We proposed to determine the diffusion kinetics of Sm, Nd and other selected REE in garnet (Ce, Gd, Yb) and clinopyroxene (Ce, Yb), and also of Hf in garnet as functions of T, P and fO2. The diffusion experiments will be conducted by tracer isotope techniques, and the induced isotopic profiles will be analyzed primarily by depth profiling in an Ion probe (SIMS).If the budgetary constraints, the anisotropic diffusion tensor of clinopyroxene will be determined following established procedures, which should yield fundamental insight about the diffusion mechanism. The diffusion data will be applied to model the dynamic evolution of REE in igneous rocks, which are products of partial melting of the Earth's mantle, accounting for the kinetics of incorporation of the trace elements from the solids into the partial melt. The Hf diffusion data will be applied to the interpretation of the Hf isotopic data in the Precambrian granites and rhyolites in terms of the involvement of garnet in the source region.Theoretical formulation will be developed for the closure temperature of slowly diffusing trace components in minerals, and to relate their cooling ages to the cooling rates, and applied to the Sm-Nd and Lu-Hf decay systems in garnet.
