Structural Controls on Shallow Cenozoic Fluid Flow in the Otago Schist, New Zealand

Figure 4

Photos from Akatore Creek (left column) and Bruce Rocks (right column). (a) Three main sets of exhumation joints are mutually intersecting at Akatore Creek. Spacing of joints varies between a few centimetres (in this photo) and a few metres (Figure 3). (b) One main set of steeply N-dipping joints at Bruce Rocks cuts across the prominent metamorphic foliation. (c) Reactivation of joint sets 1 and 3 has formed a carbonate-filled dilational jog. Joint set 2 is not reactivated in this case. (d) Reactivation of joints at Bruce rocks produce tabular layers of orange, carbonate-cemented fault breccias. (e) Formation of a rhomb-shaped carbonate-filled mosaic breccia at Akatore Creek, by reactivation of joint sets 1 and 2. (f) A relatively large fault at Bruce Rocks is surrounded by an orange, carbonate-bearing alteration zone. (g) Rhomb-shaped fault breccia at Akatore Creek containing fragments of calcite veins. (h) Polished hand specimen of fault breccia from Bruce Rocks, containing rotated angular fragments of Otago Schist.