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| Titel |
Multi-isotope tracing of CO2 leakage and water-rock interaction in a natural CCS analogue. |
| VerfasserIn |
Wolfram Kloppmann, Vasiliki Gemeni, Julie Lions, Nikolaos Koukouzas, Pauline Humez, Charalampos Vasilatos, Romain Millot, Hélène Pauwels |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104816
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| Publikation (Nr.) |
 EGU/EGU2015-5638.pdf |
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| Zusammenfassung |
| Natural analogues of CO2 accumulation and, potentially, leakage, provide a highly valuable
opportunity to study (1) geochemical processes within a CO2-reservoir and the overlying
aquifers or aquicludes, i.e. gas-water-rock interactions, (2) geology and tightness of
reservoirs over geological timescales, (3) potential or real leakage pathways, (3) impact
of leakage on shallow groundwater resources quality, and (4) direct and indirect
geochemical indicators of gas leakage (Lions et al., 2014, Humez et al., 2014). The
Florina Basin in NW Macedonia, Greece, contains a deep CO2-rich aquifer within
a graben structure. The graben filling consists of highly heterogeneous Neogene
clastic sediments constituted by components from the adjacent massifs including
carbonates, schists, gneiss as well as some ultramafic volcanic rocks. Clay layers are
observed that isolate hydraulically the deep, partly artesian aquifer. Organic matter, in
form of lignite accumulations, is abundant in the Neogene series. The underlying
bedrocks are metamorphic carbonates and silicate rocks. The origin of the CO2
accumulation is controversial (deep, partially mantle-derived D’Allessandro et al., 2008 or
resulting from thermal decomposition of carbonates, Hatziyannis and Arvanitis, 2011).
Groundwaters have been sampled from springs and borewells over 3 years at different
depths. First results on major, minor and trace elements give evidence of water-rock
interaction, mainly with carbonates but also with ultramafic components but do not
indicate that CO2-seepage is the principal driver of those processes (Gemeni et al.,
submitted).
Here we present isotope data on a selection of groundwaters (δ2H , δ18O, δ13CTDIC,
87Sr/86Sr, δ11B, δ7Li). Stable isotopes of water indicate paleo-recharge for some of the
groundwaters, limited exchange with gaseous CO2 and, in one case, possibly thermal
exchange processes with silicates. Sr isotope ratios vary between marine ratios and
radiogenic values indicating interaction with carbonates and silicates. Both δ11B
and δ7Li show a very large range of variation and fairly good correlation, between
-29.7 ‰ and +24‰ vs. NBS951 for boron and -11‰ and +20.4‰ vs. L-SVEC
for lithium. The negative δ11B and δ7Li values are among the lowest reported in
literature for groundwaters, comparable only to values observed for boron in case of
geothermal fluids interaction with clay minerals (Pennisi et al., 2009) or in some
amphiboles (e.g. Gillis et al., 2003) or lithium in ultramafic rocks (Nishio et al.,
2004). Those variations reflect water-rock interaction with the silicate fraction of the
highly heterogeneous graben filling but no clear indication of enhanced reactions
due to CO2 intrusion has been found. The δ13C values of TDIC are also strongly
variable (-10.5 to +15 ‰ vs. PDB), reflecting biogenic inputs (e.g. from lignite
layers), dissolution of carbonates and, potentially, methanogenesis through CO2
reduction.
D’ Alessandro W., Bellomo S., Brusca L., Karakazanis S., Kyriakopoulos K., and Liotta
M. (2011) The impact on water quality of the high carbon dioxide contents of the
groundwater in the area of Florina (N. Greece), Advances in the Research of Aquatic
Environment. Springer.
Gillis K. M., Coogan L. A., and Chaussidon M. (2003) Volatile element (B, Cl, F)
behaviour in the roof of an axial magma chamber from the East Pacific Rise. Earth and
Planetary Science Letters 213, 447-462.
Hatziyannis G. and Arvanitits A. (2011) Natural analogues of CO2 leakage in Florina
area, N. Greece., 2nd CGS Europe Knowledge Sharing Workshop Natural Analogues, Maria
Laach, Germany, October 17-19, 2011, pp.
Humez P., Negrel P., Lagneau V., Lions J., Kloppmann W., Gal F., Millot R., Guerrot C.,
Flehoc C., Widory D., and Girard J. F. (2014) CO2-water-mineral reactions during CO2
leakage: Geochemical and isotopic monitoring of a CO2 injection field test. Chem. Geol. 368,
11-30.
Lions J., Humez P., Pauwels H., Kloppmann W., and Czernichowski-Lauriol I. (2014)
Tracking leakage from a natural CO2 reservoir (Montmiral, France) through the chemistry
and isotope signatures of shallow groundwater. Greenhouse Gases-Science and Technology 4,
225-243.
Pennisi M., Bianchini G., Kloppmann W., and Muti A. (2009) Chemical and isotopic (B,
Sr) composition of alluvial sediments as archive of a past hydrothermal outflow. Chem. Geol.
266, 123-134.
Gemeni V., Vasilatos C., Koukouzas N., Kanellopoulos C. (submitted) Factors controlling
the chemistry of the groundwater in a CO2 natural field: The case of Florina Basin, W.
Macedonia, Greece. Submitted to Appl. Geochem. |
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