Experimentally Determined Trace Element Partitioning between Rutile and Melt: Implications for Subduction Zone Processes

HR: 1340h
AN: V13A-1459 [Abstracts]
TI: Experimentally Determined Trace Element Partitioning between Rutile and Melt: Implications for Subduction Zone Processes
AU: Prowatke, S
EM: sprowatk@ix.urz.uni-heidelberg.de
AF: Dept of Mineralogy University of Heidelberg, Im Neuenheimer Feld 236, Heidelberg, 69120 Germany
AU: * Klemme, S
EM: sklemme@min.uni-heidelberg.de
AF: Dept of Mineralogy University of Heidelberg, Im Neuenheimer Feld 236, Heidelberg, 69120 Germany
AU: Hametner, K
EM: hametner@inorg.chem.ethz.ch
AF: Laboratorium f〉 Anorganische Chemie ETH Zuerich, ETH Hoenggerberg, Zuerich, 8093 Switzerland
AU: Guenther, D
EM: detlef.guenther@inorg.chem.ethz.ch
AF: Laboratorium f〉 Anorganische Chemie ETH Zuerich, ETH Hoenggerberg, Zuerich, 8093 Switzerland
AB: Mineral/melt trace element partition coefficients were determined experimentally for rutile (TiO$_{2}$) for a large number of trace elements (Zr, Hf, Nb, Ta, V, Co, Cu, Zn, Sr, REE, Cr, Sb, W, U, Th). Whilst the high field strength elements (Zr, Hf, Nb, Ta) are compatible in rutile, most other studied trace elements are incompatible (Co, Zn, Sr, Th, REE). In all experiments we found D$_{Ta}$ $>$ D$_{Nb}$, D$_{Hf}$ $>$ D$_{Zr}$ and D$_{U}$ $>$ D$_{Th}$. Partition coefficients for some polyvalent elements (Sb, W, V) were, as expected, rather sensitive to oxygen fugacity. Melt composition exerts a strong influence on HFSE partition coefficients. With increasing polymerisation of the melt, rutile/melt partition coefficients for the high field strength elements Zr, Hf, Nb and Ta increase about an order of magnitude. However, D$_{Nb}$/D$_{Ta}$ and D$_{Hf}$/D$_{Zr}$ appear not to be affected by melt composition. Because D$_{U}$ $>$ D$_{Th}$, partial melting of rutile-bearing eclogite in subducted lithosphere may cause excesses of $^{230}$Th over $^{238}$U in some island arc lavas, whereas dehydration of subducted lithosphere may cause excesses of $^{238}$U over $^{230}$Th. From our partitioning results we infer partition coefficients for Pa which we predict to be much lower than previously anticipated. Contrary to previous studies, our data imply that rutile should not significantly influence observed $^{231}$Pa-$^{235}$U disequilibria in certain volcanic rocks.
DE: 3630 Experimental mineralogy and petrology
DE: 3640 Igneous petrology
DE: 1065 Trace elements (3670)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting