Geochemical characteristics of petit-spot volcanoes on the western Pacific Plate

Abstract

Petit-spot, the fourth kind of universal volcanic activity on the Earth after island arcs, mid ocean ridges, and hotspots, is expected to originate from the lithosphere-asthenosphere boundary. Therefore, the study of petit-spot basalts potentially provides information about the nature of the asthenosphere as a fundamental theory of plate tectonics. In this study, the analysis of major and trace element compositions, Sr, Nd, and Pb isotopic ratios, and Ar-Ar datings are performed for western Pacific petit-spot volcanoes to investigate the chemical characteristics of upper mantle below the oldest portion of the Pacific Plate. We report the nature of melting source of the petit-spot magmas on the basis of their geochemistry and some modelled compositions of partial melt from carbonated materials.