Workshop Report - Ridge 2000 Program

o Laboratory experiments must test and generate thermodynamic
and kinetic data for mineral reactions at elevated
temperatures, pressures, and for varying salinity (0.5 to 2
times that of seawater). Near-supercritical conditions should
be emphasized. These experiments must address such issues as
aqueous speciation (inorganic and organic), solid-solution
relations for key alteration phases such as feldspar, chlorite,
and epidote, and fluid-mineral trace element distributions.
Analytical techniques must be developed to obtain more accurate
measurements of trace element and isotopic systematics of
hydrothermal alteration products. Ion and proton microprobe
techniques are expected to be especially useful.
o Numerical techniques and supporting data are required
to permit the modeling in three dimensions of fluid flow in
inhomogeneous ocean crustal rocks. Explicit account must be
made of the temporal and spatial distributions of primary and
secondary permeability (on macro to micro scales) and
pressure-volume-temperature composition properties of fluids.
The effect of different and variable heat transfer mechanisms
must also be included.
o Physical and chemical models of subseafloor hydrothermal
processes must be coupled to include the interconnectedness
of chemical and physical controls on fluid
circulation.
o Techniques must be developed to permit dating of
fluids, igneous materials, and hydrothermal products. These
techniques must make use of absolute and relative dating schemes
and permit timing of events on scales of 1 to 1.000,000 years.
Many of the measurement capabilities required to characterize
seafloor hydrothermal systems need to be improved and
refined.
o Precise and routine positioning on the seafloor is
essential for establishing spatial and temporal relationships.
o Instruments for geophysical measurements and experiments,
including seismic, controlled source electromagnetic,
and passive acoustic, need to be optimized for characterizing
the relevant spatial scales. The high data rates involved
require rapid incorporation of evolving technologies for
instrument control and data storage. Accurate and innovative
permeability measurements in crustal rocks and sediments are
also essential. Remotely operated vehicles (ROV's) should
be developed into powerful tools for mapping, sampling, and
experimental servicing.
o Improved water sampling equipment is needed for use at
high temperature vents and in boreholes. These need to be
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