Heterogeneities upper mantle

Zindler A, Hart SR (1986) Chemical geodynamics. Aim Rev Earth Planet Sci 14 493-571 Zindler A, Standigel H, Batiza R (1984) Isotope and trace element geochemistry of young Pacific seamounts implications for the scale of upper mantle heterogeneity. Earth Planet Sci Lett 70 175-190... 

Since hthium and boron isotope fractionations mainly occur during low temperature processes, Li and B isotopes may provide a robust tracer of surface material that is recycled to the mantle (Elhott et al. 2004). Heterogeneous distribution of subducted oceanic and continental crust in the mantle will thus result in variations in Li and B isotope ratios. Furthermore, dehydration processes active in subducdon zones appear to be of crucial importance in the control of Li and B isotope composition of different parts of the mantle. For the upper mantle as a whole Jeffcoate et al. (2007) gave an estimated 8 Li-value of 3.5%o. 

Meibom A., Sleep N. H., Chamberlain C. P., Coleman R. G., Frei R., Hren M. T., and Wooden J. L. (2002c) Re-Os isotopic evidence for long-lived heterogeneity and equilibration processes in the Earth s upper mantle. Nature 419(6908), 705-708. 

Schiano P., Birck J.-L., and Allegre C. J. (1997) Osmium-strontium-neodymium-lead isotopic covariations in midocean ridge basalt glasses and the heterogeneity of the upper mantle. Earth Planet. Sci. Lett. 150, 363-379. 

In this chapter, we review the main inferences on upper mantle composition and heterogeneity that may be drawn from geochemical analyses of the major elements, lithophile trace elements, and Nd-Sr isotopes in tectonically emplaced and abyssal mantle rocks. In addition we emphasize important insights into the mechanisms of melt/fluid transfer that can be deduced from detailed studies of these mantle materials. 

Girardeau J. and Gil Ibarguchi J. I. (1991) Pyroxene-rich peridotites of the Cabo Ortegal Complex (Northwestern Spain) evidence for large-scale upper-mantle heterogeneity. J. Petrol. (Orogenic IherzoUtes and mantle processes) (sp. vol.), 135-154. 

Overall, using the basic principles of this model, the basic relationships between the isotopic compositions of the atmosphere and upper mantle cannot be explained. However, the preservation of noble gas isotope heterogeneities in convectively isolated mantle layers remains appealing. 

Wass S. Y., Henderson P., and Elliot C. J. (1980) Chemical heterogeneity and metasomatism in the upper mantle evidence from rare earth and other elements in apatite-rich... 

Various types of mantle heterogeneities have been identified that differ from one another in their major element, trace element, and isotope sys-tematics (see Chapter 2.03). A number of these distinct types of heterogeneities, particularly in isotopic composition, are most strongly manifest by hotspot volcanism (e.g.. Hart and Zindler, 1989). In addition, however, it is clear that there are dispersed heterogeneities in the upper mantle that are sampled by melting at mid-ocean ridges far removed from hotspot influences. 

Schilling J.-G. (1985) Upper mantle heterogeneities and dynamics. Nature 314, 62-67. 

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