Part - II
Application of the fission
track method in Geology
3 key questions
What geologic questions can be answered?
What sampling strategy is required?
How can we interpret our fission track data?
Part 2 - The application
What are the processes that we can
"date" with fission track data?
Very fast processes with rock cooling:
volcanic eruptions, intrusions with fast cooling,
hydrothermal event, shear heating along fault plane
Fast processes with rock cooling:
fast exhumation or erosion in an active orogen, fast
movements along faults (e.g. tectonic unroofing)
Moderately fast processes with rock cooling:
moderate exhumation or erosion, moderately cooling in
and around intrusive body,
Slow processes with rock cooling:
slow erosion or exhumation in a decaying orogen
Part 2 - The application
Real "dating" with the FT method
Only with fast to very fast cooling, the fission
track method is able to "date an event"
Potential events:
 volcanic eruption
 fast cooling intrusion
 impact event
 hydrothermal event
 shear heating along thrust plane
Part 2 - The application
Process rate estimation with the FT method
With moderate and slow cooling, the fission
track method only estimates cooling rates. It
does NOT necessarily mean an "event".
Possible processes:
 erosive denudation
 tectonic denudation
 topography formation
 thermal relaxation
Part 2 - The application
Fission track dating of a single event - I
Australian tektite
Glass drops ejected from
German impact crater
Part 2 - The application
Fission track dating of a single event - II
Bohemian Glass from
1849 with 1% of U can be
dated with FT
 check of the fission
decay constant
Part 2 - The application
Comparison between dating methods - I
Example from
German volcano
(Kraml et al., in
prep.):
apatite FT data
Part 2 - The application
Comparison between dating methods - II
Example from German volcano
(Kraml et al., in prep.):
Part 2 - The application
Comparison between dating methods - II
Part 2 - The application
FT dating and anthropology
Titanite
0.306 ± 0.056 Ma
Thermoluminescence
0.292 ± 0.026 Ma
0.312 ± 0.028 Ma
U-series dating
0.300 ± 0.040 Ma
Titanite
0.462 ± 0.045 Ma
(Guo et al. 1991)
Part 2 - The application
How do we know that the FT age
represents a single event ?
Track length distribution:
All tracks are long (mean length > 14.5 mm) and the track
length distribution is very narrow.
Radial plot:
All single grain ages plot in a narrow cluster (except for
very young ages or grains with low U content).
Statistical tests:
The calculated central age passes Poissonian c2 tests.
Isochrons:
The FT age is in agreement with ages from other dating
techniques (e.g. U/Pb, Ar/Ar, (U-Th)/He).
Absence of regional variation:
The FT age is identical within the same material, also if
sampled at other localities.
Part 2 - The application
100 km
Nanga
Parbat - I
Part 2 - The application
Fast exhumation
processes:
example Nanga
Parbat - II
25 km
Part 2 - The application
Fast exhumation processes:
example Nanga Parbat - III
Part 2 - The application
Fast exhumation
processes:
example Nanga
Parbat - IV
Part 2 - The application
Fast exhumation processes:
example Nanga Parbat - V
From:
Brozovic et al. (1997)
apatite FT ages:
A: 0-1 Ma
B: 1-6 Ma
C: 6-15 Ma
Part 2 - The application
Fast exhumation
processes:
example Taiwan - I
from Dadson et al. (2003):
Exhumation rates (mm yr-1)
based on apatite FT ages:
red: reset FT age
orange: partially reset
blue: not reset
Part 2 - The application
Fast exhumation
processes:
example Taiwan - II
from Dadson et al. (2003):
Bedrock incision rates
(mm yr-1) as derived from
age dating of fluvial
terraces
 much larger than
exhumation rates !
Part 2 - The application
Chicken or egg?
The main question in research today:
Who was first, erosion or tectonics ?
How can we know ?
 regional plate tectonic context
 very fast cooling points to tectonics
 climatic evidence
 accompagnying processes
 topography analysis
Part 2 - The application
Uplift - Exhumation - Denudation
(England &
Molnar 1990)
Part 2 - The application
The effect of topography
Part 2 - The application
Convex and concave T-t paths
Assumption:
topography evolves in a vertical direction only,
no lateral valley shift
Part 2 - The application
The effect of fluid flow
(from
Kohl & Rybach,
www.gtr.
geophys.ethz.ch/
neatpiora.html)
Part 2 - The application
Fault planes
and ages
Part 2 - The application
Fault movements in the Central Alps
Part 2 - The application
Exhumation in a cratonic continent - I
(Gleadow et
al. 2002)
Part 2 - The application
Exhumation in a cratonic continent - II
(Gleadow et
al. 2002)
 2750 apatite
FT ages
Part 2 - The application
Exhumation in a cratonic continent - III
(Gleadow et
al. 2002)
Part 2 - The application
Exhumation in a cratonic continent - IV
(Gleadow et
al. 2002)
Part 2 - The application
The principles of fission track data modelling
Part 2 - The application
The modelling of FT data: age and track length
Part 2 - The application
Genetic algorithm and shrinking of T-t-boxes
Part 2 - The application
Why are detrital zircons better than apatites?
Part 2 - The application
The lag time concept
Part 2 - The application
orogenic
cycle
Part 2 - The application
Uplift - erosion - topography
Davis (1899):
uplift is short-term
process
Penck (1953):
uplift is „waxingwaning“
Hack (1975): uplift
and topography
form steady-state
Part 2 - The application
Detrital age spectra:
static and younging age components
steady age component
younging age component
Part 2 - The application
raw data with error envelope
Probability density
plots of FT ages
statistical fit to density plot
fitted age populations
(from Garver
et al. 1999)
Part 2 - The application
Decrease and increase of lag time
(from Bernet
et al. 2001)
Part 2 - The application
Example: European Alps
pro-wedge
retro-wedge
Part 2 - The application
Example for a decrease of lag time
(from Bernet
et al. 2004)
Part 2 - The application
Example for a steady lag time
(from Bernet
et al. 2004)
Part 2 - The application
FT ages
along vertical
bore hole
Part 2 - The application
FT age
evolution
along vertical
bore hole
Part 2 - The application
FT age
evolution
along vertical
bore hole
Part 2 - The application
FT age
evolution
along vertical
bore hole
Part 2 - The application
example I:
bore hole @
Hünenberg
(from
Cederbom et
al., in press)
Part 2 - The application
example II:
Rigi Mountain
and bore hole
@ Weggis
(from
Cederbom et
al., in press)
Part 2 - The application
Exhumed PAZ at Denali, Alaska
(Fitzgerald
et al. 1995)
Part 2 - The application
Thank you for your attention !