Ailsa Craig - The history of a reference material

P.J. Potts and J.R. Holbrook

Department of Earth Sciences, The Open University, Walton Hall,
Milton Keynes, MK7 6AA, U.K.

Summary
Interest in Ailsa Craig at the Open University arose in 1973 with the requirement to prepare an in-house standard suitable for calibrating instrumental neutron activation analysis for the determination of rare earth elements and other key trace elements. At the suggestion of Ian Gibson (then of Bedford College University of London), the Ailsa Craig microgranite was adopted since this rock had a relatively high rare earth element content giving a flat chondrite-normalised abundance profile at about the 100 times chondrite level (though with a large negative europium anomaly). Considerable effort was put into the reliable calibration of this material both by standard additions and by comparison with USGS II reference samples (Potts et al. 6). In view of the experience gained with the use of this sample as a calibration standard, a proposal was made for the adoption of Ailsa Craig as a new reference material particularly for the analysis of selected trace elements (Potts, 7). Following acceptance of this proposal, the authors collected about 700 kg of "Blue Hone" Ailsa Craig during July 1984 and subsequently delivered this bulk sample to the CRPG, Nancy to undergo the preparation process (8).

References
(1) R.M. Macintyre (1973)
Lower Tertiary geochronology of the North Atlantic continental margins. In: R.T. Pidgeon, R.M. Macintyre, S.M.F. Sheppard and O. van Breeman. Geochronology and isotope geology of Scotland. Field guide and reference K1-K25 (European Colloquium on Geochronology III).

(2) J.J.H. Teall (1892)
On a micro-granite containing riebeckite from Ailsa Craig. Mineralogical Magazine, 9: 219-221.

(3) R.A. Howie and J.N. Walsh (1981)
Riebeckitic arfvedsonite and aenigmatite from the Ailsa Craig microgranite. Scottish Journal of Geology, 17, 123-128.

(4) R.R. Harding (1983)
Zr-rich pyroxenes and glauconite minerals in the Tertiary alkali granite of Ailsa Craig. Scottish Journal of Geology, 19: 219-227.

(5) R.K. Harrison, P. Stone, I.B. Cameron, R.W. Elliot and R.R. Harding (in press)
Geology, petrology and geochemistry of Ailsa Craig. Report of the British Geological Survey.

(6) P.J. Potts, O.W. Thorpe and J.S. Watson (1981)
Determination of the rare earth element abundances in 29 International rock standards by instrumental neutron activation analysis: a critical appraisal of calibration errors. Chemical Geology, 34: 331-352.

(7) P.J. Potts (1983)
Proposal for the adoption of a microgranite from Ailsa Craig, SW Scotland as a trace element rock reference sample. Geostandards Newsletter, 7: 345-346. ABSTRACTS

(8) K. Govindaraju (1987)
1987 Compilation report on Ailsa Craig Granite AC-E with the participation of 128 GIT-IWG laboratories. Geostandards Newsletter, 11: 203-255. ABSTRACTS

Geostandards Newsletter (1987), Vol. 11 No. 2 pp. 257-260



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