TY - JOUR
T1 - Fractionation of highly siderophile elements in refertilized mantle
T2 - implications for the Os isotope composition of basalts
AU - Marchesi, Claudio
AU - Dale, Christopher W.
AU - Garrido, Carlos J.
AU - Pearson, D. Graham
AU - Bosch, Delphine
AU - Bodinier, Jean Louis
AU - Gervilla, Fernando
AU - Hidas, Karoly
PY - 2014/8/15
Y1 - 2014/8/15
N2 - Highly fertile lherzolite and spinel websterite in the Ronda peridotite massif are enriched in Pt and Pd compared to Os, Ir, Ru and Re. The fractionation of the highly siderophile elements (HSE) in these rocks was produced by reaction of melt with their peridotite and pyroxenite precursors. Modeling indicates that upon reaction primary HSE hosts were dissolved and magmatic sulphides precipitated, largely erasing the original HSE signature of reacting protoliths. The budget of HSE in the melt was controlled by sulphide-silicate partitioning or entrainment of molten sulphide in silicate melt. Rhenium was likely removed from precursor peridotite and pyroxenite by previous melt extraction. Refertilization of peridotite by melts increased Al2O3, CaO, Pt, Pd contents and Os-187/Os-188 beyond typical values for mantle peridotite and the primitive upper mantle. The interaction of melts with residual peridotite and pyroxenite, as illustrated in the Ronda massif, can generate radiogenic-Os-enriched domains in the mantle with high melt productivity, higher Pt/Os and Pt/Re than common peridotite, and lower Re/Os than typical pyroxenite. As also previously proposed for pyroxenites, these "hybrid" domains can account for the difference in Os isotope compositions between many basalts (e.g., MORB and OIB) and common depleted mantle peridotites. Moreover, the presence of these enriched hybrid components in the mantle, evolved over sufficient timescales and in geologically reasonable proportions, may account for the Os-186-Os-187 enrichment of plume lavas without requiring a chemical contribution from the core. (C) 2014 Elsevier B.V. All rights reserved.
AB - Highly fertile lherzolite and spinel websterite in the Ronda peridotite massif are enriched in Pt and Pd compared to Os, Ir, Ru and Re. The fractionation of the highly siderophile elements (HSE) in these rocks was produced by reaction of melt with their peridotite and pyroxenite precursors. Modeling indicates that upon reaction primary HSE hosts were dissolved and magmatic sulphides precipitated, largely erasing the original HSE signature of reacting protoliths. The budget of HSE in the melt was controlled by sulphide-silicate partitioning or entrainment of molten sulphide in silicate melt. Rhenium was likely removed from precursor peridotite and pyroxenite by previous melt extraction. Refertilization of peridotite by melts increased Al2O3, CaO, Pt, Pd contents and Os-187/Os-188 beyond typical values for mantle peridotite and the primitive upper mantle. The interaction of melts with residual peridotite and pyroxenite, as illustrated in the Ronda massif, can generate radiogenic-Os-enriched domains in the mantle with high melt productivity, higher Pt/Os and Pt/Re than common peridotite, and lower Re/Os than typical pyroxenite. As also previously proposed for pyroxenites, these "hybrid" domains can account for the difference in Os isotope compositions between many basalts (e.g., MORB and OIB) and common depleted mantle peridotites. Moreover, the presence of these enriched hybrid components in the mantle, evolved over sufficient timescales and in geologically reasonable proportions, may account for the Os-186-Os-187 enrichment of plume lavas without requiring a chemical contribution from the core. (C) 2014 Elsevier B.V. All rights reserved.
KW - basalt
KW - heterogeneous mantle
KW - highly siderophile elements
KW - mantle refertilization
KW - melting
KW - Os isotopes
UR - http://www.scopus.com/inward/record.url?scp=84901768407&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2014.05.025
DO - 10.1016/j.epsl.2014.05.025
M3 - Article
SN - 0012-821X
VL - 400
SP - 33
EP - 44
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -