Volcanic evolution and magma diversity of Akita-Komagatake volcano, northeastern Japan: Refining tephra–edifice correlations using multi-proxy petrological data

High-resolution reconstruction of volcanic edifice evolution is crucial for understanding magma processes and eruptive mechanisms. Establishing robust correlations between tephra units, which provide temporal constraints, and proximal edifice deposits is key to this reconstruction. Here, rather than correlating tephra and edifice deposits solely on the basis of major-element similarity, we first identified the magma type of each tephra unit based on the established tephra stratigraphy and clarified its temporal variation. We then assigned previously uncorrelated edifice deposits to specific tephra units using magma-type affinities, thereby constructing a consistent stratigraphy for the volcanic edifice. Magma types were distinguished using multiple petrological parameters, including whole-rock major and trace element compositions and Sr–Nd isotopic ratios. Applying this approach to Akita-Komagatake volcano in Northeast Japan arc, we reassessed its volcanic evolution from the late Pleistocene to the present. Thirteen tephra units were classified into five magma types based on Sr–Nd isotopic compositions and large-ion lithophile element abundances (K, Rb, Ba). Edifice deposits were divided into seven eruptive stages and substages according to vent locations, eruption styles, and stratigraphic relationships, each associated with a characteristic magma type. This integrated correlation enabled a refined reconstruction of the chronology, erupted volumes, and eruption styles of each stage. A revised magma-discharge step diagram integrating both tephra and edifice deposits reveals a three-stage evolutionary sequence: (1) an initial explosive phase with large magma discharge and caldera formation, (2) a subsequent phase dominated by vigorous effusive eruptions that built the volcanic edifice, and (3) a final stage of declining eruption rate. Temporal changes in magma types across these phases suggest stepwise reorganization and progressive maturation of the magma plumbing system in concert with edifice growth.