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Large-scale mantle convective processes are commonly reflected in the emplacement of Large Igneous Provinces (LIPs). These are high-volume, short-duration magmatic events consisting mainly of extensive flood basalts and their associated plumbing systems. One of the most voluminous LIPs in the geological record is the ~ 2.06 billion-year-old Bushveld Igneous Complex of South Africa (BIC), one of the most mineralised magmatic complexes on Earth. Surprisingly, the known geographic envelope of magmatism related to the BIC is limited to a series of satellite intrusions in southern Africa and has not been traced further afield. This appears inconsistent with the inferred large size of the BIC event. Here, we present new radiometric ages for alkaline magmatism in the Archean Yilgarn Craton (Western Australia), which overlap the emplacement age of the BIC and indicate a much more extensive geographic footprint of the BIC magmatic event. To assess plume involvement at this distance, we present numerical simulations of mantle plume impingement at the base of the lithosphere, and constrain a relationship between the radial extent of volcanism versus time, excess temperature and plume size. These simulations suggest that the thermal influence of large plume events could extend for thousands of km within a few million years, and produce widespread alkaline magmatism, crustal extension potentially leading to continental break-up, and large ore deposits in distal sectors. Our results imply that superplumes may produce very extensive and diverse magmatic and metallogenic provinces, which may now be preserved in widely-dispersed continental blocks.

© 2017 Extensional episodes in Precambrian orogens are often difficult to decipher because of subsequent orogenesis and intracontinental reworking. Here, we use geochemical and geochronological constraints of a suite of preserved mafic–ultramafic rocks in the Paleoproterozoic Capricorn Orogen of Western Australia to reveal ophiolites, continental ribbons and aborted rifts. The Capricorn Orogen separates the Archean Yilgarn and Pilbara cratons and includes mafic–ultramafic rocks of the fault-bounded Trillbar Complex and Bryah Sub-basin. The Trillbar Complex is situated within a fault wedge between the Yilgarn Craton and a reworked portion of the craton to the north (Yarlarweelor Gneiss Complex), and has been variously interpreted as an obducted ophiolite, oceanic plateau or continental rift-related magmatic suite. In this study, a new U–Pb zircon age of 2069 ± 9 Ma from the Trillbar Complex indicates that it is at least 40 Myr older than the mafic and ultramafic rocks of the Bryah Sub-basin, with which it has previously been linked. The Trillbar Complex is characterised by E-MORB-like signatures, hydrous crystallization and a lack of crustal contamination, and probably formed in a mid-ocean ridge or, alternatively, an oceanic intraplate setting. Conversely, the 2030–1990 Ma mafic and ultramafic rocks in the Bryah Sub-basin show evidence of crustal contamination and are interpreted to have formed in a continental rift setting. Moreover, there is no evidence for boninites in the Bryah Sub-basin and, therefore, no justification for invoking a fore-arc setting. Thus, these pieces of evidence reveal a different tectonic and geodynamic origin for the Trillbar Complex compared to the Bryah Sub-basin rocks. The tectonic setting for the Trillbar Complex requires oceanic crust to have existed between the Yilgarn Craton and the Yarlarweelor Gneiss Complex. However, almost identical Archean histories of these crustal blocks support a proximal origin for the Yarlarweelor Gneiss C

© 2017 A regional tectonic model is presented for the formation and evolution of Paleoproterozoic basins over the northern Yilgarn Craton, integrating new and published regional geological, geochronological, geochemical and geophysical data. The basins formed as a response to both extensional and compressional processes in the early Paleoproterozoic along the craton margin. Early rifting and basin formation coincided with the Ophthalmia Orogeny, the result of the convergence and accretion of the Archean to Proterozoic Glenburgh Terrane with the Pilbara Craton, and led to the formation of the Yerrida Basin at c. 2180 Ma as a single sub-basin containing the Windplain Group. This led to the eventual development of the Bryah and Mooloogool Sub-basins of the Yerrida Basin at c. 2030 Ma, and voluminous extrusion and intrusion of mafic rocks. The depth and nature of the Bryah Sub-basin suggests formation in response to rifting, with its orientation corresponding to the rift axis. Continued rifting along the northern Yilgarn margin resulted in subduction of the Yilgarn Craton beneath the composite Glenburgh–Pilbara craton. Eventual collision was marked by cessation of volcanism and rift-sediment deposition in the Bryah and Mooloogool Sub-basins, the onset of a pro-foreland basin (Padbury Basin) in the west, and approximately NE–SW rifting further east (the Earaheedy Basin), all at c. 2000 Ma. Banded iron-formation and granular iron-formation (Robinson Range and Frere Formations) was deposited much later (c. 1890 Ma) in a large basin that deepened from east to west, spanning the Earaheedy and Yerrida Basins. The deepest parts of this basin coincide with the Bryah Sub-basin, which was the most rifted portion of the Yilgarn Craton in this region. Deposition in all basins probably ceased with onset of the Capricorn Orogeny at c. 1820 Ma.

Abra is a major lead–silver–copper–gold deposit within the Bangemall Supergroup that has a total indicated and inferred resource estimate of 93 million tonnes at 4.0% lead and 10 g/t silver and 14 million tonnes at 0.6% copper and 0.5 g/t gold. The mineralization lies within the upper part of the locally defi ned Gap Well Formation, and in the lower part of the overlying West Creek Formation. These units correlate respectively with the Irregully and lower Kiangi Creek Formations of the Edmund Group.The Abra deposit is characterized by a funnel-shaped brecciated zone, interpreted as a breccia feeder-pipe, overlain by stratabound mineralization made up of the Red Zone, an underlying Black Zone, and a stringer (feeder) zone. The Red Zone is characterized by banded jaspilite, hematite, galena, pyrite, quartz, abundant barite, and siderite. The Black Zone consists of veins and rhythmically banded Pb, Zn, and minor Cu sulfi des, laminated and/or brecciated hematite, magnetite, Fe-rich carbonate, barite, and scheelite.In situ Sensitive high-resolution ion microprobe (SHRIMP) U–Pb geochronology of detrital zircon, monazite, and xenotime in sandstones from the Abra deposit yields a range of dates from c. 2450 Ma to c. 1675 Ma, consistent with results from previous detrital zircon studies. SHRIMP dating of hydrothermal monazite from the Abra deposit suggests that a mineralization event occurred at c. 1385 Ma. The presence of c. 1465 Ma metamorphic/hydrothermal monazite in sandstones from Abra indicates that the host rocks are older and therefore belong to the Edmund Group. SHRIMP geochronology of xenotime extracted from the Tangadee Rhyolite, which outcrops within the lower Kiangi Creek Formation close to the Abra deposit, yields two main age components corresponding to oscillatory-zoned cores and unzoned rims. The cores are interpreted as magmatic in origin and indicate a possible eruption age of c. 1235 Ma, whereas the rims are interpreted to record a later hydrothermal eve

The Gascoyne Complex in Western Australia is a major Proterozoic tectonic zone which separates the Archaean Pilbara and Yilgarn cratons and hosts a number of mineralisation styles including intrusion- and shear-zone-related Mo-Cu-W-Pb such as at the Minnie Creek batholith, carbonatite-related rare earth elements including U, such as the Gifford Creek igneous complex, scheelite skarns such as at Nardoo Well, Ta, Bi and Be pegmatites such as at Morrissey Hill and Cu-Pb-Zn(-Au) such as Mount James, Glenburgh and Star of Mangaroon. Multiple reworking episodes including complex (re)folding and tectonic disruption mean that the controls on known mineralisation have been poorly understood. The nature, timing and significance of at least four distinct events are discussed on the basis of mapping and U-Pb SIMS data., The Gascoyne Complex in Western Australia is a major Proterozoic tectonic zone which separates the Archaean Pilbara and Yilgarn cratons and hosts a number of mineralisation styles including intrusion- and shear-zone-related Mo-Cu-W-Pb such as at the Minnie Creek batholith, carbonatite-related rare earth elements including U, such as the Gifford Creek igneous complex, scheelite skarns such as at Nardoo Well, Ta, Bi and Be pegmatites such as at Morrissey Hill and Cu-Pb-Zn(-Au) such as Mount James, Glenburgh and Star of Mangaroon. Multiple reworking episodes including complex (re)folding and tectonic disruption mean that the controls on known mineralisation have been poorly understood. The nature, timing and significance of at least four distinct events are discussed on the basis of mapping and U-Pb SIMS data.

The deposit is a blind, stratabound sedimentary-rock hosted Fe-Pb-Zn- Ba-Cu(-Au-Ag-Bi-W) deposit located within the easterly trending Jillawarra rift sub-basin of the Mesoproterozoic Edmund Basin in Western Australia. The deposit is in the exploration stage and is estimated to contain 93 000 000 t of ore grading 4% Pb and 10 g/t Ag and 14 000 000 t at 0.62% Cu and 0.5 g/t Ag. The mineral system is characterised by several overprinting phases of hydrothermal activity from several stages of brecciation and fluidisation, barite and sulphide veining to barren low-temperature chalcedonic veining. Hydrothermal alteration minerals include multi-stage quartz, chlorite, prehnite, Fe-rich carbonate and albite. A preliminary genetic model is presented which indicates that there may be several hydrothermal breccia pipes each of which may be associated with distal haematite-barite chemical sediments and enhancing the prospectivity of the basin., The deposit is a blind, stratabound sedimentary-rock hosted Fe-Pb-Zn- Ba-Cu(-Au-Ag-Bi-W) deposit located within the easterly trending Jillawarra rift sub-basin of the Mesoproterozoic Edmund Basin in Western Australia. The deposit is in the exploration stage and is estimated to contain 93 000 000 t of ore grading 4% Pb and 10 g/t Ag and 14 000 000 t at 0.62% Cu and 0.5 g/t Ag. The mineral system is characterised by several overprinting phases of hydrothermal activity from several stages of brecciation and fluidisation, barite and sulphide veining to barren low-temperature chalcedonic veining. Hydrothermal alteration minerals include multi-stage quartz, chlorite, prehnite, Fe-rich carbonate and albite. A preliminary genetic model is presented which indicates that there may be several hydrothermal breccia pipes each of which may be associated with distal haematite-barite chemical sediments and enhancing the prospectivity of the basin.

The Palaeoproterozoic Earaheedy Basin is one of a series of basins that extend for about 700 km east-west and are part of the Capricorn Orogen, situated between the Archaean Pilbara and Yilgarn Cratons. The Earaheedy Basin contains sedimentary rocks that were deposited on the northern passive continental margin of the Yilgarn Craton, probably as a result of continental breakup at 1.8 Ga. The sedimentary rocks of the Earaheedy Group are divided into two Subgroups, Toloo and Miningarra, each representing different depositional environments and aggregating about 3000 m in thickeness. The Tooloo Subgroup consists of basal siliciclastic with minor platform carbonates, overlain by a 600-m-thick succession of Fe-rich rocks (granular iron-formation and hematitic shales). The Miningarra Subgroup is predominantly siliciclastic, but includes stromatolite-bearing carbonate sequences and was deposited during a more active depositional regime. Far field tectonic events at 1.76 and 1.65 Ga resulted in the deformation of the sedimentary package with progressive intensity from north to south, forming the Stanley Fold Belt and giving and overall asymmetric structure to the Basin. These events were followed by a large meteorite impact (Shoemaker Impact Structure), probably in the Neoproterozoic. The Earaheedy Basin is well endowed with Fe resources, represented by the granular iron-formation (Frere Formation, Tooloo Subgroup), particularly in the Stanly Fold Belt, where there was secondary enrichement.

North of the craton's present-day boundary are the Goodin, Marymia and Malmac inliers which represent Archaean granite-greenstone terranes and the northern extension of the Yilgarn craton. The inliers are located within a 700-km long belt of Palaeoproterozoic volcano-sedimentary and sedimentary basins, which are considered part of the Capricorn Orogen and include the Bryah-Padbury, Yerrida and Earaheedy basins. The metallogeny of the basins is characterised by a range of mineral systems formed during and as a result of the tectonic and magmatic events. Three broad groups of mineral systems are recognised. One group includes volcanogenic massive sulphides (Horseshoe Lights, Bryah Basin) and Fe and Mn deposits (Bryah and Earaheedy). The second group includes Mississippi Valley-type deposits such as the carbonate-hosted Zn-Pb deposits in the Yelma Formation (Earaheedy Basin) and the Magellan non-sulphide Pb deposit, where the only ore minerals are cerussite, coronodite and pyromorphite. The third group consists of structurally controlled, orogenic lodes including the orogenic lode-Au in the Peak Hill Schist, Bryah and Padbury groups., North of the craton's present-day boundary are the Goodin, Marymia and Malmac inliers which represent Archaean granite-greenstone terranes and the northern extension of the Yilgarn craton. The inliers are located within a 700-km long belt of Palaeoproterozoic volcano-sedimentary and sedimentary basins, which are considered part of the Capricorn Orogen and include the Bryah-Padbury, Yerrida and Earaheedy basins. The metallogeny of the basins is characterised by a range of mineral systems formed during and as a result of the tectonic and magmatic events. Three broad groups of mineral systems are recognised. One group includes volcanogenic massive sulphides (Horseshoe Lights, Bryah Basin) and Fe and Mn deposits (Bryah and Earaheedy). The second group includes Mississippi Valley-type deposits such as the carbonate-hosted Zn-Pb deposits in the Yelma Formation (Earaheedy Basin) and the Magellan non-sulphide Pb deposit, where the only ore minerals are cerussite, coronodite and pyromorphite. The third group consists of structurally controlled, orogenic lodes including the orogenic lode-Au in the Peak Hill Schist, Bryah and Padbury groups.

A drilling programme intersected 49 m of tholeiitic basalt lava flows at depths of 527-576 m. The lavas were named the Keene Basalt and erupted during deposition of the shallow-marine Kanpa Formation, a mixed carbonate-siliciclastic succession in the Neoproterozoic Buldya Group. Palaeontological and chemostratigraphic correlation of the Kanpa Formation with the Burra Group of the Adelaide Rift Complex suggests an age older than 700 Ma. Geochemical data indicate that the Keene basalt is of continental origin and shows a close similarity to mafic dykes near Mingary, South Australia. Petrographic and XRD analyses show that the basalt has been hydrothermally altered by interaction with seawater, and locally contains disseminated sulphides. Massive and disseminated sulphide mineralisation, similar to that of submarine systems, may exist., A drilling programme intersected 49 m of tholeiitic basalt lava flows at depths of 527-576 m. The lavas were named the Keene Basalt and erupted during deposition of the shallow-marine Kanpa Formation, a mixed carbonate-siliciclastic succession in the Neoproterozoic Buldya Group. Palaeontological and chemostratigraphic correlation of the Kanpa Formation with the Burra Group of the Adelaide Rift Complex suggests an age older than 700 Ma. Geochemical data indicate that the Keene basalt is of continental origin and shows a close similarity to mafic dykes near Mingary, South Australia. Petrographic and XRD analyses show that the basalt has been hydrothermally altered by interaction with seawater, and locally contains disseminated sulphides. Massive and disseminated sulphide mineralisation, similar to that of submarine systems, may exist.

The Terrestrial hydrothermal processes and systems reviewed are associated with submarine, sub-aerial and sub-volcanic settings, intra- continental rifts and geothermal springs. Systems that most closely approximate Martian conditions include the Dresser Formation and the Sulphur Springs Group in the Pilbara Craton, Western Australia. The East African rift system may be considered as an analogue for the great rift system of Valles Marineris on Mars. A summary of the geology of Mars is presented and the types of hydrothermal systems that may occur are discussed, in particular around Tharsis volcanoes and caldera floors and in fractures and rift valleys. The discovery of crystalline haematite and sulphate deposits indicates chemical precipitation analogous to that of banded iron formation and/or hot spring sinter-like deposits. The interaction of hot magmas with the cryosphere is proposed as a mechanism to explain many of the surface features and a model is presented for the widespread deposition of sulphates as hydrothermal precipitates, generated through the interaction of magmatic H2S in hydrothermal solutions with water in the cryosphere., The Terrestrial hydrothermal processes and systems reviewed are associated with submarine, sub-aerial and sub-volcanic settings, intra- continental rifts and geothermal springs. Systems that most closely approximate Martian conditions include the Dresser Formation and the Sulphur Springs Group in the Pilbara Craton, Western Australia. The East African rift system may be considered as an analogue for the great rift system of Valles Marineris on Mars. A summary of the geology of Mars is presented and the types of hydrothermal systems that may occur are discussed, in particular around Tharsis volcanoes and caldera floors and in fractures and rift valleys. The discovery of crystalline haematite and sulphate deposits indicates chemical precipitation analogous to that of banded iron formation and/or hot spring sinter-like deposits. The interaction of hot magmas with the cryosphere is proposed as a mechanism to explain many of the surface features and a model is presented for the widespread deposition of sulphates as hydrothermal precipitates, generated through the interaction of magmatic H2S in hydrothermal solutions with water in the cryosphere.

Meteorite impacts cause conversion of kinetic energy into thermal energy. Part of this thermal energy is used to form a melt sheet, part is dissipated to heat the target rocks and these together with the hot rocks that elastically rebound from the depth of several kilometres (central uplift) activate hydrothermal circulation. Impact-generated hydrothermal systems have been documented from several impact structures world-wide. Three Australian examples—Shoemaker, Woodleigh and Yarrabubba—provide evidence of hydrothermal fluid flow both within and around the structures. Field observations, and petrographic and geochemical data suggest a common evolutionary trend of post-impact hydrothermal activity from early high-temperature alkali metasomatism to a later lower temperature H+ metasomatism, resulting in the overprinting by hydrous mineral assemblages. Hydrothermal systems activated by meteorite-impact events are important because they may also form economic mineral deposits, as is documented for several impact structures in the world. A working model of hydrothermal circulation in terrestrial impact structures posits two main stages: (i) initial high-temperature fluids percolate downward causing widespread alkali metasomatism of the shattered target rocks below the melt sheet, resulting in their modification to rocks of syenitic affinity; and (ii) inflow of meteoric water and progressive cooling of the melt sheet leads to a lower temperature stage, in which hydrothermal fluid flow tends to move upward, resulting in mineral assemblages and alteration patterns that resemble those of epithermal systems. In addition, these fluids can discharge at the surface as hot springs.