High Resolution 40Ar/39Ar Geochronology of the Tuvalu Seamount Chain: Implications for Hotspot Longevity and Pacific Plate Motion.

Abstract:

The Tuvalu seamount chain is a Mid-Pacific (4-11^oS, 175-179^oE) linear volcanic chain that was previously poorly sampled. Absolute plate motion (APM) models predict a long-lived relationship with hotspot activity in French Polynesia. The lack of detailed age data therefore results in a key chronologic gap in the geologic history of this hotspot and current APM models. Depending on the set of assumptions employed, previous APM models have disagreed on which known hotspot chain, if any, the Tuvalu volcanoes are associated with. Based on APM modeling and geochemical affinities (HIMU, ²⁰⁶Pb/²⁰⁴Pb > 20), Konter et al. (2008) argue that Rurutu Island (French Polynesia) represents the modern location of the hotspot that contributed volcanism to the Tuvalu seamounts. This model traces the hotspot chain from Rurutu through the region of modern day Samoa, the Tuvalu seamounts, the Gilbert ridge, and into the North & South Wake islands. This hypothesis suggests that a single HIMU mantle reservoir can exist and remain relatively geochemically consistent over 100 Myrs. On the contrary, the Wessel and Kroenke (2008) APM model suggest the Tuvalu seamounts and N & S Wake are unrelated. This model requires the N & S Wake chains to rotate significantly at the young end of the Gilbert Ridge resulting in a current hotspot location around 13-15^oS and 156-155^oW, away from any known active volcanism. During the summer of 2013, 25 Tuvaluan seamounts and 9 seamounts near the current Samoan chain were dredged onboard the R.V. Roger Revelle (expedition RR1310). Here we present 43 new ⁴⁰Ar-³⁹Ar ages covering 19 Tuvaluan seamounts and four seamounts within the Samoan hotspot track. These ages provide insights into the contributing hotspot for Tuvaluan volcanism and provide a new reference frame for constraining Pacific APM models. The corresponding chemical analyses for a subset of these seamounts will be presented by Finlayson et al. (this volume).

Konter, J. G. et al. One hundred million years of mantle geochemical history suggest the retiring of mantle plumes is premature. Earth and Planetary Science Letters 275, 285-295, doi:10.1016/j.epsl.2008.08.023 (2008)

Wessel, P. & Kroenke, L. W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research: Solid Earth (1978–2012) 113 (2008)