Zircon U-Pb ages, εHf(t) and δ18O isotopic data, geochemistry and limited Sm-Nd results mostly from deep basement drill cores from undercover parts of the Thomson Orogen, provide strong temporal links with outcropping regions of the orogen as well as important clues for its evolution and relationship with the Lachlan Orogen. SHRIMP U–Pb ages from three Early Ordovician volcanic samples and one granite from the undercover, Thomson Orogen shows that magmatism of this age is widespread across the central, undercover regions of the orogen and occurred in a narrow time-window between 480 Ma and 470 Ma. These rocks have evolved, εHf(t)zrn (-6.26 to -12.18), εNd (-7.1 to -11.3), and supracrustal δ18Ozrn (7.01–8.50‰) which is in stark contrast to the Early Ordovician rocks in the Lachlan Orogen, that are isotopically juvenile. Two samples have latest Silurian to earliest Devonian ages (1586685 DIO Ella 1; 425.4 ± 6.6 Ma and 2122055 Hungerford Granite; 419.1 ± 2.5) and coincide with a major period of intrusive magmatism in the southern Thomson and the Eastern and Central Lachlan Orogen. These samples have evolved εHf(t)zrn (-4.62 to -6.42) and supracrustal δ18Ozrn (9.26–10.29‰) which is similar to Lachlan Orogen rocks emplaced during this time. Four samples have mid Early to early Late Devonian ages (408–382 Ma) and appear to have been emplaced in a generally extensional tectonic regime. Two of these are from the Gumbardo Formation (1682891 PPC Carlow 1 and 1682892 PPC Gumbardo 1), the basal unit of the Adavale Basin, and constrain its opening to between 408 Ma and 403 Ma. The other two samples (1585223 AAE Towerhill 1 and 2122056 Currawinya Granite) have ages of ca. 382 Ma. These latter samples generally show a shift towards more juvenile εHf(t)zrn and mantle-like δ18Ozrn values, a trend that is also seen in rocks of this age in the Lachlan Orogen. Collectively, zircon Hf and O isotopes show that magmatism in the central, undercover part of the Thomson Orogen was initially derived from isotopically evolved magma sources but progressed to more juvenile sources during the Devonian. Furthermore, it appears that samples from the Thomson Orogen may fall along two distinct Hf-O isotopic mixing trends. One trend, appears to have incorporated an older (more evolved) supracrustal component and occurs in the northern two-thirds of the Thomson Orogen, while the other trend is generally less evolved and occurs in the southern third of the Thomson Orogen and is geographically continuous with the Lachlan Orogen. <b>Citation:</b> A. J. Cross, D. J. Purdy, D. C. Champion, D. D. Brown, C. Siégel & R. A. Armstrong (2018) Insights into the evolution of the Thomson Orogen from geochronology, geochemistry, and zircon isotopic studies of magmatic rocks, <i>Australian Journal of Earth Sciences</i>, 65:7-8, 987-1008, DOI: 10.1080/08120099.2018.1515791

Mount Marumba covers the central part of Arnhem Land, which is occupied mainly by the Katherine River, Mount Rigg and Roper Groups of the Palaeoproterozoic to Mesoproterozoic McArthur Basin succession. These units consist of marine and non-marine clastics, carbonates, and lesser volcanics, that are extensively intruded by dolerite and some microgranite. Recent mapping and associated structural, geophysical, geochemical and geochronological studies have resulted in a number of important new findings: (1) The Jimbu Microgranite intruded the Katherine River Group at ~1710 Ma, causing updoming of surrounding sediments to form a number of structural domes. (2) An age of 1324 Ma has been obtained from the Derim Derim Dolerite, intruding the Roper Group, that provides improved constraints on the ages of sedimentation and deformation. (3) An aeolian facies has been recognised within the Gundy Sandstone. (4) The former Kombolgie Formation has been elevated to a Subgroup, subdivded into component formations, and extended upwards to include the McKay Sandstone. (5) A major impact structure, the Gulpuliyul Structure, was formed between ~1600 and 1324 Ma.The mapping and interpretation took advantage of the full complement of regional gravity, airborne magnetic and gamma-ray spectometric datasets now available. Concealed dykes, lineaments and sill edges are overprinted on the surface geology in magenta. In addition, the map features 1:1 000 000-scale marginal figures of an enhanced total magnetic intensity image and a gamma-ray spectroscopy image. Two cross-sections highlight the salient features of the stratigraphy and structure. The 84-page Explanatory Notes presents descriptions of the geology in some detail, in sections on the regional geological setting, stratigraphy, geophysics, structure, geological history and economic geology. The text is supported by several tables and numerous black-and-white photographs and line drawings, as well as some full-colour images.

New and existing Sm-Nd whole rock isotope data and U-Pb zircon ages from sedimentary rocks in several Australian Proterozoic Provinces hosting Zn-Pb mineralisation show a distinct transition that corresponds to a change from evolved sediment sources to more juvenile sedimentary sources at ~1650 Ma. This Sm-Nd isotopic change has been documented in the Eastern and Western Successions of the Mount Isa Inlier, the Etheridge Province of the Georgetown Inlier. A similar transition at ~1650 Ma has also been documented in the Broken Hill and Olary Domains of the Curnamona Province (Barovich and Hand 2008) and defines a continental-scale isotopic signal. The world-class, sediment-hosted Mt Isa and Hilton-George Fisher Zn-Pb Mt Isa-style deposits in the Western Mount Isa Inlier occur above the transition in sediments derived from more juvenile sources. In contrast, Pb-Zn-Ag Broken Hill-style deposits, including the Broken Hill (Curnamona), Cannington (Isa), Mount Misery (now Chloe) and Railway Flat deposits (Georgetown Inlier) (Carr et al. 2004) occur below this ~1650 Ma transition in sediments which have a much more evolved source.

Beginning in the Archean, the continent of Australia evolved to its present configuration through the accretion and assembly of several smaller continental blocks and terranes at its margins. Australia usually grew by convergent plate margin processes, such as arc-continent collision, continent-continent collision or through accretionary processes at subduction zones. The accretion of several island arcs to the Australian continent, through arc-continent collisions, played an important role in this process, and the geodynamic implications of some Archean and Proterozoic island arcs recognised in Australia will be discussed here.

The Glenloth Granite is an icon of South Australian geology, having been the site of some of the earliest gold workings in the central portion of what is now known as the Gawler Craton and the subject of some of the first radiometric age determinations in the 1960's. The Glenloth Granite forms part of the Neoarchaean to earliest Palaeoproterozoic belt of supracrustals and associated intrusives known as the Mulgathing Complex, which includes mafic to ultramafic (komatiitic) volcanics. Inferred to be syn-tectonic in nature in the original 1:250 000 scale mapping of the region, new SHRIMP data shows that the Glenloth Granite was emplaced at 2508 +/- 2 Ma, during period of magmatism that predates the ca. 2470 - 2420 Ma Sleafordian Orogeny. This orogenic event reworked the Glenloth Granite in to magmatitic gneiss and is responsible for two main generations of metamorphic zircon growth at 2453 +/- 4 Ma and 2427 +/- 3 Ma, likely reflecting initial prograde metamorphism followed by migmatite formation during biotite dehydration reactions, as has been documented from elsewhere in the Mulgathing Complex.

New provenance data from Palaeoproterozoic and possible Archaean sedimentary units in the central eastern Gawler Craton forms part of a growing dataset suggesting that the Gawler Craton shares important basin formation and tectonic time lines with the adjacent Curnamona Province and the Isan Inlier in northern Australia. U-Pb dating of detrital zircons from the Eba Formation (previously mapped as Tarcoola Formation), yield exclusively Archaean ages (~2530-3300 Ma). This is consistent with whole rock Nd and zircon Hf isotopic data for the Eba Formation which have evolved compositions. Elsewhere in the eastern Gawler Craton, cover sequences historically considered to be Palaeoproterozoic in age also contain exclusively Neo and Meso Archaean aged detrital zircons (Reid et al, 2009 Econ. Geol.; Szpunar et al, 2007, SGTSG). The absence of Palaeoproterozoic detrital grains in several differently mapped sequences (including the Eba Formation) despite the proximity of voluminous Palaeoproterozoic rock units, suggests that the Eba Formation may be part of a Neo-Archaean or early Palaeoproterozoic cover sequence derived from erosion of a complex Archaean aged source region. The Labyrinth Formation unconformably overlies the Eba Quartzite, and contains rhyolitic units that constrain deposition to 1715 ± 9 Ma (Fanning et al., 2007; PIRSA Bulletin 55). This age is identical to the timing of deposition of the lower Willyama Supergroup in the adjacent Curnamona Province. Detrital zircon ages in the Labyrinth Formation range from NeoArchaean to Palaeoproterozoic, and are consistent with derivation from > 1715 Ma components of the Gawler Craton. Isotopic zircon Hf data and whole rock Nd data also suggest a source region with a mixed crustal evolution (-Nd -4.5 to -6), consistent with what is known about the Gawler Craton. Compared to the Lower Willyama Supergroup, the Labyrinth Formation has a source more obviously reconcilable with the Gawler Craton.

The Mulgathing Complex within the Gawler Craton, South Australia, preserves evidence for magmatism, sedimentation and metamorphism spanning the transition between the Neoarchean and Paleoproterozoic (c. 2555 - 2410 Ma). Prior to this study, limited data has been available to constrain the timing of these tectonothermal events. Consequently there has been uncertainty regarding the timing of sedimentation and magmatism relative to the pervasive deformation and metamorphism that has affected this region. We report SHRIMP zircon U-Pb dating of metamorphosed sedimentary and magmatic rocks from the Mulgathing Complex, central Gawler Craton. The data show that etasedimentary gneisses (Christie Gneiss) preserve an inferred maximum depositional age of ca. 2480 Ma, in contrast to previous studies that have suggests deposition had occurred ca. 2510 Ma. The oldest metamorphic zircons in our data are ca. 2465 Ma, thus indicating there was a time interval of less than 15 Myr between the cessation of sedimentation and the occurrence of metamorphism at high metamorphic grade. Metamorphic zircons have a range of ages, from ca. 2465 and ca. 2415 Ma, consistent with a period of ca. 50 Myr during which high-grade metamorphism occurred. Mafic and felsic intrusions have ages that range from ca. 2520 Ma to 2460 Ma, indicating magmatism occurred during sedimentation and continued during the early stages of metamorphism and deformation of these rocks. The abundance of mafic intrusions and its temporal overlap with the sedimentation within the Mulgathing Complex may indicate that the overall tectonic regime involved some form of iithospheric extension. The Mulgathing Complex shows temporal similarities with only a few terranes in particular the Saask Craton, Canada, regions within the North China Craton, and to some extent cratonic regions within northern Australia.

Aspects of the tectonic history of Paleo- to Mesoproterozoic Australia are recorded by metasedimentary basins in the Mt Isa, Etheridge Provinces, and Coen Inlier in northern Australia and in the Curnamona Province of southern Australia. These deformed and metamorphosed basins are interpreted to have been deposited in a tectonically-linked system based on similarities in depositional ages and stratigraphy (Giles at al 2002). Neodymium isotope compositions of sediments and felsic volcanics, when combined with U-Pb geochronology, are independent data that are important tools for inferring tectonic setting, palaeogeography and sediment provenance in deformed and metamorphosed terrains.

The Mount Painter Province is located in the northern Flinders Ranges, South Australia and comprises deformed Proterozoic metasedimentary and igneous rocks.

Australia's Large Igneous Provinces (LIPs) span most of Earth's geological history, ranging from Early Archean to Recent. LIPs in continental Australia are represented by continental flood basalts, fragments of oceanic plateaux, layered mafic-ultramafic intrusions, sill complexes and dyke swarms. It is only in the last decade that geologists have started to focus on LIPs in Australia, mainly from the perspective of their mineral potential, particularly after the discovery of the Nebo-Babel Ni-Cu-PGE deposit in the West Musgrave Province, central Australia. The list of LIPs increased by including other well-known igneous provinces, such as the Fortescue, Warakurna, Hart-Carson, Kalkarindji (formerly known as Antrim Plateau Volcanics) and various dyke swarms (e.g., Widgiemooltha, Marnda Moorn, Gairdner). The Bunbury Basalt, although only covering a small area in the Cape Naturaliste-Cape Leeuwin peninsula, joined the list of LIPs, due to its age links with the huge Kerguelen oceanic plateau magmatism. As indicated by the world-class Nebo-Babel deposit and further discoveries in the West Musgrave and in the Kimberley region, the mineral potential of LIPs is very high. In the case of orthomagmatic mineral systems, the selection of areas or specific intrusions requires focusing on isotope systematics and trace- and major-element geochemical trends to filter out mafic-ultramafic intrusions that may not have undergone sulphur saturation from those that have experienced sulphur saturation from processes, such as crustal contamination. In eastern Australia, there are two major volcanic provinces: the Early Cretaceous Whitsunday volcanic province, which is a good example of a silicic LIP, and a 4400 km long belt characterised by recent (youngest volcano is 4600 years ago) intraplate alkaline volcanism. The mineral potential associated with these provinces is as yet not fully assessed.