Isotope geochemistry of basaltic glasses from the Vance Seamounts, a near-ridge seamount chain adjacent to the Juan de Fuca Ridge.

摘要

Volcanic glass from 24 grab-samples from the Vance Seamounts, a chain of seven near-ridge seamounts (NRS) located adjacent to the southern Juan de Fuca Ridge (SJdF), was analysed for Sr, Nd, and Pb isotopic composition. The selected samples show a relatively large range of isotopic compositions (87Sr/86Sr from 0.702473 to 0.702755, 143Nd/144Nd from 0.513048 to 0.513182, and 206Pb/204Pb from 18.12 to 18.82).;The isotopic diversity, seen both within and among seamounts of the chain, is consistent with melt-induced mixing of a heterogeneous mantle source comprised of a depleted mantle (DM) matrix with 'plums' of HIMU(high micro)-like material. The observed isotopic compositions fall outside of previously observed compositional ranges from SJdF and neighbouring NRS lavas, but are consistent with compositions previously observed in lavas from the greater northeast Pacific. The data also support previous, recent melting events of the seamount source components beneath the adjacent SJdF.