High-grade reworking of Proterozoic granulites during Ordovician intraplate transpression, eastern Arunta Inlier, central Australia

Abstract

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°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°C and 5-7 kbar, followed by inferred near-isobaric cooling. Juxtaposition of these terrains along the EPSZ occurred at upper amphibolite facies conditions (700°C, 7 kbar), and resulted in extensive reworking of the Kanandra Granulite. Monazite growth within EPSZ mylonites is dated at 445-4-5

Detrital zircon provenance constraints on the evolution of the Harts Range Metamorphic Complex (central Australia): links to the Centralian Superbasin

“…Given its age, the older, least tightly constrained overgrowth population may reflect zircon growth in the quartzite at or before the peak of the Larapinta Event. The younger age group is younger than the accepted age of the Larapinta Event and is within error of the age of earliest deformation related to the beginning of the Alice Springs Orogeny (c. 445 Ma; Mawby et al 1999;Scrimgeour & Raith 2001). Further work is required to understand the growth history of Ordovician zircon in the quartzite.…”

“…In the deepest structural levels, subsequent decompression-cooling to c. 6 kbar and c. 700 8C (Miller et al 1997;Mawby et al 1999) was associated with the development of recumbent, mylonitic shear fabrics that formed during NE-SW-directed tectonic transport (Hand et al 1999b;Mawby et al 1999), and the emplacement of basaltic dykes (Hand et al 1999b). This association was interpreted by Hand et al (1999a, b) as resulting from extensional tectonics, and was terminated at c. 440 Ma, when the region underwent SW-directed thrusting (Mawby et al 1999) and local strike-slip shearing (Scrimgeour & Raith 2001) related to the beginning of the Alice Springs Orogeny. The Entia Gneiss Complex and Harts Range Metamorphic Complex were locally and episodically reworked at amphibolite grade during the Alice Springs Orogeny (Hand et al 1999a;Mawby et al 1999;Scrimgeour & Raith 2001).…”

“…This association was interpreted by Hand et al (1999a, b) as resulting from extensional tectonics, and was terminated at c. 440 Ma, when the region underwent SW-directed thrusting (Mawby et al 1999) and local strike-slip shearing (Scrimgeour & Raith 2001) related to the beginning of the Alice Springs Orogeny. The Entia Gneiss Complex and Harts Range Metamorphic Complex were locally and episodically reworked at amphibolite grade during the Alice Springs Orogeny (Hand et al 1999a;Mawby et al 1999;Scrimgeour & Raith 2001).…”

“…This event was termed the Larapinta Event by Hand et al (1999b) to emphasize the temporal relationship between metamorphism and deposition of the Ordovician Larapinta Group in the Amadeus Basin. The orientation and movement sense of peak-metamorphic fabrics, the relationship between metamorphism and syn-to post-peak mafic dykes, and the possibility of synmetamorphic crustal excision between the c. 8-10 kbar Irindina Gneiss and the overlying 6-7 kbar Brady Gneiss were used by Hand et al (1999a, b) to suggest that the peak-to post-peak metamorphic evolution of the Harts Range Metamorphic Complex occurred in an extensional setting that was terminated by the beginning of the Alice Springs Orogeny at c. 440 Ma (Mawby et al 1999;Haines et al 2001;Scrimgeour & Raith 2001).…”

Deformation in a complex crustal-scale shear zone: Errabiddy Shear Zone, Western Australia

“…The distribution of strain in shear zones may vary spatially (strain localization) and also temporally and pure and simple shear deformation may be partitioned within the shear zone (Tikoff & Teyssier 1994;Jones & Tanner 1995;Dewey et al 1998;Lin & Williams 1998;Reddy et al 1999Reddy et al , 2003. Once formed, shear zones are often zones of weakness (Holdsworth et al 2001a,b) and may further deform by reactivation leading to complex polyphase deformation histories (Scrimgeour & Raith 2001;Hand & Buick 2001).…”