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Fluids in the lower crust
1) In the Serre of Calabria (Italy), representing the deepest part of
an exposed Hercynian crust, fluid inclusion investigations have been
combined with analyses of the channel fluids in cordierite to
characterize the fluid composition of the lower crustal rocks during
the metamorphic evolution (Herms and Schenk 1992). Fluid inclusion
data enabled to constrain the petrologically deduced P-T path, even
for low P-T conditions where mineral reactions are not available,
while stable isotopes have been used to yield information about fluid
movements.
2) High-pressure granulites from the Uluguru Mts (Tanzania), which are
part of the Pan-African belt, represent an exceptional case where
fluid inclusion investigations enabled to record the entire fluid
evolution from the prograde to the retrograde stage. Fluid inclusion
work further indicated that in metapelites and metabasites the fluid
composition has been internally controlled by phase equilibria, while
a fluid influx was suggested for shear zones (Herms and Schenk
1998).
3) Fluid inclusion studies on subduction-related 2 Ga eclogites of the
Usagaran of Tanzania are in progress. Fluids in subduction zones are
of great importance with respect to the fact that fluids liberated
from the subducted slab are responsible for element recycling into the
mantle, for mantle metasomatism and melt generation.
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