Fig. 3

Schematic structure of a tremolite–calcite vein (according to the model of Bucher 1998). Photographs of thin sections highlight the longitudinal variation of the vein structure. The lowest two thin sections represent one half of the vein. Original height of thin sections is 23 mm. The different microtexture and abundance of tremolite (green) and calcite (colourless) accounts for the zoned, rhythmic banding of the vein. r.f. reaction front, f.w. fracture wall, i.b. inner band (see text for further explanation)