Mantle depleted

In summary, many recent studies have argued for three components in most arc lavas depleted mantle, basalt-derived fluid, and sediment (in bulk, via fluid, or via melt)... 

Ewart A, Hawkesworth CJ (1987) The Pleistoeene-Reeent Tonga-Kermadee are lavas Interpretation of new isotopic and rare earth data in terms of a depleted mantle somce model. J Petrol 28 495-530 Fumkawa F (1993a) Magmatic processes under arcs and formation of the volcanic front. J Geophys Res 98 8309-8319... 

Woodhead J, Eggins S, Gamble J (1993) High field strength and transition element systematics in island arc and back-arc basin basalts evidence for multi-phase melt extraction and a depleted mantle wedge. Earth Planet Sci Lett 114 491-504... 

In the 143Nd/l44Nd vs 87Sr/86Sr plot, draw the mixing triangle at the 20 percent mesh size for a mixture of three mantle components, the depleted mantle (DM), the enriched mantle I (EM I) and the enriched mantle II (EM II). The isotopic ratios and relative concentrations of each component are listed in Table 1.10. 

Albarede, F. Brouxel, M. (1987). The Sm/Nd secular evolution of the continental crust and depleted mantle. Earth Planet. Sci. Letters, 82, 25-35. 

Grustal reservoirs are also variable in Gl-isotope compositions (Figs. 1-6) due to fractionation of the Gl-isotope compositions inherited from their mantle source through fluid-mineral reactions, incorporation of G1 derived from the oceans and fractionation within fluid reservoirs by diffusion (see below). For example, the oceanic crust is enriched in Gl (and pore fluids depleted in Gl) through reaction of seawater with basaltic crust derived from the depleted mantle (Fig. 1 Magenheim et al. 1995). Undoubtedly, future investigations of Gl-isotopes in whole rocks and mineral separates will address the Gl-isotope compositions of these reservoirs and their evolution. 

Salters, V. and Stracke, A. (2004) Composition of the depleted mantle. Geochemistry, Geophysics, Geosystems, 5(5), 1525-2027. 

A simple model, which is often advanced, is that there are basically two kinds of mantle, or two prominent poles in a spectrum of mantle characteristics. One kind is depleted mantle, material that has undergone at least one episode, or probably more,... 

Fisher, D. E. (1985b) Radiogenic rare gases and the evolutionary history of the depleted mantle. J. Geophys. Res., 90(B2), 1801-7. 

Lee D.-C. and Halliday A. N. (2000b) Hf-W isotopic systematics of ordinary chondrites and the initial i82Hf/i80Hf of the solar system. Chem. Geol. 169, 35-43. Lee D.-C., Halliday A. N., Davies G. R., Essene E. L, Eitton J. G., and Temdjim R. (1996) Melt enrichment of shallow depleted mantle a detailed petrological, trace element and isotopic study of mantle derived xenohths and megacrysts from the Cameroon line. J. Petrol. 37, 415-441. 

Copper. The abundance of copper in the depleted mantle raises a particular problem. Unlike other moderately compatible elements, there is a difference in the copper abundances of massive peridotites compared to many, but not all, of the xenolith suites from alkali basalts. The copper versus MgO correlations in massive peridotites consistently extrapolate to values of 30 ppm at 36% MgO, whereas those for the xenoliths usually extrapolate to <20 ppm, albeit with much scatter. A value of 30 ppm is a relatively high value when chondrite normalized ((Cu/Mg)N = 0.11), and would imply Cu/Ni and Cu/Co ratios greater than chondritic, difficult to explain, if true. However, the copper abundances in massive peridotites are correlated with sulfur, and may have been affected by the sulfur mobility postulated by Lorand (1991). Copper in xenoliths is not correlated with sulfur, and its abundance in the xenoliths and also inferred from correlations in basalts and komatiites points to a substantially lower abundance of 20 ppm (O Neill, 1991). We have adopted this latter value. 

Chondritic relative abundances of strongly incompatible RLEs (lanthanum, niobium, tantalum, uranium, thorium) and their ratios to compatible RLEs in the Earth s mantle are more difficult to test. The smooth and complementary patterns of REEs in the continental crust and the residual depleted mantle are consistent with a bulk REE pattern that is flat, i.e., unfractionated when normalized to chondritic abundances. As mentioned earlier, the isotopic compositions of neodymium and hafnium are consistent with chondritic Sm/Nd and Lu/Hf ratios for bulk Earth. Most authors, however, assume that RLEs occur in chondritic relative abundances in the Earth s mantle. However, the uncertainties of RLE ratios in Cl-meteorites do exceed 10% in some cases (see Table 4) and the uncertainties of the corresponding ratios in the Earth are in same range (Jochum et ai, 1989 W eyer et ai, 2002). Minor differences (even in the percent range) in RLE ratios between the Earth and chondritic meteorites cannot be excluded, with the apparent exception of Sm/Nd and Lu/Hf ratios (Blicher-Toft and Albarede, 1997). 

Campbell I. H. (2002) Implications of Nb/U, ThAJ and Sm/Nd in plume magmas for the relationship between continental and oceanic crust formation and the development of the depleted mantle. Geochim. Cosmochim. Acta 66, 1651-1662. 

MID-OCEAN RIDGE BASALTS SAMPLES OF THE DEPLETED MANTLE... 

Mid-Ocean Ridge Basalts Samples of the Depleted Mantle... 

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