Conditions of diamond growth: a proton microprobe study of inclusions in West Australian diamonds

Abstract

Crystalline primary inclusions in diamonds from the Argyle and Ellendale lamproites have been analyzed for Mn, Ni, Cu, Zn, Ga, Pb, Rb, Sr, Y, Zr, Nb, Ta, Ba and Mo by proton microprobe. Eclogite-suite inclusions dominate at Argyle and occur in equal proportions with peridotite-suite inclusions at Ellendale. Eclogitic phases present include garnet, omphacitic clinopyroxene, coesite, rutile, kyanite and sulfide. Eclogitic clinopyroxenes are commonly rich in K and contain 300-1060 ppm Sr and 3-70 ppm Zr: K/Rb increases with K content up to 1400 at 0.7-1.1% K. Rutiles have high Zr and Nb contents with Zr/Nb=1.5-4 and Nb/Ta ∼16. Of the peridotite-suite inclusions, olivine commonly contains > 10 p..