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Fission Track Thermochronology – Reconstructing the Thermal and Tectonic Evolution of the Crust


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Author Gleadow A JW
ID P199003057


Fission track thermochronology is a well established
method for reconstructing the thermal histories of rocks
with particularly important applications in tectonic studies,
detecting low-grade thermal events, sedimentary basin
analysis and resource exploration. These applications take
advantage of the limited stability of fission tracks,
especially in apatite, when exposed to the temperatures
found in the upper 3-4 km of the crust. Apparent fission
track ages in apatites can define an invisible ‘stratigraphy’
in otherwise homogeneous rock masses that can give
valuable information on thermal, tectonic and erosional
events. Quantitative modelling of the thermal annealing
of tracks in apatite shows that distinctive profiles of
apparent fission track age can be related to a number of
simple thermal history styles. The main types of profile
observed tend to be either an essentially linear decrease of
apparent age with increasing depth, which relates to
continuous uplift and denudation, or a concave-upwards
profile produced by partial annealing in environments of
tectonic stability or burial. More complex thermal
histories produce compound profiles which are essentially
just combinations of these two elements. Track length
information allows the apparent age profiles to be
interpreted in much greater detail. Examples of the major
profile types have now been identified in various
geological environments and can be analysed to give
information about, for example, uplift and denudation
rates, the timing of uplift or low-grade thermal events and
maximum palaeotemperatures experienced during burial.