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Combined in situ monazite dating, mineral equilibria modelling and zircon U–Pb detrital zircon analysis provide insight into the pressure–temperature–time (P–T–t) evolution of the western Gawler Craton. In the Nawa Domain, pelitic and quartzo-feldspathic gneisses were deposited after ca 1760 Ma and record high-grade metamorphic conditions of ∼7.5 kbar and 850 °C at ca 1730 Ma. Post-peak microstructures, including partial plagioclase coronae and late biotite around garnet, and subtle retrograde garnet compositional zoning, suggest that these rocks cooled along a shallow down-pressure trajectory across an elevated dry solidus. In the northwest Fowler Domain (Colona Block), monazite grains from pelitic gneisses record two stages of growth/recrystallisation interpreted to represent discrete parts of the P–T path: (1) ca 1710 Ma monazite growth during prograde to peak conditions, and (2) ca 1690 Ma Y-enriched monazite growth/recrystallisation during partial garnet breakdown and cooling towards the solidus. Relict prograde growth zoning in garnet suggests rocks underwent a steep up-P path to peak conditions of ∼8 kbar at 800 °C. The new P–T–t results suggest basement rocks of the southwestern Nawa and northwestern Fowler were buried to depths of 20–25 km during the Kimban Orogeny, ca 10 Myrs after the sedimentary precursors were deposited. The P–T path for the Kimban Orogeny is broadly anti-clockwise, suggesting that at least the early phase of this event was associated with extension. Exhumation of rocks from both the southwestern Nawa and northwestern Fowler domains may have occurred during the waning stages of the Kimban Orogeny (

New in situ zircon Lu–Hf isotopic data are presented from magmatic rocks distributed across the Gawler Craton, Australia. These rocks range in composition from granite to gabbro, with the majority being granite or granodiorite and moderately peraluminous in composition. The new Lu–Hf isotopic data, together with previously published data, provide insight into the magmatic evolution of the craton and crust and mantle interaction through time. Increased juvenile content of magmatic rocks correlate with periods of extensional tectonism, in particular basin formation and associated magmatism during the Neoarchean to earliest Paleoproterozoic (c. 2555–2480 Ma), Middle Paleoproterozoic (c. 2020–1710 Ma) and Late Paleoproterozoic (c. 1630–160 Ma). In contrast, magmatic rocks associated with periods of orogenic activity show greater proportions of crustal derivation, particularly the magmatic rocks generated during the c. 1730–1690 Ma Kimban Orogeny. The final two major magmatic events of the Gawler Craton at c. 1630–1604 Ma and c. 1595–1575 Ma both represent periods of juvenile input into the Gawler Craton, with ε Hf (t) values extending to as positive as + 8. However, widespread crustal melting at this time is also indicated by the presence of more evolved ε Hf (t) values to − 6.5. The mixing between crust and mantle sources during these two youngest magmatic events is also indicated by the range in two stage depleted mantle model ages (T DM c) between 1.76 Ga and 2.51 Ga. Significant mantle input into the crust, particularly during formation of the c. 1595–1575 Ma Hiltaba Suite and Gawler Range Volcanics, likely facilitated the widespread crustal magmatism of this time period. Viewed spatially, average ε Hf (t) and T DM c values highlight three of the major shear zones within the Gawler Craton as potentially being isotopic as well as structural boundaries. Differences in isotopic composition across the Coorabbie Shear Zone in the western Gawler Craton, the Middle Bore Fault in the northern Gawler Craton and, to a lesser extent, the Kalinjala Shear Zone in the southern Gawler Craton, broadly correspond to crustal and even lithospheric-scale discontinuities evident in geophysical studies. Therefore, these shear zones may approximate some of the first order crustal domains within the Gawler Craton. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Prominent Hill iron-oxide copper-gold deposit lies on the fault-bound southern edge of the Mt Woods Domain, Gawler Craton, South Australia. Chalcocite-bornite-chalcopyrite ores occur in a hematitic breccia complex that has similarities to the Olympic Dam deposit, but were emplaced in a shallow water clastic-carbonate package overlying a thick andesite-dacite pile. The sequence has been overturned against the major, steep, east-west, Hangingwall Fault, beyond which lies the clastic to potentially evaporitic Blue Duck Metasediments. Immediately north of the deposit, these metasediments have been intruded by dacite porphyry and granitoid and metasomatised to form magnetite-calc-silicate skarn ± pyrite-chalcopyrite. The hematitic breccia complex is strongly sericitised and silicified, has a large sericite ± chlorite halo, and was intruded by dykes during and after sericitisation. This paper evaluates the age of sericite formation in the mineralised breccias and provides constraints on the timing of granitoid intrusion and skarn formation in the terrain adjoining the mineralisation. The breccia complex contains fragments of granitoid and porphyry that are found here to be part of the Gawler Range Volcanics/Hiltaba Suite magmatic event at 1600-1570 Ma. This indicates that some breccia formation post-dated granitoid intrusion. Monazite and apatite in Fe-P-REE-albite metasomatised granitoid, paragenetically linked with magnetite skarn formation north of the Hangingwall Fault, grew soon after granitoid intrusion, although the apatite experienced U-Pb-LREE loss during later fluid-mineral interaction; this accounts for its calculated age of 1544 ± 39 Ma. To the south of the fault, within the breccia, Ar-Ar ages yield a minimum age of sericitisation (+Cu+Fe+REE) of dykes and volcanics of ∼1575 Ma, firmly placing Prominent Hill ore formation as part of the Gawler Range Volcanics/Hiltaba Suite magmatic event within the Olympic Cu-Au province of the Gawler Craton. [ABSTRACT FROM AUTHOR]

Abstract: Geochemical, Sm–Nd isotopic, and U–Pb–Lu–Hf zircon analyses reveal the sedimentary succession formerly recognised as the Hutchison Group consists of three temporally and isotopically distinct groups, divided by a crustal-scale shear zone (Kalinjala Mylonite Zone). The BIF endowed, newly recognised Middleback Group lies to the east of the Kalinjala Mylonite Zone and has a provenance consistent with uniquely Archean source rocks, including highly evolved ɛ Nd(1790Ma) values, positive Eu anomalies, flat REE patterns and no detrital zircon younger than 2570Ma. The depositional age of this Group is likely to be c. 2500Ma and is a possible temporal equivalent to Late Archean successions in the Gawler Craton and the BIF-endowed Hamersley Group in the Pilbara Craton, Western Australia. Two groups are recognised to the west of the Kalinjala Mylonite Zone. The older of the metasedimentary successions, here termed the Darke Peak Group, consists of felsic volcanic rocks, quartzite, pelite and carbonate rocks deposited at c. 1865Ma. The volcanic rocks have a geochemical signature of enriched, alkaline, intracontinental magmatism with A-type affinities, and mark the initiation of Paleoproterozoic rifting. Sources to the metasedimentary component of this Group were dominated by highly evolved, intra-crustally reworked, c. 2500Ma and c. 2000Ma felsic rocks, consistent with a provenance dominated by local basement complexes of the Late Archean to Early Proterozoic Gawler Craton. A succession of dominantly psammitic and pelitic units, here termed the Cleve Group, disconformably overlies the Darke Peak Group and was deposited between 1780Ma and 1730Ma. Provenance to the Cleve Group included abundant 1850Ma and 1790Ma zircons, and had a geochemical composition consistent with felsic, upper crustal sources which were significantly less evolved than the Darke Peak Group. The more radiogenic initial ɛ Nd values recorded in the Cleve Group require the input of juvenile felsic material not easily reconcilable with sources within the Southern Australian Proterozoic. Provenance data strengthen Proterozoic assembly models which suggest that the Southern Australian Proterozoic was contiguous with components of either the North Australian Craton or the southern Pilbara Craton by the time of deposition of the Cleve Succession (c. 1780Ma). The data are also internally consistent with reconstructions of Nuna which place southern Laurentia proximal to the southeast margin of Proterozoic Australia at c. 1800Ma. [Copyright &y& Elsevier]

Abstract: The Gawler Craton forms the bulk of the South Australian Craton and occupies a pivotal location that links rock systems in Antarctica to those in northern Australia. The western Gawler Craton is a virtually unexposed region where the timing of basin development and metamorphism is largely unknown, making the region ambiguous in the context of models seeking to reconstruct the Australian Proterozoic. Detrital zircon data from metasedimentary rocks in the central Fowler Domain in the western Gawler Craton provide maximum depositional ages between 1760 and 1700Ma, with rare older detrital components ranging in age up to 3130Ma. In the bulk of samples, ɛ Nd(1700Ma) values range between −4.3 and −3.8. The combination of these data suggest on average, comparatively evolved but age-restricted source regions. Lu–Hf isotopic data from the ca 1700Ma aged zircons provide a wide range of values (ɛ Hf(1700Ma) +6 to −6). Monazite U–Pb data from granulite-grade metasedimentary rocks yield metamorphic ages of 1690–1670Ma. This range overlaps with and extends the timing of the widespread Kimban Orogeny in the Gawler Craton, and provides minimum depositional age constraints, indicating that basin development immediately preceded medium to high grade metamorphism. The timing of Paleoproterozoic basin development and metamorphism in the western Gawler Craton coincides with that in the northern and eastern Gawler Craton, and also in the adjacent Curnamona Province, suggesting protoliths to the rocks within the Fowler Domain may have originally formed part of a large ca 1760–1700Ma basin system in the southern Australian Proterozoic. Provenance characteristics between these basins are remarkably similar and point to the Arunta Region in the North Australian Craton as a potential source. In this context there is little support for tectonic reconstruction models that: (1) suggest components of the Gawler Craton accreted together at different stages in the interval ca 1760–1680Ma; and (2) that the North Australian Craton and the southern Australian Proterozoic were separate continental fragments between 1760 and 1700Ma. [Copyright &y& Elsevier]

Abstract: Complexly deformed late Archean to Mesoproterozoic rocks of the western Gawler Craton are poorly exposed, thus reducing the ability to extract meaningful geological, structural and tectonic information. This study focuses on shear zone analysis via a constrained integration of qualitative aeromagnetic and Bouguer gravity data interpretation with quantitative two-dimensional forward modeling. This integration provides a means to interpret the crustal architecture as well as constrain a sequence of events, which aid the interpretation of a tectonic history for the western Gawler Craton. Results indicate a polyphase shearing history dominated by a crustal-scale array of predominantly west-dipping shear zones. The initiation of ∼east–west trending SZ1 structures was likely coincident with ca. 1750–1720Ma crustal extension, high heat flow and deposition on thinned areas of Archean crust with the development of a dense, possibly underplated lower crustal component. SZ1-R2 dextral transpressional movements reactivated SZ1 during the ca. 1720–1670Ma Kimban Orogeny, which is interpreted to record collision between the Gawler Craton and the North Australian Craton. During this event basins marginal to, and in the interior of the Archean crustal block of the western Gawler Craton were inverted and the dense lower crust was vertically offset, causing some of the long wavelength (∼30–50km) Bouguer gravity anomalies presently observed. Shear zone activity is constrained until ca. 1680Ma during which time subduction rollback established a new arc position at the southern margin of the Archean crust with magmatism persisting until ca. 1670Ma. SZ3 structures overprint and offset the interpreted axis of the Kimban Orogeny within the Archean crust. These structures record a major phase of crustal-scale sinistral strike-slip movement associated with ∼north–south shortening between ca. 1630 and 1540Ma prior to their reactivation at ca. 1450Ma. This SZ3-R4 reactivation is interpreted to cause southwest-directed crustal transport, which was focused as west-side-up movements internal to the Archean continent, whereas dextral strike-slip was focused at a major rheological boundary between thick Archean crust to the south and thick Paleoproterozoic basins to the north. [Copyright &y& Elsevier]

Abstract: The integration of structural analysis of outcrop and aeromagnetic interpretation has revealed a complex tectonic evolution for the southern Gawler Craton that reflects the regional tectonic signal during the late Paleo- to early Mesoproterozoic. Results suggest that exposures at Yarlbrinda Hill comprise the margin of a highly deformed St Peter Suite pluton emplaced within the southwestern Gawler Craton at ca. 1611 Ma. D1 at outcrop records east- to northeast-directed ductile thrusting. Regionally, this deformation overprints north–south trending dextral Yarlbrinda Shear Zone fabrics within ca. 1622 Ma St Peter Suite granite and ca. 1690–1670 Ma Tunkillia Suite granite. Progressive east to northeast directed thrust movements led to exhumation of the deformed ca. 1611 Ma granite. D2 deformation is recorded by the brittle reactivation of first generation mylonitic fabrics, accompanied by cataclasis, alteration and pseudotachylite development. D3 records a switch to ∼northwest–southeast shortening, which led to the folding and tear faulting of the D1–2 shear zone. A switch to extension and subsequent rotations of the principle stress axes led to Hiltaba Suite granite emplacement and contemporaneous faulting under ∼east–west extension during D4 and west–northwest–east–southeast extension during D5. Deformation of ca. 1622 Ma St Peter Suite granite is consistent with movement on the Yarlbrinda Shear Zone and requires the St Peter Suite to have been emplaced into or adjacent to the ca. 1690–1670 Ma Tunkillia Suite prior to shear zone activity and on the overriding plate during subduction. D1–D3 deformation is constrained by the emplacement of ca. 1580 Ma Hiltaba Suite granite and correlates with the Wartakan Orogeny in the southeastern Gawler Craton and the Olarian Orogeny in the Curnamona Province. A ∼52° disparity between the shortening directions in these respective areas suggests different degrees of Mesoproterozoic rotation, which likely aided the formation of an intervening basin province, the remnants of which are presently preserved in the Mount Painter Inlier. The record of convergent deformation is geochronologically constrained to a ∼30 Myr period and places this region of the central Gawler Craton near a late Paleoproterozoic convergent plate margin prior to a period of transient extension beginning at ca. 1580 Ma. The continental scale signal of tectonic events can be recognized at the outcrop scale highlighting the importance of detailed outcrop studies in sparsely exposed areas. [Copyright &y& Elsevier]

Abstract: Structural mapping of poorly exposed shear zone outcrops is integrated with the analysis of aeromagnetic and Bouguer gravity data to develop a multi-scale kinematic and relative overprinting chronology for the Palaeoproterozoic Tallacootra Shear Zone, Australia. D2 mylonitic fabrics at outcrop record Kimban-aged (ca. 1730–1690Ma) N–S shortening and correlate with SZ1 movements. Overprinting D3 sinistral shear zones record the partitioning of near-ideal simple shear and initiated Riedel to regional-scale SZ2 strike-slip on the Tallacootra Shear Zone (SZ2). Previously undocumented NE–SW extension led to the emplacement of aplite dykes into the shear zone and can be correlated to the (ca. 1595–1575Ma) Hiltaba magmatic event. D4 dextral transpression during the (ca. 1470–1450Ma) Coorabie Orogeny reactivated the Tallacootra Shear Zone (SZ2–R4) exhuming lower crust of the northwestern Fowler Domain within a positive flower structure. This latest shear zone movement is related to a system of west-dipping shear zones that penetrate the crust and sole into a lithospheric detachment indicating wholesale crustal shortening. These methods demonstrate the value of integrating multi-scale structural analyses for the study of shear zones with limited exposure. [Copyright &y& Elsevier]

Abstract: The bulk of sedimentary provenance studies use similarities in the detrital zircon age patterns or “barcodes” in sedimentary systems and potential source regions to make interpretations about palaeogeographic settings. While this “age-only” approach is generally considered to be effective, it is limiting because the timing of zircon growth events may not be unique to specific terrains and important rock forming events may be associated with little zircon growth. To a significant extent these limitations can be overcome by employing additional isotopic data sets such as Sm–Nd and Lu–Hf that provide information on the crustal evolution of the source region, and allow comparisons with sedimentary packages. As an example, the age spectra of detrital zircons in Palaeoproterozoic metasedimentary rocks in the eastern Gawler Craton in southern Australia are virtually identical to the dominant zircon growth timelines in adjacent older domains of the Gawler Craton, presenting a prima facie case that it was the source region. However, whole rock Nd isotopic data indicate that the pre-existing proto Gawler Craton was isotopically too crustally evolved (ε Nd (1850 Ma ) −10) to have supplied the bulk of the sediment to the relatively more juvenile metasedimentary units (ε Nd (1850 Ma) −1 to −5). In addition, zircon Hf isotopic compositions from ca 2000 Ma detrital zircons in the metasedimentary rocks (ε Hf (2000 Ma) +2 to +5) are significantly more juvenile than 2000 Ma rocks in the adjacent Gawler Craton (ε Hf (2000 Ma) −2 to −5). The combination of bulk rock Nd and Hf zircon data suggest that the Gawler Craton is not a viable source region for the metasedimentary packages, despite the striking similarity between detrital zircon ages and zircon crystallisation events within the craton. [Copyright &y& Elsevier]

Abstract: The Fowler Domain in the western Gawler Craton in southern Australia is a poorly exposed region that can only presented be explored using a combination of information from drilling and potential field geophysics. Regional maps of the Total Magnetic Intensity (TMI) field of the Fowler Domain highlight an anastomosing system of terrain-scale shear zones that bound four crustal-scale tectonic blocks: from west to east, the Colona, Barton, Central and Nundroo blocks. Integrated thermobarometry and electron microprobe chemical dating of metamorphic monazites from drillholes in the Fowler Domain suggest that the Colona Block in the west underwent two mid-crustal amphibolite grade metamorphic events at ca. 1643 and 1600Ma. The younger age corresponds to the timing of regional high-grade metamorphism in the Barton Block. Together, the age data suggest that the western Fowler Domain underwent a major tectonothermal event at ca. 1600Ma. In contrast, regional lower crustal metamorphism in the Nundroo Block, which forms the eastern Fowler Domain, occurred at ca. 1545Ma. In both the Barton and Nundroo Blocks, petrological relationships, mineral zoning, and pressure–temperature (P–T) modelling suggest the terrains cooled in the mid- to lower crust, rather than undergoing exhumation immediately following peak metamorphism. Age data from the geophysically defined shear zone systems that bound the blocks suggest that exhumation of these lower crustal domains occurred between ca. 1470 and 1450Ma and was associated with transpressional reactivation of the terrain during the Coorabie Orogeny. A key finding of this study is that the tectonic evolution of the crustal blocks in the Fowler Domain was not in concert until at least 1500Ma. Thus, the evolution of the individual blocks is unlikely to be related to the macroscopic character of the terrain defined by the regional-scale shear zone systems, which are one of the youngest tectonic imprints on the Fowler Domain. Coincident gravity and magnetic forward modelling of significant bounding faults suggests the shear zones form a steeply dipping transpressional array, consistent with the observed metamorphic field character of the different blocks. This study provides a demonstration of the integration of geophysical and petrological approaches to investigate the time-integrated tectonic evolution of poorly exposed basement terrains. [Copyright &y& Elsevier]

LA-ICPMS U-Pb data from metamorphic monazite in upper amphibolite and granulite-grade metasedimentary rocks indicate that the Nawa Domain of the northern Gawler Craton in southern Australia underwent multiple high-grade metamorphic events in the Late Paleoproterozoic and Early Mesoproterozoic. Five of the six samples investigated here record metamorphic monazite growth during the period 1730-1690 Ma, coincident with the Kimban Orogeny, which shaped the crustal architecture of the southeastern Gawler Craton. Combined with existing detrital zircon U-Pb data, the metamorphic monazite ages constrain deposition of the northern Gawler metasedimentary protoliths to the interval ca 1750-1720 Ma. The new age data highlight the craton-wide nature of the 1730-1690 Ma Kimban Orogeny in the Gawler Craton. In the Mabel Creek Ridge region of the Nawa Domain, rocks metamorphosed during the Kimban Orogeny were reworked during the Kararan Orogeny (1570-1555 Ma). The obtained Kararan Orogeny monazite ages are within uncertainty of ca 1590-1575 Ma zircon U-Pb metamorphic ages from the Mt Woods Domain in the central-eastern Gawler Craton, which indicate that high-grade metamorphism and associated deformation were coeval with the craton-scale Hiltaba magmatic event. The timing of this deformation, and the implied compressional vector, is similar to the latter stages of the Olarian Orogeny in the adjacent Curnamona Province and appears to be part of a westward migration in the timing of deformation and metamorphism in the southern Australian Proterozoic over the interval 1600-1545 Ma. This pattern of westward-shifting tectonism is defined by the Olarian Orogeny (1600-1585 Ma, Curnamona Province), Mt Woods deformation (1590-1575 Ma), Mabel Creek Ridge deformation (1570-1555 Ma, Kararan Orogeny) and Fowler Domain deformation (1555-1545 Ma, Kararan Orogeny). This westward migration of deformation suggests the existence of a large evolving tectonic system that encompassed the emplacement of the voluminous Hiltaba Suite and associated volcanic and mineral systems. [ABSTRACT FROM AUTHOR]

A three-dimensional lithospheric electrical resistivity model of the Archaean-Proterozoic Gawler Craton in southern Australia has been developed, to define the tectonic framework of the craton and identify craton margins under regolith cover. Knowledge of cratonic margins is important as upwards of 60% of known mineral wealth is located in palaeoconvergent zones between ancient cratons. The research was conducted in three phases. First, all previous magnetotelluric (MT) and geomagnetic depth sounding (GDS) data were compiled to establish a regional scale induction database. Almost 400 observation sites were found in the literature and from personal communication, collected over the last 30 years by various research groups. Of these, most measurements were GDS only, but recent 2D MT sites along major profiles provide further depth constraints. Second, eight long period MT sites were collected from central areas of the craton to provide a window into the deeper lithosphere and asthenosphere. Data were collected over a number of weeks to establish high quality MT responses in the bandwidth 10–104 s. Onedimensional modelling indicated that the lithosphere was resistive (> 100 Ω m), with a more conductive midmantle at 70 km and a decrease in resistivity at the transition zone. These MT responses agree with the long period (104-107 s) continental lithosphere induction responses of Olsen (N. Olsen: 'Long-period (30 days–1 year) electromagnetic sounding and the electrical conductivity of the lower mantle beneath Europe', Geophys. J. Int., 1999, 138, 179–187). Finally, a 3D resistivity model of the lithosphere was compiled from 2D inversions of MT profiles, with constraints from lithosphere asthenosphere soundings, and regional scale GDS data. The Gawler Craton is shown to have a resistive core of dimension 500 km, surrounded by more conductive terrains. The core is largely, but not exclusively, Archaean crust, surrounded by conductive Proterozoic crust. The edge of the core on the eastern side of the Gawler Craton correlates with the location of several iron oxide–copper–gold deposits, including the world class Olympic Dam deposit, potentially making mapping of large scale resistivity structures a useful tool for regional scale exploration. [ABSTRACT FROM AUTHOR]

Abstract: An array of northeast-trending shear zones in the north-west Gawler Craton of South Australia has been implicated in widely disparate Proterozoic continental reconstructions. These shear zones are interpreted to have formed in response to sinistral transpression, and dissect the north-west Gawler Craton into several geological domains, each with contrasting metamorphic histories. New 40Ar/39Ar data provide age constraints for movement along these shear zones, and are interpreted to indicate that the Karari, Tallacootra and Coorabie Shear Zones were last active at ∼1450Ma. Despite distinct differences in metamorphic grade, the various geological domains bounded by shear zones exhibit evidence for commonality in event histories prior to deformation at ∼1450Ma, albeit at different crustal levels. This is interpreted to indicate that deformation at ∼1450Ma was responsible for reshuffling of crustal blocks that were already adjacent, rather than amalgamation of exotic terranes. The new data also provide additional evidence for a widespread metamorphic and deformational event at ∼1530–1550Ma across the north-western Gawler Craton. The timing of deformation at ∼1450 is ∼100Ma younger than suggested in several published tectonic reconstructions and, importantly, is also significantly older than Grenvillian-age tectonism in adjacent provinces to the west and north. [Copyright &y& Elsevier]

Abstract: Large-scale Mesoproterozoic crustal shear zones are partially exposed from beneath cover sequences in the Christie Domain of the northwestern Gawler Craton, southern Australia. These structures are associated with gravity and magnetic anomalies that allow them to be mapped under cover, and their three-dimensional geometry and kinematics to be evaluated. Gravity and magnetic forward modelling indicate that these shear zones form an imbricate oblique thrust stack with combined top-to-the-southeast, left lateral transport. The longest shear zones in the stack penetrate the crust to at least 15km depth, and dip to the northwest at 70°; their inferred sense of motion are consistent with kinematic indicators from sparse outcrops. From northwest to southeast, the stack includes crustal slices bound by the Karari Fault Zone, Tallacootra and Blowout Shear Zones, Colona and Coorabie Fault Zones and the Muckanippie Shear Zone. These structures separate discrete tectonometamorphic packages within the previously undifferentiated Christie Gneiss of the Archean Mulgathing Complex, and imply several generations of transport of material from the lower and middle crust. Three-dimensional inversion of gravity data indicates that the Muckanippie Shear Zone, a shallowly rooted second-order splay of the Coorabie Fault Zone has an antithetic dip (to the southeast), and is part of a positive flower structure. Cross-cutting relationships, coupled with recent reconnaissance geochronology, suggest that the western Gawler Craton, part of the Mawson Continent, was under a long-lasting oblique slip deformational regime after ca. 1590Ma. This tectonic reworking is correlated with episodic pervasive metamorphism and deformation recorded elsewhere in the Gawler Craton between ca. 1550 and 1450 (Coorabie Orogeny), pointing to a complex history of stabilization in Proterozoic Rodinia. The Tallacootra, Colona and Coorabie structures are all cut at a high angle to their strikes by Mesozoic rift faults of the Southern Rift System, and may form piercing points in reconstructions of Gondwana, and earlier Rodinia configurations. [Copyright &y& Elsevier]

Abstract: Electron Probe Micro Analysis (EPMA) chemical dating of monazite from crustal scale shear zones in the late Archaean to Mesoproterozoic Gawler Craton, southern Australia, highlights a long history of shear zone development associated with assembly and reworking of the craton. In the southeast Gawler Craton, dextral transpression was focussed into the >250km long Kalinjala Shear Zone, which dominates the structural character of that part of the craton. Monazite in upper amphibolite facies shear fabrics within the Kalinjala Shear Zone give a mean age of 1682±10Ma. This is indistinguishable from an age of 1693±16Ma obtained from monazite inclusions within garnet porphyroclasts within the shear fabric. In the western Gawler Craton, monazite populations from two separate locations along the >400km long Tallacootra Shear Zone give ages of 1680±37 and 1679±39Ma, respectively, suggesting that both the Kalinjala and Tallacootra Shear Zone systems record regional-scale strain partitioning toward the end of the ca. 1730–1700Ma Kimban Orogeny. In the northwest Gawler Craton, the Karari Fault Zone can be traced for >700km, and separates late Archaean rocks from an assembly of tectonic terranes that comprise the northern and northwest Gawler Craton. Monazites from amphibolite-grade mylonites associated with the Karari Fault Zone have a mean age of 1631±12Ma. This age is identical to the timing of regional arc-like magmatism represented by the St. Peter Suite in the central Gawler Craton, and suggests that exhumation of the ca. 1650–1640Ma ultra high-grade granulites of the Nawa Domain in the northwest Gawler Craton was linked to the development of the St. Peter Suite magmatic margin. In the central Gawler Craton, monazite in the >200km long Yerda Shear Zone, which sheared granites belonging to the ca. 1580Ma Hiltaba Suite, have a mean age of 1503±16Ma. Similar ages of 1516±18 and 1508±14Ma are obtained from monazite inclusions in garnet porphyroclasts within mylonites along the >300km long Coorabie Fault Zone in the western Gawler Craton. Younger ages of 1468±12 and 1457±22Ma from the amphibolite-grade mylonitic fabrics in the Coorabie Fault Zone are similar to 40Ar–39Ar ages from the western Gawler Craton, and suggest that reactivation of the Coorabie Shear Zone in part was associated with regional cooling and stabilisation of the Gawler Craton at ca. 1450Ma. The history of deformation on the terrane-scale shear zones in the Gawler Craton therefore does not reflect a single period of terrane assembly or reworking, rather it points to a complex pattern of strain partitioning during tectonic events in the late Palaeoproterozoic to early Mesoproterozoic. [Copyright &y& Elsevier]

Structural mapping integrated with interpretation and forward modelling of aeromagnetic data form complimentary and powerful tools for regional structural analysis because both techniques focus on architecture and overprinting relationships. This approach is used to constrain the geometry and evolution of the sparsely exposed Mount Woods Inlier in the northern Gawler Craton. The Mount Woods Inlier records a history of poly-phase deformation, high-temperature metamorphism, and syn- and post-orogenic magmatism between ca. 1736 and 1584 Ma. The earliest deformation involved isoclinal folding, and the development of bedding parallel and axial planar gneissic foliation (S1). This was accompanied by high-temperature, upper amphibolite to granulite facies metamorphism at ca. 1736 Ma. During subsequent north–south shortening (D2), open to isoclinal south–southeast-oriented F2 folds developed as the Palaeoproterozoic successions of the inlier were thrust over the Archaean nuclei of the Gawler Craton. The syn-D2 Engenina Adamellite was emplaced at ca. 1692 Ma. The post-D2 history involved shear zone development and localised folding, exhumation of metamorphic rocks, and deposition of clastic sediments prior to the emplacement of the ca. 1584 Ma Granite Balta Suite. The Mount Woods Inlier is interpreted as the northern continuation of the Kimban Orogen. [Copyright &y& Elsevier]