Shear sense indicators in striped bedding-veins

Striped bedding-veins are veins that lie subparallel to bedding and have an internal layering or lineation at a small angle to the veins' long axis. T hey form during bedding-parallel slip and can be used as shear sense indica tors. Solid inclusion trails produce the visible internal layering or linea tion and track the opening direction of the veins. Elongate quartz crystals however can be oriented at an angle of up to 80 degrees to the opening dir ection, are non-tracking, and contain almost no information on the shear se nse. The striped bedding-veins can be separated into three types according to the geometry of their internal segmentation. Veins of type B opened para llel to jogs oriented at a low angle to bedding, veins of type J opened par allel to jogs oriented at a high angle to bedding and veins of type O opene d orthogonal to bedding and jogs. Striped bedding-veins of types B and J co ntain crack-seal inclusion bands and displacement parallel inclusion trails . Striped bedding-veins of type O feature only crack-seal inclusion bands. The example of striped bedding-veins presented in this paper from the Orobi c Alps of Italy belongs to type B. The lineation in the veins and the orien tation of the inclusion bands and inclusion trails, as well as the orientat ion of steps in the vein wall, can be used to determine the sense of shear and the direction and amount of Vein opening or bedding-parallel slip. (C) 2000 Elsevier Science Ltd. All rights reserved.