Modification of Lithospheric Mantle by Melts/Fluids With Different Sulfur Fugacities During the Wilson Cycle: Insights From Lesvos and Global Ophiolitic Peridotites

Abstract

As remnants of past oceanic lithosphere, ophiolites could potentially record the life cycles of ocean basins from their rift-drift and seafloor spreading to subduction initiation and terminal closure (Dilek & Furnes, 2011Xu et al., 2020;Vannucchi et al., 2020). Different types of ophiolites formed in various tectonic environments, such as ocean-continent-transition (OCT), mid-ocean-ridges (MOR), and supra-subduction-zone settings (SSZ; Dilek & Furnes, 2014 and references therein), are believed to represent different

Mineralogy, Geochemistry and Tectonic Setting of the Raobazhai Ultramafic Complex, North Dabie

“…Typical primitive mantle residues were not subjected to strong secondary overprinting and, overall, showed a strong positive correlation between the Pd/Ir ratio and silicate melt extraction index (such as Al 2 O 3 ) [41]. The Pd/Ir of the Raobazhai harzburgites was higher than that of the melting model, which may be due to the metasomatism of the Pd-rich Cu-Ni sulfide melt to the Pd-depleted residual mantle (Figure 10c), which is similar to the Yarlung-Zangbo ophiolite [43,44] in Tibet and Lesvos [45]. The Raobazhai chromite harzburgites (samples RBZ-40b and RBZ 42) showed obvious Pt-Pd differentiation with a higher Pt/Pd ratio (Figure 10d).…”

“…As the IAB may impact the entire fore-arc domain, a similar metasomatism will be formed if the continental core complex (CMCC) occurs where the ocean meets the continent (Figure 12, 3 ). [45]). OOST: out-of-sequence thrust; IAB: island arc basalt.…”

“…Figure12. Tectonic model illustrating the possible environment of Raobazhai ultramafic complex (modified after[45]). OOST: out-of-sequence thrust; IAB: island arc basalt.…”

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

“…S2), especially for the sharp anomalies of Ru and Pd, the NUB peridotites are in notable contrast to the ranges of mantle-wedge peridotites. Mantle peridotites formed in subduction zones typically have relatively lower Os N /Ir N and more radiogenic 187 Os/ 188 Os ratios owing to high- f O 2 metasomatism and slab-derived contamination ( 34 ). The HSE systematics of the NUB peridotites obviously do not fall into this category (fig.…”

“…Bulk-rock major and trace elements, mineral major elements, HSEs, and Re-Os isotopic analysis Analytical methods for HSEs (here including Re + five PGEs: Os, Ir, Ru, Pt, and Pd) and Re-Os isotopes (analyzed at CUGB) are described in detail in (34), while those for some related bulk-rock major and trace elements (analyzed at Washington State University; table S1), as well as mineral (e.g., olivine, amphibole, and chromite) major elements (analyzed at University of Copenhagen; table S3) involved in this work, are described in (74). The HSE concentrations and 187 Os/ 188 Os ratios of repeatedly measured reference materials UB-N (serpentinized lherzolite) and BHVO-2 (table S4) are also consistent with their accepted values (75) within uncertainties.…”