1. Radiation Damage of Quartz Grains Contained in
the Host Sandstones of the Three Crow Roll-Front
Uranium Deposit, Nebraska
Julie Leibold
Thomas Monecke, Dan Jiricka, and Adrienne Hanly

2. Location of Three Crow Deposit
Three Crow Deposit:
 Average Grade of 0.22 wt.%
U3O8
 Indicated resource of 3.75
million pounds U3O8
 Expected yearly production:
6 mi/10 km 600,000 pounds U3O8

3. Methodology
• Hot-cathode Cathodoluminescence (CL)
microscopy
• Scanning Electron Microscopy (SEM) and
Electron microprobe studies
• Raman Spectroscopy

4. Three Crow Uranium Deposit
Modified from A. Hanly (unpubl., 2009)

5. Cathodoluminescence
Halos in Quartz
www.und.nodak.edu, Petrology 320
0.25 mm
 Pleochroic halos in biotite are
well recognized
 Unlike biotite, radiation
induced features in quartz are
not visible in plane polarized
or cross-polarized light
0.25 mm

6. Cathodoluminescence
Halos in Quartz
250 um
Owen (1988)
 Alpha particles result from the
 Source of alpha particles and
decay of radionuclides such as
their resulting kinetic energy
uranium and thorium
determines maximum halo radius
 Irradiation with alpha particles
 Alpha particle dosage and time
causes the CL of quartz to shift
determine intensity of the halo
from blue or brown to orange

7. Cause of CL Halos in Quartz  Cathodoluminescence can
result from element
substitution or structural
defects
 Major element concentration
does not vary between the
halos and the pristine quartz
Al map

8. Cause of CL Halos in Quartz  Raman spectroscopy reveals
structural information
Unaltered  Amorphization is indicated by
quartz an increase in the peak width
and background and a
decrease in relative peak
height of the 466 cm-1 peak
Blue CL Halo CL Difference
Quartz FWHM of 9.18 11.02 -1.83
halo
466 peak 10.02 11.23 -1.21
8.93 10.43 -1.50
8.68 9.08 -0.39
8.73 10.19 -1.46
8.84 9.12 -0.28
Average 9.06 10.18 -1.11

9. Cause of CL Halos in Quartz
0.25 mm

10. Types of CL halos –
Inclusion halos
0.25 mm
 Halos surrounding mineral inclusions,
typically zircon and monazite, that
contain radionuclides
 Halos reflect inclusion contours and
can resemble a bullseye when the
inclusion is small
0.25 mm

11. Types of CL halos –
CL grain rims
0.25 mm
 Orange CL that extends into
the grain from its edge and
follows the edge contour
 CL rims can be continuous
around the entire grain or
occur only along parts of grains
0.25 mm

12. Types of CL halos –
CL rim spots
0.25 mm
 Rim spots can result from:
0.25 mm – Grain boundary intersecting an
 Similar to CL rims but the rim is inclusion halo where the inclusion
made of discontinuous spots of CL grain has been liberated during
that resemble half of an inclusion sedimentary transport (right)
halo – Radioactive mineral grain located
 Can occur individually on a grain adjacent to the quartz grain
boundary or in clusters boundary (left)

13. Distribution of CL features across the roll-front
Distal Proximal Proximal Distal
Oxidized Oxidized Mineralized Reduced Reduced
Oxidized: Mineralized: Reduced:
 Continuous CL rims are  Continuous CL rims  Continuous CL rims are
less abundant than most common vary rare, less than 1
near the mineralized radiation damage grain per field of view
zone, 1-3 grains per feature, 1-5 grains per  Inclusion halos are
field of view field of view somewhat rare
 Inclusion halos  Inclusion halos  Rim spots are rare
somewhat common common
 Rim spots rare  Rim spots somewhat
rare

14. Distal Proximal Proximal Distal
Oxidized Oxidized Mineralized Reduced Reduced
Oxidiation -> Reduction -> U
mobilization of U precipitation
CL rims
Fluid flow and
CL rims possible, very
U transport CL rims very
but rare common rare
 CL rims and some CL rim spots are associated with the roll-front
mineralization
– Inclusion halos are distributed relatively evenly across the roll-front
– Individual CL rim spots are most common in samples that also have
abundant inclusion halos
 The Three Crow roll-front is either advancing very slowly or is stagnant
– The abundance of CL rims broadly correlates to the uranium content
of the samples

15. Key Points
 The formation of CL rims on quartz
grains is associated with roll-front
mineralization
– Rim damage more abundant
within and upstream of
mineralization
– CL rim abundance correlates to U
content
 Amorphization of the crystal
structure is the likely cause of the
change in CL color
– No change in major element
concentration between halos and
unaltered quartz
– Major Raman bands broaden and
background increases

16. Future Work
 Transmission Electron Microscopy
– Confirm the amorphization of the
quartz crystal structure with
exposure to alpha radiation
– Determine the extent of the
correlation of the amorphization
with CL halos
 Fission track mapping
– Map uranium distribution with
respect to the CL rims
 Additional Raman analysis
– Map additional CL features
– Determine the extent of the
correlation of peak broadening to
CL halos

17. Acknowledgements
 Cameco and Cameco
Resources
– Providing funding and
access to core
 Colorado School of Mines
– Seth Griffiths for Raman
instruction