A suite of amphibole-bearing ultramafic and mafic xenoliths representing the crust-mantle boundary was sampled in the northern segment of the Kamchatka arc. These nodules exhibit low equilibration temperatures at elevated pressures suggesting relatively cold conditions at Moho depths, which are uncommon in modern island arcs. A model including successive stages of subduction initiation, subduction cessation resulting in cooling of the lithospheric wedge, followed by intra-arc rifting due to upwelling of astenospheric diapirs is proposed to explain the observed textural, petrologic and chemical characteristics of sampled rock assemblage. ¿ American Geophysical Union 1993