In search of a bulk-Earth composition

Hart, Stanley R.; Zindler, Alan

doi:10.1016/0009-2541(86)90053-7

Cited by 618 publications

(352 citation statements)

References 60 publications

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“…6a-6c). The wholerock composition is also comparable to the xenolith compositions of the Injibara area (Conticelli et al, 1999) and the average compositions of the abyssal mantle (Boyd, 1989), continental mantle (Maaløe and Aoki, 1977;McDonough, 1990), primitive mantle (Jagoutz et al, 1979;Hart and Zindler, 1986;Hirose and Kushiro, 1993;Baker and Stolper, 1994;McDonough and Sun, 1995) and southern Ethiopia mantle xenoliths (Bedini et al, 1997;Conticelli et al, 1999;Meshesha et al, 2011) (Fig. 6).…”

Section: Mineral Chemistrysupporting

confidence: 72%

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Geochemical and Sr–Nd–Pb isotopic compositions of lithospheric mantle: Spinel lherzolites in alkaline basalts from the northwestern Ethiopian plateau

Meshesha¹,

Shinjo

Orihashi

2014

Journal of Mineralogical and Petrological Sciences

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The geochemical characteristics of mantle xenoliths (spinel lherzolites) in Quaternary alkaline basalts from the northwestern Ethiopian plateau provide new insight into the conditions of melting associated with the Afar plume. The major element compositions of the spinel lherzolites are in the range of those of the primitive mantle. The high modal content of the clinopyroxene (14-23%) indicate that the mantle xenoliths are fertile spinel lherzolites that have experienced insignificant partial melting. However, enrichment in highly incompatible elements (LREE, Ba, Pb, Th, and U) and the absence of any typical metasomatic minerals indicate that the spinel lherzolites underwent an event of later cryptic metasomatic enrichment induced by plume-related, hydrous fluid-rich silicate melts. The

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Section: Mineral Chemistrysupporting

confidence: 72%

“…Moreover, the whole-rock compositions of the spinel lherzolites approach those of the depleted primitive mantle (Jagoutz et al, 1979;Hart and Zindler, 1986;Hirose and Kushiro, 1993;Baker and Stolper, 1994;McDonough and Sun, 1995) (Table 1 and Fig. 6).…”

Section: Evidence Of Partial Melting and Melt Extractionmentioning

confidence: 82%

Geochemical and Sr–Nd–Pb isotopic compositions of lithospheric mantle: Spinel lherzolites in alkaline basalts from the northwestern Ethiopian plateau

Meshesha¹,

Shinjo

Orihashi

2014

Journal of Mineralogical and Petrological Sciences

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“…Physical properties were then computed from the appropriate results depending upon whether melt was predicted to be stable from the experimentally constrained phase relations (Table B3). Examples of phase diagrams computed for different lithologies are discussed by [Connolly [Plank and Langmuir, 1998]; basalt is an average for the upper 500 m of the igneous section of the oceanic crust [Staudigel et al, 1989]; gabbro is a synthetic composition for the gabbroic section of the oceanic crust [Behn and Kelemen, 2003], modified to contain up to 1.5 wt% water to represent the effects of lower crustal hydrothermal alteration [Carlson, 2003], and peridotite is the LOSIMAG composition [Hart and Zindler, 1986] chosen to represent mantle peridotite. The compositions have been simplified by the omission of minor elements such as Mn, P, Ti, and Cr and the assumption that all Fe is ferrous; additionally, CO 2 has been removed from the GLOSS sediment composition.…”

Section: B4 Obtaining Mineralogymentioning

confidence: 99%

Large‐scale rigid‐body rotation in the mantle wedge and its implications for seismic tomography

Gorczyk

Gerya

Connolly

et al. 2006

Geochem Geophys Geosyst

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[1] Using a combined finite difference and marker-in-cell technique, we performed two-dimensional coupled petrological-thermomechanical numerical simulations of intraoceanic subduction. The simulations indicate that parts of the mantle wedge can become trapped between rheologically weak, hydrated, and partially molten upwellings (cold plumes) and the subducting slab. The structures form at various depths and develop circular, elliptic, or irregular shapes. The combined effect of the tractions caused by upwelling and subduction causes these regions to rotate. Our simulations investigate the parameters controlling the occurrence and long-term stability of such rigid, rotating structures. Circular rotating structures like ''subduction wheels'' are characteristic of models with relatively young (20-30 Myr) slabs and intermediate (2-5 cm/yr) subduction rates. We propose that the development of such circular features may explain some of the isolated seismic velocity anomalies in the mantle wedge.

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“…Because Pb is not a refractory element, its abundance in the bulk earth cannot be determined directly by comparison with meteorite abundances of refractory elements. While Pb contents are reasonably well-behaved in terrestrial peridotites Meijer et al 1990), no one has attempted to derive bulk earth Pb abundances using the approach of Jagoutz et al (1979) and Hart and Zindler (1986). Instead, the conventional approach is to use Pb isotopes to define the 238 U/ 204 Pb ratio (µ) of the mantle, and then to deduce the Pb content from the bulk earth abundance of U, a refractory element well-modeled using a chondritic analogue.…”

Section: Introductionmentioning

confidence: 99%

Mantle Pb paradoxes: the sulfide solution

Hart

Gaetani

2006

Contrib Mineral Petrol

116

108

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There is growing evidence that the budget of Pb in mantle peridotites is largely contained in sulfide, and that Pb partitions strongly into sulfide relative to silicate melt. In addition, there is evidence to suggest that diffusion rates of Pb in sulfide (solid or melt) are very fast. Given the possibility that sulfide melt 'wets' sub-solidus mantle silicates, and has very low viscosity, the implications for Pb behavior during mantle melting are profound. There is only sparse experimental data relating to Pb partitioning between sulfide and silicate, and no data on Pb diffusion rates in sulfides. A full understanding of Pb behavior in sulfide may hold the key to several long-standing and important Pb paradoxes and enigmas. The classical Pb isotope paradox arises from the fact that all known mantle reservoirs lie to the right of the Geochron, with no consensus as to the identity of the "balancing" reservoir. We propose that long-term segregation of sulfide (containing Pb) to the core may resolve this paradox.Another Pb paradox arises from the fact that the Ce/Pb ratio of both OIB and MORB is greater than bulk earth, and constant at a value of 25. The constancy of this "canonical ratio" implies similar partition coefficients for Ce and Pb during magmatic processes (Hofmann et al. 1986), whereas most experimental studies show that Pb is more incompatible in silicates than Ce. Retention of Pb in residual mantle sulfide during melting has the potential to bring the bulk partitioning of Ce into equality with Pb if the sulfide melt/silicate melt partition coefficient for Pb has a value of ~ 14. Modeling shows that the Ce/Pb (or Nd/Pb) of such melts will still accurately reflect that of the source, thus enforcing the paradox that OIB and MORB mantles have markedly higher Ce/Pb (and Nd/Pb) than the bulk silicate earth. This implies large deficiencies of Pb in the mantle sources for these basalts. Sulfide may play other important roles during magmagenesis: 1). advective/diffusive sulfide networks may form potent metasomatic agents (in both introducing and obliterating Pb isotopic heterogeneities in the mantle); 2). silicate melt networks may easily exchange Pb with ambient mantle sulfides (by diffusion or assimilation), thus 'sampling' Pb in isotopically heterogeneous mantle domains differently from the silicate-controlled isotope tracer systems (Sr, Nd, Hf), with an apparent 'de-coupling' of these systems.

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In search of a bulk-Earth composition

Cited by 618 publications

References 60 publications

Geochemical and Sr–Nd–Pb isotopic compositions of lithospheric mantle: Spinel lherzolites in alkaline basalts from the northwestern Ethiopian plateau

Geochemical and Sr–Nd–Pb isotopic compositions of lithospheric mantle: Spinel lherzolites in alkaline basalts from the northwestern Ethiopian plateau

Large‐scale rigid‐body rotation in the mantle wedge and its implications for seismic tomography

Mantle Pb paradoxes: the sulfide solution

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