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Mercury (Hg) enrichments in ancient sediments have been used as a proxy of volcanism, especially large igneous province (LIP) eruptions. However, considering the existence of other potential Hg sources besides volcanoes and the diverse factors (e.g., organic matters, clay minerals, sulfide minerals and Fe oxides) that can affect Hg sequestration, there are considerable uncertainties to simply regard sedimentary Hg anomalies as signatures of volcanic activities. Mercury stable isotopes, a promising tool for tracing the origins and transformations of Hg, have been increasingly used for determining the causes of Hg spikes and understanding the geochemical behavior of Hg in the geologic record. To date, lots of researches have applied Hg concentrations and Hg isotopes to identify LIP volcanisms linking with significant geological events such as mass extinctions, ocean anoxic events and other environmental perturbations that mainly occurred in the Phanerozoic. However, the results in previous studies clearly show that not all Hg enrichments are derived from volcanic inputs, which emphasize the need for more caution in using Hg as a fingerprint of volcanism. With a better understanding of Hg isotopes in the future, there will be important implications for Hg isotopes to reconstruct volcanic activities in the rock records and their impacts on biological evolution. [ABSTRACT FROM AUTHOR]

Sedimentary carbonates are known to be carried into the deep mantle by subducted slabs, and studies on mantle‐derived magmas have attempted to trace the recycled carbonate in their mantle source. However, the final depth of storage of recycled carbonate and the role of recycled carbonate in the partial melting of mantle remain controversial. Peralkaline‐carbonatite suites are considered to have been derived from a carbonated mantle source and are windows to evaluate carbon in the mantle. In this study, we report the Zn isotopic compositions of a peralkaline‐carbonatite suite from the Tarim Large Igneous Province (Tarim LIP). The peralkaline‐carbonatite suite has heavier δ66Zn than normal mantle with δ66Zn of 0.34–0.40 ‰ for nephelinite, 0.35–0.47 ‰ for aillikite, 0.51–0.55 ‰ for nepheline syenite, 0.58–0.67 ‰ for calciocarbonatite and 0.38–0.56 ‰ for magnesiocarbonatite. The heavy Zn isotopic compositions of the peralkaline‐carbonatite suite in the Wajilitag complex suggest the incorporation of recycled carbonate‐bearing materials into the deep mantle. We infer that the calciocarbonatite was produced by the initial partial melting of subducted MgSiO3/MgO + C‐bearing carbonated eclogite, whereas the magnesiocarbonatite, aillikite, and nephelinite are considered as reacted melts between carbonated eclogite‐derived melts and peridotite. The heavy Zn isotopic compositions of the nepheline syenite are attributed to fractional crystallization from nephelinite magma in the magma reservoir. Our study highlights the incorporation of carbonated eclogite as an important agent of recycled carbon in the deep mantle and interactions between carbonated eclogite‐derived melts and peridotite lead to the complex lithological heterogeneities in the peralkaline‐carbonatite suite in Tarim LIP. Key Points: Zn isotopes of the peralkaline‐carbonatite suite in TLIP show that the subducted carbon is recycled in the form of MgSiO3/MgO + CThe carbonated eclogite‐derived melt‐peridotite reaction as the key for the formation of aillikite and nephelinite in TLIPThe incorporation of carbonated eclogite as an important source of recycled carbon in the deep mantle [ABSTRACT FROM AUTHOR]

Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes including continental fragments. Here, we investigate the rifting of William's Ridge (Kerguelen Plateau) and Broken Ridge, components of the Kerguelen Large Igneous Province now situated in the Southeast Indian Ocean, and incorporate these end members into the deformation migration concept for rifted margins. We use multichannel seismic reflection profiles and data from scientific drill cores acquired on both conjugate margins to propose, for the first time, a combined tectono‐stratigraphic framework. We interpret seismic patterns, tectonic features, and magnetic anomaly picks to determine an across‐strike structural domain classification. This interpretation considers the rift system overall to be "magma‐poor" despite being located proximal to the Kerguelen plume but suggests that syn‐rift interaction between the Kerguelen mantle plume and the lithospheric structure of William's Ridge and Broken Ridge has controlled the along‐strike segmentation of both conjugates. We integrate seismic reflection and bathymetric data to test the hypothesis of predominantly transform motion, between the Australian and Antarctic plates, in Late Cretaceous and Paleogene time. Plain Language Summary: Numerous investigations into the evolution of continental rift systems have advanced understanding of how the Earth's crust stretches and may eventually result in the formation of new ocean basins. However, these studies have not considered the case of thick mafic crust, sometimes including continental fragments. Here we focus on William's Ridge (Kerguelen Plateau) and Broken Ridge, formed as a single feature, in the Southern Indian Ocean. We investigate how these features rifted, broke apart, and separated in the current conceptual framework of deformation migration. We use multichannel seismic reflection data, multibeam bathymetry data, drilling results, and magnetics data to interpret their structure, stratigraphy, and tectonics with the goal of explaining how the features evolved in time and space. Surprisingly, we find evidence for relatively weak magmatism despite the features being located near a mantle hotspot. Nevertheless, we suggest that the mantle hotspot influenced how the crust broke apart along different segments of the features' conjugate margins. We also find that the Australia and Antarctic tectonic plates, on which the features are now located, were moving laterally with respect to each other while rifting and breaking apart. Key Points: The first consistent tectono‐stratigraphic framework across the Kerguelen Plateau‐Broken Ridge rifted margins is presentedWilliam's Ridge‐Broken Ridge rifted margins are defined as "magma‐poor" and classified following the deformation migration modelThe Kerguelen mantle plume controls along‐strike segmentation and promotes syn‐rift transform motion in William's Ridge‐Broken Ridge [ABSTRACT FROM AUTHOR]

Theory regarding the causation of mass extinctions is in need of systematization, which is the focus of this contribution. Every mass extinction has both an ultimate cause, i.e. the trigger that leads to various climato-environmental changes, and one or more proximate cause(s), i.e. the specific climato-environmental changes that result in elevated biotic mortality. With regard to ultimate causes, strong cases can be made that bolide (i.e. meteor) impacts, large igneous province (LIP) eruptions and bioevolutionary events have each triggered one or more of the Phanerozoic Big Five mass extinctions, and that tectono-oceanic changes have triggered some second-order extinction events. Apart from bolide impacts, other astronomical triggers (e.g. solar flares, gamma bursts and supernova explosions) remain entirely in the realm of speculation. With regard to proximate mechanisms, most extinctions are related to either carbon-release or carbon-burial processes, the former being associated with climatic warming, ocean acidification, reduced marine productivity and lower carbonate δ13C values, and the latter with climatic cooling, increased marine productivity and higher carbonate δ13C values. Environmental parameters such as marine redox conditions and terrestrial weathering intensity do not show consistent relationships with carbon-cycle changes. In this context, mass extinction causation can be usefully classified using a matrix of ultimate and proximate factors. Among the Big Five mass extinctions, the end-Cretaceous biocrisis is an example of a bolide-triggered carbon-release event, the end-Permian and end-Triassic biocrises are examples of LIP-triggered carbon-release events, and the Late Ordovician and Late Devonian biocrises are examples of bioevolution-triggered carbon-burial events. Whereas the bolide-impact and LIP-eruption mechanisms appear to invariably cause carbon release, bioevolutionary triggers can result in variable carbon-cycle changes, e.g. carbon burial during the Late Ordovician and Late Devonian events, carbon release associated with modern anthropogenic climate warming, and little to no carbon-cycle impact due to certain types of ecosystem change (e.g. the advent of the first predators around the end-Ediacaran; the appearance of Paleolithic human hunters in Australasia and the Americas). Broadly speaking, studies of mass extinction causation have suffered from insufficiently critical thinking—an impartial survey of the extant evidence shows that (i) hypotheses of a common ultimate cause (e.g. bolide impacts or LIP eruptions) for all Big Five mass extinctions are suspect given manifest differences in patterns of environmental and biotic change among them; (ii) the Late Ordovician and Late Devonian events were associated with carbon burial and long-term climatic cooling, i.e. changes that are inconsistent with a bolide-impact or LIP-eruption mechanism; and (iii) claims of periodicity in Phanerozoic mass extinctions depended critically on the now-disproven idea that they shared a common extrinsic trigger (i.e. bolide impacts). [ABSTRACT FROM AUTHOR]

The Paraná-Etendeka Large Igneous Province (PELIP) is renowned for its massive and rapidly emplaced flood basalts that dominated the centre of the Gondwana supercontinent during the Early Cretaceous. However, little is currently understood about mafic explosive eruptions, which often occur simultaneously with effusive activity, as observed in young basaltic volcanism. Here, we describe the first well-preserved layer of basaltic tuff interbedded within the high-Ti basaltic lava sequence in the central part of the PELIP, Brazil. The Tapalam Tuff consists of basaltic juvenile glassy components, scoriaceous lapilli and coarse ash, with a cement containing clays, zeolites, carbonates, and iron oxides. The glassy sideromelane fragments range from well-rounded achneliths with smooth, curved surfaces to highly angular, cuspate-shaped or platy shards. Achnelith morphologies include broken droplets (Pele's tears), thread fragments (Pele's hair), dumbbells, needles, spheres, ovoids and reticulite. Elongated pyroclasts exhibit a flat orientation, and subtle bedding is defined by granulometric alternation. Our findings suggest the deposits were laid down proximal to the volcanic vent and likely indicate a fallout deposit associated with a fluid-dominated, high (hundreds of meters or more than 1 km) fountain similar to a Hawaiian-type eruption, fed by low-viscosity basaltic magma. Volcanic activity was therefore not exclusively effusive but also involved explosive eruptions, which may have significant implications for understanding PELIP's volcanic history and its relation to local and global environmental changes. [ABSTRACT FROM AUTHOR]

During the latest Mesoproterozoic–Early Neoproterozoic era, extensional regimes generated a number of sedimentary basins in various regions in the Sino-Korean Craton. Mantle-plume emplacements are widely recognized in the sedimentary strata as mafic dikes and sills of the Dashigou Large Igneous Province (LIP). The occurrence of Fe-rich redbeds is first reported in the Neoproterozoic Socheong Formation of the Sangwon Supergroup in the Pyeongnam Basin. Their geochemical and mineralogical characteristics indicate basin-wide Fe enrichment due to hydrothermal fluid input. The episodic yet repetitive hydrothermal injection into the basin generated short-lived anoxia, recorded as greenish-gray coloration in the ferruginous beds. This hydrothermal fluid was likely sourced from the mafic igneous activities involved in the Dashigou LIP. The redbeds can be utilized as key beds for intra- or inter-basinal stratigraphic correlation and to study the negative carbon isotope excursions that occurred in the genetically related basins in the region (e.g., the Sangwon, Xu-Huai, and Dalian basins). [ABSTRACT FROM AUTHOR]

The Lake Tana area is located within a complex volcano-tectonic basin on the northwestern Ethiopian plateau. The basin is underlain by a thick succession of Oligocene transitional basalts and sub-alkaline rhyolites overlain in places, particularly south of the lake, by Quaternary alkaline to mildly transitional basalts, and dotted with Oligo-Miocene trachyte domes and plugs. This paper presents the results of integrated field, petrographic, and major and trace element geochemical studies of the Lake Tana area volcanic rocks, with particular emphasis on the Oligocene basalts and rhyolites. The studies reveal a clear petrogenetic link between the Oligocene basalts and rhyolites. The Oligocene basalts are: (1) plagioclase, olivine, and/or pyroxene phyric; (2) show an overall decreasing trend in MgO, Fe2O3, and CaO with silica; (3) have relatively low Mg#, Ni and Cr contents and high Nb/La and Nb/Yb ratios; and (4) show LREE enriched and generally flat HREE patterns. All these imply the origin of the Oligocene basalts by shallow-level fractional crystallization of an enriched magma sourced at the asthenospheric mantle. The Oligocene rhyolites: (1) are enriched in incompatible while depleted in compatible trace elements, P and Ti; (2) show a strong negative Eu anomaly; (3) contain appreciable amounts of plagioclase, apatite, and Fe-Ti oxides; and (4) show clear geochemical similarity with well-constrained rhyolites from the Large Igneous Province (LIP) of the northwestern Ethiopian plateau. Low-pressure fractional crystallization of mantle-derived basaltic magma in crustal magma chambers explains the origin of these rhyolites. Our study further shows that the Oligocene basalts and rhyolites are co-genetic and the felsic rocks of the Lake Tana area are related differentiates of the flood basalt volcanism in the northwestern Ethiopian plateau. [ABSTRACT FROM AUTHOR]

The application of the olivine–spinel aluminum exchange thermometer to natural samples is limited by the restricted experimental data set on which it was calibrated. Here, we present a new data set of 46 high-temperature crystallization experiments and 21 reanalyzed published experiments, which we used to extend the calibration to higher and lower temperatures. The final calibration data set spans a range of conditions relevant to crustal and upper mantle processes: 1174–1606°C, 0.1–1350 MPa, QFM − 2.5 to QFM + 7.2 (oxygen fugacity, f O2, reported in log units relative to the quartz–fayalite–magnetite buffer, QFM), and 0–7.4 wt % H2Omelt. We propose three new models. The first is thermodynamically self-consistent, based on spinel Fe, Mg, Al, and Cr compositions and Al exchange between olivine and spinel. The second and third are empirical models that consider fewer elemental exchanges: the second uses only Al exchange and spinel compositions, whereas the third considers olivine–spinel Al and Cr exchange. All models include the modest effect of pressure on olivine-spinel equilibrium chemistry, whereas f O2 and water content have negligible effects. In general, as fewer elements are considered in the olivine–spinel exchange, the fit to experimental data worsens. Conversely, the associated decrease in model complexity improves their robustness against systematic errors when applied to natural crystal pairs: the thermodynamic model may underestimate crystallization temperatures in natural samples due to spinel subsolidus re-equilibration, whereas the empirical models (independent of Fe and Mg in spinel) are less sensitive to re-equilibration but yield temperatures with larger uncertainties. We applied a statistical test to select the most appropriate model for application to natural samples. When applied to lavas from mid-ocean ridges, Iceland, Skye, Emeishan, Etendeka, and Tortugal, our new temperature estimates are 30–100°C lower than previously proposed. The lower temperature estimates cause a lower mantle melting temperature and significant impacts on the mantle lithology constraints. [ABSTRACT FROM AUTHOR]

Large-volume silicic eruptions in large igneous provinces are unique in the geological record because there are no observed analogues. Their facies architecture do not strictly follow the diagnostic features proposed in the literature for rheomorphic ignimbrites and lava flows. The models proposed for their emplacement depend on conditions such as high temperature (> 950 °C) and low viscosity (< 106 Pa s) coupled with unusually high effusion rates. Low-Ti dacitic lavas from the Paraná-Etendeka Large Igneous Province (LIP) have a wide variety of morphologies and lithofacies on both sides of the Atlantic Ocean. A common facies association framework for the Caxias do Sul/Grootberg dacites (outcropping in Namibia and southern Brazil) include the presence of platy and thinly jointed facies with a columnar jointed massive core and an amygdaloidal upper facies, with an absence of basal breccia. In this work, we describe and interpret features observed in the basal portion of these silicic units, focusing on the thinly jointed facies. This basal facies includes what has been termed as "zebra-like banding." Zebra-like banding is an apparent structure that originates from a fracture network which involves horizontal and long first-order fractures, oblique and short second-order fractures, oblique short to long third-order fractures, and intersection zones of fourth-order structures. First-order fractures are related to pure shear, the second- and third-order fractures are Riedel shears, and the fourth-order structures represent angular contacts between different sets containing first-, second-, and third-order fractures. The combination of first-, second-, and third-order fractures evolves to shear lenses. The zebra-banding" is caused by oxidation/reduction halos developing in the host rock during post-emplacement fluid circulation along the fractures, culminating in precipitation of silica polymorphs and zeolite. The fracture system, including all orders of fracture, formed during late to post emplacement stages, and accommodated pure and simple shear in a ductile–brittle basal zone during oscillations in effusion rate. Fracturing of the basal zone, rather than the formation of basal breccia, demonstrates stress accumulation in this part of the flow and helps to explain why the presence of basal breccia is not a diagnostic feature in distinguishing large-volume silicic lava flows from rheomorphic ignimbrites. [ABSTRACT FROM AUTHOR]

Patterns of magma transport during the emplacement of Large Igneous Provinces (LIPs) are extremely important for the understanding of their formation. The Permian-Triassic Siberian Traps LIP is considered to be one of the largest in the Phanerozoic; however, mechanisms of magma transfer within and under the crust are still poorly studied. This problem is vital for the reconstruction of the dynamics of magmatic activity and eruption styles, ascertaining the position of magmatic centers and feeding zones, and conception of ore deposits genesis. Here, we present the detailed results of anisotropy of magnetic susceptibility measurements for lava flows and intrusions from the Noril'sk and Kulumbe regions (the northwestern Siberian platform). We reconstructed patterns of magma flow based on the magnetic fabric analysis of more than 100 sites. Distribution of the magnetic lineation in the studied intrusions and flows points out that the lateral magma flow of NW-SE directions was predominant. Our results support the idea of a magma-controlling role of Noril'sk-Kharaelakh and Imangda-Letninskiy regional fault zones. Furthermore, the reconstructed geometry of magma transport in intrusions is contrasting with that in the Angara-Taseeva depression (the southern part of the LIP) due to the presence of the long-lived mobile zones in the northwestern Siberian platform. [ABSTRACT FROM AUTHOR]

Cratons are the most mature parts of the continents on Earth and can remain stable for billions of years. Cratonic keels may be destroyed, for which a prime example is the eastern North China craton (NCC), which was removed during the Mesozoic. However, the critical stable state of the keel and the destroying mechanism of the rigid and buoyant cratonic roots remain enigmatic. Here, rhenium-osmium and neodymium isotope datasets from the eastern NCC open up a possible approach to reveal its evolution prior to the destruction. Two Re (rhenium) -depletion model age peaks of the peridotite xenoliths entrained by Phanerozoic basalts reconcile the ages of the large igneous provinces (LIPs) of Yanliao (ca. 1.3 Ga) and Xuhuai (ca. 0.92 Ga), respectively. This indicates that the mantle lithosphere of the eastern NCC has undergone metasomatism and growth during the emplacement of the two LIPs. The Proterozoic LIPs probably produced buoyant mantle residues that were then captured beneath thinned lithosphere regions. Such igneous processes occur at a depth of ~100 km and may induce the formation of weak zones (e.g. palaeo-mid-lithosphere discontinuity) partially within the rigid mantle lithosphere. The palaeo-weak zones might be rheologically unstable structures and probably reduced the stability of the craton, presenting as foci for potential later keel destruction. This provides evidence that LIP event may be another key factor for the intra-cratonic mantle lithosphere destruction. [ABSTRACT FROM AUTHOR]

This paper presents zircon U-Pb, REE and Hf data for Paleoproterozoic felsic volcanic rocks from the Colíder Group with outcrops in the southwestern Amazonian Craton. It is estimated that these rocks cover an area of 85,000 km2 with a volume of 2.7 × 106 km3. The Colíder volcanics are comprised of basalts, andesites and a variety of felsic rocks. The felsic rocks are characterized by rhyolite, andesite and dacite lavas with frequent intercalated pyroclastic and epiclastic deposits. Effusive and pyroclastic rocks are intruded in places by hypabyssal porphyritic rocks. The U-Pb ages obtained for the northeastern domain (1782–1776 Ma) are younger than the ages obtained for the southern domain (1800–1787 Ma). The NE volcanic facies show Hf TDM ages between 2.3 and 2.5 Ga (εHf from +1 to −3) and greater fractionation (Ce/Yb – 0.03–0.06) than the younger facies that has TDM from 2.4 to 2.7 Ga (εHf from −3 to −6) with Ce/Yb values of 0.025–0.030. The Hf isotope compositions, REE contents and U-Pb analyses suggest geographic (north-south) variations in composition, crystallization ages, and TDM age zonation during the generation of the Colíder large igneous province. [ABSTRACT FROM AUTHOR]

Devonian plants in Siberia present protracted pioneer succession. Research into the survivorship dynamics of early plant communities upon the palaeocontinent Angarida have demonstrated that transgression and volcanogenic nutrient influx were key to the survival of colonizing plants. Taxic proportions show that migrating taxa entered Angarida from the southwest, Kuznetsk and Minusinsk basins, dispersing across the continent in waves through central areas northwards. The patterns of dispersal are consistent throughout the Devonian. Increased nutrient load from the active pulses of the Viluy-Yakutsk Large Igneous Province, biogeomorphic ecosystem engineering and the increased biomass of Angaridan plants are assisted by Late Devonian transgression. These cumulative factors can be linked to the Late Devonian marine extinctions observed in Siberia. [ABSTRACT FROM AUTHOR]

Dichotomous high-Ti and low-Ti magmas are ubiquitous in large igneous provinces (LIPs). These magmas often form economically critical Fe–Ti oxide ores in layered intrusions via mechanisms that remain debated. To constrain the evolution of high-Ti and low-Ti basalts during fractionation, we performed stepwise equilibrium crystallization experiments at atmospheric pressure. We specifically aimed to quantify the influences of starting composition and oxygen fugacity (fO2) on phase stability, phase compositions, and the onset of silicate liquid immiscibility during cooling. Both types of magma crystallize similar phase assemblages at QFM (quartz–fayalite–magnetite thermodynamic equilibrium) and QFM + 2: olivine, clinopyroxene, plagioclase, Fe–Ti oxides, and whitlockite. Tridymite crystallizes late in experiments at QFM + 2. The starting composition exerts a strong influence on phase and melt compositions. High CaO and Al2O3 contents in the melt favor the early crystallization of plagioclase and enhance FeO enrichment before Fe–Ti oxide saturation. fO2 affects the composition and stability of Fe–Ti oxides, and high fO2 conditions may promote melt differentiation into the calc-alkaline field. Silicate liquid immiscibility occurs in both compositional trajectories, producing Fe-rich melt globules in equilibrium with Si-rich melts. Strong iron enrichment is not necessary for immiscibility to develop; unmixing also occurs in Fe depleted compositions. We propose a new parameterization to map the binodal surface in temperature-composition space that successfully fits the two-liquid field in experiments and natural immiscible compositions. Our results indicate that Fe–Ti oxide ores in layered intrusions associated with LIPs form by the segregation of Fe-rich melts and/or the accumulation of early crystallized Fe–Ti oxides during fractionation. [ABSTRACT FROM AUTHOR]

• First detailed temporal record of large igneous province mantle temperatures. • Mantle temperatures vary by 120 °C in the earliest 0.5 Ma of LIP magmatism. • A plume origin for the North Atlantic Igneous Province is supported. • Fluctuating mantle temperature impacts the dynamics of the crustal magmatic system. The generation of Large Igneous Provinces (LIPs) is a topic of vigorous debate with competing models variably invoking hot mantle plumes, insulative heating by supercontinents or edge driven convective instabilities. Mantle temperature and its temporal variation during LIP magmatism is key to distinguishing between these different models. This may have important consequences for the dynamics, evolution and tempo of volcano-magmatic systems developed during these periods of intense activity. Despite this, there are currently no detailed stratigraphically constrained studies of mantle temperature through a LIP succession. To address this, we have applied both olivine-spinel thermometry and modelling of primary magma compositions (Monte Carlo PRIMELT3) to constrain mantle potential temperature through a continuous sequence of LIP lavas formed during the earliest expression of the North Atlantic Igneous Province (the Antrim Lava Group). Mantle potential temperature derived from olivine-spinel and olivine addition methods give consistent temperature ranges of 1403–1521 °C and 1374–1472 °C, respectively. However, both temperature records indicate significant (100–120 °C) variation in melting temperature over a relatively short stratigraphic interval during petrogenesis of early magmas and much less variation in later magmas, suggesting initial instability or pulsing which stabilised with time. This supports a plume origin for LIP formation. Variability in melting temperature is mirrored by proxies for crustal and volcanic processes; olivine Ni contents are elevated (<3000 ppm) in the same stratigraphic interval as the lowest mantle temperatures, indicating mixing of primary and more evolved (MgO ∼4 %) melts, resulting from low magmatic flux into the crust during this time interval. The abundance and thickness of red weathering horizons capping lava flows is also significantly higher through the succession where mantle temperature variation is highest, indicating prolonged repose periods between eruption and a stop-start rhythm to volcanism. These unique observations indicate that volcanic, crustal and mantle systems are intrinsically linked and suggest that the tempo of volcanism, mediated via variations in melt flux, may ultimately be driven from below by changing mantle temperature. [ABSTRACT FROM AUTHOR]

Felsic rocks of the Piskahegan Group and coeval plutons form a major part of a Late Paleozoic epicontinental caldera in southwestern New Brunswick, Canada. The caldera forms an elliptical structure with a length of ∼34 km and a width of ∼13 km. It hosts a significant polymetallic deposit of tin, molybdenum, indium and bismuth associated with mid-sequence granitic intrusions. The caldera formed in the aftermath of the late Early to Middle Devonian Acadian Orogeny during the opening of the late Paleozoic Maritimes Basin in the Northern Appalachian Belt. Its surrounding successions are largely composed of bimodal igneous rocks that were derived from two distinct sources: upper mantle-derived mafic magma and lower crust-derived felsic magma. The rocks that marked the beginning of volcanic activity in the caldera are no younger than 374.2 ± 2 Ma, whereas the uppermost dated volcanic unit in the complex yielded an age of 364.6 ± 0.7 Ma. The latter is conformably overlain by a succession of red beds and undated basalts that also overlie penecontemporaneous felsic volcanic rocks adjacent to the caldera. The post-orogenic felsic rocks are fractionated, peraluminous A-2 type rocks with silica contents ranging from ∼70 to ∼79 wt% along with high K 2 O contents and ɛ Nd (t) ranging from −0.10 to +1.05. They were generated by the melting of lower crustal basement rocks linked to a lithospheric plate that was metasomatized during the Neoproterozoic. Based on available geochemical, geophysical and structural data on Late Paleozoic rocks of southeastern Canada, the melting may have been triggered by the injection of profuse mafic magma that eventually formed a thick underplating at the base of the crust in association with heat derived from an underlying mantle plume and conveyed by transtensional structures. Basal rocks of the Piskahegan Group (the Intracaldera Sequence) and penecontemporaneous volcanic rocks in Nova Scotia are interpreted as small erosional remnants of a Large Igneous Province (LIP) based on the extensive exposure of large coeval plutons throughout southeastern Canada. The new geochronological data suggests that profuse late Frasnian magmatism in this LIP could have contributed to the environmental deterioration that led to a significant extinction at the Frasnian-Famennian boundary (the Kellwasser Event). • The Mount Pleasant caldera complex is associated with a large Late Devonian igneous province in southeastern Canada. • Mafic underplating and profuse felsic magma produced as the Canadian Appalachian Belt was overriding a mantle plume. • Neodymium isotopes are compatible with a Ganderian crustal source. • New U-Pb zircon dates suggest that Frasnian volcanism was voluminous and may have contributed to the Kellwasser event. [ABSTRACT FROM AUTHOR]

Large igneous provinces (LIP) are vast (0.2 to >1 Mkm3) outpourings of basaltic lava and voluminous intrusions of magmas that have had important environmental consequences, in many cases leading to immense greenhouse gas release and mass extinctions. Magmatic oxygen fugacity (f O 2) influences the chemistry of volcanic gases and is an important parameter for examining the links between LIP eruptions and environmental change. To constrain the f O 2 of LIP magmas, we report olivine elemental chemistry of 399 crystals from a set of fifteen olivine-rich LIP samples, spanning in age from the Proterozoic (∼1270 Ma) to the Miocene (∼17 Ma). Concentrations of V in olivine are used to show that mafic LIP lavas erupted at +1.20 ± 0.95 ΔFMQ, on average more oxidized than mid ocean ridge basalts (MORB) at −0.28 ± 0.28 ΔFMQ. Mafic LIP magmas show a much larger range than MORB, however. Additionally, f O 2 shows a negative correlation with parental magma MgO content, with high MgO lavas approaching the MORB range. This correlation is likely due to sampling of a heterogeneous mixture of oxidized and reduced lithologies, as also sampled by ocean island basalts (OIB). Correlation between f O 2 and isotopic ratios such as 143Nd/144Nd demonstrates that the oxidized endmember is geochemically enriched, and may result from subduction recycling of oxidized surficial materials. The high f O 2 of primitive LIP magmas demonstrate that they largely emitted oxidized gases during eruption, and furthermore, that LIP magmas associated with mass extinctions have similar magmatic f O 2 to those that are not. Global plate tectonic position, magnitude and duration of LIP volcanic eruptions and magmatic degassing, as well as interaction with sedimentary basins in the crust - but not mantle source f O 2 - are likely to be the critical factors for whether a LIP was associated with a mass extinction. • The f O 2 of continental LIP lavas is constrained using the V-in-olivine method. • LIP lavas are more oxidized than MORB, overlapping with OIB. • LIP f O 2 data plot on same MgO-isotopic correlations of OIB. [ABSTRACT FROM AUTHOR]

• Eclogites protoliths in North Qinling UHPM are remnants of Neoproterozoic CFBs. • The 850–820 Ma eclogites protoliths and volcanics record a LIP over 300,000 km2. • The LIP reveals an 850 Ma-initiated mantle plume within Rodinia supercontinent. • The LIP was partly subducted to mantle depths in the Early Paleozoic. Large igneous provinces (LIP) provide invaluable clues for recognizing the growth, breakup, and cycles of supercontinents and constraining the activity of ancient mantle plumes (or superplumes). The widespread intraplate magmatism is considered as a possible fingerprint of ancient plume activities and LIPs. Here, we present the results of an integrated study on protoliths of eclogites and amphibolite-facies bimodal volcanic rocks from North Qinling Ultrahigh-pressure Metamorphic (UHPM) Terrane, Qinling Orogen, and identify a dismembered Neoproterozoic LIP. These rocks share similar protolith ages of ca. 850–800 Ma and experienced high- to ultrahigh-pressure metamorphism at ca. 500–480 Ma. The mafic rocks are mainly tholeiitic and display enrichment of LILEs and HFSEs, similar to the E-MORB/OIB characters. They also have typical features of continental flood basalts (CFBs) with low CaO/Al 2 O 3 (0.68–0.87), Lu/Yb (0.14–0.15), Zr/Nb (8–13), high Nb/La (0.87–1.24, mean 1.07), La/Nb (0.80–1.15), La/Ta (11–20), Nb/Yb (3.0–6.2) ratios, and positive ε Nd (t) (+4.3 to + 5.4). Their occurrence, geochemical features, age data, and high mantle potential temperature (1500–1550 °C) suggest that they are remnants of Neoproterozoic CFBs with mantle plume origin. Based on the lateral distribution length (ca. 300 km) of meta -basaltic rocks and the maximum subduction depths (ca. 100–200 km) recorded by UHP eclogites, the identified ca. 850 Ma-initiated CFBs in the North Qinling terrane should represent an LIP, covering more than 100,000 km2. This Neoproterozoic LIP, together with the coeval volcanic sequences in the South Qinling terrane and the northern Yangtze, would have occupied a maximum landmass of 300,000 km2, which lends support for the onset of a mantle plume at ca. 850 Ma within the Rodinia supercontinent. We conclude that the Qinling Block is one of the fragments of the Rodinia supercontinent with a passive margin covered by CFBs, which was subducted to mantle depths in the Early Paleozoic. [ABSTRACT FROM AUTHOR]

The Paraná-Etendeka Magmatic Province is the second largest continental large igneous province (LIP) known. It is characterised by the occurrence of an unusually high proportion (∼3%) of silica-rich magmatic products (dacitic to rhyolitic in composition). Here we provide the first experimental constraints on the pre-eruptive crystallisation conditions of the Caxias do Sul dacite (CSd), the oldest silicic end member of the Palmas-type volcanic sequence of the Paraná Magmatic Province. We use crystallisation experiments to define the phase assemblage of the CSd and compare our experimental results with observations from natural samples to constrain pre-eruptive conditions. We find that the crystallisation conditions are consistent with temperatures between 975 and 1000 °C, pressures of 150–350 MPa and a H 2 O content of ∼2 wt%. Quantitative textural analysis of natural products provides an estimated crystal content of 15–29 vol%, which likely crystallised within the storage region prior to magma ascent. The experimentally estimated high temperature and low H 2 O content suggest that low undercooling (Δ T) was maintained within the conduit, accompanied by the sole crystallisation of syn -eruptive microlites, generating minimal rheological change during magma ascent. Compared with other dacitic compositions, the CSd represents an atypical, high temperature and H 2 O-poor end member and possessed a comparatively low viscosity. • New constraints on the pre-eruptive conditions of the Caxias do Sul dacite. • P - T -H 2 O conditions constrained, combining experiments and data from natural samples. • The Caxias do Sul dacite was high temperature (975–1000 °C) and H 2 O-poor (∼2 wt%). • Low viscosity was likely maintained during magma ascent, influencing eruptive style. [ABSTRACT FROM AUTHOR]

Recognition of ancient pyroclastic rocks made up of particles of explosive volcanic origin and deposited by primary volcanic processes and/or rapid sedimentation of freshly erupted, texturally unmodified particles vis-a-vis secondary volcaniclastic deposits derived by significant reworking during transport of primary volcanic particles prior to deposition, but long after volcanism (epiclastic) remains a major challenge. A volcanic conglomerate having both rhyolitic clasts and matrix within the ~2.5 Ga Bijli Rhyolite in the Dongargarh large igneous province in the Bastar craton, is earlier interpreted to be of epiclastic origin, primarily because of the presence of large rounded rhyolite clasts imparting conglomeratic appearance to the deposit, and thereby considered representing a significant time break (unconformity) between explosive Bijli volcanism and the deposit. Based on new field and petrography studies, we identified the ~125 m thick volcanic conglomerate as rapidly sedimented texturally unmodified rhyolitic breccia-conglomerate linked to coeval incipiently welded pyroclastic flow that occurred during caldera collapse related to mafic-recharge-mediated Bijli volcanism, without significant time break. We ascribed the rounding of rhyolite clasts to surface tension of hot crystallising molten magma in plastic state and partly to mechanical interactions of particles on steep slopes in such volcanic settings. This study may help clarify origin of similar deposits in deformed metamorphosed provinces elsewhere. [ABSTRACT FROM AUTHOR]

The Late Paleozoic Ice Age (LPIA) was the longest-lasting icehouse in the Phanerozoic. Previous studies indicated a climate warming interval in the earliest Permian—an apex of the LPIA. To better understand hydroclimatic changes and carbon cycling within this time interval, we conducted a series of high-resolution geochemical and rock magnetic analyses, including magnetic measurements (e.g., magnetic susceptibility, anhysteretic remanent magnetization, hysteresis loops, temperature-dependent susceptibility), ratio of iron to potassium (Fe/K), and carbonate carbon isotope (δ13C carb) from a deep-marine section in South China. Calibrated to the published astronomical time scale, a negative δ13C carb excursion (−1‰) was identified during 298.4–297.9 Ma, and it was time-equivalent with the warming interval, recognized by a decrease in conodont apatite oxygen isotopes in South China, low-latitude sea-level transgression, and high-latitude deglaciation. The negative δ13C carb excursion also coincided with a magmatic pulse of the Skagerrak-Centered Large Igneous Province (LIP), indicating that the perturbation in carbon cycling is likely associated with the release of volcanic CO 2. Furthermore, cyclostratigraphic analysis on multiple paleoclimatic proxies, including ferrimagnetic susceptibility, gamma-ray, and Fe/K, suggested that the negative excursion of δ13C carb also overlapped with the maximum of the eccentricity cycle. It implied that orbital configurations may amplify the feedback of the LIP, causing this short-term warming interval. • High-resolution carbon isotope and magnetic record in the earliest Permian. • Transient climate warming interval is documented in the earliest Permian. • LIP and orbital forcing were critical drivers of the earliest Permian warming. [ABSTRACT FROM AUTHOR]

An 82.2 m-thick sequence of basaltic rocks was recovered from a deep-sea core on the eastern flank of the Naturaliste Plateau, offshore southwestern Australia during International Ocean Discovery Program (IODP) Expedition 369. The basaltic rocks were cored at the base of IODP Site U1513 and represent the acoustic basement of the Mentelle Basin. The recovered materials consist of subaerial to shallow-water basalt flows interbedded with volcaniclastic beds and cross-cutting dolerite dykes, all of which have been altered to some degree. Existing paleomagnetic data obtained from the overlying sedimentary sequences indicate that the basaltic sequence cored at Site U1513 was deposited before chron M10Nn.1n (which could be as young as 130.9 Ma or as old as 134.2 Ma, depending on the time scale used). Here, we present the results of 40Ar/39Ar step-heating experiments conducted on whole-rock samples of two basalt flows and six dolerite dykes to provide greater certainty of the timing of magmatism and subsequent alteration. Each sample was also characterised using optical and scanning electron microscopy together with X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses. The dolerite dykes are the only rocks that were sampled that record a remnant estimate of the primary cooling age of the magmatic event at ca 134 Ma. This magmatism was contemporaneous with rifting that preceded the break-up of Greater India from Australia/Antarctica and is potentially associated with the Greater Kerguelen large igneous province. The basalt flows record younger apparent ages (between 118 and 110 Ma) that cannot represent extrusive ages given their stratigraphic context, as well as older ages obtained from cross-cutting dykes. We interpret the younger apparent ages to reflect a phase of hydrothermal alteration that reset the argon isotopic system. A tectonic reconstruction, which shows the distribution of magmatism associated with the Greater Kerguelen large igneous province, indicates that the earliest phases of magmatism occurred within an ellipse with a NW–SE-oriented long axis. The reconstruction also shows that the Naturaliste Plateau was approximately 500 km from a known source of magmatism at ca 115 Ma. This distance is within the radius of a mantle plume head and indicates that hydrothermal and/or magmatic activity responsible for resetting the argon isotopic system of the dated basalt flows may have been associated with a mantle plume or was otherwise driven by a local source of magmatism that remained active during the Aptian (126.3–113.0 Ma). 40Ar/39Ar dating indicates Naturaliste Plateau magmatism occurred between 141.3 and 130.9 Ma. The basaltic rocks potentially record a phase of hydrothermal alteration at ca 118–110 Ma. Greater Kerguelen large igneous province magmatism occurred within an ellipse with a NW–SE oriented long axis. [ABSTRACT FROM AUTHOR]

The oxygen fugacity (f O 2) of the Earth's mantle is a key parameter that regulates fundamental geological processes such as planetary differentiation, mantle melting, and volatile cycling. Large igneous provinces (LIPs) are among the most voluminous mafic volcanic eruptions in the Earth's history. Constraining the f O 2 of LIP rocks is critical for understanding the redox state of the mantle and migration of volatiles from the deep Earth to the atmosphere. Here, we investigated primitive picrites from the Dali and Lijiang areas belonging to the Emeishan LIP, which contain early-crystallized olivine phenocrysts with Fo contents up to 93.5 and 91.9, respectively. The f O 2 conditions of primary and derivative melts are determined by the olivine-spinel and olivine-melt V oxybarometers, aided by temperature estimates from olivine-spinel Al and olivine-melt Sc/Y thermometers. The calculated f O 2 values are negatively correlated with olivine Fo contents due to fractionation of mafic minerals in a system closed to oxygen. The f O 2 s of Dali and Lijiang primary melts are −0.8 ± 0.4 and + 0.6 ± 0.3 (1σ) ΔFMQ log units, respectively, more variable than those of primitive MORBs, indicating significant f O 2 fluctuations in primary magmas from the Emeishan LIP caused by changes in both redox state of the source rock and depth of melt extraction. Melt barometer constrains the Dali and Lijiang primary melts generated at 4.7 and 3.0 GPa, respectively. After correcting for the depth effect, the Dali and Lijiang sources are more oxidized (with higher Fe3+/∑Fe ratios), in varying degrees, than the ambient upper mantle, likely due to incorporation of recycled surface materials. Under such oxidized conditions, mantle carbon is efficiently extracted during melting in the form of CO 2 and released to the atmosphere during massive magma emplacement, which may have played an important role in causing the climatic and environmental changes and triggering the end-Guadalupian mass extinction. [ABSTRACT FROM AUTHOR]

Stratigraphic, petrological and geophysical studies suggest that the Late Permian (~ 260 Ma) Emeishan Large Igneous Province in southern China may be formed by mantle plume activity. However, the plume impingement hypothesis remains controversial since interpretations based on volcano-stratigraphic analyses around plume induced domal uplift/inner zone suggest that the volcanism occurred under submarine environment rather than elevated sub-aerial (above sea level) conditions, usually associated with the dynamic topography effects of the ascending mantle plumes. Here, 2-D numerical and 3-D scaled laboratory (analogue) plume experiments are used to explore the coupled dynamics of plume-mantle-lithosphere interaction and their evolution of surface topography characteristics. Experimental results show that the initial (plume incubation) phase is characterized by rapid, transient domal uplift above the plume axis, subsequently, as plume head flattens, there is short wavelength topographic variation (ie. subsidence and uplift occurs synchronously) due to the shear stress imposed onto the base of the lithosphere and loss of gravitational potential energy. The surface depressions predicted by the plume models, next to the plume axial/inner/uplift zone, may explain the deposition of submarine volcanics at Lake Erhai, Dali in the western side and Xiluo and Daqiao in the eastern side, which may resolve the plume controversy for the formation of Emeishan Large Igneous Province. Notably, while experimental results from these two different techniques show some differences, (e.g much bigger plume head for the laboratory experiment), the overall characteristics of the predictions have robust similarities. For instance, the extension above the plume axis may explain the enigmatic cause of the Panxi rift system, in the middle of the inner zone where giant dyke swarms radiate from, and mafic magma underplatings in the lower crust has been described by seismological studies. [ABSTRACT FROM AUTHOR]

40Ar/39Ar geochronology is one of the most important techniques for constraining the timing of basaltic events due to the paucity of suitable minerals in basalts for other geochronological techniques such as U–Pb (e.g., zircon, baddeleyite). Among a variety of materials from basaltic rocks that have been used for 40Ar/39Ar dating, plagioclase is the most important due to its common presence in basalts as a primary crystallizing phase, and its transparency so that fresh grains can be selected during sample preparation. However, plagioclase 40Ar/39Ar geochronology has often been compromised by alteration (e.g., sericitization by hydrothermal events), which, in practice, is difficult to identify using a petrographic microscope when the amount of alteration is low (e.g., <1%). We used laboratory step-heating experiments and theoretical simulations to characterize the 40Ar/39Ar age and Ca/K spectra of altered plagioclase so that 40Ar/39Ar dating results on altered samples can be identified and better interpreted. The step-heating experiments and theoretical simulations yielded consistent results, and show that with the presence of even a tiny amount of sericite (~0.01% for K-poor samples and ~0.1% for K-rich samples), the plagioclase samples yielded alteration plateau ages that are 3%–4% younger than the crystallization age. The difference between the alteration age of sericitized plagioclase and its crystallization age is primarily controlled by the time lapse between the crystallization and sericitization events, but also by the Ca/K ratios of the plagioclase. For plagioclase samples that experienced the same alteration event, the higher the Ca/K ratio is, the more sensitive the 40Ar/39Ar age is to alteration. We propose that the alteration signatures of plagioclase can be effectively identified through inspecting the 40Ar/39Ar age spectra, the Ca/K spectra, and the degassing curves. We also investigated the effect of sericitization of plagioclase microliths in basaltic groundmass and modelled the 40Ar/39Ar age and Ca/K spectra of altered groundmass samples. We validate our approach by revisiting published 40Ar/39Ar dating results for large igneous provinces, and showed that these dates should have been interpreted as alteration ages (minimum eruption ages) rather than crystallization ages. Finally, we demonstrate that with high degrees of alteration (~50% for K-poor and >70% for K-rich plagioclase samples), the age of hydrothermal alteration can be successfully dated. [ABSTRACT FROM AUTHOR]

The Late Triassic Carnian Pluvial Episode (CPE) saw a dramatic increase in global humidity and temperature that has been linked to the large-scale volcanism of the Wrangellia large igneous province. The climatic changes coincide with a major biological turnover on land that included the ascent of the dinosaurs and the origin of modern conifers. However, linking the disparate cause and effects of the CPE has yet to be achieved because of the lack of a detailed terrestrial record of these events. Here, we present a multidisciplinary record of volcanism and environmental change from an expanded Carnian lake succession of the Jiyuan Basin, North China. New U–Pb zircon dating, high-resolution chemostratigraphy, and palynological and sedimentological data reveal that terrestrial conditions in the region were in remarkable lockstep with the large-scale volcanism. Using the sedimentary mercury record as a proxy for eruptions reveals four discrete episodes during the CPE interval (ca. 234.0 to 232.4 Ma). Each eruptive phase correlated with large, negative C isotope excursions and major climatic changes to more humid conditions (marked by increased importance of hygrophytic plants), lake expansion, and eutrophication. Our results show that large igneous province eruptions can occur in multiple, discrete pulses, rather than showing a simple acme-and-decline history, and demonstrate their powerful ability to alter the global C cycle, cause climate change, and drive macroevolution, at least in the Triassic. [ABSTRACT FROM AUTHOR]

We review the properties of the Neoarchean Ventersdorp Supergroup and provide new trace element concentrations and the first combined Sr-Nd-Hf isotopic compositions for the mafic magmatic products. These sequences contain the remnants of some of the world's oldest Large Igneous Provinces (total preserved volume = 0.659 × 106 km3). Ventersdorp rocks have been divided into three major units, separated by prominent unconformities: the basal Klipriviersberg Group (∼2.78 Ga), the medial Platberg Group (2.72 Ga) and the upper Pniel Sequence (2.68 Ga). The base of the Klipriviersberg Group is the Westonaria Formation, composed almost entirely of picrites (12–18 wt% MgO) and komatiites (>18 wt% MgO). All other formations of the Klipriviersberg Group contain mainly basaltic (<12 wt% MgO, 45–57 wt% SiO 2) and andesitic rocks (57–63 wt% SiO 2). The Platberg Group is composed of bimodal mafic lavas (Goedgenoeg and Rietgat Formations) and crustally derived dacites and rhyolites (Makwassie Formation); we did not study the crustally derived sequences. The Pniel Sequence contains basaltic lavas in the Allanridge Formation (<7.8 wt% MgO). Strontium isotopes have been modified by extensive low-grade hydrothermal alteration processes and cannot be used to make inferences about magmatic processes. Initial ε Nd and ε Hf values are highest for Westonaria picrites and komatiites (maximum ε Nd = +2.16; ε Hf = +3.60), and match Neoarchean depleted, asthenospheric mantle, implying derivation from large degree partial melting in a plume head. Klipriviersberg basaltic-komatiitic lavas have the largest volume (0.145 × 106 km3), qualifying this as a Large Igneous Province in its own right; Platberg and Allanridge basalts and basaltic andesites have unradiogenic ε Nd and ε Hf (ε Nd = −2.45 to −4.01; ε Hf = −2.73 to −10.12), and lower volumes (Platberg = 0.022 × 106 km3; Allanridge = 0.042 × 106 km3), too small to represent LIPs. Although Westonaria picrites and komatiites were likely sourced from the hot, central portions of a flattened plume head, the other magmatic Formations in the Ventersdorp Supergroup may have been derived from cooler, compositionally different, marginal parts of the plume head, or possibly the plume tail. The three Ventersdorp magmatic components can be interpreted in terms of a single, long-lasting plume, with the spatial overlap having been caused by a stationary African plate over a time interval of >100 million years. Trace element ratios and isotopic compositions suggest that fractional crystallization and crustal assimilation were minor to absent in Ventersdorp basaltic magmas. Negative Nb Ta anomalies are present in all magmatic rocks except those of the Westonaria Formation, suggesting that the lithospheric mantle component bears a subduction signature; this component probably represents deeply subducted oceanic lithosphere that was entrained in the deep mantle by an ascending plume. Volume and compositional relations preclude derivation of the basaltic lavas from subcontinental lithospheric mantle or small, enriched domains in the SCLM. Zn/Fe relations can be interpreted in terms of heterogeneous sub-lithospheric mantle sources, with Klipriviersberg Group lavas having been derived dominantly from peridotitic sources, whereas Platberg and Allanridge mafic lavas were derived from a source richer in pyroxenitic components. Our new Nd isotopic data coupled with lithostratigraphic differences indicate that correlations between the Ventersdorp (South Africa) and the coeval (2.77–2.71 Ga) Fortescue (Australia) sequences are more complex than is currently understood, possibly reflecting differences in basin structure and evolution. More data are needed to constrain the Vaalbara hypothesis, which postulates that the Kaapvaal and Pilbara Cratons were adjoined in the late Archean. • Ventersdorp Initial Nd and Hf isotopes are most depleted for basal komatiitic lavas. • Fractional crystallization and crustal assimilation were minor in these lavas. • Magmas were derived from a long-lived plume beneath a stationary African continent. • Sub-lithospheric mantle sources include both peridotite and pyroxenite. • Correlations between Ventersdorp and Fortescue (Australia) are possible, but complex. [ABSTRACT FROM AUTHOR]

The Beetaloo Sub‐basin, northern Australia, is considered the main depocentre of the 1,000‐km scale Mesoproterozoic Wilton package of the greater McArthur Basin – the host to one of the oldest hydrocarbon global resources. The ca. 1.40–1.31 Ga upper Roper Group and the latest Mesoproterozoic to early Neoproterozoic unnamed group of the Beetaloo Sub‐basin, together, record ca. 500 million years of depositional history within the North Australia Craton. Whole‐rock shale Sm–Nd and Pb isotope data from these sediments reveal sedimentary provenance and their evolution from ca. 1.35 to 0.85 Ga. Furthermore, these data, together with shale major/trace elements data from this study and pyrolysis data from previous publications, are used to develop a dynamic tectonic geography model that links the organic carbon production and burial to an enhanced weathering of nutrients from a large igneous province. The ca. 1.35–1.31 Ga Kyalla Formation of the upper Roper Group is composed of isotopically evolved sedimentary detritus that passes up, into more isotopically juvenile Pb values towards the top of the formation. The increase in juvenile compositions coincides with elevated total organic carbon (TOC) contents of these sediments. The coherently enriched juvenile compositions and TOC the upper portions of the Kyalla Formation are interpreted to reflect an increase in nutrient supply associated with the weathering of basaltic sources (e.g. phosphorous). Possible, relatively juvenile, basaltic sources include the Wankanki Supersuite in the western Musgraves and the Derim Derim–Galiwinku large igneous province (LIP). The transition into juvenile, basaltic sources directly before a supersequence‐bounding unconformity is here interpreted to reflect uplift and erosion of the Derim Derim–Galiwinku LIP, rather than an influx of southern Musgrave sources. A new baddeleyite crystallisation age of 1,312.9 ± 0.7 Ma provides both a tight constraint on the age of this LIP, along with its associated magmatic uplift, as well as providing a minimum age constraint for Roper Group deposition. The unconformably overlying lower and upper Jamison sandstones are at least 300 million years younger than the Kyalla Formation and were sourced from the Musgrave Province. An up‐section increase in isotopically juvenile compositions seen in these rocks is interpreted to document the progressive exhumation of the western Musgrave Province. The overlying Hayfield mudstone received detritus from both the Musgrave and Arunta regions, and its isotopic geochemistry reveals affinities with other early Neoproterozoic basins (e.g. Amadeus, Victoria and Officer basins), indicating the potential for inter‐basin correlations. [ABSTRACT FROM AUTHOR]

Antarctica and Zealandia were once-adjacent blocks of Gondwana with a shared magmatic history during the Mesozoic and earlier. This is preserved in (a) shared Palaeozoic and Mesozoic Gondwana plutonism; (b) magmatism associated with syn-Gondwana breakup, including Jurassic-aged dolerite rocks of the Ferrar large igneous province, and igneous intrusions of similar isotopic affinity occurring on both continents coeval with Late Cretaceous rifting of Antarctica from Zealandia. The shared magmatic history continued post-Gondwana breakup through (c) the generation of oceanic crust and (d) eruption of diffuse alkaline magmatic province (DAMP) rocks. The DAMP encompasses magmatism from the Late Cretaceous to present day that shares isotopic and trace element characteristics over a (now) widely dispersed area of the southwest Pacific. This has been ascribed to either a previously contiguous mantle lithosphere with a shared, syn-Gondwana breakup history contributing to volcanic melts or to an isotopically distinct Antarctica – Zealandia asthenospheric mantle domain. The development of the Antarctic ice sheet after 34 Ma resulted in many volcanoes recording ice interactions that reveal many new details of Antarctica's palaeoenvironmental history. Study of the volcanic history of Antarctica helps to advance understanding of the geological history of the region, including once-conjugate continents like Zealandia. [ABSTRACT FROM AUTHOR]

Oceanic Anoxic Event 2 (OAE-2) occurred at the Cenomanian-Turonian boundary (∼94.1 Ma) and was a time of profound global changes in ocean chemistry and the carbon cycle. This event was characterized by a positive carbon isotope excursion (CIE) caused by massive organic carbon burial, global greenhouse temperatures, ocean deoxygenation, and changes in ocean life driven by large igneous province (LIP) activity. LIPs throughout the Phanerozoic have had dynamic magma flux, with episodes of major eruptions interspersed with periods of relatively less intense eruptions. A possible trigger for LIP activity throughout the Phanerozoic has been attributed to extraterrestrial impacts because there are multiple contemporaneous occurrences of large craters, LIP activity, and mass extinctions in the geologic record. At the Cenomanian-Turonian boundary, there is a 25 km diameter (rim-to-rim) complex crater in NW Alberta, Canada known as the Steen River impact structure dated at 91 ± 7 Ma (Carrigy and Short, 1968). An alternative explanation for those craters found contemporaneous with LIP activity and mass extinctions is that they were created by large explosive events related to LIP activity. Explosive events associated with mantle plume incubation beneath cratonic lithosphere have been suggested to create geologic features commonly attributed to impacts (e.g., shocked quartz, microspherules, etc.). Currently, the trigger for LIP activity during OAE-2, as well as the duration of LIP activity and the temporal variation and magnitude of eruption rates are not well constrained. To address the issue of LIP eruption rates and the trigger for LIP activity, we examined osmium (Os) abundances and isotopes as well as highly siderophile element (HSE; for this study: Re, Ru, Pd, Os, Ir, Pt) abundance data from a continuous sedimentary section spanning OAE-2. The section is from the Eagle Ford Group in the Iona-1 core, deposited in the Cretaceous Western Interior Seaway (KWIS). We found three high Os concentration intervals with mantle-like initial Os i isotope (initial 187Os/188Os) values of ∼0.16. These intervals are interpreted to reflect high-flux LIP magmatic pulses. Between the pulses, lower Os abundances with more radiogenic Os i values of ∼0.20 are observed, which we interpret as low-flux LIP activity between the high-flux periods. This trend of high-and-low flux Os concentration pulses with mantle-like Os i values during the high flux periods is found in another KWIS core (USGS Portland #1) deposited to the north of Iona-1, and in core Deep Sea Drilling Project (DSDP) Site 530 Hole A (hereafter DSDP 530A; drilled off-shore Namibia in the Angola Basin) deposited in the Southern Hemisphere. Before and throughout the Iona-1 core OAE-2 interval, HSE abundance patterns indicate a mantle source for the unradiogenic Os, and are not consistent with an extraterrestrial impact trigger or contribution to LIP activity during OAE-2. This evidence for multiple high-flux pulses of LIP activity driving ocean deoxygenation has implications for the modern ocean, which is currently experiencing deoxygenation. These results provide new constraints on subsequent high-flux periods that extended the event. The first high-flux period started ∼60 Kyr after our selection of the onset of the CIE. The second and third high-flux periods started ∼270 and ∼400 Kyr after the onset of the CIE, respectively. After the third high-flux period, δ13C org and Os isotope ratios shifted back to pre-excursion values over ∼585 kyr. In the Iona-1 core, OAE-2 lasted for 1.04 ± 0.12 Myr based on our selection of the CIE. [ABSTRACT FROM AUTHOR]

A deeper understanding of hyperthermal events in the Earth's history can provide an important scientific basis for understanding and coping with global warming in the Anthropocene. Two types of hyperthermal events are classified based on the characteristics of the carbon isotope excursion (CIE) of the five representative hyperthermal events in the Mesozoic and Cenozoic. The first type is overall characterized by negative CIEs (NCHE) and represented by the Permian-Triassic boundary event (PTB, ~252 Ma), the early Toarcian oceanic anoxic event (TOAE, ~183 Ma), and the Paleocene-Eocene Thermal Maximum event (PETM, ~56 Ma). The second type is overall characterized by positive CIEs (PCHE) and represented by the early Aptian oceanic anoxic event (OAE1a, ~120 Ma) and the latest Cenomanian oceanic anoxic event (OAE2, ~94 Ma). Hyperthermal events of negative CIEs (NCHE), lead to dramatic changes in temperature, sedimentation, and biodiversity. These events caused frequent occurrence of terrestrial wildfires, extreme droughts, acid rain, destruction of ozone layer, metal poisoning (such as mercury), changes in terrestrial water system, and carbonate platform demise, ocean acidification, ocean anoxia in marine settings, and various degree extinction of terrestrial and marine life, especially in shallow marine. In contrast, hyperthermal events of positive CIEs (PCHE), result in rapid warming of seawater and widespread oceanic anoxia, large-scale burial of organic matter and associated black shale deposition, which exerted more significant impacts on deep-water marine life, but little impacts on shallow sea and terrestrial life. While PCHEs were triggered by volcanism associated with LIPs in deep-sea environment, the released heat and nutrient were buffered by seawater due to their eruption in the deep sea, thus exerted more significant impacts on deep-marine biota than on shallow marine and terrestrial biota. This work enriches the study of hyperthermal events in geological history, not only for the understanding of hyperthermal events themselves, large igneous provinces, marine and terrestrial environment changes, mass extinctions, but also for providing a new method to identify the types of hyperthermal events and the inference of their driving mechanism based on the characteristics of carbon isotopic excursions and geological records. [ABSTRACT FROM AUTHOR]

Bubble emission mechanisms from submerged large igneous provinces remains enigmatic. The Kerguelen Plateau, a large igneous province in the southern Indian Ocean, has a long sustained history of active volcanism and glacial/interglacial cycles of sedimentation, both of which may cause seafloor bubble production. We present the results of hydroacoustic flare observations around the underexplored volcanically active Heard Island and McDonald Islands on the Central Kerguelen Plateau. Flares were observed with a split‐beam echosounder and characterized using multifrequency decibel differencing. Deep‐tow camera footage, water properties, water column δ3He, subbottom profile, and sediment δ13C and δ34S data were analyzed to consider flare mechanisms. Excess δ3He near McDonald Islands seeps, indicating mantle‐derived input, suggests proximal hydrothermal activity; McDonald Islands flares may thus indicate CO2, methane, and other minor gas bubbles associated with shallow diffuse hydrothermal venting. The Heard Island seep environment, with subbottom acoustic blanking in thick sediment, muted 3He signal, and δ13C and δ34S fractionation factors, suggest that Heard Island seeps may either be methane gas (possibly both shallow biogenic methane and deeper‐sourced thermogenic methane related to geothermal heat from onshore volcanism) or a combination of methane and CO2, such as seen in sediment‐hosted geothermal systems. These data provide the first evidence of submarine gas escape on the Central Kerguelen Plateau and expand our understanding of seafloor processes and carbon cycling in the data‐poor southern Indian Ocean. Extensive sedimentation of the Kerguelen Plateau and additional zones of submarine volcanic activity mean additional seeps or vents may lie outside the small survey area proximal to the islands. Plain Language Summary: Bubbles are constantly escaping the seafloor, either from thick sediments with gas‐producing bacteria or from volcanic gases escaping rocks deep beneath the seafloor. We use sonar to observe bubbles that appear as "hydroacoustic flares" as they travel from the seafloor into the ocean. Our paper shows the results of the 2016 RV Investigator voyage to Heard and McDonald Islands, two of Australia's most remote islands and home to its only active volcanoes. We observed hundreds of flares around the two islands and were able to examine bubbles in some of our camera footage. By examining the seafloor, the shallow subseafloor, and the chemistry of sediments and the water column, we suggest the bubbles may be composed of different gases. Around Heard Island, bubbles were associated with thick sediment that are likely rich with bacteria that produce methane gas; near the McDonald Islands, bubbles were not associated with sediments and possibly indicate shallow volcanic activity emitting gases, like CO2, originating from the mantle. Knowing where bubbles are escaping is crucial for understanding how much gas is contributed from the seafloor into the ocean and atmosphere. Key Points: Active submarine gas emission around Heard and McDonald Islands on the Central Kerguelen Plateau in the southern Indian OceanGas release near the McDonald Islands possibly shallow diffuse hydrothermal venting, uncommon on an intraplate large igneous provinceGas release near Heard Island either or both a biogenic orthermogenic methane seep, the second reported in the Southern Ocean to date [ABSTRACT FROM AUTHOR]

With a size of over 500,000 km2, the Deccan Volcanic Province (DVP) covers a large area of the Indian subcontinent. Stratigraphically continuous lava flows piled up to 3000 m record about five million years of volcanic activity. The peak activity of one million years coincides with the migration of the Indian subcontinent across the Réunion plume. Previous studies inferred an isotopic "common signature" for most DVP basalts that is best explained by a mixture of early Réunion plume-related melts and melts from the depleted upper mantle. Further chemical variability of the DVP sequence was explained by the incorporation of material from the lithospheric mantle and continental crust possibly within a single magma chamber system. Yet, indications for a complex crustal magmatic system have also been brought forward by earlier studies and find recently more support in explaining the magmatic plumbing system of the DVP and Large Igneous Provinces in general. This study presents new major and trace element data, including high-precision concentration measurements of high-field strength elements by isotope dilution and Sr-Nd-Hf-Pb isotope compositions for basaltic samples that cover nearly the complete DVP main section. Based on significant variations in Nb/Th (and Th/Ta) over a wide range of MgO concentrations we identified three distinct magma differentiation trends. The distinct differentiation trends result from three types of parental melts that are best explained by different proportions of lower and upper mantle melts indicated by diluted Réunion plume-like trace element and isotope compositions. During their ascent, these separate melts assimilated variable amounts of metasomatized lithospheric mantle and crustal material. Most likely the assimilation occurred before any major differentiation events, thus fixing the Nb/Th (and Th/Ta) of each group regardless of the degree of differentiation. The chemical trends can also be replicated using a statistical numerical approach, confirming that their geochemical signature truly reflects individual differentiation of three distinct parental melts. Field relations require that lavas related to these three unique differentiation trends erupted contemporaneously. This is in contrast to the idea of a gradually evolving single magma chamber system and the concept of a general chemostratigraphy for the DVP main plateau. Rather, our study reveals fast-changing contributions of different mantle reservoirs and provides new insight into the magma-plumbing systems of Large Igneous Provinces that may be more complex. [Display omitted] • Evidence for a multi-magma chamber system beneath the Deccan Volcanic Province. • Three distinct magma differentiation trends are observed. • Variable proportions of upper and lower mantle melts. • Crust and metasomatized lithosphere were assimilated during magma ascent. • The DVP chemostratigraphy might need revision. [ABSTRACT FROM AUTHOR]

The paper presents a detailed review of chemostratigraphic data on the Bonarelli oceanic anoxic event (OAE2) at the Cenomanian-Turonian boundary from different regions worldwide, with a focus on the respective redox conditions in the basins, metal anomalies, and δ13C excursions. Marine sediments with OAE2 signatures in Eastern Kamchatka are compared with their counterparts from submarine volcanic rises in the northwestern Pacific. The available isotope ages of lavas from some large igneous provinces are correlated with the age of OAE2. The Bonarelli event was triggered and governed by several interrelated factors: volcanism, climate, and ocean circulation. The supply of nutrients into oceans as a result of enhanced magmatism, hydrothermal activity, and weathering on continents played an important role in maintaining anoxia. The spatial patterns of black-shale deposition were controlled by ocean circulation. Geochemical and biochemical processes associated with high productivity ultimately led to its reduction and to the recovery of oxic conditions in oceans. [ABSTRACT FROM AUTHOR]

Oceanic environments and biotas were in a state of near-continuous perturbation during the Early Triassic, the ~5-million-year interval following the latest Permian mass extinction (LPME), but the underlying cause(s) remain uncertain. The role of episodic volcanic or intrusive magmatic activity in triggering global-scale perturbations during this interval is suspected but has not been strongly evidenced to date. Here, we investigate the record of volcanism through the Early Triassic (with a focus on the Smithian-Spathian Boundary, or SSB) using mercury (Hg) concentrations in marine sediments as a proxy. This study examines five marine sections from three paleo-oceans (Paleo-Tethys, Neo-Tethys, and Panthalassa) representing a range of depositional settings from shallow platform to deep slope. Our results suggest that volcanic and magmatic activity of the Siberian Traps Large Igneous Province (STLIP) was most intense during the first ~1.3 million years following the LPME, and that termination of its most active stage was responsible for a sharp cooling event at the SSB. Variations in the intensity of STLIP activity are thus likely to account for the large (>8‰) fluctuations of δ13C carb and related changes in oceanic redox and environmental conditions that characterized the Griesbachian to Smithian substages of the Early Triassic in marine sections globally. We hypothesize that a strong reduction or cessation of STLIP activity at the SSB set the stage for the recovery of marine biodiversity and ecosystems in the Spathian and later. • First Hg concentration records spanning the full Early Triassic from five sections with a global distribution (581 analyses). • Hg data provide a proxy record of the timing and intensity of Siberian Traps volcanic activity during the Early Triassic. • Peak Hg inputs occurred around the Permian-Triassic boundary, when Hg/TOC rose to ~3–8× Late Permian background values. • High Hg inputs during the Griesbachian-Smithian, with a secondary peak coinciding with the Late Smithian Thermal Maximum. • Hg inputs were modest during the Spathian and returned to background levels at the Early/Middle Triassic boundary. [ABSTRACT FROM AUTHOR]

Correlations within and between Precambrian basins are heavily reliant on precise dating of volcanic units (i.e., tuff beds and lava flows) in the absence of biostratigraphy. However, felsic tuffs and lavas are rare or absent in many basins, and direct age determinations of Precambrian basaltic lavas have proven to be challenging. In this paper, we report the first successful application of 40Ar/39Ar dating to pyroxene from a Neoproterozoic basalt unit, the Keene Basalt in the Officer Basin of central Australia. 40Ar/39Ar analyses of igneous pyroxene crystals yielded an age of 752 ± 4 Ma (mean squared weighted deviation = 0.69, p = 72%), which is underpinned by 40Ar/39Ar plagioclase age (753.04 ± 0.84 Ma) from the basalt. This age is significant because the Keene Basalt is one of the very few extrusive igneous rocks identified within the Neoproterozoic successions of central Australia and is potentially an important time marker for correlating the Neoproterozoic stratigraphy within, and beyond, the central Australian basins. Our geochronological and geochemical data show that the Keene Basalt, which is characterized by enriched elemental and Nd‐Pb isotopic signatures, is strikingly similar to, and coeval with, the 755 ± 3 Ma Mundine Well Dolerite in northwestern Australia. Here we suggest that both are part of the same large igneous province (~6.5 × 105 km2) related to breakup of the supercontinent Rodinia. This study demonstrates the potential of pyroxene 40Ar/39Ar geochronology to date ancient flood basalts and to provide pivotal time constraints for stratigraphic correlations of Precambrian basins. Plain Language Summary: Ancient basaltic lavas erupted on Earth's crust hold critical clues about the tectonic and igneous history of geologic past and are important for correlating Precambrian stratigraphy and reconstructing supercontinents. However, constraining the crystallization age of basaltic lavas proves challenging due to the dearth of commonly used uranium‐lead geochronometers such as zircon in such rocks. In this research, we applied 40Ar/39Ar dating of pyroxene and plagioclase to establish the eruption age of a critical basalt lava suite, the Keene Basalt, in the Neoproterozoic Officer Basin in central Australia. The new age, combined with geochemical constraints, contributes to conclusively defining the genetic affinity and geodynamic setting of the basalt unit. Application of pyroxene 40Ar/39Ar dating to terrestrial basalts represents an important technical breakthrough, and we report the first successful result for a Precambrian basalt. The robustly dated Keene Basalt is an important time marker for correlating the Neoproterozoic successions and associated glacial deposits in Australia and worldwide. The new age and geochemistry of the basalt are used to test its relationship to known Neoproterozoic igneous events. Our data, integrated with existing evidence, reveals a 755‐ to 750‐Ma large igneous province related to Rodinia breakup. Key Points: We report the first application of pyroxene 40Ar/39Ar dating to a Precambrian basaltic lava, the Keene Basalt in central AustraliaThe Keene Basalt is correlated with the Mundine Well Dolerite, both being part of a 755‐ to 750‐Ma LIPThe robustly dated Keene Basalt is an important time marker for correlating Neoproterozoic successions in Australia and worldwide [ABSTRACT FROM AUTHOR]

Mantle melting dynamics of the Central Atlantic Magmatic Province (CAMP) is constrained from new platinum group element (PGE), gold (Au), rare earth element (REE), and high field strength element (HFSE) data and geochemical modelling of flood basalts in Morocco. The PGE are enriched similarly to flood basalts of other large igneous provinces. The magmas did not experience sulphide saturation during fractionation and were therefore fertile. The CAMP is thus prospective for PGE and gold mineralization. The Pt/Pd ratio of the Moroccan lavas indicates that they originated by partial melting of the asthenospheric mantle, not the subcontinental lithospheric mantle. Mantle melting modelling of PGE, REE and HFSE suggests the following: (1) the mantle source for all the lavas was dominated by primitive mantle and invariably included a small proportion of recycled continental crust (<8%); (2) the mantle potential temperature was moderately elevated (c. 1430°C) relative to ambient mantle; (3) intra-lava unit compositional variations are probably a combined result of variable amounts of crust in the mantle source (heterogeneous source) and fractional crystallization; (4) mantle melting initially took place at depths between c. 110 and c. 55 km and became shallower with time (c. 110 to c. 32 km depth); (5) the melting region appears to have changed from triangular to columnar with time. These results are best explained by melting of asthenospheric mantle that was mixed with continental sediments during the assembly of Pangaea, then heated and further mixed by convection while insulated under the Pangaea supercontinent, and subsequently melted in multiple continental rift systems associated with the breakup of Pangaea. Most probably the CAMP volcanism was triggered by the arrival of a mantle plume, although plume material apparently was not contributing directly (chemically) to the magmas in Morocco, nor to many other areas of CAMP. [ABSTRACT FROM AUTHOR]

• Additional units of the 920–900 Ma Bahia-Gangila LIP (Brazil-Africa) are identified. • Santa Maria de Itabira gabbro U-Pb ages are 940 ± 42 Ma, 912 ± 17 Ma, and 986 ± 64 Ma. • 920–900 Ma LIPs of North China and São Francisco/Congo cratons have similar geochemistry. A widespread mafic sill and dyke unit (the Pedro Lessa suite) adjacent to the southeastern São Francisco (SF) craton (eastern South America) is dated as 940 ± 42 Ma, 912 ± 17 Ma, and 986 ± 64 Ma (based on combined ID-TIMS and LA-ICPMS analyses on baddeleyite grains) on the Santa Maria de Itabira gabbroic intrusion. These ages suggest membership in the previously defined ca. 920–900 Ma Large Igneous Province (LIP) (herein referred to as the Bahia-Gangila LIP) of the reconstructed São Francisco and formerly adjacent Congo craton (Africa). Additional mafic and felsic units throughout the SF craton are also linked (based on a literature review), thus expanding the size of the reconstructed LIP to ca. 1,500,000 km2. Geochemistry reveals high Ti OIB signature for most units and low Ti E-MORB composition for the Gangila flood basalts, marking the initiation of attempted ocean opening. Geochemistry of the Bahia-Gangila LIP is also compared with the ca. 920–900 Ma Dashigou-Chulan LIP of the North China craton, and implications for three possible reconstructions of SF/Congo craton with the North China craton are considered. [ABSTRACT FROM AUTHOR]

• New 1888 Ma mafic dyke swarm in southwest Yilgarn Craton, Western Australia has been discovered. • The new dyke suite suggests connection with India at ca. 1890 Ma and may be part of the Bastar-Cuddapah Large Igneous Province. • The dyke swarm is coeval with global mafic magmatism found on most other Precambrian cratons. The Archean Yilgarn Craton in Western Australia is intruded by numerous mafic dykes of varying orientations, which are poorly exposed but discernible in aeromagnetic maps. Previous studies have identified two craton-wide dyke swarms, the 2408 Ma Widgiemooltha and the 1210 Ma Marnda Moorn Large Igneous Provinces (LIP), as well as limited occurrences of the 1075 Ma Warakurna LIP in the northern part of the craton. We report here a newly identified NW-trending mafic dyke swarm in southwestern Yilgarn Craton dated at 1888 ± 9 Ma with ID-TIMS U-Pb method on baddeleyite from a single dyke and at 1858 ± 54 Ma, 1881 ± 37 and 1911 ± 42 Ma with in situ SHRIMP U-Pb on baddeleyite from three dykes. Preliminary interpretation of aeromagnetic data indicates that the dykes form a linear swarm several hundred kilometers long, truncated by the Darling Fault in the west. This newly named Boonadgin dyke swarm is synchronous with post-orogenic extension and deposition of granular iron formations in the Earaheedy basin in the Capricorn Orogen and its emplacement may be associated with far field stresses. Emplacement of the dykes may also be related to initial stages of rifting and formation of the intracratonic Barren Basin in the Albany-Fraser Orogen, where the regional extensional setting prevailed for the following 300 million years. Recent studies and new paleomagnetic evidence raise the possibility that the dykes could be part of the coeval 1890 Ma Bastar-Cuddapah LIP in India. Globally, the Boonadgin dyke swarm is synchronous with a major orogenic episode and records of intracratonic mafic magmatism on many other Precambrian cratons. [ABSTRACT FROM AUTHOR]

• Geochronology of LIP-scale events through time and space in the Amazonian Craton. • 1.89–1.87 Ga Uatumã SLIP links well the known LIP events on other crustal blocks. • 1.11 Ga LIP has remarkable match with intraplate activity in other places around the world. • 0.53 Ga dykes mark reactivation of the cratonic margin during West Gondwana assembly. • Ca. 200 Ma dykes correlate with the span of ages for CAMP LIP event. U-Pb baddeleyite ages for key mafic dykes of the Amazonian Craton reveal four significant intraplate episodes that allow connections with global igneous activity through time and supercontinent cycles. The oldest dykes (Carajás-Rio Maria region) are diabases with ages of 1880.2 ± 1.5 Ma and 1884.6 ± 1.6 Ma, respectively, corresponding with the Tucumã swarm which crops out to the west and is age-equivalent. The magmatic activity has a genetic link with the ca. 1.88 Ga Uatumã Silicic Large Igneous Province (SLIP), characterized by felsic plutonic-volcanic rocks. There is an age correlation with LIP events (ca. 1880 Ma) in the Superior, Slave, Indian and other cratons. This magmatism could be derived from significant perturbations of the upper mantle during the partial assembly of Columbia. Gabbronorite of the Rio Perdido Suite (Rio Apa Terrane) crystallized at 1110.7 ± 1.4 Ma, and is identical to that of the Rincón del Tigre-Huanchaca LIP event of the Amazonian Craton. This event was synchronous with the initiation of Keweenawan magmatism of central Laurentia (Midcontinent Rift) and also with coeval units in the Kalahari, Congo and India cratons. The two youngest U-Pb dates (535 and 200 Ma) occur in the Carajás region. Diabase of the Paraupebas swarm yields an age of 535.1 ± 1.1 Ma, which may be correlative with the giant Piranhas swarm located ca. 900 km apart to the west. The Paraupebas swarm is correlative with post-collisional plutonism within the Araguaia marginal belt. Therefore, the Cambrian dykes may reflect reactivation of cooled lithosphere, due to crustal extension/transtension active along the craton's margin during assembly of West Gondwana. This magmatism is also contemporaneous with the 539–530 Ma Wichita LIP of southern Laurentia. The youngest studied Carajás region dyke was emplaced at ca. 200 Ma, corresponding with 40Ar/39Ar ages for the Periquito dykes west of Carajás and with most K-Ar ages of the giant Cassiporé swarm, located north of the study area. The newly dated ca. 200 Ma dyke fits well into the known, brief span of ages for the CAMP Large Igneous Province event, around the present central and northern Atlantic Ocean. [ABSTRACT FROM AUTHOR]

The initial formation and temporal evolution of large igneous plateaus and the extent to which these large enigmatic igneous features impact on their immediate and distant ecological surrounding remains a matter of active research. The compositional variability in large igneous provinces has mainly been attributed to changes in the melting regime and shallow crustal processes and commonly ranges from depleted tholeiitic basaltic to enriched alkaline lavas. Large igneous provinces erupted in the submarine environment however, may also experience intense hydrothermal alteration during their formation resulting from an increased exchange between seawater and the erupting lavas during their eruptive history. The submarine Azores Plateau in the Central Northern Atlantic has generally been treated to represent such large igneous province formed since ∼10 Ma by widespread volcanism and the unique tectonic regime which results in large fault systems exposing the erupted lavas. Here, we present new seismic, petrological and major element, trace element and isotope geochemical data from a ∼1000 m stratigraphic section of submarine lavas exposed at the western Princessa Alice bank. The 22 samples recovered from the near-vertical rift wall provide evidence for intense water-rock exchange not observed anywhere in oceanic crust sampled to date. Fluid-immobile incompatible trace elements show that the samples formed from higher degrees of partial melting of a mantle source that is less enriched than the source that gives rise to the islands today. The extents of melting today are very small, implying a change in melting regime since initial formation of the Princessa Alice Plateau basalts that correspond to a melting anomaly in the Azores. Our observations indicate that the extreme levels of alteration may result from a combination of intensified magmatic activity during initial formation of the Azores Plateau and the tectonic regime providing pathways for the fluids. Our results impact on the interpretation of shallow level crustal magmatic processes, in which the contribution of crustal sources to the ascending melt may be different to what had previously been suggested. We propose that hydrothermal alteration during submarine igneous plateau forming events can drastically change the compositions of the igneous crust. The associated elemental and isotopic exchange between the oceanic crust and hydrosphere may substantially change the chemical fluxes between oceans and crust during the emplacement of oceanic plateaus. [ABSTRACT FROM AUTHOR]

Highlights • New 40Ar/39Ar age of 135.9 ± 1.2 Ma and Sr–Nd–Pb isotopes for previously undated flow of Bunbury Basalt. • >80% of Cretaceous WA magmatism synchronous with breakup of eastern Gondwana at 137–136 Ma. • Kerguelen mantle plume under Greater India at 137–136 Ma cannot be origin for Bunbury Basalt. • Breakup of eastern Gondwana not caused by a thermochemical plume. • Volatile enrichment during ca. 550–500 Ma Kuunga Orogeny instead facilitated breakup. Abstract The link between mantle plumes and continental breakup remain a topic of debate. Here, a new 40Ar/39Ar age of 135.9 ± 1.2 Ma (2 σ) and previous ages from the Bunbury Basalt – lava flows that are part of the Greater Kerguelen large igneous province (LIP) – reveal that >80% of magmatism in the southern Perth Basin was concomitant with the continental breakup of eastern Gondwana at ca. 137–136 Ma. New and existing isotope geochemical data show that only lithospheric and depleted asthenospheric sources were melted to form the Bunbury Basalt and most other early, ca. 147–124 Ma magmatic products part of the Greater Kerguelen LIP. All lines of evidence strongly point towards passive continental breakup of eastern Gondwana, including the restriction of 147–124 Ma magmatism to continental rifts, the lack of excess oceanic magmatism in this period and the >1000 km distance between the Kerguelen plume underneath Greater Indian lithosphere and the breakup nexus. It is not possible to reconcile the influence of a thermochemical plume with the observed geochemical, spatial and geochronological information. Instead, we posit that eastern Gondwana breakup occurred because it was proximal to the former suture zone associated with the ca. 550–500 Ma Kuunga Orogeny between Indo–Australia and Australo–Antarctica. Enrichment of the mantle with volatiles associated with subduction during the Kuunga Orogeny permitted partial melting when the continental crust was sufficiently attenuated in the Early Cretaceous. Repeated and protracted rifting of Greater India from Australo–Antarctic since the mid-Paleozoic eventually led to the rupture of the continental lithosphere and to mafic magmatism at ca. 137–136 Ma, approximately along the position of the former suture zone, without the influence of a mantle plume. [ABSTRACT FROM AUTHOR]

New petrographic, geochemical, and Sm-Nd isotopic data provide constraints on the petrogenesis of ca. 2400 Ma gabbronorite, picrodolerite and dolerite mafic sills and dikes in the Liinakhamari and Sorvaranger areas, Kola–Norwegian terrane, Northern Fennoscandia. The sills are differentiated. Their chilled margins are composed of porphyritic picrodolerite with olivine (Fo92-81) and clinopyroxene (Mg# = 85–80) phenocrysts enclosed by quenched groundmass with intergrows of fan-shaped branched plagioclase grains and clinopyroxenes. The bottom of the sills are usually composed of cumulative olivine gabbronorite upsection followed by olivine gabbro, gabbro, and quartz-bearing dolerites. Picrodolerite and dolerite dikes are close to chilled margins and evolved quartz-bearing dolerites from the upper parts of picrodolerite sills, correspondingly, in terms of mineral and chemical composition. The distribution of trace elements in sills sections is caused by fractionation crystallization of picrodolerite magma with a leading role of gravity settling of olivine phenocrysts. Variations of neodymium isotopic composition in the cumulative gabbronorites in the lower (εNd from –0.25 to +0.82) and dolerites in the upper (εNd from –0.85 to –2.4) parts of the sills are probably related with an addition of crustal contaminant into the magma after phenocrysts crystallization. Doleritic dikes have more radiogenic neodymium isotopic composition (εNd = –0.10) in comparison with dolerites of sills that suggests lower degrees of crustal contamination in dikes. Evaluation of conditions of phenocrysts crystallization using mineral thermobarometers and modelling of crystallization using alphaMELTS indicate that the main stage of the evolution of ca. 2400 Ma mafic melts was probably related with high degrees of fractional crystallization and crustal contamination of high-Mg (MgO ~ 18 wt %) primary melt in the upper crust at P =1–4 kbar. Ca. 2400 Ma mafic intrusions in the Kola–Norwegian terrane are similar with coeval mafic dikes in Troms area in the Northern Fennoscandia, basaltic komatiites of Vetreny Belt and doleritic dikes of Kostomuksha area in the Karelian Craton in terms of petrographic, geochemical and Sm-Nd isotopic characteristics. It suggests that studied mafic sills and dikes in the Kola–Norwegian terrane could be considered as a component of ca. 2400 Ma large igneous province in the Fennoscandia. [ABSTRACT FROM AUTHOR]

The volcanic rocks of the Schrikkloof Formation of the Paleoproterozoic Rooiberg Group provide crucial information on the eruptive and depositional processes preceding or concurrent with the intrusive activity of the Bushveld large igneous province of South Africa. A study area near the town of Modimolle (formerly Nylstroom), approximately 190 km north of Johannesburg, was chosen due to the relatively good exposure. The results of this study show that all rocks within the study area, ranging in composition from rhyolites to dacites, have been affected in various ways by circulating hydrothermal fluids, the presence of which is demonstrated by existing hydrothermal breccias and fumarolic features. The volcanic rocks are classified into three lithofacies types, which can be interpreted as low-grade, high-grade, and extremely high-grade welded ignimbrites. The ignimbrite-forming eruptions, which may have been characterized by low columns, were possibly fed by fissures (potentially related to one or more as yet unidentified calderas) associated with a reactivation of the Thabazimbi-Murchison Lineament, a prominent suture zone in the north of South Africa that has been reactivated several times since the Archean. A decline in volcanic activity may be seen near the top of the volcanic succession, which is coupled with a continual increase in clastic sedimentation. This demonstrates a gradational relationship between the volcanic-dominated Schrikkloof Formation and the overlying clastic-dominated Swaershoek Formation of the Waterberg Group. Therefore, the findings of this study may have profound implications for the Paleoproterozoic stratigraphy of South Africa, which hitherto considers the Swaershoek Formation to have an unconformable relationship with the Rooiberg Group below. Furthermore, the evidence provided in this article may aid in the identification and interpretation of other high-grade ignimbrites encountered around the world. • First study on the different degrees of welding of Rooiberg Group rocks. • All Schrikkloof Formation volcanic rocks show evidence of deposition from pyroclastic density currents. • Degrees of welding range from low-grade to extremely high-grade. • First ICP-MS trace element data for the Schrikkloof Formation. • Evidence for significantly prolonged volcanic activity. [ABSTRACT FROM AUTHOR]

Elevated mercury (Hg) in sedimentary strata are a widely used tracer for assessing the relationship between large igneous province (LIP) activity and global environmental change. A key unknown in applying this proxy is the extent to which Hg was sourced from contact metamorphism of sedimentary rocks during sill intrusions versus gaseous emissions of the magmas themselves. Here, we investigate Hg behaviour during contact metamorphism of shales. We show loss of 80–99% of the sedimentary Hg in contact aureoles in four case studies covering the interactions around dykes, sills and plutons associated the High Arctic LIP (Sverdrup Basin, Canada), the Karoo LIP (South Africa) and the Skagerrak-centred LIP (Oslo Rift, Norway). A combination of geochemical data and thermal modelling around a dyke from the High Arctic LIP shows 33% Hg volatilization in the aureole at 265–300 °C. The other cases show similar behaviours with significant lowering of organic-bound Hg, more significantly in the innermost 60% of the contact aureoles. We hypothesize that gaseous Hg is transported out of aureoles during metamorphism, together with CH 4 and CO 2. Furthermore, we estimate the thermogenic Hg mobilization from Karoo LIP aureoles as 72–192 t per km3 of aureole, which is between 1–3 times the estimated volumetric Hg release from Karoo magmas. When scaling our results to the size of the shale portions of the Karoo Basin affected by the LIP and a timescale of 100 kyr of sill emplacement, the average Hg flux is calculated to have been 78–207 t/y with maximum values up to ∼300 t/y. The pulsed nature of intrusive volcanism suggests that this thermogenic Hg flux could have dominated LIP Hg emissions during periods of their life span. Our results demonstrate that the global Hg cycle can be significantly perturbed following LIP-scale sill emplacement into organic-rich sedimentary rocks and our quantification of the emissions based on source-rock analysis provides important information for independent interpretation of the sedimentary Hg record. • Sedimentary mercury is released from shale during contact metamorphism. • Thermal modelling shows that the mercury release starts around 285 C. • The global Hg cycle can be perturbed following LIP-scale sill emplacement. • Our result provides a basis for independent interpretation of Hg records. [ABSTRACT FROM AUTHOR]

Comprehensive paleomagnetic study from the Paraná-Etendeka Igneous Province (PEIP), Serra Geral Formation, southern Brazil (∼ 135 Ma) adds to the scarce southern hemisphere paleomagnetic database. Twelve paleomagnetic sites from the exposed stratigraphy of the PEIP were recovered from basaltic lava flows in northern Rio Grande do Sul state. These volcanic rocks erupted between 131.5 and 135.6 Ma. The reliability of the rock magnetism data was confirmed before being accepted for paleo-intensity analysis. The Thellier-Coe paleointensity protocol was applied to 109 collected specimens, and 26 individual samples from 9 sites were selected to test for consistency of the paleointensity determinations. The new high-quality mean paleointensity value of 30.6 ± 7.2μT corresponds to a virtual dipole moment (VDM) of 5.75 ± 0.49 × 1022 Am2. These values correspond to approximately 72% of the present-day Earth's magnetic field and suggest that the Earth's magnetic field strength was slightly elevated compared to the long-term average geomagnetic field that prevailed during the Cretaceous Normal Superchron. The calculated paleomagnetic pole (Plong = −27.5° and Plat = −78.6°, A95 = 3.5°) presents an angular difference of 22° with respect to the expected pole declination with an inclination of 5°. This difference may correspond to secular variations considering the confidence cones. Our results, when compared with previous paleomagnetic data, approach the accuracy of recent models for the Cretaceous interval. [Display omitted] • New high-quality determination of paleointensity data from the PEIP southern Brazil. • Rapid changes of the magnetic field prior to the CNS long period of stability. • Strength of the ancient magnetic field is slightly below the Earth's present field strength. • The position of the paleomagnetic pole may correspond to rapid variations in the geomagnetic field. • The calculated paleomagnetic pole agrees with the previous and predicted poles of the onset of Cretaceous Normal Superchron. [ABSTRACT FROM AUTHOR]

The emplacement of Large Igneous Provinces (LIPs) during the Neoarchean is thought to have influenced the Earth's surface by modulating global climate and the supply of nutrients to the oceans. However, the links between Neoarchean LIPs and Earth's surface changes are complex and not fully understood due to a lack of sedimentological constraints documenting the relationships between magmatic activity and concomitant depositional environments. At ca. 2.75 Ga, the Amazonia Craton witnessed the emplacement of the Parauapebas LIP, which is mainly composed of vesicular basalts and associated volcaniclastic rocks. The Carajás Formation conformably overlies the basalts of the Parauapebas LIP. It comprises extensive iron formations (IFs) interbedded with minor carbonate and volcaniclastic horizons, which were deposited in various shallow to deep-water settings. Zircon U–Pb dating of volcaniclastic layers yielded ages between 2732 ± 5 Ma and 2720 ± 6 Ma, which indicates that the volcanic activity continued 30–40 Myrs after the main peak in magmatic activity of the Parauapebas LIP. Above the Carajás Formation, the Igarapé Bahia Group consists mainly of terrigenous sediments that are interleaved at their base with minor IFs. This group does not preserve evidence of contemporaneous volcanic activity and comprises detrital zircon populations with ages between ca. 3.0 and 2.7 Ga. The few IFs horizons at the base of the Igarapé Bahia Group could reflect a long-lasting hydrothermal activity linked with the emplacement of the Parauapebas LIP. This LIP thus exerted a major control on depositional environments both in space and time by favoring the deposition of IFs (e.g., in shallow to deep-water settings) during a period that exceeded 30 Myrs. [Display omitted] • The Carajás Formation comprises diversified iron-rich sedimentary facies • The Carajás Formation was deposited between ca. 2750 Ma and ca. 2710 Ma • Iron-rich facies were favored by the Parauapebas LIP activity • No evidence of volcanic activity was observed in the Igarapé Bahia Group [ABSTRACT FROM AUTHOR]

The Cretaceous (Cenomanian, ~96 Ma) basaltic rocks of the Strand Fiord Formation of the Sverdrup Basin of the Canadian Arctic Archipelago, Nunavut, Canada, are a part of the High Arctic large igneous province. The basaltic suite reaches a thickness of almost 1,000 m on Axel Heiberg Island in its depocentre and over 700 m at the studied section. The rocks are variably fractionated tholeiitic basalts, which are geochemically similar to many other continental flood basalts, particularly to low Ti basalts of flood basalt provinces. Geochemical as well as Sr (87Sr/86Srinitial ~ 0.7045 to 0.7067) and Nd (ƐNd(t) ~ +1.3 to +4.3) isotopic signatures of the basalts were inherited during partial melting of spinel peridotite of an ancient subcontinental lithospheric mantle, which was modified around 0.7–0.9 Ga by a metasomatic event. The melting generating the Cretaceous basalts was probably triggered by a mantle plume but was also associated with basin rifting and stretching. There is evidence of plume‐induced doming and uplift of the crust prior to and during the eruption of the basalts as documented by the progression from marine sedimentation to subaerial/lacustrine and then back to marine sedimentation in the Sverdrup Basin centre. The basalts represent parts of the Early Cretaceous igneous province that is dispersed around the Arctic Ocean due to the opening of the Canada Basin, which is inferred to be related to a mantle plume. [ABSTRACT FROM AUTHOR]