The age and origin of the Bath thermal waters : new geochemical investigations as part of the Bath Spa Project

Edmunds, W.M.; Darling, W.G.; Purtschert, R.; Corcho, J.. 2002 The age and origin of the Bath thermal waters : new geochemical investigations as part of the Bath Spa Project. Nottingham, UK, British Geological Survey, 26pp. (CR/01/263N) (Unpublished)

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Abstract/Summary

The most comprehensive geochemical investigation to date has been carried out on the Bath thermal waters using samples obtained from the Stall Street borehole and the Cross Bath in August 2000. Prior to the current investigation the available evidence pointed to a Holocene age for recharge of the thermal water, but with an ill-defined lower limit. The use of the isotope 39Ar in this study has now indicated that the bulk residence time of the thermal water exceeds 1000 years. Indications of a Holocene age were confirmed by the new results, and the thermal component now emerging is most probably some 5-10 thousand years old. However, stable isotopic evidence from confined groundwaters in the vicinity suggests that the thermal circulation may have been in operation since at least as far back as the late Pleistocene. Solute and dissolved gas data show that the thermal water has evolved predominantly within the Carboniferous Limestone, with little or no evidence for contributions from the underlying Old Red Sandstone or overlying Coal Measures. The rise to the surface of the thermal water from a depth of ~3km is sufficiently slow to allow a temperature drop of some 20°C, pointing to the existence of a complex fracture network. Best estimates for Carboniferous Limestone porosities at depth imply a large (basin-wide) storage volume for the thermal water. Earlier indications of the presence of a small proportion of modern water in the thermal discharge have been confirmed by noble gas and chlorofluorocarbon data to amount to some 5% by volume. This component now requires better characterisation in terms of fluctuations due to seasonal or other short-term factors, in order that its provenance can be better understood and any water quality implications fully appreciated.

Item Type:	Publication - Report
Programmes:	BGS Programmes > Groundwater Management
Funders/Sponsors:	British Geological Survey, University of Bern
Additional Information. Not used in RCUK Gateway to Research.:	This item has been internally reviewed, but not externally peer-reviewed.
Date made live:	25 Sep 2024 15:17 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538080

Item Type:

Publication - Report

Programmes:

BGS Programmes > Groundwater Management

Funders/Sponsors:

British Geological Survey, University of Bern

Additional Information. Not used in RCUK Gateway to Research.:

This item has been internally reviewed, but not externally peer-reviewed.

Date made live:

25 Sep 2024 15:17 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/538080