorption features at 2190 nm and 2200 nm as
opposed to the diagenetic illite which will show the absorption
feature at 2205, 2210, 2220 nm. By tracking the alteration changes
in illite a geologist might get a better idea of how close an ore
body might be.
 First in Full Range PDA Spectrometer, Spectroradiometer and Spectrophotometer Systems