What is the origin of OIB?

John Caulfield

•Identification and explanation of similarities and differences in isotopic ratios (Sr, Nd, Os, O and Pb) between OIB and MORB, Mantle and Continental Crust.

•Hence, which mantle components are unique to OIB, and which heterogeneities are the result of localised OIB interaction with crust and mantle.

Sr-Nd Isotope correlations

OIB

MORB

ENRICHED

DEPLETED

SCLM

SCLM xenolith Os concs.

Modified from Hofmann 1997.

Pearson et al. 1995

Element compatibility plot•Greater enrichment in incompatible elements suggests OIB are smaller degree melts than MORB. Plume emplacement required for OIB?

•OIB has Nb and Pb anomalies with the same sense as MORB, and opposite to those of C.C. excludes simple two component mixing.

Modified from Hofmann 1997.

Multi-Component mixing 1•OIB’s can be distinguished by their enrichment in three mantle components, EM1, EM2 and HIMU all of which can show elevated 187Os/188Os – suggestive of a common source.

•All mixing arrays converge on depleted FOZO component that is distinct from the DMM component in terms of Pb concentration.

Van Keken et al. 2002

Multi-component mixing 2•Elevated 3He/4He of FOZO indicates primitive nature

•All arrays contain FOZO, but not EM1, EM2 and HIMU all together.

•OIB source model must reconcile supply of EM/HIMU components in differing proportions and subsequent mixing with FOZO.

Van Keken et al. 2002

Recycling of subducted oceanic crust•Subducted slab provides source for three enriched mantle components and allows for elevated 187Os/188Os.

HIMU- Recycled oceanic crust

EM1- Oceanic lithosphere

EM2- Modern sediments

Lassiter and Hauri 1998δ18O

187Os/188Os correlates with δ18O.

δ18O

Koolau and Kea Components•Koolau=subducted oceanic crust component and modern sediments

•Kea=recycled oceanic lithosphere

Koolau displays elevated 3He consistent with entrainment of FOZO above D”

Lassiter and Hauri 1997

Preservation of Heterogeneity

•Metabasaltic lithosphere transforms to Eclogite at approx. 100km depth.

•Increased viscosity of Eclogite(Garnet+Cpx) preserves slab heterogeneity.

•High Sm/Yb ratios in Hawaiian lavas reflect the presence of Garnet in their source, precluding generation of melts in the upper lithospheric mantle.

Lassiter and Hauri 1997.

OIB Diversity

•Lavas of the Honolulu series formed in the presence of residual amphibole ± phlogopite

•Both phases are temperature sensitive and cannot have a plume origin.

•These lavas are best accounted for by the mixing of an upwelling plume with oceanic lithospheric mantle.

Class and Goldstein 1997.

Review

• OIB are the product of mixing of enriched mantle components and lower mantle depleted FOZO.

• Recycling of subducted slab is supported as it accounts for correlations between Os and O.

• Localised OIB heterogeneity can be accounted for by mixing of the plume source with upper mantle components.

References

Class, C., Goldstein, S.L. Plume lithosphere interactions in the ocean basins: constraints from the source mineralogy. Earth and Planetary Sci. Lett. 150 (1997) 245-260.

Garcia, M.O., Ito, E., Eiler, J.M., Pietruszka. Cruatal contamination of Kilauea Volcano magmas revealed by oxygen Isotope analyses of Glass and Olivine from Puu Oo eruption Lavas. Journal of Petrology 1998 vol. 39 no.5 p.803-817.

Hofmann, A.W. Mantle Geochemistry: the message from oceanic volcanism. Nature vol. 385 (1997) p.219-229.

Lassiter, J.C., Hauri, E.H. Osmium-isotope variations in Hawaiian lavas: evidence for recycled oceanic lithosphere in the Hawaiian plume. Earth and Planetary Sci. Lett. 164 (1998) p.483-496

Pearson, D.G., R.W. Carlson, R.W., Shirley S.B., Boyd, F.R., Nixon P.H. Stabilisation of Archean Lithospheric mantle: A Re-Os study of peridotite xenoliths from the Kaapvaal Craton. Earth and Planetary Sci. Lett. 134. (1995) p.341-357

Van Keken, P.E., Hauri, E.H., Ballentine, C.J. Mantle Mixing: The generation, preservation, and destruction of chemical heterogeneity. Annu. Rev. Earth Planet. Sci. (2002), 30 p.493-525.