1. American Geophysical Union OS52B-04, 19 December 2014 San Francisco, CA American Geophysical Union OS52B-04, 19 December 2014 San Francisco, CA A Cross-hole, Multi-year Tracer Injection Experiment in the Volcanic Ocean Crust A. T. Fisher 1, N. Neira 2, C. G. Wheat 3, J. Clark 2, D. Winslow 1, K. Becker 4, C.-C. Hsieh 5, M. Rappé 5 1 Earth and Planetary Sciences Department and Center for Dark Energy Biosphere Investigations University of California, Santa Cruz 2 University of California, Santa Barbara 3 University of Mississippi 4 University of Miami, RSMAS 5 University of Hawaii

2. modified from Fisher and Wheat (2010) The upper oceanic crust is a hydro-thermo-chemo-bio reactor

3. The Hydrogeologic Architecture of Basaltic Oceanic Crust: Hydrogeology, Geochemistry, Microbiology Focus on active ridge-flank processes to resolve: Magnitude and nature (distribution, extent of channeling) of permeability in crustal fluid-rock systems, variations, scaling (temporal, spatial) Magnitude and nature (distribution, extent of channeling) of permeability in crustal fluid-rock systems, variations, scaling (temporal, spatial) Magnitudes and directions of driving forces, fluid fluxes, flow channeling, and associated solute, heat, and microbial transport and storage Magnitudes and directions of driving forces, fluid fluxes, flow channeling, and associated solute, heat, and microbial transport and storage Relations between fluid flow, compartmentalization, microbiological communities, seismic properties, alteration, and structure Relations between fluid flow, compartmentalization, microbiological communities, seismic properties, alteration, and structure Nature of distinct fluid reservoirs, fluid residence times and velocities, response to transient perturbations Nature of distinct fluid reservoirs, fluid residence times and velocities, response to transient perturbations Focus on active ridge-flank processes to resolve: Magnitude and nature (distribution, extent of channeling) of permeability in crustal fluid-rock systems, variations, scaling (temporal, spatial) Magnitude and nature (distribution, extent of channeling) of permeability in crustal fluid-rock systems, variations, scaling (temporal, spatial) Magnitudes and directions of driving forces, fluid fluxes, flow channeling, and associated solute, heat, and microbial transport and storage Magnitudes and directions of driving forces, fluid fluxes, flow channeling, and associated solute, heat, and microbial transport and storage Relations between fluid flow, compartmentalization, microbiological communities, seismic properties, alteration, and structure Relations between fluid flow, compartmentalization, microbiological communities, seismic properties, alteration, and structure Nature of distinct fluid reservoirs, fluid residence times and velocities, response to transient perturbations Nature of distinct fluid reservoirs, fluid residence times and velocities, response to transient perturbations

4. Scientific Ocean Drilling Experiments modified from Fisher et al. (2011a) IODP Expeditions 301 (2004) and 327 (2010), ROV/HOV expeditions (2004-14)

5. Subseafloor borehole observatories (CORKs) Seal reentry hole to prevent hydrologic contamination, allow return to pre-drilling P/T/Chemistry/MBIO conditions Seal reentry hole to prevent hydrologic contamination, allow return to pre-drilling P/T/Chemistry/MBIO conditions Allow access to the subseafloor environment over long times, without drillship Allow access to the subseafloor environment over long times, without drillship Permit passive monitoring, facilitate active testing Permit passive monitoring, facilitate active testing Isolate multiple depth intervals Isolate multiple depth intervals Sounds like a lot of work... It is! But it’s worth the effort… Hundreds of meters modified from Fisher et al. (2011b)

6. Setting up a Cross-hole Experiment New CORKs installed in Holes 1026B, 1301A/B during IODP Expedition 301 (2004) New CORKs installed in Holes 1026B, 1301A/B during IODP Expedition 301 (2004) New CORKs installed in Holes 1362A/B during IODP Expedition 327 (2010) New CORKs installed in Holes 1362A/B during IODP Expedition 327 (2010) CORK in Hole 1027C rehabilitated with on AT18-07 (2011) CORK in Hole 1027C rehabilitated with on AT18-07 (2011) New CORKs installed in Holes 1026B, 1301A/B during IODP Expedition 301 (2004) New CORKs installed in Holes 1026B, 1301A/B during IODP Expedition 301 (2004) New CORKs installed in Holes 1362A/B during IODP Expedition 327 (2010) New CORKs installed in Holes 1362A/B during IODP Expedition 327 (2010) CORK in Hole 1027C rehabilitated with on AT18-07 (2011) CORK in Hole 1027C rehabilitated with on AT18-07 (2011) PP PP Basement relief modified from Fisher et al. (2011a)

7. Tracer injected 2010 Monitor seafloor (2010-14) Monitor downhole (2010-14) Tracer: Sulfur Hexafluoride (SF 6 ) Injected ~23 M in 24 hr Injectate [SF 6 ] ~ 48 µM Detection limit ~ 1 pM (dilution factor = 5 x 10 7 ) Fisher et al. (2011b) First controlled measurement of water, solute velocity! Setting up a Cross-hole Experiment Inferred flow direction: N20E, based on geochem, heat flow, modeling

8. Tracer testing concepts modified from Fisher et al. (2011b)

9. Tracer Test Configuration and Operations Hole 1362B One depth interval Injection (2010) Wellhead OS (2011, 13, 14) Downhole OS (2014) Free flow ≥2011 1000 m Hole 1301A Hole 1362A Hole 1026B

10. Tracer Test Configuration and Operations Hole 1362B 1000 m Hole 1362A Hole 1026B Hole 1301A One depth interval Wellhead OS (2010, 11, 13, 14) Discharging CORK!

11. Tracer Test Configuration and Operations Hole 1362B 1000 m Hole 1362A Two depth intervals Wellhead OS (2011, 13, 14) Downhole OS (2014) Hole 1026B Hole 1301A

12. Tracer Test Configuration and Operations Hole 1362B 1000 m Hole 1362A Hole 1026B Hole 1301A One depth interval Wellhead OS (2010-11,13,14) Downhole OS (2014)

13. Tracer Recovery: Hole 1301A Hole 1301A (discharging) Hole 1362B Hole 1362A Hole 1026B 1000 m modified from Neira (2014) Expedition delayed (2012)

14. Tracer Recovery: Hole 1301A modified from Neira (2014) Expedition delayed (2012) SF 6 peak arrival ~1 m/day Long plume tail, low [SF 6 ]…

15. Tracer Recovery: Hole 1362B modified from Neira (2014) Hole 1301A (discharging) Hole 1362B Hole 1362A Hole 1026B 1000 m Raw Corrected Flowmeter attached, Valve opened, Wellhead sampler deployed Expedition delayed (2012)

16. Tracer Recovery: Hole 1362A modified from Neira (2014) Hole 1301A Hole 1362B Hole 1362A Hole 1026B 1000 m Valve opened (1362B), Wellhead sampler deployed Expedition delayed (2012)

17. Tracer Recovery: Hole 1026B modified from Neira (2014) Hole 1301A Hole 1362B Hole 1362A Hole 1026B 1000 m 2010-13Wellhead

18. Tracer Recovery: Hole 1026B modified from Neira (2014) 2010-13Wellhead

19. Tracer Recovery: Hole 1026B modified from Neira (2014) Hole 1301A Hole 1362B Hole 1362A Hole 1026B 1000 m 2010-13Wellhead SF 6 peak arrival ≥1 m/day

20. The first three-dimensional, coupled fluid-heat flow ridge-flank hydrothermal models Field data guide model design, constrain results (hydrogeological, thermal, chemical) Field data guide model design, constrain results (hydrogeological, thermal, chemical) Small outcrop vents 5-20 kg/s, 1-2 MW power Small outcrop vents 5-20 kg/s, 1-2 MW power No regional mining of crustal heat No regional mining of crustal heat Basement fluids at 65°C, highly altered Basement fluids at 65°C, highly altered modified from Winslow and Fisher (2014)

21. The first three-dimensional, coupled fluid-heat flow ridge-flank hydrothermal models Mixed convection and a hydrothermal siphon between outcrops… modified from Winslow and Fisher (2014)

22. t The first three-dimensional, coupled fluid-heat flow ridge-flank hydrothermal models Mixed convection and a hydrothermal siphon between outcrops… modified from Winslow and Fisher (2014) Specific discharge x 10 -8 (m/s) 00.40.81.21.6 Count 2,000 6,000 10,000 14,000 0.130.260.38 Specific discharge (m/yr) Flow rates in the upper ocean crust, between outcrops, are about 0.2 m/yr

23. What do different flow rates imply? Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Moreno and Tsang, 1994 Tsang et al., 1991

24. What do different flow rates imply? Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc.

25. What do different flow rates imply? Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc.

26. What do different flow rates imply? Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Tracer tests: v L ~350 m/yr Tracer tests: v L ~350 m/yr Thermal data/models: q ~0.2 m/yr Thermal data/models: q ~0.2 m/yr Effective porosity (fraction of rock with flowing fluid): Effective porosity (fraction of rock with flowing fluid): n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) n e = q/v L = (0.2)/350 ~ 0.0005 (0.05%) Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc. Implications: very heterogeneous flow system, low specific surface area available for reaction, most pores are dead ends, etc.

27. Preliminary Interpretations We can run tracer injection tests in the ocean crust! We can run tracer injection tests in the ocean crust! Dominant flow direction is N20E, as hypothesized. Dominant flow direction is N20E, as hypothesized. Dissolved gas tracer transport rate is ~1 m/day. Dissolved gas tracer transport rate is ~1 m/day. Effective porosity for tracer transport is small <<1%. Effective porosity for tracer transport is small <<1%. Upper crustal aquifer is highly heterogeneous Upper crustal aquifer is highly heterogeneous “most of the aquifer is not an aquifer” We can run tracer injection tests in the ocean crust! We can run tracer injection tests in the ocean crust! Dominant flow direction is N20E, as hypothesized. Dominant flow direction is N20E, as hypothesized. Dissolved gas tracer transport rate is ~1 m/day. Dissolved gas tracer transport rate is ~1 m/day. Effective porosity for tracer transport is small <<1%. Effective porosity for tracer transport is small <<1%. Upper crustal aquifer is highly heterogeneous Upper crustal aquifer is highly heterogeneous “most of the aquifer is not an aquifer”

28. Preliminary Interpretations More data and interpretations from 1000s of samples recovered (wellhead/downhole) in Summer 2014, ongoing/new modeling, links to microbiological analyses… More data and interpretations from 1000s of samples recovered (wellhead/downhole) in Summer 2014, ongoing/new modeling, links to microbiological analyses… Data to be analyzed from cross-hole pressure and temperature response, independent estimates of formation permeability… Data to be analyzed from cross-hole pressure and temperature response, independent estimates of formation permeability… We can run tracer injection tests in the ocean crust! We can run tracer injection tests in the ocean crust! Dominant flow direction is N20E, as hypothesized. Dominant flow direction is N20E, as hypothesized. Dissolved gas tracer transport rate is ~1 m/day. Dissolved gas tracer transport rate is ~1 m/day. Effective porosity for tracer transport is small <<1%. Effective porosity for tracer transport is small <<1%. Upper crustal aquifer is highly heterogeneous Upper crustal aquifer is highly heterogeneous “most of the aquifer is not an aquifer” We can run tracer injection tests in the ocean crust! We can run tracer injection tests in the ocean crust! Dominant flow direction is N20E, as hypothesized. Dominant flow direction is N20E, as hypothesized. Dissolved gas tracer transport rate is ~1 m/day. Dissolved gas tracer transport rate is ~1 m/day. Effective porosity for tracer transport is small <<1%. Effective porosity for tracer transport is small <<1%. Upper crustal aquifer is highly heterogeneous Upper crustal aquifer is highly heterogeneous “most of the aquifer is not an aquifer”

29. Acknowledgements J. Cowen, E. Davis, K. Edwards, C. Gable, S. Hulme, G. Iturrino, M. Hutnak, W. Kirkwood, T. Pettigrew, V. Spiess, P. Stauffer, T. Tsuji, T. Urabe, H. Villinger, L. Zühlsdorff, and many others… Collaboration, advice, encouragement: Funding, leadership, trust: Planning, field support: IOs for ODP and IODP, crews and technicians of: J. Resolution, Atlantis, Thompson, Alvin, Jason, ROPOS… Thank you!

30. Questions? modified from Fisher (2005) Thank you!