Transcript Onstott_Wang_Geosciences_Summary_Sat_plenary

Deep Earth Observatory and Laboratory for
Life, Fluid Flow and Rock Processes
Geoscience Executive Summary for Working Groups
on Geobiology, Geochemistry, Geohydrology, Geomechanics,
and Geophysics
T. C. Onstott, Princeton U.
H. F. Wang, U. of Wisconsin-Madison
Executive Summary
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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
PHOTIC-RHIZO ZONE
THERMO BIOZONE
120oC
USGS Bull.
1857-J
(1991)
HYDROTHERMAL ZONE
2.0 b.y.
Time
Today
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
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.
Courtesy: URL at Atomic Energy of Canada Ltd
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. 1857-J
(1991)
Fluid Flow and Transport
Rationale: fluid flow influences resource recovery,
water supply, contaminant transport and remediation
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
How do we upscale point (space,time)
measurements in a complex geologic system
to larger regional processes?
Whole earth Regional scale –
Whole mine experiments Stope, cavity scale Tunnel, shaft scale -
107 m
106 m
104 m
102 m
101
Borehole, “laboratory” scale -
10-1 m
Grain, sub-lab scale -
10-3 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
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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
While fractures are discontinuities, understanding their
role in geologic processes is a unifying theme.
• 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?
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, roomsized excavations?
Permeable Fractures and Faults are
Critically Stressed
Hypothesis Linking Stress State to
Permeability to Crustal Strength.
•Permeable faults/fractures are
critically-stressed
•High permeability maintains
hydrostatic pore pressure
•Hydrostatic pore pressure results in
high 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
800C
50
Fracture aperture (m)
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40
1200C
1500C
30
20
10
0
800C
1200C
0
50
100
150
200
400
Time (h)
600
800
1000
Coupled Thermal-Hydrologic-MechanicalChemical-Biological Experiment Opportunities
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Imperatives
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Strong scale dependence
THMCB processes incompletely understood
The role of serendipity in scientific advance
Approach
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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
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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.