Workshop Report - Ridge 2000 Program

Research over the past few years has provided a definition
of how small parts of the system work. However. major advances
in geophysical and geochemical techniques now allow us to
envision a coordinated. long-term program on a global scale
which will provide an integrated understanding of the processes
of crustal accretion.
Critical Problems
In order to understand the processes that transform mantle
melt into oceanic crust and the role of crustal magma chambers.
there are eight critical problems that must be addressed:
1. What is the global distribution of magma chambers along
oceanic ridges. and how does this distribution correlate with
tectonic segmentation. spreading rate. and mantle temperature?
2. What are the variations in the size. shape and physical
properties of ridge crest magma chambers?
3. What are the internal dynamics of magma chambers?
4. How are the magma chambers cooled?
5. What is the spacing of input of magma from the mantle
and output through eruption at the seafloor?
6. What is the temporal variability of magmatic processes?
7. What are the relationships among magmatism. tectonism
and hydrothermal activity?
8. Is the ophiolite model a valid structural analogue for
oceanic crust?
In order to address these problems several different
physical processes must be studied Isee Figure 1):
Magma formation and transport affects the composition of the
mantle melt and the temporal and spatial supply of magma to the
crust.
Magma differentiation and crystallization modifies the
magmas delivered from the upper mantle before they solidify to
form oceanic crust.
Hydrothermal circulation and conductive cooling transfer
heat out of the magma chamber and control its crystallization
history.
Volcanism delivers magma and heat to the sea floor.
Tectonism causes faulting and fissuring that control the
morphology of the spreading center and the locus and style of
volcanism.
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