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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. S-isotope and Hg geochemistry across the terrestrial Permian–Triassic mass extinction (252 Ma) provides evidence of repeated volcanic eruptions over ~300 kyr that drove acidification and poisoning of a palaeo-lacustrine ecosystem in northwest China. [ABSTRACT FROM AUTHOR]

The physio-chemical framework that generates carbonatites and, ultimately, the associated rare earth element deposits remains contentious. This primarily reflects the diverse tectonic settings in which carbonatites occur: large igneous provinces, continental rifts and major extensional terranes, syn- to post-collisional settings, or ocean islands. There is, however, a broad consensus that carbonatites (or their parental melts) originate in the mantle. These exotic melts have small volumes that make them ideal probes of conditions in their underlying source regions. We combine the carbonatite locations with global maps of lithospheric thickness, derived from seismic tomography, and show that post-Neoproterozoic carbonatites occur preferentially above the margins of thick cratonic lithosphere (e.g., adjacent to the South Atlantic and Indian Oceans or in North America, Greenland, and Asia) and where once thick lithosphere has undergone stretching (e.g., eastern Asia). Our thermal modeling reveals that lateral and vertical heat conduction on rifted craton margins, or rapid stretching of cratonic lithosphere, can mobilize carbonated peridotite at the temperatures (950–1250 °C) and pressures (2–3 GPa) required to form primary carbonatites or their parental alkali silicate melts. Importantly, our models show that heat conduction from upwelling mantle plumes or ambient mantle on rifted cratonic margins may sufficiently modify the temperature of the lithospheric mantle to cause melting of carbonated peridotite, settling the long-standing debate on the role of rifting and heating in the generation of carbonatites. [ABSTRACT FROM AUTHOR]

We construct the 3D Shear wave velocity and azimuthal anisotropy images in the southern Chuandian block using phase velocity dispersion of Rayleigh wave in the period of 5–45 s. The images show two extensive low-velocity zones with a depth range of 20–40 km. The west range of the low-velocity extends from the Lijiang-Xiaojinhe fault to the Red River fault, while its east range follows along the Xiaojiang fault. Two ranges of low velocities are merged at the southern inner belt of the Emeishan Large Igneous Provinces (ELIP). The observed fast directions of azimuthal anisotropy are consistent with the extension of low-velocity ranges at the lower crust. The findings reveal the presence of two potential weak channels in the lower crust, characterized by low-velocity zones, which align with the hypothesis of lower crustal flow. Meanwhile, the crust around the inner belt of ELIP exhibits a high-velocity body characterized by a northeast-trending and counter-clockwise azimuthal anisotropy. Combined with geological data, we attribute the high S-velocity to a mafic–ultramafic magma reservoir of the ELIP, which blocks the continuity of crustal flow within the southern Chuandian block, thus dividing the lower crustal flow into two branches. Additionally, we also find the fast directions of azimuthal anisotropy above 20 km align well with the strike-slip fault orientations. The above research results indicate that the crustal deformation in the southern Chuandian block is likely attributed to the joint action of the two deformation mechanisms. One involves a lower crustal flow model, while the other entails rigid extrusion controlled by the deep-seated, large-scale strike-slip faults in the upper crust. [ABSTRACT FROM AUTHOR]

Periods of large igneous province (LIP) magmatism have shaped Earth’s biological and climatic history, causing major climatic shifts and biological reorganizations. The vegetation response to LIP-induced perturbations may affect the efficiency of the carbon-climate regulation system and the post-LIP climate evolution. Using an eco-evolutionary vegetation model, we demonstrate here that the vegetation’s climate adaptation capacity, through biological evolution and geographic dispersal, is a major determinant of the severity and longevity of LIP-induced hyperthermals and can promote the emergence of a new climatic steady state. Proxy-based temperature reconstructions of the Permian-Triassic, Triassic-Jurassic, and Paleocene-Eocene hyperthermals match the modeled trajectories of bioclimatic disturbance and recovery. We conclude that biological vegetation dynamics shape the multimillion-year Earth system response to sudden carbon degassing and global warming episodes. [ABSTRACT FROM AUTHOR]

The hydrothermal dolomitization, facilitated by basement fault activities, had an important impact on the Permian Maokou Formation dolomite in the Sichuan Basin, which experienced complex diagenesis and presented strong reservoir heterogeneity. The source and age of diagenetic fluids in this succession remain controversial. In this study, various analyses were implemented on samples collected from outcrops and wells near the No. 15 fault in the eastern Sichuan Basin to reconstruct the multi-stage fluid activity and analyze the impact on reservoir development, including petrology, micro-domain isotopes, rare earth elements, homogenization temperature of fluid inclusions, and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb dating. The homogenization temperature of primary brine inclusions in fine-grained matrix dolomite and saddle dolomite is concentrated between 100 and 150 °C, which indicates that the impacts of abnormally high temperatures of other geological bodies. The δ13C and δ18O value and low 87Sr/86Sr value indicate that the diagenetic fluid of fine-grained matrix dolomite is mainly Permian seawater. The U-Pb ages of fine-grained matrix dolomite are ~260 Ma, which coincides with the age of the main magmatism of Emeishan Large Igneous Province (ELIP), and hydrothermal fluid provided a favorable high-temperature environment in the penecontemporaneous stage. While highly radiogenic 87Sr/86Sr compositions suggests those of saddle dolomite, the high-temperature Sr-rich formation fluid. The U-Pb ages of saddle dolomite are 245–250 Ma, which coincides with the age of the 255~251 Ma magmatism of ELIP. This indicates that those should be the diagenetic products of the ELIP hydrothermal fluid in the shallow burial stage. The U-Pb age of coarse-grained calcite is 190–220 Ma, and it should be the diagenetic product of the deep burial stage. Brine inclusions associated with primary methane inclusions were developed in coarse-grained calcite, with a homogenization temperature range of 140.8–199.8 °C, which indicates that the formation fluid activities were related to hydrocarbon charging. The Permian Maokou Formation dolomite was firstly formed in the penecontemporaneous shallow burial stage, and then it was subjected to further hydrothermal dolomitization due to the basement faulting and the abnormally high heat flow during the active period of ELIP. Hydrothermal dolomitization contributed to the formation and maintenance of intercrystalline and dissolution pores, whereas it also formed saddle dolomite to fill the pores, and reduce the pore space. The influence of deep fluid activities on reservoir evolution is further distinguished. [ABSTRACT FROM AUTHOR]

During the early Cenozoic, the collision and convergence between India and Eurasia resulted in the uplift of the Tibetan Plateau and continuous northward compression, forming the Circum‐Tibetan Plateau Basin and Orogen System (CTPBOS). The Tarim Basin, located between the Tibetan Plateau and the Tianshan Mountains, plays a crucial role for studying the convergence‐driving strain propagation mechanism intra‐Asian continent during the growth processes of the Tibetan Plateau. Owing to the lack of accurate geophysical information on the deep structure of the Tarim crust，the mechanism of Cenozoic deformation in the Tarim Basin has been under debate. In this paper, the teleseismic data acquired by the broadband seismic profile across the Tarim Basin from south to north and the S‐wave receiver function method were used to obtain the depth of the Moho and the discontinuities in the lithosphere beneath the Tarim Basin. The SRF result shows that the Moho geometry has an abrupt relief under the Bachu Uplift, and Moho offset under the fault zone between the Kalashayi Fault and the Tumuxiuke Fault. The regional dip of the Moho under the Bachu area can be explained by the root of the Bachu basement‐involved uplift cutting across the whole crust and locally penetrating into the mantle lithosphere. The Bachu Uplift, located in the central Tarim terrane, has a relatively weak lithosphere. In the process of forming the Tarim large igneous province during the early Permian, the crust beneath the Bachu area was weakened and thinned by the thermo‐mechanical erosion from upwelling mantle plume. As the collision and convergence of India and Eurasia since the early Cenozoic, the convergence‐driving strain was propagated into the Tarim Basin. The pre‐existing weak Bachu Uplift was reactivated. The Tarim Basin absorbs Cenozoic compressional deformation through the crustal shortening and Moho offset of the Bachu Uplift. [ABSTRACT FROM AUTHOR]

High-Ti basalts are commonly believed to represent parental magmas leading to the formation of mafic-ultramafic layered intrusions, such as Late Permian Panzhihua and Hongge in the Emeishan Large Igneous Province (SW China). Consequently, elucidation of the crystallisation and crustal differentiation of high-Ti basalts is critical for our understanding of the petrogenesis of these layered intrusions and the associated oxide ore mineralisation. Here, we present the results of crystallisation experiments carried out in internally heated pressure vessels using a primitive high-Ti basaltic composition. The experiments were conducted at 100 and 300 MPa, in the temperature interval of 950–1200 °C and with water activities (a H2O) from 0 to 1. The oxygen fugacity (f O2) was controlled and varied from FMQ −1 to FMQ +3.3 log units (FMQ corresponds to fayalite-quartz-magnetite buffer). The main mineral phases are olivine, clinopyroxene and plagioclase, accompanied by Cr-Fe-Ti-oxides, orthopyroxene, apatite and amphibole, depending on the conditions. Redox conditions primarily influence the stability fields of Cr-Fe-Ti oxides. Clinopyroxene, orthopyroxene and amphibole are pressure-dependent and have larger stability fields under high pressure conditions. The olivine→orthopyroxene and olivine→amphibole peritectic reactions are observed. Comparisons of phase equilibria between this study and experiments conducted with parental magma of Skaergaard layered intrusion demonstrate the effect of bulk system composition. For instance, ilmenite crystallisation is determined not only by intrinsic parameters such as f O2 but also by additional compositional parameters (e.g. melt Ti, Fe, Al and Mg content). Although COMAGMAT and MELTS modelling results generally reproduce the crystallisation sequence, only the stability field of clinopyroxene and its composition are perfectly modelled. The comparison of experimental results with the rocks from the lowest units of Panzhihua and Hongge layered intrusions are applied to constrain storage conditions in the magma reservoirs. Compared to Hongge, we conclude that the Panzhihua magma chamber was probably located at a shallower depth (~3–6 km), that magma crystallisation started at lower temperatures (~1125–1100 °C), higher f O2 (~FMQ + 1 to FMQ + 2) and that its initial melt H2O content was lower (~0.5–1 wt. %). [ABSTRACT FROM AUTHOR]

A summary of the Jurassic‐Cretaceous rift to breakup tectonostratigraphy of the onshore Sverdrup Basin is correlated to the offshore Amerasia Basin in order to reconstruct a tectonic setting for the High Arctic Large Igneous Province (HALIP). The rift climax from the Canadian rifted margin is correlated with hyper‐extension of the continent‐ocean‐transition zone. Hyper‐extension of the continental lithosphere can accommodate plate motions of Arctic Alaska‐Chukotka away from the Canadian Arctic Islands and Lomonosov Ridge between ∼155 Ma and 135–133 Ma. After lithospheric breakup at ∼135–133 Ma, correlation of the post‐rift stage to the seafloor spreading anomalies M10n to M4n that are associated with oceanic crustal domains can accommodate plate motions from 135–133 Ma to 128 Ma. The uncertainties associated with the earliest magmas of HALIP overlap with the uncertainties on the timing of the latest seafloor spreading. The first main pulse of HALIP in the Aptian at 124–120 Ma post‐dates seafloor spreading and so HALIP was emplaced in a tectonic setting that closely resembles the present state of the south and eastern Amerasia Basin. At the paleogeographic center of the HALIP, the Alpha Ridge complex is consistent with the magmatic character and history of similar Cretaceous oceanic plateau in terms of volume and duration. Plain Language Summary: Prior to recently reported geochronological data from the High Arctic Large Igneous Province (HALIP), the temporal relations were highly uncertain between the tectonic stages of the onshore rift basin (Sverdrup Basin), the HALIP magmatism, and the elusive spreading history of the oceanic portion of the Amerasia Basin (Canada Basin). In the past decade, each of these components has been illuminated by new data to an extent that they can now be correlated. In the summary presented here: (a) it is proposed that the rift climax and the hyper‐extension in the continent‐ocean‐transition zone were coeval and linked processes; (b) that the breakup unconformity identified from the onshore rift basins is consistent with the earliest generation of oceanic crust; and (c) after rifting and seafloor spreading, magmatism of HALIP was a result of a mantle plume that rose to shallow levels below the thin lithosphere of the northern Amerasia Basin. Key Points: Correlation of the geochronology of the High Arctic Large Igneous Province (HALIP) to rift basin tectonostratigraphy indicates that it was emplaced well after the start of the post‐rift stageNon‐correlation of the geochronology of the HALIP to oceanic magnetic anomalies in the Canada Basin indicates it post‐dates seafloor spreadingThese correlations support the oceanic plateau model for the HALIP, centered above the thin lithosphere of the northern Amerasia Basin [ABSTRACT FROM AUTHOR]

This paper completes the examination of results of the study of lithogeochemical characteristics of a pilot collection of the Riphean–Vendian sandstones, siltstones, and claystones (last one based on the interpretation of results) in Belarus. Data on the age of detrital zircon published in recent years suggest that Upper Precambrian rocks of this region were sourced from the Osnitsk–Mikashevichi and the Trans-Scandinavian igneous belts, the Volyn–Brest large igneous province, rapakivi granites, as well as various rock associations of Sarmatia, Danopolonian orogen and Svecofennides. Based on the lithogeochemical characteristics, the distribution of data points of the studied clastic rocks on discriminant diagrams provides insight into the possible provenance, paleogeodynamic, paleogeographic, and paleoclimatic settings and suggests several conclusions. The considered Riphean–Vendian stratons in Belarus are composed mainly of erosion products of within-plate granitoids, as well as various island-arc and syncollisional felsic igneous rocks. The share of erosion products of mafic rocks among them generally does not exceed 30%. It is significant mainly in the Volyn Group rocks (erosion products of the Volyn–Brest large igneous province), as well as in some samples of the Nizov, Selyavy, and Kotlin formations (fragments of mafic rocks from other provenances?). The source-to-sink transport was accomplished mainly by large rivers. Paleogeodynamic settings varied from quite active to quite passive. The paleoclimate in catchment areas was most likely arid/semiarid in the Riphean. In the Vendian, it was humid and varied from subtropical in the Early Vendian (except the Glusk Formation) to tropical in the Late Vendian. The obtained results also make it possible to show some peculiarities of the known methods and techniques of paleoclimate reconstruction. [ABSTRACT FROM AUTHOR]

Large Igneous Provinces (LIPs) are associated with global warming and carbon cycle perturbations during Oceanic Anoxic Event 2 (OAE2, ~94 Ma) and the Mid-Cenomanian Event (MCE, ~96.5 Ma). However, there is still no consensus on the role volcanism played as a trigger, or its source – previously ascribed to the Caribbean LIP or High Arctic LIP. Here, we use Mentelle Basin sedimentary mercury (Hg) concentrations to determine the timing of volcanism, and neodymium (Nd) and strontium (Sr) isotopes for sedimentary provenance. High Hg concentrations compared to Northern Hemisphere records, and a shift to radiogenic Nd isotopes, indicates Kerguelen LIP volcanic activity and plateau uplift occurred in the lead up to and within OAE2. Whilst we find limited evidence that a volcanic event caused the MCE, pulsed Hg spikes before and during OAE2 imply volcanic emissions were key in driving climate and carbon cycle changes and triggering OAE2. Oceanic Anoxic Event 2 was triggered by Kerguelen Large Igneous Province volcanism. Short-lived sedimentary mercury enrichments and changes in sediment provenance suggest that southern hemisphere volcanic activity drove climate and carbon cycle changes. [ABSTRACT FROM AUTHOR]

The study of the deep structure and tectonics of the Arctic region is relevant not only for solving fundamental problems of modern geodynamics, but also for developing natural resources in the circumpolar regions; it is also of interest from the geopolitical view when determining the boundaries of the marginal seas shelves. To analyze the anomalous magnetic field in the Polar Arctic region, experimental CHAMP satellite data were used, obtained at the last stage of its operation, when the orbit altitude decreased to 280–260 km, which made it possible to obtain geomagnetic parameters with higher spatial resolution. For several sectors of the Polar Arctic, maps of the lithospheric magnetic anomalies field distribution for various scales and degrees of averaging over this area were constructed. The anomalies parameters were analyzed and an explanation was proposed for the geological and physical nature of the anomalies, which are images of the most significant geological–tectonic structures of the North Atlantic Igneous Province and complex of Central Arctic underwater rises. The article discusses the relationships between the discovered features of the lithospheric anomalous magnetic field distribution, and the known geological structures of Amerasia and Eurasia, and tectonic processes that occurred here in the past and still proceed now. The results obtained are of interest for further comprehensive geological and geophysical studies and construction of substantiated models of the Arctic region lithosphere evolution. [ABSTRACT FROM AUTHOR]

We investigated velocity and anisotropic structure of the crust beneath the eastern margin of the Tibetan Plateau to better understand its deformation and evolution mechanism. We performed H‐κ and Pms anisotropy analyses to obtain crustal thickness, Vp/Vs ratio, fast polarization direction, and splitting time from 711 stations, and further conducted quality control using slowness, harmonic and statistical analyses. The Songpan‐Ganzi Block has a large splitting time and a fast polarization direction roughly parallel to the GPS motion and SKS fast direction. It also shows an overall high but complex distribution of Vp/Vs ratio, and large variations in crustal thickness, indicating that crustal deformation is likely caused by crustal shortening and lower crustal flow. The northern Sichuan‐Yunnan Rhombic Block (SYRB) is featured by a thick crust and high Vp/Vs ratio, suggesting that the crust is likely inflated by partial melting lower crustal rocks. The subblock also exhibits a strong azimuthal anisotropy with a splitting time greater than 0.6 s. The fast polarization direction aligns with the nearly N‐S extended direction and rotates clockwise in front of the Emeishan Large Igneous Province (ELIP). The observed anisotropy agrees with aligned amphibole minerals under a simple shear condition, supporting a southward lower crust flow being diverted by the ELIP. Anisotropy measurements on the southern SYRB are less robust and widely scattered, suggesting a deformation mechanism different from the northern SYRB. In addition, the southeastern margin of the Sichuan Basin shows a systematic pattern of crustal anisotropy consistent with a pure shear deformation mechanism. Plain Language Summary: We studied the crustal structure and deformation beneath the eastern edge of the Tibetan Plateau. By analyzing teleseismic data from 727 stations, we measured crust thickness, Vp/Vs ratio, and azimuthal anisotropy using receiver functions. Our findings show a complex crustal behavior pattern in the eastern Tibet margin. In the Songpan‐Ganzi Block, crustal shortening and lower crust flow seem to be causing deformation. The northern Sichuan‐Yunnan Rhombic Block, with its thick crust and high Vp/Vs ratio, appears to be influenced by partial melting of lower crust rocks. And a southward lower crust flow being diverted by the Emeishan Large Igneous Province. The eastern and southern part of this block shows a different pattern, indicating a unique deformation mechanism. Additionally, the southeastern margin of the Sichuan Basin appears to undergo a distinct type of crustal deformation. Key Points: A new crustal model with much more reliable and denser Pms anisotropic measurements is built in the eastern Tibetan MarginSongpan‐Ganzi Block is likely deformed by crustal shortening and lower crustal flowChannel flow may exist in the west low velocity zone (LVZ) while absent at the east LVZ [ABSTRACT FROM AUTHOR]

Seamounts and basaltic basement can influence deformation and mass fluxes within subduction zones. We examined seamounts and volcanic units across the western Hikurangi Plateau, near the Hikurangi subduction margin, New Zealand, with seismic reflection images. Volcanism at the Hikurangi Plateau occurred in at least three phases that we attribute to (1) Early Cretaceous large igneous province formation, the top of which is marked by laterally continuous and dipping wedges of reflections that we interpret as lava flows; (2) Late Cretaceous seamounts and volcaniclastics that erupted onto the crust of the Hikurangi Plateau and make up the majority of seamount volume and basement relief; and (3) late-stage, Pliocene volcanics that erupted through and adjacent to Cretaceous seamounts and younger sediments of the northcentral Hikurangi Plateau. The Pliocene volcanoes do not appear to be strongly welded to the plateau basement and may be petit spot volcanoes that are related to the displacement and accumulation of hydrous transition zone melts. Large seamounts and volcaniclastic units are evenly distributed across most of the Hikurangi Plateau near the Hikurangi margin but are absent from the Pegasus Basin. Although faults are imaged throughout the basement of the Pegasus Basin, contemporary normal faulting of the Hikurangi Plateau is uncommon, except for a zone of Quaternary normal faults near the Pliocene volcanics. These trends indicate that the Hikurangi megathrust may be more influenced by volcanic structures in the north and central Hikurangi margin, where plateau rifting and voluminous seamount eruptions have more substantially overprinted the original Early Cretaceous basement. [ABSTRACT FROM AUTHOR]

Although the Aguja Formation (West Texas, southwestern USA) and its fossil vertebrate fauna have been known for over a century, its basic stratigraphic requisites (type area and type section) have not been formally documented. The formation is herein subdivided into a series of formal members, and a lectostratotype section is proposed. Lithostratigraphic and biostratigraphic subdivisions are documented and integrated with geochronologic data to provide an age model for the formation. Four terrestrial vertebrate biozones are proposed. There are at least four major depositional intervals represented in the Aguja and intertonguing Pen Formations. An initial progradational deltaic succession is recorded by the La Basa Sandstone and lower part of the Abajo Shale Members of the Aguja Formation. A second phase of deposition resulted in a retrogradational shoreface succession that includes the upper part of the Abajo Shale, overlying Rattlesnake Mountain Sandstone Member, and lower part of the McKinney Springs Tongue of the Pen Formation, up to a skeletal phosphate bed interpreted to represent the maximum flooding surface. The third phase of deposition comprises a progradational deltaic succession that includes the upper part of the McKinney Springs Tongue, Terlingua Creek Sandstone Member of the Aguja Formation, and lower part of the Alto Shale Member of the Aguja Formation. This third succession records eastward migration of the strandline and withdrawal of the Western Interior Seaway from the Big Bend region. The fourth phase of deposition comprises a series of aggradational fluvial channel and floodplain successions that form the upper part of the Alto Shale Member and is coincident with redirection of stream flow to the southeast. This interval is much thicker in the central part of the Big Bend region, thins to the southwest and northeast, and likely records initial subsidence in the Laramide Tornillo Basin. The upper part of this succession was also contemporaneous with a series of basaltic pyroclastic eruptions, the westernmost expression of the Balcones igneous province. A dramatic constriction in the southern entrance to the Western Interior Seaway through the Gulf of Mexico occurred during this final phase in deposition of the Aguja Formation and corresponds to a shift of stream flow southeastward and to an outbreak of local pyroclastic eruptions. Regional uplift associated with this episode of magmatism is likely responsible for closing the southern aperture of the Western Interior Seaway. [ABSTRACT FROM AUTHOR]

Continental large igneous provinces are among the largest magmatic events on Earth, characteristically manifesting at the surface as stacks of monotonous flood basalt lavas that form through a dynamic pattern of eruptive pulses separated by hiatuses. Such dynamic patterns may be difficult to detect from the composition of the lavas. Instead, lava crystal cargoes can be used to study how the eruption cycles inherent to continental large igneous provinces are moderated by episodic recharge and evacuation at multiple crustal levels. Here, we present a stratigraphically well-constrained series of 56 flood basalt flows from the Eocene Initial Phase of magmatic activity in East Africa. These flows and their crystal cargo permit temporal insight into the development of one of the youngest and best-preserved continental large igneous provinces. The stratiform mafic lavas exposed in northern Kenya consist of alternating aphyric and plagioclase-phyric lava packages consistent with periods of eruption punctuated by volcanic hiatus, where magmas stall and crystallize plagioclase at medium to shallow crustal levels. Plagioclase compositions (n  = 541) exhibit little intra-crystal or intra-sample compositional diversity. Intra-crystal equilibrium calculations for Sr and Ti indicate internal chemical equilibrium, requiring storage at high temperatures over a prolonged time interval (10 000–100 000 years). Using a series of seven interlinked partial crystal fractionation models under equilibrium conditions, we replicate the observed stratigraphic patterns in plagioclase composition. We find that the balance between recharge, evacuation, and diffusive equilibration within a shallow magmatic system controls the composition of plagioclase in these flood basalts. We conclude that the shallow fractionation system modulates eruptive cycles and thus constitutes a critical component in studies of continental large igneous provinces. [ABSTRACT FROM AUTHOR]

Alkaline rocks are widely distributed in various geological environments and are important carriers for exploring the formation and compositional diversity of continental crust. Extensive studies have investigated the processes of mantle melting and crustal differentiation that produced such rocks. However, the potential interaction processes between mantle-derived magma and crust during their formation are poorly constrained. In this study, we focus on a Paleoproterozoic garnet-bearing syenite in the Xiong'er large igneous province (LIP) on the southern margin of the North China Craton through detailed whole-rock and mineral analyses. The high K2O (7.4–8.8 wt %) syenite emplaced at ~1772 Ma with ancient inherited zircon (1800–2800 Ma). The dominant mineral assemblage is composed of clinopyroxene, garnet, and K-feldspar with a small amount of titanite. Complex compositional oscillatory zoning of clinopyroxene and garnet indicates that magma mixing played a significant role in the formation of the syenite. We estimated the major elements composition for melts in equilibrium with clinopyroxene and calculated the clinopyroxene/melt partition coefficients by crystal lattice strain model, thus calculating the trace elements of the equilibrated melts. The equilibrium melts of high Mg# (>85) clinopyroxene have high CaO/Al2O3 (>0.6) and low Hf/Sm (<0.4), which suggests a role for carbonatitic metasomatism of the mantle. The variables La/Yb (24.4–56.1), Dy/Yb (0.8–5.9), and Yb (0.6–10.3 μg/g) indicate that the initial melts were formed by 1% to 2% partial melting of spinel-garnet phlogopite lherzolite. An REE-based model for melts in equilibrium with low Mg# (<85) clinopyroxene indicates that 10% to 30% felsic magma from ancient crust participated in hybridization. In addition to well-documented magma mixing, the oscillatory zoning of garnet is also related to competition with titanite. The initial alkaline magmas have a high water content (~4 wt %), which delays the crystallization of K-feldspar, leading to the enrichment of K2O, until the K-feldspar accumulates in the shallow crust to form the syenite. Magma mixing under an open system further leads to alkalinity enrichment. Magma source and crustal evolution jointly determine the potassium-rich characteristics of syenite. Multiple episodes of magma mixing and fractional crystallization occur in the crust (700–300 MPa), suggesting complex and vertically extensive magma chambers. This study represents the first identification of carbonatitic metasomatism as a mantle source in the Xiong'er LIP. Furthermore, it offers a new perspective on magma mixing between the mantle and crust in transcrustal magmatic systems, contributing to the formation of alkaline rocks. [ABSTRACT FROM AUTHOR]

The Precambrian terranes of the Eastern Indian Shield (EIS) comprise the Bundelkhand, Singhbhum, and Bastar cratons with intervening Proterozoic mobile belts such as Central Indian Tectonic Zone, Eastern Ghats Mobile Belt, Singhbhum Mobile Belt and Chotanagpur Granite Gneissic Complex; and the Proterozoic Mahanadi Rift, Chhattisgarh and Vindhyan Basins, with significant coverage of Indo-Gangetic Plain sediments in the northern part. This study presents the results of a seismically well-constrained 2-D multi-scale potential field modelling to delineate the lithosphere structure across different Precambrian terranes of the EIS. The joint interpretation of the potential field data reveals that (i) the mobile belts are bounded by the deep crustal faults with denser crust, (ii) presence of thick underplated crust below Singhbhum Craton, Singhbhum Mobile Belt, Chotanagpur Granite Gneissic Complex and the surrounding rift basin, (iii) localised Moho upwarp at a depth of ~ 36–37 km below the Proterozoic basins, and (iv) the Lithosphere-Asthenosphere Boundary (LAB) varying between 90 and 200 km below the EIS region. The distinct crustal structure and deeper LAB (130–200 km) below the mobile belts suggest the Proterozoic amalgamation and lithosphere reworking. Below the Singhbhum Craton, the LAB is observed at a depth of ~ 145–155 km, which is comparatively thinner than other cratonic areas elsewhere. The observed crustal underplating and the thinner LAB below the Singhbhum Craton indicate that the lithospheric erosion and magmatic upwelling was caused by the major Paleo-Mesoproterozoic and Early-Cretaceous large igneous province events. [ABSTRACT FROM AUTHOR]

Large igneous provinces (LIPs) are often the surface expressions of mantle plume process. Intensive magma could occur in the continental crust when a mantle plume penetrates the Moho. How magmas migrate in the crust, forming LIPs, remains debated. In this study, we employ 2D thermo‐mechanical numerical modelling to study the dynamics of magma intrusion and migration within the continental crust affected by a mantle plume. Our results suggest that (1) lateral magma migration dominates crustal deformation, promoting the possible formation of metamorphic core complexes; (2) two distinct crustal deformation modes are recognized regarding the presence or absence of crustal break‐up, affected by whether a significant vertical magma migration occurs; (3) the crustal thickness, Moho temperature and the length of the preset weak crust–mantle decoupling zone are the three key parameters controlling crustal magma migration. This study highlights the importance of lateral magma migration in the lower crust and provides physical mechanisms for the interpretation of magma migration under LIPs. [ABSTRACT FROM AUTHOR]

The Amazonian Craton is home to many Statherian to Calymmian taphrogenesis events that evolved over Large Igneous Provinces. The NW-SE faults on the Western Amazonian Igneous Belt (1.82–1.74Ga) and their reactivations, which facilitated the deposition of the Beneficente Group (1.76–1.60Ga), Prainha Formation (1.46Ga), and Alto Tapajós Group (Silurian-Devonian), are associated with these events in the southwest Amazonian Craton. Mineralogical composition, whole-rocks geochemistry, and Nd-Sr-Pb isotopic data show that the three sedimentary successions originated in the provinces of Rondônia-Juruena and Tapajós Parima, particularly during two rift stages. Beneficente Group deposition is associated with Paleoproterozoic Rift 1, while the Prainha Formation represents the post-rift 1, and Alto Tapajós Group deposition is associated with Paleozoic Rift 2. In addition, the Prainha Formation also received sediment supply from the Sunsás Province. These three sedimentary successions have an intrinsic relationship with the reworking of the local basement and their own reworking that occurred from the Paleoproterozoic to the Paleozoic. Autochthonous reworking, particularly in the Colíder and Beneficente groups, is demonstrated by Ti-magnetite grains, volcanic and arenite fragments in the Prainha Formation sublitharenite, and by angular microcline grains, high Au content, a Pb whole-rock isochron yielding the 1.796±0.096Ga age, and by ${\varepsilon _{Sr\left(0 \right)}}$ ε Sr 0 vs 1/Rb relationship in Alto Tapajós Group. ${\varepsilon _{Nd\left(t \right)}}$ ε Nd t and flat REE patterns and some positive Eu anomalies in the Prainha Formation and Alto Tapajós Group record the influence of the mafic rocks of the Mata-Matá suite. A Pb-Pb whole-rock isochron allowed hydrothermal activity recognition at 1.32Ga in the Vila do Carmo Formation. This event was ratified by positive Eu/Eu* (1.3–1.43), Ce/Ce* (1.24–2.84), and Gd/Gd*(~1.5) anomalies. Finally, Nd model ages, geochemistry, and Sr isotopes allow for correlating the local basement and the overlaying sedimentary successions along the Columbia and Gondwana boundaries. [ABSTRACT FROM AUTHOR]

The Carnian Pluvial Episode (CPE) fingerprints global environmental perturbations and biological extinction on land and oceans and is potentially linked to the Wrangellia Large Igneous Province (LIP). However, the correlation between terrestrial environmental changes and Wrangellia volcanism in the Ordos Basin during the CPE remains poorly understood. Records of negative carbon isotopic excursions (NCIEs), mercury (Hg), Hg/TOC, and Hg enrichment factor (HgEF) from oil shales in a large‐scale terrestrial Ordos Basin in the Eastern Tethys were correlated with marine and other terrestrial successions. The three significant NCIEs in the study section were consistently correlated with those in the CPE successions of Europe, the UK, and South and North China. The U‐Pb geochronology indicates a Ladinian–Carnian age for the Chang 7 Member. A comprehensive overview of the geochronology, NCIE correlation, and previous bio‐ and chronostratigraphic frameworks shows that the Ladinian–Carnian boundary is located in the lower part of Chang 7 in the Yishicun section. HgEF may be a more reliable proxy for tracing volcanic eruptions than the Hg/TOC ratio because the accumulation rates of TOC content largely vary in terrestrial and marine successions. The records of Hg, Hg/TOC, HgEF, and NCIEs in the Ordos Basin aligned with Carnian successions worldwide and were marked by similar anomalies, indicating a global response to the Wrangellia LIP during the CPE. Anoxia, a warm‐humid climate, enhancement of detrital input, and NCIEs are synchronous with the CPE interval in the Ordos Basin, which suggests that the CPE combined with the regional Qinling Orogeny should dominate the enhanced rate of terrigenous input and paleoenvironmental evolution in the Ordos Basin. [ABSTRACT FROM AUTHOR]

Magmatic activity is one of the important pathways for the delivery of deep Earth carbon to the surface. The massive carbon release in this process can have significant impacts on atmospheric-oceanic environment. Previous studies have done a lot of work on the relationship between Phanerozoic magmatic activity and carbon release, but there is relatively limited attention has been given to investigating the association between Precambrian magmatic activity and carbon release. The Yanliao Large Igneous Province at 1.32 Ga exhibits extensive development of sills, and the reaction between sills and surrounding rocks triggers the release of carbon. Simultaneously, the magmatic activity during this period is considered as the final response to the breakup of the Columbia supercontinent, coinciding with the occurrence of the Mesoproterozoic Oxygenation Event To explore the connection between this magmatic activity and global carbon cycling, environmental changes and planetary evolution, nine representative stratigraphic columns are selected from the Yanliao area. We use the SILLi 1.0 1D model by utilizing the one-dimensional finite element method (FEM) to simulate and estimate the amount of carbon release triggered by sill emplacement. The simulation results indicate that the emplacement of sills increased the surrounding rock temperature and vitrinite reflectance, leading to a decrease in the total organic carbon (TOC) content. A large amount of organic carbon and inorganic carbon was released, which was initiated by the reaction between sills and surrounding rocks, with a total carbon release up to 1.24 x 1013 tons. The estimated CO2 equivalent released during this magma activity episode is expected to be greater than 4.58 x 1013. In Mesoproterozoic strata, the emplacement of sills activates carbon within the lithosphere could have implications for the global environment. Further work needs to be done in other ancient cratons that possess Lower Riphean strata to find additional evidence of the impact of this magmatic event on the Earth system. From this study, it is evident that magmatic activity during the Precambrian period could promote the activation of carbon in crustal sediments and influence global environment, which can a reference for people to understand the planetary evolution process. [ABSTRACT FROM AUTHOR]

Well-preserved strata of the Ghaap Plateau along the western margin of the proto-Kalahari Craton have been intruded by a large number of mafic dykes. Owing to the scarcity of outcrops, these dykes are generally not well documented and intrusion ages remain poorly understood. In order to address this lack of knowledge, a total of seventeen Ghaap Plateau dykes that included seven north-northeast to northeast-trending dykes, eight northwest-trending dykes and two east to east-northeast-trending dykes were sampled for this study. Here, we report on the petrography and whole rock geochemistry of these dykes. We also report three new U-Pb baddeleyite ages along with some palaeomagnetic data. The mineralogy of the dykes is dominated by clinopyroxene and plagioclase showing varying degrees of alteration. Whole rock geochemical data identify the dykes as basalts with MORB, E-MORB or within plate-like signatures, suggesting an asthenospheric magma source. Our study indicates that the Ghaap Plateau dykes represent several magmatic events of markedly different age. Based on their whole rock geochemical composition, all but one of the dyke samples are tentatively arranged into four distinct groups (Groups A to D). Group A dykes (four dykes) are compositionally similar to the Umkondo Large Igneous Province (LIP). Two north-northeast-trending dykes of this Group yielded overlapping U-Pb baddeleyite ages of 1 103 ± 84 Ma and 1 112 ± 55 Ma, thereby adding to the known footprint of the Umkondo LIP along the western margin of the proto-Kalahari craton. In Group B (four dykes), one northeast-trending dyke yielded a U-Pb baddeleyite age of 1 929 ± 17 Ma. Its palaeomagnetic signature (Lat. 24.5°, Long. 317.6°, A95= 14.20°) is supported by a positive baked contact test and agrees well with the ~1.93 Ga Hartley LIP palaeopole. Group B dykes are thus interpreted to be related to the Hartley LIP, with our new 1 929 ± 17 Ma age supporting a wider extent for the Hartley magmatism than previously known. A new palaeopole for the Hartley LIP (Lat. 22.3°, Long. 327.4°, A95 = 9.25°) was calculated by combining the data of our 1 929 Ma dyke with data reported previously from other sites. Whole rock geochemical data for the remaining dykes are consistent with the Karoo magmatism (two east to east-northeast-trending dykes of Group D) or the ~2.4 Ga Ongeluk LIP (north-trending dyke). The final four dykes (Group C) are difficult to match with other known mafic units. Precise geochronology is needed to confirm the exact age of these unassigned dykes. [ABSTRACT FROM AUTHOR]

Understanding the behavior of mercury (Hg) in organic‐rich sediments as they undergo thermal maturation is important, for example, because enrichment of Hg in sedimentary deposits has become a widely used proxy for volcanism from Large Igneous Provinces (LIPs). In this study, we evaluate the effects of such processes on sedimentary Hg concentrations by investigating a common stratigraphic interval in three drill cores with different levels of thermal maturity (immature, mature and post‐mature) in Toarcian sediments (Posidonienschiefer Formation) from the Lower Saxony Basin, Germany. We present Hg concentrations, bulk organic geochemistry, and total sulfur data. Mercury concentrations in the mature and post‐mature sediments are increased >2‐fold relative to the immature material, which is greater than any potential differences in original Hg concentrations in the studied successions prior to burial. Organic‐carbon and host‐rock mass loss during thermal maturation may have concentrated Hg in the mature sediments to some extent, provided Hg is considered effectively immobile. The increased Hg, TOC‐normalized Hg, and TS‐normalized Hg are most likely linked to the "closed system" behavior of Hg in sedimentary basins and the relatively low temperatures (70–260°C) during maturation that resulted in limited Hg mobility. More speculatively, a certain degree of redistribution of Hg within the mature sediments is suggested by its enrichment in distinct stratigraphic levels. Regardless of the exact mechanisms at play, the elevated Hg concentrations in mature sediments amplify both Hg/TOC and Hg/TS, implying that thermal effects must be considered when using normalized Hg as a proxy for far‐field volcanic activity. Plain Language Summary: This study examines how mercury (Hg) behaves in organic‐rich sediments that undergo thermal maturation, which is crucial for using Hg concentrations as a proxy for paleo‐volcanic activity. We analyzed three drill cores from the Lower Saxony Basin in Germany, each representing different stages of thermal maturity (immature, mature, and post‐mature). We measured Hg concentrations, organic content, and sulfur levels in these sediments. We found that mature and post‐mature sediments show more than double the Hg concentrations compared to immature sediments. This increase is likely due to the loss of organic matter and rock mass during maturation, which concentrates the remaining Hg. The relatively low temperatures (70–260°C) during maturation kept Hg from moving significantly, resulting in higher concentrations in mature sediments. There might be some redistribution of Hg within mature sediments, seen as enrichment in certain layers. Overall, the study highlights that thermal maturation effects must be accounted for when using Hg as a proxy for paleo‐volcanic activity. Key Points: Hg concentrations in thermally matured organic‐rich deposits have increased >2‐foldHg mobilization and recapture may occur during thermal maturation, and may result in stratigraphic increases in Hg concentrationsThe thermal history of sediments must be considered when using Hg as a proxy for volcanism [ABSTRACT FROM AUTHOR]

The widespread High Arctic Large Igneous Province (HALIP) exhibits prolonged melting over more than 50 Myr, an observation that is difficult to reconcile with the classic view that large igneous provinces (LIPs) originate from melting in plume heads. Hence, the suggested plume‐related origin and classification of HALIP as a LIP have been questioned. Here, we use numerical models that include melting and melt migration to investigate a rising plume interacting with lithosphere of variable thickness, that is, a basin‐to‐craton setting applicable to the Arctic. Models reveal that melt migration introduces significant spatial and temporal variations in melt volumes and pulses of melt production, including protracted melting for at least about 30–40 Myr, because of the dynamic feedback between migrating melt and local lithosphere thinning. For HALIP, plume material deflected from underneath the Greenland craton can re‐activate melting zones below the previously plume‐influenced Sverdrup Basin after a melt‐free period of about 10–15 Myr, even though the plume is already ∼500 km away. Hence, actively melting zones do not necessarily represent the location of the deeper plume stem at a given time, especially for secondary pulses. Additional processes such as (minor) plume flux variations or local lithospheric extension may alter the timing and volume of HALIP pulses, but are to first order not required to reproduce the long‐lived and multi‐pulse magmatism of HALIP. Since melting zones are always plume‐fed, we would expect HALIP magmatism to exhibit plume‐related trace element signatures throughout time, potentially shifting from mostly tholeiitic toward more alkalic compositions. Plain Language Summary: Typically, the arrival of a large mantle upwelling ("mantle plume") is expected to cause catastrophic large‐scale volcanism that lasts a few million years. However, a massive past volcanic event now distributed onshore and offshore across the Arctic (the High Arctic Large Igneous Province—HALIP) defies this definition. This wide‐spread magmatism exhibits dates spanning more than 50 Myr, with several pulses of activity. Based on this prolonged magmatism, it has been questioned whether all of it can be attributed to a mantle plume, despite the geochemistry of basalts indicating a plume source. Here, we show that a plume can cause prolonged and multi‐pulse magmatism if it interacts with an increase in lithosphere thickness. Once the plume moves below the thicker lithosphere, hot plume material is channeled along the base of the lithosphere toward the adjacent thinner part, where it can reactivate previous melting regions. At this time, the active plume can be about 500 km away from the melting region, hence plume‐related melt cannot be used as a proxy for the plume position at the given time. Based on the models, we suggest that the prolonged HALIP magmatism was caused by a plume interacting with the edge of a craton. Key Points: Mantle plumes interacting with changes in lithosphere thickness at craton edges can cause prolonged melting with pulses in the same regionRejuvenated melting happens underneath previously melt‐affected thinned lithosphere several hundred km downstream of the plume stemThe timing and duration of rejuvenated melting in models correspond to and therefore may explain observations of magmatic pulses from High Arctic Large Igneous Province [ABSTRACT FROM AUTHOR]

The opening of oceans within accretionary orogens is important for understanding the Wilson cycle. The Mongol–Okhotsk Ocean (MOO) began opening within the early Paleozoic accretionary collage of the Central Asian Orogenic Belt (CAOB), representing a world‐class example to constrain the geodynamic history of ocean opening in accretionary orogens, but the kinematics and mechanisms associated to this process are highly debated. We report on a newly‐discovered bimodal volcanic suite and associated volcanic‐sediments that comprise part of the Altay‐Sayan Rift System, which indicate a widespread Early Devonian extensional event within the CAOB. This extension regime is attributed to a Devonian mantle plume, which is thought to have impinged upon and weakened the lithosphere of the Early Paleozoic collage, and drove the opening of the MOO. Opening of the MOO suggests continent breakup in accretionary orogens tends to focus along intervening weak orogenic lithosphere between the rigid microcontinents. Plain Language Summary: The opening of oceans within subduction related accretionary orogens is a process that is common within the geologic record. The tectonic mechanisms involved in this process, however, are not well understood. The Mongol–Okhotsk Ocean began opening within the Early Paleozoic accretionary collage of the Central Asian Orogenic Belt, providing an opportunity to constrain the geodynamic history of ocean opening in accretionary orogens, but the kinematics and mechanisms related to this process are highly debated. We report on newly‐discovered bimodal volcanic suite (410–415 Ma) and associated volcanic‐sedimentary rocks in Northwest Mongolia, which comprise part of the Altay‐Sayan Rift System (also termed Altay‐Sayan Large Igneous Province). This giant rift system represents a widespread Early Devonian extensional event associated with a mantle plume. The ascent of this mantle plume is thought to have impacted and weakened the lithosphere of northern Early Paleozoic collage, ultimately leading to the opening of the Mongol‐Okhotsk Ocean between microcontinents that had earlier accreted to Siberia Craton. Our model suggests continent breakup in accretionary orogens tends to focus along weak orogenic lithosphere between the rigid microcontinents. Key Points: The 415–410 Ma bimodal volcanic suite and associated volcanic‐sediments document a widespread extension regime related to a mantle plumeThe Devonian mantle plume weakened structures within the accretionary orogen and led to the opening of the Mongol‐Okhotsk OceanContinent breakup in accretionary orogens tends to happen along weak orogenic lithosphere between rigid microcontinents [ABSTRACT FROM AUTHOR]

Ahi Tupua, the central section of the Taupō Volcanic Zone in the central North Island of New Zealand, encompasses Taupō and Ōkataina calderas and has been the most frequently active and productive silicic magma system worldwide during the Quaternary. The entire Taupō Volcanic Zone is underlain by the Hikurangi Subduction Zone where a Large Igneous Province, the Hikurangi Plateau, is being subducted, but Ahi Tupua exhibits much higher rates of magma output than either the northern or the southern sections. Trace element signatures of Ahi Tupua eruptive products suggest that both decompression melting and flux melting play a role in this rifted arc setting, with fluid flux signatures being more prevalent in regions of active caldera volcanism. Intermediate‐depth (50–300 km) earthquakes provide a means of studying faulting and fluid flow processes within and around the subducting slab beneath Ahi Tupua. Using data from the national seismic network and a 13‐station temporary network ("ECLIPSE"), we repick and relocate 397 intermediate‐depth earthquakes of magnitudes M2.5+ that occurred in a 29‐month interval, and compute focal mechanisms for a subset of 47 earthquakes. We observe some seismicity that may be within the mantle wedge but most of the relocated earthquakes occur within the crust and uppermost mantle of the subducted slab and exhibit a weak transition from predominantly normal‐faulting in the slab crust to predominantly reverse‐faulting in the slab mantle. No double seismic zone is observed beneath Ahi Tupua. These observations are consistent with dehydration of the slab and flow of slab‐derived fluids along existing faults into the mantle wedge, that drives flux melting and accounts for the distinctive geochemical signatures and voluminous output of Ahi Tupua calderas. Plain Language Summary: Ahi Tupua is a volcanic region in the North Island of New Zealand that is the most active silicic volcanic system on Earth. It includes the active caldera volcanoes Taupō and Ōkataina. This volcanic region lies above the Hikurangi Subduction Zone, and studies of past eruptions suggest that Ahi Tupua's high rate of activity is driven by fluids released deep in the subduction zone. In this study, we use seismic data from across the entire North Island to investigate earthquakes occurring at depths of 50–300 km within the Hikurangi Subduction Zone. We show that these earthquakes suggest that the subducting oceanic crust is releasing a substantial amount of water into the overlying mantle, causing a large amount of melting and, ultimately, the distinctive volcanism of Ahi Tupua. Key Points: We relocate 397 intermediate‐depth earthquakes beneath Ahi Tupua, central Taupō Volcanic Zone, and compute 47 focal mechanismsMost seismicity occurs within the slab crust and mantle, with subordinate mantle wedge and plate interface faultingHypocenters and focal mechanisms are consistent with slab‐derived fluid fluxing melting of the mantle wedge beneath Ahi Tupua [ABSTRACT FROM AUTHOR]

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]

Water is known to play a crucial role in the generation of many large igneous provinces (LIP) worldwide, but the amount and origin of the water in their sources is still under debate. To address this question, this paper presents in situ major-, trace-element, and Sr isotope data coupled with bulk-mineral O-HHe isotope analyses of amphibole in a suite of aillikites from the Tarim LIP (NW China). The cores of zoned macrocrysts and microcrysts display partially overlapping compositions ranging between edenite and pargasite (75-83 versus 75-80 Mg#), which suggest a common origin from an evolving magma. The rims (Mg# = 75-80) of both macrocrysts and microcrysts are very similar to their cores for many elements, except for higher Sr and Ba contents. All the amphibole zones show similar primitive mantle-normalized trace element patterns, suggesting that they crystallized at different stages during magmatic evolution. This interpretation is confirmed by the homogenous Sr isotope compositions (87Sr/86Sr(i) = 0.70298-0.70394) of these amphiboles, which overlap with those of magmatic apatites and perovskites in these aillikites. The hydrogen isotope compositions (-D = -120‰ to -140‰) of the amphiboles are significantly lower than average mantle values. Given the low water contents (<0.66 wt%) of these minerals, the low H iso signatures of the amphiboles might be caused by variable H2O loss during magma ascent. However, open-system Rayleigh fractionation modeling suggests that the hydrogen isotope compositions of these amphibole phenocrysts cannot be fully reproduced by crystallization following magmatic degassing. These low Î'D values require incorporation of recycled altered oceanic crust containing hydrous components in the plume source of these aillikites, which is consistent with the previously published moderately radiogenic He isotope ratios of olivine separates and bulk-rock Os and Pb isotope data for these same samples. We conclude that water in these magmas was derived from a plume source containing recycled water-bearing oceanic crust. [ABSTRACT FROM AUTHOR]

Many continental large igneous provinces coincide with climate perturbations and mass extinctions. When basaltic plumbing systems traverse carbon-rich sedimentary rocks, large volumes of greenhouse gases may be generated. We document how intrusive sills of the Mesozoic High Arctic Large Igneous Province affected surrounding finegrained, organic-rich siliciclastic rocks of the Sverdrup Basin in the Canadian Arctic Archipelago. Petrographic and X-ray diffraction data from samples located near sills show the presence of high-temperature metamorphic phases (diopside, andalusite, garnet, and cordierite). Raman thermometry on organic matter yields peak temperatures of 385-400 °C near sill contacts, tailing off to far-field temperatures of ≤230 °C. Samples located >20 m from sills show no systematic change in vitrinite reflectance and have a VRo eq% value of ~2.5%, which indicates a temperature of ~210 °C. The finite element thermal modeling tool SUTRAHEAT was applied to the 17-m-thick Hare Sill, emplaced at 3 km depth at 1105 °C. SUTRAHEAT results show that contact-proximal rocks attain temperatures of >700 °C for a brief period (~1 year). By 5 years, the Hare Sill is completely solidified (<730 °C), and the temperature anomaly collapses rapidly thereafter as the thermal pulse propagates outward. By 10 years, all rocks within 10 m of the Hare Sill are between 450 °C and 400 °C, rocks at 20 m from the contact attain 200 °C, yet far-field temperatures (>50 m) have barely changed. When multiple sills are emplaced between 4 km and 6 km depth, all rocks between sills reach ~250 °C after 100 years, showing that it is possible to raise regional-scale background temperatures by ~150 °C for the observed High Arctic Large Igneous Province sill density. Vitrinite reflectance data and pyrolysis results, together with SILLi thermal modeling, indicate that much of the hydrocarbongenerating potential was eliminated by High Arctic Large Igneous Province intrusions. The SILLi model yields ~20 tonnes/m² of organic equivalent CO2 (all carbon gas is reported as CO2) from the Hare Sill alone when emplaced into Murray Harbour Formation rocks with 5.7 wt% organic carbon, and ~226 tonnes/m² by emplacement of multiple sills throughout the 2-km-thick Blaa Mountain Group with 3 wt% organic carbon. On a basin scale, this yields a total of ~2550 Gt CO2 from the Hare Sill, with ~13,000 Gt CO2 being generated by the multiple sill scenario, similar to estimates from other large igneous provinces. Much of the Blaa Mountain Group rocks now have organic carbon contents of <1 wt%, which is consistent with large volumes of carbon-species gas having been generated, likely a mixture of CO2, CH4, and other species. However, organic-rich Murray Harbour Formation rocks show no obvious reduction in organic carbon content toward the Hare Sill intrusive contacts, which suggests that not all of the carbon was lost from the sedimentary package hosting High Arctic Large Igneous Province magmas. We suggest that some of the gas generated by contact metamorphism failed to drain out for lack of high-permeability conduits, and then back-reacted to form calcite cements and pyrobitumen during cooling. [ABSTRACT FROM AUTHOR]

The termination of Neoproterozoic "Snowball Earth" glaciations is marked globally by laterally extensive neritic cap carbonates directly overlying glacial diamictites. The formation of these unique deposits on deglaciation calls for anomalously high calcium carbonate saturation. A popular mechanism to account for the source of requisite ocean alkalinity is the shallow-ridge hypothesis, in which initial spreading ridges surrounding fragments of Rodinia, assumed to be dominated by volcanic margins, were formed at sea level. The shallow ridges are inferred to have promoted widespread deposition and alteration of glassy hyaloclastite--a source of alkalinity. We test this hypothesis by quantifying the prevalence of shallow ridges along Pangea's passive continental margins, and by assessing Neoproterozoic reconstructions of tectonic plates. We find that the most frequently occurring depth range for incipient mid-ocean ridges is 2.1 ± 0.4 km. Ridges with initial elevations of approximately sea level are rare and have anomalous crustal thicknesses >14 km that only occur proximal to large igneous provinces (LIPs). Hyaloclastite is uncommon on mid-ocean ridges as it is generally restricted to water depths of <200 m for tholeiitic basalts, instead forming mostly on intraplate seamounts. Additionally, ocean drilling recently found hyaloclastite to be insignificant along the outer Vøring Plateau (offshore Norway)--an exemplar of a volcanic margin. Reconstructions of Rodinia and associated LIPs demonstrate that volcanic margins potentially hosting minor hyaloclastites were scarce during the late Neoproterozoic. We conclude that the shallow-ridge hypothesis fails to explain the formation of cap carbonates and suggest that other mechanisms such as enhanced continental weathering may be largely responsible. [ABSTRACT FROM AUTHOR]

The Seiland Igneous Province (SIP) is a large province of mafic and ultramafic (UM) complexes interpreted to be relics of a giant plumbing system feeding the Ediacaran Central Iapetus Magmatic Province. The Reinfjord Ultramafic Complex (RUC) is one of the four major ultramafic complexes of the SIP. The RUC has a younger dunite core surrounded by wehrlite and lherzolite embedded in country rocks consisting of layered gabbros with sub‐horizontal layering and metamorphosed sedimentary rocks. Here, we develop a 3D subsurface model for the RUC using high‐resolution magnetic and gravity data and extensive petrophysical measurements from oriented surface samples and drill core samples. Our model indicates that the RUC narrows in depth, extending a minimum of 1.4 km below sea level, and plunges eastwards below the country rock. This model allows us to decipher the lithologic heterogeneities, and the depth and lateral extent of ultramafic rocks, which we interpret in the context of the geologic history of the area. The RUC is spatially separated from other UM complexes of the SIP and the result of this study indicates a smaller depth extent. Combining these findings with the previously reported distribution of the SIP rocks based on the regional gravity data, we propose that the uplift of the crustal block hosting the RUC is larger than for ultramafic complexes in the northwestern part of the SIP. Plain Language Summary: Worldwide, mafic and ultramafic intrusions are considered potential hosts for economic Ni‐Cu and platinum group elements. Magma‐conduit systems are particularly interesting for such mineralization, because they provide an ideal environment for the formation of large economic sulfide occurrences such as the Norilsk Talnakh deposits. We investigate one of the ultramafic complexes of a large magmatic province considered to represent a deep root zone where transient melts passed en route to upper crustal levels. The RUC is an ideal magma‐conduit system for research of large igneous provinces. Here, we construct a subsurface model of the ultramafic complex using gravity and geomagnetic field data constrained by petrophysical data sets from rock samples. We identified the different mafic and ultramafic units, and the alteration of rocks linked to later tectonic events. The localization and the estimation of relative volumes of altered and unaltered mafic and ultramafic rocks provide information about the geodynamic history and the ore potential of these rocks. Key Points: The modeled structure of the ultramafic complex resulted in a minimum volume of 6.5 km3 and an eastward plunging root with depth of 1.4 kmModeling results suggest localized serpentinization of ultramafic rocks with shallow to negative natural remanent magnetization (NRM) inclination and high Königsberger ratioA new proposed uplift history for the Seiland Igneous Province indicating the southern part as a deeper section of the continental crust [ABSTRACT FROM AUTHOR]

The Antarctic ice sheet blankets >99% of the continent and limits our ability to study how subglacial geology and topography have evolved through time. Ice-rafted dropstones derived from the Antarctic subglacial continental interior at different times during the late Cenozoic provide valuable thermal history proxies to understand this geologic history. We applied multiple thermochronometers covering a range of closure temperatures (60-800 °C) to 10 dropstones collected during Integrated Ocean Drilling Program (IODP) Expedition 318 in order to explore the subglacial geology and thermal and exhumation history of the Wilkes Subglacial Basin. The Wilkes Subglacial Basin is a key target for study because ice-sheet models show it was an area of ice-sheet retreat that significantly contributed to sea-level rise during past warm periods. Depositional ages of dropstones range from early Oligocene to late Pleistocene and have zircon U-Pb or 40Ar/39Ar ages indicating sources from the Mertz shear zone, Adélie craton, Ferrar large igneous province, and Millen schist belt. Dropstones from the Mertz shear zone and Adélie craton experienced three cooling periods (1700-1500 Ma; 500-280 Ma; 34-0 Ma) and two periods of extremely slow cooling rates (1500-500 Ma; 280-34 Ma). Low-temperature thermochronometers from seven of the dropstones record cooling during the Paleozoic, potentially recording the Ross or Pan-African orogenies, and during the Mesozoic, potentially recording late Paleozoic to Mesozoic rifting. These dropstones then resided within ~500 m of the surface since the late Paleozoic and early Mesozoic. In contrast, two dropstones deposited during the mid-Pliocene, one from the Mertz shear zone and one from Adélie craton, show evidence for localized post-Eocene glacial erosion of =2 km. [ABSTRACT FROM AUTHOR]

Mafic layered intrusions constitute a natural laboratory to investigate petrogenetic processes using trace element variations in apatite chemistry. Although these intrusions are related to large igneous provinces, there is a wide range of parameters that can affect the chemistry of the primary melt (i.e. composition of the source, pressure, temperature, oxygen fugacity), followed by possible crustal contamination. In this study, we use a comprehensive dataset of analyses of cumulus and intercumulus apatite from a variety of mafic layered intrusions to demonstrate the use of apatite as a powerful petrogenetic indicator. The dataset (determined in this study and compiled from the literature) comprises electron microprobe and LA-ICP-MS analyses, as well as in-situ LA-MC-ICP-MS analyses of Sr isotopes in apatite from well documented layered intrusions (Sept-Iles, Skaergaard, Bushveld, Panzhihua) and the Sudbury Igneous Complex. For the first time, we show that high values of (La/Nd)N, Th, U, Pb, and As in apatite correlate with high (87Sr/86Sr)initial and are related to contamination with continental crust. An elevated (Gd/Yb)N ratio might indicate melting of a mantle source deep enough to retain Yb in garnet. We also confirm that increasingly negative Eu anomaly and decreasing Sr/Y ratio in apatite are indicators of fractional crystallisation of plagioclase, and that high Sr/Y is indicative of early saturation of apatite and/or delayed crystallisation of plagioclase. The reversal to more primitive compositions caused by magma mixing is expressed by higher Sr, V, Mg and Sr/Y ratio, and lower REE + Y, As and Na concentrations in apatite following magma replenishment. Lastly, we show that apatite signature can efficiently distinguish a mafic from a felsic intrusion using its REE and Sr content coupled to its Eu anomaly. It is also possible to further identify the more primitive from the more evolved parts of a mafic layered intrusion, using the Lu, Th, V and volatile (F/Cl) content to distinguish intercumulus from cumulus apatite, respectively. Finally, identifying a mafic magmatic system using detrital apatite in till will prove useful for provenance and mineral exploration studies. [ABSTRACT FROM AUTHOR]

The Komsomolsk tin-ore district is located along the Miao-Chan Ridge in the Middle Amur River area (Khabarovsk krai) within the Badzhal accretionary terrane of the Sikhote-Alin orogenic belt. This work presents new results of U–Pb zircon dating of tonalite from the Miao-Chan complex of the Silinka granite pluton (99.7 ± 1.1 Ma) and rhyolites of the lower part of the Kholdami Formation (98.4 ± 1.0 and 98.7 ± 1.2 Ma) from the northeastern part of the Komsomolsk district. The geochemical characteristics of the rocks studied show that granitoids of the Miao-Chan complex are I-type rocks and that synchronous rhyolites of the Kholdami Formation are highly aluminous and correspond to S-type rocks. New data on the composition and early Cenomanian age of the rocks make it possible to consider the ore-magmatic system of the Komsomolsk ore district as part of the previously identified Albian–Cenomanian igneous province of Pacific Asia. [ABSTRACT FROM AUTHOR]

Competing hypotheses attribute the regional loss of 1.2–1.0 Ga detrital zircon from the Cambrian Sauk Sequence in southwestern North America to differing tectonic controls on surface topography. We test three hypotheses with source‐to‐sink detrital zircon provenance analysis via tandem in situ and isotope dilution U–Pb geochronology paired with geochemical and Hf‐isotope tracers. Our data indicate that the lower‐to‐middle Sixtymile Formation in Grand Canyon was derived from ca. 1.1 Ga rocks of the Llano Uplift and the ca. 539–523 Ma Wichita igneous province, approximately 1400 km away. In contrast, new U–Pb geochronology links the upper Sixtymile and Tapeats formations to the 513–510 Ma Florida Mountains intrusive complex, southern New Mexico, and proximal 1.4 and 1.7 Ga basement approximately 650 km away. We attribute a regional provenance shift to plume–lithosphere interactions on the Iapetan margin, tectonism along 'leaky' intracratonic transverse fault zones and the rift‐to‐drift transition on the Cordilleran margin. [ABSTRACT FROM AUTHOR]

The Cretaceous Period is a vital time interval in deciphering the evolutionary history of the Neo-Tethys Ocean and the convergence of different plates and blocks across the Qinghai-Tibetan Plateau. A detailed stratigraphic framework and paleogeographic patterns are the basis for understanding the evolution of the Neo-Tethys Ocean and the formation of the Qinghai-Tibetan Plateau. Here, the Cretaceous stratigraphy, biota, paleogeography, and major geological events in the Qinghai-Tibetan Plateau are analyzed to establish an integrative stratigraphic framework, reconstruct the paleogeography during the Cretaceous Period, and decode the history of the major geological events. The Cretaceous rocks of the Qinghai-Tibetan Plateau and its surrounding area are predominantly marine deposits, with a small amount of interbedded marine-terrestrial and terrestrial conponents. The Indus-Yarlung Tsangpo Suture Zone was responsible for the deposition of deep marine sediments dominated by ophiolite suites and radiolarian silicalite. To the south, the Tethys Himalayas and Indus Basin received marine sediments of varying depths and lithology; to the north, the Xigaze and Ladakh forearc basins are also filled with marine sediments. The Lhasa Block, Karakorum Block, western Tarim Basin, and West Burma block consist of shallow marine, interbedded marine-terrestrial, and terrestrial sediments. The Qiangtang Basin and other areas are dominated by terrestrial sedimentation. The Cretaceous strata of the Qinghai-Tibetan Plateau and its surrounding areas are widely distributed and diversified, with abundant foraminifera, calcareous nannofossils, radiolarians, ammonites, bivalves, and palynomorphs. On the basis of integrated lithostratigraphic, biostratigraphic, geochronologic, and chemostratigraphic analyses, we proposed herein a comprehensive stratigraphic framework for the Cretaceous Period of the eastern Neo-Tethys. By analyzing the Cretaceous biota of different biogeographic zones from eastern Neo-Tethys and its surrounding areas, we reconstructed the paleobiogeography of different periods of eastern Neo-Tethys. The Cretaceous paleogeographic evolution of the Qinghai-Tibetan Plateau and its surrounding areas can be divided into three phases: (1) gradual breakup of the Indian Plate from the Australia-Antarctica continent and the early collision phase of the Lhasa-Qiangtang blocks (145–125 Ma); (2) northward drift of the Indian Plate and the collision phase of the Lhasa-Qiangtang blocks (125–100 Ma); (3) rapid northward drift of the Indian Plate, formation of the Tarim-Tajik-Karakorum Bay, and early uplift of the Gangdise Mountains (100–66 Ma). The Indus-Tethys Himalayan biota underwent a transition from the cold-water type in the high latitudes of the southern hemisphere to the warm-water type near the equator from the Early Cretaceous to the Mid-Cretaceous. The biodiversity and abundance of the eastern Neo-Tethys Ocean increased gradually in the Early Cretaceous, peaking in the Mid-Cretaceous, and decreased sharply during the late Late Cretaceous (late Maastrichtian). Along with the northward drift of the Indian Plate and subduction of the Neo-Tethys, the eastern Neo-Tethys and its surrounding areas experienced a series of major geological events, including the formation of the large igneous province, oceanic anoxia events, and mass extinction, etc. [ABSTRACT FROM AUTHOR]

The Jenkyns Event (~183 Ma) represents an exceptional warming period in the Jurassic, which is characterized by intense environmental and climate perturbation. The eruption of the Karoo‐Ferrar Large Igneous Province (K‐F LIP) triggered pronounced carbon isotope negative excursion (N‐CIE) in exogenic carbon reservoirs, global widespread organic carbon burial and extensive ocean anoxia. However, the synchronic coupling relationship between the carbon release, volcanic activity, and intense weathering induced by the K‐F LIP during this period remains poorly understood. In this study, detailed sedimentologic and geochemical studies were conducted on the terrestrial stratigraphy of the Lower Jurassic Fuxian Formation in the Ordos Basin. Three spore‐pollen assemblages have been identified, with the Cyathidites‐Deltoidospora‐Chasmatosporites assemblage suggesting a Pliensbachian age, the Classopollis‐Cycadopites‐Chasmatosporites assemblage indicating an early to middle Toarcian age, and the Cyathidites‐Cycadopites‐Psophosphaera assemblage indicating a late Toarcian age. The lower part of the Classopollis‐Cycadopites‐Chasmatosporites assemblage shows a negative CIE with a magnitude of 2.7‰, accompanied by organic carbon enrichment. Mercury concentrations and Hg/total organic carbon ratios also show peaks during the initial stage of the carbon isotope negative shift, implying a synchrony between volcanic activities and carbon perturbation. Furthermore, the Chemical Index of Alteration value has reached its maximum and the kaolinite content shows a sharp increase at the same position as the carbon isotope negative shift initiation, indicating a simultaneous enhancement of continental weathering during volcanic activity. The changing patterns of the continental weathering intensity encompassing the Jenkyns Event also indicate that continental weathering may have functioned as a significant approach to counteract the greenhouse effect caused by substantial volcanic CO2 emissions. [ABSTRACT FROM AUTHOR]

The Sturtian "Snowball Earth" glaciation (ca. 717-661 Ma) is regarded as the most extreme interval of icehouse climate in Earth's history. The exact trigger and sustention mechanisms for this long-lived global glaciation remain obscure. The most widely debated causes are silicate weathering of the ca. 718 Ma Franklin large igneous province (LIP) and changes in the length and degassing of continental arcs. A new generation of two independent Neoproterozoic full-plate tectonic models now allows us to quantify the role of tectonics in initiating and sustaining the Sturtian glaciation. We find that continental arc length remains relatively constant from 850 Ma until the end of the glaciation in both models and is unlikely to play a role. The two plate motion models diverge in their predictions of the timing and progression of Rodinia break-up, ocean-basin age, ocean-basement depth, sea-level evolution, and mid-ocean ridge (MOR) carbon outflux. One model predicts MOR outflux and ocean basin volume-driven sea level lower than during the Late Cenozoic glaciation, while the other predicts outgassing and sea level exceeding those of the Late Cretaceous hothouse climate. The second model would preclude a major glaciation, while the first model implies that the trigger for the Sturtian glaciation could have been a combination of an extremely low MOR outflux (~9 Mt C/yr) and Franklin LIP weathering. Such minimal outflux could have maintained an icehouse state for 57 m.y. when silicate weathering was markedly reduced, with a gradual build-up of MOR CO2 in the atmosphere paired with terrestrial volcanism leading to its termination. [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]

The Cambrian explosion, one of the most consequential biological revolutions in Earth history, occurred in two phases separated by the Sinsk event, the first major extinction of the Phanerozoic. Trilobite fossil data show that Series 2 strata in the Ross Orogen, Antarctica, and Delamerian Orogen, Australia, record nearly identical and synchronous tectono-sedimentary shifts marking the Sinsk event. These resulted from an abrupt pulse of contractional supracrustal deformation on both continents during the Pararaia janeae trilobite Zone. The Sinsk event extinction was triggered by initial Ross/Delamerian supracrustal contraction along the edge of Gondwana, which caused a cascading series of geodynamic, paleoenvironmental, and biotic changes, including (i) loss of shallow marine carbonate habitats along the Gondwanan margin; (ii) tectonic transformation to extensional tectonics within the Gondwanan interior; (iii) extrusion of the Kalkarindji large igneous province; (iv) release of large volumes of volcanic gasses; and (v) rapid climatic change, including incursions of marine anoxic waters and collapse of shallow marine ecosystems. [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]

Owing to the paucity of research on synchronous mafic rocks in the Tarim Basin, the late Paleozoic–early Mesozoic tectonic development of this region is not well defined. The Halaqi region is situated on Tarim's northwest edge, and numerous mafic dikes can be found cross-cutting the Permian strata. The whole-rock geochemistry, zircon U–Pb age, and Sr–Nd isotopic signature of these mafic rocks have never been reported before, and this contribution can offer geochronological and petrogenetic investigations that provide fresh insight into the geodynamic development of the area. Major oxide contents in the Halaqi mafic rocks vary, including SiO2 (45.74–50.31 wt.%), Al2O3 (13.28–14.8 wt.%), FeOT (16.48–19.19 wt.%), MgO (7.58–10.32 wt.%), CaO (7.19–12.39 wt.%), Na2O (2.97–4.50 wt.%), K2O (0.24–0.63 wt.%), TiO2 (1.11–1.29 wt.%), MnO (0.14–0.16 wt.%), and P2O5 (0.13–0.17 wt.%). The mafic rocks are enriched in high-field-strength elements (e.g., Zr and Hf) and large-ion lithophile elements (e.g., Sr, Th, and U) but depleted in Nb, Ta, and P. The total REEs in the rocks are lower (ΣREE = 72.80–86.85 ppm), and HREEs are somewhat depleted in comparison to LREEs, with positive Eu anomalies (Eu/Eu* = 1.05–1.17) but weak negative Ce anomalies (Ce/Ce* = 0.91–0.93). Zircon U–Pb ages of 201–247 Ma were obtained from a total of 18 magmatic zircon grains found in the mafic rocks that were studied. These results point to a middle-to-late Triassic emplacement. The mafic dikes exhibit somewhat enriched Nd isotopic compositions (εNd(t) = –1.6~–0.2) and an older Nd model age (TDM = 1.24–1.37 Ga). The Halaqi middle–late Triassic mafic dikes are thought to have originated from the same tectonic background as the Permian Tarim Large Igneous Province, along with similar geochemical and isotopic compositions. This suggests that they are all products of the interaction between asthenospheric and lithospheric mantles in an intraplate extensional environment. Research indicates that the Triassic mafic magmatism in northwest Tarim could be the product of the continuous thermal pulse of the Tarim mantle plume and be a part of the Tarim LIP. [ABSTRACT FROM AUTHOR]

The Southwestern Laurentia large igneous province (SWLLIP) comprises voluminous, widespread ca 1.1 Ga magmatism in the southwestern United States and northern Mexico. The timing and tempo of SWLLIP magmatism and its relationship to other late Mesoproterozoic igneous provinces have been unclear due to difficulties in dating mafic rocks at high precision. New precise U-Pb zircon dates for comagmatic felsic segregations within mafic rocks reveal distinct magmatic episodes at ca. 1098 Ma (represented by massive sills in Death Valley, California, the Grand Canyon, and central Arizona) and ca. 1083 Ma (represented by the Cardenas Basalts in the Grand Canyon and a sill in the Dead Mountains, California). The ca. 1098 Ma magmatic pulse was short-lived, lasting 0.25-0.24 +0.67 m.y., and voluminous and widespread, evidenced by the ≥100 m sills in Death Valley, the Grand Canyon, and central Arizona, consistent with decompression melting of an upwelling mantle plume. The ca. 1083 Ma magmatism may have been generated by a secondary plume pulse or post-plume lithosphere extension. The ca. 1098 Ma pulse of magmatism in southwestern Laurentia occurred ∼2 m.y. prior to an anomalous renewal of voluminous melt generation in the Midcontinent Rift of central Laurentia that is recorded by the ca. 1096 Ma Duluth Complex layered mafic intrusions. Rates of lateral plume spread predicted by mantle plume lubrication theory support a model where a plume derived from the deep mantle impinged near southwestern Laurentia, then spread to thinned Midcontinent Rift lithosphere over ∼2 m.y. to elevate mantle temperatures and generate melt. This geodynamic hypothesis reconciles the close temporal relationships between voluminous magmatism across Laurentia and provides an explanation for that anomalous renewal of high magmatic flux within the protracted magmatic history of the Midcontinent Rift. [ABSTRACT FROM AUTHOR]

The large Mo isotopic fractionations between diferent geological reservoirs make this isotopic system a potentially useful tool for constraining the origins of magmatism. However, the efect of magmatic diferentiation on Mo isotopes is still controversial. In this study, we obtained Mo isotope data for the Panzhihua gabbroic intrusion (i.e., including mineral separates of clinopyroxene, plagioclase, magnetite, and ilmenite). The whole-rock samples and mineral separates exhibit large Mo isotopic fractionations with δ98/95Mo values as follows: magnetite (–0.73‰ to –0.32‰) < clinopyroxene (–0.32‰ to –0.10‰) < ilmenite (0.06‰ to 0.36‰) < plagioclase (0.33‰ to 0.83‰). Iron-Ti oxides have Mo contents that are one order of magnitude higher than those of clinopyroxene and plagioclase. Mass balance calculations based on Mo isotopes and contents are consistent with an accumulated origin for the Panzhihua intrusion. Rayleigh fractionation modeling shows that the removal of magnetite and ilmenite results in significant Mo isotopic fractionation in the residual magma. Due to the low Mo contents of clinopyroxene and plagioclase, Mo isotopes are not significantly fractionated by the removal of these minerals. Therefore, our study highlights that fractionation of Fe-Ti oxides can cause considerable Mo isotopic fractionation; consequently, caution is needed when using Mo isotopes to infer magma origins. [ABSTRACT FROM AUTHOR]

The Kotuy intrusive complex was identified from the geological survey of the western slope of the Anabar Massif in the middle reaches of the Kotuy River. It is represented by dolerite–gabbrodolerite sills and dikes of Vendian age (556 ± 28 Ma). A number of sills are characterized by 30–80 m thickness, and dikes often have a length of a few dozen kilometers. The distribution area of the complex is a few hundred square kilometers. However, the geodynamic evidence for the formation of extensive intrusive bodies in the northern part of Siberia in the Vendian is not clear. We present new geochronological, geochemical, and paleomagnetic data indicating that at least part of the Kotuy magmatic complex intrusions in the middle reaches of the Kotuy River should be attributed to the ~1500 Ma Kengede magmatic complex (Kuonamka large igneous province). In this light, the very existence of Vendian intrusive magmatism on the western slope of the Anabar massif appears questionable. [ABSTRACT FROM AUTHOR]

Ancient orogens within the supercontinent like Columbia can remain stable evolution as long as the cratons. What kind of lithospheric mantle was beneath those orogens and how it evolved into a stable state are still enigmatic. The Trans‐North China orogen (TNCO) is one of the typical collisional orogens within the Columbia supercontinent and was formed at ca. 1.85 Ga. Our work reveals that a cluster of kimberlites intruded the orogenic belt at ca. 1.54 Ga. These rocks were originally generated under a thick lithosphere (>200 km). Their entrained olivine cores show a composition of overlapping olivines from refractory mantle peridotites. The results suggest a thick and refractory lithospheric mantle beneath the TNCO at ca. 1.54 Ga. Such craton‐like property may result from large volume melt extraction from the lithospheric mantle, possibly caused by the ca. 1.78 Ga large igneous event, which eventually induces the long‐term stability of the TNCO during the subsequent supercontinent cycle. [ABSTRACT FROM AUTHOR]

Our study of boreholes, seismic survey and magnetic data from the region between the Baltic Basin and the Lublin Basin indicates the existence of numerous buried intrusions and effusive complexes, most of them unnoticed so far, together with a few igneous massifs. They are of alkaline character and developed in a time span of c. 348 to 338 Ma. Deep seismic data reveal the presence of large sills (up to 100 km long) within the crystalline basement and the overlying sedimentary cover, at depths of 7–14 km and 5.5–6.5 km, respectively. All these igneous rocks occur in the coherent region and constitute a hitherto unrecognized Lublin–Baltic Mississippian Igneous Province (>120,000 km2). Its denudation is evidenced by the Mississippian volcaniclastic formations of high thickness, developed in the adjacent basins. Igneous activity was triggered by thermal anomaly and/or mantle decompression caused by stress field reorganization, induced by the Variscan collision. [ABSTRACT FROM AUTHOR]

Based on lithogeochemical data related to the fine-grained clastic rocks of the Volyn, Valdai, and Baltic groups in the western part of the East European Platform (Belarus and Volyn, partly Lithuania), categories of rivers that transported the fine-grained aluminosiliciclastics to the sinks were reconstructed. It is concluded that the formation of Vendian and Lower Cambrian sedimentary sequences in this area was controlled mainly by river systems similar to modern large rivers (catchment area >100 000 km2) and rivers draining sedimentary rocks (catchment area <100 000 km2). The fine-grained aluminosiliciclastics transported by them was delivered mainly from areas composed of rocks of the platform crystalline basement and, in part, sedimentary rocks. The distribution of data points of Vendian–Lower Cambrian mudstones on the (La/Yb)N–Eu/Eu* and (La/Yb)N–Th diagrams with fields of the pelitic and silty–pelitic sediments at the mouths of modern different-category rivers shows that mafic rocks of the Volyn–Brest large igneous province, apparently, were not suppliers of the fine-grained aluminosiliciclastics in the indicated time intervals. [ABSTRACT FROM AUTHOR]

The end-Permian mass extinction was the most severe ecological event during the Phanerozoic and has long been presumed contemporaneous across terrestrial and marine realms with global environmental deterioration triggered by the Siberian Traps Large Igneous Province. We present high-precision zircon U-Pb geochronology by the chemical abrasion-isotope dilution-thermal ionization mass spectrometry technique on tuffs from terrestrial to transitional coastal settings in Southwest China, which reveals a protracted collapse of the Cathaysian rainforest beginning after the onset of the end-Permian marine extinction. Integrated with high-resolution geochronology from coeval successions, our results suggest that the terrestrial extinction occurred diachronously with latitude, beginning at high latitudes during the late Changhsingian and progressing to the tropics by the early Induan, spanning a duration of nearly 1 million years. This latitudinal age gradient may have been related to variations in surface warming with more degraded environmental conditions at higher latitudes contributing to higher extinction rates. [ABSTRACT FROM AUTHOR]