Section Days abstract book 2010.indd - RUB Research School ...

NSE_04
COOLING AND ACCRETION OF THE LOWER
OCEANIC CRUST AT FAST SPREADING
MID-OCEAN RIDGES
Kathrin Faak,
Sumit Chakraborty and Laurence Coogan
Faculty of Geoscience, Institute for Geology, Mineralogy and Geophysics
Ruhr-Universität Bochum, 44780 Bochum, Germany
email: Kathrin.Faak@rub.de
The formation and cooling of new oceanic lithosphere continually resurfaces the surface of
two-thirds of Earth and is the principal mechanism of cooling of Earth's interior. The
formation of new ocean crust along the global mid-ocean ridge system involves the
emplacement of ~20 km 3 of magma per year. An intimately linked process is the circulation of
seawater through newly formed crust that extracts magmatic heat and produces hydrothermal
fluids enriched in base metals and nutrients that form massive sulfide deposits and feed
chemosynthetic ecosystems on the seafloor. Additionally these hydrothermal systems have a
profound influence on the composition of the oceans.
However the processes involved in crystallizing and cooling this magma to form the oceanic
crust are still poorly understood. At the moment two different models are discussed in the
literature to explain the formation of oceanic crust – the “Gabbro glacier” and the “Sheeted
sill” model, which predict different thermal evolution of the oceanic crust and different depth
of hydrothermal circulation.
We apply methods of geospeedometry to samples directly from the ocean floor to determine
cooling rates of the oceanic crust as a function of depth. This allows to check, which of the
models is in better conformity with the observations made in nature.