Geosciences in an Underground Laboratory:

EarthLab

W. M. RoggenthenSD School of Mines & Technology

EarthLab:A Subterranean Laboratory and Observatory to Study Microbial Life, Fluid Flow, and Rock Deformation

Brian McPherson, New Mexico Institute of Mining and TechnologyDerek Elsworth, Pennsylvania State UniversityCharles Fairhurst, University of MinnesotaStephen Kesler, University of MichiganTullis Onstott, Princeton UniversityWilliam Roggenthen, SDSMTHerb Wang, University of Wisconsin

http://www.earthlab.org

Requirements – what Geosciences need:

1. A large (~20+ km3) volume of rock with interesting geology.

2. Drill holes and underground workings in rocks reaching temperatures of 120°C - water-filled fracture systems.

3. Ability to introduce materials into holes, workings, or fractures to modify the geochemistry of the rock.

4. Existing geologic data and samples.

Homestake Mine, Lead, SD

•EarthLab:

• A “window” into the basement of North America

•Microbial Life at Depth

•Hydrologic Cycle

•Rock-Water Chemistry

•Rock Deformation and Fluid Flow

•Deep Seismic Observatory

Microbial Life at Depth

The Ultradeep Life and Biogeochemistry Observatory

Purpose:

to search for the limits of life

•what is living at depth?•how does it take advantage of its environment?•what is its metabolic rate/how does it grow?

Methods:

use closely spaced boreholes that:

• attain depths up to 5 km

• have bottom-hole temperatures of 110-120°C, the maximum known temperature for life

Homestake Mine, Lead, SD

~16,000 ft

Hydrologic Cycle

The Deep Flow and Paleoclimate Laboratory and Observatory

Purpose:

to search for continental paleoclimate recordsand document deep transport processes

Methods:

instrument a fracture zone extending from the surface to the maximum depth of the laboratory.

Deep Flow Hydrologic Experiments

will provide information on the movement of groundwater in the crust and its relationship to Earth’s changing climate.

The Induced Fracture and Deformation Processes Laboratory

Purpose:

to conduct extensive studies of three-dimensionalrock deformation in heterogeneous rock formations

Methods:

Instruments in boreholes will measure:

•Rock deformation associated with mining out a large cavity

•Creation of fractures using high-pressure fluid

•Deformation resulting from heating small volumes of rock

Data are critical to scaling-up models used to predict long-term stability of subsurface excavations.

Induced Fracture and Deformation

The Deep Seismic Observatory

Purpose:

To make the largest and best seismometer in the world.

Method:

•The laboratory will become the instrument.

•Will use a fully three-dimensional array consisting of at least 60 broadband seismometers in tunnels and boreholes.

Key Numbers for EarthLab

Anticipated total tunnel length: ~ 10 kmGreatest tunnel depth: ~ 2 - 2.5 kmnumber of instrumented boreholes: ~ 140total length of rock core to collect: ~ 15,000 m

Genetic materials - novel microorganisms

Analytical techniques for geomicrobiology

Environmental remediation

Subsurface imaging

Natural resource recovery