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| Titel |
An integrated geochemical approach to microbial biosignatures from a subterranean deep biosphere |
| VerfasserIn |
Christine Heim, Jukka Lausmaa, Peter Sjövall, Jan Toporski, Thomas Dieing, Klaus Simon, Bent T. Hansen, Joachim Reitner  , Volker Thiel |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056153
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| Zusammenfassung |
| To track organic or inorganic biosignatures of an ancient deep biosphere, an analytical
approach combining complementary techniques of high lateral resolution was adopted. This
approach included polarization microscopy, time-of-flight secondary ion mass spectrometry
(ToF-SIMS), confocal Raman microscopy, and laser ablation inductively coupled
plasma mass spectrometry (LA-ICP-MS). This instrumental combination enabled a
reconstruction and integrated understanding of ancient environmental processes that
occurred within the continental deep biosphere, while leaving the integrity of the
studied structures virtually intact. Investigations were performed on a minute amount
of sample material, namely a 5 mm thick section (2x4 cm2) exhibiting fracture
fillings in a 1.8 Ga old diorite, obtained at -450 m depth in the Äspö Hard Rock
Laboratory.
The fracture mineral succession consists of fluorite and calcite phases and a thin
(20-100μm), amorphous layer, lining the boundary between the fluorite and the calcite
phases. Distinct accumulations of the amorphous material within cavities of the fluorite point
to biocorrosion. Analysis of the amorphous layer showed significant accumulations of Si, Al,
Mg, Fe, and light rare earth elements (LREE). In the same area, ToF-SIMS imaging revealed
numerous, partly functionalized organic ions, e.g. C2H6N+, C4H7+, C3H5O+, and C6H11+.
The presence of such functionalized organic compounds within the amorphous layer was
corroborated by extended Raman imaging showing bands characteristic for C-C, C-N, and
C-O bonds. According to its organic nature and the abundance of relatively unstable N- and
O- heterocompounds, the organic-rich amorphous layer was interpreted to represent
the remains of a biofilm that established much later than the initial cooling of the
Precambrian host rock. Indeed, δ13C, δ18O and 87Sr/86Sr isotope analyses of the
fracture minerals and the host rock pointed to an association of the fossil biofilm with
a Pleistocene fracture reactivation event, i.e., in the most recent geological past. |
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