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Studies of possible controls on the variability of radon potential of two East Midlands ironstones

Hodgkinson, E.S.; Scheib, C.; Jones, D.G.; Davis, J.. 2012 Studies of possible controls on the variability of radon potential of two East Midlands ironstones. British Geological Survey, 94pp. (IR/06/128) (Unpublished)

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Abstract/Summary

Jurassic ironstones consist of several formations, which, in the East Midlands, crop out in a thin band across the region. They stretch from north east of Gainsborough in Lincolnshire, through east Leicestershire, Northamptonshire and then curve gently towards the south-east, through Oxfordshire. Ironstones have been worked over a long period for their iron content, mainly opencast but with a limited number of underground workings (e.g. Hollingworth and Taylor, 1951; Tonks, 1989, 1991, 1992; Whitehead et al, 1952). Although no longer used as an iron ore, they are still quarried in a few places for buildings stone and as a source of aggregates. The Jurassic ironstones are known to be associated with a higher than average radon risk, as determined by house and soil gas data (e.g. Appleton and Ball, 1995, Sutherland and Sharman, 1996), and this is not uniform across the ironstones. High resolution airborne survey data (HiRES-1, Peart et al, 2003) showed elevated levels of eU (equivalent uranium, derived from the 214Bi gamma peak) and eTh (equivalent thorium, derived from the 208Tl gamma peak) for the ironstones, but also showed variability in these elements. It has been suggested that the primary source of radon in the ironstones is in phosphates (Sutherland, 1992) but the regional variations have not been investigated in detail. The study presented here was carried out in order to examine possible geological factors that might give rise to geographical variations in radon both within each ironstone formation and between formations. The objectives were as follows: (i) To characterise the large to medium (i.e. regional to outcrop) scale variation in the radioactivity of the ironstones, using airborne data acquired by the HiRES-1 project, and fieldbased gamma spectrometry. (ii) To sample ironstones from a number of locations and undertake laboratory-based petrographic, geochemical and radiographic studies in order to determine the mineralogy/petrology of radiogenic minerals and their efficiency in radon generation. (ii) To compare these two datasets and determine to what extent mineralogical and petrographical controls on radon levels affect surface radioactivity on a field scale. (iii) Finally, to try to relate smaller scale variability (hand specimen to outcrop scale) to larger scale regional variations in radon risk based largely on indoor radon measurements.

Item Type: Publication - Report (UNSPECIFIED)
Programmes: BGS Programmes 2010 > Land Use, Planning and Development
Funders/Sponsors: NERC
Additional Information. Not used in RCUK Gateway to Research.: This item has been internally reviewed but not externally peer-reviewed
NORA Subject Terms: Earth Sciences
Date made live: 24 Feb 2012 14:51
URI: http://nora.nerc.ac.uk/id/eprint/16695

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