scholarly journals Anisotropic Differences in the Thermal Conductivity of Rocks: A Summary from Core Measurement Data in East China

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1135
Author(s):  
Yibo Wang ◽  
Zhuting Wang ◽  
Lin Shi ◽  
Yuwei Rong ◽  
Jie Hu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Structure ◽  
Eastern China ◽  
Measurement Data ◽  
East China ◽  
Metamorphic Rocks ◽  
Strong Anisotropy ◽  
Conductivity Anisotropy ◽  
Development And Utilization

The study of thermal conductivity anisotropy is of great importance for more accurate heat flow calculations, geodynamic studies, development and utilization of hot dry rock, and simulation of heat transfer in geological reservoirs of nuclear waste, and so on. To study the thermal conductivity anisotropy of rocks, 1158 cores from 60 boreholes in East China were tested for thermal conductivity, including thermal conductivity values parallel to (λ∥) and perpendicular to (λ⊥) structural planes of basalt, mudstones, gneisses, sandstones, carbonates, evaporites, and metamorphic rocks. The thermal conductivity anisotropy is not obvious for sand, clay, and evaporate, and the average anisotropic factors of 1.19 ± 0.22, 1.18 ± 0.17, and 1.18 ± 0.17 for tuff/breccia, granitoid and contact metamorphic rocks, respectively, indicate that these three rocks have strong anisotropy characteristics. Finally, the effect of thermal conductivity anisotropy on heat flow is studied and discussed in detail, showing that the results of thermal conductivity tests have a significant effect on the calculation of heat flow and thermal structure, and the data show that a deviation of about 10% in thermal conductivity causes a deviation of about 11% in heat flow, which may lead to a misperception of deep thermal structure studies. The regular and anisotropic characteristics of thermal conductivity of various rocks in Eastern China obtained in this paper can provide parameter support for projects such as heat flow calculations, thermal structure studies, and geothermal resource development and utilization.

scholarly journals Present-day geothermal regime of the Uliastai Depression, Erlian Basin, North China

2018 ◽  
Vol 37 (2) ◽  
pp. 770-786 ◽  
Author(s):  
Wei Xu ◽  
Shaopeng Huang ◽  
Jiong Zhang ◽  
Ruyang Yu ◽  
Yinhui Zuo ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Structure ◽  
Rheological Characteristic ◽  
Rheological Parameter ◽  
Lithospheric Thickness ◽  
Terrestrial Heat Flow ◽  
Geothermal Regime ◽  
Mantle Heat Flow ◽  
Erlian Basin

In this study, we calculated the present-day terrestrial heat flow of the Uliastai Depression in Erlian Basin by using systematical steady-state temperature data obtained from four deep boreholes and 89 thermal conductivity measurements from 22 boreholes. Then, we calculated the lithospheric thermal structure, thermal lithospheric thickness, and lithospheric thermo-rheological structure by combining crustal structure, thermal conductivity, heat production, and rheological parameter data. Research from the Depression shows that the present-day terrestrial heat flow ( qs) is 86.3 ± 2.3 mW/m2, higher than the average of 60.4 ± 12.3 mW/m2 of the continental area of China. Mantle heat flow ( qm) in the Depression ranges from 33.7 to 39.3 mW/m2, qm/ qs ranges from 40 to 44%, show that the crust plays the dominant position in the terrestrial heat flow. The thermal thickness of the lithosphere is about 74–88 km and characterized by a “strong crust–weak mantle” rheological characteristic. The total lithospheric strength is 1.5 × 1012 N/m under wet mantle conditions. Present-day geothermal regime indicates that the Uliastai Depression has a high thermal background, the activity of the deep-seated lithosphere is relatively intense. This result differs significantly from the earlier understanding that the area belongs to a cold basin. However, a hot basin should be better consistent with the evidences from lithochemistry and geophysical observations. The results also show the melts/fluids in the study area may be related to the subduction of the Paleo-Asian Ocean. The study of the geothermal regime in the Uliastai Depression provides new geothermal evidence for the volcanic activity in the eastern part of the Central Asian Orogenic Belt and has significant implications for the geodynamic characteristics.

Measurement of the thermal conductivity of thin layers using a scanning thermal microscope

2001 ◽  
Vol 16 (9) ◽  
pp. 2530-2543 ◽  
Author(s):  
Erwin R. Meinders
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Structure ◽  
Thin Layers ◽  
Heat Diffusion ◽  
Sputter Deposited ◽  
Relative Differences ◽  
Conductivity Of Thin Films ◽  
Change Material

A scanning thermal microscope (SThM) was used to measure the thermal conductivity of thin sputter-deposited films in the thickness range of 10 nm–10 μm. The SThM method is based on a heated tip that is scanned across the surface of a sample. The heat flowing into the sample is correlated to the local thermal conductivity of the sample. Issues like the contact force, the surface roughness of the sample, and tip degradation, which determine to a great extent the contact area between tip and surface, and thus the heat flow to the sample, are addressed in the paper. A calibration curve was measured from known reference materials to quantify the sample heat flow. This calibration was used to determine the effective thermal conductivity of samples. Further, the heat diffusion through a layered sample due to a surface heat source was analyzed with an analytical and numerical model. Measurements were performed with films of aluminum, ZnS–SiO2, and GeSbTe phase change material of variable thickness and sputter-deposited on substrates of glass, silicon, or polycarbonate. It is shown in the paper that the SThM is a suitable tool to visualize relative differences in thermal structure of nanometer resolution. Determination of the thermal conductivity of thin layers is possible for layers in the micrometer range. It is concluded that the SThM is not sensitive enough to measure accurately the thermal conductivity of thin films in the nanometer range. Suggestions for improvement of the SThM method are given.

scholarly journals Shear heating reconciles thermal models with the metamorphic rock record of subduction

2018 ◽  
Vol 115 (46) ◽  
pp. 11706-11711 ◽  
Author(s):  
Matthew J. Kohn ◽  
Adrian E. Castro ◽  
Buchanan C. Kerswell ◽  
César R. Ranero ◽  
Frank S. Spear
Keyword(s):  
Heat Flow ◽  
Subduction Zones ◽  
Thermal Structure ◽  
Metamorphic Rocks ◽  
Shear Stresses ◽  
Thermal Models ◽  
Average Value ◽  
Temperature Conditions ◽  
Mechanical Models ◽  
Shear Heating

Some commonly referenced thermal-mechanical models of current subduction zones imply temperatures that are 100–500 °C colder at 30–80-km depth than pressure–temperature conditions determined thermobarometrically from exhumed metamorphic rocks. Accurately inferring subduction zone thermal structure, whether from models or rocks, is crucial for predicting metamorphic reactions and associated fluid release, subarc melting conditions, rheologies, and fault-slip phenomena. Here, we compile surface heat flow data from subduction zones worldwide and show that values are higher than can be explained for a frictionless subduction interface often assumed for modeling. An additional heat source––likely shear heating––is required to explain these forearc heat flow values. A friction coefficient of at least 0.03 and possibly as high as 0.1 in some cases explains these data, and we recommend a provisional average value of 0.05 ± 0.015 for modeling. Even small coefficients of friction can contribute several hundred degrees of heating at depths of 30–80 km. Adding such shear stresses to thermal models quantitatively reproduces the pressure–temperature conditions recorded by exhumed metamorphic rocks. Comparatively higher temperatures generally drive rock dehydration and densification, so, at a given depth, hotter rocks are denser than colder rocks, and harder to exhume through buoyancy mechanisms. Consequently––conversely to previous proposals––exhumed metamorphic rocks might overrepresent old-cold subduction where rocks at the slab interface are wetter and more buoyant than in young-hot subduction zones.

Heat production and thermal conductivity of rocks from the Pikwitonei–Sachigo continental cross section, central Manitoba: implications for the thermal structure of Archean crust

1987 ◽  
Vol 24 (8) ◽  
pp. 1583-1594 ◽  
Author(s):  
David M. Fountain ◽  
Matthew H. Salisbury ◽  
Kevin P. Furlong
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Cross Section ◽  
Heat Production ◽  
Thermal Structure ◽  
Granulite Facies ◽  
Surface Heat ◽  
Gamma Ray Spectrometry ◽  
Surface Heat Flow ◽  
Greenstone Belts

The Pikwitonei and Sachigo subprovinces of central Manitoba provide a cross-sectional view of the Superior Province crust. In cross section, the upper to mid-level crust is composed of synformal greenstone belts surrounded by tonalitic gneisses, both of which are intruded by granitoid plutons. This crustal structure persists downward into the granulite facies, where keels of the greenstone belts can be found. To constrain thermal models of the crust, we measured heat production and thermal conductivity in 60 rocks from this terrain using standard gamma-ray spectrometry and divided bar techniques. Large vertical and lateral heterogeneities in heat production in the upper crust are evident; heat production is high in granites and metasedimentary rocks, intermediate in tonalite gneisses, and low in the portions of greenstone belts dominated by mafic meta-igneous rocks. In the deeper granulite facies rocks, heat production decreases by a factor of two in the tonalitic gneisses and remains low in the high-grade mafic rocks. When applied to the Pikwitonei–Sachigo crust cross section, the laboratory data here do not support step function or exponential models of the variation of heat production with depth. However, estimates of surface heat flow and surface heat production for various sites in the crustal model yield the well-known linear relationship between surface heat production and surface heat flow observed for heat-flow provinces for both one- and two-dimensional models. This demonstrates that determinations of heat production with depth based on inversion of the linear heat-production–heat-flow relationship are nonunique.

On the possibility of anisotropic heat flow in the inner core

2001 ◽  
Vol 38 (6) ◽  
pp. 975-982 ◽  
Author(s):  
R A Secco ◽  
P S Balog
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
High Temperature ◽  
Heat Flow ◽  
Seismic Anisotropy ◽  
Inner Core ◽  
Elevated Pressure ◽  
Conductivity Anisotropy ◽  
Anisotropic Thermal Conductivity ◽  
Thermally Driven

We consider the possibility of anisotropic heat flow in the inner core by examining the potential for anisotropic thermal conductivity of hexagonal close-packed (hcp-)Fe. Because hcp-Fe exists only at pressures above 13 GPa at room temperature, we investigate thermal conductivity anisotropy in analog material Gd by measuring the electrical conductivity and applying the Wiedemann–Franz Law to determine thermal conductivity (k). The electrical conductivity anisotropy of Gd was measured at pressures up to 1.4 GPa and temperatures up to 873 K in the hcp phase range. At elevated pressure, the variation with temperature of anisotropic thermal conductivity of Gd single crystal resembles the anisotropic behavior at high temperature and 1 atm observed in earlier work. The temperature range of anisotropy of thermal conductivity of Gd, where kc > ka, is extended by pressure, but the anisotropy disappears before the high temperature hcp[Formula: see text]bcc (body-centered cubic) transformation. Our results on hcp-Gd lead us to raise the question of the possibility of hcp-Fe exhibiting anisotropy of thermal conductivity. Together with the known seismic anisotropy of the inner core, and the inferred textural alignment of hcp crystals causing it, we suggest some implications that an anisotropy of thermal conductivity of hcp-Fe, and a concomitant anisotropy of inner core heat flow, could have on thermally driven core processes.

scholarly journals Heat Flow in the Cretaceous of Northwestern Kansas and Implications for Regional Hydrology

1997 ◽  
pp. 1-11
Author(s):  
Andrea Forster ◽  
Daniel F. Merriam
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Structure ◽  
Flow Density ◽  
Thermal Gradients ◽  
Conductive Heat ◽  
Flow Estimation ◽  
Average Value ◽  
Dakota Formation ◽  
Porosity And Permeability

Temperature logs are interpreted to investigate the thermal structure of the units overlying the Kansas portion of the Cretaceous Dakota aquifer. The aim of this study is to determine if additional heat input by fluids exists and thus clarify whether the overall conductive heat flow from the basement through the sequence might be overprinted by heat advection. Although interval thermal gradients are determined for different lithologic (stratigraphic) units, the shale thermal gradients are preferred for heat-flow estimation. Shale thermal conductivity as measured in Mesozoic shales in Nebraska and South Dakota is extrapolated to the area because of the similar lithology. A few thermal-conductivity values are determined in sandstone samples of the Dakota Formation and also used in heat-flow estimation. In general, the noncalcareous, marine Cretaceous shales (Pierre, Carlile, Graneros, and Kiowa) show different thermal gradients. Gradients in the Pierre (average value 58.5°C/km) and Carlile (55.5°C/km) are slightly higher than the average gradient in the Graneros Shale (45.1°C/km) and Kiowa Formation (46.5°C/km). The higher thermal gradients are limited to the extreme northwestern corner of the study area where the Pierre and Carlile are present. The heat-flow density of 69-74 mW/m2 observed there is slightly higher than the average of 60 mW/m2 typical for central and eastern Kansas. The higher heat flow observed is in the range of data reported and mapped for northeastern Colorado and the Nebraska Panhandle on the western flank of the Chadron Arch, an area with geothermal overprint by warm fluids. Regional differences in heat flow in western Kansas seemingly are caused by the different composition, porosity, and permeability of the aquifer and the nearness to recharge areas.

scholarly journals Shallow subsurface thermal structure onshore Denmark: temperature, thermal conductivity and heat flow

2020 ◽  
Vol 67 ◽  
pp. 29-52
Author(s):  
Ingelise Møller ◽  
Niels Balling ◽  
Claus Ditlefsen
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Structure ◽  
Temperature Gradients ◽  
Core Material ◽  
Clear Correlation ◽  
Mean Values ◽  
Shallow Subsurface ◽  
Clay Deposits ◽  
Thermal Conductivities

Available measured temperatures and thermal conductivities covering Danish onshore areas to a depth of about 300 m have been compiled and analysed. Temperature data from 236 borehole sites, including 56 boreholes with detailed temperature profiles, are applied together with thermal conductivities mea- sured on samples collected at 34 well-characterised outcrops and on core material from 20 boreholes. Significant thermal variations in the shallow subsurface are observed. At a depth of 50 m, a mean temperature of 8.9 ± 0.8°C is found, close to the mean annual surface temperature. Higher mean values of 9.7 ± 1.1°C found at 100 m and 11.6 ± 2.2°C at 200 m reflect a general increase of temperatures with depth. In contrast to the assumption commonly held, we observe significant lateral variations both lo- cally and regionally. At a depth of 100 m, temperatures vary between 7.3 and 13.0°C across Denmark, and at 250 m between 9.6 and 17.9°C. Mean values of the thermal conductivities lie within a range of 0.6–6 W/(m·K) measured water- saturated at laboratory conditions. The majority of values are within the interval of 1–3 W/(m·K) and show a strong correlation with lithology. The content of quartz and the rock porosity (the content of water) are found to be two main factors controlling the observed variations. Characteristic temperature gradients are in the range 1–4°C/100 m. Following Fourier’s law of heat conduction, a clear correlation is observed between temperature gradients and thermal conductivities of different lithologies. Intervals of quartz-rich sand deposits with high thermal conductivity show low temperature gradients, chalk and limestone intervals with intermediate conductivity display intermediate gradients, while sections with fine grained clay deposits of low thermal conductivity show high gradient values. A correlation analysis provides an estimate of regional shallow heat flow of 37 ± 5 mW/m2, consistent with local, classically determined heat-flow values from shallow borehole data. However, it is significantly below deep background heat flow, and this is believed to be caused by long-term paleoclimatic effects. The shallow subsurface thermal regime across the Danish area is largely controlled by thermal conduction. Only locally, and in rare cases, do we observe temperature perturbations due to ground- water migration. In addition to general geoscientific purposes, our results are important for several applications including exploitation of shallow geothermal energy and the use of the subsurface for heat storage and cooling purposes.

scholarly journals Thermal structure of the deep Lopra-1/1A borehole in the Faroe Islands

2006 ◽  
Vol 9 ◽  
pp. 91-107 ◽  
Author(s):  
Niels Balling ◽  
Niels Breiner ◽  
Regin Waagstein
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
High Precision ◽  
Thermal Structure ◽  
Temperature Gradients ◽  
Depth Interval ◽  
Faroe Islands ◽  
Precision Temperature ◽  
Lapilli Tuff

Information on temperature, temperature gradients, thermal conductivity and heat flow from the c. 3.5 km deep Lopra-1/1A borehole in the Faroe Islands is presented and analysed. The upper 2450 m of the drilled sequence consists of thick tholeiitic basalt flows and the deeper parts of hyaloclastites and thin beds of basalt. Temperature data originate from high precision temperature logging a long time after drilling to a depth of 2175 m (the original Lopra-1 borehole) and from commercial temperature logs measured a short time after drilling to a depth of 3430 m (Lopra-1/1A). The high-precision temperature log determines accurately levels of inflow of groundwater to the borehole and significant thermal disturbances to a depth of c. 1250 m. Below 1300 m, no significant disturbances are seen and interval temperature gradients for large depth intervals show only small variations between 28 and 33°C/km. The mean least-squares gradient for the depth interval of 1400–3430 m is 31.4°C/ km. In clear contrast to these overall very homogeneous, large-interval, mean temperature gradients, great local variability, between gradients of 20–25°C/km and 45°C/km, was observed between about 1300 and 2175 m (maximum depth of the high-resolution temperature log). These gradient variations are interpreted to be due to thermal conductivity variations and to reflect varying secondary mineralisation and mineral alterations. A preliminary analysis of the Lopra-1/1A temperature–depth function in terms of long-term palaeoclimatic signals indicates subsurface temperatures below about 1300 m to be in equilibrium with mean surface temperatures significantly below zero during the last glacial period. A subsequent temperature increase of 12–16°C occurred at around the termination of the last glaciation. The measured temperatures (some after correction) and the thermal regime below 1300 m seem to represent conductive equilibrium conditions without significant disturbances from the effect of drilling, groundwater flow or long-term palaeoclimatic surface temperature variations. Thermal conductivity measured on samples of basalt taken from drill cores and surface outcrops in the area of the borehole shows values within a rather narrow range and a well-defined mean value for low porosity basalts of about 1.8 W/m°C , while a few samples of lapilli-tuff/tuff from the borehole gave values around 1.9 W/m°C . Lapilli-tuff and tuff seem to have higher matrix (grain) conductivity than basalt. Heat flow is estimated at 60 ± 5 mW/m2. A heat flow of this magnitude is consistent with the Faroe Islands being underlain by continental crust.

AN INSTRUMENT FOR MEASURING HEAT FLOW, TEMPERATURE, AND THERMAL CONDUCTIVITY IN THE LUNAR SURFACE LAYER

1970 ◽  
Author(s):  
A. E. Wechsler ◽  
E. M. Drake ◽  
F. E. Ruccia ◽  
J. E. McCullough ◽  
P. Felsenthal ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Surface Layer ◽  
Heat Flow ◽  
Lunar Surface ◽  
Flow Temperature
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