FEATURES AND GENESIS OF TERRESTRIAL BASALTIC VITROCLASTIC ROCKS IN NORTHERN HEBEI

This paper introduces the petrological features of basaltic vitroclastic rock in the Early Cretaceous Dabeigou Formation in northern Hebei. The rock is higkly vitrified and the cements are dominated by carbonates, chlorite and ferruginous material. Its oxidation coefficient is lower than that of normal basalt. At the base of the formation there occur basaltic vitriclastic agglomerate and vitroclastic breccia; upward vitroclastation weakens, forming ball and pillow basalt; still upward the rock grades to normal basalt. The vitroclastic degree depends upon the depth and temperature of waters, the magnitude and replenishment amount of lava flow, velocity of lava flowage and the amount of volatile components in molten magma.