Skip to main content Accessibility help

Hydrothermal Sr contamination of the Dippin sill, Isle of Arran, Western Scotland

  • A. P. Dickin (a1), C. M. B. Henderson (a2) and F. G. F. Gibb (a3)


The Dippin sill, which is emplaced into the Triassic sediments of SE Arran, is an alkaline basic sheet which displays pronounced hydrothermal alteration. The 40-m-thick sill has suffered pervasive contamination with radiogenic Sr, introduced from the Triassic sediments by hydrothermal fluids. Stable isotope measurements suggest that fluids were of meteoric origin, but were restricted to a small closed-system circulation. Initial 87Sr/86Sr ratios in the sill were raised from an original value of 0.7032 to a maximum of 0.7091, contamination being especially pronounced near the contacts at Dippin Head itself (localities 12 and 14) and in a drill core section through the sill above Dippin. Hydrothermal Sr was incorporated into an early-formed high-CaO, high-Sr analcime, which replaced unstable high-silica nepheline in interstitial patches. However, this high-CaO analcime, along with plagioclase, was later replaced by a low-CaO, low-Sr analcime, allowing Sr leaching from the margins of the sill. Hydrothermal fluids are thought to have migrated up to 1 km laterally, up the dip of the sill, mainly via tension joints forming in the cooling intrusion. Pooling of hot fluids at the upper end of the sill probably raised water/rock ratios in this region and allowed greater Sr contamination during mineralogical alteration. The undersaturated mineralogy of the sill accounts for its pervasive hydrothermal Sr contamination, which contrasts markedly with the relatively undisturbed Sr isotope compositions of Hebridean granites involved in hydrothermal systems.



Hide All
Blake, S. (1981) J. Geol. Soc. London. 138, 281-7.
Borthwick, J., and Harmon, R. S. (1982) Geochim. Cos- mochim. Acta (in press).
Clayton, R. N., and Mayeda, T. K. (1963) Ibid. 27, 4352.
Dickin, A. P. (1980) Geochemical and isotopic investigations of continental igneous rocks, with special reference to the British Tertiary igneous province. Unpubl. D.Phil. thesis, Oxford University.
Dickin, A. P. (1981a) Nature. 294, 342-7.
Dickin, A. P. (1981b) J. Petrol. 22, 155-89.
Dickin, A. P. (1983) Scott. J. Geol. 19, 235-42.
Dickin, A. P. and Exley, R. A. (1981) Contrib. Mineral. Petrol. 76, 98108.
Dickin, A. P. and Jones, N. W. (1983) Ibid. 82, 147-53.
Dickin, A. P. and Whyte, F. (1983) Scott. J. Geol. 19, 81-6.
Dickin, A. P., Exley, R. A., and Smith, B. M., (1980) Earth Planet. Sci. Lett. 51, 5870.
Dickin, A. P., Moorbath, S., and Welke, H. J. (1981) Trans. R. Soc. Edinburgh: Earth Sci. 72, 159-70.
Gibb, F. G. F., and Henderson, C. M. B. (1978) Scott. J. Geol. 14, 127.
Hawkesworth, C. J., and Morrison, M. A. (1978) Nature. 276, 381-3.
Henderson, C. M. B., and Gibb, F. G. F. (1977) Mineral. Mag. 41, 534-7.
Jaeger, J. C. (1957) Am. J. Sci. 255, 306-18.
O’Neil, J. R., and Taylor, H. P. (1967) Am. Mineral. 52, 141-4.
Pearce, J. A., and Cann, J. R. (1971) Earth Planet. Sci. Lett. 12, 339.
Smith, B. M., and Giletti, B. J. (1979) Eos, Trans. Am. Geophys. Union. 60, 417.(abstract).
Steiger, R. H., and Jager, E. (1977) Earth Planet. Sci. Lett. 36, 359-62.
Taylor, H. P. (1977) J. Geol. Soc. London. 133, 509-58.
Vallance, T. G. (1974) J. Petrol. 15, 79-96.
Whyte, F. (1960) Scott. J. Geol. 2, 107-21.
Whyte, F. (1980) Ibid. 16, 263-6.
Wood, D. A., Gibson, I. L., and Thompson, R. N. (1976) Contrib. Mineral. Petrol. 55, 241-54.

Hydrothermal Sr contamination of the Dippin sill, Isle of Arran, Western Scotland

  • A. P. Dickin (a1), C. M. B. Henderson (a2) and F. G. F. Gibb (a3)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed