Raman spectroscopic study of a garnetite xenolith from Malaita, Southwest Pacific

Abstract

A garnetite xenolith, KC-99-M5, from Malaita Island reported to contain minerals from the mantle transition zone was investigated using micro-Raman spectroscopy and electron probe microanalysis. The xenolith is mainly composed of Ti-bearing pyropic garnet. It contains many amoeboid areas with radiating cracks and veins that suggest fracturing during decompression. The phases in the veins and amoeboid areas are identified as orthopyroxene, clinopyroxene, amphibole, spinel, and plagioclase. High-pressure minerals such as majorite and silicate perovskite were not confirmed in this work. Texture, mineral chemistry, and Raman spectroscopic data indicate that the minerals in the veins and amoeboid areas are the reaction products of primary minerals with the melt from the hosting alnöite magma that penetrated along the cracks.