Two textural types of felsic fragments are recognized in pyroclastic (tuffite) dikes at Kawakami in Nara Prefecture, SW Japan: one is porphyritic, and the other is aphyric. Porphyritic fragments are welded and their glassy margins are deformed. An aphyric fragment in a boulder is lensoidal in shape, indicating ductile deformation. Matrix surrounding those fragments includes small lensoidal or amoeboidal glasses, and shows a eutaxitic texture. All of these observations indicate that the felsic fragments and matrix were hot at the time of dike emplacement, and that the fragments were juvenile. K-Ar and fission-track datings applied to the porphyritic fragment resulted in ages of 13.7±0.7 Ma (sanidine) and of 16.0±0.6 Ma (zircon), respectively. Those ages from the juvenile fragment, circular distribution of the dikes, and fiammes observed in boulders of densely welded tuff suggest that the tuffite dikes occurred as feeders similar to those associated with caldera- or cauldron-forming eruptions around 14-16 Ma.