Abstract:
Structures related to ductile siMple shear parallel to
the Bankf ield-Tonbill Fault, define a 5km wide zone, the
Barton Bay Deformation Zone. Structures present within this
zone Include; simple shear fabrics S, C and C , asymmetric Z
shaped folds with rotated axes, boudinage and pinch and swell
structures and a subhorlzontal extension llneation.
The most highly deformed rock is a gabbro mylonite which
occurs in the fault zone. The deformation of this gabbro has
been traced in stages from a protomylonite to an ultramylonite
In which feldspar and chlorite grainslze has been reduced from
over 100 microns to as little as 5 microns.
Evidence from the mylonite and the surrounding structure
indicates that deformation within the Barton Bay Deformation
Zone is related to a regional simple shear zone, the
Bankf ield-Tombill Fault. Movement along this shear zone was
in a south over north oblique strike slip fashion with a
dextral sense of displacement.
