Abstract
A Jurassic sequence of mudrocks, siltstones and limestones, at Down Ampney, Gloucestershire, was investigated. The aim was to evaluate the importance of faults in mudrocks as conduits for direct groundwater flow, and the influence of such faults on solute transport. Chemical analysis of porewaters and groundwaters are reported. Porewaters were obtained for analysis by squeezing mudrock core samples, yielding 18.1-34.5% of the total porewater. The solutions were analysed for major and trace elements and stable O/H isotope compositions. These analyses are compared with analyses for conventional groundwater samples. Samples were taken from a borehole array which crossed a prominent east-west trending fault, with a northerly downthrow of c.48 m. Comparisons are made between pore- and ground- water samples from each side of the fault, and from the fault zone itself. Sulphate concentrations are greatly increased in porewaters from the fault zone in comparison with sulphate concentrations in porewaters remote from the fault. The concentrations of porewater cations are related to pH, which in turn can be related to sulphate concentrations, probably controlled by sulphide oxidation. Cation concentrations are controlled mainly by carbonate dissolution and cation exchange reactions, largely dependent upon pH. Porewater concentrations of Cl and Br increase downwards but
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Metcalfe, R;
Ross, C A.M.;
Cave, M R;
Green, K A;
Reeder, S;
Entwisle, D C
[1]
- British Geological Survey, Keyworth (United Kingdom)
Citation Formats
Metcalfe, R, Ross, C A.M., Cave, M R, Green, K A, Reeder, S, and Entwisle, D C.
Porewater and groundwater geochemistry at the Down Ampney fault research site.
United Kingdom: N. p.,
1990.
Web.
Metcalfe, R, Ross, C A.M., Cave, M R, Green, K A, Reeder, S, & Entwisle, D C.
Porewater and groundwater geochemistry at the Down Ampney fault research site.
United Kingdom.
Metcalfe, R, Ross, C A.M., Cave, M R, Green, K A, Reeder, S, and Entwisle, D C.
1990.
"Porewater and groundwater geochemistry at the Down Ampney fault research site."
United Kingdom.
@misc{etde_10128766,
title = {Porewater and groundwater geochemistry at the Down Ampney fault research site}
author = {Metcalfe, R, Ross, C A.M., Cave, M R, Green, K A, Reeder, S, and Entwisle, D C}
abstractNote = {A Jurassic sequence of mudrocks, siltstones and limestones, at Down Ampney, Gloucestershire, was investigated. The aim was to evaluate the importance of faults in mudrocks as conduits for direct groundwater flow, and the influence of such faults on solute transport. Chemical analysis of porewaters and groundwaters are reported. Porewaters were obtained for analysis by squeezing mudrock core samples, yielding 18.1-34.5% of the total porewater. The solutions were analysed for major and trace elements and stable O/H isotope compositions. These analyses are compared with analyses for conventional groundwater samples. Samples were taken from a borehole array which crossed a prominent east-west trending fault, with a northerly downthrow of c.48 m. Comparisons are made between pore- and ground- water samples from each side of the fault, and from the fault zone itself. Sulphate concentrations are greatly increased in porewaters from the fault zone in comparison with sulphate concentrations in porewaters remote from the fault. The concentrations of porewater cations are related to pH, which in turn can be related to sulphate concentrations, probably controlled by sulphide oxidation. Cation concentrations are controlled mainly by carbonate dissolution and cation exchange reactions, largely dependent upon pH. Porewater concentrations of Cl and Br increase downwards but away from the fault zones the concentration gradients with depth are twice those in the vicinity of the fault. This suggests that meteoric waters are conducted by the fault, although they also penetrate downwards throughout the area. Groundwater compositions bear no simple relationship to porewater compositions, except in the case of sulphate. In the fault zone this is invariably more dilute in groundwaters than in porewaters. (author).}
place = {United Kingdom}
year = {1990}
month = {Dec}
}
title = {Porewater and groundwater geochemistry at the Down Ampney fault research site}
author = {Metcalfe, R, Ross, C A.M., Cave, M R, Green, K A, Reeder, S, and Entwisle, D C}
abstractNote = {A Jurassic sequence of mudrocks, siltstones and limestones, at Down Ampney, Gloucestershire, was investigated. The aim was to evaluate the importance of faults in mudrocks as conduits for direct groundwater flow, and the influence of such faults on solute transport. Chemical analysis of porewaters and groundwaters are reported. Porewaters were obtained for analysis by squeezing mudrock core samples, yielding 18.1-34.5% of the total porewater. The solutions were analysed for major and trace elements and stable O/H isotope compositions. These analyses are compared with analyses for conventional groundwater samples. Samples were taken from a borehole array which crossed a prominent east-west trending fault, with a northerly downthrow of c.48 m. Comparisons are made between pore- and ground- water samples from each side of the fault, and from the fault zone itself. Sulphate concentrations are greatly increased in porewaters from the fault zone in comparison with sulphate concentrations in porewaters remote from the fault. The concentrations of porewater cations are related to pH, which in turn can be related to sulphate concentrations, probably controlled by sulphide oxidation. Cation concentrations are controlled mainly by carbonate dissolution and cation exchange reactions, largely dependent upon pH. Porewater concentrations of Cl and Br increase downwards but away from the fault zones the concentration gradients with depth are twice those in the vicinity of the fault. This suggests that meteoric waters are conducted by the fault, although they also penetrate downwards throughout the area. Groundwater compositions bear no simple relationship to porewater compositions, except in the case of sulphate. In the fault zone this is invariably more dilute in groundwaters than in porewaters. (author).}
place = {United Kingdom}
year = {1990}
month = {Dec}
}