NOTICE CONCERNING COPYRIGHT RESTRICTIONS

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1 NOTICE CONCERNING COPYRIGHT RESTRICTIONS This document may contain copyrighted materials. These materials have been made available for use in research, teaching, and private study, but may not be used for any commercial purpose. Users may not otherwise copy, reproduce, retransmit, distribute, publish, commercially exploit or otherwise transfer any material. The copyright law of the United States (Title 7, United States Code) governs the making of photocopies or other reproductions of copyrighted material. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specific conditions is that the photocopy or reproduction is not to be "used for any purpose other than private study, scholarship, or research." If a user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of "fair use," that user may be liable for copyright infringement. This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law.

2 Geothermal Resources Council, TRANSACTIONS Vol., October 8 THE THERMAL CONDUCTIVITY OF SOME CRYSTALLINE AND SEDIMENTARY ROCKS FROM SCANDINAVIA Jan I. Kristiansen, Svend Saxov and Niels Balling Laboratory of Geophysics University of Aarhus Aarhus, Denmark ABSTRACT Some available information on thermal conductivity of earth materials from the Scandinavian area is collected. The mean conductivities as reported from individual localities are grouped in crystalline and sedimentary rocks. Mean results are displayed in histograms and localities are mapped. The collocation of conductivity information contains new results of granites and sedimentary rocks from Sweden and of limestones and clays from Danish borings. The new values are presented as histograms of individual measurements and given as mean values with standard errors of mean. The crystalline rocks range from - to -4 W/(m K), and the sedimentary rocks range from -0.8 to - W/(m K). INTRODUCTION Thermal conductivity is an important parameter in the study of terrestrial heat flow and subsurface temperatures. Also in the search for areas which have potential as geothermal resources, information about the conductivities of a wide variety of earth materials is essential. The Scandinavian region mainly comprises of parts of the Precambrian Fennoscandian Shield, the Paleozoic Caledonian Orogenic Belt and the northeastern part of the Northwest European Sedimentary Basin. Thus the rock types of the region cover crystalline as well as sedimentary rocks. A fairly large number of conductivity results from Scandinavia have been reported, and the rocks which have been measured include many of those found in the region. The Fennoscandian Shield covers the largest part of the area of interest (Fig. ). The major parts of Sweden and Finland belong to this Precambrian shield, while only the southern and west central Norway is included. The rocks are mainly volcanics, metasediments, gneisses and granites. The Paleozoic Caledonian Orogenic Belt covers a large part of Norway and the northwestern Sweden. The rocks of these areas consist mainly of greenstones, amphibolites, metasediments, metavolcanics and various Caledonian intrusives. The Permian graben system in the Oslo area is an igneous province of minor extent. Here the rocks consist of alkaline intrusives and extrusives. The Danish area constitutes the northeastern part of the Northwest European Sedimentary Basin. Thick sequences of Paleozoic, Mesozoic and Cenozoic rocks are present in the central part of the Danish subbasin. A minor part of southern Sweden (Skane) is covered by similar sedimentary rocks. The islands of aland and Gotland (Sweden) are covered by ancient Paleozoic rocks, while the island of Bornholm (Denmark) consists of rocks from all four eras. Table. Rock types which are included in the collocation Amphibolite gneiss Anorthosite Carbonite Diabase Diorite Glimmerite Gneiss Granite gneiss Greenstone Hallaflinta Ilmenite Lep t ite Liparite Mica gneiss Mica schists Migmat i t e Pe gma t it e Peridotite Porphyr ie Rapakivi Serpentinite Sparagmite Syenite Alunshale Anhydrite Clay Clays t one Do lomi t e Greenschists Greywacke/shale Lake sediment Limes tone Rocks a t Sand Sandstone Si t s tone Quartzite COLLOCATION OF THERMAL CONDUCTIVITIES The Scandinavian thermal conductivities, which are considered here, are mainly measured by the divided bar method and the transient cylindrical probe method. In Sweden a modified probe method (Landstrbm et al., 80) has been used occasionaly.traditionally most measurements on crystalline rocks are made by the first method but also

3 Table. New sites of measurements. N: number of measurements, k: mean conductivity. The figures of the rock type correspond to Table. Locality Rock type N - E(w/(m K)) I a b C d e f g h i j k m n 0 Kalmar Bohus Degerhamn I Degerhamn Degerhamn Degerhamn 4 M r by snga Ottenby Gislovhammar Tommarp Tobbisborg Dalby-Sandby Harre Rrs Selde Figure. Sites of conductivity measurements and Tectonic map of Scandinavia.. indicates previous sites, + indicates new sites (identified by letters) and figures indicate rock type. the probe method has been used successfully in crystalline areas. The probe method is very suitable for measurements in most sedimentary rocks. It also applies to in situ conductivity determinations on lake sediments in Norway (Hanel et' al., 74). The conductivity results as considered here consist of existing information and of new measurements. Conductivities from Norway are reported by Swanberg et al. (74, Heier and Grgnlie (77, Hanel et al. (7) and GrBnlie et al. (80, from Sweden by Parasnis (75), Eriksson and Malmqvist (7), Poulsen et al. (8, and Malmqvist et al. (8), from Finland by JHrvimHki and Puranen (7, and from Denmark by Balling (7), Balling et al. (8, and (8). Not all conductivity results, which are contained in the above papers, are included in this work. Thus a few cases, where mean conductivities in the original papers are ascribed to more than one widely different rock type, are disregarded. A similar rejection of results has been used in cases where materials or results are considered not to be generally representative of a rock type. The rock types are presented in Table. The localities to which the conductivity samples relate are mapped in Fig., and the identifying figures are given in Table. As the present collocation of results is based on mean values, each box of the compiled histograms contains two figures: the first relates to the rock types, and the second to the number of measurements. The histograms shown in Fig. comprise the mean conductivities of crystalline and sedimentary rocks. The conductivities of crystalline rocks range from - to -4 W/(m K). The magnitude of the conductivity of a specific rock is highly dependent on the quartz content. The range of for example the values of grnites may be due to this. However, the overall conductivity range ascribed to crystalline rocks is narrow compared to that of sedimentary rocks. Here values range from -0.8 to - W/(m K), and the rock types show individually much broader distributions. Limestones range from -. to -. W/(m K), and sandstones from -. to -. W/(m K). Again the content of quartz is an important factor, but also the porosityhas a dominating effect. The porosity dependence of some Danish sediments has been investigated (Balling et al., 8). For water-saturated pure limestones it is shown that the conductivity (k) varies with POrosity ($) as follows: k = 0.58$.l-4. Apparently, similar formulas do not hold for other types of sediments within the same accuracy. 0 NEW CONDUCTIVITY VALUES New conductivities from the Swedish 0

4 CONDUCllVlll (Wlm MI CollWCllVllV (Wlm I) Figure. Conductivities of some Swedish granites and sedimentary rocks. "I m Figure 4. Conductivities of two clay sequences (Harre, Denmark). -- I 5 I CoNLIcTlvITv (WlmnI r t Figure 5. Conductivities of a clay sequence (Ars, Denmark) (left part), and of a limestone sequence (Selde, Denmark) (right part). Figure. Histograms of Scandinavian mean conductivities. Left part: crystalline rocks. Right part: sedimentary rocks. The first figure within a box indicates rock type and the last indicates the number of measurements. and Danish areas have been determined. The measurements have been carried out by the probe method on outcrops and on core materials. The equipments have been standardized against calibration materials. Their mode of operation as well as typical examp- les of measurements are given elsewhere (Balling et al., 8; Poulsen et al., 8;, 8). The interpretations of data are based on the line source model. A major part of the results have been compared with and agree with those obtained by the more accurate integral solution combined with the iterative least squares inversion procedure (Kristiansen, 8). In situ measurements on two granites from the Kalmar and Bohus areas and on five sedimentary rocks from Oland and Skine have been made. The localities and the results of the individual measurements are

given in Table and shown in Fig.. The sample sites are mapped on Fig. and characterized according to Tables and. These results show accordance with expected values for the rock types in question.

5 given in Table and shown in Fig.. The sample sites are mapped on Fig. and characterized according to Tables and. These results show accordance with expected values for the rock types in question. The laboratory measurements on homogeneous Danish core materials (Harre, Ars, Selde ) show accurately determined mean conductivities. The results appear in Table and Figs. 4 and 5. The localities are included in Fig.. Results of these types have been used for accurate heat flow determinations in Denmark (Balling et. al., 8). Our new results are included in the present collocation of data (Figs. and ). CONCLUSION Thermal conductivities of earth materials from Scandinavia are presented and collocated. Mean values of crystalline rocks range from - to -4 W/(m K) and show narrow individual distributions. Mean values of sedimentary rocks cover a larger range (-0.8 to - W/(m K)), and the individual distributions are broader. The wide range of the sedimentary results implies that temperature gradients in sedimentary areas are not constant with depth provided constant heat flow. The new results of Danish core materials show narrow distributions. Thus mean values for clays are 0.8 k0.0 W/(m K),.08?O.OlW/(m K), and.8 k0.0 W/(m K), and for limestone W/(m K). The new Swedish results which we have obtained are in accordance with expected values. REFERENCES Balling, N., 7, Subsurface temperatures and heat flow estimates in Denmark &I V. Cermiik and L. Rybach (eds), Terrestrial Heat Flow in Europe, Springer, p. -7. Balling, N., Kristiansen, J.I., Breiner,N., Poulsen, K.D., Rasmussen, R., and Saxov S., 8, Geothermal measurements and subsurface temperature modelling in Denmark, GeoSkrifter, 7 p. Eriksson, K.G. and Malmqvist, D., 7, A review of the past and the present in vestigations of heat flow in Sweden - in V. ZermCk and L. Rybach (eds), Terrestrial Heat Flow in Europe, Spri Springer, p Grenlie, G., Johansen, T.E., Karlstad, B., and Heier, K.S., 80, Prospecting for geothermal energy in the Iddefjord Norway, Norsk Geol. Tidsk. 0, p. -7. Hlnel, R., Grenlie, G., and Heier, K.S., 74, Terrestrial heat flow determinations from lakes in southern Norway, Norsk Geol. Tidsk. 54, p Hanel, R., Grenlie, G., and Heier, K.S., 7. Terrestrial heat flow determination in Norway and an attempted interpretation & V. Cermdk and L. Rybach (eds), Terrestrial Heat Flow in Europe, Springer, p. -. Heier, K.S. and Grenlie, G., 77, Heat flow - heat generation studies in Norway in S.K. Saxena and S. Bhattacharji (eds), Energetics of Geological Processes, Springer, p Jarvimlki, P. and Puranen, M., 7, Heat flow measurements in Finland V. EermLk and L. Rybach (eds), Terrestrial Heat Flow in Europe, Springer, p Kristiansen, J.I., 8, The transient cylindrical probe method for determination of thermal parameters of earth materials, GeoSkrifter (in press). Kristiansen, J.I., Saxov, S., Balling, N., and Poulsen, K.D., 8, In situ thermal conductivity measurements of Precambrian, Palaeozoic and Mesozoic rocks on Bornholm, Denmark, Geol. Fiire. i Stockholm Forh. 04 (in press). Landstrem, O., Larson, S.A., Lind, G., and Malmqvist, D., 80, Geothermal investigations in the Bohus granite area in southwestern Sweden, Tectonophysics, p.. Malrnqvist, D., Larson, S.A., Landstram, O., and Lind, G., 8, Heat flow andheat production from the Mallingsbo granite, central Sweden (personal communication - in press). Parasnis, D.S., 75, Temperature phenomena and heat flow estimates in two Precambrian ore-bearing areas in north Sweden, Geophys. J. R. astr. SOC. 4, p Poulsen, K.D., Saxov, S., Balling, N., and Kristiansen, J.I., 8, Thermal conductivity measurements on Silurian limestones from the island of Gotland, Sweden. Geol. Fiire. i Stockholm FZirh. 0, p Swanberg, C.A., Chessman, M.D., Simmons, G., Smithson, S.B., Granlie, G., and Heier, K.S., 74, Heat-flow - heat generation studies in Norway, Tectonophysics, p. la48.

NOTICE CONCERNING COPYRIGHT RESTRICTIONS

NOTICE CONCERNING COPYRIGHT RESTRICTIONS This document may contain copyrighted materials These materials have been made available for use in research, teaching, and private study, but may not be used for