Variations and Origins of Peridotite Xenoliths from Tsubai Island: Implications from Mineral Trace Element Compositions and Whole-Rock Chemical Analysis

Abstract

It is suggested that a huge superplume exists under the Polynesian region of the South Pacific, and the peridotite xenoliths in this area may possess distinct material characteristics compared to those in other regions. This study analyses the trace element composition of minerals and the whole-rock chemical composition of peridotite xenoliths found on Tubuai Island, a volcanic island in this region. Together with the petrography and the major elemental composition of minerals, we will discuss the characteristics and origin of mantle materials. Variations in the trace element composition of clinopyroxene show higher incompatibility elements, but the overall geochemical characteristics of the samples are believed to reflect an origin from shallow oceanic lithosphere. Regarding the rock texture, major elemental composition, and estimated temperature and pressure, it is suggested that there was a reaction with melt after partial melting. The presentation will include the analysis results of whole-rock chemical composition and systematically compare the material characteristics of the lithosphere in this region with those of other regions and other volcanic islands within the same area.