Petrogenesis of an Early Cretaceous lamprophyre dike from Kyoto Prefecture, Japan: Implications for the generation of high-Nb basalt magmas in subduction zones

We studied a 107 Ma vogesite (a kind of lamprophyre with alkali-feldspar > plagioclase, and hornblende ± clinopyroxene ± biotite) dike in the Kinki district of the Tamba Belt, Kyoto Prefecture, SW Japan, using petrography, mineralogy, K–Ar ages, and geochemistry to evaluate its petrogenesis and tectonic implications. The dike has the very specific geochemical characteristics of a primitive high-Mg basalt, with 48–50 wt.% SiO2 (anhydrous basis),...