Fractionation of the Platinum-Group Elements During Mantle Melting

Bockrath, Conny; Ballhaus, Chris; Holzheid, Astrid

doi:10.1126/science.1100160

Cited by 280 publications

(143 citation statements)

References 27 publications

Supporting

Mentioning

130

Contrasting

Unclassified

Order By: Relevance

“…There is very little data (at mantle P&T) relevant to the partitioning of Pb between the silicate and sulfide phases of interest here (this is in stark contrast to the wealth of data on sulfide-silicate partitioning of PGEs (Barnes et al 2004;Bockrath et al 2004;Fleet et al 1991;Fleet et al 1996;Li et al 1996;Peach et al 1994;Sattari et al 2002)). Oversby and Ringwood (1971) reported Pb partition coefficients of 9.8 and 12.4 between sulfide and basaltic melts.…”

Section: Iiib Pb Partitioning Between Sulfides and Silicatesmentioning

confidence: 42%

“…What stands out here is the low temperature of the sulfide solidus, and the large two-phase solid + liquid sulfide field. Note that the highly-curved sulfide liquidus as drawn by Bockrath et al (2004) is not well constrained at high temperature, and is in fact inconsistent with the congruent melting temperature of pure FeS (shown on the figure). The univariant melting of troilite should set an upper limit for the polyvariant melting of Mss (i.e.…”

Section: Iiia Mantle Sulfide Abundances and Petrologymentioning

confidence: 91%

“…Oversby and Ringwood (1971) reported Pb partition coefficients of 9.8 and 12.4 between sulfide and basaltic melts. However, their sulfide melts were cation-rich compared to likely mantle sulfide compositions (molar Fe/S ~ 1.3, compared to the molar (Fe+Ni+Cu)/S ratio of 0.93 adopted by Bockrath et al 2004). Shimizaki and MacLean (1976) reported Pb partitioning between oxygen-rich Fe-Pb sulfide liquids and a compositionally simple SiO 2 -Na 2 O-FeO silicate melt (~ 34% Fe).…”

Section: Iiib Pb Partitioning Between Sulfides and Silicatesmentioning

confidence: 99%

“…Sulfide melts are unquenchable in nature (and only with great difficulty in the lab). Figure 4 shows a P-T phase diagram for the melting relationships of a particular Mss composition, chosen to be appropriate for equilibrium with mantle peridotite (adapted from Bockrath et al 2004). What stands out here is the low temperature of the sulfide solidus, and the large two-phase solid + liquid sulfide field.…”

Section: Iiia Mantle Sulfide Abundances and Petrologymentioning

confidence: 99%

“…7). This is the type of sulfide thought to be present in the upper mantle (e.g., Bockrath et al 2004), and the transition from non-wetting to wetting (i.e. " = 60°) for these melts with respect to olivine occurs when the concentration of O exceeds ~ 2 to 6 wt% to pressures of at least 3.9 GPa (Fig.…”

Section: Iiie Transport Of Pb By Advection Of Sulfide Meltmentioning

confidence: 99%

See 4 more Smart Citations

Mantle Pb paradoxes: the sulfide solution

Hart

Gaetani

2006

Contrib Mineral Petrol

116

108

View full text Add to dashboard Cite

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.

show abstract

Section: Iiib Pb Partitioning Between Sulfides and Silicatesmentioning

confidence: 42%

Section: Iiia Mantle Sulfide Abundances and Petrologymentioning

confidence: 91%

Section: Iiib Pb Partitioning Between Sulfides and Silicatesmentioning

confidence: 99%

Section: Iiia Mantle Sulfide Abundances and Petrologymentioning

confidence: 99%

Section: Iiie Transport Of Pb By Advection Of Sulfide Meltmentioning

confidence: 99%

See 3 more Smart Citations

Mantle Pb paradoxes: the sulfide solution

Hart

Gaetani

2006

Contrib Mineral Petrol

116

108

View full text Add to dashboard Cite

show abstract

Chalcophile behavior of thallium during MORB melting and implications for the sulfur content of the mantle

Nielsen

Shimizu

Lee

et al. 2014

Geochem Geophys Geosyst

View full text Add to dashboard Cite

We present new laser ablation ICP-MS trace element concentration data for 28 elements in 97 mid-ocean ridge basalt (MORB) glasses that cover all major spreading centers as well as Tl concentration data for all mineral phases in five lherzolites from the Lherz massif, France. The ratio between the elements thallium (Tl) and cerium (Ce) is nearly constant in MORB, providing evidence that the depleted MORB mantle (DMM) has uniform Ce/Tl. Lherzolite mineral data reveal that sulfides are heterogeneous and contain between 23 and 430 ng/g of Tl while all other minerals contain Tl below the analytical detection limit of 1 ng/g. We argue that Tl in MORB is controlled by residual sulfide during mantle melting. To investigate the observed relationship between Tl and Ce, we conduct models of fractional mantle melting, which show that the constant Ce/Tl in MORB is only reproduced if the ratio between clinopyroxene and sulfide in the upper mantle varies by less than 10%. In addition, the rate of melting for these two phases must be nearly identical as otherwise melt depletion and refertilization processes would lead to Ce/Tl fractionation. These model results allow us to establish a relationship for the sulfur content of DMM: [S] DMM 5 SCSS 3 M cpx =R cpx , where SCSS is the sulfur concentration of a silicate melt at sulfide saturation, R cpx is the melt reaction coefficient, and M cpx is the modal abundance of clinopyroxene in the DMM. Using this equation, we calculate that the average upper mantle sulfur concentration is 195 6 45 lg/g.

show abstract