HR: 14:00h
AN: V42E-02    [PDF]
TI: The Composition of the Depleted Mantle
AU: * Salters, V J
EM: salters@magnet.fsu.edu
AF: National High Magnetic Field Laboratory, Florida State University, 1800E Paul Dirac Drive, Tallahassee, FL 32306 United States
AU: Stracke, A
EM: stracke@mpch-mainz.mpg.de
AF: Max-Planck Institut fur Chemie, J.J. Becher Weg 27, Mainz, FL Germany Germany
AB: We present an estimate for the composition of the depleted mantle (DM), the source for mid-ocean ridge basalts (MORBs). Several avenues are used to derive the estimated composition of the DM. Since trace element ratios can be better determined than absolute concentrations, absolute concentrations are only estimated for a few elements and the majority of the trace element concentrations are based on trace element ratios. The most reliable estimates of trace element ratios are estimates of parent-daughter ratios which are based on the isotopic composition of mid-ocean ridge basalts. These estimates form the "backbone of our trace element estimates. A second way of estimating trace element ratios is through the average composition of primitive normal-type mid ocean ridge basalts. A third group of estimates is derived from the elemental and isotopic composition of peridotites. The major element composition is obtained by subtraction of a low degree melt from a bulk silicate Earth composition. A last group of trace element ratios is derived from continental crust (CC). CC is thought to be approximately complementary to the DM and ratios that are chondritic in the continental crust are expected to also be chondritic in the DM. Volatile element and noble gas concentrations are estimated using constraints from the composition of MORBs and ocean island basalts (OIBs). We have varied the age of the DM and the isotopic composition of the DM to bring La/Nb and Ce/Pb within the range observed in primitive mid-ocean ridge basalts. Only a narrow range of ages, 1.6-2.2Ga, yields appropriate trace element ratios. Mass balance with continental crust indicates that the CC and this estimate of the DM are not complementary reservoirs.
DE: 1025 Composition of the mantle
DE: 1040 Isotopic composition/chemistry
DE: 1094 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting