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Ocean island basalts (OIBs) and associated sedimentary units form part of the ocean plate stratigraphy accreted onto island arcs or continental arcs and provide important insights into convergent margin processes. Here, we investigate some of the typical localities of Sanpozan, Shirakidani, and Kamiananai within the Chichibu composite belt in Kochi, SW Japan, where the accretionary complexes incorporate OIBs and sedimentary rocks that preserve the travelogue of an oceanic plate from a mid‐oceanic ridge (MOR) to subduction zone. We present petrology and geochemistry, as well as zircon U–Pb geochronology and REE data of the accreted OIB and sedimentary formations from Sanpozan, Shirakidani, and Kamiananai. The OIBs are enriched in LILE and LREE and depleted in HREE. The chondrite‐normalised REE patterns of zircon grains from OIBs and sedimentary rocks display LREE depletion and HREE enrichment, sharply positive Ce and Sm anomalies and negative Pr and Eu. LA‐ICP‐MS U–Pb geochronology of zircon grains from the OIBs shows three major populations with 206Pb/238U mean ages of 164–456, 724–955, and 1,638–2,202 Ma. The diverse ages suggest heterogeneous recycled source components in the plume‐related upwellings that generated the OIBs, as well as different times of formation and accretion of the Palaeozoic and Mesozoic oceanic islands. The dominant population of zircon grains from the sedimentary units shows 206Pb/238U mean ages of 147 and 288 Ma and indicate a major change in the provenance regime with subduction and the disappearance of older arcs attesting to the destruction of continental crust in convergent margins. [ABSTRACT FROM AUTHOR]

Arc volcanic rocks are important products of the subduction factory in convergent plate margins and contribute significantly to crust building in the evolving Earth. Southwest Japan provides a window to gain insights into the ongoing subduction-related processes and the early stages of crust building. In this study, we investigate a suite of volcanic rocks from the central segment of the Setouchi volcanic belt (SVB) including dacites and andesite from northeast Shikoku island in southwestern Japan based on petrologic, geochemical, zircon U--Pb, REE (rare-earth element), and Lu--Hf analyses. The dacites and andesite from this region are peraluminous, medium-K, and calc-alkalic, with LREEs (light rare-earth elements) enrichment and depleted in HREEs (heavy rare-earth elements) and HFSEs (high field-strength elements). Two groups of zircon grains occur in these volcanic rocks as revealed from U--Pb studies. The older magmatic zircon grains are of late Cretaceous age and show typical oscillatory zoning yielding 206Pb/238U age peaks at 83.6 Ma with dominantly negative εHf(t) values (−3.7 to +0.9), indicating older reworked crustal sources. The second group is represented by thin elongated prismatic grains with banded structure, which yield 206Pb/238U age peaks at 13.8 Ma and displaying more positive εHf(t) values (+2.4 to +7.7), indicating juvenile sources. A compilation and comparison of the available geochemical and geochronological data on the volcanic suites in the SVB reveal a common source for the coeval island-arc volcanic rocks (andesite-dacites-rhyolite) and HMA (high magnesium andesites). Compared with the HMA, the other volcanics are more evolved through crustal contamination and fractionation. [Display omitted] • Dacites and andesite from SVB are calc-alkalic and peraluminous. • Zircon morphology and U--Pb ages constrain the timing of volcanism at 13.75 Ma. • Zircon xenocrysts of ca. 83 Ma from Ryoke basement suggest crustal interaction. • Positive εHf(t) values suggest juvenile arc magmatism. • Coeval HMA and non-HMA volcanism correlated to source heterogeneity. [ABSTRACT FROM AUTHOR]