Using secondary minerals and hydrochemistry to trace geochemical processes in the deep subsurface
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Transcript of Using secondary minerals and hydrochemistry to trace geochemical processes in the deep subsurface
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Using secondary minerals and hydrochemistry to
trace geochemical processes in the deep subsurface
Henrik DrakeLinnaeus 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
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Billion years of history
Present Groundwaters
Presently active bacteriaSRB, IRB etc
Deep Saline Glacial Marine Meteoric>~500ka 14ka 4-8ka present recharge
Past activity?Salinity?Redox?
?
Hydrothermal history Possible Quaternary
Start of mix with brine at 10 Ma
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Methodology
Microscope/SEMFluid inclusionsTrace elementsBiomarkersGeochronologyFracture orientationsIsotopes
Drake et al., 2012, GCAMaskenskaya et al., submitted
Drake and Tullborg, 2009, AGDrake et al., in press, AG
Mathurin et al., ES&T (2012)
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Hydrothermal
References:Drake et al. 2009 Lithos, Drake and Tullborg, 2009 Appl. GeochemDrake et al. 2012, GCA, 2013, GCAMaskenskaya et al., submitted x 2
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Hydrothermal
Mathurin et al., in press GCA
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Drake et al., 2013 GCALaaksoharju et al., 2009
Berger et al., 2013
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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)
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Redox front
O2
Redox zoneRedox zone
Stable reducingconditions
Oxidisingconditions in fractures
Can be detected examining redox sensitive minerals and elements
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Oxides
Drake et al., 2009, Appl.Geochem
CeIII CeIV
Drake et al., 2009 Appl.Geochem
Yu et al., in prep
Drake et al., in prep
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Low temperature calcite and pyrite
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TRACE METAL INCORPORATION (CALCITE)
Drake et al., (2012, GCA)
Maskenskaya et al., submitted
Also fracture-zone scale variabilityDrake et al., (2013, Appl. Geochem.)
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Sulphur isotopes in pyrite (SRB-related)
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This study
Samples: Groundwater(δ34S, SO4, DOC, HCO3)
Pyrite (δ34S)0 - >900 m depth
Mathurin et al., (2012)
Drake et al., 2013, GCA
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Pyrite• intra-crystal δ34S pattern
Increase with growth
Drake et al., 2013, GCA
•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
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δ34Srim- δ34Scentre vs.SO4
Drake et al., 2013, GCA
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ONGOING/FUTURE STUDIES:
1. TRACES OF METHANE-OXIDATION/METHANOGENESISDrake et al., in prep
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Calcite (δ13C, δ18O)0 - >900 m depth
SIMS 10 µm in situ analysis+ToF-SIMS/GC-MS
Drake et al.,in press Appl. Geochem
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Methanogenesis(up to c. +5 per mil)
Small organic influence
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)
Min: -125‰
Drake et al., in prep
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Methanogenesis(up to c. +5 per mil)
Min: -125‰
Drake et al., in prep
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Similar study from Forsmark
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Within range ofgroundwater (δ18O)
Methanogenesis(to +12 per mil)
Anaerobic oxidation of methane
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Stable isotope variation and trace element uptakein recent, <17y, precipitates at Äspö• Micro-variation of sulphur isotopes in pyrite
• Trace element uptake in calcite
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PRECIPITATES ON BOREHOLE EQUIPMENT AT ÄSPÖ (-450 m)
Mathurin et al., ES&T (2012)Drake et al., in prep
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MICRO-SCALE S-ISOTOPE VARIATION
Drake et al., in review
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‰
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TRACE METAL INCORPORATION INTO CALCITE
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DMg
Laboratory DMe
This study
KA3385A-1
KA3105A-2
KA3105A-3
KA3105A-4
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Laboratory DMe
This study
KA3385A-1KA3105A-2
KA3105A-3KA3105A-4
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Laboratory DMe
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KA3385A-1
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+Ba, LREEs(+Y, V)(not shown)
Drake et al., in prep
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STABLE ISOTOPE VARIATION IN CALCITE
Drake et al., in review
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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!
δ13Cδ34S