Contribution of the paragenetic sequence of clay minerals to re-examination of the alteration zoning in the krafla geothermal system
(2021) In Minerals 11(9).- Abstract
This paper revisits the clay mineralogy of the “smectite” alteration zone in the Krafla geothermal field via the study of an exploratory well in which temperatures range from 40 °C to 215 °C. The clay alteration consists of several mineral assemblages superimposed in time and space, resulting from different stages of water-rock interaction. Trioctahedral clay minerals (chlorite, cor-rensite and smectite) are observed throughout the studied section. These minerals can form in nearly closed systems as replacements of groundmass minerals/glass after interactions with resi-dent and nearly stagnant fluids not far from chemical equilibrium (neutral to basic pH conditions) or from direct precipitation from geothermal fluids. They are locally... (More)
This paper revisits the clay mineralogy of the “smectite” alteration zone in the Krafla geothermal field via the study of an exploratory well in which temperatures range from 40 °C to 215 °C. The clay alteration consists of several mineral assemblages superimposed in time and space, resulting from different stages of water-rock interaction. Trioctahedral clay minerals (chlorite, cor-rensite and smectite) are observed throughout the studied section. These minerals can form in nearly closed systems as replacements of groundmass minerals/glass after interactions with resi-dent and nearly stagnant fluids not far from chemical equilibrium (neutral to basic pH conditions) or from direct precipitation from geothermal fluids. They are locally superimposed by Al clay phases (smectite, illite/smectite and kaolinite), which result from intense leaching of the host rocks due to their interaction with low pH fluids under strong W/R ratios. The absence of mineralogical zoning is explained by the fact that hydrothermal alteration is strongly dependent on very recent hydrodynamics. The current fluid circulation generates trioctahedral clays at depth that cannot be distinguished from pervasive earlier alteration. The only easily detectable signature of current activity and the most relevant signature for geothermal exploration is the presence of Al dioctahedral phases since it indicates leaching and intense hydrothermal activity.
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- author
- Escobedo, David ; Patrier, Patricia ; Beaufort, Daniel ; Gibert, Benoit ; Levy, Léa LU ; Findling, Nathaniel and Mortensen, Annette
- publishing date
- 2021-09
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Clay minerals, Geothermal systems, Hydrothermal alteration, Krafla, Paragenetic model
- in
- Minerals
- volume
- 11
- issue
- 9
- article number
- 935
- publisher
- MDPI AG
- external identifiers
-
- scopus:85113489310
- ISSN
- 2075-163X
- DOI
- 10.3390/min11090935
- language
- English
- LU publication?
- no
- additional info
- Funding Information: Acknowledgments: The authors thank the power company Landsvirkjun for providing access to core samples several times in very good conditions. L.L. thanks ÍSOR for the help with handling the samples and understanding their mineralogy, in particular Sigurdur Sveinn Jonsson. Christophe Nevado and Doriane Delmas are warmly thanked for the preparation of high-quality thin sections. This work was supported by a PhD grant from Paris Sciences et Lettres to Léa Lévy and the IMAGE FP7 EC and GEMex H2020 projects (grant agreements 608553 and 727550), as well as by a CNRS-INSU grant (TelluS program) attributed to the project AGERG. Fundings for travelling were provided by the PHC program JulesVerne, granted to Ecole Normale Supérieure and University of Iceland, by the Icelandic Centre for Research (Rannis) and the French Ministries of Foreign Affairs and International Development and of Education, Teaching and Research. The authors gratefully acknowledge also funding from the European Union (ERDF), ‘‘Region Nouvelle Aquitaine’’. Funding Information: Funding: This research was partly funded by TelluS-CESSUR (CNRS-INSU). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- id
- 223f5f5d-91c0-456d-a261-504b46106904
- date added to LUP
- 2021-12-14 11:54:18
- date last changed
- 2022-07-21 00:04:32
@article{223f5f5d-91c0-456d-a261-504b46106904,
abstract = {{<p>This paper revisits the clay mineralogy of the “smectite” alteration zone in the Krafla geothermal field via the study of an exploratory well in which temperatures range from 40 °C to 215 °C. The clay alteration consists of several mineral assemblages superimposed in time and space, resulting from different stages of water-rock interaction. Trioctahedral clay minerals (chlorite, cor-rensite and smectite) are observed throughout the studied section. These minerals can form in nearly closed systems as replacements of groundmass minerals/glass after interactions with resi-dent and nearly stagnant fluids not far from chemical equilibrium (neutral to basic pH conditions) or from direct precipitation from geothermal fluids. They are locally superimposed by Al clay phases (smectite, illite/smectite and kaolinite), which result from intense leaching of the host rocks due to their interaction with low pH fluids under strong W/R ratios. The absence of mineralogical zoning is explained by the fact that hydrothermal alteration is strongly dependent on very recent hydrodynamics. The current fluid circulation generates trioctahedral clays at depth that cannot be distinguished from pervasive earlier alteration. The only easily detectable signature of current activity and the most relevant signature for geothermal exploration is the presence of Al dioctahedral phases since it indicates leaching and intense hydrothermal activity.</p>}},
author = {{Escobedo, David and Patrier, Patricia and Beaufort, Daniel and Gibert, Benoit and Levy, Léa and Findling, Nathaniel and Mortensen, Annette}},
issn = {{2075-163X}},
keywords = {{Clay minerals; Geothermal systems; Hydrothermal alteration; Krafla; Paragenetic model}},
language = {{eng}},
number = {{9}},
publisher = {{MDPI AG}},
series = {{Minerals}},
title = {{Contribution of the paragenetic sequence of clay minerals to re-examination of the alteration zoning in the krafla geothermal system}},
url = {{http://dx.doi.org/10.3390/min11090935}},
doi = {{10.3390/min11090935}},
volume = {{11}},
year = {{2021}},
}