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Age and geochemistry of the oceanic Manihiki Plateau, SW Pacific: New evidence for a plume origin

Timm, C, Hoernle, K, Werner, R, Hauff, F, Van Den Bogaard, P, Michael, P, Coffin, MF and Koppers, A 2011 , 'Age and geochemistry of the oceanic Manihiki Plateau, SW Pacific: New evidence for a plume origin' , Earth and Planetary Science Letters, vol. 304 , pp. 135-146 , doi:

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We present 40Ar/39Ar age and geochemical (major and trace element and Sr–Nd–Hf–Pb isotope) data from
submarine samples recovered from the basement of the Manihiki Plateau during the R/V Sonne research
expedition SO193. The samples, predominately tholeiites, with minor occurrences of basaltic andesites and
hawaiites, give amean age of 124.6±1.6 Ma fromfour different localities on the plateau. Based on TiO2 content,
we define two groups of volcanic rocks that differ in trace element and isotopic compositions. Partial melting
modeling suggests that the low-Ti group lavas were derived through large degrees of melting (c. 30%) of a
peridotitic source at mantle potential melting temperatures of c. Tp=1510 °C, more than 100 °C above the
ambientmantle potential melting temperature. Since the primary water contents of both groups of lavas are low
(0.1–0.3g wt.%) and the source is peridotitic, excess temperature is most likely the reason for the large degrees of
melting producing the large volume of plateau basalts, consistent with the involvement of a mantle plume. The
incompatible element contents of the low-Ti group lavas showamultistage history with enrichment in themost
incompatible elements of a previously highly depleted source. They have isotopic compositions similar to
enriched mid-ocean-ridge basalt (EMORB) and similar to the common focal zone (FOZO) component. The high-Ti
group lavas have more enriched incompatible element compositions overall. Their isotopic compositions tend
towards an enrichedmantle (EMI)-type endmember, similar, although less extreme, than lavas fromthe Pitcairn
Islands. The geochemistry of the Manihiki Plateau can best be explained by a plume containing three
components: 1) a dominant peridotitic FOZO-type component, 2) delaminated EMI-type subcontinental
lithospheric mantle (SCLM), and 3) a HIMU (recycled oceanic crustal)-type component possibly in the form of
eclogite/pyroxenite. The similarity in age and geochemical composition of Manihiki, Hikurangi and Ontong Java
basement lavas, including volcanism in some adjacent basins, suggests that the Greater Ontong Java Volcanic
Event covered c. 1% of the Earth's surface with volcanism.

Item Type: Article
Authors/Creators:Timm, C and Hoernle, K and Werner, R and Hauff, F and Van Den Bogaard, P and Michael, P and Coffin, MF and Koppers, A
Keywords: Manihiki Plateau oceanic large igneous province 40Ar/39Ar age dates major and trace element and Sr–Nd–Hf–Pb isotope geochemistry volatiles Greater Ontong Java Event
Journal or Publication Title: Earth and Planetary Science Letters
ISSN: 0012-821X
DOI / ID Number:
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Copyright 2011 Elsevier

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