Eruption of basaltic lavas at hotspot volcanoes and oceanic plateaus has been considered to be a manifestation of buoyant plumes ascending through the mantle. The chemical compositions of such plume-related basalts may therefore provide us with key insights into the activity of mantle plumes, including ordinary ones and superplumes, and styles of mantle convection. Isotopic and major-element compositions of ocean island basalts (OIB) strongly suggest that recycling of subducted crustal materials plays an important role in the genesis of OIB. However, isotopic diversity of OIB seems to be too homogeneous to be generated from subducted materials which are expected to have extremely heterogeneous compositions owing to variability in their original compositions, modification history during subduction modification, and mantle residence times. Understanding the origin of the enriched components (EM1, EM2, and HIMU), which characterize the isotopic diversity of OIB, requires detailed knowledge of the dynamic and rheological behavior of mantle and crustal materials under mantle conditions as well as of their chemical characteristics. Major-element compositions of OIB suggest that OIB are generated from peridotite-pyroxenite heterogeneous mixtures at temperatures higher than the normal mantle geotherm. In contrast, major-element compositions of oceanic plateau basalts are similar to those of mid-oceanic ridge basalts (MORB), requiring no excess temperature or significant amounts of extra components such as pyroxenite in their sources. These observations imply that OIB are generated from relatively small hot plumes during normal periods in the Earth's history, whereas oceanic plateau basalts are generated from high-flux and not-hot plumes that are forced to ascend through the upper mantle by flushing of subducted slabs down to the lower mantle. This in turn brings into question the conception that superplumes come from the bottom of the mantle with abnormally high temperatures. © 2007 Springer.