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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
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
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)
Hydrothermal
References:Drake et al. 2009 Lithos, Drake and Tullborg, 2009 Appl. GeochemDrake et al. 2012, GCA, 2013, GCAMaskenskaya et al., submitted x 2
Hydrothermal
Mathurin et al., in press GCA
-1000
-800
-600
-400
-200
0
0 200 400 600 800SO4
2- (mg/L)D
epth
Drake et al., 2013 GCALaaksoharju et al., 2009
Berger et al., 2013
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)
Redox front
O2
Redox zoneRedox zone
Stable reducingconditions
Oxidisingconditions in fractures
Can be detected examining redox sensitive minerals and elements
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
Low temperature calcite and pyrite
TRACE METAL INCORPORATION (CALCITE)
Drake et al., (2012, GCA)
Maskenskaya et al., submitted
Also fracture-zone scale variabilityDrake et al., (2013, Appl. Geochem.)
Sulphur isotopes in pyrite (SRB-related)
This study
Samples: Groundwater(δ34S, SO4, DOC, HCO3)
Pyrite (δ34S)0 - >900 m depth
Mathurin et al., (2012)
Drake et al., 2013, GCA
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
δ34Srim- δ34Scentre vs.SO4
Drake et al., 2013, GCA
ONGOING/FUTURE STUDIES:
1. TRACES OF METHANE-OXIDATION/METHANOGENESISDrake et al., in prep
Calcite (δ13C, δ18O)0 - >900 m depth
SIMS 10 µm in situ analysis+ToF-SIMS/GC-MS
Drake et al.,in press Appl. Geochem
-1000
-900
-800
-700
-600
-500
-400
-300
-200
-100
0
-130 -110 -90 -70 -50 -30 -10 10δ13C ‰ (PDB)
Dep
th (
m.a
.s.l.
)
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
-1000
-900
-800
-700
-600
-500
-400
-300
-200
-100
0
-130 -110 -90 -70 -50 -30 -10 10δ13C ‰ (PDB)
Dep
th (
m.a
.s.l.
)
Methanogenesis(up to c. +5 per mil)
Min: -125‰
Drake et al., in prep
Similar study from Forsmark
-700
-600
-500
-400
-300
-200
-100
0
-70 -60 -50 -40 -30 -20 -10 0 10 20
δ13C
Dep
th Not within range ofgroundwater (δ18O)
Within range ofgroundwater (δ18O)
Methanogenesis(to +12 per mil)
Anaerobic oxidation of methane
Stable isotope variation and trace element uptakein recent, <17y, precipitates at Äspö• Micro-variation of sulphur isotopes in pyrite
• Trace element uptake in calcite
PRECIPITATES ON BOREHOLE EQUIPMENT AT ÄSPÖ (-450 m)
Mathurin et al., ES&T (2012)Drake et al., in prep
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‰
TRACE METAL INCORPORATION INTO CALCITE
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
DMg
Laboratory DMe
This study
KA3385A-1
KA3105A-2
KA3105A-3
KA3105A-4
0.01
0.1
1
10
DFe
Laboratory DMe
This study
KA3385A-1KA3105A-2
KA3105A-3KA3105A-4
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
DSr
Laboratory DMe
This study
KA3385A-1KA3105A-2
KA3105A-3KA3105A-4
0
5
10
15
20
25
30
35
DMn
LaboratoryDMeThis study
KA3385A-1
KA3105A-2KA3105A-3
KA3105A-4
+Ba, LREEs(+Y, V)(not shown)
Drake et al., in prep
STABLE ISOTOPE VARIATION IN CALCITE
Drake et al., in review
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