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

Abstract

Detailed mapping of four areas representing different geological units with varying formation histories within the crustal-scale Errabiddy Shear Zone shows an apparently simple temporal progression from foliation and mineral lineation development to folding and then to brittle deformation across the shear zone. However, in detail the structural evolution of the shear zone shows considerable complexity. The dominant foliation throughout the shear zone was formed in the upper greenschist to amphibolite facies during the 2000-1960 Ma Glenburgh Orogeny, which involved the accretion of the Archaean to Palaeoproterozoic Glenburgh Terrane onto the Archaean Yilgarn Craton and the subsequent formation of the Errabiddy Shear Zone. Orthorhombic kinematic indicators formed during the Glenburgh Orogeny as did the widespread mineral lineation. These fabrics were overprinted by a greenschist facies deformation and metamorphic event during the 1830-1780 Ma Capricorn Orogeny. During the Capricorn Orogeny mineral lineation development was rare, and mostly took place in high-Capricorn strain zones in areas where a pre-existing Glenburgh-aged mineral lineation was present. Such mineral lineations trend parallel to Capricorn-aged fold hinges. Regardless of the presence or absence of Capricornaged mineral lineations, dextral strike-slip kinematics and simple shear indicated by delta and sigma porphyroclasts, and displacement along detachment faults, are prevalent close to discrete shear zone boundaries, within the Errabiddy Shear Zone. However, between shear zone boundaries flattening and coaxial strain dominated during the Capricorn Orogeny. This difference in Capricorn Orogeny kinematics throughout the shear zone is caused by strain partitioning -although progressive deformation throughout the shear zone with dextral strike-slip faults overprinting older structures formed by pure shear also took place. These results suggest that analyses of small parts of shear zones may not give the complete history of an evolving transpressional shear zone because of the presence of strain partitioning and strain localization over time.Crustal-scale shear zones are fundamental discontinuities that often are the sites of continental accretion, collision, extension and intraplate deformation. Such zones may accommodate deformation via simultaneous components of pure and simple shear (i.e. general shear). 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

Spatio-temporal evolution of the Satpura Mountain Belt of India: A comparison with the Capricorn Orogen of Western Australia and implication for evolution of the supercontinent Columbia

“…The Capricorn Orogeny (1830e1780 Ma) produced dextral transpressional structures at greenschist facies conditions (Occhipinti and Reddy, 2004) in the Glenburgh Terrane and the Narryer Terrane. The Dalgaringa Supersuite, a dominant component of the Glenburgh Terrane in the Southern Capricorn Orogen, has abundance of medium-K I-type tonalite and granodiorite similar to Phanerozoic Andean-type batholiths .…”

“…On the basis of these observations Sharma (2007) has questioned the proposition of Bhowmik et al (1999Bhowmik et al ( , 2000 and Acharyya (2001Acharyya ( , 2003 that the Satpura orogenic event I at 1500e1600 Ma is pre-Sausar in age. Tyler and Thorne, 1990;Evans et al, 2003;Occhipinti and Reddy, 2004;W-12: 3.2. The eastern continuation of the Satpura Orogen…”

Seismic Reflection and Potential Field Constraints on Imbrication and Exhumation of the Paleoarchean Narryer Terrane, Yilgarn Craton

“…We favor possible late (?) Capricorn movement, because the evidence for dextral transpression along N2 resembles the kinematics of the Cargarah Shear Zone (Spaggiari, 2007) and also the Errabiddy Shear Zone during the Capricorn Orogeny (Occhipinti & Reddy, 2004). Furthermore, there is -so far-no evidence for post-Capricorn ductile deformation within the Narryer Terrane (Spaggiari, 2007;Spaggiari et al, 2008).…”

“…The northern margin of the Narryer Terrane was deformed during this collision, reworked in the subsequent 1.82–1.77 Ga intraplate Capricorn Orogeny, and is now represented by the Yarlarweelor Gneiss Complex (Sheppard et al., 2003). The Errabiddy Shear Zone, which marks the present day boundary between the Glenburgh Terrane and the Yilgarn Craton, formed during the Glenburgh Orogeny and was affected by dextral transpression during the Capricorn Orogeny, which also resulted in the intrusion of large plutons into, and north of, the Glenburgh Terrane (Occhipinti & Reddy, 2004; Sheppard et al., 2004).…”

SHRIMP U–Pb phosphate dating shows metamorphism was synchronous with magmatism during the Paleoproterozoic Capricorn Orogeny

“…Although the direct P-T conditions remain elusive, this study combined with previous work, has established the following framework that must be explained by any tectonic model: regional low-to mediumgrade metamorphic assemblages (except for the Yarlarweelor Gneiss Complex, which shows a higher grade of metamorphism); direct ages for metamorphism at 1805-1772 Ma; geochronological constraints on deformation at 1813-1772 Ma; and regional magmatism at 1820-1775 Ma. The higher-grade rocks exposed in the Yarlarweelor Gneiss Complex could be a result of dextral transpression affecting the Errabiddy Shear Zone during the Capricorn Orogeny, resulting in uplift of deeper crustal rocks (Occhipinti & Reddy, 2004). Any proposed model must be able to explain the synchronicity of magmatism, active deformation and metamorphism during compression.…”