Cambridge MA, 9-10 July 2015

C-DEBI Basement Microbiology Workshop

Modeling of Massive Hydrothermal Flows between Basement Outcrops in the Volcanic Crust

R. Lauer, A. T. Fisher, D. M. Winslow University of California, Santa Cruz

Lauer et al. – Massive Hydrothermal Flows Basement Microbiology Workshop

modified from Fisher and Wheat (2010)

We need to know crustal properties and flow rates to predict water-rock-microbial interactions

Dorado outcrop (and surrounding region)

• Regional surveys in 2001/2002• 11 volcanic outcrops mapped• Seismic, heat flux, geochem

• 14,500 km2 (size of Connecticut)missing 1.4 GW!

Massive, low-T fluid flow…?

Lauer et al. – Massive Hydrothermal Flows Basement Microbiology Workshop

Regional conductive heat flow deficit indicates rates of heat and fluid flow…

…which must be ginormous** “…very large, simply enormous…” OED

1.0-1.4 GWEach outcrop:1,000–20,000 L/s

modified from Hutnak et al. (2008)

104

HFF = 10-35%

20 kmDorado outcrop

Tengosed outcrop

A “firehose” of low-temperature, hydrothermal discharge?

Accessing the subseafloor biosphere

without drilling…

AT26-18

Basement outcrops provide entry/exit points for hydrothermal fluids, solutes, heat

Lauer et al. – Massive Hydrothermal Flows Basement Microbiology Workshop

Three-dimensional models of massive, outcrop-to-outcrop circulation

Lauer et al. – Massive Hydrothermal Flows Basement Microbiology Workshop

20 km

sediment

aquifer

conductive crust

Outcrop(seamount)

Outcrop(seamount)

Lower boundary: lithospheric heating (~110 mW/m2)

Upper boundary (seafloor):constant T, P(z)

One example from many options for two-outcrop systems:

Three-dimensional models of massive, outcrop-to-outcrop circulation

Lauer et al. – Massive Hydrothermal Flows Basement Microbiology Workshop

Recharge:koutcrop = 10-8 m2

Discharge:koutcrop = 10-10 m2

Two small outcrops Two large outcrops

observations

observations

Three-dimensional models of massive, outcrop-to-outcrop circulation

Lauer et al. – Massive Hydrothermal Flows Basement Microbiology Workshop

Recharge:koutcrop = 10-8 m2

Discharge:koutcrop = 10-10 m2

Two small outcrops Two large outcrops

observations

observations

Bingo!

Thank you!Questions?

Lauer et al. – Massive Hydrothermal Flows Basement Microbiology Workshop