Petrology of the 1952 Eruption and Ancient Lava and Pyroclastic Flows of Krenitsyn Peak Volcano, Onekotan Island, Kuril Arc, Russia

Krenitsyn Peak is one of the two active volcanoes on Onekotan Island (Greater Kuril Ridge). The inaccessibility of the island, along with the volcano being situated within a sizeable (7 km in diameter) and cold (3.7 °C) caldera lake, has led to minimal research on the area. We present the first detailed characterization of the rocks from the only historical eruption of Krenitsyn Peak (November 1952) and a brief description of the ancient lava and pyroclastic density current (PDC) deposits that make up the building of the volcano. The 1952 eruptive products are represented by two-pyroxene andesites (59.2–63.3 wt.% SiO2), and the older lava and pyroclastic flow rocks consist of two-pyroxene andesites and dacites (62–67.6 wt.% SiO2). Almost all samples belong to the calc-alkaline, medium-K, and medium-Fe series, and the pumiceous lapilli from the 1952 eruption fall into the low-Fe series. The minerals exhibit signs of magma mingling, including relic high-Ca (up to An92) plagioclase cores with signs of dissolution and recrystallization, and oscillatory-zoned pyroxene.