An investigation of Irish thermal springs: provenance, pathways and potential Sarah Blake

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1 An investigation of Irish thermal springs: provenance, pathways and potential Sarah Blake IRETHERM Workshop, Dublin 1 st April 2016

2 Thermal springs in Ireland

3 Thermal springs in Ireland

4 Thermal springs in Ireland Springs range in temperature up to 25 C

5 Thermal springs in Ireland Springs range in temperature up to 25 C Irish groundwater typically C

6 Thermal springs in Ireland Springs range in temperature up to 25 C Irish groundwater typically C Located in S and E of island (ISZ)

7 Thermal springs in Ireland Springs range in temperature up to 25 C Irish groundwater typically C Located in S and E of island (ISZ) Issue from Carboniferous strata

8 Thermal springs in Ireland Springs range in temperature up to 25 C Irish groundwater typically C Located in S and E of island (ISZ) Issue from Carboniferous strata One example of small-scale utilisation of geothermal energy at Mallow swimming pool (19 C)

11 C Located in S and E of island (ISZ) Issue from

utilisation of geothermal energy at Mallow swimming

9 Thermal springs in Ireland Springs range in temperature up to 25 C Irish groundwater typically C Located in S and E of island (ISZ) Issue from Carboniferous strata One example of small-scale utilisation of geothermal energy at Mallow swimming pool (19 C) Mallow warm spring and swimming pool (Goodman et al., 2004)

10 Geological setting

11 Geological setting Maximum temperature (red) and electrical conductivity in µs/cm (blue) for each spring.

12 Geological setting Six springs in Leinster chosen for detailed investigation Cold groundwater data supplied by EPA Maximum temperature (red) and electrical conductivity in µs/cm (blue) for each spring.

13 Project aims and methods

14 Project aims and methods Provenance: Pathways: Potential:

15 Project aims and methods Provenance: determine the source aquifers of the thermal waters Pathways: Potential:

16 Project aims and methods Provenance: Pathways: determine the source aquifers of the thermal waters characterise the nature of the warm water delivery system Potential:

17 Project aims and methods Provenance: Pathways: Potential: determine the source aquifers of the thermal waters characterise the nature of the warm water delivery system investigate the possibility of deeper water circulation patterns which might offer higher temperature waters

thermal waters characterise the nature of the warm

deeper water circulation patterns which might offer

18 Project aims and methods Provenance: Pathways: Potential: determine the source aquifers of the thermal waters characterise the nature of the warm water delivery system investigate the possibility of deeper water circulation patterns which might offer higher temperature waters Hydrochemistry Time-lapse measurements Geophysics

19 Project aims and methods AMT October 2013 AMT July 2012 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

20 Project aims and methods AMT October 2013 Hydrochemical study AMT July 2012 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

21 Project aims and methods AMT October 2013 Hydrochemical study AMT July 2012 Forthcoming paper: Blake, S., Henry, T., Murray, J., Flood, R., Muller, M., Jones, A.G., Rath, V. Investigating the provenance of thermal groundwater using compositional multivariate statistical analysis: a hydrochemical study from Ireland. Under review at Applied Geochemistry (Special Issue on Geochemical Statistics)

22 Hydrochemical study main findings

23 Hydrochemical study main findings

24 Hydrochemical study main findings Two endmember types of thermal spring

25 Hydrochemical study main findings Two endmember types of thermal spring Type 1: Na-Cl-type Steady temperature Little influence from seasonal recharge Longer residence times Louisa Bridge, St. Edmundsbury

26 Hydrochemical study main findings Two endmember types of thermal spring Type 1: Na-Cl-type Steady temperature Little influence from seasonal recharge Longer residence times Louisa Bridge, St. Edmundsbury

27 Hydrochemical study main findings Two endmember types of thermal spring Type 1: Na-Cl-type Steady temperature Little influence from seasonal recharge Longer residence times Louisa Bridge, St. Edmundsbury Type 2: Ca-HCO 3 -type Variable temperature (warmer after recharge) Strong influence from seasonal recharge Less evolved hydrochemistry St. Gorman s Well

28 Hydrochemical study main findings Two endmember types of thermal spring Type 1: Na-Cl-type Steady temperature Little influence from seasonal recharge Longer residence times Louisa Bridge, St. Edmundsbury Type 2: Ca-HCO 3 -type Variable temperature (warmer after recharge) Strong influence from seasonal recharge Less evolved hydrochemistry St. Gorman s Well

29 Hydrochemical study main findings Time-lapse temperature (blue) and electrical conductivity (black) measurements (15 minute sampling interval).

30 Hydrochemical study main findings Most springs governed by carbonate dissolution

31 Hydrochemical study main findings Most springs governed by carbonate dissolution Na-Cl-type springs have a deep, non-carbonate source

32 Hydrochemical study main findings Most springs governed by carbonate dissolution Na-Cl-type springs have a deep, non-carbonate source Excess Cl from dissolution of evaporites

33 Hydrochemical study main findings Most springs governed by carbonate dissolution Na-Cl-type springs have a deep, non-carbonate source Excess Cl from dissolution of evaporites

34 Electromagnetic imaging of thermal springs

35 Electromagnetic imaging of thermal springs AMT October 2013 AMT July 2012 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

36 Electromagnetic imaging of thermal springs Carboniferous limestones low 1 porosity fracture and conduit flow AMT October 2013 AMT July 2012 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

37 Electromagnetic imaging of thermal springs Carboniferous limestones low 1 porosity fracture and conduit flow Used AMT to identify (electrically conductive) fluid pathways in the bedrock AMT October 2013 AMT July 2012 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

38 Kilbrook spring

39 Kilbrook spring AMT July 2012 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

40 Kilbrook spring AMT July 2012 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

41 Kilbrook spring AMT survey layout and geological map of Kilbrook

42 Kilbrook spring 3-D electrical resistivity models of the subsurface beneath Kilbrook spring

43 Kilbrook spring 3-D inversion using ModEM code (Egbert and Kelbert, 2012; Kelbert et al., 2014) 3-D electrical resistivity models of the subsurface beneath Kilbrook spring

44 Kilbrook spring Estimated depth of circulation >> 560m assuming geothermal gradient of 25 C/km 3-D electrical resistivity models of the subsurface beneath Kilbrook spring

45 St. Gorman s Well

46 St. Gorman s Well AMT October 2013 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

47 St. Gorman s Well AMT October 2013 Maximum temperature (red) and mean electrical conductivity in µs/cm (blue) for each spring.

48 St. Gorman s Well AMT survey layout and geological map of St. Gorman s Well

49 St. Gorman s Well 3-D electrical resistivity models of the subsurface beneath St. Gorman s Well

50 St. Gorman s Well 3-D resistivity model from ModEM inversion 3-D electrical resistivity models of the subsurface beneath St. Gorman s Well

51 St. Gorman s Well Estimated depth of circulation >> 500 m for maximum winter temperatures 3-D electrical resistivity models of the subsurface beneath St. Gorman s Well

52 Main conclusions

53 Main conclusions Provenance

54 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs

55 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs

56 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs

57 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways

58 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone

59 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone Cenozoic strike-slip faults NNW NNE oriented

60 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone Cenozoic strike-slip faults NNW NNE oriented Carboniferous normal faults (NE, or NW for cross-faults)

61 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone Cenozoic strike-slip faults NNW NNE oriented Carboniferous normal faults (NE, or NW for cross-faults) Estimated depths of circulation approx ,000 m

62 Main conclusions Kilbrook spring St. Gorman s Well

63 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone Cenozoic strike-slip faults NNW NNE oriented Carboniferous normal faults (NE, or NW for cross-faults) Estimated depths of circulation approx ,000 m Potential

64 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone Cenozoic strike-slip faults NNW NNE oriented Carboniferous normal faults (NE, or NW for cross-faults) Estimated depths of circulation approx ,000 m Potential Thickness of Carboniferous basins limits hydrothermal circulation

65 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone Cenozoic strike-slip faults NNW NNE oriented Carboniferous normal faults (NE, or NW for cross-faults) Estimated depths of circulation approx ,000 m Potential Thickness of Carboniferous basins limits hydrothermal circulation Thermal springs can be explained without a deep and hot aquifer, or even an enhanced geothermal gradient

66 Main conclusions Provenance Seasonally-driven hydrothermal circulation in limestone for Ca-HCO 3 springs Evidence for evaporite dissolution for Na-Cl-type springs Pathways Structural control - karstification and conduit flow in limestone Cenozoic strike-slip faults NNW NNE oriented Carboniferous normal faults (NE, or NW for cross-faults) Estimated depths of circulation approx ,000 m Potential Thickness of Carboniferous basins limits hydrothermal circulation Thermal springs can be explained without a deep and hot aquifer, or even an enhanced geothermal gradient Large volumes of high temperature waters at depth beneath springs not very likely

67 Main conclusions Practical implications

68 Main conclusions Practical implications Seasonal variations in temperature affect how much energy is available for abstraction

69 Main conclusions Practical implications Seasonal variations in temperature affect how much energy is available for abstraction St. Gorman s Well

70 Main achievements Practical implications Seasonal variations in temperature affect how much energy is available for abstraction Highly transmissive structures are extremely localised hard to target

71 Main achievements Practical implications Seasonal variations in temperature affect how much energy is available for abstraction Highly transmissive structures are extremely localised hard to target Need to understand the structures and how they interact for the greatest yields

72 Main conclusions Practical implications Seasonal variations in temperature affect how much energy is available for abstraction Highly transmissive structures are extremely localised hard to target Need to understand the structures and how they interact for the greatest yields 1 m cavity 7,000 m 3 /d 16.3 C Huntstown Fault

Acknowledgements IRETHERM is funded by Science Foundation Ireland (grant no. 10/IN.1/I3022) All members of the IRETHERM team (www.iretherm.

74 Acknowledgements IRETHERM is funded by Science Foundation Ireland (grant no. 10/IN.1/I3022) All members of the IRETHERM team ( Staff and students of DIAS and beyond who helped with data acquisition Landowners and tenants who kindly granted us access to their land My supervisors, co-authors and reviewers for their critical and constructive comments

Provided by the author(s) and NUI Galway in accordance with publisher policies. Please cite the published version when available.

Provided by the author(s) and NUI Galway in accordance with publisher policies. Please cite the published version when available. Title A multi-disciplinary investigation of the provenance, pathways and