Fig. 4
From: Genesis of the columnar joints from welded tuff in Mount Mudeung National Geopark, Republic of Korea
Mt. Mudeung andesite or dacite plotted on the total alkali–silica igneous rock classification diagram. Each symbol represents an average colonnade composition (n = 15–26; see Table 1) from Mt. Mudeung. Rock samples were collected at the Ipseok-dae (unfilled triangles), Seoseok-dae (unfilled diamonds), Gwangseok-dae (unfilled circles), and Chotdae-bong (unfilled rectangles) colonnades. Dotted line indicates the boundary between alkaline and sub-alkaline magmas (Le Bas et al., 1986), and all samples from Mt. Mudeung are plotted within the sub-alkaline field