Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites
The Precambrian Egersund anorthosites exhibit a wide range of groundwater chemical composition (pH 5.40–9.93, Ca2+ 1.5–41 mg/L, Na+ 12.3–103 mg/L). They also exhibit an evolutionary trend, culminating in high pH, Na-rich, low-Ca groundwaters, that is broadly representative of Norwegian crystalline b...
Published in: | Geochimica et Cosmochimica Acta |
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ftuglasgow:oai:eprints.gla.ac.uk:76198 2023-05-15T15:05:00+02:00 Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites Banks, D. Frengstad, B. 2006-03-15 http://eprints.gla.ac.uk/76198/ unknown Banks, D. <http://eprints.gla.ac.uk/view/author/29509.html> and Frengstad, B. (2006) Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites. Geochimica et Cosmochimica Acta <http://eprints.gla.ac.uk/view/journal_volume/Geochimica_et_Cosmochimica_Acta.html>, 70(6), pp. 1337-1355. (doi:10.1016/j.gca.2005.11.025 <http://dx.doi.org/10.1016/j.gca.2005.11.025>) QD Chemistry QE Geology Articles PeerReviewed 2006 ftuglasgow https://doi.org/10.1016/j.gca.2005.11.025 2021-09-23T22:53:26Z The Precambrian Egersund anorthosites exhibit a wide range of groundwater chemical composition (pH 5.40–9.93, Ca2+ 1.5–41 mg/L, Na+ 12.3–103 mg/L). They also exhibit an evolutionary trend, culminating in high pH, Na-rich, low-Ca groundwaters, that is broadly representative of Norwegian crystalline bedrock aquifers in general. Simple PHREEQC modelling of monomineralic plagioclase–CO2–H2O systems demonstrates that the evolution of such waters can be explained solely by plagioclase weathering, coupled with calcite precipitation, without invoking cation exchange. Some degree of reaction in open CO2 systems seems necessary to generate the observed maximum solute concentrations, while subsequent system closure can be invoked to explain high observed pH values. Empirical data provide observations required or predicted by such a model: (i) the presence of secondary calcite in silicate aquifer systems, (ii) the buffering of pH at around 8.0–8.3 by calcite precipitation, (iii) significant soil gas CO2 concentrations (PCO2 > 10−2 atm) even in poorly vegetated sub-arctic catchments, and (iv) the eventual re-accumulation of calcium in highly evolved, high pH waters. Article in Journal/Newspaper Arctic University of Glasgow: Enlighten - Publications Arctic Geochimica et Cosmochimica Acta 70 6 1337 1355 |
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Open Polar |
collection |
University of Glasgow: Enlighten - Publications |
op_collection_id |
ftuglasgow |
language |
unknown |
topic |
QD Chemistry QE Geology |
spellingShingle |
QD Chemistry QE Geology Banks, D. Frengstad, B. Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites |
topic_facet |
QD Chemistry QE Geology |
description |
The Precambrian Egersund anorthosites exhibit a wide range of groundwater chemical composition (pH 5.40–9.93, Ca2+ 1.5–41 mg/L, Na+ 12.3–103 mg/L). They also exhibit an evolutionary trend, culminating in high pH, Na-rich, low-Ca groundwaters, that is broadly representative of Norwegian crystalline bedrock aquifers in general. Simple PHREEQC modelling of monomineralic plagioclase–CO2–H2O systems demonstrates that the evolution of such waters can be explained solely by plagioclase weathering, coupled with calcite precipitation, without invoking cation exchange. Some degree of reaction in open CO2 systems seems necessary to generate the observed maximum solute concentrations, while subsequent system closure can be invoked to explain high observed pH values. Empirical data provide observations required or predicted by such a model: (i) the presence of secondary calcite in silicate aquifer systems, (ii) the buffering of pH at around 8.0–8.3 by calcite precipitation, (iii) significant soil gas CO2 concentrations (PCO2 > 10−2 atm) even in poorly vegetated sub-arctic catchments, and (iv) the eventual re-accumulation of calcium in highly evolved, high pH waters. |
format |
Article in Journal/Newspaper |
author |
Banks, D. Frengstad, B. |
author_facet |
Banks, D. Frengstad, B. |
author_sort |
Banks, D. |
title |
Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites |
title_short |
Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites |
title_full |
Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites |
title_fullStr |
Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites |
title_full_unstemmed |
Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites |
title_sort |
evolution of groundwater chemical composition by plagioclase hydrolysis in norwegian anorthosites |
publishDate |
2006 |
url |
http://eprints.gla.ac.uk/76198/ |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_relation |
Banks, D. <http://eprints.gla.ac.uk/view/author/29509.html> and Frengstad, B. (2006) Evolution of groundwater chemical composition by plagioclase hydrolysis in Norwegian anorthosites. Geochimica et Cosmochimica Acta <http://eprints.gla.ac.uk/view/journal_volume/Geochimica_et_Cosmochimica_Acta.html>, 70(6), pp. 1337-1355. (doi:10.1016/j.gca.2005.11.025 <http://dx.doi.org/10.1016/j.gca.2005.11.025>) |
op_doi |
https://doi.org/10.1016/j.gca.2005.11.025 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
70 |
container_issue |
6 |
container_start_page |
1337 |
op_container_end_page |
1355 |
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1766336769515585536 |