Annealing of fission tracks in widerange,

1
Annealing of fission tracks in wide-range,
radiation-damaged detrital zircon
Garver, J.I. Department of Geology, Union College
Zircon undergoes a crystalline-to-amorphous
transition by radiation damage, which causes
internal disorder and lowers retention and
stability of fission tracks. We have pursued
three research tracks to understand the
relationship between radiation damage and fission
tracks
Optical images of thin sections of highly damage
Cambrian detrital zircon, NY State
1 ZFT Ages of detrital zircon from Cambrian
strata (NY) range from 300 Ma to over 2000 Ma.
Where thermal maturity is low (west), ZFT grain
ages reflect provenance age of 550 Ma and 740
Ma. Samples with greater thermal maturity (east)
have old grains and also a young ZFT population
at 280-290 Ma, which coincides with Alleghanian
burial. 2 Annealing of Radiation Damage in
Grenville zircon. Annealing of large pegmatitic
zircons from the Grenville basement shows that
radiation damage is progressively removed at
temperatures well above those require for
fission track annealing. Compared to fission
damage, radiation damage is more resistant to
annealing under geological conditions.
3 Measurement of radiation damage by Raman
Spectroscopy. Grain-to-grain variation in
radiation damage can be used to explain
over-dispersion of ZFT grain ages in reheated
samples. Uranium concentration has a major effect
on the Raman spectral data of the v3 and v1
SiO4 bands from the zircons, and the amount of
radiation damage can probably be quantified from
these measurements.
Ongoing studies are aimed at relating Raman
wavenumber to annealing of heated detrital
samples of the Cambrian of eastern NY State.
Reset grains record the last thermal maximum that
was likely related to gas generation, which is
the current target of significant exploration in
the State.
Raman Laser scattering on zircon mount