Isotopic Evidence for Multiple Recycled Sulfur Reservoirs in the Mangaia Mantle Plume. (6th October 2020)

• Record Type: Journal Article
• Authors: Dottin, J. W.; Labidi, J.; Jackson, M. G.; Woodhead, J.; Farquhar, J.
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 21:Number 10(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-10-06
• Subjects: sulfur isotopes -- HIMU -- mantle recycling; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2020GC009081
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: Mangaia, an ocean island in the Cook‐Austral volcanic chain, is the type locality for the HIMU mantle reservoir and has also been shown to exhibit evidence for recycled sulfur with anomalous δ 34 S and Δ 33 S that has been attributed an Archean origin. Here we report bulk S‐isotope data from sulfide inclusions in olivine and pyroxene phenocrysts from one of the previously analyzed and four additional Mangaia basalts to further test for the prevalence of anomalous S in the HIMU mantle source feeding Mangaia. We document compositions that range from −5.13‰ to +0.21‰ (±0.3 2σ), +0.006‰ to +0.049‰ (±0.016 2σ), −0.81‰ to +0.69‰ (±0.3 2σ) for δ 34 S, Δ 33 S, and Δ 36 S, respectively. These data extend the range of measured compositions and suggest S‐isotope heterogeneity in the HIMU mantle source at Mangaia. We show that S‐isotope compositions of bulk sulfide in olivine is not in isotopic equilibrium with bulk sulfide in pyroxene from the same samples and that samples from a confined area (M4, M10, M12, and M13) in the northern central part of the island show a distinct covariation for δ 34 S and Δ 33 S. This isotopic variation (forming an array) suggests mixing of sulfur from two sources that were captured at different stages of crystallization by phenocrysts in the Mangaia HIMU sulfur endmember. Plain Language Summary: The sulfur isotope composition of the mantle is heterogenous from crust formation and recycling continental and oceanic crust. Basalts, from an intraplate volcanic hotspot volcano in the Pacific Ocean, Mangaia, show isotopic evidence for hosting Archean‐related sulfur that is sourced from a recycled oceanic crustal component. The prevalence of this Archean‐related sulfur in the plume source that feeds Mangaia is not well constrained. In this work, we present sulfur isotope data on sulfur from minerals that crystallized deep in the magma chamber and identify a new, potentially younger, recycled sulfur source that demonstrates the diversity of materials mixing in the magma chamber prior to eruption. Key Points: We report bulk S‐isotope compositions of sulfide in melt inclusions of olivines and pyroxenes from Mangaia Isotopic disequilibrium in a single sample records a process of trapping various compositions during magma mixing Data collected identify a new, potentially young, recycled component with negative δ 34 S and slightly positive Δ 33 S in HIMU source