Deep Earth Observatory and Laboratory for Life, Fluid Flow and Rock Processes T. C. Onstott, Princeton U. H. F. Wang, U. of Wisconsin-Madison Geoscience Executive Summary for Working Groups on Geobiology, Geochemistry, Geohydrology, Geomechanics, and Geophysics

Executive Summary Theme: Coupled Processes in the Earth at Depth Life at Depth Fluid Flow and Transport at Depth Rock Deformation at Depth Potential for Scientific and Engineering Innovation Education and Outreach

Executive Summary for Geobiology/Geochemistry/Geology Kesler, Phelps,Valley, Sherwood-Lollar, Slater, Bang, Ruiz, Duke, Ridley, Campbell and Onstott Evolution of Geochemical, Hydrological and Biological Interfaces in Heterogeneous Environment over Geological Time USGS Bull J (1991) Time2.0 b.y. Today Depth PHOTIC-RHIZO ZONE THERMO BIOZONE 120 o C HYDROTHERMAL ZONE

Process and Interface Evolution Characterization –Hydrothermal and Deformation History –Fracture formation, low temperature geochemical alteration and biofossilization. –Present hydrogeological system and microbial biozones. –Inferred rates of evolution. Experimentaion –Rates - fluid mixing and mass transport –Rates microbial and nonmicrobial activity –Rates of subsurface microbial evolution in changing environment

Infrastructure (surface and subsurface labs) Clean lab/uncompromised sample repository Unique Experimental facilities Long term instrumentation of borehole arrays for experiments New scientific drilling

Courtesy: URL at Atomic Energy of Canada Ltd Proposed New Approach: Develop a US laboratory and observatory underground, inside the earth. Much like surgery permits a physician to examine internal bones and organs recognized on X-rays or CAT scans, NUSL will be a fully instrumented, dedicated laboratory and observatory for scientists to examine Earth’s interior.

US has not had a basic science underground lab to study geologic processes

Coupled Processes in the Earth at Depth NUSL offers unique opportunity to study complex geologic processes in situ with 3-D access for continuous observations and controlled experiments in an exceptionally large volume and great depth. USGS Bull J (1991)

Fluid Flow and Transport Characterization of active flow system Characterization of fracture network Verification of well and tracer test models Recharge to deep groundwater system Colloidal and bacterial transport Paleohydrology Rationale: fluid flow influences resource recovery, water supply, contaminant transport and remediation

How do we upscale point (space,time) measurements in a complex geologic system to larger regional processes? Whole earth m Regional scale – 10 6 m Whole mine experiments m Stope, cavity scale m Tunnel, shaft scale Borehole, “laboratory” scale m Grain, sub-lab scale m

Permeability vs. Scale

(a) Sampling arrangement in the Stripa 3-D experiment showing placement of plastic sheets for tracer collection. (b) Tracer distribution in the test site. Arrows indicate positions of injection holes, solid circles indicate sheet with significant water flow, and rectangles indicate sheets where tracers were collected. [adapted from Abelin et al., 1987]

Fractures are Key to Many Processes Fluid Flow Rock Strength Heat Flow Chemical Transport Ore Formation Faults & Earthquakes Biosphere for deep life to colonize and pathways for nutrient transport. Mauna Loa fissure eruption, D.A. Clague

Understanding Fractures What is their 3-D geometry and evolution? What processes formed fractures? What are their fluid and mass transport properties? How do fractures influence occurrence and type of microbial life? How do they govern microbial remediation methods? Can we understand empirically observed scaling effects? Can we improve geophysical imaging of fractures? While fractures are discontinuities, understanding their role in geologic processes is a unifying theme.

State of Stress: How do point measurements relate to regional and global stress picture? Is crust at NUSL critically stressed as at sites in other stable, intraplate areas? Do critically-stressed faults dominate fluid flow? How does stress state affect stability of tunnels, shafts, wellbores, and large, room- sized excavations?

Permeable Fractures and Faults are Critically Stressed

Permeable faults/fractures are critically-stressed High permeability maintains hydrostatic pore pressure Hydrostatic pore pressure results in high crustal strength Hypothesis Linking Stress State to Permeability to Crustal Strength.

Local Stress Distribution Critical to Rock Engineering

INSTRUMENTATION and MINE MEASUREMENTS of DISPLACEMENTS are ESSENTIAL

Solid- & Fluid-Environment Interaction –Models of Fracture Development –Coupled Processes  THM  CB  THMCB 80 0 C120 0 C C 80 0 C

Coupled Thermal-Hydrologic-Mechanical- Chemical-Biological Experiment Opportunities Imperatives –Strong scale dependence –THMCB processes incompletely understood –The role of serendipity in scientific advance Approach –Run-of-Mine Experiments (HCB) –Experiments Concurrent with Excavation of the Detector Caverns (THM) –Purpose-Built Experiments (THMCB)  Large Block Tests  Mine-By and Drift Structure Tests  Geophysical Monitoring –Educational Opportunities

Potential for Scientific and Engineering Innovation New genetic materials and applications Analytical technique for geomicrobiology Natural resource recovery Drilling and excavation technology Novel uses of underground space Mine safety Subsurface imaging Environmental remediation

Closing Perspectives Geoscience discoveries have depended historically on new exposures of subsurface through civil works, e.g., William Smith’s The Map that Changed the World. Educational and outreach benefits include providing experiential appreciation of earth’s interior.