Thallium Isotopic Compositions in Hawaiian Lavas: Evidence for Recycled Materials on the Kea Side of the Hawaiian Mantle Plume

Abstract

The Hawaiian-Emperor chain is an ideal natural laboratory for exploring mantle chemical heterogeneity because it records over 80 Ma of potentially deep Pacific mantle chemistry along nearly 6,000 km of seamounts and volcanoes created by the long-lived Hawaiian mantle plume (e.g.

Emergence of the Loa Mantle Component in the Hawaiian Islands Based on the Geochemistry of Kauaʻi Shield‐Stage Basalts

“…Additional Hf isotopic data for Kea group samples would help further validate this observation, as there are still significantly less Hf isotopic data available for Hawaiian shield-stage samples than Pb, Sr, or Nd (e.g., for the Kea geochemical group samples, n = 257 for Hf isotopes and n = 436 for Nd isotopes, with only 165 samples having both Hf and Nd isotopes). However, the Kea slope supports the possibility that recycled materials influence Kea geochemical compositions as well as Loa and Enriched Loa compositions (Williamson et al, 2021), and in this case that the chemical differences between Hawaiian geochemical groups/end-members reflect the different origins and ages of recycled materials in the lower mantle, whether within or outside of the LLSVP (Weis et al, 2020;Williamson et al, 2021).…”

“…Typically, the Loa and Enriched Loa Hawaiian geochemical groups are associated with recycled materials (Fekiacova et al, 2007;Tanaka et al, 2002Tanaka et al, , 2008Weis et al, 2011Weis et al, , 2020. However, recent work has shown recycled materials potentially present in the Kea Hawaiian source as well, originating from the outside of the Pacific LLSVP (Williamson et al, 2021). The ε Hf -ε Nd arrays for each of the Loa (light blue dashed line in Figure 10d), Enriched Loa (blue dashed line), and Kea (red dashed line) Hawaiian geochemical groups suggest that the Kea group of samples may be controlling the shallower ε Hf -ε Nd slope of the Hawaiian array (Figure 10d).…”

Identifying Tethys oceanic fingerprint in post-collisional potassium-rich lavas in Tibet using thallium isotopes

“…In recent years, Tl isotopic compositions have been increasingly applied to track recycling of oceanic sediments and slab-derived fluids in igneous rocks from subduction and plume settings (e.g., Nielsen et al, 2006aNielsen et al, , 2007Nielsen et al, , 2016Nielsen et al, , 2017aPrytulak et al, 2013;Shu et al, 2017Shu et al, , 2019Shu et al, , 2022Blusztajn et al, 2018;Brett et al, 2021;Williamson et al 2021). Thallium has two stable isotopes, 203 Tl and 205 Tl, and isotopic variations are reported in epsilon notation relative to NIST Tl standard SRM997, which is defined as zero, by the equation: 205 Tl = 10,000 × [( 205 Tl/ 203 Tlsample -205 Tl/ 203 TlSRM997)/( 205 Tl/ 203 TlSRM997)] Thallium is a heavy metal with a large ionic radius (Tl + =1.49Å; Shaw, 1952), whose oxidation states are Tl + and Tl 3+ .…”