## 3 Results and Discussion  
### Thin Section Analyses  
Several rock samples, collected at the Kizildere site, were shipped for thin section preparation. Table 7 presents the image analyses results and mineralogy obtained from the thin section analyses. The 2D area and perimeter, of the connected pores within an area of interest, were implemented in the 2D Carman-Kozeny equation [37; 38] to obtain the presented 2D permeability. Pixel size equals 10 \(\upmu\)m \(\times\) 10 \(\upmu\)m. Note that, due to preparation damage and a stress-free matrix, all 2D permeability values shown are likely to be overestimated by at least one order of magnitude. The results indicate that the presence of a fracture increases the 2D permeability by a factor of roughly 10 on average, compared to the matrix permeability only. The latter is in line with the fact that geothermal production in Kizildere is mainly dependent on fluid flow through fractures [33; 36]. The identified mineral composition might shed light on the acoustic behaviour, as a function of stress and temperature, of the various rock types studied. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \multicolumn{1}{c}{**Temp. Effect**} & \multicolumn{6}{c}{**Experiment**} \\ \hline Type & Calschist & Marble & Limestone & Quartzite & Silstone & Quartzchist & Mudstone & Micaschist \\ Code & TID12\(\times\)C66 & TID1-M7 & T52-S2.13 & TID20-Q2.3 & TX6-B1-1 & TD2-Q3-Q2. & TX6-B2. & TID25-M5-2 \\ Length (mm) & 60.1 \(\pm\) 0.1 & 61.3 \(\pm\) 0.1 & 60.4 \(\pm\) 0.1 & 61.2 \(\pm\) 0.1 & 65.0 \(\pm\) 0.1 & 61.8 \(\pm\) 0.1 & 42.0 \(\pm\) 0.1 & 36.1 \(\pm\) 0.1 \\ Diameter (mm) & 29.5 \(\pm\) 0.1 & 29.8 \(\pm\) 0.1 & 29.0 \(\pm\) 0.1 & 29.8 \(\pm\) 0.1 & 29.8 \(\pm\) 0.1 & 29.6 \(\pm\) 0.1 & 29.1 \(\pm\) 0.1 & 29.8 \(\pm\) 0.1 \\ Provisity (\%) & 3.10 \(\pm\) 0.16 & 2.34 \(\pm\) 0.19 & 3.97 \(\pm\) 0.21 & 4.46 \(\pm\) 0.10 & 25.10 \(\pm\) 0.05 & 2.99 \(\pm\) 0.15 & 17.89 \(\pm\) 0.17 & 7.78 \(\pm\) 0.08 \\ Matrix density & 2.76 \(\pm\) 0.01 & 2.75 \(\pm\) 0.01 & 2.72 \(\pm\) 0.01 & 2.89 \(\pm\) 0.01 & 2.77 \(\pm\) 0.01 & 2.84 \(\pm\) 0.01 & 2.85 \(\pm\) 0.01 & 2.91 \(\pm\) 0.01 \\ \(\text{Bulk density}\) (g/cm\({}^{3}\)) & 2.67 \(\pm\) 0.02 & 2.69 \(\pm\) 0.02 & 2.61 \(\pm\) 0.02 & 2.76 \(\pm\) 0.03 & 2.07 \(\pm\) 0.01 & 2.75 \(\pm\) 0.02 & 2.34 \(\pm\) 0.03 & 2.69 \(\pm\) 0.03 \\ Additional \(\sigma_{1}\) (MPa) & 0.070 \(\pm\) 0.001 & 0.068 \(\pm\) 0.001 & 0.072 \(\pm\) 0.001 & 0.068 \(\pm\) 0.001 & 0.068 \(\pm\) 0.001 & 0.069 \(\pm\) 0.001 & 0.072 \(\pm\) 0.001 & 0.068 \(\pm\) 0.001 \\ Temperature (\({}^{\circ}\)C) & 40–240 & 40–240 & 40–240 & 40–240 & 40–240 & 40–240 & 40–240 & 40–240 & 40–240 \\ \hline \end{tabular}
\end{table} 
Table 6: Properties of the core samples used for studying the effect of temperature on seismic velocity. Figure 3: Schematic of the set-up used for assessing the effect of temperature on seismic velocity. \begin{table} \begin{tabular}{c c c c c c c} \hline
**Type** & **Calcchist** & **Marble** & **Limestone** & **Micashist** & **Quartzschist** \\ \hline Code & TD11-B & TD1-B & TS1-B5 & TD24-B & TD23-B \\ \hline Areny porosity & Ind. fracture: 1.3 & Total \({}^{4}\) : 1.6 & & & & \\ (\%) & Excl. fracture: 0.4 & Effective \({}^{6}\) : 0.4 & Effective \({}^{6}\) : 0.4 & Effective \({}^{6}\) : 0.4 & & \\ \hline
2D Carman- & & & & & & \\ Kozeny & & & & & & \\ Demethylship (D) & 2.5 & 2.2 & 12.4 & 2.6 & 24.1 \\ Ind. fracture 1  & 0.3 & 0.1 & - & - & 5.7 \\ Matrix only 2  & & & & -Calcite and & & \\ \hline  & -Calcite and & & & & & \\ dolomite & & -Calcite and & & organic matter) & 89 & and ankerite & \\ Mineralog (recrystallised) & 98 & dolomite & 99 & -Angular quartz & 8 & -Muscovite and & 25 \\ (area\(\%\))3  & -Muscovite and & 1 & (recrystallised) & 1 & -Organic matter & 1 & and feldspar & 2 & sercite \\  & -specific & +1 & -Something & & and oxides & -Smetic & -c1 & -Quartz and & 45 \\  & -Quartz or & (haloysite) & & (vermiculite) & & feldspar & \\ feldspar & & -Biotite remnants & & & -Biotite remnants & & \\ \hline \end{tabular}