Abstract

AbstractIdentification of the nature of recycling crustal materials in the sources of large igneous provinces (LIPs) is crucial for understanding compositional heterogeneity of the deep mantle. To provide new constraints on this issue, here we reported high‐precision zinc isotope data on picritic and basaltic lavas from the Emeishan LIP, SW China. Using olivine‐melt Mg‐Fe equilibrium and log (incompatible elements)‐log (MgO) systematics, the parental magma of picritic lavas is estimated to have a MgO content of 21.8 wt.%. All picrites and basalts analyzed have δ66ZnJMC 3‐0749L values of ~0.30‰, which is heavier by ~0.14‰ than that of the terrestrial mantle (0.16 ± 0.05‰, 2s.d.). Olivine and clinopyroxene phenocrysts in picrites are isotopically lighter by ~0.15‰ than the whole rocks, and a negative correlation between Zn and MgO contents for picrites is observed, indicating that olivine accumulation could lower Zn contents and δ66Zn values of the magmas. Taking this into account, the parental magma of picrites has a δ66Zn value of 0.33 ± 0.04‰ (2s.d.). This value is significantly higher than that of other large‐degree partial melts derived from the mantle (e.g. Archean komatiites and the Baffin Island picrites; ~0.20‰), which requires addition of recycled crustal materials into the mantle sources. Modeling suggests that this difference can be best explained by partial melting of a hybridized mantle source containing ~15% recycled basaltic oceanic crust. Our data also show no evidence for recycled marine carbonates into the source of Emeishan LIP and thus possibly into the Earth's deep mantle (>660 km).

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call