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Thermal modelling
The results of the thermal modelling are graphically illustrated in Appendix C, Fig.
C2a-k. Modelling was performed on samples having enough measurable confined track
length, which is dependent on the U-content and the age of the sample. Hence, not in
all regions the latest cooling history could be modelled. AFTSolve models the
temperature range of the apatite partial annealing zone, thus the temperature range of
around 60°C to 110°C. All suggested cooling paths above or below the PAZ
temperatures are therefore only inferred from the modelling results, but are not
modelled themselves.
To model the time-temperature history of the granite samples from the Karakul-Mazar
belt, the Ar/Ar data and zircon fission track ages were also considered. Modelling was
started at the maximum boundary temperature of the program at 325°C with the Ar/Ar
biotite age of the sample. The southerly samples P20 to P24 have mean track lengths
between 12.4 �m to 13.4 �m indicating slow cooling through the partial annealing zone
(Fig. C2a-c). In contrast, samples P25 and P26 have mean track lengths of 14.4 �m and
a narrow track length distribution, suggesting fast cooling in Miocene times (Fig. C2de).
Cooling through the PAZ increases from 0.5°C/Ma in the south (P20) to 25°C/Ma in
the north (P25). From the modelling it is inferred that after passing the PAZ, the
samples show cooling rates in the range of 1.7°C/Ma to 3.2°C/Ma until reaching the
present day surface temperature of 20°C. The samples left the PAZ from ~23 Ma to
~12.5 Ma. In the modelling, the zircon fission track ages of 122 Ma (P26) and 108 Ma
(P25) were also considered and similar zircon fission track ages around 120 Ma were
assumed for the other 3 samples. The modelled cooling histories offer different best-fit
time-temperature paths during Mesozoic times for the samples: P20 shows a Mid to
Late Jurassic cooling event from about 300°C to 110°C, sample P22 Late Cretaceous
cooling in the same temperature range, whereas for sample P25 cooling from 300°C to
110°C is inferred for Eocene times. Samples P24 and P26 show constant moderate
cooling from about 1.2°C/Ma for the temperature range >110°C. Other modelling
attempts considered constrains around 150 Ma and 80 Ma, as these thermal events are
suggested from sediment samples from adjacent regions. Modelling solutions did not
show any difference in the goodness of the statistical parameters of modelled age and
track length nor was a mid-Jurassic cooling event well detectable from the cooling
paths.
Samples P17 and P15 from the Muzkol dome have apparent fission track ages around
15 Ma with track lengths between 14.1 �m to 14.7 �m suggesting fast cooling (Fig. 2fg).
The best fit models suggest nearly identical time-temperature evolutions for both
samples with very rapid cooling before entering the PAZ. Sample P17 cooled between
23 to 14 Ma with an inferred rate of 24.4°C/Ma. Cooling through the PAZ was modelled
with a rate of 14.3°C/Ma and final cooling to surface temperatures, starting around 11
Ma, is again inferred from the model with a rate of 3.6°C/Ma. Sample P15 cooled very
rapid at 16-15 Ma: the Ar/Ar biotite and potassium-feldspar ages and the zircon and
apatite fission track dates are within errors nearly identical. Upon entering the PAZ,
cooling seemed to have decreased to a rate of 18.5°C/Ma. Upon leaving the PAZ at
~12.3 Ma, the rate decreased to 3.3°C/Ma until reaching the today’s surface
temperature. In summary, the samples of the Muzkol dome show the highest average
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