Large Igneous Province Research Articles

Tectonomagmatic evolution of Pune – Nasik Deccan Dykes: Insights from structure and dimension scaling

The Deccan Continental Flood Basalt of the Indian Peninsula is characterized by extensive basaltic eruptions ornamented with three spectacular distinct dyke swarms: the Pune – Nasik, Narmada – Tapi, and Western Coastal dyke swarms. Our study area is the Pune – Nasik dyke swarm, which has ~465 mappable dykes. These dykes exhibit different orientations with a predominant trend of N101° and vary in length from less than 1 km to ~64 km. These dykes are massively jointed and occasionally contain vesicles filled with secondary minerals like quartz and calcite. The host rock is weathered basalt of various older Deccan flows. In this study, we have calculated magmatic overpressures and magma chamber depths using the aspect ratios (length/thickness) of the dykes. The average estimated source depth is ~13 km, based on an average Young's modulus for the host rock basalt (Eavg, 7.5 GPa). Additionally, we compared the inferred magma source depths of the Pune – Nasik, and Narmada-Tapi dyke swarms which include the Nandurbar – Dhule, and Pachmarhi dykes of the Deccan Flood Basalt Province. Our findings indicate that the magma chamber source depth is greater in the Pune – Nasik dyke swarm compared with other dyke swarms. The variation in strike distribution of the Pune-Nasik dyke swarm may be attributed to several factors, including a larger magma chamber, local stress fields generated by shallow magma chamber, or the superimposition of tectonic stress fields (N-S and E-W extension) during the emplacement of dykes. This contrasts with the commonly held belief that the dykes are solely connected to a central edifice of the Reunion hotspot.

Large igneous provinces played a major role in oceanic oxygenation events during the mid-Proterozoic

AbstractLow atmospheric oxygen levels during the mid-Proterozoic were occasionally interrupted by transient high oxygen levels. The cause of mid-Proterozoic ocean redox variability remains unclear. Here we investigate mercury chemostratigraphy across the Jixian section of North China Craton through two oxygenation intervals. Abnormal spikes in mercury concentration and excursions of mercury isotopes are observed in the Dahongyu and Hongshuizhuang formations, which occur just below the two oxygenation intervals, respectively. These mercury anomalies suggest that the two oxygenation events were preceded by subaerial volcanism. Furthermore, the two oxygenation intervals show increased nutrient concentrations and negative shifts in mercury isotopes, indicating that enhanced weathering and terrestrial nutrient influx occurred during oxygenation intervals. We infer that in the breakup setting of the Columbia supercontinent, large igneous province volcanism and its efficient low-latitude weathering could rapidly increase terrestrial nutrient influx into the ocean, promoting oceanic productivity and a pulsed rise in oxygen levels.

Genesis of the Wuchiapingian Formation Tuffs and Their Relationship with the Tectonic Background of the Kaijiang–Liangping Trough in the Northern Sichuan Basin

Controversy surrounds the forming time and tectonic background of the Kaijiang–Liangping Trough in the northern Sichuan Basin. The Wuchiapingian Formation, surrounding this Late Permian trough, contains tuffs, and industrial gas reservoirs have been discovered. However, the genesis of these tuffs, revealed by the drilling wells, remains unclear. In the present work, we analyzed the samples of sedimentary tuff from the core of the study area by macroscopic and microscopic analysis, combined with whole-rock major and trace element analysis, zircon U-Pb dating, and zircon trace element analysis, defining the genesis of the Wuchiapingian Formation tuffs around the Kaijiang–Liangping Trough, in an attempt to describe the initial tectonic context of the trough. The U-Pb ages of the tuffs measured in this study range from 255 to 259 Ma. They are slightly later than the activity of the Emeishan Large Igneous Province. Considering the trough’s distance from the center of the Emeishan Large Igneous Province and its location in the outer zone, it is more likely associated with acidic volcanic eruptions of the island arc. The arc was formed by the subduction activity of the Mianlue Ocean beneath the northern Yangtze Plate. In terms of the timing of activity and the tectonic position of the subduction zone, the Kaijiang–Liangping trough in the northern Sichuan Basin is more closely related to the closing of the Mianlue Ocean.

Ash deposits link Oceanic Anoxic Event 2 to High Arctic volcanism

Oceanic Anoxic Event 2 (OAE 2) was a major environmental perturbation that occurred ∼94 million years ago. It is associated with profound changes in global climate and carbon cycling, which are commonly attributed to large-scale carbon release from large igneous province (LIP) volcanism. However, the specific LIP(s) involved and the mechanisms of carbon release remain poorly understood, as indicated by discrepancies between carbon release rates suggested by numerical models and LIP degassing estimates. Our study refines the eruptive history of the High Arctic large igneous province (HALIP) by dating ashfall deposits in marine sediments from the Canadian High Arctic using an integrated stratigraphic approach. Our results show that silicic HALIP volcanism began tens of thousands of years before OAE 2, suggesting a strong causal link. Volcanic activity coincides with a marked shift in carbon isotope values, linked to the degassing of HALIP magmas and/or thermogenic gas release. We propose that the concurrent activity of two LIPs—the HALIP and the Kerguelen Plateau—could account for the high rates of carbon release inferred for OAE 2, providing a hypothesis for its pervasive environmental impact.

Correlating 300 million years of catastrophes

It is frequently proposed that large bolide impacts and voluminous volcanic eruptions may be responsible for environmental catastrophes. In the conventional approach, the potential causes and consequences are matched using an age-versus-age plot, with preferential ages selected for comparison. This approach inevitably results in a one-to-one correlation, which may be misleading. To address this issue, a novel statistical metric, named conformity, has been proposed which accounts for the possibility of age coincidence resulting from random processes (i.e. bad luck coincidence). The available and updated geochronological datasets of bolide impacts, large igneous provinces, CO2-concentration peaks in the atmosphere, mass extinctions, ocean anoxic events, and climatic optima and thermal highs were subjected to a comparison in terms of their concordance. The most significant discovery is the correlation between the ages of mass extinctions and those of giant bolide impacts (crater diameter >40 km), as well as volcanism of continental large igneous provinces and CO2-concentration peaks in the atmosphere. The severity of mass extinctions appears to be dependent upon the number of simultaneously occurring causes. The most pronounced Late Maastrichtian (∼66 Ma) and Changhsingian (∼252 Ma) mass extinctions were likely caused by a combination of factors, including the simultaneous occurrence of volcanism of continental large igneous provinces, giant bolide impact and CO2-concentration rise in the atmosphere. Conversely, the ages of large igneous provinces, bolide impacts and CO2-concentration peaks are not correlated, indicating that these three causes were not interdependent.

Dynamic evolution of the transcrustal plumbing system in Large Igneous Provinces: Geochemical and microstructural insights from glomerocrysts and melt inclusions

Abstract The nature of the magma plumbing system of Large Igneous Provinces is still poorly understood. Among these exceptional magmatic events from Earth’s past, the end-Triassic Central Atlantic Magmatic Province (CAMP) and the end-Cretaceous Deccan Traps (Deccan) coincided in time with two of the most catastrophic biotic crises during the Phanerozoic. In order to constrain the architecture of their magma plumbing system, glomerocrysts containing abundant bubble-bearing melt inclusions from basaltic lava flows of both CAMP and Deccan were investigated via in situ geochemical and microstructural analyses. The analysed glomerocrysts, dominated by augitic clinopyroxene crystals, represent fragments of a crystal mush entrained by basaltic magmas before eruption. The analysed melt inclusions, consisting of an intermediate to felsic composition glass and CO2-bearing bubbles, represent relics of interstitial melts and fluids within a porous crystal framework forming the crystal mush. The different volume proportions between bubbles and whole inclusions reveal that melt entrapment occurred after volatile exsolution. The minimum observed bubble/inclusion fraction indicates that the CO2 concentration in CAMP and Deccan melts was at least 0.3 wt.%, consistent with a maximum entrapment pressure of about 0.5 GPa at CO2–H2O fluid-saturated conditions. The MgO-rich composition of host clinopyroxene crystals and whole rocks is in contrast with the SiO2-rich composition of (trachy-) andesitic to rhyolitic glass of melt inclusions, pointing to disequilibrium conditions. Thermodynamic and geochemical modelling shows that fractional crystallization alone cannot explain the evolved composition of glass in melt inclusions starting from their whole rock composition. On one side, the oxygen isotope composition of clinopyroxene crystals in glomerocrysts ranges from + 3.9 (± 0.3) to + 5.8 (± 0.3) ‰ and their sample-averaged oxygen isotope composition spans from + 4.4 (N = 10) to + 5.6 (N = 10) ‰, implying that glomerocrysts crystallized from mafic melts with normal (i.e., mantle-like) to slightly low δ18O values. On the other side, the oxygen isotope composition of glass in melt inclusions ranges from + 5.5 (± 0.4) to + 22.1 (± 0.4) ‰, implying that melt inclusions entrapped intermediate to felsic melts with normal (i.e., mantle-like) to extremely high δ18O values, typical of (meta-) sedimentary rocks. Some melt inclusions are compatible with fractionation from the same mafic melts that crystallized their host mineral phase, but most melt inclusions are compatible with variable degrees of crustal assimilation and partial mixing, potentially followed by minor post-entrapment isotope re-equilibration. In the CAMP, where sedimentary basins are abundant, (meta-) pelites and occasionally granitoids were the most likely assimilants. On the contrary, in the Deccan, where sedimentary basins are rare, granitoids and metapelites were the most likely assimilants. Oxygen isotope compositions of glass in melt inclusions, spanning from mantle-like to crust-dominated signatures, suggest that the CO2 within their coexisting bubbles likely derived partly from the mantle and partly from assimilated crustal materials. The investigated glomerocrysts and their bubble-bearing melt inclusions are relics of a multiphase (i.e., solid + liquid + gas phases) crystal mush revealing a dynamic evolution for the magma plumbing system of both CAMP and Deccan, where crystals, silicate melts and exsolved fluids coexisted and interacted through most of the transcrustal section.

Zircon Xenocrysts From Easter Island (Rapa Nui) Reveal Hotspot Activity Since the Middle Jurassic

AbstractWe report the finding of mantle‐derived zircon grains retrieved from red soils, regoliths, and beach sands from Easter Island, that are much older than the island volcanism (0–2.5 Ma) and its underlying lithosphere (Pliocene, 3–4.8 Ma). A large population of 0–165 Ma old zircons have coherent oxygen (δ18O 3.8–5.9‰) and hafnium (εHf(t)+3.5–+12.5) mantle isotopic signatures. These results are consistent with the crystallization of zircon from plume‐related melts. In addition, a chemically diverse population with ages from the Paleozoic to the Archean was found. These older populations are enigmatic but they could represent remnants of ancient subducted sediments. Meanwhile, the ∼0–165 Ma population is interpreted as plume‐derived, suggesting that the hotspot started at least ∼165 Ma ago. A spike of ∼164–160 Ma zircons could represent a Large Igneous Province (LIP) stage upon the first arrival of the plume. We use plate reconstructions to show that such a LIP would have formed on the Phoenix Plate and would have subducted below the Antarctic Peninsula around 100–105 Ma. There, LIP subduction would offer a solution for the enigmatic Palmer Land deformation event, previously proposed to result from a collision with an unknown indenter. The here‐reported “ghost” of a prolonged hotspot activity suggests that fragments of the Easter plume and of the ambient sub‐lithospheric mantle stored and re‐sampled zircon xenocrysts due to convective (re)circulation at the scale of the plume head. Our study demonstrates how zircon geochronology and geochemistry provide novel insights into global‐scale geodynamics, offering new perspectives on the dynamics of mantle plumes and hotspot activity.

Iron Isotopes reveal volcanogenic input during Oceanic Anoxic Event 2 (OAE 2 ∼ 94 Ma)

Anomalously high metal concentrations including iron enrichments are recorded in marine carbonates deposited during Ocean Anoxic Event 2 (OAE 2). These metal enrichments have been attributed to massive submarine eruptions during the formation of one or more large igneous provinces, the proposed trigger for OAE 2 (hydrothermal hypothesis), or to the release of metals from the reoxidation of formerly anoxic marine sediment during a period of temporary cooling during OAE 2 (sediment release hypothesis). Here we use iron stable isotopes to help distinguish between the two hypotheses for a trace metal enriched interval during OAE 2 in the Iona-1 core in the Western Interior Seaway, Texas. Our results show a two-step negative excursion during OAE 2 that is coincident with osmium isotope volcanic proxies measured in the same core, with peak negative values centered on a trace metal-enriched interval. After corrections for detrital and locally supplied iron to the study setting, the δ56Fe value of the remotely supplied iron is –0.28 ± 0.05 ‰, falling in the range of iron δ56Fe values observed in modern hydrothermal plumes (–0.1 to –0.5 ‰), thus supporting the hydrothermal hypothesis as the source of iron and other associated trace metals enriched in the study core during OAE 2. By contrast, the sediment release hypothesis predicts much lower δ56Fe values, between –1.0 ‰ to –3.3 ‰ predicted for benthic supplies of iron from anoxic marine sediment overlying re-oxygenated bottom waters. This study shows that combining iron with other proxies for environmental change, particularly submarine volcanism, can distinguish hydrothermally supplied iron from dust, rivers, and shelf sediment supplies of iron despite iron’s reputation for complicated cycling.

Multi-Stage Evolution of the Oceanic Lithosphere beneath Heard Island, Southern Indian Ocean

Abstract The Kerguelen Plateau is the second biggest submarine large igneous province (LIP) on Earth, however, the nature of the lithospheric mantle source underlying it remains poorly constrained. In this contribution, we provide novel insights into the oceanic lithospheric mantle underlying Heard Island (southern Indian Ocean), which represents the most recent and active phase of volcanic activity (<1 Ma) in the Kerguelen Plateau. We present petrographic and geochemical data for a suite of spinel-bearing harzburgite xenoliths hosted in basanite lavas and provide detailed constraints for distinguishing in situ mantle metasomatism from post-entrapment modification of the xenoliths following interaction with the host magma. We demonstrate that the xenolith mineral compositions and textures preserve a complex multistage history of different modal and cryptic transformations that occurred in the mantle due to: i) high degrees of partial melting that produced highly refractory whole-rock Mg# (Mg# = (Mg + Fe)/Mg × 100; 88–92), major element (FeO/MgO = 0.17) and mineral compositions (e.g. highly forsteritic olivine; Fo = (Mg + Fe)/Mg × 100; 91–92 mol %); ii) solid-state re-equilibration reactions during decompression that caused exsolution of clinopyroxene and Cr-spinel from xenolith orthopyroxene to form symplectite intergrowths; iii) cryptic metasomatism affecting the composition of xenolith clinopyroxene (i.e. enrichment in Na, Th, U and light rare earth elements, and depletion in Rb, Nb, Zr, Hf and Ti) due to interaction with carbonatitic melts in the mantle. Mantle fragments, entrapped by ascending basanite magmas as xenoliths were further modified by reactions with the host magma. This resulted in the partial dissolution of mantle orthopyroxene and replacement by newly formed and compositionally distinct assemblages of clinopyroxene (Mg# 87–91), olivine (Fo: 81–88 mol %) and Cr-spinel (i.e. ‘wehrlitisation’ of the xenoliths). This study highlights the utility of combining petrography and mineral chemistry to decipher the complex and sometimes overprinting and masking effects that different processes (e.g. melting events, metasomatism) exert on the lithospheric mantle, as well as constrain the processes that modify the xenoliths during transport towards the surface.

Mercury evidence of Emeishan volcanism driving the mid-Capitanian (Middle Permian) extinction

The mid-Capitanian (Middle Permian) extinction has been widely attributed to the eruption of the Emeishan large igneous province. Here, we investigate the nature and timing of this link by determining Hg concentrations and isotopic compositions of limestones from the Xiongjiachang section of southwestern China, where Emeishan basalts directly overlie sediments recording the mid-Capitanian extinction horizon. Results show an initial Hg-enrichment interval ∼2.2 m below the mid-Capitanian extinction horizon. Positive Δ199Hg values in the Hg-enrichment interval suggest enhanced volcanic Hg influx into the ocean via atmospheric Hg(II) deposition. The late stage of the mid-Capitanian extinction interval has lower Δ199Hg values, which indicates enhanced input of terrestrial Hg due to ecosystem collapse and soil erosion. The results of this study provide evidence that the Emeishan large igneous province eruption occurred earlier than the mid-Capitanian extinction, and establish a more reasonable temporal link between Emeishan large igneous province volcanism and the mid-Capitanian extinction.

Petrogenesis and an Evaluation of the Melting Conditions of the Late Permian ELIP Picrites, SW China: Constraints Due to Primary Magma and Olivine Composition

The late Permian Emeishan large igneous province (ELIP) in SW China is a melting product of the Emeishan mantle plume. Recently, it has been debated whether peridotite or pyroxenite is the dominant lithology of the mantle source in the ELIP. To address this, systematic analyses of bulk-rock and coexisting spinel and olivine compositions were conducted on picrites from Lijiang–Yongsheng, Dali–Binchuan, Yumen, Muli, and Ertan. The ELIP picrites exhibit positive TiO2–CaO and negative MgO–CaO correlations, as well as low FC3MS values (−0.24–0.1), supporting a peridotite-dominated mantle source. This lithology of the mantle source is also supported by the high 100 × Mn–Fe (1.43–1.73) and Mn–Zn (13.6–18.4) values but low 10,000 × Zn–Fe (8.0–12.7) ratios of the olivine phenocrysts. The estimated mantle potential temperature for Lijiang, Yongsheng, Yumen–Ertan, Muli, and Dali–Binchuan picrites decreased away from Lijiang and Yongsheng, suggesting that the Lijiang and Yongsheng areas were the center of the ELIP. The Lijiang–Yongsheng primary magma shows similar SiO2 content but lower Al2O3 contents (average of 8.24 wt.%) and higher MgO contents (average of 21.42 wt.%) than those of Dali–Binchuan primary magma (Al2O3: 9.86 wt.%; MgO: 19.02 wt.%). Also considering the high Gd–Yb (average of 3.05) and La–Yb (average of 14.61) ratios and mantle potential temperature (average of 1599 °C), we proposed that Lijiang–Yongsheng lavas are produced via the melting of a garnet–peridotitic mantle. In contrast, the Dali–Binchuan lavas with low Gd–Yb (average of 1.91) and La–Yb (average of 5.88) ratios can be explained by their formation in the garnet–spinel transition zone of a peridotitic mantle. The Yumen–Ertan primary magma displays similar mantle potential temperature (average of 1600 °C), Al2O3 and FeO content, and Gd–Yb ratios to those of Lijiang–Yongsheng lavas, indicating that YumenvErtan primary magma may be attributed to the partial melting of garnet with minor peridotite. Therefore, heterogeneous plume-head mantle sources lead to the evaluation of melting conditions of the late Permian ELIP picrites.

Impact of the Jenkyns Event on shallow-marine carbonates and coeval emerged paleoenvironments: the Plitvice Lakes region, Croatia

Early Jurassic (late Pliensbachian–early Toarcian) Large Igneous Province (LIP) magmatism affected the entire ocean-atmosphere system culminating in a cascade of paleoenvironmental perturbations known as the Jenkyns Event which globally impacted marine, transitional and terrestrial paleoenvironments. Carbonate platforms at low latitudes in the Western Tethys realm drowned or shifted to non-skeletal production during the early Toarcian due to sea level rise, global warming, and ocean acidification. Unlike deep-marine deposits, shallow-marine carbonates present a challenge in defining global geochemical signals due to common diagenetic modifications. An integrated dataset including δ13Ccarb and δ18Ocarb, TOC, biomicrofacies, SEM, XRD, and palynological study of two stratigraphic successions in the Plitvice Lakes region, Bjelopolje (BJ) and Plitvice Spring (PS), in Croatia, provides an overview of the paleoenvironmental evolution and lateral facies changes in a peritidal setting during the Early Jurassic on the Adriatic Carbonate Platform (AdCP). The investigated stratigraphic succession starts with upper Pliensbachian, peloid-ooid-bioclastic grainstones alternating with fenestral and massive mudstones overlain by lower Toarcian, lagoonal, bioturbated, “spotted” limestones with horizons indicative of short-lived subaerial emergence during the early Toarcian. A negative excursion in δ13Ccarb, foraminifer assemblages, and the predominance of Classopollis pollen within the “spotted” limestones marks the stratigraphic position of the Jenkyns Event. Global-scale events (sea level variation, climate change, C-cycle perturbation, anoxia) operated simultaneously with local to regional synsedimentary tectonics and eustatic movements that preserved the AdCP carbonate factory from collapse or drowning but resulted in pronounced facies differentiation on the shallow-marine carbonate platforms.

The origin and implications of primordial helium depletion in the Afar mantle plume

Mantle plumes are responsible for the Earth’s largest volcanic provinces. In the prevailing paradigm, the deep mantle is less degassed than convecting shallow mantle, implying that plume-derived lavas have higher concentrations of primordial volatiles such as helium (He). Demonstrating this has led to explanations that question the established Earth model. Here, we show that the 3He/4He of basalts from the Red Sea display coherent relationships with trace elements, allowing the helium concentration of the Afar plume to be calculated. Contrary to the prevailing model it appears the helium concentration of the Afar plume is 10-25% of the upper mantle. This contradiction is resolved if the plume material itself is a mixture of helium-rich high-3He/4He deep mantle with helium-depleted low-3He/4He recently subducted oceanic crust. This implies that helium-depleted domains may exist in convecting mantle and that moderately high 3He/4He plumes likely do not contain a notable contribution of the deep mantle.

Unveiling a major strike-slip fault system associated with the Somún Curá Large Igneous Province in central Patagonia, Argentina

This study presents new evidence of a major, regional strike-slip fault system linked to the emplacement of the Somún Curá Large Igneous Province in central Patagonia, Argentina. Employing a combination of remote sensing techniques and fieldwork, we provide additional insights into the structural complexities underlying this magmatic province, shedding light on its geological evolution. Our findings indicate a compelling correlation between the magmatic products of the Somún Curá Large Igneous Province and the left-lateral strike-slip fault system, resembling similar relationships observed in other magmatic large igneous provinces. Moreover, the strike-slip tectonics delineated in this study likely represent the culmination of the fault system's evolution, possibly originating from a longstanding basement fault and extending beyond the limits of the Somún Curá basaltic plateau.

Origin of hydrothermal dolomitization in the Huize Zn–Pb ore district, SW China: Insights from in situ U–Pb dating, fluid inclusion, and C–O–Sr–Mg isotope analyses

The temporal and genetic association between Mississippi Valley-type (MVT) Zn–Pb mineralization and hydrothermal dolomitization remains controversial. To determine the origin of hydrothermal dolomite and its genetic links with the MVT ore deposit, detailed petrographic observations and geochemical analyses were conducted on various carbonates from the giant Huize MVT Zn–Pb ore district in SW China. The following paragenetic sequence of the carbonates (from the early to late stages) was established: host limestone (ML), early diagenetic micritic dolostone (D1), late diagenetic or pre-ore fine- to medium-grained ferroan dolostone (D2) and medium- to coarse-crystalline non-ferroan dolostone (D3), pre-ore reworked D3 dolomite (D3o), ore-related void-filling dolomite cement (DC), and calcite cement (CC) related to sulfide mineralization. D2, D3, DC, and CC exhibit higher homogenization temperatures for fluid inclusion than the burial temperature, indicating a hydrothermal origin. Geochemical data indicate that D2, D3, D3o, DC, and CC display oxygen isotope depletion and radiogenic Sr isotope enrichment signatures relative to D1. Their parent fluids have more positive δ18O values and similar or lower δ26Mg values relative to those of D1 and seawater. These geochemical proxies indicate that the pre-ore hydrothermal dolomites (D2 and D3) formed from modified seawater circulated in the underlying sandstone aquifers through fault-related thermal convection. DC and CC, related to Zn–Pb mineralization, were formed by the dissolution and reprecipitation of preexisting carbonates. Sphalerite shows higher temperatures and salinities compared with D2 and D3 dolostones, indicating that the ore-forming fluid, different from the hydrothermal dolomitizing fluid, originated from a deep-sourced brine. In situ U–Pb dating of D3o reveals that the pre-ore hydrothermal dolomitization occurred at 253.7 ± 8.7 Ma, and a late-stage hydrothermal imprint occurred at 203 ± 11 Ma, likely related to tectono-thermal events, including the Emeishan large igneous province and Indosinian Orogeny, respectively. These findings imply that the hydrothermal dolomitization and Zn–Pb mineralization in the Huize ore district are likely associated with the multistage basin and basement fluid flows driven by elevated geothermal gradient and tectonic compression, respectively. The void-filling DC and CC and their cathodoluminescence characteristics are useful indicators for MVT Zn–Pb ore exploration.

The timing and duration of large-scale carbon release in the Early Jurassic

The Toarcian oceanic anoxic event (T-OAE, ca. 183 Ma) in the Early Jurassic was one of the most significant warming events of the Phanerozoic, associated with large-scale carbon emissions, mass extinction, and perturbations to hydrology and ocean chemistry. However, the age and duration of this hyperthermal have long been uncertain, hindering our understanding of the timing and pace of carbon release and the associated environmental and biotic changes. We present high-precision radioisotopic dates bracketing a biostratigraphically constrained record of the T-OAE in Japan. Our geochronology reveals an unexpectedly short T-OAE duration of ∼300 k.y. and a temporal coincidence with Ferrar large igneous province (LIP) magmatism. Our dates refute previous work linking the T-OAE to the earlier Karoo LIP, which was coincident with an earlier carbon cycle perturbation at the Pliensbachian−Toarcian boundary. Our results suggest both events were driven by extremely rapid (perhaps sub-millennial scale) thermogenic carbon degassing during LIP sill intrusion.

Carbonatites and related mineralization: an overview

Despite of their scarcity, carbonatites are documented from diverse geological settings, including cratons, continental rifts, orogenic belts and large igneous provinces, which range in age from the Archean to Recent. This study provides a concise overview of the evolution of igneous carbonatites, compiling data on their diverse characteristics and classifying them into mantle- and crustal-derived subtypes. Mantle-derived carbonatites, typically associated with alkaline rocks, are enriched in rare earth elements (REEs) and display geochemical affinities to the mantle. By contrast, crustal-derived carbonatites usually show much lower REE contents and crustal-affinity geochemical features similar to sedimentary carbonaceous rocks. Our study documents the significant economic potential of carbonatites that can host world-class deposits of REE, rare metals, alkaline earth metals and non-metallic resources. Typically, the key processes controlling REE mineralization include the low-degree melting of refertilized mantle, liquid immiscibility, fractional crystallization and hydrothermal fluids. Thus, carbonatites are of significant economic value due to the rapidly increasing global demand for REEs, mainly driven by the ‘green energy transition’.

Potential effects of the Emeishan large igneous province on Capitanian marine anoxia in the Upper Yangtze region

The widespread Capitanian (late Guadalupian) marine anoxia/euxinia has long been regarded as a key driver of the end-Guadalupian (middle Permian) biotic crisis. However, the cause of this marine anoxia is debated, particularly regarding the influence of the Emeishan large igneous province (ELIP). To investigate the contribution of the ELIP to marine anoxia and the possible causal mechanisms, we undertook a conodont biostratigraphic and geochemical study of the middle Permian Maokou Formation in a platform-to-trough transect in the Upper Yangtze region, South China. Our results show that the depositional facies of the Maokou Formation changed from a carbonate ramp to an intra-platform trough within the Jinogondolella (J.) altudaensis zone in the northwestern Yangtze region, which can be attributed to the initial activity of the ELIP. Mantle-derived Sr inputs in the initial and main stages of the ELIP led to two decreases in 87Sr/86Sr during the Capitanian, in the J. shannoni–J. altudaensis and J. prexuanhanensis–J. xuanhanensis zones. The elevated 87Sr/86Sr values during the late Capitanian may have been due to enhanced continental weathering caused by rapid climate warming in response to subaerial eruptions of the ELIP. The deep-water anoxia–euxinia expanded during the middle Capitanian, as indicated by increased MoEF/UEF and V/(V + Ni) values, along with the disappearance of burrows and appearance of small pyrite framboids in the J. altudaensis zone in the Cheng 20 well. However, shallow-water anoxia occurred during the late Capitanian (i.e., J. prexuanhanensis–J. xuanhanensis zone), as evidenced by positive Ce anomalies and losses of aerobic benthic species in the Erya section. Importantly, marine anoxia and negative δ13Ccarb excursions occurred synchronously, but earlier in deep water than in shallow water, potentially indicating an expansion of the oxygen minimum zone (OMZ). The deep-water anoxia corresponded to a decrease in 87Sr/86Sr ratios and the appearance of an intra-platform trough in the J. altudaensis zone, whereas the shallow-water anoxia in the late Capitanian coincided with elevated 87Sr/86Sr ratios. This suggests that the initial activity of the ELIP promoted the development of the OMZ in deep waters during the middle Capitanian, while the subaerial eruptions of the ELIP drove climate warming that led to the expansion of the OMZ into shallow-water platforms during the late Capitanian.

Mechanisms of Co enrichment in the Zhubu Ni–Co–PGE deposit in the Emeishan LIP, SW China: Constraints from mineral geochemistry and Fe–S isotopes of sulfides

The Zhubu Ni–Co–PGE sulfide deposit in the Permian Emeishan Large Igneous Province (LIP), SW China is hosted by a mafic–ultramafic intrusion that comprises two morphologically distinct ore-forming spaces: a central, layered sequence that represents a magma chamber surrounded by a marginal sub-vertical conduit zone. The marginal conduit zone contains significant Ni–Co–PGE sulfide mineralization, suggesting that high volumes of sulfide-bearing silicate melt flowed through the magma conduit system. Determining the hosts of Co is key to understanding the Co enrichment process in the Zhubu deposit, as well as in the Emeishan LIP as a whole. We assess this here using the geochemistry and Fe–S isotope compositions of sulfides in the Zhubu deposit. Cobalt is mainly concentrated in pentlandite sulfide in the websterite, with Co contents increasing in the order pyrrhotite < chalcopyrite < pyrite < pentlandite < violarite; the abundance of violarite, however, is notably lower than that of the other sulfides. The Co contents of pentlandite, pyrite, and chalcopyrite are negatively correlated with their Ni and Fe contents, suggesting that Co substitutes isomorphically for Ni and Fe in the sulfide structure. The δ56Fe values of sulfides increase in the order pyrrhotite < chalcopyrite < pentlandite < pyrite resulted from kinetic fractionation of Fe isotopes. The δ56Fe values of pentlandite and chalcopyrite in lherzolite are higher than those in websterite, implying that lherzolite and websterite formed in compositionally distinct magmas, Fe isotope compositions become heavier with crystal fractionation. The δ34S values of sulfides increase in the order pyrrhotite < pentlandite < chalcopyrite < pyrite, similar to the fractionation sequence of sulfide melts, suggesting that externally derived S was added to the magma and contributed to its sulfide saturation. The Co contents of chalcopyrite and pyrite vary positively with δ56Fe values, and negatively with δ34S values, indicating that the addition of externally derived S and resulting sulfide segregation were critical to Co enrichment.

Repeated pulses of volcanism drove the end-Permian terrestrial crisis in northwest China

The Permo-Triassic mass extinction was linked to catastrophic environmental changes and large igneous province (LIP) volcanism. In addition to the widespread marine losses, the Permo–Triassic event was the most severe terrestrial ecological crisis in Earth’s history and the only known mass extinction among insects, but the cause of extinction on land remains unclear. In this study, high-resolution Hg concentration records and multiple-archive S-isotope analyses of sediments from the Junggar Basin (China) provide evidence of repeated pulses of volcanic-S (acid rain) and increased Hg loading culminating in a crisis of terrestrial biota in the Junggar Basin coeval with the interval of LIP emplacement. Minor S-isotope analyses are, however, inconsistent with total ozone layer collapse. Our data suggest that LIP volcanism repeatedly stressed end-Permian terrestrial environments in the ~300 kyr preceding the marine extinction locally via S-driven acidification and deposition of Hg, and globally via pulsed addition of CO2.