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Isotopic evidence for microbial production and consumption of methane in the upper continental crust throughout the Phanerozoic eon
Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).ORCID-id: 0000-0001-7230-6509
Georg August Univ, Germany.
British Geol Survey, UK.
University of Gothenburg.
Vise andre og tillknytning
2017 (engelsk)Inngår i: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 470, s. 108-118Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Microorganisms produce and consume methane in terrestrial surface environments, sea sediments and, as indicated by recent discoveries, in fractured crystalline bedrock. These processes in the crystalline bedrock remain, however, unexplored both in terms of mechanisms and spatiotemporal distribution. Here we have studied these processes via a multi-method approach including microscale analysis of the stable isotope compositions of calcite and pyrite precipitated in bedrock fractures in the upper crust (down to 1.7 km) at three sites on the Baltic Shield. Microbial processes have caused an intriguing variability of the carbon isotopes in the calcites at all sites, with delta C-13 spanning as much as -93.1 parts per thousand (related to anaerobic oxidation of methane) to +36.5 parts per thousand (related to methanogenesis). Spatiotemporal coupling between the stable isotope measurements and radiometric age determinations (micro-scale dating using new high spatial methods: LA-ICP-MS U-Pb for calcite and Rb-Sr for calcite and co-genetic adularia) enabled unprecedented direct timing constraints of the microbial processes to several periods throughout the Phanerozoic eon, dating back to Devonian times. These events have featured variable fluid salinities and temperatures as shown by fluid inclusions in the calcite; dominantly 70-85 degrees C brines in the Paleozoic and lower temperatures (<50-62 degrees C) and salinities in the Mesozoic. Preserved organic compounds, including plant signatures, within the calcite crystals mark the influence of organic matter in descending surficial fluids on the microbial processes in the fracture system, thus linking processes in the deep and surficial biosphere. These findings substantially extend the recognized temporal and spatial range for production and consumption of methane within the upper continental crust. (C) 2017 Elsevier B.V. All rights reserved.

sted, utgiver, år, opplag, sider
Elsevier, 2017. Vol. 470, s. 108-118
Emneord [en]
anaerobic oxidation of methane, methanogenesis, calcite, carbon isotopes, crystalline crust, radiometric dating
HSV kategori
Forskningsprogram
Ekologi, Mikrobiologi
Identifikatorer
URN: urn:nbn:se:lnu:diva-66966DOI: 10.1016/j.epsl.2017.04.034ISI: 000402944600011Scopus ID: 2-s2.0-85019034992OAI: oai:DiVA.org:lnu-66966DiVA, id: diva2:1127780
Tilgjengelig fra: 2017-07-19 Laget: 2017-07-19 Sist oppdatert: 2020-11-06bibliografisk kontrollert
Inngår i avhandling
1. Constraining the timing of veins, faults and fractures in crystalline rocks by in situ Rb-Sr geochronology
Åpne denne publikasjonen i ny fane eller vindu >>Constraining the timing of veins, faults and fractures in crystalline rocks by in situ Rb-Sr geochronology
2020 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Precambrian cratons are continent cores archiving the oldest crustal histories on Earth. The crystalline basement of cratons is typically characterized by complex arrays of multiple fracture and fault generations hosting minerals formed by fluids flowing through fracture networks. Disentangling absolute chronologies of the various fracturing, faulting and fluid flow events have to date been difficult given the micro-scale mineral intergrowths and zonations, inhibiting conventional dating techniques. In the general lack of age constraints, deformation and mineralization mechanisms cannot be attributed to specific tectonic regimes, hampering reconstruction of local and regional events of fluid flow and mineral precipitation, and ultimately of the geological evolution of cratons. This thesis presents diverse studies utilizing the radiogenic decay of fracture, fault and shear zone mineral assemblages sampled from the crystalline basement of the Fennoscandian Shield, aiming at detecting episodic fracturing reactivation, mineralization and microbial processes throughout the craton history.

The analytical procedures involve, foremost, Rb-Sr geochronology, along with U-Pb and (U-Th)/He geochronology, stable isotope and trace element geochemistry, fluid inclusion thermometry and biomarkers. The in situ age determinations enabled 1) linking of greisen and distal veins to magmatic and post-magmatic fluid circulation, 2) slickenfibre growth to distinct faulting episodes, and 3) mineral precipitation in fractures, veins and shear zones to regionally extending deformation events across the Fennoscandian Shield. In addition, dating of mineralization related to deep fracture-hosted microbial life constrained the timing of such activity at several sites. The precipitation episodes stretch from Paleoproterozoic to Jurassic times with overgrowth generations separated in time by up to one billion years in single veins and even within individual crystals. The findings of the thesis demonstrate that the methodological protocol has potential to directly date a wide range of mineral assemblages in fractures, faults, veins and shear zones given that the isochron requirements are fulfilled. Fulfillment is ensured through detailed petrological and structural characterization followed by geochronological analysis and thorough data reduction allowing validation of isotopic data down to submicrometer level. The outcomes have implications for tectonic reconstructions at various scales, for the tracing of the deep ancient biosphere and for comprehending hydrothermal ore deposition, with direct societal relevance in the detection of ancient microbial activity and fracture reactivation at the candidate site for a spent nuclear fuel repository in Sweden.

sted, utgiver, år, opplag, sider
Växjö: Linnaeus University Press, 2020. s. 67
Serie
Linnaeus University Dissertations ; 397
Emneord
geochronology, brittle deformation, crustal fluids, mineral precipitation, ancient microbial activity, Precambrian craton, Scandinavia
HSV kategori
Forskningsprogram
Naturvetenskap
Identifikatorer
urn:nbn:se:lnu:diva-98778 (URN)978-91-89283-02-2 (ISBN)978-91-89283-03-9 (ISBN)
Disputas
2020-11-27, Lapis, Hus Vita, Kalmar, 09:00
Opponent
Veileder
Tilgjengelig fra: 2020-11-06 Laget: 2020-11-06 Sist oppdatert: 2024-02-29bibliografisk kontrollert

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