Hostname: page-component-78c5997874-fbnjt Total loading time: 0 Render date: 2024-11-19T23:26:16.810Z Has data issue: false hasContentIssue false
  • English
  • Français

The evolution of saline and thermal groundwaters in the Carnmenellis granite

Published online by Cambridge University Press:  05 July 2018

W. M. Edmunds ,
J. N. Andrews ,
W. G. Burgess ,
R. L. F. Kay  and
D. J. Lee
W. M. Edmunds
Affiliation:
British Geological Survey, Hydrogeology Unit, Wallingford, Oxon OX10 8BB
J. N. Andrews
Affiliation:
School of Chemistry, University of Bath, Bath BA2 7AY
W. G. Burgess
Affiliation:
British Geological Survey, Hydrogeology Unit, Wallingford, Oxon
R. L. F. Kay
Affiliation:
British Geological Survey, Hydrogeology Unit, Wallingford, Oxon
D. J. Lee
Affiliation:
Atomic Energy Establishment, Winfrith, Dorset
Get access Rights & Permissions [Opens in a new window]

Abstract

The Carnmenellis granite and its aureole contain the only recorded thermal groundwaters (up to 52 °C) in British granites. They occur as springs in tin mines at depths between 200 and 700 m and most are saline (maximum mineralization 19 310 mg 1−1). Mining activity has disturbed the groundwater circulation pattern developed over a geological time-scale and levels of bomb-produced tritium (> 4 TU) indicate that a significant component (up to 65 %) of the most saline waters are of recent origin. All components of all the mine waters are of meteoric origin. Radiogenic 4He contents, 40Ar/36Ar ratios, and uranium series geochemistry suggest that the thermal component has a likely residence time of at least 5 × 104 years and probably of order 106 years.

The thermal waters have molar Na+/Cl− ratios considerably less than 1 but they are enriched relative to sea water in all major cations except Mg. The groundwater is also particularly enriched in Li with contents ranging up to 125 mg 1−1. The groundwater salinity, which may reach a maximum of 30 000 mg 1−1, is shown to result from weathering reactions of biotite (probably through a chloritization step) and plagioclase feldspar, to kaolinite. On volumetric considerations, fluid inclusions cannot contribute significantly to the groundwater salinity, and stable isotope ratios rule out any contribution from sea water.

Groundwater silica contents and molar Na+/K+ ratios suggest that the likely equilibration temperature is 54°C, which would imply a depth of circulation of about 1.2 km.

Type
Research Article
Information
Mineralogical Magazine , Volume 48 , Issue 348 , September 1984 , pp. 407 - 424
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1984

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Alderton, D. H. M., and Rankin, A. H. (1983) Geol. Soc. 140, 297–309 [M.A. 83M/2666],CrossRefGoogle Scholar
Alderton, D. H. M. and Sheppard, S. M. F. (1977) Trans. Inst. Mining Met all. (B). 86, 191.4 [M.A. 78-1844],Google Scholar
Alexander, J., Hall, D. H., and Storey, B. C. (1981) Rept. Inst. Geol. Sci. ENPU 81–10.Google Scholar
Al-Saleh, S., Fuge, R., and Rea, W. J. (1977) Proc. Ussher Soc. 4, 37.48 [M.A. 78-2047],Google Scholar
Al-Turki, K. I., and Stone, M. (1978) Ibid. 4, 182-9 [M.A. 79-1700],Google Scholar
Andrews, J. N., and Kay, R. L. F. (1982) Nature. 298, 361.3 [M.A. 83M/2830].CrossRefGoogle Scholar
Andrews, J. N., (1983) Isotope Geoscience. 1, 101-17.Google Scholar
Andrews, J. N. and Lee, D. J. (1979) J. Hydrol. 41, 233-52.CrossRefGoogle Scholar
Andrews, J. N., Giles, I. S., Kay, R. L. F., Lee, D. J., Osmond, J. K., Cowart, J. K., Fritz, P., Barker, J. F., and Gale, J. (1982) Geochim. Cosmochim. Acta. 46, 1533.43 [M.A. 83M/ 3330],CrossRefGoogle Scholar
Batchelor, A. S., and Pearson, C. M. (1979) Trans. Inst. Mining Metall. (B). 88, 51-6.Google Scholar
Baxter, M. S., Ergin, M., and Walton, A. (1969) Radiocarbon. 11, 43-52.CrossRefGoogle Scholar
Beer, K. E., Edmunds, W. M., and Hawkes, J. R. (1978) Energy. 3, 281-92 [M.A. 79-1376],CrossRefGoogle Scholar
Bradshaw, P. M. D., and Stoyel, A. J. (1968) Trans. Inst. Mining Metall. (B), 77, 144-52 [M.A. 69-1384],Google Scholar
Bristow, C. M. (1969) In Rept. 23rd lnt. Geol. Congr. Czechoslovakia (1968), 15, Academia, Prague, 275-88.Google Scholar
Burgess, W. G., Edmunds, W. M., Andrews, J. N., Kay, R. L. F., and Lee, D. J. (1982) The Origin and Circulation of Groundwater in the Carnmenellis Granite: the Hydrogeochemical Evidence. Rept. Inst. Geol. Sci., London.Google Scholar
Collins, J. H. (1912) Trans. R. Geol. Soc. Cornwall. 14, 695.pp.Google Scholar
Cook, J. M., and Miles, D. L. (1980) Rept. Inst. Geol. Sci. 80/5, HMSO, London, 55 pp. [M.A. 81-2273],Google Scholar
Craig, H. (1961) Science. 33, 1702-3.CrossRefGoogle Scholar
Dines, H. G. (1956) The Metalliferous Mining Region of South-West England. Mem. Geol. Surv. Gt. Brit. HMSO, London, 795 pp.Google Scholar
Durrance, E. M., Bromley, A. G., Bristow, C. M., Heath, M. J., and Penman, J. M. (1982) Proc. Ussher Soc. 5, 304-20 [M.A. 83M/3333].Google Scholar
Edmonds, E. A., McKeown, M. C. and Williams, M. (1969) British Regional Geology: South West England. HMSO, London, 130 pp.Google Scholar
Ellis, A. J. (1970) Geothermics Special Issue. 2, 516-28.CrossRefGoogle Scholar
Ellis, A. J. and Mahon, W. A. J. (1977) Chemistry and Geothermal Systems. Academic Press, New York, 392 pp.Google Scholar
ERDA (Energy Research and Development Administration) (1977) Rept. No. 1. of Hot Dry Rock Assessment Panel. ERDA 77–74. Springfield.Google Scholar
Exley, C. S. (1959) Q. J. Geol. Soc. 114, 197-230.CrossRefGoogle Scholar
Exley, C. S. and Stone, M. (1964) In Present Views of Some Aspects of the Geology of Cornwall and Devon. 150th Anniversary Vol. Trans. R. Geol. Soc. Cornwall, 131-84.Google Scholar
Foster, S. S. D., and Smith-Carington, A. K. (1980) J. Hydrol. 46, 343-64.CrossRefGoogle Scholar
Fournier, R. O. (1970) Proc. Symp. Hydrogeochem. Bio- geochem. 7-9 September 1970, Tokyo. Hydrogeochem. I, The Clarke Co., Washington, 122-39.Google Scholar
Fournier, R. O. and Truesdell, A. H. (1973) Geochem. Cosmochim. Acta. 37, 1255-75.CrossRefGoogle Scholar
Frape, S. K., and Fritz, P. (1982) Can. J. Earth Sci. 19, 645-61 [M.A. 82M/4455],CrossRefGoogle Scholar
Fuge, R. (1974) In Handbook of Geochemistry (Wedehpohl, K. H., ed.). Springer, Berlin. Ch. 17.Google Scholar
Fuge, R. and Power, G. M. (1969) Geochim. Cosmochim. Acta, 33, 887-93.CrossRefGoogle Scholar
Jackson, N. J., Halliday, P. N., Sheppard, S. M. F., and Mitchell, J. G. (1982) In Metallization Associated with Acid Magmatism (Evans, A. M., ed.). Wiley, New York, 137-9 [M.A. 82M/4452],Google Scholar
Langmuir, D. (1978) Geochim. Cosmochim. Acta. 42, 547-69 [M.A. 79-1295],CrossRefGoogle Scholar
Miller, W. A. (1865) Rept. Br. Ass. Advancement Sci. (34th Meeting), 35-6.Google Scholar
Nordstrom, D. K. (1983) Proc. NEA Workshop on Geologic Disposal of Radioactive Wastes; In-situ Experiments in Granite. Stockholm, Sweden. 25-27 October 1982. NEA, Paris, 143-53.Google Scholar
Paces, T. (1972) Geochim. Cosmochim. Acta. 36, 217-40.CrossRefGoogle Scholar
Phillips, J. A. (1873) Land. Edinb. Dubl. Phil. Mag. (B), 46, 26–36.CrossRefGoogle Scholar
Rankin, A. H., and Alderton, D. H. M. (1983) Mineralium Deposita, in press.Google Scholar
Rankin, A. H., Alderton, D. H. M. and Thompson, M. (1982) Mineral. Mag. 46, 179-86.CrossRefGoogle Scholar
Sawkins, F. J. (1966) Trans. Inst. Mining Metall. (B). 75, 109-12.Google Scholar
Sheppard, S. M. F. (1977) J. Geol. Soc. 133, 573-91.CrossRefGoogle Scholar
Tammemagi, H. Y., and Wheildon, J. (1974) J. Geophys. J. R. astr. Soc. 38, 83–94.CrossRefGoogle Scholar
Walton, N. R. G. (1982) Rept. Inst. Geol. Sci. 81/5. HMSO, London [M.A. 83M/0572],Google Scholar
Wheildon, J., Francis, M. F., and Thomas-Betts, A. (1977) Seminar on Geothermal Energy, Brussels, EUR 5920, 1, 175-88.Google Scholar
Wheildon, J., Francis, M. F., Ellis, J. R. L., and Thomas-Betts, A. (1980) In Advances in European Geothermal Research (Strub, A. S. and Ungemach, P., eds.). Proc. 2nd lnt. Seminar on Results of EC Geothermal Energy Research, Strasbourg, 456-65.CrossRefGoogle Scholar