Projects
Sm-Nd
Thermochronology of Garnets in Metamorphic Rocks: A New Method and Tectonic
Applications
|
|
|
This project quantitatively investigates
cooling and exhumation rates of garnet bearing lower crustal rocks using a new thermochronological
method. This method permits determination of cooling rates from the age profile
or the difference between the core and bulk ages of a mineral by a single decay
system, the Sm-Nd system. We determine the Sm-Nd ages of central and rim segments
of garnet crystals by isotope dilution and thermal ionization mass
spectrometry. The ages are determined from small quantities of samples drilled
from the cores of defined dimensions. These data are then combined with
conventional thermobarometry based on ion exchange and mineral reactions to
constrain the exhumation history of the rocks above 500 °C.
We are experimenting with measurements of
143Nd/144Nd on small quantities of Nd (down to 1-2 ng) by measuring Nd as NdO+.
Preliminary measurements of exhumation rates on granulites from the Santa Lucia
range, California and Hercynian eclogites from the South Carpathians have been
unsuccessful, partly because of the fast exhumation rates experimented by these
rocks (i.e. they yielded identical core and rim ages within the analytical
error). We are now focusing on slowly cooled rocks from the
Personnel: Ducea, Jibamitra
Ganguly (Univ.
Publications:
·
Ducea, M.N.,
Ganguly, J.,