Geology and petrology of part of the Archaean inlier north-east of Yankalilla on the Fleurieu Peninsula

Abstract

The Archaean inlier to the east of Yankalilla on the Fleurieu Peninsula forms the core of an overturned anticlinal structure whose limbs and hinge line dip and plunge to the south-east. The fold is delineated by the overlying unconformable Proterozoic and Cambrian sediments.

There is evidence of a sheared boundary along the north-western edge of the inlier. The schistosity and layering of the basement schists, quartzofeldspathic schists, gneisses and feldspar gneisses parallels the axial plane structure of the anticline.

The basement has possibly undergone intense deformation before the deposition of the Adelaidean in the form of tight isoclinal folding. It is intruded by amphibolite dykes and pegmatites.

The metamorphic grade has reached at least upper amphibolite facies and has been retrograded to Greenschist facies.