Platinum peridotite xenoliths

Irvine G. J. (2002) Time constraints on the formation of lithospheric mantle beneath cratons a Re—Os isotope and Platinum Group Element study of peridotite xenoliths from Northern Canada and Lesotho, PhD Thesis, University of Durham. 

Lee C. T. (2002) Platinum-group element geochemsitry of peridotite xenoliths from the Sierra Nevada and the Basin and Range, California. Geochim. Cosmochim. Acta 66, 3987-4006. 

In contrast, peridotites metasomatized by small melt fractions show enrichment in platinum and palladium and elevated (Pd/Ir) . Bulk mineral separate PGE-Re analyses of two fertile xenoliths from southeastern Australia indicate less than 6% of the whole-rock PGE budget resides in either silicate or oxide phases and further implicates sulfides and alloys as the main controls of PGE-Re abundance. Comparison of sulfide versus whole-rock budgets by Lorand and Alard (2001) demonstrates the dominance of sulfide as the main PGE host in relatively fertile peridotites. This confirms the results of earlier studies of xenolith PGE mass balance (Hart and Ravizza, 1996 Mitchell and Keays, 1981) plus xenolith-derived and diamond inclusion sulfide studies (Jagoutz et al, 1979 Pearson et al, 1998b). As with cratonic xenoliths, sulfur-PGE and major-element-PGE correlations in more depleted noncratonic peridotites indicate that I-PGEs are probably not hosted entirely by sulfide (Lee, 2002). 

Pearson D. G., Irvine G. J., Ionov D. A., Boyd F. R., and Dreibus G. E. (2004) Re-Os isotope systematics and platinum group element fractionation during mantle melt extraction a study of massif and xenolith peridotite suites. Chem. Geol. (special volume) Highley Siderophile Elements (in press). 

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