Mantle-melt evolution (dynamic source) in the origin of a single MORB suite: A perspective from magnesian glasses of Macquarie Island

Abstract

The effects of source composition and source evolution during progressive partial melting on the chemistry of mantle-derived mid-ocean ridge basalt (MORB) melts were tested using a comprehensive geochemical and Sr-Nd-Pb isotopic dataset for fresh, magnesian basaltic glasses from the Miocene Macquarie Island ophiolite, SW Pacific. These glasses: (1) exhibit clear parent-daughter relationships; (2) allow simple reconstruction of primary melt compositions; (3) show exceptional compositional diversity (e.g. K2O/TiO2 0.09-0.9; La/Yb 1.5-22; 206Pb/204Pb 18.70-19.52); (4) preserve changes in major element and isotope compositions, which are correlated with the degree of trace element enrichment (e...