Ebel, D.S., and A.J. Campbell (1998) Geological Society of America, Abstracts with Program, 30A: 318.

RHODIUM AND PALLADIUM PARTITIONING BETWEEN COPPER-NICKEL-PYRRHOTITE AND SULFIDE LIQUID

EBEL, D. S., and CAMPBELL, A. J., Dept. Geophysical Sciences, University of Chicago, 5734 S. Ellis Ave., Chicago IL 60637, debel@ and acampbel@midway.uchicago.edu

Partition coefficients for Rh and Pd between monosulfide solid solution (mss), (Fe,Ni,Cu, PGE)1-xS, and sulfide liquid (matte) have been determined from experiments in which ~0.1g of simple sulfides doped with Rh or Pd were heated in silica tubes for several days, then quenched very rapidly, all using techniques of, and yielding major element contents of two-phase results highly consistent with, Ebel and Naldrett (1997). Multiple polished mss/matte interfaces were analyzed for PGE using the laser ablation ICP-MS facility at Chicago:
.......... Nominal bulk wt%........ PGE in mss.... PGE in matte.. D(PGE)
expPGE FeNiCuS T(C) nppm1s nppm1s mss/matte
PdN4Pd 58.65.1036.4 1100 121.990.44 1230.476.48 0.065
PdC2Pd 54.90.38.736.0 1100 64.350.38 6204.19.97 0.021
RN2Rh 58.85.1036.1 1100 72.580.17 86.671.23 0.387
RN3bRh 47.214.7038.1 1100 65.010.17 72.590.15 1.931
RC2Rh 54.00.59.536.0 1100 81.290.46 80.690.46 1.877
RC1bRh 51.30.69.538.5 1100 729.041.995 128.781.24 3.307
RC3Rh 57.00.63.239.1 1150 1120.360.90 78.011.12 2.542
RC4Rh 58.00.64.037.5 1150 2015.710.51 1511.521.06 1.364

Fleet et al. (1993) obtained major element equilibria broadly consistent with more recent work, and D(Rh)=3.0± 0.7 and D(Pd)=0.21± 0.08, at ~1020° C, in seven experiments with 20 to 50 ppm of each of six PGEs, ~5 wt% Cu, Ni at ~24 or 7 wt%. Our results suggest D for Rh and Pd decrease with decreasing f(S2), and both Rh and Pd "prefer" matte when the degree of metallic bonding in the matte increases. A value of 2.5<D(Rh)<3.0 is consistent with the natural buffering effects observed in magmatic Ni-PGE ores. Further work clearly will be required, to establish the major element dependence of these and other PGE mss/matte partition coefficients of geological interest.


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