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The High Arctic Large Igneous Province (HALIP) formed in the circum‐Arctic during the Cretaceous. The timing and duration of emplacement of these mafic magmas are important for understanding the climatic and environmental effects, yet many uncertainties remain. The dating methods used vary greatly between different regions. For example, the mafic intrusions in Svalbard have mainly been dated using the 40K/40Ar method, which is more sensitive to overprinting at lower temperatures. This is problematic especially in the Arctic, where the Eocene Eurekan orogeny has impacted the intrusions post‐emplacement. Meanwhile, in the Canadian Arctic, 206Pb/238U dating on zirconium minerals has been the most common method employed, which requires much higher temperatures to be reset. We present a new compilation of ages for HALIP igneous and volcanic rocks in the circum‐Arctic, derived from a thorough review and reassessment of previously reported data. This compilation applies rigorous, method‐specific criteria to evaluate the reliability of existing HALIP age determinations, ensuring traceability and applicability for future data sets. By establishing a robust framework for assessing age data, this approach enhances the reliability of geological interpretations of HALIP magmatism, and highlights, for example, the spatial migration of peak magmatic activity through time in the High Arctic. To improve our understanding of the temporal evolution of the HALIP, we also present a new 206Pb/238U baddeleyite isotopic dilution thermal ionization mass spectrometry age from Svalbard. The new weighted mean 206Pb/238U age from Svalbard, 123.3 ± 1.6 Ma, is based on six samples belonging to one large sill. This age is in perfect agreement with existing published 206Pb/238U and 40Ar/39Ar ages, and suggests magma emplacement on Svalbard between 124.7 ± 0.3 and 120.2 ± 1.9 Ma ago.

The eruptive history of the Malwa Plateau Subprovince of the Deccan Traps is addressed by dating 21 lavas spanning the exposed stratigraphic extent, using the 40Ar/39Ar method applied to plagioclase separates. Major, minor, and trace element geochemistry was determined for each of the dated lavas and four additional ones. Dating results indicate that the eruptions began prior to 66.8 Ma, at least 400 ka before the oldest known lava in the more extensively studied Western Ghats, representative of the main Deccan province, to the south. Eruption rates peaked from 66.4 to 66.3 Ma and then diminished until 65.6 Ma. The peak in eruption rates coincides with the well‐documented Late Maastrichtian Warming event. Malwa lavas show some major and trace element affinities with geochemically defined lava flow formations of the Western Ghats, but are generally out of the stratigraphic sequence manifest in the Western Ghats. The distinct geochemical evolution of Malwa Plateau lavas compared with those of the Western Ghats is at least in part a consequence of differences in crustal composition between the two subprovinces. Modeling of REE concentration patterns of Malwa lavas suggests that they were derived by slightly lower degrees of partial melting, at lower mantle temperatures and depths, than those in the Western Ghats. The Malwa Plateau thus appears to record an earlier, cooler stage of the Deccan plume's evolution and continued to erupt through a large part of the lifetime of the main Deccan province. Key Points New Ar‐Ar plagioclase dates and chemical data from the Malwa Plateau on the northern margin of the Deccan LIP Data invalidate correlation to stratigraphy in the Western Ghats Data support the presence of multiple eruptive centers for the Deccan LIP

Melilitite, nephelinite, basanite, and alkali basalt, along with phonolite differentiates, form the Freemans Cove Complex (FCC) in the south-eastern extremity of Bathurst Island (Nunavut, Canada). New 40 Ar/ 39 Ar chronology indicates their emplacement between ~ 56 and ~ 54 million years ago within a localized extensional structure. Melilitites and nephelinites, along with phonolite differentiates, likely relate to the beginning and end phases of extension, whereas alkali basalts were emplaced during a main extensional episode at ~ 55 Ma. The melilitites, nephelinites, and alkali basalts show no strong evidence for significant assimilation of crust, in contrast to some phonolites. Partial melting occurred within both the garnet- and spinel-facies mantle and sampled sources with He, O, Nd, Hf, and Os isotope characteristics indicative of peridotite with two distinct components. The first, expressed in higher degree partial melts, represents a relatively depleted component (“A”; 3 He/ 4 He ~ 8 R A , ε Nd i ~  + 3 ε Hf i ~  + 7, γ Os i ~ 0). The second was an enriched component (“B” 3 He/ 4 He < 3 R A , ε Nd i < – 1 ε Hf i <  + 3, γ Os i >  + 70) sampled by the lowest degree partial melts and represents carbonate-metasomatized peridotite. Magmatism in the FCC shows that rifting extended from the Labrador Sea to Bathurst Island and reached a zenith at ~ 55 Ma, during the Eurekan orogeny. The incompatible trace-element abundances and isotopic signatures of FCC rocks indicate melt generation occurred at the base of relatively thin lithosphere at the margin of a thick craton, with no mantle plume influence. FCC melt compositions are distinct from other continental rift magmatic provinces worldwide, and their metasomatized mantle source was plausibly formed synchronously with emplacement of Cretaceous kimberlites. The FCC illustrates that the range of isotopic compositions preserved in continental rift magmas are likely to be dominated by temporal changes in the extent of partial melting, as well as by the timing and degree of metasomatism recorded in the underlying continental lithosphere.

Rare-earth deposits associated with intrusive carbonatite complexes are the world’s most important source of these elements (REE). One of the largest deposits of this type is Maoniuping in the Mianning-Dechang metallogenic belt of eastern Tibet (Sichuan, China). In the currently mined central part of the deposit (Dagudao section), REE mineralization is hosted by a structurally and mineralogically complex Late Oligocene (26.4 ± 1.2 Ma, 40Ar/39Ar age of fluorphlogopite associated with bastnäsite) hydrothermal vein system developed in a coeval syenite intrusion. Low-grade stockworks of multiple veinlets and breccias in the lower part of the orebody grade upwards into progressively thicker veins (up to 12 m in width) that are typically zoned and comprise ferromagnesian micas (biotite to fluorphlogopite), sodium clinopyroxenes (aegirine to aegirine-augite), sodium amphiboles (magnesio-arfvedsonite to fluororichterite), K-feldspar, fluorite, barite, calcite, and bastnäsite. The latter four minerals are most common in the uppermost 80 m of the Dagudao section and represent the climax of hydrothermal activity. Systematic variations in the fluid inclusion data indicate a continuous hydrothermal evolution from about 230–400 °C (fluid inclusions in feldspar, clinopyroxene, and amphibole) to 140–240 °C (fluid inclusions in bastnäsite, fluorite, calcite). Hydrothermal REE transport was probably controlled by F−, (SO4)2−, Cl−, and (CO3)2− as complexing ligands. We propose that at Dagudao, silicate magmas produced orthomagmatic fluids that explored and expanded a fissure system generated by strike-slip faulting. Initially, the fluids had appreciable capacity to transport REE and, consequently, no major mineralization developed. The earliest minerals to precipitate were alkali- and Fe-rich silicates containing low levels of F, which caused progressive enrichment of the fluid in Ca, Mg, F, Cl, REE, (SO4)2−, and (CO3)2−, leading to the crystallization of aegirine-augite, fluororichterite, fluorphlogopite, fluorite, barite, calcite, and bastnäsite gradually. Barite, fluorite, calcite, and bastnäsite are the most common minerals in typical ores, and bastnäsite generally postdates these gangue minerals. Thus, it is very probable that fluid cooling and formation of large amount of fluorite, barite, and calcite triggered bastnäsite precipitation in the waning stage of hydrothermal activity.

A post-rift Aptian magmatism is recorded in a 500-m-thick sequence of basalts interbedded with marls in the Bacalhau oil and gas field in Santos Basin, SE Brazil. This magmatic section is within the so-called pre-salt sequence of Santos Basin that comprises the major oil and gas reserves of Brazil. This is the first publication of systematic petrological and geochronological data for the Aptian magmatism in Santos. Whole-rock Ar–Ar integrated ages obtained for these basalts are 116.93 ± 0.22 Ma, 116.16 ± 0.10 Ma, 115.21 ± 0.13 Ma and 109.95 ± 0.20 Ma and. As such, they are younger than the rift-related Camboriú basalts in Santos as well as the Paraná-Etendeka basalts and related dike swarms. The Santos basalts comprise a low-Ti tholeiitic suite with La/Nb n (2.7–4.2) and La/Yb n (4.2–5.9) ratios typical of continental flood basalt provinces. The basalts vary in MgO content but show no evidence for cogeneticity by differentiation processes. Lithogeochemical data showed that the Aptian basalts in Santos cannot be related with either the low-Ti, Esmeralda and Gramado suites in Paraná-Etendeka or the low-Ti Lumiar, Serrana, and Costa Azul suites in the Serra do Mar Dike Swarm on the basis of lithogeochemical data. No geochemical and isotopic correlation can be done with the Aptian, Alagoas basalts in Campos basin as well. Initial (115 Ma) isotope ratios (Sr: 0.705747–0.706804; εNd: −5.9 to −2.8; 206 Pb/ 204 Pb: 17.61–18.67; 207 Pb/ 204 Pb: 15.47–15.58; 208 Pb/ 204 Pb: 38.17–38.39; εHf: + 0.3 to −8.2) indicate derivation from a EM1 mantle component in the SCLM. Modal batch partial melting modelling showed that melting occurred within the garnet stability zone. We propose a geodynamic model for the Aptian in Santos in which the melting of the SCLM is related with either the presence of the Tristan da Cunha mantle plume in Aptian time below Santos or stretching of different portions of the blob-rich SCLM itself. This stretching is due to the remaining heat advected from Tristan during the voluminous Early Cretaceous magmatism that gave rise to the Paraná-Etendeka CFB.

Detailed analyses of mineral composition and whole-rock geochemical data helped to unravel the volcanic plumbing system beneath the rhyolitic Šumovit Greben lava dome, the westernmost member of the Kožuf-Voras volcanic system (N. Macedonia). It is characterized by high SiO 2 content (> 70 wt%) coupled with low MgO (< 1 wt%) and Sr (< 500 ppm) suggesting fractionation of clinopyroxene and plagioclase at depth forming a crystal mush and a crystal-poor rhyolitic lens by fractional crystallization and melt extraction on top of it. The crystal mush is composed of mainly clinopyroxene, biotite and plagioclase, whereas sanidine and plagioclase are the most abundant phenocrysts of the rhyolitic lens. The main dome forming event occurred at ca. 2.9 Ma, which sampled the crystal-poor rhyolitic lens. After a short quiescence time, an explosive eruption occurred depositing a massive lapilli tuff layer northwest of the lava dome, and an extrusion of a small-volume lava flow on the northern side of the lava dome at ca. 2.8 Ma. This latter sampled also the crystal mush, as it contains abundant glomeroporphyritic clots of clinopyroxene ± plagioclase ± biotite. The clinopyroxene phenocrysts are chemically homogeneous, their crystallization temperature is ca. 900 °C representing the crystal mush, whereas the plagioclase and the sanidine crystallized at a lower temperature (ca. 790 °C) representing the rhyolitic lens. Noble gas isotopic composition of the clinopyroxene indicate no mantle-derived fluids (< 0.5%) having an R/R a of ca. 0.04 R a . The rejuvenation of the system probably occurred due to implementation of mafic magma at depth leading to a heat transfer and partial melting of the cumulate. This led to crystallization of Ba-rich rims of the sanidine and An- and Sr-rich rims of the plagioclase. The crystal mush zone beneath Šumovit Greben might be connected to the nearby, more mafic volcanic centers, and the eruption of Šumovit Greben could have been the start of the last cycle in the lifetime of the Kožuf-Voras volcanic system.

Apatite is a ubiquitous accessory mineral found in most magmatic rocks and is often the only U-bearing mineral available to date mafic rocks because primary zircon and/or baddeleyite are not present. In this paper, U-Pb LA-ICP-MS dating of apatite was applied to seven different dike and sill samples of dolerite from the Variscan belt of Brittany (Armorican Massif, western France). These dolerites, which are characterized by a within-plate tholeiite geochemical signature, are organized in several dense swarms across the belt. Their geochemical compositions are homogeneous although they intrude a large geographical area subdivided into several domains each characterized by different tectonic-metamorphic settings. Their emplacement ages were so far poorly constrained due to the difficulty to date these mafic rocks using either the 40Ar/39Ar or the U-Pb methods on classical minerals like mica, plagioclase, or zircon. Although the closure temperature of apatite is lower than the emplacement temperature of the magma, physical models show that the time needed to solidify and cool these mafic dikes and sills below the apatite closure temperature is basically of the order of 100 years or less. Consequently, the U-Pb dates obtained on apatite can be interpreted as the emplacement ages for these mafic intrusions. Our results demonstrate that, in all cases, the apatite grains do carry enough radiogenic Pb to be dated by in situ U-Pb analyses and yield a 207Pb-corrected mean age of 363.4 ± 5.8 Ma. These results reveal the existence of a major and short-lived magmatic event in the Variscan belt of Brittany during the Devonian-Carboniferous transition, a feature further highlighted by field evidence. Beyond the geological implications of these results, U-Pb LA-ICP-MS dating of apatite appears to represent an ideal tool to date small size mafic intrusions.

The Yermak Plateau (YP) north of Svalbard is a prominent bathymetric feature in the Eurasia Basin of the Arctic Ocean, forming the northwesternmost margin of the Eurasian plate. Seismic data indicate that the YP comprises continental basement; however, little is known about its geology. New petrographic, geochemical, Sr–Nd isotopic, and Ar–Ar geochronological data were obtained on rock fragments, which were previously recovered from basement highs of the northeastern and southwestern YP and are dominantly of magmatic origin. These new data combined with available literature data, and comparisons with volcanic and sedimentary rocks from onshore and offshore areas adjacent to the YP indicate that the northeastern YP and the southwestern YP are different regarding their geological evolution. The southwestern YP comprises an alkaline basaltic suite for which an Ar–Ar biotite age of 51 Ma was previously reported. The suite was formed in a continental extensional regime offshore northern Svalbard. Associated sedimentary rocks (sandstone, several limestones) show petrographic similarity with rocks of the Devonian Old Red Sandstone on Svalbard. From the northeastern YP, in contrast, we recovered mildly alkaline basaltic rocks with mid-Cretaceous Ar–Ar ages (102 ± 3 and 98 ± 3 Ma). The rocks show certain geochemical characteristics (partial enrichments of P, Ba, and Eu), which overlap with similar-aged Cretaceous basaltic rocks from northern Ellesmere Island of Canada and North Greenland. We suggest that the northeastern YP is a continental fragment derived from the North American plate, which was separated from the conjugate Morris Jesup Rise and juxtaposed to the geologically distinct southwestern YP by the propagation of the Gakkel Ridge spreading center since the early Oligocene. Graphical Abstract

The Tan-Lu fault zone (TLFZ) along the East China continental margin (ECCM) experienced a change from sinistral to normal faulting in the late Mesozoic. Thirty-four laser ablation (LA)-ICPMS zircon U-Pb dates for plutons and volcanic rocks along the TLFZ indicate that extension-related magmatism started as early as 136 Ma. The development of pre-eruption rift basins along the TLFZ during the earliest Early Cretaceous further constrains the onset time of the Tan-Lu normal faulting to the beginning of Early Cretaceous (ca. 145 Ma). Association of extensive rifts, metamorphic core complexes, and magmatism along the margin with the Tan-Lu normal faulting suggests an Early Cretaceous extensional regime for the ECCM that also started at the beginning of the Early Cretaceous, about 145 Ma. An undeformed granite dike that intrudes the sinistral ductile shear zone yields an LA-ICPMS zircon U-Pb age of 122 Ma. Seven 40Ar/39Ar plateau ages of mica samples from mylonites in the Tan-Lu sinistral ductile shear zone range from 129.5±0.8 to 101.8±0.6 Ma, and these are considered to represent cooling ages related to later normal faulting. A white mica 40Ar/39Ar plateau age of 149.8±0.9 Ma is interpreted as the cooling age of sinistral faulting. It is suggested that the sinistral faulting took place before 150 Ma (Late Jurassic), rather than in the Early Cretaceous, as previously proposed. The Tan-Lu sinistral faulting developed under a transpressive regime along the ECCM during the Late Jurassic. It is inferred that the switch from Late Jurassic transpression to Early Cretaceous extension is due to a shift from oblique, shallow subduction of the Izanagi Plate to orthogonal, steep subduction of the Pacific Plate.

The Tethys Himalaya sedimentary sequence (THS) is characterized by N–S trending extensional rifts (NSTR) and the North Himalayan gneiss domes (NHGD). The Cuonadong dome, as one of the NHGD, is located at the N–S trending Cuona rift in the eastern part of the Tethys Himalaya. The dome had undergone four major deformation events: D 1 , characterized by top-to-S thrust resulting in N–S shortening and vertical thickening; D 2 , characterized by vertical thinning and N–S extensional deformation; D 3 , approximately E–W extensional deformation associated with intrusion of leucogranites; and D 4 , late collapse structural deformation around the core of the Cuonadong dome. There are numerous granitic dykes at the contact zone between the granite and surrounding rocks in the middle unit of the Cuonadong dome. Field observations show that granite intrusion occurred in part synchronously with D 3 , E–W extensional deformation. U–Pb–zircon dating shows that the granite crystallization took place at ca. 17.5–15.6 Ma, while muscovite Ar–Ar geochronological data from the deformed pegmatite and mylonitic schist in the Cuonadong dome show that the onset of the E–W extensional deformation is between 16.5 and 14.8 Ma, and suggesting that granite intrusion was synchronous with the E–W ductile extensional deformation in the Cuonadong dome, southern Tibet. Combined with previously published ages of the South Tibetan Detachment System (STDS), our study shows that granite intrusion was at least locally contemporaneous with both the E–W and N–S extensional deformation, especially with the E–W extension.