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Chemical denudation rates in SW-Iceland
64
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
C H E M I C A L D E N U D A T I O N R A T E S IN S W - I C E L A N D
GISLASON S.R. *, ARNORSSON S. * and ARMANNSSON H. ** • Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavik, Iceland • * National Energy Authority, Grensasvegur 9, IS-108 Reykjavik, Iceland
INTRODUCTION Global surficial geofluxes from the present to the Proterozoic have been studied extensively since the pioneering work of Garrels and Mackenzie 1971, (e.g. Meybeck, 1979; Walling and Webb, 1986; Tardy, 1989). The chemical denudation rate has been shown to be a function of runoff, rock type, temperature and relief. The present chemical denudation rate is at its maximum (80 tonnes/km2/year) in the mountainous regions of the humid temperate and tropical zones, but at its minimum (3 tonnes/ km2/year) in the deserts of the world(Meybeck, 1979). The objective of this paper is to assess the present rate of chemical denudation in SW-Iceland, using reported data on, fiver discharge, the size of discharge areas, and chemistry of rivers and precipitation in SW-Iceland. CHEMICAL DENUDATION RATES In order to assess the rate of chemical denudation from data on dissolved solids in river water a distinction between the contribution by weathering, oceanic aerosols, geothermal activity and pollution, is needed. The chemistry of precipitation in SW-Iceland has been monitored by the Icelandic Meteorological Office since 1958 (The Icelandic Meteorological Office, 1958-1981). The samples are integrated monthly samples from 1 to 3 meteorological stations. Data on the chemistry of precipitation from NE-Iceland is available for the summers of 1982 and 1983 as well as the winter precipitation on the north western part of the Vatnaj6kull glacier 1982 (Gislason and Rettig, 1986). This data base was used to define the chemistry of precipitation in
Iceland. The samples show near normal distribution around a mean pH of 5.4 with the standard deviation of 0.46. A plot of C1 versus all the major elements in Icelandic precipitation is shown in Figure a-e. The lines drawn on the diagrams represent the ratio of the given element versus C1 in mean ocean water as reported by Riley and Chester (1971). Na/C1, K/C1 and Mg/C1 ratios in Icelandic precipitation is close to the oceanic ratios (Fig.a, b and c), indicating a marine source only for these elements in the precipitation. The concentration of Ca and SO4 in Icelandic precipitation is higher than would be predicted by unfractionated marine contribution. In order to linearly regress the data shown in Fig. d and e, a constant enrichment which is independent of the amount of the marine contribution, is assumed. The nonmafine enrichment is represented by the intercept but the'slope of the line is due to the marine contribution. No significant difference in the salt ratios were detected from one meteorological station to the other. However, as shown by Sigurosson and Einarsson (1988), the amount of aerosol is greatest close to the cost and decreases inland as elevation increases. In order to calculate the amount of airborne dissolved or soluble solids to the discharge areas of the rivers it is assumed that all dissolved chlorine in the river water is airborne. Chloride concentrations in precipitation and in river water lie in the same range (Table 1, Figs. a-e) indicating that the source for this element in the river water is marine. Studies of chloride and boron in cold and thermal waters (up to 50 °C) in the NW-Peninsula indicate that even the warmest waters have dissolved insignificant amount of chloride from the rock, 1-3 ppm as compared with 10-25 total dissolved chloride in the water
65
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd I N T E R N A T I O N A L SYMPOSIUM, July, 2-8, 1990, Aix en Provence, France.
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.
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.
.
.
10 15 2 0 2 5 3 0 3 5 4 0 Glacial c o v e r %
Figures a to f : CI versus major elements in Icelandis precipitations. TABLE I Rivers
Valma Sog Bmara, Dynjandi Bruara, Efstadal Tungufljot Fossa Hvita, south
PjoFsa Olfusa EUioaar Pvera, Draghals Grimsa Floka Reykjadalsa Hvita, Kljafoss Pvera Noroura Hvita, Hvitarvellir Laxa, Vogatunga
TDSrivers ppm 163 50.5 49.1 43.2 44.1 67.7 53.3 65.7 52.5 56.3 39.6 49.8 54.7 96.2 43.8 57.9 44.4 47 44.2
Clrivers TDSprecip TDCchem.den Discharge ppm ppm ppm m3/sec 16.9 6.97 4.98 4.03 3.8 6.45 3.64 4.59 5.57 10.1 7.18 7.21 7.28 11.97 4.35 8.69 6.72 5.69 7.9
33.76 15.83 12.23 10.52 10.10 14.89 9.81 11.53 13.30 21.48 16.21 16.26 16.39 24.86 11.10 18.93 15.38 13.52 17.51
129.24 34.67 36.87 32.68 34.00 52.81 43.49 54.17 39.20 34.82 23.39 33.54 38.31 71.34 32.70 38.97 29.02 33.48 26.69
2.21 1 16.2 76.68 41.2 47.34 1.66 131.4 397 440.9 27.03 5.45 21.6 8.33 10.5 94.53 25.3 35.2 189.1 7.8
Area Glaciers Chem.den. kin2 krn2 t/km2 /year 55 1050 670 215 720 29 2000 7200 5760 270 44 313 155 210 1685 480 500 3550 142
270 420 1200 690
365
163.77 121.00 133.06 197.50 70.49 95.33 90.10 94.19 94.63 109.93 91.37 72.99 64.93 112.49 57.86 64.77 64.44 56.25 46.24
66
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
(Leosson, 1990) substantiating the above conclusion of the source of chloride in river water. Fresh tephra contains relatively high concentration of soluble salts of chloride and fluoride. These salts are removed within a few days from the tephra by rain water (Oskarsson, 1980). The data used for the river waters in this study, where collected in the period 1972-74. Hekla erupted in 1970 spreading tephra over a part of the Pjorsa river water shed. Yet, in Pjorsa the average chloride concentration is similar to those of rivers not affected by the tephra fall. All major airborne dissolved or soluble solids can be calculated from the dissolved chlorine in river waters, the linear equations shown in Figs. a-e, plus the total dissolved carbon in precipitation which is calculated assuming air saturation of pure water at 0°C, cast in terms of CO3 (1.63 ppm). The contribution of geothermal activity to the chemical denudation in Iceland is negligible with the exception of few small rivers, like Varma (Table 1), draining geothemmal fields. The runoff from high temperature geothermal systems is insignificant but the total natural runoff from low-temperature systems is 1.8 m3/sec (S~emundsson and Frioleifsson, 1980) which is small compared to the total runoff, 5500 m3/sec, for Iceland (Rist, 1956). The survey of Armannsson et al. (1972) and Rist (1974 & 1986) revealed that the rivers in SW-Iceland were virtually unpolluted with the exception of the fiver Varma which is also heavily affected by geothermal activity. The data base used for the dissolved solids budget, discharge and discharge area is the one of Armannsson e t al. (1973) and Rist (1974 & 1986). The rivers are 19, draining total of 16979 km 2 which is more than 16% of the total surface area of Iceland. Of these 16979 km2, about 2255 km2 or about 13%, is covered with glaciers. These rivers were monitored on a monthly basis for up to 23 months. The elevation of discharge areas ranges from near sea level up to 2000 m.a.s.l. The age of the rocks ranges from 1000 years to less than 14 m.years old and they are primarily of basaltic composition. The chemical denudation rate (tonnes/km2/year) is shown in Table 1 as well as average TDS of the rivers, average dissolved chlorine, calculated average TDS of precipitation, calculated average TDS caused by chemical denudation, average discharge at the time of sampling, the size of the discharge areas, and the discharge area covered by glaciers. According to Bjrrnsson (1987) about 74% of the runoff from the Ellioaar river discharge area is lost by groundwater flow and does, therefore, not enter the river. This loss is added to the average discharge (7.0 m3/sec)
for the EUioaar river. The atmospheric contribution to the total dissolved solids in Icelandic rivers range from 18% to more than 40% for watersheds that are closest to the coast. As would be expected for an island, this is considerable higher than the average 15% atmospheric contribution to the surface waters of the world (Meybeck, 1979). The weighted average chemical denudation for SW-Iceland is calculated using the rivers Olfusa, Pjorsa, Hvita in Western Iceland at Hvitarvellir, Laxa at Vogatunga and Ellioaar. Other rivers in Table 1 are tributaries to 01fusa or Hvita at Hvitarvellir. The rivers are weighted according to the size of their discharge areas (Table 1). The river Varma is not included since it is polluted and affected by geothermal activity, thus the total discharge area under consideration is 16922 km 2. The chemical denudation so calculated for SW-Iceland amounts to 86 tonnes/km2/year. This is two to three times higher than the average rate for the world as reported by Wallig and Webb (1986) and Garrels and Mackenzie (1971), respectively, and it is similar or higher than the rate in the mountainous ranges of the humid temperate and tropical zones of the world (Meybeck, 1979). This intensive rate of chemical denudation in SW-Iceland is considered to be due to high-runoff, the abundance of glassy basalt and forceful physical erosion. The dissolution rate of glassy basalts is about ten times that of crystalline basalts (Gislason and Eugster, 1987), the physical erosion in Iceland amounts to about 500 tonnes/km2/year (Tomasson, 1986) compared to about 178 tonnes/kxn2/year which is the average for the world (Meybeck, 1988), and the mean runoff is about 55 1/sec/km 2 compared to about 12 1/sec/km2 on average for the world (Meybeck, 1988). It is tempting to use the data in Table I to assess the effect of glacial cover on the chemical denudation rates as is shown in Fig. f. However, runoff and the abundance of reactive glassy basalts are probable more important variables as is reflected in the range of chemical denudation rates for watersheds, not covered by glaciers. ACKNOWLEDGEMENTS
The work described in this article has been supported by the Icelandic Science Foundation and the Research Foundation of the University of Iceland. REFERENCES Armannsson H, Magnusson H., Sigurosson P. og Rist S.
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
(1973) Efnarannsokn vatna. Vatnasvio Hvitar - ()lfusar; einnig Pjorsar vio Urrioafoss. Orkustofnun, OS - RI, Reykjavik (in Icelandic). BjOrnsson S. (1987) Vatnsbol Reykjavikur og vatnasvio Ellioaanna. Vatnio og landio, agrip erinda, 100-101 (in Icelandic). Garrels R.M. and Mackenzie F.T. (1971) Evolution of Sedimentary Rocks. New York, Norton, 397 p. Gislason S.R. and Rettig S. (1986) Meteoric water-basalt interactions in N.E, Iceland: Methods and analytical results. U.S. Geol. Survey Open-File Report 87, 49. Gislason S.R. and Eugster H.P. (1987) Metexmc water-basalt interactions : I. A laboratory study. Geochim. Cosmochm. Acta 51, 2841-2855. Leosson, M.A. (1990) Dissolved solids in 5-50°C well waters in southern NW-Peninsula. Unpubl. B.Sc. thesis, University of Iceland (in Icelandic). Meybock, M (1979) Concentrations des caux fluviales en 616ments majeurs et apports en solution aux oc6ans. Rev. G6ologie Dynamique et G6ographie Physique 21,215-246. Meybcck, M (1988) How to establish and use world budgets of rivedne materials. In: Physical and Chemical Weathering in Geochemical Cycles (A.Lerman and M.Meybeck eds.), Kluwer Academic Publishers, Dordrecht, 247-272. Oskarsson N. (1980) The interaction between volcanic gases and tephra : Fluorine adhering to tephra of the 1970 Hekla eruption. J. Vole. Geoth. Res. 8, 251-266. Riley J.P. and Chester R. (1971) Introduction to Marine
67
Chemistry. New York, Academic Press, 465 p. Rist S. (1956) Icelandic Fresh Waters, Raforkumalastjori Vatnameelingar, Reykjavik, 127 p. Rist S. (1974) Efnarannsokn vatna. Vatnasvio Hvitar 61fusar; einnig Pjorsar vio Urrioafoss. Orkustofnun., Reykjavik OSV7405 (in Icelandic). Rist S. (1986) Efnarannsokn vama. Borgarfj0rour, einnig Ellioaar i Reykjavik. Orkustofnun, Reykjavik OS-86070/VOD-03 (in Icelandic). Sigurosson F. and Einarsson, K. (1988) Groundwater resources of Iceland - availability and demand. J0kull, 38, 35-53. S~emundsson K. and Frioleifsson I.B. (1980) Geothermal heat and geology. Nattumfra~ingurinn 50, 157-188 (in Icelandic). Tardy Y. (1989) Geochemical cycles and global water-rock interactions from 4,000 millions years. WaterRock Interaction, Miles (ed.), Balkema, Rotterdam, 675-678. Tomasson H. (1986) Glacial and volcanic shore interactions. Part I : On land. In; Iceland costal and River Symposium Proceedings (G. Sigbjarnarson, ed), University of Iceland, Reykjavik, 7-16. The Icelandic Meteorological Office (1958-1981) Measurements of some elements in air and precipitation. Veorattan 1958 to 1981 (in Icelandic). Walling D.E. and Webb, B.W. (1986) Solutes in river systems. In : Solute Processes (S.T. Trudgill ed.), John Wiley & Sons Ltd., New York. 251-327.
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
C H E M I C A L D E N U D A T I O N R A T E S IN S W - I C E L A N D
GISLASON S.R. *, ARNORSSON S. * and ARMANNSSON H. ** • Science Institute, University of Iceland, Dunhagi 3, IS-107 Reykjavik, Iceland • * National Energy Authority, Grensasvegur 9, IS-108 Reykjavik, Iceland
INTRODUCTION Global surficial geofluxes from the present to the Proterozoic have been studied extensively since the pioneering work of Garrels and Mackenzie 1971, (e.g. Meybeck, 1979; Walling and Webb, 1986; Tardy, 1989). The chemical denudation rate has been shown to be a function of runoff, rock type, temperature and relief. The present chemical denudation rate is at its maximum (80 tonnes/km2/year) in the mountainous regions of the humid temperate and tropical zones, but at its minimum (3 tonnes/ km2/year) in the deserts of the world(Meybeck, 1979). The objective of this paper is to assess the present rate of chemical denudation in SW-Iceland, using reported data on, fiver discharge, the size of discharge areas, and chemistry of rivers and precipitation in SW-Iceland. CHEMICAL DENUDATION RATES In order to assess the rate of chemical denudation from data on dissolved solids in river water a distinction between the contribution by weathering, oceanic aerosols, geothermal activity and pollution, is needed. The chemistry of precipitation in SW-Iceland has been monitored by the Icelandic Meteorological Office since 1958 (The Icelandic Meteorological Office, 1958-1981). The samples are integrated monthly samples from 1 to 3 meteorological stations. Data on the chemistry of precipitation from NE-Iceland is available for the summers of 1982 and 1983 as well as the winter precipitation on the north western part of the Vatnaj6kull glacier 1982 (Gislason and Rettig, 1986). This data base was used to define the chemistry of precipitation in
Iceland. The samples show near normal distribution around a mean pH of 5.4 with the standard deviation of 0.46. A plot of C1 versus all the major elements in Icelandic precipitation is shown in Figure a-e. The lines drawn on the diagrams represent the ratio of the given element versus C1 in mean ocean water as reported by Riley and Chester (1971). Na/C1, K/C1 and Mg/C1 ratios in Icelandic precipitation is close to the oceanic ratios (Fig.a, b and c), indicating a marine source only for these elements in the precipitation. The concentration of Ca and SO4 in Icelandic precipitation is higher than would be predicted by unfractionated marine contribution. In order to linearly regress the data shown in Fig. d and e, a constant enrichment which is independent of the amount of the marine contribution, is assumed. The nonmafine enrichment is represented by the intercept but the'slope of the line is due to the marine contribution. No significant difference in the salt ratios were detected from one meteorological station to the other. However, as shown by Sigurosson and Einarsson (1988), the amount of aerosol is greatest close to the cost and decreases inland as elevation increases. In order to calculate the amount of airborne dissolved or soluble solids to the discharge areas of the rivers it is assumed that all dissolved chlorine in the river water is airborne. Chloride concentrations in precipitation and in river water lie in the same range (Table 1, Figs. a-e) indicating that the source for this element in the river water is marine. Studies of chloride and boron in cold and thermal waters (up to 50 °C) in the NW-Peninsula indicate that even the warmest waters have dissolved insignificant amount of chloride from the rock, 1-3 ppm as compared with 10-25 total dissolved chloride in the water
65
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd I N T E R N A T I O N A L SYMPOSIUM, July, 2-8, 1990, Aix en Provence, France.
40
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10 2 0
5
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I
60
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]
70
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60 70
80
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e i • ~" ~ • ~ • ~ • ,'~; • 10 2 0 3 0 40 50 6 0 7 0 8 0 CI ppm
.
0
5
.
.
.
10 15 2 0 2 5 3 0 3 5 4 0 Glacial c o v e r %
Figures a to f : CI versus major elements in Icelandis precipitations. TABLE I Rivers
Valma Sog Bmara, Dynjandi Bruara, Efstadal Tungufljot Fossa Hvita, south
PjoFsa Olfusa EUioaar Pvera, Draghals Grimsa Floka Reykjadalsa Hvita, Kljafoss Pvera Noroura Hvita, Hvitarvellir Laxa, Vogatunga
TDSrivers ppm 163 50.5 49.1 43.2 44.1 67.7 53.3 65.7 52.5 56.3 39.6 49.8 54.7 96.2 43.8 57.9 44.4 47 44.2
Clrivers TDSprecip TDCchem.den Discharge ppm ppm ppm m3/sec 16.9 6.97 4.98 4.03 3.8 6.45 3.64 4.59 5.57 10.1 7.18 7.21 7.28 11.97 4.35 8.69 6.72 5.69 7.9
33.76 15.83 12.23 10.52 10.10 14.89 9.81 11.53 13.30 21.48 16.21 16.26 16.39 24.86 11.10 18.93 15.38 13.52 17.51
129.24 34.67 36.87 32.68 34.00 52.81 43.49 54.17 39.20 34.82 23.39 33.54 38.31 71.34 32.70 38.97 29.02 33.48 26.69
2.21 1 16.2 76.68 41.2 47.34 1.66 131.4 397 440.9 27.03 5.45 21.6 8.33 10.5 94.53 25.3 35.2 189.1 7.8
Area Glaciers Chem.den. kin2 krn2 t/km2 /year 55 1050 670 215 720 29 2000 7200 5760 270 44 313 155 210 1685 480 500 3550 142
270 420 1200 690
365
163.77 121.00 133.06 197.50 70.49 95.33 90.10 94.19 94.63 109.93 91.37 72.99 64.93 112.49 57.86 64.77 64.44 56.25 46.24
66
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
(Leosson, 1990) substantiating the above conclusion of the source of chloride in river water. Fresh tephra contains relatively high concentration of soluble salts of chloride and fluoride. These salts are removed within a few days from the tephra by rain water (Oskarsson, 1980). The data used for the river waters in this study, where collected in the period 1972-74. Hekla erupted in 1970 spreading tephra over a part of the Pjorsa river water shed. Yet, in Pjorsa the average chloride concentration is similar to those of rivers not affected by the tephra fall. All major airborne dissolved or soluble solids can be calculated from the dissolved chlorine in river waters, the linear equations shown in Figs. a-e, plus the total dissolved carbon in precipitation which is calculated assuming air saturation of pure water at 0°C, cast in terms of CO3 (1.63 ppm). The contribution of geothermal activity to the chemical denudation in Iceland is negligible with the exception of few small rivers, like Varma (Table 1), draining geothemmal fields. The runoff from high temperature geothermal systems is insignificant but the total natural runoff from low-temperature systems is 1.8 m3/sec (S~emundsson and Frioleifsson, 1980) which is small compared to the total runoff, 5500 m3/sec, for Iceland (Rist, 1956). The survey of Armannsson et al. (1972) and Rist (1974 & 1986) revealed that the rivers in SW-Iceland were virtually unpolluted with the exception of the fiver Varma which is also heavily affected by geothermal activity. The data base used for the dissolved solids budget, discharge and discharge area is the one of Armannsson e t al. (1973) and Rist (1974 & 1986). The rivers are 19, draining total of 16979 km 2 which is more than 16% of the total surface area of Iceland. Of these 16979 km2, about 2255 km2 or about 13%, is covered with glaciers. These rivers were monitored on a monthly basis for up to 23 months. The elevation of discharge areas ranges from near sea level up to 2000 m.a.s.l. The age of the rocks ranges from 1000 years to less than 14 m.years old and they are primarily of basaltic composition. The chemical denudation rate (tonnes/km2/year) is shown in Table 1 as well as average TDS of the rivers, average dissolved chlorine, calculated average TDS of precipitation, calculated average TDS caused by chemical denudation, average discharge at the time of sampling, the size of the discharge areas, and the discharge area covered by glaciers. According to Bjrrnsson (1987) about 74% of the runoff from the Ellioaar river discharge area is lost by groundwater flow and does, therefore, not enter the river. This loss is added to the average discharge (7.0 m3/sec)
for the EUioaar river. The atmospheric contribution to the total dissolved solids in Icelandic rivers range from 18% to more than 40% for watersheds that are closest to the coast. As would be expected for an island, this is considerable higher than the average 15% atmospheric contribution to the surface waters of the world (Meybeck, 1979). The weighted average chemical denudation for SW-Iceland is calculated using the rivers Olfusa, Pjorsa, Hvita in Western Iceland at Hvitarvellir, Laxa at Vogatunga and Ellioaar. Other rivers in Table 1 are tributaries to 01fusa or Hvita at Hvitarvellir. The rivers are weighted according to the size of their discharge areas (Table 1). The river Varma is not included since it is polluted and affected by geothermal activity, thus the total discharge area under consideration is 16922 km 2. The chemical denudation so calculated for SW-Iceland amounts to 86 tonnes/km2/year. This is two to three times higher than the average rate for the world as reported by Wallig and Webb (1986) and Garrels and Mackenzie (1971), respectively, and it is similar or higher than the rate in the mountainous ranges of the humid temperate and tropical zones of the world (Meybeck, 1979). This intensive rate of chemical denudation in SW-Iceland is considered to be due to high-runoff, the abundance of glassy basalt and forceful physical erosion. The dissolution rate of glassy basalts is about ten times that of crystalline basalts (Gislason and Eugster, 1987), the physical erosion in Iceland amounts to about 500 tonnes/km2/year (Tomasson, 1986) compared to about 178 tonnes/kxn2/year which is the average for the world (Meybeck, 1988), and the mean runoff is about 55 1/sec/km 2 compared to about 12 1/sec/km2 on average for the world (Meybeck, 1988). It is tempting to use the data in Table I to assess the effect of glacial cover on the chemical denudation rates as is shown in Fig. f. However, runoff and the abundance of reactive glassy basalts are probable more important variables as is reflected in the range of chemical denudation rates for watersheds, not covered by glaciers. ACKNOWLEDGEMENTS
The work described in this article has been supported by the Icelandic Science Foundation and the Research Foundation of the University of Iceland. REFERENCES Armannsson H, Magnusson H., Sigurosson P. og Rist S.
GEOCHEMISTRY OF THE EARTH'S SURFACE AND OF MINERAL FORMATION 2nd INTERNATIONAL SYMPOSIUM, July, 2-8, 1990, Alx en Provence, France.
(1973) Efnarannsokn vatna. Vatnasvio Hvitar - ()lfusar; einnig Pjorsar vio Urrioafoss. Orkustofnun, OS - RI, Reykjavik (in Icelandic). BjOrnsson S. (1987) Vatnsbol Reykjavikur og vatnasvio Ellioaanna. Vatnio og landio, agrip erinda, 100-101 (in Icelandic). Garrels R.M. and Mackenzie F.T. (1971) Evolution of Sedimentary Rocks. New York, Norton, 397 p. Gislason S.R. and Rettig S. (1986) Meteoric water-basalt interactions in N.E, Iceland: Methods and analytical results. U.S. Geol. Survey Open-File Report 87, 49. Gislason S.R. and Eugster H.P. (1987) Metexmc water-basalt interactions : I. A laboratory study. Geochim. Cosmochm. Acta 51, 2841-2855. Leosson, M.A. (1990) Dissolved solids in 5-50°C well waters in southern NW-Peninsula. Unpubl. B.Sc. thesis, University of Iceland (in Icelandic). Meybock, M (1979) Concentrations des caux fluviales en 616ments majeurs et apports en solution aux oc6ans. Rev. G6ologie Dynamique et G6ographie Physique 21,215-246. Meybcck, M (1988) How to establish and use world budgets of rivedne materials. In: Physical and Chemical Weathering in Geochemical Cycles (A.Lerman and M.Meybeck eds.), Kluwer Academic Publishers, Dordrecht, 247-272. Oskarsson N. (1980) The interaction between volcanic gases and tephra : Fluorine adhering to tephra of the 1970 Hekla eruption. J. Vole. Geoth. Res. 8, 251-266. Riley J.P. and Chester R. (1971) Introduction to Marine
67
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