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The ca 1600–1580 Ma time interval is recognised as a significant period of magmatism, deformation and mineralisation throughout eastern Proterozoic Australia. Within the northern Yorke Peninsula in South Australia, this period was associated with the emplacement of multiple phases of the Tickera Granite, an intensely foliated quartz alkali-feldspar syenite, a leucotonalite and an alkali-feldspar granite. These granites belong to the broader Hiltaba Suite that was emplaced at shallow crustal levels throughout the Gawler Craton. Geochemical and isotopic analysis suggests these granite phases were derived from a heterogeneous source region. The syenite and alkali-feldspar granite were derived from similar source regions, likely the underlying ca 1850 Ma Donington Suite and/or the ca 1750 Ma Wallaroo Group metasediments with some contamination from an Archean basement. The leucotonalite is sourced from a similar but more mafic/lower crustal source. Phases of the Tickera Granite were emplaced synchronously with deformation that resulted in development of a prominent northeast-trending structural grain throughout the Yorke Peninsula region. This fabric is associated with composite events resulting from folding, shearing and faulting within the region. The intense deformation and intrusion of granites within this period resulted in mineralisation throughout the region, as seen in Wheal Hughes and Poona mines. The Yorke Peninsula shares a common geological history with the Curnamona Province, which was deformed during the ca 1600–1585 Ma Olarian Orogeny, and resulted in development of early isoclinal and recumbent folds overprinted by an upright fold generation, a dominant northeast-trending structural grain, mineralisation, and spatially and temporally related intrusions. This suggests correlation of parts of the Gawler Craton with the Curnamona Province, and that the Olarian Orogeny also affected the southeastern Gawler Craton. Refereed/Peer-reviewed

Light rare earth elements (LREEs) are commonly enriched within iron oxide-copper-gold (IOCG) deposits within the Gawler Craton, South Australia. The LREEs are host within a number of phases including monazite, which is a resistate phase that can withstand processes of physical transport and weathering without significant chemical alteration. Recognition of this elevated LREE signature within rocks that have been transported away from mineralised zones can therefore be used as a geochemical vector towards potential IOCG mineralisation.In the northern Gawler Craton, South Australia, monazite occurs within basement rocks within and proximal to the Prominent Hill IOCG deposit. These basement rocks have been physically transported and dispersed during glacial activity subsequent to the mineralisation event, and redeposited in the cover sequence as a glacial diamictite. Here we show that the hydrothermal monazite within the mineralised zone has a characteristic geochemical signature, and that this signature has been preserved within monazite grains within the overlying glacial diamictite. The hydrothermal monazite is characteristically enriched in La and Ce, and depleted in Y and Th. A chemical criterion for exploration is derived. Monazite chemistry showing concentrations of La. +. Ce >. 63. wt.% and Y and Th . 75. ppm and Ce >. 155. ppm is considered anomalous. Data that also shows (La. +. Ce):Y ratios between 10:1 and 30:1 and (La. +. Ce):Th ratios between 16:1 and 32:1 is considered interesting. Ratios of (La. +. Ce):Y and (La. +. Ce):Th greater than 30:1 and 32:1 respectively are considered compelling. In the northern Gawler Craton, the scale of the footprint associated with the anomalous whole rock geochemical signature characteristic of Prominent Hill-style IOCG mineralisation is 2-3 times larger than the orebody itself. Dispersion of this signature is related to glacial processes and palaeotopography. This chemical criteria may potentially be used as a geochemical vectoring method towards Prominent Hill-style IOCG mineralisation, and may be applicable to exploration for other IOCG deposits within the Gawler Craton and further afield. Refereed/Peer-reviewed

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 epsilon(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 epsilon(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(PM)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 epsilon(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. Refereed/Peer-reviewed

The far northeastern Gawler Craton, South Australia, lies at the northern margin of one of the major building blocks of the Australian continent and is a region that is important in models for the Proterozoic tectonic evolution of Australia. However, this region is overlain by Phanerozoic sedimentary cover and consequently has had no previous geological study. We report the lithotypes, geochronology, geochemistry and isotopic composition of rocks recovered in a mineral exploration drill hole in the far northeastern Gawler Craton, the sole drill hole to sample crystalline basement in this region. Lithologies within the drill hole are garnet- and pyrite-bearing metasedimentary gneiss, pyroxenite and gabbroic intrusions, along with granitic bodies. Metasedimentary gneiss has a maximum depositional age of 1841 +/- 4 Ma and a provenance pattern more similar to rocks of the Aileron Province of the Arunta Region, central Australia, in particular the Lander Rock Formation, than to other metasedimentary rocks of the Gawler Craton. Amphibolite fades metamorphism occurred at c. 1780 Ma and was synchronous with emplacement of high Mg, crustally contaminated mafic rocks, along with several types of felsic intrusion. This metamorphic event is very similar in age and style to the Yambah Event of the Aileron Province, and has not been documented previously in the Gawler Craton. The overall geological features of this portion of the northern Gawler Craton support models that link it with the Aileron Province of the Arunta Region. The rocks of drill hole TB02 underwent thermal resetting recorded by a biotite Ar-40/Ar-39 age of c. 480 Ma, likely as a result of the Cambro-Ordovician Delamerian Orogeny along the eastern margin of Gondwana. Refereed/Peer-reviewed

This study utilises U-Pb geochronology, Lu-Hf, Sm-Nd isotopes and geochemistry to constrain the timing of deposition, metamorphism and provenance characteristics of buried Palaeoproterozoic meta-sedimentary and meta-igneous rocks in the northern Gawler Craton, Australia. The data suggest that sedimentary sequences were deposited between ca. 1780 and 1740 Ma across a wide region accompanied by syn-depositional magmatism. Restricted zircon age spectra, relatively radiogenic whole-rock Hf-Nd and in-situ zircon Hf isotopic compositions and enriched REE signatures support the notion of a connected series of basins or a single large basin, which developed on a common Neoarchaean substrate across the northern Gawler Craton during the Late Palaeoproterozoic. Temporal and isotopic correlation of these indurated rocks with Palaeoproterozoic basins throughout the North Australian Craton suggests they may form part of an extensive basin system that developed across the Australian continent during the Late Palaeoproterozoic. The meta-sedimentary and meta-igneous rocks of the northern Gawler Craton record high-grade crustal anatexis during the ca. 1730–1690 Ma Kimban Orogeny and subsequent Early Mesoproterozoic re-working. Refereed/Peer-reviewed

Refereed/Peer-reviewed

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 50 km 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 (similar to 1.7 Ga), 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 (827 Ma). Refereed/Peer-reviewed

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 1700 Ma, with rare older detrital components ranging in age up to 3130 Ma. In the bulk of samples, εNd(1700 Ma) 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 1700 Ma aged zircons provide a wide range of values (εHf(1700 Ma) +6 to −6). Monazite U–Pb data from granulite-grade metasedimentary rocks yield metamorphic ages of 1690–1670 Ma. 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 1760–1700 Ma 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 1760–1680 Ma; and (2) that the North Australian Craton and the southern Australian Proterozoic were separate continental fragments between 1760 and 1700 Ma. Refereed/Peer-reviewed

The 1690–1670 Ma felsic Tunkillia Suite was generated through the central Gawler Craton, southern Australia, during or after the waning stages of the 1730–1690 Ma Kimban Orogeny. Previous models for the generation of the Tunkillia Suite used trace element tectonic discrimination diagrams to suggest a subduction-related petrogenesis. Subsequently, Tunkillia Suite magmatism was used to infer an active plate margin in paleotectonic reconstruction models. In part, this led to the suggestion of a long-lived active margin on the southern edge of paleo-Australia that was correlated with the long-lived active margin of south-western Laurentia. The more detailed geochemical and isotopic analyses used in this study highlight the shortcomings of analysis based upon simple application of trace-element tectonic discrimination diagrams. The combination of detailed geochemical assessment and new geochronology demonstrates that some intrusions previously used to characterise the tectonic setting of the Tunkillia Suite are in fact unrelated. Tunkillia Suite intrusions are typically high-K, alkali-calcic and magnesian and are dominantly felsic (>70 wt% SiO2), moderately peraluminous granitoids. Trace and rare earth element abundances display large variations. Sr and Y concentrations range from 40 to 550 ppm and from 4.7 to 41 ppm, respectively. Eu/Eu* values range from 0.2 to 1.6 and combined with REE patterns demonstrate the varying composition of restite associated with melt generation of the Tunkillia Suite. The majority of the Tunkillia Suite display chemical characteristics typical of a plagioclase- or hornblende-dominated restite with only three samples demonstrating garnet-rich restite composition. Nd-isotope characteristics of Tunkillia Suite intrusions suggest a crustal column of variable age exists in the Gawler Craton, as variation in ɛNd(T) values (−6.3 to +2.6) cannot be accounted for simply through assimilation and fractional crystallisation processes. The limited SiO2 compositional range of the Tunkillia Suite inhibits unequivocal tectonic classification due to the inability to determine mantle melt composition and infer mantle melting conditions leading to the generation of the Tunkillia Suite. Geochemical, isotopic and mineralogical characteristics of the Tunkillia Suite are most consistent with a ‘late- to post-tectonic’ setting for petrogenesis. The term ‘late- to post-tectonic’ is used in this instance as a genetic descriptor based upon the comparison with Phanerozoic granitoid suites formed in such a setting after collisional orogenesis. Contrary to the suggestion of previous studies, a subduction-related arc setting is not readily reconcilable with the chemical and mineralogical characteristics of the Tunkillia Suite. Refereed/Peer-reviewed

U–Pb zircon analyses from a series of orthogneisses sampled in drill core in the northern Gawler Craton provide crystallisation ages at ca 1775–1750 Ma, which is an uncommon age in the Gawler Craton. Metamorphic zircon and monazite give ages of ca 1730–1710 Ma indicating that the igneous protoliths underwent metamorphism during the craton-wide Kimban Orogeny. Isotopic Hf zircon data show that 1780–1750 Ma zircons are somewhat evolved with initial εHf values –4 to +0.9, and model ages of ca 2.3 to 2.2 Ga. Isotopic whole rock Sm–Nd values from most samples have relatively evolved initial εNd values of –3.7 to –1.4. In contrast, a mafic unit from drill hole Middle Bore 1 has a juvenile isotopic signature with initial εHf zircon values of ca +5.2 to +8.2, and initial εNd values of ∼+3.5 to +3.8. The presence of 1775–1750 Ma zircon forming magmatic rocks in the northern Gawler Craton provides a possible source for similarly aged detrital zircons in Paleoproterozoic basin systems of the Gawler Craton and adjacent Curnamona Province. Previous provenance studies on these Paleoproterozoic basins have appealed to the Arunta Region of the North Australian Craton to provide 1780–1750 Ma detrital zircons, and isotopically and geochemically similar basin fill. The orthogneisses in the northern Gawler Craton also match the source criteria and display geochemical similarities between coeval magmatism in the Arunta Region of the North Australian Craton, providing further support for paleogeographic reconstructions that link the Gawler Craton and North Australian Craton during the Paleoproterozoic. Refereed/Peer-reviewed

Tectonic models for the latest Paleoproterozoic to earliest Mesoproterozoic evolution of eastern Australia (circa 1620-1500 Ma) are diverse and either emphasize plume or plate margin activity, neither of which satisfactorily explains all geological observations. The dichotomy is largely attributed to geochemical, spatial and temporal data that suggest voluminous A-type felsic magmas are plume related, whereas distribution of arc-related magmas and intense orogenic overprint suggest plate margin activity. The salient geological events include arc-related magmatism at circa 1620-1610 Ma followed by a magmatic hiatus coincident with north-south crustal shortening (1610-1590 Ma) and a magmatic flare-up of A-type felsic magmas throughout the Gawler Craton (circa 1595-1575 Ma). These magmas form the oldest component of a northward younging hot spot track that extends to the Mount Isa Inlier. At circa 1590-1550 Ma, arc magmatism resumed along the northern margin of the Gawler Craton and the rest of eastern Australia records a 90 degrees shift in the regional shortening direction related to activity along the eastern margin of the Australian continent. A plume-modified orogenic setting satisfies all of the spatial and temporal relationships between magma generation and orogenic activity. In this model, the Gawler Craton and the adjacent subduction zone migrated over a mantle plume (circa 1620-1610 Ma). Resultant flat subduction caused transient orogenesis (1610-1595 Ma) in the overriding plate. Slab delamination and thermal assimilation of the plume and the subducting slab caused a switch to crustal extension in the overriding plate, resulting in extensive mantle-derived and crustal melting in the Gawler Craton (1595-1575 Ma). Refereed/Peer-reviewed

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 uncerta...

Thermoluminescence research over the last three years has reached the point that radiation effects can be recognized in natural minerals, among which quartz ideally suited because of its small variation in chemical composition. The major radiation-related effects of quartz are sensitization (increasing the TL efficiency of the test dose) and a high temperature shift of TL glow peaks with increasing radiation doses. Those two criteria have been used to assess the TL glow curves of quartz obtained from samples near a Carpentarian unconformity in Eyre Peninsula, South Australia. The TL results indicate that radiation affected a zone of narrow (50 m) width of Lower Proterozoic rocks occurring immediately under the unconformity sediments of Carpentarian age. Vertical drill holes cutting through the unconformity surface yielded sample material which demonstrated diminishing radiation effects away from the unconformity. Maximal radiation effects, which are compatible with an uranium content of 100 ppm residing in the zone over a period 1 400 Ma, are confined to the Carpentarian unconformity and its immediate vicinity. The results indicate that the mineralization took place under a Carpentarian cover, and was not sourced in the Lower Proterozoic metamorphics. From the homogeneous distribution of radiation effects it seems likely that the mineralization spread under the cover and only penetrated greater depths in shear zones. In areas where erosion has removed the Carpentarian cover and part of the metamorphic rocks under it, those shear zones are the only rocks affected by radiation., Durant les trois dernières années, les recherches sur la thermoluminescence ont permis de reconnaître les effets des radiations ionisantes dans les minéraux naturels. Le quartz est un minéral idéal pour cette étude à cause de ses variations minimes de composition chimique. Les principaux effets des radiations sur le quartz comprennent la sensibilisation (en augmentant l'efficacité de TL pour une dose expérimentale) et le déplacement des courbes de TL vers les hautes températures lors de l'augmentation des doses de radiation. Ces deux critères sont utilisés pour apprécier les résultats d'une étude de TL des quartz de roches métamorphiques et de grès, situés près d'une discordance d'âge Carpentarien dans la péninsule d'Eyre (Australie du Sud). Les résultats indiquent que les effets de l'irradiation sont limités à une zone assez étroite (moins de 50 mètres) juste au-dessous de la discordance Carpentarienne dans les roches Protérozoïques Inférieures. Les sondages verticaux qui ont traversé la surface de discordance indiquent que les effets de l'irradiation décroissent en s'éloignant de celle-ci. L'effet maximal de l'irradiation peut être expliqué par une concentration maximale d'uranium de 100 ppm pour un temps de résidence de 1 400 Ma. Les résultats démontrent que la minéralisation uranifère s'est mise en place sous la couverture sédimentaire Carpentarienne et n'est pas issue des métamorphites du Protérozoïque Inférieur. La répartition homogène des effets de l'irradiation montre que la minéralisation s'est distribuée horizontalement dans la couverture Carpentarienne et a pénétré seulement à la faveur de zones de cisaillement dans les roches Protérozoïques. Dans les zones où la couverture Carpentarienne a été érodée, les zones de cisaillement sont les seules roches affectées par une irradiation., Ypma Petrus Johannes Maria, Hochman Mark B. M. A thermoluminescence study of the rôle of a middle proterozoic unconformity in controlling uranium mineralization, as shown at Eyre Peninsula, South Australia. In: Bulletin de Minéralogie, volume 110, 2-3, 1987. Les mécanismes de concentration de l'uranium dans les environnements géologiques.