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| Titel |
Water-Rock Interactions in the Peridotite Aquifer of the Oman-UAE Ophiolite:
Strontium Isotopic Ratio and Geochemical Evolution of Groundwater |
| VerfasserIn |
Nicolas Bompard, Juerg Matter, Damon Teagle |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135050
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| Publikation (Nr.) |
 EGU/EGU2016-15847.pdf |
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| Zusammenfassung |
| The peridotite aquifer in Wadi Tayin, Sultanate of Oman, is a perfect example of natural
carbonation of ultramafic rocks. In situ mineral carbonation is considered the most safest and
permanent option of CO2 Capture and Sequestration (CCS). However, the process itself is yet
to be characterised and a better understanding of the mechanisms involved in natural mineral
carbonation is needed before geo-engineering it. We used the 87Sr/86Sr system to follow the
water-rock interactions along the groundwater flowpath in the peridotite aquifer and
to determine the sources of divalent cations (Mg2+, Ca2+) required for mineral
carbonation.
The Sr-isotope data of groundwater show that the aquifer rocks are the main source for
divalent cations (Mg2+, Ca2+ and Sr2+) and secondary carbonates are their main sink. The
groundwater 87Sr/86Sr ratio evolves with its pH: from 87Sr/86Sr = 0.7087 (n=3) to 0.7082
(n=8) between pH 7 and 8, and from 0.7086 (n=6) at pH 9 to 0.07075 (n=9) at pH 11.
This evolution seems to support a two-step model for the water-rock interactions
in the peridotite aquifer. From pH 7 to 8, secondary Ca-carbonate precipitation
buffers the pH rise resulting from peridotite serpentinisation. From pH 9 to 11,
peridotite serpentinisation drives the pH to alkaline condition. The change from a
Mg-rich to a Ca-rich groundwater at pH 9 seems to confirm the two-step model. |
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