Quartz veining in simply folded arenites, Cape Liptrap, southeast Victoria, Australia

Quartz veins in a simply folded sequence of interbedded arenite and mudstone at Cape Liptrap, Victoria, indicate the importance of the local stress fields in controlling the orientation of quartz veins in the folding of a multilayered sequence. Because most of the quartz veins formed by hydraulic extension, the effective stress field at any point closely constrained the orientation of the veins. The veins formed in sets consisting of many subparallel, dimensionally comparable, almost synchronously formed quartz veins. Planar sets aligned either (sub) parallel or (sub) normal to the fold axis, formed preferentially in the hinge zone, whereas single, en echelon sets oriented (sub) normal to the fold axis formed on the limbs. Most sets oblique to the fold axis are present on the limbs of folds and, from cross-cutting relationships, appear to have formed prior to fold formation. Silica depletion in the quartz arenites and high fluid to rock ratios, together with high uniform oxygen isotope results for the quartz veins (18.4 ± 0.4%o), are consistent with the silica-rich fluid, from which the quartz veins were derived, being derived within the enclosing sedimentary pile and transported via mainly advective processes to the sequence being folded