Publication Date:
2001-01-01
Description:
In the Huckitta region of the eastern Arunta Inlier, central Australia, two terrains with distinct metamorphic histories are separated by a zone of sinistral strike-slip mylonitic deformation and reworking, the Entire Point Shear Zone (EPSZ). To the south of the EPSZ, in the Harts Range Group, Ordovician (c. 470 Ma) intraplate granulite facies metamorphism (c. 800{degrees}C, 8-10 kbar) was followed by decompression to c. 7 kbar. In contrast, the Kanandra Granulite, to the north of the EPSZ, is characterized by Palaeoproterozoic high-grade metamorphism at 770-850{degrees}C and 5-7 kbar, followed by inferred near-isobaric cooling. Juxta-position of these terrains along the EPSZ occurred at upper amphibolite facies conditions (700{degrees}C, 7 kbar), and resulted in extensive reworking of the Kanandra Granulite. Monazite growth within EPSZ mylonites is dated at 445 {+/-} 5 Ma, whilst a garnet amphibolite gives a Sm-Nd isochron age of 434 {+/-} 6. The timing of this deformation is broadly coincident with the inferred onset of south-vergent compressional deformation in the Harts Range region to the south. This suggests that juxtaposition of the Ordovician granulite terrain with the surrounding Proterozoic terrains occurred during intraplate sinistral transpression in the late Ordovician. Further reworking of the Kanandra Granulite occurred at mid-amphibolite to greenschist facies conditions, during north-vergent mylonitic deformation that exhumed the Ordovician high-grade terrain during the 400-300 Ma Alice Springs Orogeny. Although this zone of Palaeozoic reworking is 〈5 km wide, it forms the northern margin of Palaeozoic high-grade intraplate deformation and represents a major tectonic boundary in central Australia.
