The structure of Kangaroo Island, South Australia: Strain and kinematic partitioning during Delamerian basin and platform reactivation

Geochemistry and geochronology of the Rathjen Gneiss: Implications for the early tectonic evolution of the Delamerian Orogen

“…The S 1 subhorizontal foliation and associated L 1 north–south‐trending stretching lineations found in the Rathjen Gneiss and in the enclosing migmatitic metasediments, provide interesting insight into the tectonic complexity of the belt. As discussed earlier, this fabric is kinematically distinct from fabrics resulting from subsequent upright folding during east–west shortening and which are probably associated with the development of westward‐verging thrust‐stacking in the more external lower grade parts of the belt (Jenkins & Sandiford 1992; Flöttmann et al 1994, 1995). The possibility that these fabrics are due to an early phase of north–south extensional deformation has been argued by Oliver and Zakowski (1995).…”

“…Emerging from this study is an interpretation of a more complex structural evolution than the traditional view of east–west convergence and shortening (Flöttmann et al 1994, 1995). Both structural and magmatic histories imply the juxtaposition of extensional and compressional tectonic regimes over relatively short time intervals.…”

“…As simple closure of a pre‐Delamerian rift from direct reversal and convergence on the original extensional vectors would be expected to return South Australian autochthonous basement from the east, the change in detrital zircon ages of Kanmantoo basin fill must support the translation of a new younger crustal source terrain from the southeast. A combination of some element of oblique convergence on this boundary, coupled with variable geometry from north to south, may lead to periodic local transition from extension to compression perhaps indicative of a transpressional regime as suggested by Flöttmann et al (1995). Indeed, such a scenario would provide an ideal environment to produce variations in the interaction of mantle‐derived magmas with, and fractionation in, the crust required to yield the variety of granite chemistries observed in the southern Adelaide Fold‐Thrust Belt.…”

Expedition 369 summary

“…However, the change in structural configuration appears to occur along an east-west trend that would project east to the Kangaroo Island Shear Zone (Fig. 15), which delineates the Proterozoic Gawler Craton from the Early Palaeozoic Adelaide Fold-Thrust Belt (Flöttmann et al, 1995). The variation in structural configuration within the Duntroon Sub-basin may thus be associated with changes in the underlying basement, from the Gawler Craton in the north to the Adelaide Fold-Thrust Belt in the southeast.…”