Sulfide Dissolution on the Nickel Isotopic Composition of Basaltic Rocks

Abstract

In spite of the high abundance of nickel (Ni) in igneous rocks and wide use of Ni in identifying the processes that govern planetary differentiation (e.g., McDonough & Sun, 1995;Palme & O'Neill, 2014), Ni stable isotopes have received limited attention (e.g., Elliott & Steele, 2017). Systematic Ni isotopic studies on terrestrial igneous rocks have only been made in the past few years (

Ni isotopes provide a glimpse of Earth’s pre-late-veneer mantle

“…Bulk rock δ 60 Ni values versus Al 2 O 3 content ( A ), bulk rock Mg# ( B ), Ni concentration ( C ), and Ir N /(Pt N + Pd N ) ( D ) for ~3.8-Ga NUB peridotites. BSE estimate ( 29 , 76 ), and data of post-Archean peridotites, komatiites, eclogites, and basalts from literature ( 9 – 13 , 44 ) are also plotted for comparison. Light and dark blue shaded fields represent the 2SD (±0.03‰) and 95% CI (±0.01‰) for the NUB sample group, respectively.…”

“…S4] reflect the involvement of sulfides and/or alloys, these PGE variations and absolute PGE abundances (fig. S7) are not associated with limited change of δ 60 Ni values, still suggesting that no process such as incongruent melting, immiscibility, crystallization, or metasomatism of sulfides (44,47,48,50) has effectively affected the Ni isotopic compositions of the NUB peridotites. Although samples 208191 and 208196 have a few visible pentlandites (fig.…”

“…More recently, a rather large Ni isotopic fractionation with δ 60 Ni varying from +0.07 to +1.00‰ was recognized in Noril'sk basalts and can be well explained by sulfide-silicate liquid immiscibility during magmatic differentiation where light isotopes preferentially partition into the sulfide liquid (48). In addition, sulfide metasomatism and dissolution have also been proposed to explain lighter Ni isotopic signatures in some peridotite xenoliths (11) and nephelinitic melts (44), respectively. Accordingly, there is no doubt that sulfide is a key phase affecting Ni isotopic compositions in ultramafic-mafic rocks, so its influence must be evaluated.…”

Nickel Isotope Fractionation During Magmatic Differentiation

“…In addition, Sheng et al. (2022) compiled Ni isotopic data of different subducted lithologies and suggested that subducted sedimentary input (because of their low Ni contents), if any, contributed a negligible amount of Ni that can hardly modify the Ni isotopic systematics of the sub‐arc mantle source, while the subducted mafic‐ultramafic lithologies have δ 60/58 Ni values falling within the normal mantle range. Third, due to the immobility of Ni in slab‐dehydrated fluids (Ballhaus et al., 1994), fluid addition is thought to have a negligible impact on Ni isotopes of the melts, as evidenced by the lack of correlation between δ 60/58 Ni and Ba/Th or Ba/La (Figure S2 in Supporting Information ).…”

“…Zhao et al., 2022), respectively. Given the limited Ni isotope fractionation during mantle silicate melting (Klaver et al., 2022; Sheng et al., 2022), we assume that initial basaltic magmas in all settings have an δ 60/58 Ni value of +0.05‰ ± 0.19‰ (2SD), the average of all published data of oceanic basalts (Cameron et al., 2009; Gueguen et al., 2013; Saunders et al., 2022; S.‐J. Wang et al., 2021).…”