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The Musgrave Province of central Australia was the focus of long-lived mantle upwelling that produced large volumes of magnesian basaltic to tholeiitic magma and their felsic derivatives. The Musgrave Province contains one of the greatest concentrations of mafic–ultramafic layered intrusions globally, grouped as the Giles intrusions. In the present paper, we study the magmatic ore potential of the Kalka, Gosse Pile and Ewarara layered intrusions located in South Australia. Ewarara and Gosse Pile appear to have relatively low potential for platnium-group element (PGE) reefs and magmatic Ni–Cu, based on lack of evident metal enrichment and the absence of a mafic–ultramafic transition zone that hosts most PGE reefs globally. However, mafic–ultramafic pipes within the intrusions that could have higher ore potential have not been studied by us. At Kalka, the mafic–ultramafic transition interval is exposed, rendering this intrusion potentially more prospective for PGE reefs. However, based on the available data, this zone appears to be barren. Instead, there are signs of PGE enrichment and metal ratio variation in the magnetite-bearing upper portion of the intrusion suggestive of undiscovered PGE reefs. This interpretation is consistent with subtle Cu–Pd enrichment of soils adjacent to the upper portion of the intrusion. First assessment of magmatic ore potential of Kalka, Ewarara and Gosse Pile layered intrusions in South Australia. Kalka shows signs of PGE enrichment in upper, magnetite-bearing portion of intrusion, suggesting enhanced potential for a PGE reef. Ewarara and Gosse Pile appear to be less prospective for PGE–Ni–Cu, but picrite pipes remain unstudied. [ABSTRACT FROM AUTHOR]

Abstract The central Australian Musgrave Province at the junction of the South, North and West Australian cratons has undergone and continues to retain evidence of significant whole-of-crust, and most likely ‘whole-of-lithosphere’ tectono-magmatic processes. The area is known for some of the largest geophysical anomalies related to significant Moho offsets of up to 15 km, which resulted from repeated intracratonic reworking since the Neoproterozoic. New magnetotelluric (MT) data have been collected across the Musgrave Province in Western Australia and South Australia as part of the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP). Station spacing was $$\sim 50\,\hbox {km}$$ ∼ 50 km between 96 sites over an area of 500 × 700 km. Long-period MT impedance and tipper data over a bandwidth of 8 s to 10,000 s period have been inverted using a smooth 3D inverse algorithm. The 3D model shows two predominant resistivity trends. There are deep ( $$>65\,\hbox {km}$$ > 65 km ) north–south mantle conductors that we infer to be related to the Palaeo- to Mesoproterozoic north-trending arc-related rocks that experienced ultra-high temperature metamorphism and widespread magmatism during the Mesoproterozoic Musgravian Orogeny. These conductors are preserved in the crust south of the Musgrave Province. The upper mantle also contains a localised resistive zone that possibly represents generation of mafic- to ultramafic magmas during the c. 1090–1040 Ma Giles Event. The crust ( $$

The central Australian Musgrave Province at the junction of the South, North and West Australian cratons has undergone and continues to retain evidence of significant whole-of-crust, and most likely 'whole-of-lithosphere' tectono-magmatic processes. The area is known for some of the largest geophysical anomalies related to significant Moho offsets of up to 15 km, which resulted from repeated intracratonic reworking since the Neoproterozoic. New magnetotelluric (MT) data have been collected across the Musgrave Province in Western Australia and South Australia as part of the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP). Station spacing was ∼ 50 km between 96 sites over an area of 500 × 700 km. Long-period MT impedance and tipper data over a bandwidth of 8 s to 10,000 s period have been inverted using a smooth 3D inverse algorithm. The 3D model shows two predominant resistivity trends. There are deep ( > 65 km ) north–south mantle conductors that we infer to be related to the Palaeo- to Mesoproterozoic north-trending arc-related rocks that experienced ultra-high temperature metamorphism and widespread magmatism during the Mesoproterozoic Musgravian Orogeny. These conductors are preserved in the crust south of the Musgrave Province. The upper mantle also contains a localised resistive zone that possibly represents generation of mafic- to ultramafic magmas during the c. 1090–1040 Ma Giles Event. The crust ( < 65 km depth) contains strong east–west crustal conductors interpreted to reflect the east–west structural grain that initiated during the c. 1090–1040 Ma Giles Event and overprinted the older N–S-oriented mantle anomalies. These E–W crustal conductors coincide with magnetic anomalies that represent crustal-scale structures, and high gravity anomalies associated with significant Moho offsets resulting from further reactivation during the c. 630–520 Ma Petermann and c. 450–300 Ma Alice Springs orogenies. [ABSTRACT FROM AUTHOR]

Abstract The approximate position of a terrane boundary between the Archean–Mesoproterozoic Gawler Craton and the Meso–Neoproterozoic Musgrave Province, central Australia, is currently inferred from magnetic and gravity anomalies. However, its precise location, structural architecture and tectonic attributes are poorly understood. Thick overlying sediments of the Neoproterozoic Officer Basin restrict outcropping basement, and the number of basement-intersecting drill holes across the proposed boundary is limited. The Gawler Craton–Musgrave Province interface is critical to interpreting the tectonic relationship between these adjacent terranes, providing insights into the mechanism of Australian Proterozoic assembly. To assist its geophysical identification, we present 14 new heat flow estimates from the Nawa and Mount Woods Domains of the Gawler Craton, along with the first heat flow value calculated from the eastern Musgrave Province. These estimates are integrated with a magnetotelluric (MT) profile that transects the study area. The new datasets show that a transition exists from heat flow values of 68–89 mW m−2 in the eastern Musgrave Province and northern Nawa Domain, through to higher heat flow values of 93–112 mW m−2 in the southern Nawa and Mount Woods Domains. This transition corresponds to a highly resistive region located between two subvertical conductive bodies observed in the MT data; seismic interpretations from the Gawler Craton–Officer Basin–Musgrave Province–Amadeus Basin (GOMA) profile indicate that it corresponds to a region located between the Sarda Bluff Fault and Karari Shear Zone within the Nawa Domain. We therefore argue that the transition from Musgrave Province to Gawler Craton lithosphere can be mapped on the basis of higher heat flow and electrical conductivity, providing sufficient contrast to constrain this interface more accurately than previous geophysical models based on magnetic and gravity data alone. Highlights • 14 heat flow estimates determined for the northern Gawler Craton. • First heat flow estimate obtained from the eastern Musgrave Province. • New heat flow data integrated with a magnetotelluric profile. • Three zones of distinctive heat flow and electrical resistivity identified. • Transition from Gawler Craton to Musgrave Province lithosphere mapped. [ABSTRACT FROM AUTHOR]

The Alcurra Dolerite in the Musgrave Province, central Australia, is part of the c. 1075 Ma Warakurna large igneous province (LIP), which is interpreted to have been emplaced contemporaneously with intracontinental rifting. The Alcurra Dolerite in the eastern Musgrave Province comprises two types of continental tholeiite. Dominant Group 1 dolerites are mainly magnesian tholeiites, whereas subordinate Group 2 dolerites are normal tholeiites. These two groups have distinct chondrite-normalized rare earth element (REE) patterns, primordial mantle-normalized trace element patterns, and incompatible element ratios (e.g. Th/Yb, Nb/Yb, La/Yb and Zr/Y). Both groups are low-Ti and low-Zr, but Group 1 dolerites have higher Ti/Zr (>60) and Ti/Y (>310) values than those of Group 2. Group 1 mainly comprises olivine-microgabbros, and is volumetrically dominant, whereas Group 2 is proportionally minor and includes noritic-microgabbros. Dolerites from both groups plot in discrete fields in 143Nd/144Nd versus 147Sm/144Nd space, along a mixing trend between chondritic or depleted mantle and the c. 1·59 Ga Musgravian basement. Group 1 dolerites have low Rb, Th and K2O contents that preclude their contamination by Musgravian continental crust. They also have incompatible element ratios that overlap with mid-ocean ridge basalt or primitive mantle. Group 2 dolerites have more negative ɛNd values and are also the more incompatible element enriched group; they may have, to some extent, been directly contaminated by Musgravian basement. Low concentrations of light REE (LREE) in Group 1 dolerites indicate a moderate to high percentage of partial melting of a relatively depleted source. Mixing this partial melt with a small proportion of melt derived by a moderate percentage of partial melting of a more incompatible element enriched mantle source could have resulted in the low (La/Sm)N ratios and low absolute La contents seen in these dolerites. Group 1 is divided into two subgroups (1A and 1B) on the basis of LREE abundances and Nb/Yb ratios. These two subgroups may reflect different percentages of partial melting of the depleted source. Petrogenetic interpretations for the Alcurra Dolerite of the eastern Musgrave Province must address published geophysical evidence for asthenospheric mantle upwelling and underplating in the Musgrave Province, and for contemporaneous low- and high-Ti Alcurra Dolerites indicative of a plume to the west where they are associated with Giles Suite layered intrusions. The large proportion of probable asthenosphere-derived melt in the petrogenesis of the Group 1 dolerites from the eastern Musgrave Province indicates either substantial heat transfer, or significant decompression in the mantle. The Warakurna LIP could result from a complex interaction between a plume and mantle upwelling. [ABSTRACT FROM AUTHOR]

Ground velocity records of the 20 May 2016 Petermann Ranges earthquake are used to calculate its centroid-moment-tensor in the 3D heterogeneous Earth model AuSREM. The global-centroidmoment-tensor reported a depth of 12 km, which is the shallowest allowed depth in the algorithm. Solutions from other global and local agencies indicate that the event occurred within the top 12km of the crust, but the locations vary laterally by up to 100 km. We perform a centroidmoment-tensor inversion through a spatiotemporal grid search in 3D allowing for time shifts around the origin time. Our 3D grid encompasses the locations of all proposed global solutions. The inversion produces an ensemble of solutions that constrain the depth, lateral location of the centroid, and strike, dip and rake of the fault. The centroid location stands out with a clear peak in the correlation between real and synthetic data for a depth of 1 km at longitude 129.8° and latitude -25.6°. A collection of acceptable solutions at this centroid location, produced by different time shifts, constrain the fault strike to be 304 ± 4° or 138 ± 1°. The two nodal planes have dip angles of 64 ± 5° and 26 ± 4° and rake angles of 96 ± 2° and 77 ± 5°, respectively. The southwestdipping nodal plane with the dip angle of 64° could be seen as part of a near vertical splay fault system at the end of the Woodroffe Thrust. The other nodal plane could be interpreted as a conjugate fault rupturing perpendicular to the splay structure. We speculate that the latter is more likely, since the hypocentres reported by several agencies, including the Geoscience Australia, as well as the majority of aftershocks are all located to the northeast of our preferred centroid location. Our best estimate for the moment magnitude of this event is 5.9. The optimum centroid is located on the 20km surface rupture caused by the earthquake. Given the estimated magnitude, the long surface rupture requires only ~4 km of rupture down dip, which is in agreement with the shallow centroid depth we obtained. [ABSTRACT FROM AUTHOR]

Abstract The post-Mesoproterozoic tectonometamorphic history of the Musgrave Province, central Australia, has previously been solely attributed to intracontinental compressional deformation during the 580–520 Ma Petermann Orogeny. However, our new structurally controlled multi-mineral geochronology results, from two north-trending transects, indicate protracted reactivation of the Australian continental interior over ca. 715 million years. The earliest events are identified in the hinterland of the orogen along the western transect. The first tectonothermal event, at ca. 715 Ma, is indicated by 40Ar/39Ar muscovite and U–Pb titanite ages. Another previously unrecognised tectonometamorphic event is dated at ca. 630 Ma by U–Pb analyses of metamorphic zircon rims. This event was followed by continuous cooling and exhumation of the hinterland and core of the orogen along numerous faults, including the Woodroffe Thrust, from ca. 625 Ma to 565 Ma as indicated by muscovite, biotite, and hornblende 40Ar/39Ar cooling ages. We therefore propose that the Petermann Orogeny commenced as early as ca. 630 Ma. Along the eastern transect, 40Ar/39Ar muscovite and zircon (U–Th)/He data indicate exhumation of the foreland fold and thrust system to shallow crustal levels between ca. 550 Ma and 520 Ma, while the core of the orogen was undergoing exhumation to mid-crustal levels and cooling below 600–660 °C. Subsequent cooling to 150–220 °C of the core of the orogen occurred between ca. 480 Ma and 400 Ma (zircon [U–Th]/He data) during reactivation of the Woodroffe Thrust, coincident with the 450–300 Ma Alice Springs Orogeny. Exhumation of the footwall of the Woodroffe Thrust to shallow depths occurred at ca. 200 Ma. More recent tectonic activity is also evident as on the 21 May, 2016 (Sydney date), a magnitude 6.1 earthquake occurred, and the resolved focal mechanism indicates that compressive stress and exhumation along the Woodroffe Thrust is continuing to the present day. Overall, these results demonstrate repeated amagmatic reactivation of the continental interior of Australia for ca. 715 million years, including at least 600 million years of reactivation along the Woodroffe Thrust alone. Estimated cooling rates agree with previously reported rates and suggest slow cooling of 0.9–7.0 °C/Ma in the core of the Petermann Orogen between ca. 570 Ma and 400 Ma. The long-lived, amagmatic, intracontinental reactivation of central Australia is a remarkable example of stress transmission, strain localization and cratonization-hindering processes that highlights the complexity of Continental Tectonics with regards to the rigid-plate paradigm of Plate Tectonics. Graphical abstract Image 1 Highlights • Two previously inferred tectonothermal events are dated at ca. 715 Ma and 630 Ma. • The age range for the Petermann Orogeny is redefined to 630–520 Ma. • The Woodroffe Thrust was reactivated at ca. 480 Ma, 400 Ma and 200 Ma and is still seismically active. [ABSTRACT FROM AUTHOR]

Three mafic-hosted, magnetite-related prospects called Jameson, Navigator and Latitude Hill occur in the most evolved, upper parts of the 1078 Ma layered intrusions belonging to the Giles Complex, Musgrave Province, Western Australia. The hosting layered intrusions are dominated by leucogabbronorite, gabbro and troctolite and each has a significant Fe-Ti oxide component comprising heavily disseminated, semi-massive and massive magnetite and ilmenite forming layers. Low grade Cu and PGE mineralization at Jameson and Navigator is strongly correlated with the presence of titaniferous magnetite. Copper, Au, Pt, Pd and S concentrations are low to very low below the first appearance of magnetite, but shift to significantly higher concentrations upon the first appearance of sulfide, which coincides with an increase in Fe 2 O 3 + TiO 2 + V 2 O 5 concentrations. Copper grades up to 0.42 wt.% and Pt + Pd + Au grades to 2 ppm are associated with S concentrations that rarely exceed 0.4 wt.%. There is a very low sulfide abundance, typically <1 modal%, dominated by Cu-rich sulfides, bornite and chalcopyrite (Cu/S ratios are typically >1). Cobalt-rich pentlandite and millerite are trace sulfides in these prospects, but pyrrhotite is rare or absent. Some of the Pt and Pd peaks are stratigraphically off-set from Cu and Au peaks. Mineralization is further characterised by high Cu/Ni ratios and low S/Se ratios indicating Ni partitioning into silicates prior to sulfide formation and very low or no crustal contamination. The Cu/Pd ratios at Jameson and Navigator show a clear shift from low Cu/Pd ratios below the sulfide-bearing magnetite zone to high Cu/Pd ratios above the base of the mineralization, highlighting that reef-type mineralization has been intersected. Mantle-normalised PGE patterns for Jameson and Navigator are PPGE > IPGE, which is typical for magnetite-related, reef-type Cu-PGE deposits. The Jameson mineralization is related to a <4 m thick magnetitite and has many characteristics that closely resemble reef-type mineralization in the Stella Intrusion, South Africa, whereas Navigator mineralization occurs in a >70 m thick, magnetite-bearing gabbronorite and websterite sequence and has more in common with reef-type mineralization at Rio Jacaré in Brazil. The Latitude Hill prospect is characterised by a >200 m thick zone of layered, semi-massive to massive magnetite, but it differs from Jameson and Navigator by having a sulfide assemblage dominated by pyrrhotite and very low whole rock Cu, Pt, Pd and Au grades. High Cu/Pd and S/Se ratios indicate that this intrusion experienced an earlier sulfide saturation event and that crustal contamination was an important factor in the formation of the sulfides at this prospect. A relatively flat mantle-normalised PGE pattern for samples from this prospect is similar to that from the Main Magnetite Layer from the Upper Zone of the Bushveld Complex. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Jameson Range intrusion forms part of the Giles Complex, Musgrave Province, Western Australia. It is predominantly mafic in composition comprising olivine-bearing gabbroic lithologies with variable amounts of magnetite and ilmenite. Lithologies containing more than 50 vol% magnetite and ilmenite are classified as magnetitites. The Jameson Range hosts several of these magnetitites forming laterally extensive layers, which can be traced for at least 19 km as continuous magnetic anomalies. Similar occurrences of magnetitites are known from the upper parts of other layered intrusions, such as the Bushveld Complex. In addition, the intrusion hosts several P-rich zones, one of which is at least 59 m in thickness containing 1.0 wt% PO. The P-rich zones are not directly associated with the magnetitites, but they mostly occur slightly above them. The mineral chemistry of the Jameson Range cumulates is relatively evolved with olivine compositions ranging from Fo to Fo and plagioclase compositions varying between An and An. The Mg# (100 × Mg / (Mg + Fe)) of ortho- and clinopyroxene ranges from 60 to 61 and from 70 to 75, respectively. Magnetite compositions are characterised by low TiO concentrations varying from 0.39 to 3.04 wt% representing near end-member magnetite with up to 1.2 wt% Cr and 1.3 wt% V, respectively. The basal magnetite layer reaches up to 68.8 wt% FeO(t) and 24.2 wt% TiO, and it is also markedly enriched in Cu (up to 0.3 wt% Cu), V (up to 1.05 wt% VO) and platinum-group elements (PGE) (up to 2 ppm Pt + Pd). Sulphide minerals comprising bornite, chalcopyrite and minor pentlandite occur finely disseminated in the magnetitite and account for the elevated base metal and PGE concentrations. Modelling indicates that the PGE mineralisation was formed at very high R factors of up to 100,000, which is typical for PGE reefs in layered intrusions. Whole rock geochemical and mineralogical data of the magnetite layers and their host rocks further allow for a refinement of current formation models of layered igneous sequences. Several lines of evidence suggest that the magnetite layers formed in response to primarily density-controlled mineral sorting within crystal slurries, although the grain size also affects the sorting process. [ABSTRACT FROM AUTHOR]

More than 20 layered intrusions were emplaced at c. 1075 Ma across > 100 000 km 2 in the Mesoproterozoic Musgrave Province of central Australia as part of the c. 1090–1040 Ma Giles Event of the Warakurna Large Igneous Province (LIP). Some of the intrusions, including Wingellina Hills, Pirntirri Mulari, The Wart, Ewarara, Kalka, Claude Hills, and Gosse Pile contain thick ultramafic segments comprising wehrlite, harzburgite, and websterite. Other intrusions, notably Hinckley Range, Michael Hills, and Murray Range, are essentially of olivine-gabbronoritic composition. Intrusions with substantial troctolitic portions comprise Morgan Range and Cavenagh Range, as well as the Bell Rock, Blackstone, and Jameson–Finlayson ranges which are tectonically dismembered blocks of an originally single intrusion, here named Mantamaru, with a strike length of > 170 km and a width of > 20 km, constituting one of the world's largest layered intrusions. Over a time span of > 200 my, the Musgrave Province was affected by near continuous high-temperature reworking under a primarily extensional regime. This began with the 1220–1150 Ma intracratonic Musgrave Orogeny, characterized by ponding of basalt at the base of the lithosphere, melting of lower crust, voluminous granite magmatism, and widespread and near-continuous, mid-crustal ultra-high-temperature (UHT) metamorphism. Direct ascent of basic magmas into the upper crust was inhibited by the ductile nature of the lower crust and the development of substantial crystal-rich magma storage chambers. In the period between c. 1150 and 1090 Ma magmatism ceased, possibly because the lower crust had become too refractory, but mid-crustal reworking was continuously recorded in the crystallization of zircon in anatectic melts. Renewed magmatism in the form of the Giles Event of the Warakurna LIP began at around 1090 Ma and was characterized by voluminous basic and felsic volcanic and intrusive rocks grouped into the Warakurna Supersuite. Of particular interest in the context of the present study are the Giles layered intrusions which were emplaced into localized extensional zones. Rifting, emplacement of the layered intrusions, and significant uplift all occurred between 1078 and 1075 Ma, but mantle-derived magmatism lasted for > 50 m.y., with no time progressive geographical trend, suggesting that magmatism was unrelated to a deep mantle plume, but instead controlled by plate architecture. The Giles layered intrusions and their immediate host rocks are considered to be prospective for (i) platinum-group element (PGE) reefs in the ultramafic–mafic transition zones of the intrusions, and in magnetite layers of their upper portions, (ii) Cu–Ni sulfide deposits hosted within magma feeder conduits of late basaltic pulses, (iii) vanadium in the lowermost magnetite layers of the most fractionated intrusions, (iv) apatite in unexposed magnetite layers towards the evolved top of some layered intrusions, (v) ilmenite as granular disseminated grains within the upper portions of the intrusions, (vi) iron in tectonically thickened magnetite layers or magnetite pipes of the upper portions of intrusions, (vii) gold and copper in the roof rocks and contact aureoles of the large intrusions, and (viii) lateritic nickel in weathered portions of olivine-rich ultramafic intrusions. [ABSTRACT FROM AUTHOR]

The ~ 120,000 km 2 Musgrave Province forms part of a continuous Musgrave–Albany–Fraser mid-late Mesoproterozoic orogenic system that transects central and southern Australia, and continues into formerly contiguous Antarctica. Voluminous felsic magmatic rocks that intruded over the interval 1330–1150 Ma, corresponding globally to the Grenvillian timeline, dominate the Musgrave Province. However, rare but widely distributed metapelitic granulites contain peak metamorphic mineral assemblages comprising garnet + sillimanite ± quartz ± spinel. These are variably overprinted by coronae and/or symplectites of cordierite-bearing assemblages such as cordierite + spinel + magnetite ± plagioclase ± garnet. Petrologic forward modelling and Zr-in-rutile thermometry indicates these peak mineral assemblages developed at thermally extreme conditions of approximately 1000 °C and ca. 7–8 kbar. These ultra-high temperature (UHT) conditions appear to have prevailed throughout the Musgrave Province, across an approximate 600 km strike distance. The retrograde P–T evolution was characterised by modest decreases in pressure during the initial high temperature segment of the cooling path, suggesting that the crust was not significantly thickened as a result of tectonism. Combined SIMS (SHRIMP) and LA–ICP–MS U–Pb geochronology constrains the total range of metamorphic monazite growth/recrystallisation ages span 1263–1111 Ma with most individual samples spanning an age range of ≥ 80 Myr. The total age span implies approximately 150 Myr of perturbed thermal conditions during the Musgrave Orogeny. Our data requires that monazite is extremely resistive to isotopic resetting, even when exposed to extreme thermal conditions for long (≥ 80 Myr) periods. The thermal conditions, large regional footprint and long timescale of metamorphism and magmatism classify the Musgrave Province as a large, hot orogen. [ABSTRACT FROM AUTHOR]

Eruptions of voluminous 18 O-depleted rhyolite provide the best evidence that the extreme conditions required to produce and accumulate huge volumes of felsic magma can occur in the upper 10 km of the crust. Mesoproterozoic bimodal volcanic sequences from the Talbot Sub-basin in central Australia contain possibly the world's most voluminous accumulation of 18 O-depleted rhyolite. This volcanic system differs from the better known, but geochemically similar, Miocene Snake River Plain – Yellowstone Plateau of North America. Both systems witnessed ‘super’ sized eruptions from shallow crustal chambers, and produced 18 O-depleted rhyolite. The Talbot system, however, accumulated over a much longer period (>30 Ma), at a single depositional centre, and from a magma with mantle-like isotopic compositions that contrast strongly with the isotopically evolved basement and country-rock compositions. Nevertheless, although the Talbot rhyolites are exclusively 18 O-depleted, the unavoidable inference of an 18 O-undepleted precursor requires high-temperature rejuvenation of crust in an upper-crustal chamber, and in this respect the evolution of the Talbot rhyolites and 18 O-depleted rhyolites of the Snake River Plain – Yellowstone Plateau is very similar. However, instead of older crustal material, the primary upper-crustal source recycled into Talbot rhyolites was comagmatic (or nearly so) felsic rock itself derived from a contemporaneous juvenile basement hot-zone. Whereas giant low δ 18 O volcanic systems show that voluminous melting of upper crust can occur, our studies indicate that felsic magmas generated at lower crustal depths can also contribute significantly to the thermal and material budget of these systems. The requirement that very high-temperatures be achieved and sustained in the upper crust means that voluminous low δ 18 O magmatism is rare, primarily restricted to bimodal tholeiitic, high-K rhyolite (A-type) magmatic associations in highly attenuated lithosphere. In the case of the Talbot system, at least, our data suggest that an unusually hot pre-history might also be required to thermally prime the crust. [ABSTRACT FROM AUTHOR]

Extensive time constrained isotopic (Sm–Nd, Lu–Hf) datasets on samples with well-studied geological context demonstrates that the Musgrave Province of central Australia and the Albany–Fraser Orogen of south Western Australia evolved through temporally similar Mesoproterozoic orogenies – at 1345–1260 and 1215–1140 Ma – but on completely different basement. The West and North Australian Cratons amalgamated before the 1345–1260 Ma event, which saw the convergence and final amalgamation of those combined cratons with the South Australian Craton. Well-defined Nd- and Hf-isotopic evolution arrays for the Musgrave Province reflect a juvenile basement with distinct 1950–1900, 1600–1550 Ma crust formation events. Rare non-radiogenic material is seen only in detritus and in magmas that assimilated this material. This evolved detritus was derived from non-Yilgarn Archean sources, and reworked Archean sources, which were added to sedimentary basins developed over the Musgrave Province basement during and after c. 1400 Ma. To the south of the Musgrave Province, the Madura Province has a similarly radiogenic signature to the Musgrave Province and is likely contiguous with it beneath younger cover sequences. It shows 2.0–1.4 Ma mantle extraction ages and is dominated by juvenile rocks reflecting oceanic crust consumed to the north of the South Australian Craton and east of the West Australian Craton. Available data support the suggestion that the Musgrave Province is simply modified Madura Province crust situated along the edge of the North Australian Craton. Together, the Musgrave Province and the Madura Province represent Proterozoic Australia's most juvenile crustal remnant. In stark contrast to this juvenile remnant, the isotopic evolution array for the Albany–Fraser Orogen reveals a much more evolved signature, charting progressive juvenile input into an Archean source with strong isotopic and age similarity to the Yilgarn Craton of the West Australian Craton. [ABSTRACT FROM AUTHOR]

The > 1090 to < 1040 Ma Giles Event added extraordinary volumes of mantle derived magma to the crust of the Musgrave region of central Australia. This included one of Earth's largest mafic intrusions – the Mantamaru intrusion – and the c. 1075 Ma formation of the Warakurna large igneous province, which spread dolerite intrusions across ~ 1.5 million km 2 of western and central Australia. It also included one of the most voluminous additions of juvenile felsic material to Earth's crust, with the development of one of the world's longest-lived rhyolitic centres, including the Talbot supervolcano. Previous suggestions that the event was the result of a deep mantle plume cannot adequately account for the > 50 m.y. duration of mantle derived magmatism or the fact that isolated localities such as the Talbot Sub-basin preserve the entire magmatic record, with no discernible regional age progressive spatial trend. For at least 100 m.y. before the Giles Event, the Musgrave region experienced high- to ultra-high crustal temperatures — possibly as an ultra-hot orogen born from a c. 1300 Ma back-arc. Granitic magmatism prior to the Giles Event also involved a significant mantle-derived component and was accompanied by mid-crustal ultra-high temperature (> 1000 °C) metamorphism reflecting a thin and weak lithosphere. This magmatism also resulted in a mid-crustal (~ 25 km deep) layer greatly enriched in radiogenic heat producing elements that strongly augmented the already extreme crustal geotherms over a prolonged period. The Giles Event may have been triggered when this regional Musgrave thermal anomaly was displaced, and again significantly destabilised, along the Mundrabilla Shear Zone — a continent-scale structure that juxtaposed the Musgrave Province against the easterly extension of the Capricorn Orogen where pre-existing orogen-scale structures were in extension. These orogen-scale structures funnelled the magmas that produced the Warakurna large igneous province and the intersection of the Musgrave thermal anomaly and the Mundrabilla Shear Zone was the site of the Talbot supervolcano. Although previously thought to be a result of a deep mantle plume, the Giles Event was more likely the product of intra-plate tectonic processes involving an anomalous and prolonged thermal pre-history, a magma-focussing lithospheric architecture and large-scale tectonic movements. [ABSTRACT FROM AUTHOR]

The Musgrave Province is one of the most geodynamically significant of Australia's Proterozoic orogenic belts, lying at the intersection of the continent's three cratonic elements — the West, North and South Australian Cratons. While remoteness and cultural sensitivity have slowed geological research into this region, recent collaborative programs in Western Australia (the west Musgrave Province) have done much to address this. This Focus Review provides a synthesis of this, and previous, work investigating the Mesoproterozoic to Neoproterozoic geological evolution of the province. The Musgrave Province is a Mesoproterozoic to Neoproterozoic belt dominated by granites formed and deformed during several major events. A cryptic juvenile basement is exposed mainly in the east Musgrave Province as c. 1600–1550 Ma orthogneiss and in the west Musgrave Province as isolated outcrops of granulite-facies metagranites of the c. 1575 Ma Warlawurru Supersuite. Zircon Hf-isotopic data suggest an earlier major juvenile crust-forming event at c. 1950–1900 Ma. There is, however, no evidence that the province evolved over Archean crust. The c. 1600–1550 Ma period probably involved evolution within a primitive arc setting, perhaps developed on c. 1950–1900 Ma oceanic or oceanic-arc crust. Voluminous calc-alkaline plutonism was accompanied by clastic and volcaniclastic basin formation during the 1345–1293 Ma Mount West Orogeny. This stage traced the evolution of a continental arc reflecting the final amalgamation of the combined North and West Australian Craton with the South Australian Craton. The intervening c. 1400 Ma primitive crust – the Madura Province – on which the proto-Musgrave Province had evolved, was consumed during amalgamation. The thickened crust resulting from this accretion was drastically thinned at the beginning of the c. 1220–1150 Ma Musgrave Orogeny as this central part of the new combined craton entered an extraordinary period of high heat flow characterised by c. 100 m.y. of ultrahigh-temperature metamorphism and high-temperature, anhydrous, alkali-calcic magmatism sourced from MASH chambers developed at the base of the thinned crust. The ridged cratonic architecture and a massive accumulation of high radiogenic heat producing granites within the mid crust perpetuated a thin crustal regime. Voluminous magmatism was again triggered during the c. 1090–1040 Ma Giles Event with the evolution of the magmatism-dominated, Ngaanyatjarra Rift. This event was likely initiated through renewed movement along translithospheric faults that intersected the thermally perturbed Musgrave Province, pinned at a cratonic junction. Mantle-derived bimodal magmatism extended more or less continuously for 50 m.y., producing one of the world's largest layered mafic intrusions and supervolcano-sized additions of juvenile felsic crust, in the form of alkali-calcic to alkali, A-type, rhyolite deposits. Together, the Albany–Fraser Orogen, which developed over the southern margin of the West Australian Craton, and the Musgrave Province mark the preserved edge of the North and West Australian Craton. These two belts show remarkable chronological links between c. 1345 and 1150 Ma but contrasting histories before and after that period. Their period of shared evolution reflects collision and accretion of the South Australian Craton, but their tectonic setting and basement geology throughout that event were very different. [ABSTRACT FROM AUTHOR]

Abstract: The Ediacaran–Cambrian Petermann Orogeny, central Australia, is an exceptional example of intraplate orogenesis. It involved sub-eclogite facies metamorphism and extreme basin inversion during the exhumation of Musgrave Province basement from beneath the formerly contiguous Centralian Superbasin. Sensitive High Resolution Ion Microprobe (SHRIMP) U–Pb geochronology of zircon, titanite and rutile, along with Ti-in-zircon thermometry from meta-igneous samples, have been used to determine the timing and duration of high-pressure metamorphism and subsequent cooling associated with this orogenic event. Peak metamorphic temperatures of 720–760°C were attained at 544±7Ma (U–Pb zircon). Subsequent cooling to 600–660°C by ~521Ma occurred at a rate of ~2.6–7.0°CMyr−1, as recorded by the closure of Pb diffusion in titanite. Further cooling to 585–560°C by 498–472Ma occurred at a rate of 0.9–4.8°CMyr−1, as recorded by Pb closure in rutile. The duration of tectonism was long-lived (>40Myr) across the central and western parts of the orogenic system, and deformation occurred in a comparatively warm and weak portion of crust, characterised by regional thermal gradients of 17–26°Ckm−1. This proposed duration of tectonism is much longer than that permitted by a shear heating mechanism, which requires an exceptionally short duration of tectonism, and additionally, an overall cold lithosphere characterised by geothermal gradients of ~9°Ckm−1. [Copyright &y& Elsevier]

Abstract: The Late Mesoproterozoic (1085–1040Ma) Ngaanyatjarra Rift, previously referred to as the Giles Event, is the dominant component of the Warakurna Large Igneous Province (LIP) that affected much of central and western Australia. This rift is well preserved and provides excellent examples of rift structure at a variety of crustal levels and times in the rift's evolution. Geological knowledge is integrated with geophysical interpretations and models to understand the crustal structure and evolution of this rift. Two phases are identified: an early rift stage (1085–1074Ma) that is characterised by voluminous magmatism within the upper crust and relatively little tectonic deformation; and a late rift stage that is characterised by tectonic deformation, synchronous with the deposition of a thick pile of volcanic and sedimentary rocks (1074–1040Ma). Compared to modern rift examples, this rift is unusual in that the crust was thickened by ~15km and overall extension was very limited. However, its structure and evolution are very similar to the near-contemporaneous Midcontinent Rift, which shows the addition of a similar quantity of magmatic material as well as crustal thickening and limited extension. For these Mesoproterozoic rifts, we suggest that magmatism was the dominant process, and that the extension observed was a response to magmatism-induced crustal thickening and the gravitational collapse of the crustal column. Other Proterozoic rifts show similar characteristics (e.g. Transvaal Rift), whereas most Phanerozoic rifts are dissimilar, showing instead a dominance of extension, with magmatism largely a result of this extension. This change in the style of rifting from the Precambrian to the Phanerozoic may relate to the influence of a typically cooler and stronger lithosphere, which has caused stronger strain localisation and a greater role for extension as the controlling factor in rift evolution. [Copyright &y& Elsevier]

Abstract: The Hf and Nd isotopic evolution of the Musgrave Province, central Australia, is used to constrain the timing of crust formation and lithospheric organisation of Proterozoic Australia. The dataset from this region challenges two widely held tenets of Hf and Nd isotope systematics, namely; that crust formation events can only be identified as periods when crystallisation ages correspond to model ages, and that linear Hf evolution arrays away from depleted mantle (along crustal Lu/Hf or Sm/Nd slopes) reflect reworking of the same source. Hf isotopes in Musgrave Province zircon crystals indicate two major crust formation events at c. 1900Ma and at 1600–1550Ma. Although no juvenile rocks or crystals are known from c. 1900Ma, radiogenic addition into the crust at this time is required to account for consistent Nd and Hf evolution patterns, which show no indication of an initially heterogeneous source. Oxygen isotopes in zircon grains confirm that much of the c. 1900Ma Hf isotopic signal is not compromised by mixtures. Furthermore, the correspondence between mantle extraction and the commencement of reworking of Archean material supports new crust generation at c. 1900Ma and a coupling between lower and upper crustal processes. The c. 1900Ma timing of juvenile addition is dissimilar to that in the Albany–Fraser and Arunta Orogens and may reflect continental arc development on the margin of a southern continent. The general Hf isotopic evolution trend of the Musgrave Province apparently reflects reworking from a dominant c. 1900Ma source with some additional unradiogenic and radiogenic input through time. However, in the 1220–1050Ma interval this apparent isotopic evolution contrasts with geological observations that indicate input of voluminous mantle-derived material. Intracontinental rifts and other regions with sustained very-high temperature crustal recycling processes generate magmatic provinces with extreme HFSE-enrichment. This can have a profound influence on isotopic evolution trends, suppressing typical juvenile addition patterns. Isotopic mixture modelling indicates that a significant volume of mantle derived material can be accommodated within HFSE enriched magmas without diverging isotopic signatures from apparent reworking trends. In the Musgrave Province, the crust had become so HFSE enriched during the prolonged Musgrave Orogeny (1220–1150Ma) that it was insensitive to mantle input, which is estimated to have been as much as 85% during this event. [Copyright &y& Elsevier]

Abstract: The Archaean to Mesoproterozoic basement of northern South Australia is almost completely overlain by thick Neoproterozoic and younger basins (≪1% outcrop), yet is likely to preserve an important record of the interactions between the Archean-Proterozoic Gawler Craton and the Proterozoic Musgrave Province during the amalgamation of Australia in the Proterozoic. However, constraints on the location and geometry of the boundary between these provinces are poor. We use potential field data to determine the 3D basement architecture and so constrain where this Palaeo-Mesoproterozoic boundary may be located beneath the Eastern Officer Basin. We establish the geometry and properties of the overlying basins and explicitly include them during forward and inverse modelling of potential field data to highlight the structure of the underlying basement. Our analysis identifies three crustal domains. (1) Southeast of the steep northeast–southwest Middle Bore Fault, positive gravity and magnetic anomalies are co-located and sourced from bodies in the upper crust, these bodies overlie middle to lower crust that is apparently uniform. (2) Between the Middle Bore Fault and the southern edge of the Munyarai Trough, the highest amplitude gravity and magnetic anomalies are not co-located and are sourced from large northwest dipping bodies. (3) To the northwest, the crust underlying the Munyarai Trough has similar properties to the Musgrave Province, suggesting that the Musgrave Province extends at least 50km beneath the Eastern Officer Basin. Although details of the geology in the second (central) domain are poorly constrained, the domain preserves large crustal-scale Precambrian structures and is interpreted to mark the boundary between the Gawler Craton and the Musgrave Province. In particular, the multiply reactivated Middle Bore Fault forms a major crustal boundary and is interpreted to mark the northern limit of the Gawler Craton. The Middle Bore Fault may have formed as early as the Kimban Orogeny (∼1.7Ga), although substantial reactivation and modification of the crustal architecture could have occurred between the Kimban Orogeny and intrusion of the cross-cutting Gairdner Dolerite Dykes (827Ma). [Copyright &y& Elsevier]

Abstract: Mafic and felsic rocks units of the Musgrave Province originally attributed to the c. 1075Ma Giles Event of the greater Warakurna Large Igneous Province (LIP) are shown to be part of a complex sequence of magmatic and tectonic events punctuated over a span of at least 50m.y. New geochronology and mapping resolve a sequence of at least 10 magmatic pulses with hiati of up to 10m.y. consistent with a long-lived intracontinental rift setting. This rift, here named the Ngaanyatjarra Rift, features giant layered mafic-ultramafic Giles intrusions cut by a 10km wide mafic-felsic magmatic shear zone. The latter is temporally related to the Warakurna LIP, however it is not clear that the Giles intrusions actually form part of the Warakurna LIP. Macroscopic folding and the formation of the large synmagmatic transpressional shear zone attest to synmagmatic basin inversion in the early stages of the rift. The extensive mafic to felsic volcanic rocks of the Tollu Group (traditionally grouped with the Giles Event) were emplaced 25–50m.y. later than the c. 1075Ma Warakurna LIP. [ABSTRACT FROM AUTHOR]

Abstract: Constrained aeromagnetic interpretation and modelling in the south-central Musgrave Province has produced a model of the regional structural evolution that permits links to be made between localised structural studies and continent-scale tectonic models. Eight deformation events were defined in this region, several of which can be interpreted in the context of tectonic events related to the formation and break-up of Proterozoic supercontinents. D1 reflects northwest-southeast shortening during the ca. 1200Ma Musgravian Orogeny, and its structure suggests that the Musgravian Orogeny occurred due to re-organisation of the Australian and Mawson continents during Rodinia assembly, rather than as part of a supercontinent-scale orogenic belt. D3 is interpreted to represent north-south shortening ca. 1060Ma, characterised by inversion of extensional architecture developed during the ca. 1080Ma Giles Event. D3 occurred in an intraplate environment, probably as a result of continued Rodinia assembly. D4 is characterised by northeast-southwest extension and dyke emplacement, probably ca. 800Ma, which is consistent with a northwest-trending aulacogen extending across South Australia during Rodinia break-up. The ca. 550Ma Petermann Orogeny is characterised by pervasive reactivation of pre-existing architecture under north-south shortening (D5 and D6) followed by dextral transpression on east and southeast-trending crustal-scale shear zones (D7). This intraplate deformation resulted from a compressive stress field during the assembly of Gondwana, probably due to the collision of India with Australia''s western margin, and the initiation of subduction at the eastern margin of the Australian continent. The structural evolution of the Musgrave Province is therefore intimately linked with the supercontinent cycle, and provides a model of the architecture, deformation pattern and stress field of central Australia throughout the Proterozoic, which is an important constraint on the possible configurations of Rodinia and Gondwana. [Copyright &y& Elsevier]

Integrated aeromagnetic and field-based structural analysis provides a method for establishing a constrained regional-scale tectonic model where insufficient outcrop, remoteness or restricted access precludes widespread structural mapping. In this method the different scales of observation lead to uncertainty in integrating the observations. An integrated analysis of the Deering Hills region of the Musgrave Province shows that this uncertainty is largely dependent on the magnetic data resolution, the scale of deformation, and mineralogy. In the Deering Hills, four deformation events are defined, each with different structural character. These differences in character result in different levels of uncertainty in integrating these observations with aeromagnetic data. D1 was only evident at small scales in outcrop, and therefore any correlation with aeromagnetic data is inherently uncertain. However, well-defined relative timing to D2, and the parallel nature of an S1 foliation and regional D1 structures identified in the aeromagnetic data permitted the derivation of a moderately reliable regional model indicating northwest to southeast directed shortening at a deep crustal level during the Musgravian Orogeny. This resulted in a pervasive gneissic foliation, and a regional array of northeast-trending reverse-shear zones and tight to isoclinal upright folds. A higher confidence regional model was derived for the second deformation event (D2), which was identified at the regional scale in outcrop and could be directly correlated with features in the aeromagnetic data. North-south-directed crustal shortening, either in the late Musgravian Orogeny or during deformation ca 1060 Ma resulting in east-southeast- and southeast-trending reverse- and dextral-reverse shear zones and southeast-trending recumbent isoclinal nappes. For the third and fourth deformation events, links could not be made between field observations and aeromagnetic data, and the regional models for these events are low in confidence. The regional setting of D3 is not defined, and D4 is interpreted to represent the development of shear zones during north-south compression in the Petermann Orogeny. [ABSTRACT FROM AUTHOR]

Abstract: The Musgrave Province in central Australia is an east-west trending ∼120,000km2 region composed of lithologic units that range in age from earliest Mesoproterozoic to Neoproterozoic. It is one of the few terrains in Australia that records significant Grenvillian-aged tectonism, and has a distinctly younger geological history than the surrounding fragments of Proterozoic Australia. Compared to other Proterozoic terranes of Australia the evolution of the Musgrave Province is poorly understood. The region contains evidence for the development of earliest Mesoproterozoic arc-related magmatism, with major juvenile crustal additions comprising intercalated felsic and mafic gneisses with protolith ages ranging from ca. 1.60 to 1.54Ga. This period of arc magmatism was followed by closure of the ocean separating the North Australian Craton (NAC) from the South Australian Craton (SAC) at ca. 1.54Ga. Arc magmatism and collision was followed by a period of extension during which protoliths to the metasedimentary rocks of the eastern Musgrave Province were deposited at ca. 1.4Ga. The combined juvenile Nd isotopic signature and detrital zircon ages from these metasediments suggests provenance from non-Australian sources, with possible sources originating from Laurentia. Granitic magmatic events occurred at ca. 1.3 and 1.20–1.14Ga, the latter comprising the voluminous A-type granites of the Pitjantjatjara Supersuite. The intrusion of these magmatic units provide key temporal constraints on deformational events, and are coeval with the voluminous A-type suites of Laurentia which would invite correlation of Australia with Laurentia at ca. 1.30–1.14Ga. These magmatic episodes are accompanied by deformation at granulite facies at ca. 1.30Ga (unnamed event), and 1.23–1.15Ga (Musgrave Orogeny). These deformation/metamorphic events have completely recrystallised any primary layering within the pre 1.30Ga rocks, forcing interpretations on their genesis to be inferred from geochemical and isotopic data. The tectonic significance of these events is not clear, however they may form part of a larger Grenville-aged deformational belt extending into the western Australian Albany-Fraser Province and Antarctica. Emplacement of the voluminous mafic–ultramafic Giles Complex and associated granulite facies metamorphism of the Giles Event occurred at ca. 1.078Ga. The layered intrusions of the Giles Complex are generally fault bound, and are considered to represent discrete bodies emplaced in an extensional regime associated with generation of the Warakurna Large Igneous Province. The ca. 1.08Ga Alcurra Dolerite, unnamed ca. 1.0Ga olivine dolerites, and ca. 0.8Ga Amata Dolerite dissect much of the Musgrave Province. The Alcurra Dolerite and unnamed olivine dolerite dykes have been proposed as originating from a modified sub-continental lithospheric mantle, whereas the Amata Dolerite is proposed to be plume related, coinciding with the initiation of rifting creating the Centralian Superbasin. An earliest Cambrian intraplate transpressional event is recorded in the ca. 550Ma Petermann Orogeny. This resulted in deep crustal exhumation of much of the northern Musgrave Province from beneath the Centralian Superbasin, with mylonitic deformation recorded at pressures of ∼12kbar and temperatures of 700–750°C. [Copyright &y& Elsevier]

The Ngunala Intrusion is a poorly understood layered mafic-ultramafic intrusion that forms part of the voluminous Giles Complex intrusions (∼1080 Ma) of the Musgrave Province. Preliminary geochemistry, petrology and field observations indicate that the Ngunala Intrusion is composed of a series of discrete magmatic pulses. The identification of rare fragments of pentlandite and chalcopyrite in the southern outcrop of the Ngunala Intrusion indicates that the host magmas reached sulphur saturation and highlights its potential to host magmatic sulphide mineralisation. The Ngunala Intrusion is located in close proximity to a major crustal scale structure proposed to have acted as a major magma conduit. The series of discrete magmatic pulses identified in outcrop and interpreted at depth, describes an active, dynamic magmatic environment to allow for magma mixing. The Ngunala Intrusion is host to several characteristics that describe the appropriate physical environment required to concentrate the sulphides into a deposit. [ABSTRACT FROM AUTHOR]