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NSF funded research project to examine deep crystalline basement flow systems in extensional terrains

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Fractures in granitic basement rocks exposed on the south side of Truth or Consequences, NM. This particular outcrop averages 53 fractures/m, which is unusually high. Most outcrops in the nearby Mud Springs Mountains have 2-10 fractures/m.

Rio Grande rift
— November 15, 2018

A newly funded NSF research project will study fluid mobility in cystalline rocks that are deep within the earth's crust. The research is being conducted by Jesus Gomez-Velez (Vanderbilt, formerly at NMT), Mark Person (NMT), and Shari Kelley (NMBGMR).

Typically, hydrogeologists view the crystalline basement rocks as impermeable. On the other hand, geothermal explorationists acknowledge that discrete fault zones within basement rocks can be permeable, but pay little attention to the source of the fluids feeding them. This study offers a compelling paradigm in which the crystalline basement in tectonically active regions can have a relatively high bulk permeability, serving as a major conveyor for water, solutes, and energy. Using the Rio Grande rift as a test bed, this project will combine geophysical (electromagnetic), geochemical, and field observations with advanced numerical models to explore the flow and transport characteristics of these deep hydrologic systems to unprecedented depths (~10 km). The outcomes and understanding gained with this effort could help quantify the volumes, salinity, residence times, and genesis of brackish water within deep aquifers in the western USA -- an unconventional resource with the potential to offset the ever-increasing deficit of water and energy in arid environments.

One goal of this project is to quantify the orientation, density, connectivity, and continuity of fractures in Proterozoic basement outcrops and cores in central and southern New Mexico (see photograph).