Large Igneous Province Research Articles

Globally limited but severe shallow-shelf euxinia during the end-Triassic extinction

One of the most severe extinctions of complex marine life in Earth’s history occurred at the end of the Triassic period (~201.4 million years ago). The marine extinction was initiated by large igneous province volcanism and has tentatively been linked to the spread of anoxic conditions. However, the global-scale pattern of anoxic conditions across the end-Triassic event is not well constrained. Here we use the sedimentary enrichment and isotopic composition of the redox-sensitive element molybdenum to reconstruct global–local marine redox conditions through the extinction interval. Peak δ98Mo values indicate that the global distribution of sulfidic marine conditions was similar to the modern ocean during the extinction interval. Meanwhile, Tethyan shelf sediments record pulsed, positive δ98Mo excursions indicative of locally oxygen-poor, sulfidic conditions. We suggest that pulses of severe marine de-oxygenation were restricted largely to marginal marine environments during the latest Triassic and played a substantial role in shallow-marine extinction phases at that time. Importantly, these results show that global marine biodiversity, and possibly ecosystem stability, were vulnerable to geographically localized anoxic conditions. Expanding present-day marine anoxia in response to anthropogenic marine nutrient supply and climate forcing may therefore have substantial consequences for global biodiversity and wider ecosystem stability.

Coupled volcanic activity and marine anoxia in the Upper Yangtze region prior to the Capitanian mass extinction

The Capitanian mass extinction was a severe biotic crisis in geological history. To present more evidence for this event, this study acquired geochemical data from shelf-margin facies deposits in the Upper Yangtze region, China (i.e., the Shangsi section; the third member of the Maokou Formation [Mao III Member] prior to the Capitanian mass extinction). A significant Hg anomaly is associated with the negative δ13Ccarb excursion in the Mao III Member, suggesting a link to the volcanic activity of the Emeishan large igneous province (ELIP). With increasing water depth, enhanced marine anoxia and stronger water column stratification existed, as evidenced by both organic and inorganic geochemical proxy data. This suggests a possible oceanographic change in response to ELIP volcanism. We propose a three-stage model for the coupled volcanic–climatic–oceanic variations in the Upper Yangtze region during the early Capitanian and the volcanism associated with the ELIP was a potential driving mechanism of the environmental changes and biotic crisis. The ELIP volcanism could have caused the widespread marine anoxia along the continental margin, due to climate warming and the release of nutrient elements. The significant water column stratification and basin restriction were enhanced by climate warming, which would have resulted in expansion of oxygen minimum zones into shelf habitats. This coincided with a decrease in the fusulinacean foraminiferal assemblages and calcareous algae in the Shangsi section. The enhanced marine anoxia and intensified water column stratification may have had a direct role in the death of these organisms. Therefore, widespread marine anoxia/euxinia driven by volcanic activity and climate warming resulted from the ELIP eruption could finally led to the Capitanian biotic crisis.

Metasomatism and depletion of the southern Gawler Craton from combined mantle xenocryst and AusLAMP magnetotelluric data

Metasomatised mantle is considered a prerequisite for the formation of many major ore deposits. Since magnetotellurics (MT) is strongly sensitive to mantle metasomatism, MT is a useful tool for analysis of mineral systems that incorporate a metasomatised mantle as a key ingredient. In this work, we combine recently reported kimberlite-hosted mantle xenocryst data from the southern Gawler Craton and Adelaide Superbasin with AusLAMP MT models. We find good correlations between mantle MT conductors and geochemical indicators of mantle metasomatism from clinopyroxene xenocrysts, with the most metasomatically enriched lithospheric mantle beneath the Adelaide Superbasin and more depleted mantle beneath the Gawler Craton. There is a significant step in lithospheric thickness across the Adelaide Superbasin, and particularly around the Terowie kimberlite cluster. Combined with the fertile mantle, this helps explain this region’s prospectivity for sediment-hosted copper deposits. High mantle resistivities and depleted geochemical compositions towards the central Gawler Craton on and north of the Eyre Peninsula are consistent with melting of previously metasomatised mantle, including during production of the Gawler Range Volcanics and Hiltaba Suite Large Igneous Province. Most of the major iron oxide copper gold (IOCG) and gold deposits in the region lie on the edge of this zone of mantle melting, consistent with mineral systems models that require melting of previously metasomatised mantle in the generation of these deposits.

Geochronological results from the Zhela Formation volcanics of the Tethyan Himalaya and their implications for the breakup of eastern Gondwana

The relationship between the Kerguelen mantle plume and the breakup of eastern Gondwana is still debated. The new Zircon SHRIMP U–Pb dating of 139.9 ± 4.6 Ma, as well as previous ages from the Zhela Formation volcanic rocks in the Tethyan Himalaya, show that the studied Zhela Formation volcanic rocks formed during the Late Jurassic-Early Cretaceous, rather than the Middle Jurassic. The calculated volume of the Comei-Bunbury igneous rocks is ~ 114,250 km3, which is compatible with the large igneous provinces and, consequently, the typical mantle plume models. The new date results, along with existing dates, show that the volcanism attributed to the Kerguelen mantle plume in the Tethyan Himalaya ranges from ca.147 Ma to ca.124 Ma, with two peaks at approximately 141 Ma and 133 Ma. This new finding, together with geochemical and palaeomagnetic data obtained from the Comei-Bunbury igneous rocks, indicate that the Kerguelen mantle plume contributed significantly to the breakup of eastern Gondwana and that eastern Gondwana first disintegrated and dispersed at ca.147 Ma, the Indian plate separated completely from the eastern Gondwana before ca.125 Ma.

Spatial distribution of the critical mineral resource element titanium in China and its influencing factors

In China, titanium is found in multi-metal symbiotic ore deposits that present sorting difficulties, low recovery rates, high production costs, and low overall resource utilization rates. The concentration and distribution of titanium in the pedosphere must be better understood to assess the potential titanium resources. The China Geochemical Baseline project obtained harmonized soil and rock geochemical data covering mainland China and provided reliable data for 76 elements (including titanium) from 3382 top (0–25 cm) and 3380 deep (>100 cm) sediment or alluvial soil samples and 12,201 rock samples. In this study, titanium concentrations were determined by X-ray fluorescence spectrometry under strict quality control. The median titanium concentration values in the top and deep samples, which were considered geochemical baseline values, were 3498 mg/kg and 3406 mg/kg, respectively, with mean values of 3661 mg/kg and 3585 mg/kg, respectively. The titanium concentrations ranged from 266 to 24,674 mg/kg and 324 to 25,504 mg/kg in the top and deep soil samples, respectively. The 75 % range (Q25–Q95) of titanium concentrations in the rock ranged from 978 to 8299 mg/kg. The median titanium concentration was 2555 mg/kg in the rock samples, while the mean concentration was 3089 mg/kg. The geochemical map of titanium indicated that low titanium concentrations below Q25 (<3498 and 3406 mg/kg in the top and deep samples, respectively) are primarily distributed in southern Xinjiang, Tibet, Qinghai, Gansu, and Inner Mongolia. The distribution of low titanium content in the soils is likely attributed to these regions being covered by deserts (e.g., Gobi) and glaciers. Soils with high titanium concentrations are widely distributed in the Emeishan large igneous province at the southwest margin of the Yangzi block, which is related to the large distribution of intermediate-basic rock in the area, as well as along the northeast-southwest direction of the Yangtze block, which extends for nearly 1600 km. Moreover, these soils are mainly associated with the black rock system and intermediate-basic dikes. Soil titanium concentrations are affected by various factors, including the occurrence of tectonic activity and distribution of the black rock system, intermediate-basic rock (especially basalt), and VTi magnetite deposits. In particular, the large igneous province area generated by a mantle column represents the main location of VTi magnetite deposit formation and the area with the highest titanium content. In addition to providing detailed information about the titanium distribution in the pedosphere and rock of mainland China, the project can also provide basic geochemical data for the development and utilization of titanium resources and the formulation of critical mineral industry policies.

Serra Geral Group plumbing system and 3D geological framework in Morungava region, southern Paraná-Etendeka LIP (Brazil): Evidence from borehole, geochemical, and petrophysical data

The Morungava region (east of Porto Alegre-Rio Grande do Sul, Brazil), in the southern half of the Paraná-Etendeka Large Igneous Province (LIP), hosts Serra Geral Group subvolcanic intrusions (sill complex). These intrusions comprise various chemical compositions, including high-Mg rocks. So far, only a few examples of high-Mg rocks have been discovered in the Paraná-Etendeka LIP. Many investigations have been conducted in the Morungava region, yet several questions regarding the distribution, geometry, composition, and structural framework of the subvolcanic bodies in the subsurface remain unanswered. Therefore, we built a three-dimensional geological model of the Serra Geral Group sills and their associated stratigraphic framework in the Morungava region. This was achieved through the combined analysis of geological data (boreholes and geological maps), as well as petrophysical and chemical data, to improve the understanding of these subvolcanic bodies underground. The stratigraphic framework depicts the Precambrian basement topography, the distribution of the Paraná Basin units, and the Rio Grande do Sul Coastal Plain strata, which span the majority of the examined area. To categorize the Serra Geral Group rocks intersected by the boreholes, we established a validation and correlation technique using three separate data sources: laboratory geochemical data, portable X-ray fluorescence measurements, and gamma-ray logs. Using this technique, we classified the Serra Geral Group rocks in the Morungava region into three types (1, 2, 3), which share compositional similarities with Palmas, Vale do Sol, and Torres formations, respectively. Additionally, we identified a fourth type that could be compared to the Lomba Grande Complex, Silica Saturated Olivine Tholeiite-type dikes, and some high-Mg rocks from Namibia.

Identify vestiges of large igneous provinces in deep time: A 0.9 Ga case from North China (Sino-Korean) craton

Large igneous provinces (LIPs) are mostly eroded in deep time; nevertheless, their plumbing systems remained in the crust and weathered materials may be traced in basins. Vestiges of the early Neoproterozoic LIPs are investigated in the North China craton. Two large doleritic sills are dated at ca. 940 Ma and ca. 890 Ma in the Pyongnam basin in Korean peninsula, which are comparable with those coeval ones in the other two basins of the Xuhuai rift. Both of them are featured by ocean island basalt-akin trace element patterns. The ca. 890 Ma sills show stronger depletion in mobile elements, and slightly higher differentiated light and heavy rare earth elements than the ca. 940 Ma sills. They are also chemically affinitive with the ca. 920 Ma Dashigou LIP, but with slightly higher MgO and total alkalis and more differentiated light and heavy rare earth elements. This may indicate a similar (plume) source with probably lower degrees of partial melting in the source region(s) in the magma chamber than the 920 Ma one. Together with the Dashigou, they comprise a cluster of LIPs from the same plume with sequential peaks at ca. 940 Ma, 920 Ma and 890 Ma. Ages of sills and the youngest detrital zircons constrain the sediments to be within 1160–940 Ma for the 940 Ma sill-hosting lower-middle section (e.g., Jikhyon-Mukchon groups) and 940–890 Ma for the 940 Ma-sill free upper section (e.g., Myoraksan Group). A synthetic dataset of all the three basins of the Xuhuai rift reveals a similar depositional age and a similar major provenance (940–900 Ma) for the black-greenish shale-featured formations (e.g., Socheong-Xingmincun-Jinshanzhai formations), which are right above the carbonates with negative inorganic carbon (Majiatun) excursion across much of the Xuhuai rift. The significant 940–900 Ma provenance is featured by zircons resemble those from the local LIPs. It is possible that the provenance was the relevant extrusive rocks of the 940–890 Ma LIPs. This further implies that the ca. 940–920 Ma Majiatun excursion is concurrent with the LIP cluster and is possibly a result of instant turbulence of carbon cycle by the LIPs.

Water Content and Hydrogen Isotopes of Olivine‐Hosted Melt Inclusions in the Dali Picrites, SW China: Reassessing the Role of Water in the Formation of the Emeishan Large Igneous Province

AbstractThe contribution of water to the formation of large igneous provinces (LIPs) remains controversial. We report the first measurement of water content and hydrogen isotope ratios in olivine‐hosted melt inclusions from the Dali picrites, which belong to the Emeishan LIP (ELIP). The inclusions have a wide range of H2O content (0.01–1.73 wt %) and H isotope ratios (δD = 87 ± 11‰ to −267 ± 14‰). The lowest H isotope ratio is below that of the average mantle but comparable to that of the dehydrated slab. These results suggest that most of the Dali melt inclusions have undergone H+ diffusion and H2O degassing. However, some melt inclusions have higher H2O content and lower δD value, which may have undergone rapid cooling and thereby preserved their magmatic H isotope and water content signatures. The reconstructed H2O content of the primary magma for the Dali picrites is ∼1.35 wt %, much lower than the previous estimate for the ELIP primary magma (3.44 ± 0.89 wt % or 4.0–5.6 wt %). Our results support a moderately hydrous (OIB‐type) magma for the ELIP, instead of a highly hydrous one (arc‐type). The mantle source of the picrites is calculated to contain 0.28–0.52 wt % H2O, and recycled oceanic crust that underwent seawater alteration and subsequent slab dehydration during subduction, causing the low δD value of the melt inclusions. We suggest that the Dali picrites may have formed by partial melting of the recycled oceanic crust and metasomatized mantle peridotite.

Age and Geochemistry of High Arctic Large Igneous Province Tholeiitic Magmatism in NW Axel Heiberg Island, Canada

AbstractThe Cretaceous High Arctic Large Igneous Province (HALIP) in Canada involved extrusion of continental flood basalts (CFBs) at 130–120 Ma and 100‐95 Ma and emplacement of an extensive sill and dike network that intersected the Carboniferous to Paleogene Sverdrup Basin. In this paper, we present new 40Ar/39Ar ages, major and trace elements, and Sr‐Nd‐Pb isotope ratios for HALIP lava, dikes, and sills from Bukken Fiord, NW Axel Heiberg Island, Canadian Arctic Islands. Our best constrained 40Ar/39Ar ages yield a weighted average of 124.1 ± 1 (2σ) Ma, coincident with the first pulse of tholeiitic CFB magmatism in the Arctic‐wide HALIP as exemplified by Isachsen Formation flood basalts on Axel Heiberg Island. The Bukken Fiord samples are plagioclase and clinopyroxene‐phyric tholeiitic basalts, are relatively evolved (3.2–6.5 wt% MgO), and share similar major and trace element compositions to typical HALIP tholeiites. Initial 143Nd/144Nd ranges from 0.51260 to 0.51291 and initial 87Sr/86Sr ranges from 0.70362 to 0.70776, while measured 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb range from 18.614 to 19.199, 15.534 to 15.630, and 38.404 to 39.054, respectively. The most primitive sample in this study has Sr‐Nd‐Pb isotope signatures that suggest an enriched plume‐derived mantle source for HALIP tholeiites. Most samples, however, possess relatively radiogenic isotope signatures that can be explained by moderate degrees of assimilation of Sverdrup Basin sedimentary rocks. Magma‐crust interaction in the HALIP plumbing system was likely widespread and may have increased the environmental impact of the HALIP, particularly if crustal carbon was volatilized.

Geochronological, geochemical and isotopic characterisation of the Early Cretaceous Andean margin within Ecuador: The Alao Arc

Tectonic models of the Early Cretaceous Andean margin in Ecuador are hindered by a paucity of accurate crystallisation ages of igneous rocks. The Alao Arc, situated on the western flank of the Cordillera Real in Ecuador, is mainly composed of submarine altered basalts to andesites, and the most deformed areas are frequently modified by greenschist metamorphism. To improve our knowledge of the evolution of the northern Andes prior to the accretion of the Caribbean Large Igneous Province we attempt to constrain the tectonic origin and crystallisation age of the arc's volcanic rocks, using whole-rock geochemistry and isotopic tracing, combined with 40Ar/39Ar geochronology. Major oxides and trace element abundances and Sr-Nd-Pb compositions show that the Alao Arc comprises two separate assemblages, namely, typical arc-like volcanic rocks and E-MORB-like basalts. These have been interpreted to have formed in a continental arc above thinned continental crust in an extensional setting, and the E-MORB-type basalts are considered to have formed in an intra-arc rift. As the Alao Arc's volcanic rocks are devoid of zircon and baddeleyite we attempted to date the time of their crystallisation using 40Ar/39Ar analyses of whole-rock groundmass and plagioclase. However, as the igneous rocks are modified by varying degrees of alteration with the formation of secondary K- and Ca-bearing phases, none of the ∼75 Ma to ∼16 Ma 40Ar/39Ar dates record the age of their crystallisation. The plateau and weighted mean 40Ar/39Ar date populations define peaks at ∼75–60 Ma and ∼ 45–30 Ma that coincide with previously recognised tectonic events that drove fluid circulation, modifying the Ar isotopic compositions. Based on the maximum depositional ages of intercalated sedimentary rocks, the degree of deformation, geochemical and isotopic trends of the Jurassic arc in Ecuador, and correlations with the Early Cretaceous Quebradagrande Arc of Colombia, we propose that the Alao Arc formed during ∼140–110 Ma.

Geochemical benchmarks in the Phanerozoic LIPs constrained from well-cores in the Deccan Volcanic Province, India

The ∼66 Ma Deccan flood basalt province is one of the largest in the World. Here, we present mineral chemistry, bulk-rock geochemistry and NdSr isotopes in the ∼1000 m thick basalt lava sequence extracted from the deep bore-hole well-cores KBH-8 and KBH-7 from the main Deccan Plateau in the southwestern Deccan Volcanic Province. On the basis of trace and rare earth element systematics, we have statistically grouped the accumulated lava into fifteen Eruptive Phases (EPs). The basalts show extreme variation in their initial 87Sr/86Sr (0.7038–0.7166) and εNd (+5.9 to −12.1) isotopic compositions consistent with the involvement of depleted and enriched mantle sources in their genesis. The lavas sourced from the enriched subcontinental lithospheric mantle has been categorized as EP4-type, and EP11-type represents the isotopically depleted lavas derived from a plume asthenospheric source. The remaining EPs resulted from mixing of the components from these two endmembers in some proportion. This essentially reflects upon source contamination rather than crustal assimilation enroute to eruption or emplacement. The unique geochemical and isotopic fingerprint of EP4 and EP11 is traceable in the Phanerozoic LIPs, as well. Therefore, they potentially qualify as “geochemical benchmarks”. The systematic “pinch and swell” pattern observed in the trace element and isotopic compositions throughout the depth profile cannot be reconciled with continuous outpouring of lava. Instead, the EPs erupted in discreet batches in a quick span of time from a periodically replenished tapped fractionated magma chamber fed by a mantle plume at the asthenosphere-lithosphere interface. The results of this study enunciate the critical role of subcontinental lithospheric mantle in the evolution of a continental flood basalt province, irrespective of space and time.

Deep-time Arctic climate archives: high-resolution coring of Svalbard's sedimentary record – SVALCLIME, a workshop report

Abstract. ​​​​​​​We held the MagellanPlus workshop SVALCLIME “Deep-time Arctic climate archives: high-resolution coring of Svalbard's sedimentary record”, from 18 to 21 October​​​​​​​ 2022 in Longyearbyen, to discuss scientific drilling of the unique high-resolution climate archives of Neoproterozoic to Paleogene age present in the sedimentary record of Svalbard. Svalbard is globally unique in that it facilitates scientific coring across multiple stratigraphic intervals within a relatively small area. The polar location of Svalbard for some of the Mesozoic and the entire Cenozoic makes sites in Svalbard highly complementary to the more easily accessible mid-latitude sites, allowing for investigation of the polar amplification effect over geological time. The workshop focused on how understanding the geological history of Svalbard can improve our ability to predict future environmental changes, especially at higher latitudes. This topic is highly relevant for the ICDP 2020–2030 Science Plan Theme 4 “Environmental Change” and Theme 1 “Geodynamic Processes”. We concluded that systematic coring of selected Paleozoic, Mesozoic, and Paleogene age sediments in the Arctic should provide important new constraints on deep-time climate change events and the evolution of Earth's hydrosphere–atmosphere–biosphere system. We developed a scientific plan to address three main objectives through scientific onshore drilling on Svalbard: a. Investigate the coevolution of life and repeated icehouse–greenhouse climate transitions, likely forced by orbital variations, by coring Neoproterozoic and Paleozoic glacial and interglacial intervals in the Cryogenian (“Snowball/Slushball Earth”) and late Carboniferous to early Permian time periods.b. Assess the impact of Mesozoic Large Igneous Province emplacement on rapid climate change and mass extinctions, including the end-Permian mass extinction, the end-Triassic mass extinction, the Jenkyns Event (Toarcian Oceanic Anoxic Event), the Jurassic Volgian Carbon Isotopic Excursion and the Cretaceous Weissert Event and Oceanic Anoxic Event 1a.c. Examine the early Eocene hothouse and subsequent transition to a coolhouse world in the Oligocene by coring Paleogene sediments, including records of the Paleocene–Eocene Thermal Maximum, the Eocene Thermal Maximum 2, and the Eocene–Oligocene transition. The SVALCLIME science team created plans for a 3-year drilling programme using two platforms: (1) a lightweight coring system for holes of ∼ 100 m length (4–6 sites) and (2) a larger platform that can drill deep holes of up to ∼ 2 km (1–2 sites). In situ wireline log data and fluid samples will be collected in the holes, and core description and sampling will take place at The University Centre in Svalbard (UNIS) in Longyearbyen. The results from the proposed scientific drilling will be integrated with existing industry and scientific boreholes to establish an almost continuous succession of geological environmental data spanning the Phanerozoic. The results will significantly advance our understanding of how the interplay of internal and external Earth processes are linked with global climate change dynamics, the evolution of life, and mass extinctions.

The Corrugated Hills Continental Flood Basalt: a c. 2.17 Ga flood basalt province related to breakup of the Superior craton

Abstract This study documents a major continental flood basalt province in the central Labrador Trough that produced voluminous mafic magmatism along the palaeo-rifted margin of the Superior craton. This area, representing a preserved magma volume of approximately 25 000 km 3 , is characterized by classic ‘traps’ topography with columnar-jointed flows and sills separated by thin clastic sedimentary layers. A gabbroic sill near the bottom of the sequence yielded a U–Pb zircon age of 2166 ± 4 Ma, and another near the middle of the sequence yielded a 2171 ± 3 Ma U–Pb zircon age. These ages overlap in time with published ages of mafic dyke swarms that radiate outwards into the adjacent Superior craton, namely the Biscotasing (2172–2167 Ma) and Payne River (2170–2160 Ma) dykes, as well as the Otish sills (2172–2162 Ma) and Tasiataq (2170 Ma) dyke. Our data suggest that these central Labrador magmas, named the Corrugated Hills Continental Flood Basalt, were emplaced near or above a mantle plume head, leading to thermal uplift and then rifting of the Superior craton margin. Field relationships suggest that these magmas were erupted through thinned Archean crust as a rift-related continental flood basalt suite. The Corrugated Hills Continental Flood Basalt province represents remnants of one of the oldest continental flood basalt provinces on Earth.

Petrological models of magma evolution on the formation of mafic-felsic igneous complexes of the Emeishan large igneous province, SW China

Many Late Permian world-class Fe-Ti oxide-bearing layered intrusions in the Pan-Xi region, SW China are commonly considered to be fractionation products of the Emeishan mantle plume-related high-Ti basaltic melts. These layered intrusions coexist spatially and temporally with A-type granitoids, which consist of syenites and granites and are further classified into isotopically depleted metaluminous to peralkaline and isotopically enriched peraluminous to metaluminous groups. The petrogenesis of these mafic-felsic igneous complexes has been controversial. This study investigates geochemical correlations of the microgabbros at the margin of the Baima layered intrusions and the intruding isotopically enriched granitoids. The amphiboles at both sides of the contact zone are calcic (CaO = 10.4 to 12.5 wt.%) and display obvious mixing trends. Thermodynamical modeling using the MAGEMin program indicates that fractionation of basaltic melts compositionally similar to the Baima microgabbros seems incapable to crystallize olivine compositions comparable to those of the layered intrusions, but can be reconciled by early separation of 7.5 to 10 wt.% Fe-Ti-rich melts. Continued differentiation of the basaltic melts may lead to formation of the isotopically depleted granitoids, among which perthite accumulation in water-rich environments could result in the formation of metaluminous granitoids with high Na, K and Al contents and positive Eu anomalies. The isotopically enriched granitoids, on the other hand, can be produced by anatexis of the juvenile mafic lower crust together with the Yangtze ancient lower crust. Our study therefore provides a panoramic view on the complicated petrogenesis of the igneous complexes related to Emeishan mantle plume impingement through thermodynamic modeling.

Identifying crustal contributions in the Patagonian Chon Aike Silicic Large Igneous Province

The volcanic rocks of the Chon Aike Silicic Large Igneous Province (CASP) are recognized as magmas dominantly produced by crustal anatexis. Investigating the zircon of the CASP provides an opportunity to gain further insight into geochemical and isotopic differences of the potential magmatic sources (i.e., crust versus mantle), to identify crustal reservoirs that contributed to the felsic magmas during anatexis, and to quantify the contributions of the respective sources. We present a combined zircon oxygen and hafnium isotope and trace element dataset for 16 volcanic units of the two youngest volcanic phases in Patagonia, dated here with LA-ICP-MS U–Pb geochronology at ca. 148–153 Ma (El Quemado Complex, EQC) and ca. 159 Ma (western Chon Aike Formation, WCA). The EQC zircon have 18O-enriched values (δ18O from 7 to 9.5‰) with correspondingly negative initial εHf values (− 2.0 to − 8.0). The WCA zircon have δ18O values between 6 and 7‰ and εHf values ranging between − 4.0 and + 1.5. Binary δ18O-εHf mixing models require an average of 70 and 60% melt derived from partial melting of isotopically distinct metasedimentary basements for the EQC and WCA, respectively. Zircon trace element compositions are consistent with anatexis of sedimentary protoliths derived from LIL-depleted upper continental crustal sources. The overlap between a high heat flux environment (i.e., widespread extension and lithospheric thinning) during supercontinental breakup and a fertile metasedimentary crust was key in producing voluminous felsic volcanism via anatexis following the injection and emplacement of basaltic magmas into the lower crust.

Editorial: How Large Igneous Provinces (LIPs) during the Triassic shaped modern-day ecosystems

Editorial: How Large Igneous Provinces (LIPs) during the Triassic shaped modern-day ecosystems

Serra Geral Group plumbing system and 3D geological framework in Morungava region, southern Paraná–Etendeka LIP (Brazil): Combining 3D geologic and magnetic models

A coupled 3D geophysical–geological model was constructed by integrating aeromagnetic data and a prior 3D geological model of the Morungava region (Araújo et al., 2023 [manuscript submitted for publication]), situated at the southeastern border of the Paraná–Etendeka large igneous province (LIP) in Brazil. Aeromagnetic data interpretation and modeling (qualitative and semi-quantitative interpretation, susceptibility inversion, forward modeling, and magnetic vector inversion (MVI)), along with magnetic susceptibility data, complemented understanding of the Serra Geral Group feeder system in the subsurface (spatial distribution, depth, and geometry) and illuminated the crustal framework at different depths. We recognized three major NE-elongated geophysical domains (NW, Central, and SE), which were interpreted as basement compartments: the Tijucas, Pelotas, and Jaguarão terranes. The final integrated 3D geophysical–geological model encompasses the stratigraphic framework and the Serra Geral Group plumbing system in the study area, that comprises: two dike systems, four subvolcanic complexes with associated nested sills, and two intrusive ring complexes. This is the first time that these aeromagnetic data have been combined with borehole and 3D geological models.

Fractional crystallization of garnet in alkali basalts at >1.8 GPa and implications for geochemical diversity of Large Igneous Provinces

A suite of lavas from northwest Mull, British Palaeocene Igneous Province, exhibit major and trace element characteristics that are best explained by very high pressure (>1.8 GPa) crystallization of an assemblage comprising aluminous clinopyroxene (Al-Cpx) plus garnet. The resulting series of consanguineous magmas are mildly Si-undersaturated. The trace element effects of this crystallizing assemblage are manifested in increasing light rare earth element (LREE) enrichment and heavy REE (HREE) depletion with decreasing whole-rock MgO, a predictable consequence of the bulk distribution coefficient (D) of this assemblage being > > 1 for HREE but <<1 for the LREE. Early crystallization of Al-Cpx and replacement of plagioclase feldspar by garnet in the crystallizing assemblage also results in increasing or near constant Al2O3 abundances in cotectic compositions with MgO < ∼7 wt%. Garnet as opposed to plagioclase crystallization is also reflected in the incompatibility of Sr and compatibility of Y resulting in very high Sr/Y lavas (up to 100) with high Sr (∼1200 ppm) and low Y contents (∼12 ppm). Lavas also have high Zr/Y (up to 30). Major element constraints suggest the crystallizing assemblage comprised ∼40% garnet and 60% Al-Cpx.Magmas that fractionated at ∼1.8 GPa rose to the surface without interacting with the continental crust. Immediately underlying basalts and picrites show evidence of crustal contamination and assimilated fusible portions of the crust, therefore effectively lining the plumbing system and allowing later magmas to rise to the surface without crustal contamination. A local change in tectonic regime from extension to passive appears to be linked to a change from low pressure to very high-pressure crystallization of magmas. Whilst evidence for garnet fractionation in continental flood basalts is very rare, this paper provides a characterization of its geochemical consenquences.

The Prospect of Detecting Volcanic Signatures on an ExoEarth Using Direct Imaging

The James Webb Space Telescope (JWST) has provided the first opportunity of studying the atmospheres of terrestrial exoplanets and estimating their surface conditions. Earth-sized planets around Sun-like stars are currently inaccessible with JWST, however, and will have to be observed using the next generation of telescopes with direct-imaging capabilities. Detecting active volcanism on an Earth-like planet would be particularly valuable as it would provide insight into its interior and provide context for the commonality of the interior states of Earth and Venus. In this work, we used a climate model to simulate four exoEarths over eight years with ongoing large igneous province eruptions with outputs ranging from 1.8 to 60 Gt of sulfur dioxide. The atmospheric data from the simulations were used to model direct-imaging observations between 0.2 and 2.0 μm, producing reflectance spectra for every month of each exoEarth simulation. We calculated the amount of observation time required to detect each of the major absorption features in the spectra, and we identified the most prominent effects that volcanism had on the reflectance spectra. These effects include changes in the size of the O3, O2, and H2O absorption features and changes in the slope of the spectrum. Of these changes, we conclude that the most detectable and least ambiguous evidence of volcanism are changes in both O3 absorption and the slope of the spectrum.

Effects of Emeishan Large Igneous Province on organic matter accumulation, Sichuan Basin, China

Volcanic activity is often associated with the formation of organic-rich sedimentary deposits. However, the relationships between volcanism and depositional events of hydrocarbon source rock during geological history remain unclear. To fill the knowledge gap, we investigated the relationships based on a case study of the Emeishan Large Igneous Province (ELIP) during the late Guadalupian. We carried out a detailed petrological and geochemical investigation of the upper Maokou Formation (i.e., the Mao III Member) in the Shangsi section, Sichuan Province, China. The Mao III Member has a relatively high abundance of organic matter (OM), good OM type, and appropriate thermal maturity that is conducive to hydrocarbon generation. Paleoenvironmental reconstructions based on multiple geochemical proxies indicate that the Mao III Member records relatively high primary productivity, enhanced anoxic conditions, intense upwelling but weak water mass restriction, decreased detrital input and sedimentation rate, and fluctuations in volcanic and hydrothermal activity. The marked positive correlations between primary productivity, redox conditions, and OM abundance suggest that the former two factors controlled OM accumulation. In addition, the detrital input has a slight dilution effect on the OM abundance. No direct relationship was observed between hydrothermal activity and OM abundance. In contrast, volcanic activity related to ELIP had a major role in enhancing the primary productivity and more reducing conditions, which is confirmed by the marked correlations between Hg/TOC, Cuauth, and Vauth values. This suggests that ELIP volcanism had a significant positive effect on OM enrichment in the Mao III Member, which may be a common feature associated with large volcanic events at other times in Earth's history.