Intracontinental Orogeny Enhanced by Far‐Field Extension and Local Weak Crust

Abstract

The accommodation of intraplate stresses in preexisting weak regions of plate interiors is here investigated using thin viscous sheet numerical models. The intraplate stresses are governed by multicomponent and multidirectional stresses originating at plate boundaries. The modeled scenarios mimic plate boundary conditions during the intraplate Alice Springs Orogeny (ASO), central Australia, and include (1) a northwest‐southeast zone of weak lithosphere within strong continental blocks to the north and southand (2) a principal south directed stress condition at the northern boundary that causes minor clockwise rotation of the northern block. Alternative tectonic environments are investigated in additional models that include (1) secondary compressional or extensional stresses acting at the eastern boundary, representing the temporally variable stress conditions during the Tasmanides Orogeny, and (2) an eastern wedge‐shaped zone of rheologically weak lithosphere, mirroring rift fill of the Irindina subbasin. Our results highlight that a low angle between major crustal features (e.g., orogenic elongation and preexisting regional structures) and the principal transmitted stresses is highly relevant in the concentration of elevated levels of differential stress and subsequent localization of deformation in plate interiors. Secondary stresses orthogonal to the principal acting stresses may introduce effects that explain the episodic orogenic activity in the case of the ASO. The combination of secondary extensional stresses at the eastern boundary of Australia and weak lithosphere of the preexisting Irindina subbasin strongly influences the observed spatial strain intensity, localization, and kinematics of deformation during the ASO.

Melt-present shear zones enable intracontinental orogenesis

“…Recent work shows that the failed Larapinta Rift (LR; Fig. 3), together with its thick sedimentary fill, represents the required weak zone and, additionally, global-scale plate reorganization drove riftinversion and strain localization (Silva et al, 2018). Whereas the importance of fault reactivation in controlling deformation patterns during orogenesis has been recognized (e.g.…”

“…The timing of orogenic activity along the eastern margin of Australia in the Tasmanides (Tasman.) is dominantly extensional, with periods of compression (marked as "x") or significant strike slip movement (double arrows) shown (Raimondo et al, 2014;Silva et al, 2018).…”

Pressure–temperature–time constraints on gneiss dome formation in an intracontinental orogen

“…The Amadeus and Georgina Basins represent fragments of the formerly continental-scale Centralian Superbasin (Figure 1a) that was separated into structural remnants as a consequence of Palaeozoic basement exhumation associated with the c. 450-300 Ma intraplate Alice Springs Orogeny (Buick et al, 2005;Haines et al, 2001;Maidment et al, 2013;Shaw et al, 1991). Similarly, the present arrangement of the HRG is ascribed to the ASO (Haines et al, 2001;Maidment et al, 2013;Piazolo et al, 2020;Raimondo et al, 2011;Silva et al, 2018). This event exhumed the HRG rift complex and underlying Paleoproterozoic Arunta basement, including the EGC, from deep crustal levels (≥20 km), and inverted the north-eastern section of the overlying Centralian Superbasin (Sandiford & Hand, 1998).…”

“…The Entia Gneiss Complex (EGC) is located in the Harts Range, central Australia (Figure 1a,b) and represents the exhumation of Paleoproterozoic granulite facies basement that underwent hydration and recrystallization at amphibolite facies conditions during the Palaeozoic intracontinental Alice Springs Orogeny (ASO; 450-300 Ma) (Buick et al, 2008;Fournier et al, 2016;Hand, Mawby, Kinny, & Foden, 1999;Piazolo et al, 2020;Prent et al, 2020;Silva et al, 2018). The EGC crops out in an approximately elliptical domal structure that is 25 Â 15 km in diameter along its major and minor axes, respectively, and contains two antiformal culminations referred to as the Inkamulla and Huckitta sub-domes (Figure 2).…”

Th–U powered metamorphism: Thermal consequences of a chemical hotspot

“…Cycles of increased hydrothermal-magmatic activity are linked to periods of cooling recorded by K-Ar thermochronology, considered to be caused by exhumation during denudation or from far-field effects of the Alice Springs Orogeny (e.g. McLaren et al, 2002;Raimondo et al, 2014;Silva et al, 2018). Initial magmatic activity spanned 460-430 Ma with the emplacement of the British Empire Granite, Mudnawatana Tonalite and various associated pegmatitic bodies (e.g.…”