Mathematical models of ridge crest hydrothermal systems: Basic state and recent advances
Robert P. Lowell, Ph.D.
Georgia Institute of Technology
Wednesday, June 9, 2004
Pacific Forum – 2:00 p.m.
Hydrothermal processes at ocean ridge crests involve a complex interplay between the dynamics of heat supply and the evolution of crustal permeability that results in a broad spectrum of issues to challenge hydrothermal modelers. Among these are: (1) the detailed relationships between heat supply and hydrothermal heat transfer, (2) the mechanisms controlling vent stability and long-term evolution of hydrothermal vents, including the relationship between focused and diffuse flow, (3) temporal variability related to magmatic and tectonic events, (4) boiling, phase separation and the evolution of vent chlorinity, and (5) the linkages among heat transfer, fluid flow, geochemical and biological processes in controlling character and evolution of vent fields. Here we use the single-pass model approach to show that the basic state of a black smoker vent field requires a conductive boundary layer no more than a few tens of meter thick above a magma chamber and a discharge zone with permeability between 10-13 and 10-11 m2. Long-term vent stability requires that the thin conductive boundary be maintained, probably by some combination of magma replenishment and crack propagation, and a broad recharge zone to prevent clogging by anhydrite. Event plumes may be driven by dike emplacement provided the dike locally increases the permeability by two orders of magnitude and provides a significant fraction of event plume heat.