The volcanoes of the northern lzu-south-cental Honshu and northeastem Honshu arcs, Japan, occur in a region where vmiables such as age, conposition, and nature ofthe sediment cover oftle subducting plate are relatively uniform. In this study, v/e attempt to isolate some ofthe variables associated with suprasubduction zone (SSZ) magma genesis, in order to provide insight into ttre nature of sources and petrogenetic processes. The chemical compositions of selected parental and evolved magmas in fifteeu Plio-Pleistocene centers along the strike ofthe volcanic front allow us to assess tle significance of over-riding lithospheric input for SSZ magmatism. These volcanoes are distributed across a number of major terrane boundaries, including the lithosphere-penetrating Tanakura Tectonic Line. Conpositions range from basalt to rhyolite, with a preponderance of basaltic andesite and andesite; an exception is basalt-dominated Fuji. Most basalts are signiffcmfly fractionate4 with low MgO (< 7 wtTo), Mg# $0, and low Ni (d0 ppm). Significant differences among volcanic suites are established on the basis of isotopic@ b, Sr, and Nd), major-and trace-element data-The predominant source of these ma€ mas is a relatively refractory (compared to mid-oceaa ridge basalt) mantle-wedge are4 with subchondritic MZr and ZrlIIf. A number of volcanoes also havelow ZrN (< MORB), but several have both elevated hN (> 3) and Dy/Yb, indicative of gamet involvement in their gercsis. The Nd and Sr isotope ratios also indicate regional variations in chemical composition of the source (s)(ong-term depleted to enriched). Pb isotopic data are distinctive in northern Honshu, with elevated 48Pb/2I/. Pb afi, NTPbPePb at specific 2n6Pb2oaPb (south versas north of the Tanakura Tectonic Line), are collectively elevated above the Northem Hemisphere Reference Line (and lzu-Mariana arcs), appear similax to portions of the Philippines and Tertiary basalts of eastern Asia and probably reflect an Asian lithospheric heritage. The combined trace-element and isotope geochemistry of parental basalts distinguish different domains within the Izu-Bonin, central and northeastern Honshu arcs. The ultimate cause of these is most likely multicomponent, and some crustal assimilation is higbly probable. However, tlese domains may in some paxt represent nagma interaction with a subcontinental lithosphere dominated by Indian-Ocean-type mantle, or alt€ matively, derivation from an Indian-Ocean-type asthenosphere. The correlation of some magma compositional characteristics with nature of the basement terrane shows that the lithosphere plays a subtle but significant role in determining parental island-arc basalt chaxacteristics. The longevity and character ofthe continental lithosphere in Asian margin arc systems, and its interaction with asthenosphere-derived melts, is a1 imFcntant process in island-arc basalt genesis.