Sample photos and description of rocks and sediments from petit-spots in the northwestern Pacific

We present sample photos of rock and sediment samples from petit-spots and their description. The samples were collected using deep-submergence vehicle (DSV) Shinkai 6500 and its mother ship, research vessel (RV) Yokosuka during YK20-14S and YK21-07S cruises. The rock samples are basalt and peperite, a reaction product between magma and wet sediment. They at times include mantle xenoliths. The cruises were designed to elucidate modification process of the surface condition and deep lithospheric mantle of the old Pacific plate just before its subduction beneath the Japan arc.