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Thermal Conductivity 14
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Skip to Left Navigation Bar. Skip to Organizational Offices. The results of this study reveal large contrasts in thermal conductivity values among different rock types that can have major implications for future heat flow and geothermal modeling studies in these regions. Thermal conductivity is a thermal property that quantifies the ability of a material to conduct heat. Knowledge of thermal conductivity is essential in heat flow determinations as heat flow is calculated by multiplying the geothermal gradient with the thermal conductivity Jaeger Thermal conductivity is also an essential input parameter in thermal modeling investigations as it controls the steady-state temperature distribution within the Earth Blackwell and Steele In particular, the contrast in thermal conductivity between sediments and basement rocks may lead to significant temperature changes even if regional heat flow is constant Thakur et al , Erkan and Blackwell , Balkan and Salk Rock thermal conductivity also has important implications in oil and gas exploration, thermoelastic stress analysis, and geological disposal studies Pigford , Rutqvist et al , Feng et al Although western Turkey has many medium-to-high enthalpy geothermal systems Basel et al , detailed thermal models have not been developed due to a lack of direct thermal conductivity measurements and insufficient geothermal gradient data.
In particular, thermal conductivity information is necessary for estimating the Enhanced Geothermal System EGS potential of an area Tester et al This study aims to fill the gap in knowledge of thermal conductivities of the major lithologic units in western and central Anatolia. In Turkey, geothermic studies started at the beginning of the 20th century with ground temperature measurements for meteorological purposes Tezcan The first heat flow map of Turkey was published by Tezcan , and then improved by Tezcan and Turgay In these studies, heat flow values were calculated from non-equilibrium bottom-hole-temperature data from deep oil, gas, coal, and geothermal wells assuming a constant thermal conductivity of 2.
However, all of these studies assumed constant thermal conductivity values between 2—2. In these projects, thermal conductivity measurements from rock samples were made and reported without further analyses and corrections.
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Locations of the rock samples are given in figure 1. In this study, the raw thermal conductivity data are initially sorted according to the lithologic types encountered in western and central Anatolia regions, separately. Finally, the significance of the results is discussed by comparing with the general geologic and tectonic setting of each region.
Simplified geological map of the study area and location of rock samples. Note that more than one type of lithologic unit were collected at the same locations. The thermal conductivity of rocks depends on various parameters including mineral composition, porosity, anisotropy, and properties of pore-filling fluids. This leads to a large variability in thermal conductivities within each rock type sedimentary, igneous, and metamorphic rocks.
In this study, sedimentary, metamorphic, and igneous rocks are analyzed. The types of rock forming minerals directly control the thermal conductivity of a rock, and have a wide variety of values. Rock-forming minerals such as quartz and hematite have high thermal conductivities whereas clay, gypsum, and organic materials have low thermal conductivities table 1.
Minerals with high thermal conductivities cause an increase in rock thermal conductivity. For metamorphic rocks, high values for quartzite high quartz content and relatively low values for schist and gneiss low quartz content are expected. Besides the mineral composition, grain size and texture of the rock also determine how fast heat is transmitted through the rock Clauser Anisotropy may also significantly influence thermal conductivity of sedimentary and metamorphic rocks.
Clauser and Huenges Cermak and Rybach Brigaud et al , Clauser Melnikov et al Quiel Huenges Drury and Jessop The thermal conductivity of a rock also varies with porosity. Porosity is the first and foremost important factor that controls the bulk thermal conductivity for almost all rock types, particularly sedimentary and young volcanic rocks whose relative porosity are greater than metamorphic rocks.
Pore-filling materials water, air, oil, gas, etc have lower thermal conductivities than rock matrix which results in a decrease in the bulk thermal conductivity with increasing porosity Clauser and Huenges It is an effective and reliable technique for measuring thermal conductivity Grubbe et al , Sass et al In this study, the samples were initially classified according to lithological descriptions given in the dataset.
A summary of the entire dataset for the western Anatolia and central Anatolia regions is shown in table 2. Out of a total of rock samples, of them were collected from western Anatolia, and samples were collected from central Anatolia. Measurements in western Anatolia were conducted on dry samples, so they required corrections to saturated conditions for the determination of bulk thermal conductivities.
We analyzed 10 different representative rock types in western Anatolia. Table 3 lists the mean thermal conductivities of the rocks. In addition to the mean values for dry and saturated conditions, ranges of expected values are also given by taking the standard deviation of the assigned porosity.
Most of the rock samples belong to limestone units followed by claystone units. Ranges of expected values are also given for the saturated conditions. In western Anatolia, thermal conductivities in dry conditions vary between 0.
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Histograms for saturated thermal conductivity of certain lithologies are shown in figure 2. Claystone has the lowest thermal conductivity within all rocks. The thermal conductivity varies considerably for each rock type.
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Especially, clastic rocks which are mainly sandstone units show a wide range of conductivities as a result of variations in quartz contents as well as high porosity values. For metamorphic rocks, the thermal conductivities of schist and marble are 3. In igneous rocks, the mean thermal conductivity of peridotite is 2. In this study the mean thermal conductivity of igneous rocks is lower than that of metamorphic rocks. The results for central Anatolia are shown in table 4 with mean thermal conductivities and their standard deviations.
These samples were directly measured in saturated conditions, thus no correction for porosity had to be applied.
enter site The highest mean thermal conductivity value of 5. Tuff has the lowest mean thermal conductivity value of 1. Thermal conductivity values of saturated conditions and their standard deviations in central Anatolia. Figure 3 shows histograms for the thermal conductivity of certain lithologies in central Anatolia. Limestones are the most common rock in central Anatolia and their ranges of thermal conductivity are wider than other types.
Turkey is located within the Mediterranean Earthquake Belt where complex deformation has occurred due to the continental collision among African, Arabian, and Eurasian plates. Each province shows unique structural components and tectonic features. The rock samples studied in this paper belong to western and central Anatolian provinces. The relationships of the tectonic and geologic settings along the major lithologic units encountered in these provinces are discussed below. The western Anatolia region is noted for its long and complicated geological history.
The western Anatolia province includes numerous grabens filled with volcano-sedimentary sequences dissecting Menderes Metamorphic Complex MMC figure 4. It includes many kinds of metamorphosed and igneous rocks from high to low grades, including gneiss, mica schists, phyllites, quartz schists, marbles, and granodiorites. We sampled two types of metamorphic rocks which are schist and marble table 3. According to our results, marble stands out with a high thermal conductivity of 2.
Marbles located in Menderes massif generally have high dolomite content Yavuz et al , which directly increases the thermal conductivity of the marble. Western Turkey is characterized by a number of suture zones figure 4 bearing wide areas of peridotite units. In our dataset, three peridotite samples from these suture zone show a mean value of 2.
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Try again? Cited by. Back to tab navigation Download options Please wait Supplementary information PDF K. Article type: Paper. DOI: Download Citation: J. Origins of ultralow thermal conductivity in quaternary selenides J. Kuo, U. Aydemir, J. Zhou, G. Yu, A. Faghaninia, F. Ricci, M. White, G.
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