DOI: 10.7291/d1g67p
title: Numerical simulation of cool hydrothermal processes in the upper volcanic crust beneath a marine sediment pond: North Pond, North Atlantic Ocean

description: Low temperature hydrothermal systems hosted in the volcanic oceanic crust
 are responsible for ~20% of Earth's global heat loss. Marine sediment
 ponds comprise an important type-setting on young ridge flanks where
 hydrothermal circulation advectively extracts lithospheric heat, but the
 nature of coupled fluid-heat transport in these settings remains poorly
 understood. Here we present coupled (fluid-heat) numerical simulations of
 ocean crustal hydrogeology in and below North Pond, a sediment pond on ~8
 Ma seafloor of the North Atlantic Ocean. Two- and three-dimensional
 simulations show that advective transport beneath North Pond is complex
 and time-varying, with multiple spatial and temporal scales, consistent
 with seafloor and borehole observations. A unidirectional, single-pass
 flow system is neither favored nor needed to match the spatial
 distribution of seafloor heat flux through North Pond sediments. When the
 permeability of the crustal aquifer is relatively high (10-10 to 10-9 m2),
 simulations can replicate much of the observed variability and suppression
 of seafloor heat flux, and can explain basement overpressures and
 transient perturbations in pressure and temperature in the upper volcanic
 crust. Simulation results can also help explain heterogeneity in pore
 fluid chemistry and microbiology in the crust. Although driven by the same
 physical processes, the dynamics of hydrothermal circulation below North
 Pond are different from those seen on "discharge-dominated"
 ridge flanks, where the permeability and exposed area of isolated basement
 outcrops control the extent of regional heat extraction.
description: These data are input files for the numerical simulation code
 Finite Element Heat and Mass Transfer Code (FEHM; https://fehm.lanl.gov/).
 This dataset complements the publication titled "Numerical Simulation
 of Cool Hydrothermal Processes in the Upper Volcanic Crust Beneath a
 Marine Sediment Pond: North Pond, North Atlantic Ocean" published in
 the Journal of Geophysical Research: Solid Earth. The data here are model
 input files for the numerical code Finite Element Heat and Mass Transfer
 Code (FEHM) for the simulation of coupled fluxes of fluid and heat beneath
 the sedimented pond, North Pond in the North Atlantic Ocean. These files
 represent the characteristic simulation of permeability for each of the
 resulting aquifer thicknesses simulated 100, 300, 600, and
 1000m.
description: The following zipped file contains input files for FEHM
 (https://fehm.lanl.gov) numerical model. Please visit
 https://github.com/lanl/FEHM for buildFile and source code.
 The file structure is as follows:   
 |-2D<br>    |---aq300<br>    |-----p10<br>   
 |-----p11<br>    |-----p9<br>    |---aq600<br>   
 |-----p10<br>    |-----p11<br>    |-----p9<br>   
 |-3D<br>    |---aq100<br>    |-----p9<br>   
 |---aq1k<br>    |-----p10<br>    |---aq300<br>   
 |-----p10<br>    |-----p11<br>    |-----p12<br>   
 |-----p9<br>    |---aq600<br>    |-----p10<br>   
 |-----p11<br>    |-----p12<br>    |-----p9<br>   
 |---cond Where the uppermost directory contains either
 2- or 3-dimensional simulation geometries. The next subdirectory denotes
 the aquifer thickness simulated (aq1k = aquifer thickness 1000m, etc..)
 and one directory for a simulation with conductive physics. The next
 subdirectories denote the aquifer permeability simulated (p9 = aquifer
 permeability 10E-9). Within those directories are the
 following input files:<br> *.area - List of external nodes and
 cross-sectional areas in xyz.<br> *.cond - Thermal conductivity by
 node in xyz.<br> *.dat - Main FEHM control file. Used to specify
 files to read, boundary conditions, output type and frequency, and runtime
 parameters.<br> *.fehm - List of node numbers and coordinates,
 followed by element numbers and constituent nodes in each.<br>
 *.files - control file<br> *.flow - Flow file for use with FLOW
 macro, setting depth-dependent hydrostatic boundary condition at mesh
 top.<br> *.hflx - Heatflux file for use with HFLX macro, setting
 heatflow input at mesh bottom.<br> *.iap - Initial ambient pressure
 file, list of hydrostatic pressure by node based on ambient thermal
 conditions.<br> *.ini - Initial conditions used for
 simulation.<br> *.perm - Permeability by node in xyz.<br>
 *.ppor - Compressibility by node (scalar).<br> *.rock - Grain
 density, specific heat, and porosity by node.<br> *.stor - Node
 volume and mesh connectivity data for all nodes.<br> *.zone - List
 of zones and all constituent nodes. Includes materials and any additional
 specified zones (faults, conduits, etc.).<br> *_material.zone - List
 of material zones and all constituent nodes.<br> *_outside.zone -
 List of zones describing external surfaces of the mesh, and all
 constituent nodes. The format of all of these input
 files can be found in the FEHM user manual
 (http://www.lanl.gov/orgs/ees/fehm/docs/FEHM_UM_V3.3.0.pdf)<br>
 <br> Finally, file: "nist120-1800.out" is a lookup table
 for density, viscosity, enthalpy, and respective derivatives with respect
 to temperature and pressure for pure water at pressures 20-180 MPa and
 temperatures 0 - 1800ºC based on NIST STEAM tables
 (https://webbook.nist.gov/chemistry/fluid/). The data
 columns are as follows:<br> Column 1 = Pressure (MPa)<br>
 Column 2 = Temperature (ºC)<br> Column 3 = Density (g/m3)<br>
 Column 4 = ∆Density / ∆Pressure<br> Column 5 = ∆Density /
 ∆Temperature<br> Column 6 = Enthalpy / 1000<br> Column 7 = 
 ∆Enthalpy / ∆Pressure / 1000<br> Column 8 =  ∆Enthalpy /
 ∆Temperature / 1000<br> Column 9 =  Viscosity<br> Column 10 = 
 ∆Viscosity / ∆Pressure<br> Column 11 =  ∆Viscosity / ∆
 Temperature This file is symbolically linked to all the
 above directories as "run.wpi". FEHM will not run without this
 symbolic link.