Hybrid Metaandesites of Khangar Volcano, Sredinny Range, Kamchatka: Product of Interaction between Basaltic Magma and Basement Granitoids?

Unique rocks were found in the southern part of the Khangar caldera at the exposure of basement granodiorites. Their bulk composition corresponds to high-magnesia andesite (SiO 57-63 wt %, MgO 4-8 wt %, KO 1.4-2 wt %). The rocks consist of quartz, oligoclase, and olivine phenocrysts and a propylitic mineral assemblage (albite, calcite, chlorite, and epidote). The large phenocrysts are similar in composition to granodiorite minerals (oligoclase An, quartz, and biotite). The olivine phenocrysts contain melt inclusions of basaltic composition (SiO 45-48 wt %, MgO 7-10 wt %) with high KO content (up to 1.5 wt %). We supposed that these rocks were produced by interaction between basaltic melt and silicic intrusive material.