Cambrian metamorphic complexes in Tasmania: tectonic implications

• Published in: Australian Journal of Earth Sciences
• Main Authors: Meffre, S, Berry, RF, Hall, M
• Format: Article in Journal/Newspaper
• Language: English
• Published: Blackwell Science 2000
• Subjects: Earth Sciences; Geology; Tectonics; Victoria Land; Antarc*; Antarctica
• Online Access: https://doi.org/10.1046/j.1440-0952.2000.00825.x; http://ecite.utas.edu.au/20590

Cambrian metamorphic complexes containing amphibolite- to eclogite-grade rocks are present throughout western and northwestern Tasmania. These complexes contain mostly quartz-albite-biotite schists, garnet-quartz-albite-biotite schists and mafic amphibolite senses (up to 1 km long). The chemistry of these rocks is similar to unmetamorphosed. Late Neoproterozoic tholeiitic basalts and continental-derived siliciclastics. A few rocks in the metamorphic complexes have compositions that are transitional between the amphibolites and the schists, representing metamorphosed volcaniclastic rocks formed by mixing between mafic and siliciclastic sources. The rocks in these complexes were probably located on the edge of a thin Late Neoproterozoic passive margin that was partially subducted during a Cambrian arc-continent collision and uplifted during post-collisional crustal re-equilibration. The metamorphic condition, age and chemistry of both the schists and the amphibolites resemble those of metamorphic complexes in North Victoria Land in Antarctica. However, the structural setting of these complexes differs from those in Tasmania. Comparisons of the Tasmanian and North Victoria Land Cambrian structures and lithologies with those from more recent arc-continent collisions worldwide show that both are compatible with a model involving east-dipping subduction of a passive margin beneath an intraoceanic island arc. The differences between the two areas probably arise from differences in the geometry of the margins and the thickness of the passive-margin sediments.