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

Billion years of history Present Groundwaters Presently active bacteria SRB, 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/SEM Fluid inclusions Trace elements Biomarkers Geochronology Fracture orientations Isotopes Drake et al., 2012, GCA Maskenskaya et al., submitted Drake and Tullborg, 2009, AG Drake et al., in press, AG Mathurin et al., ES&T (2012)

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

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

Low temperature minerals Recent past conditions (0-10 Ma = minerals, and groundwater Ma), 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 Can be detected examining redox sensitive minerals and elements

Oxides Drake et al., 2009, Appl.Geochem Ce III Ce IV 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 variability Drake et al., (2013, Appl. Geochem.)

Sulphur isotopes in pyrite (SRB-related)

This study Samples: Groundwater (δ 34 S, SO 4, DOC, HCO 3 ) Pyrite (δ 34 S) 0 - >900 m depth Mathurin et al., (2012) Drake et al., 2013, GCA

Pyrite intra-crystal δ 34 S 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, m

δ 34 S rim - δ 34 S centre vs.SO 4 Drake et al., 2013, GCA

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

Calcite (δ 13 C, δ 18 O) 0 - >900 m depth SIMS 10 µm in situ analysis +ToF-SIMS/GC-MS Drake et al.,in press Appl. Geochem

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

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

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

Stable isotope variation and trace element uptake in 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 δ 34 S sulphate +18 to +28‰ δ 34 S sulphide -29 to -1‰ Iron isotopes to be added, First SIMS results of fracture- coating pyrite δ 56 Fe -0.9 to +2.8‰

TRACE METAL INCORPORATION INTO CALCITE +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 δ 13 C calcite reported (-125‰) Largest δ 13 C calcite range within a single crystal (109‰) Largest range of δ 13 C calcite from single location (129‰) Largest δ 34 S pyrite range from single location (141‰; Drake et al., 2013, GCA) Thank you! δ 13 Cδ 34 S