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Using secondary minerals and hydrochemistry to trace geochemical processes in the deep subsurface

Using secondary minerals and hydrochemistry to trace geochemical processes in the deep subsurface. Henrik Drake Linnaeus University, Sweden

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Using secondary minerals and hydrochemistry to trace geochemical processes in the deep subsurface

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  1. Using secondary minerals and hydrochemistry to trace geochemical processes in the deep subsurface Henrik Drake Linnaeus University, Sweden Co-workers: LnU/SKB: Mats Åström, Olga Maskenskaya, Changxun Yu, Frederic Mathurin, Tobias Berger, Linda Alakangas, Birgitta Kalinowski, Ignasi Puigdomenech, Elsewhere: Eva-Lena Tullborg, Johan Hogmalm, Martin Whitehouse, Christine Heim, Magnus Ivarsson, Bill Wallin, Curt Broman, Thomas Zack, etc etc

  2. Billion years of history Present Groundwaters Deep Saline Glacial Marine Meteoric >~500ka 14ka 4-8ka present recharge Start of mix with brine at 10 Ma Presently active bacteria SRB, IRB etc ? Past activity? Salinity? Redox? Hydrothermal history Possible Quaternary

  3. Methodology Microscope/SEM Fluid inclusions Trace elements Biomarkers Geochronology Fracture orientations Isotopes Drake and Tullborg, 2009, AG Drake et al., in press, AG Mathurin et al., ES&T (2012) Drake et al., 2012, GCA Maskenskaya et al., submitted

  4. Hydrothermal References: Drake et al. 2009 Lithos, Drake and Tullborg, 2009 Appl. Geochem Drake et al. 2012, GCA, 2013, GCA Maskenskaya et al., submitted x 2

  5. Hydrothermal Berger et al., 2013 Drake et al., 2013 GCA Laaksoharju et al., 2009 Mathurin et al., in press GCA

  6. Low temperature minerals • Recent past conditions (0-10 Ma = minerals, and groundwater 0-0.5 Ma), 0-1000 m • Near-surface redox front • Fresh/saline interface and • Trace element variation/Trace element uptake into calcite • Activity of bacteria • Sulphate reducers • Methanogens • Methane oxidation • (Iron-reducers) • Pre-drilling, undisturbed conditions (minerals)

  7. Redox front Can be detected examining redox sensitive minerals and elements

  8. CeIII CeIV Oxides Drake et al., in prep Yu et al., in prep Drake et al., 2009, Appl.Geochem Drake et al., 2009 Appl.Geochem

  9. Low temperature calcite and pyrite

  10. TRACE METAL INCORPORATION (CALCITE) Drake et al., (2012, GCA) Maskenskaya et al., submitted Also fracture-zone scale variability Drake et al., (2013, Appl. Geochem.)

  11. Sulphur isotopes in pyrite (SRB-related)

  12. This study Drake et al., 2013, GCA Samples: Groundwater (δ34S, SO4, DOC, HCO3) Pyrite (δ34S) 0 - >900 m depth Mathurin et al., (2012)

  13. Pyrite • huge variations across individual crystals (-32 to +73‰) • extreme minimum (-50‰) and • maximum (+91‰) values. • =>141‰ range! • SRB activity at all depths analysed, 0-900 m • intra-crystal δ34S pattern • Increase with growth Drake et al., 2013, GCA

  14. δ34Srim- δ34Scentre vs.SO4 Drake et al., 2013, GCA

  15. ONGOING/FUTURE STUDIES:1. TRACES OF METHANE-OXIDATION/METHANOGENESISDrake et al., in prep

  16. Calcite (δ13C, δ18O) 0 - >900 m depth Drake et al.,in press Appl. Geochem SIMS10 µm in situ analysis +ToF-SIMS/GC-MS

  17. Methanogenesis (up to c. +5 per mil) Small organic influence Min: -125‰ Influence of organic C, e.g. from plants Anaerobic oxidation of methane (biomarkers are SRB- specific of high AOM-specificity, ToF-SIMS+GC/MS data) Drake et al., in prep

  18. Methanogenesis (up to c. +5 per mil) Min: -125‰ Drake et al., in prep

  19. Similar study from Forsmark Methanogenesis (to +12 per mil) Anaerobic oxidation of methane

  20. Stable isotope variation and trace element uptakein recent, <17y, precipitates at Äspö • Micro-variation of sulphur isotopes in pyrite • Trace element uptake in calcite

  21. PRECIPITATES ON BOREHOLE EQUIPMENT AT ÄSPÖ (-450 m) Mathurin et al., ES&T (2012) Drake et al., in prep

  22. MICRO-SCALE S-ISOTOPE VARIATION δ34Ssulphate +18 to +28‰ δ34Ssulphide -29 to -1‰ Iron isotopes to be added, First SIMS results of fracture- coating pyrite δ56Fe -0.9 to +2.8‰ Drake et al., in review

  23. TRACE METAL INCORPORATION INTO CALCITE +Ba, LREEs (+Y, V) (not shown) Drake et al., in prep

  24. STABLE ISOTOPE VARIATION IN CALCITE Drake et al., in review

  25. Finally,this area has • Most depleted δ13Ccalcite reported (-125‰) • Largest δ13Ccalcite range within a single crystal (109‰) • Largest range of δ13Ccalcite from single location (129‰) • Largest δ34Spyrite range from single location (141‰; Drake et al., 2013, GCA) • Thank you! δ34S δ13C

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