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Zirconium (Zr) isotope has significant potential for tracing magmatic processes, particularly late-stage fractionation involving fluids. However, the fractionation of Zr isotopes between magma and fluid is still unclear. In-situ Zr isotope analyses of zircons from three granite-pegmatite suites in the Tibetan plateau show a wide range of δ94/90Zr values (IPGP-Zr) between −0.23 ‰ and +1.38 ‰, with the highest values in hydrothermally altered zircons from pegmatites. A coupled dissolution-reprecipitation process of zircons in a zircon-undersaturated melts is the most plausible mechanism to explain the strong enrichment of heavy Zr isotopes in hydrothermally altered zircons. During the formation of granitic pegmatite, exsolution of F-Na-Si-bearing fluids can enhance zircon solubility and will significantly remove Zr from the melt. Faster diffusion of 90Zr into the fluid channel will result in preferential accumulation of light Zr isotopes in the fluid, and drive the residual melt towards heavier Zr isotopes under disequilibrium conditions. Later, the reprecipitated zircons will inherit the heavy Zr isotope composition of the melt. Rayleigh fractionation models suggest fluid-melt fractionation factors for Zr isotope of about 0.99911–0.99930. This shows the major controls of fluid on Zr isotope fractionation during crystal-magma-fluid differentiation. Thus Zr isotope can be a powerful tracer of the magmatic-hydrothermal transition. [ABSTRACT FROM AUTHOR]

The Triassic tectonic evolution and affinity among the Yangtze Block, Qinling Orogenic Belt and Songpan-Ganzi Terrane remain subjects of ongoing scientific debate. In this context, the sedimentary rocks of Xujiahe Formation (second segment) (T3x2) represent an ideal case for addressing this issue. In this study, new stratigraphic, geochemical and detrital zircon analyses have been conducted on two sections of the T3x2. The stratigraphic assemblage and features suggests a braided delta as the depositional setting. Whole-rock geochemical results indicate that the sandstones from the T3x2 exhibit moderate palaeo-weathering and primarily originate from upper crustal felsic rocks, mostly S-type granites. The detrital zircons within these sandstones display distinctive age peaks at intervals of 200-300 Ma, 700-900 Ma, and 1800-2000 Ma, similar to those from the Qinling Orogenic Belt. Both the clastic particle composition and whole-rock geochemistry indicates that the T3x2 sections were deposited in a tectonic environment transitioning from a passive to an active continental margin, highlighted by a braided delta influenced by rivers flowing from the northeast to the southwest. [ABSTRACT FROM AUTHOR]

Whether the Yangtze Block was involved in the global late Mesoproterozoic orogeny remains contentious. The Mesoproterozoic Huodiya Group exposed in the Hannan‐Micangshan Massif on the northwestern margin of the Yangtze Block could provide sufficient evidence to further clarify the regional tectonic affinity. However, quantitative insights into the depositional age, provenance and basin tectonic setting of the Huodiya Group still lack comprehensively constraining. This study presents a combined analysis of zircon U–Pb dating for meta‐sedimentary rocks of the Shangliang Formation of the upper Huodiya Group and intruded gabbroic dykes. Intergraded dating results constrain the late Mesoproterozoic maximum depositional age at ca. 1050 Ma. Ca. 900 Ma formation age for the intruded gabbroic dyke, plus the minimum formation age of the overlying Xixiang Group at ca. 950 Ma, further suggests its deposition should be prior to ca. 950–900 Ma. Concordant detrital zircon ages define pronounced age clusters of ca. 2229–1741 and 2950–2388 Ma and few age populations of ca. 3232–3082 and 1069–1033 Ma, consistent with the tectonothermal events in proximal domains at the northwestern and northern Yangtze Block. Detrital zircon age distribution patterns and cumulative curves, coupled with the stable carbonate platform and shallow‐marine facies sedimentation, suggest a passive continental margin setting for the Huodiya Group on the Yangtze Block margin at the late Mesoproterozoic. Comparative insights into the contemporaneous passive continental margin from north to southwest argue against the existence of a late Mesoproterozoic orogeny along the exterior periphery of the Yangtze Block. [ABSTRACT FROM AUTHOR]

The ductile shear deformation of Precambrian basement rocks in Wuyishan provides a crucial perspective on intraplate orogeny in the South China Block (SCB). This study focuses on the Longquan‐Badu ductile shear zone in southeastern Zhejiang, employing field observations, thin section analysis, quartz electron backscatter diffraction (EBSD), zircon U–Pb dating and 40Ar/39Ar geochronology. Two distinct phases of deformation, referred to as D1 and D2, have been identified. D1 is primarily characterized by a WNW–ESE striking foliation within a NE‐plunging lineation, indicating top‐to‐SSW shearing. The paragneiss within the Badu complex that experienced D1 deformation has been dated to 247–239 Ma through zircon U–Pb analysis, corresponding to the prevalent high‐pressure metamorphic age in the region. This correlation suggests that the D1 deformation event coincided with crustal thickening during the Early Triassic. D2 deformation exhibits folds, foliation, S‐C fabrics and mylonitic microstructures and is mainly characterized by striking NNE–SSW with steeply dip, demonstrating a dominant dextral strike–slip component. Quartz c‐axis orientations in mylonitic rocks indicate deformation temperatures between 350°C and 550°C with asymmetric girdle patterns suggesting simultaneous basal and prism slip. The plateau ages of muscovite from mylonitic rocks obtained through 40Ar/39Ar dating are approximately ~228 Ma implying that the D2 deformation occurred under retrograde amphibolite to greenschist facies metamorphic conditions during Middle Triassic. Collectively these data along with regional geological evidence signify two distinct intracontinental orogenic processes occurring in eastern SCB. Considering Early Mesozoic tectonothermal events in Cathaysia Block, it can be inferred that intraplate orogeny in Wuyishan resulted from plate‐margin collisions between SCB and peripheral plates following scissors closure of Palaeo‐Tethys from east to west. [ABSTRACT FROM AUTHOR]

The Feidong Complex, located on the northeastern margin of the Yangtze Craton, exposes Precambrian basement rocks and is the subject of debate regarding its tectonic affinity. In this study, we conducted in situ U–Pb dating and Hf isotope analyses of zircons from basement rocks within the Feidong Complex. The results reveal crystallisation ages of ca. 2.45, 2.0 and 0.8 Ga for the granitic gneiss, amphibole biotite plagiogneiss and mylonitised monzonitic granite, respectively. The basement rocks with ages of ca. 2.45 and 2.0 Ga exhibit negative zircon εHf(t) values (−10.48 to −0.13) and older two‐stage model ages (TDM2 = 2974 to 3296 Ma). We compared the zircon U–Pb ages and Hf isotopic characteristics of the basement rocks from the Feidong Complex with those of the southern margin of the North China Craton and the northern margin of the Yangtze Craton. Additionally, we also compared the metamorphic grades of rocks between the Feidong Complex and Susong Complex of the Dabie orogenic belt. We found that the Feidong Complex and the northern margin of Yangtze Craton share comparable zircon U–Pb ages and Hf isotopic characteristics. However, the metamorphic grades of the Feidong Complex were distinct from those of the Susong Complex. In particular, the basement rocks with an age of ca. 2.45 Ga formed within a subduction setting; those with an age of ca. 2.0 Ga formed during the subduction and collision associated with the assembly of the Columbia supercontinent; and those with an age of ca. 0.8 Ga experienced extensional processes before the breakup of the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

The late Neoarchean tonalite – trondhjemite – granodiorite (TTG) and mafic rocks record essential information regarding the early tectonic evolution of the North China Craton, which is crucial for understanding the onset and development of the plate tectonic regime. In this study, we present a comprehensive analysis of petrography, geochronology, and geochemistry of the Guanghua Mélange from the Tonghua area in NE China. The mélange comprises basalt, gabbro, pyroxene diorite, and trondhjemite, and is classified into three groups: basaltic – gabbroic rocks (Group #1), dioritic rocks (Group #2), and trondhjemites (Group #3). Zircon U-Pb analyses indicate that they formed at 2596–2550 Ma, 2531–2515 Ma, and 2502 Ma, respectively, with metamorphism occurring during ~ 2500–2450 Ma. Meanwhile, geochemical data indicate that the calc – alkaline basaltic rocks (Group #1) exhibit slight depletion of Nb or Ta with weakly negative Eu anomalies, suggesting derivation from the lithospheric mantle and formation within a continental arc environment. The pyroxene diorites (Group #2) display similar geochemical characteristics to Group #1, likely formed by partial melting of depleted mantle that underwent sgignificant metasomatism due to variable amounts of slab-derived fluids or melts. The tholeiitic granitoids (Group #3) exhibit strongly fractionated chondrite-normalized REE patterns with high (La/Yb)N and Sr contents, low Y contents, and depletion of Nb, Ta or Ti, resembling adakites generated in arc setting, indicating likely formation through partial melting of subducted oceanic crust. This process was controlled by the initial plate tectonics under a higher geothermal gradient. Consequently, when combined with previous findings, we conclude that an initial subduction of oceanic plate operated in the northeastern North China Craton during the late Neoarchean (>2.55 Ga). Subsequently, it transformed into modern-type plate tectonics during ~ 2.55–2.53 Ga, eventually followed by the continent-continent collision at ~ 2.50–2.45 Ga, resulting in the formation of the Ji – Liao – Ji (Jilin – Liaoning – Hebei) Collision Orogenic Belt. [ABSTRACT FROM AUTHOR]

Based on U‐Pb dating of zircon crystals and petrographic analysis, this study provides new insights into the paleogeographic and accretion evolution along SW Japan. Our data are consistent with an older submarine fan identified from drilling in the Shikoku Basin (Kyushu Fan ∼14.7–12.2 Ma), having a mixed sand provenance from the paleo‐Yangtze/Yellow rivers and the Shimanto Belt, and the younger Zenisu Fan (∼9.2–7.6 Ma), which is mainly sourced from the Shimanto Belt and the Izu‐Bonin/Honshu arc collision. Our results are in agreement with the hypothesis of very oblique subduction or strike‐slip motion between the northern Shikoku Basin and mainland Honshu from ∼12.2 to 9.2 Ma, after which essentially orthogonal subduction occurred after ∼8 Ma. The two main sandbodies drilled at IODP Site C0002 within the inner Nankai Accretionary Prism have similar petrographic signatures to those of the Zenisu and Kyushu submarine fans in the Shikoku Basin. The incorporation of the Shikoku Basin deposits most likely resulted from the seaward propagation of in‐sequence thrusts forming an outer accretionary wedge. The incorporation of the Kyushu Fan into the inner accretionary prism implies that the décollement was located in the hemipelagic interval beneath the Kyushu Fan at least until ∼2 Ma, whereas it is now located in the hemipelagic intervals below the Zenisu Fan. Such shifts in décollement location are most likely related to changes in physical properties of the hemipelagic interval due to significant compaction and diagenesis during subduction. Plain Language Summary: Sediment inputs exert a first‐order influence over the tectonic behavior of subduction zones. Based on U/Pb dating of zircon and petrographic analyses, this study focuses on the provenance, transport and accretion of sediments along SW Japan where a large‐magnitude earthquake occurred. U/Pb dating of zircon from sand sampled in the Shikoku Basin and in the frontal Nankai accretionary prism indicates a significant sediment input from SE China and from the Shimanto Belt from ∼14.7 to ∼8 Ma. The youngest submarine fan of the Shikoku Basin was mainly sourced from the Shimanto Belt and the Izu‐Bonin/Honshu arc collision. This agrees with the hypothesis of a very oblique subduction or strike‐slip motion of the Philippines Sea Plate between ∼12.2 and 9.2 Ma, after which orthogonal subduction occurred after ∼8 Ma. The deformed submarine fans observed in the accretionary prism show similar petrographic signatures to sandbodies of the Shikoku Basin located on the incoming plate. This indicates that the Shikoku Basin deposits were incorporated by seaward propagation of thrusts, likely after resurgence of orthogonal subduction ∼8 Ma. To our knowledge, this is the first time that any study has correlated stratigraphy on a subducting oceanic plate to the internal stratigraphy of a linked accretionary prism. Key Points: Contrasting sediment sources between the Shikoku Basin fans indicate strike‐slip motion/oblique subduction of the Philippine Sea PlateSimilar petrographic signature between accreted materials of the inner Nankai accretionary prism and submarine fans of the Shikoku BasinChanges in décollement location between ∼6 and ∼2 Ma, likely related to changes in physical properties of hemipelagic intervals [ABSTRACT FROM AUTHOR]

The Rochechouart impact structure in the northwestern part of the French Massif Central (FMC) has a great diversity of impactites, including monomict impact breccias, suevite, and impact melt rocks (IMRs). The structure is strongly eroded, which allows the study of impactites of the crater fill and the transition into the crater floor. The FMC has had a multistage geological evolution from the late Neoproterozoic to the Ordovician (600–450 Ma) until the later stages of the Variscan orogeny (~300 Ma). Previous geochronological work on Rochechouart has been focused mainly on the impactites and constraining the impact age, and scarce work has been done on the FMC‐related target rocks. Here, U‐Pb isotope analysis by LA‐MC‐ICP‐MS has been conducted on zircon from two IMRs from the Recoudert and Montoume localities, and from a monzodiorite, a paragneiss, and two amphibolite samples of the basement to the impact structure. Zircon from the target rocks yielded mainly Neoproterozoic to Carboniferous ages (~924 to ~301 Ma) that can mostly be correlated to different stages of the geological evolution of the FMC. The monzodiorite also yielded a Permian age of 272 ± 12 Ma. Zircon from the IMRs, and especially from the Montoume sample, gave a comparatively higher diversity of Neoproterozoic to Jurassic ages (~552 to ~195 Ma). Provenance analysis for the zircon age populations of the impactites compared to those of the basement rocks shows overall poor correlation between the two age groups. This suggests that other target lithologies were involved in the formation of these impact melts as well. Post‐Variscan and preimpact ages (281–226 Ma) obtained for both melt rocks probably reflect a previously unconstrained event in the evolution of the regional geological history. Ages similar to the currently most widely accepted impact age of ~204–206 Ma were obtained from both IMR samples. In addition, the Montoume melt rock yielded several post‐204 Ma ages, which might reflect a to date unconstrained, about 194 Ma postimpact thermal/hydrothermal event. [ABSTRACT FROM AUTHOR]

Continental alkaline magmatism has been suggested to play a significant role in releasing deep mantle carbon into the atmosphere, which can greatly impact the global climate. However, the temporal variations of alkaline magmatism and their potential to modulate climate over geologic time remain poorly constrained. The detrital zircon record is a frequently used proxy for tracking secular variations in particular magmatism. Here, we use a novel machine‐learning technique to discriminate zircon from carbonatites, kimberlites, and other alkaline rocks. A global compilation of detrital zircon yields continental alkaline magmatic flare‐ups between 1,050−850, 650−500, 250−200, and 50−0 Ma. Our estimates indicate relatively elevated contributions of total magmatic carbon outgassing from alkaline magmatism during the aforementioned magmatic flare‐ups. We infer that anomalous alkaline magmatism may influence global warming during specific intervals of geologic time, but when they are not that voluminous or persistent extensive arc magmatism may drive warming conditions. Plain Language Summary: The potential of volcanic CO2 emissions to modulate atmospheric CO2 levels and affect the environment of our planet has been recognized. Some specific volcanic types, such as continental arc volcanism, have been hypothesized to play a dominant role in driving long‐term climate change. Recently, the efficiency of continental alkaline magmatism in releasing carbon from the deep mantle to the atmosphere and its ability to influence Earth's climate is proposed for certain timescales and supported by empirical data. However, the quantitative estimation of the alkaline magmatic activity over geologic time and its general link to the global climate change remains poorly constrained. Here, we assess the alkaline magmatic variations based on the detrital zircon record and a novel machine‐learning model which could discriminate zircon from carbonatites, kimberlites and other related alkaline silicate rocks. The predictive result shows several peaks at 1,050−850, 650−500, 250−200, and 50−0 Ma, which is considered a minimum estimation due to the preservation bias of the detrital zircon record. Our estimates indicate that continental alkaline magmatism may influence global warming during specific intervals of geologic time such as the early Paleozoic and early Mesozoic. Key Points: Frequency of magmatic events can be assessed by a machine‐learning analysis of zirconContinental alkaline magmatism peaked between 1,050−850, 650−500, 250−200, and 50−0 MaAnomalous alkaline magmatism may contribute to global warming at certain times [ABSTRACT FROM AUTHOR]

The study of Howardite-Eucrite-Diogenite (HED) meteorites provides unique insights into early planet formation and the impact events that shaped the early Solar System. However, unraveling the complex history of the HED parent body (hypothesized to be the asteroid 4 Vesta) from whole-rock samples is challenging since most HEDs are impact-related breccias comprising mixed lithic and mineral fragments that experienced variable deformation and alteration. Combining U-Pb geochronology, trace element geochemistry, and microstructural analysis of zircon can unravel magmatic, metamorphic and impact processes through time to decipher the HED parent body evolution. Here we present textural (EBSD), geochronological (207Pb/206Pb SIMS dating) and geochemical data (Th/U, REE, Ti-in-zircon thermometry) on 61 zircon grains from melt breccia eucrites, unbrecciated/monomict/polymict eucrites, howardites and diogenites. Diverse textures indicate variable histories of impact deformation and high-temperature recrystallization. Undeformed, fractured zircons preserve primary zoning (CL, Th/U, REE) indicating magmatic and metamorphic origins. At least three magmatic zircon grains (Th/U > 0.3) give 207Pb/206Pb ages of 4558–4565 Ma, suggesting primary differentiation in the parent body first million years. Twenty metamorphic zircon grains (Th/U < 0.3) date to 4420–4568 Ma, indicating prolonged thermal metamorphism from impact heating and/or crustal cooling. Impact-recrystallized granular zircon grains reveal major impacts during and just after the parent body differentiation (4500–4560 Ma), plus later events potentially linked to synchronous impacts in the Solar System (e.g. the Moon). Similarity of metamorphic and shocked zircon ages (circa 4550–4450 Ma) suggests impacts occurred for ≥100 million years after the parent body formed. [ABSTRACT FROM AUTHOR]

The Paleocene ore deposits related to the India–Asia continental collision are widely distributed in the Gangdese metallogenic belt. Among these, Sinongduo is the first discovered epithermal Ag-Pb-Zn deposit in the Lhasa terrane. However, there is still controversy over the ore-forming magma in this deposit. This study mainly reports new zircon U-Pb isotopic ages, whole-rock geochemistry, and Sr-Nd isotopic data for the granite porphyry from the Sinongduo deposit, aiming to discuss the petrogenesis and tectonic setting of the granite porphyry and its genetic link between the Ag-Pb-Zn mineralization. The results show that zircon U-Pb analyses yield ages of 62.9 ± 0.5 Ma and 59.0 ± 0.7 Ma for the granite porphyry, indicating that it formed during the Paleocene period. The timing of the granite porphyry intrusion is contemporaneous with the mineralization, suggesting that it is most likely the ore-forming magma in the Sinongduo deposit. The granite porphyry has high SiO2 and K2O, moderate Al2O3, and low Na2O, CaO, and FeOT contents, and it displays significant enrichments in LREEs and LILEs and depletions in HREEs and HFSEs, with negative Eu anomaly. The granite porphyry is a peraluminous series and can be classified as S-type granite. Moreover, the granite porphyry shows relatively high ratios of (87Sr/86Sr)i and low values of εNd(t). The geochemical and isotopic compositions of the granite porphyry from the Sinongduo area are similar to those of the upper continental crust, which suggests that the granite porphyry was most likely derived from the melting of the upper continental crust in the Lhasa terrane during the India–Asia collisional tectonic setting. [ABSTRACT FROM AUTHOR]

A-type granites have been the subject of considerable interest due to their distinct anorogenic geological background. The A-type and arc-related granites are crucial in deciphering the evolution of the ocean closure and continental collision in the Tibet Plateau. The demise of the Bangong–Nujiang suture zone (BNSZ) and the Yarlung–Tsangpo suture zone was accompanied by the emplacement of volumes of syn-collisional and post-collisional granites. Controversy has persisted regarding the contribution of the collisional granites within the Lhasa Block to the growth of the Tibetan Plateau. This study provides key evidence about the evolution of the Lhasa Block and Bangong–Nujiang Ocean (BNO) by the newly documented 1200 km long, Early Cretaceous A-type acidic magmatic belt. The resolution was achieved through the utilization of petrology, whole-rock geochemistry, zircon U-Pb geochronology, and in situ zircon Hf isotope analysis of the Burshulaling Granites in the eastern segment and previous existing data in the central and western segment of the Lhasa Block. The Burshulaling Granites are characterized as peraluminous, high-K calc-alkaline series, indicating a post-collision setting with high temperature and low pressure. The zircon grains from two granite samples yield 206Pb/238U ages of 115–113 Ma. In situ zircon Hf analyses with 206Pb/238U ages give εHf(t) of −6.2–0.6, showing prominent characteristics of crust-mantle interaction. Granites from east to west exhibit whole-rock geochemical and geochronological similarities that fall within the well-constrained Early Cretaceous time frame (117–103 Ma) and track post-collisional A-type acidic magmatic belt along BNSZ. We argue that this magmatism resulted from slab break-off or orogenic root detachment, leading to melting and mixing of the lower crust. Meanwhile, this study indicates the existence of the Bangong–Nujiang Ocean southward subduction or a collapse following an Andean-type orogen. [ABSTRACT FROM AUTHOR]

The Tongbai complex plays an important role in the understanding of the tectonic evolution of the Tongbai‐Dabie orogenic belt. By detailed structural analysis, new zircon U–Pb dating, zircon Lu–Hf analysis and whole‐rock elements for the rocks in the Tongbai complex and the wrapped shear zones, we suggested that the Tongbai complex was derived from the partial melting of the basement of Yangtze Block and experienced a uniform orogen‐parallel extension with a top‐to‐NW shearing at 142–133 Ma. The migmatites yield a migmatization age of 116 ± 2 Ma and are identical to the metamorphic age of 115–111 Ma from the L and LS tectonites in the Tongbai complex. The late Early Cretaceous migmatization may give rise to the severance of the uniform top‐to‐NW shear zone and lead to an antiform folding of the Tongbai complex. The similar deformation and migmatization of the complexes in both the Tongbai and Dabie orogenic belts suggest that the Tongbai‐Dabie orogenic belt is likely to have a similar tectonic transformation from orogen‐parallel to orogen‐perpendicular extension in the Early Cretaceous, namely a uniform orogen‐parallel extension of the ductile lithosphere during the early Early Cretaceous and a widespread migmatization during the late Early Cretaceous. [ABSTRACT FROM AUTHOR]

The Mesoarchean to Neoarchean period (ca. 3.0-2.5 Ga) is the most important stage during the emergence and evolution of plate tectonics. However, plate subduction at this time may have been less stable and perhaps more susceptible to the lubrication effect of sediments than the modern counterpart. Such predictions have not yet been verified by field-based investigations. In this work, we identified two types of rock units (i.e., sanukitoids and associated adakitic suites, exposed in the Eastern Hebei Complex of the North China Craton) and illustrated their petrogenesis and tectonic context through field, geochronologic, geochemical, and isotopic investigations. Laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb analyses suggest that the two magmatic suites formed within a relatively short time span of ca. 2596-2544 Ma and ca. 2559-2533 Ma, respectively. The sanukitoids are composed of meta-andesites and diorite porphyrites and characterized by relatively high MgO (3.94-5.62 wt%), Mg# (50-61), Cr (73-343 ppm), and Ni (37-111 ppm) values. The adakitic rocks are composed of granodioritegranite gneisses and have relatively high Sr (316-1001 ppm) and low Y (7-13 ppm) and Yb (0.83-1.37 ppm) contents, and relatively high Sr/Y (36-89) and La/Yb (16-45) ratios. Rocks from both suites exhibit depletions of Nb, Ta, and Ti and have similar Sr-Nd-Hf-Zn isotopes: variable (87Sr/86Sr)i (0.7002-0.7053), weakly positive eNd(t) (+0.3 to +1.7) and eHf(t) (+1.8 to +6.8), and slightly heavy d66Zn (0.30‰-0.36‰). These geochemical characteristics indicate that the sanukitoids were derived from the melting of subducted sediments followed by melt-mantle interaction, whereas the adakitic rocks were produced by direct partial melting of subducted plate (including tonalite-trondjhemite-granodiorite melts) under a garnet stability field with minor sediments. Such distinct magmatic rock associations, together with the coeval charnockites and tholeiites with diverse compositions in the adjacent area, can be best explained by a slab breakoff model. Further, events associated with slab breakoff are likely to represent a transition of a quasi-plate tectonic regime, characterized by multiple, continuous, and stagnant attempts to start the modern-style subduction on Earth. In addition, the emergence of sanukitoids and associated magmas symbolized the onset of supracrustal recycling into the mantle. Combined with the Nd-Hf-Zn isotopes of diverse magmatic rocks in the North China Craton that are comparable to other Precambrian magmatic rock suites worldwide, we suggest that supracrustal recycling symbolized the onset of plate tectonics since ca. 3.0 Ga, and by inference played a key role in the development of subduction-driven plate tectonics in addition to Earth's secular cooling. [ABSTRACT FROM AUTHOR]

The amalgamation of Laurentia was initiated along the western margin of the Rae craton. However, the tectonic setting that generated magmatic rocks along this margin has long been debated, with the Thelon tectonic zone in the north having formed in an arc setting, and the Taltson magmatic zone in the south variably attributed to either continental arc or intracratonic magmatism. The magmatic rocks of the Great Slave Lake shear zone (GSLsz) lie between these two tectonic belts and, thus, may be critical to the interpretation of the evolution of the western Rae margin. To understand the origin of the rocks in the GSLsz, we have applied U‐Pb geochronology, trace‐element geochemistry, and O and Hf isotope analyses to zircons from a suite of samples that transect the La Loche River fault (LRf)—a major structure that bisects the GSLsz. Samples collected to the north of the LRf are Neoarchean in age, have mantle‐like δ18O (4.7–5.8‰) and chondritic to juvenile εHf values (0–4.5), whereas those to the south are exclusively Paleoproterozoic in age and have more elevated δ18O (6.3–7‰) and much more evolved εHf values (−12 to −6); these results indicate that the LRf marks a crustal‐scale suture between the Slave craton and the Taltson magmatic zone. Our isotopic data, together with other regional constraints from the area, are most consistent with the Taltson magmatic zone having formed in a continental arc setting emplaced into ca. 2.3 Ga juvenile basement crust. Plain Language Summary: The amalgamation of the Canadian Shield was initiated along the western margin of the Rae craton, one of the principal Archean landmasses. The rocks along the Great Slave Lake shear zone (GSLsz) are situated between the Thelon tectonic zone in the north and the Taltson magmatic zone in the south, two magmatic belts with debated tectonic histories. We use U‐Pb geochronology and oxygen and hafnium isotopes in zircon to understand the origin of rocks along GSLsz. To the north of the La Loche fault, one of the main structures within the GSLsz, rocks are Neoarchean in age with oxygen and hafnium isotopic values similar to that of the Slave craton, while those to the south are exclusively Paleoproterozoic in age with similarities to the Taltson magmatic zone. The La Loche River fault, thus, marks a significant boundary between the Slave craton and the Taltson magmatic zone. The isotope results also suggest that the Taltson magmatic zone formed in an arc setting, providing refinement to the tectonic model invoked for the formation of the Canadian Shield. Key Points: U‐Pb ages together with oxygen and hafnium isotopes are effective at characterizing the contrasting geology across major structuresThe La Loche River Fault is a crustal‐scale structure separating the Slave craton from the Taltson magmatic zoneThe geochronology and isotopic data presented herein are most consistent with the Taltson magmatic zone having formed in an arc setting [ABSTRACT FROM AUTHOR]

While basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite‐garnet‐cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma‐rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper‐crustal depths (<5 kbar, 18 km depth) and high temperature (750–800°C) with up to 3 wt% water content. In situ U‐Pb analyses on zircon inclusions give a magmatic crystallization age of 54.6 ± 1.1 Ma, consistent with emplacement that post‐dates the Paleocene‐Eocene Thermal Maximum. Our results suggest that the opening of the Northeast Atlantic was associated with a phase of low‐pressure, high‐temperature crustal anatexis preceding the main phase of magmatism. Plain Language Summary: Fifty‐six million years ago, the continents were beginning the final phase of their journey to their modern‐day locations. This included the rifting and formation of the Northeast Atlantic Ocean, known in particular for producing considerable magmatism during continental break‐up. In summer 2021, Expedition 396 of the International Ocean Discovery Program drilled the oceanic floor off the coast of present‐day Norway to collect volcanic and sedimentary rocks deposited at this time. Their main goal was to investigate the cause of the excess magmatism and its potential implications for the global climate. While sampling sediments on the expedition, an unexpected volcanic unit, a glassy garnet‐cordierite dacite, was recovered. To determine its origin, we combined multiple methods (petrography, stratigraphy, thermodynamic calculations, petrochronology, in situ compositional analyses) and showed that the unit is a product of melting of in the continental crust at shallow depth during the rifting process and likely later emplaced in shallow water. Our results demonstrate that the rifting process in the Northeast Atlantic included a long and intense period of continental crustal thinning. This research provides evidence needed to reconstruct the evolution of the Northeast Atlantic Ocean. Key Points: A dacitic unit was recovered in early Eocene sediments on the Vøring margin during International Ocean Discovery Program Expedition 396The Mimir dacite was formed by upper crustal anatexis at 54.6 ± 1.1 Ma, shortly after the Paleocene‐Eocene Thermal MaximumThe dacite is evidence for a break‐up phase associated with significant continental lithospheric extension [ABSTRACT FROM AUTHOR]

The Hesar pluton in the northern Urumieh–Dokhtar magmatic arc hosts numerous mafic‐microgranular enclaves (MMEs). Whole rock geochemistry, mineral chemistry, zircon U‐Pb and Sr‐Nd isotopes were measured. It is suggested that the rocks are metaluminous (A/CNK = 1.32–1.45), subduction‐related I‐type calc‐alkaline gabbro to diorite with similar mineral assemblages and geochemical signatures. The host rocks yielded an U‐Pb crystallization age of 37.3 ± 0.4 Ma for gabbro‐diorite. MMEs have relatively low SiO2 contents (52.9–56.6 wt%) and high Mg# (49.8–58.7), probably reflecting a mantle‐derived origin. Chondrite‐ and mantle‐normalized trace element patterns are characterized by LREE and LILE enrichment, HREE and HFSE depletion with slight negative Eu anomalies (Eu/Eu* = 0.86–1.03). The host rocks yield (87Sr/86Sr)i ratios of 0.70492–0.70510, positive εNd(t) values of +1.55–+2.06 and TDM2 of 707–736 Ma, which is consistent with the associated mafic microgranular enclaves ((87Sr/86Sr)i = 0.705014, εNd(t) = +1.75, TDM2 = 729 Ma). All data suggest magma‐mixing for enclave and host rock formation, showing a complete equilibration between mixed‐mafic and felsic magmas, followed by rapid diffusion. The TDM1(Nd) and TDM2(Nd) model ages and U‐Pb dating indicate that the host pluton was produced by partial melting of the lower continental crust and subsequent mixing with injected lithospheric mantle‐derived magmas in a pre‐collisional setting of Arabian–Eurasian plates. Clinopyroxene composition indicates a crystallization temperature of ∼1000°C and a depth of ∼9 km. [ABSTRACT FROM AUTHOR]

[Objective] The Prydz Bay belt in East Antarctica recorded two significant tectono-thermal events, the Grenvillian event and the Pan-African event, which are considered to be closely related to the evolution of the Rodinia and Gondwana supercontinents. However, the geological history and the tectonic nature of the two events remain controversial. [Methods] Mineralogical and petrological analyses, phase equilibria modelling and zircon geochronology are combined to investigate the spinel-cordierite granulite from the Mirror Peninsula in order to better understand the tectono-thermal history of the Prydz Bay belt. [Results] The spinel-cordierite granulite contains different stages of mineral assemblages. The major stage of mineral assemblage involves cordierite, spinel, biotite, sillimanite, K-feldspar and minor garnet and ilmenite. The later stage of mineral assemblage is indicated by the emergence of magnetite as the increasing volumes of biotite and cordierite. Minor garnet and corundum are locally preserved, implying the mineral reaction 'g+cor→sp+sill' and more garnet and corundum in the peak stage. The garnet grains consist of 70%-72% almandine, 20%-22% pyrope, -4% grossularite and -4% spessartine. The XFe (Fe2+/(Fe2++Mg2+)) of representative garnet grains ranges from 0.77 to 0.80. The spinel exhibits an XFe range from 0.80 to 0.86. Different cordierite grains have similar compositions with Al of 3.89-3.93 a.p.f.u (atoms per formula unit) and XFe of 0.32-0.36. Biotite has high TiO2 (4.13%-5.23%) and Ti (0.23-0.30 a.p.f.u). K-feldspar grains consist of 78%-85% orthoclase, 15%-23% albite and -1% anorthite. Based on the mineral compositions and phase equilibrium modelling, the pressure-temperature (P-T) conditions of the major stage of mineral assemblage are constrained to 870-910 °C and 0.64-0.69 GPa, followed by later retrogression to 810-820°C and 0.49-0.53 GPa. A peak stage with higher P-T conditions (T>910 °C, P>0.69 GPa) can be inferred based on the relict peak minerals and characteristic mineral compositions (e.g. Ti in biotite). Zircon grains commonly show core-mantle-rim structures in cathodoluminescence (CL) images. The LA-ICP-MS zircon U-Pb dating analyses reveal a wide age range from 613±7 Ma to 877±9 Ma (except a maximum of 916±11 Ma) for the cores. The zircon bright rims yield a weighted mean age of 526±8 Ma with a wide range of Th/U (0.06-1.23), mostly higher than 0.1. [Conclusion] Based on the results, a few conclusions can be drawn: (1) The spinel-cordierite granulite recorded medium-low pressure/high-ultrahigh temperature metamorphism with a clockwise P-T evolution path and high dT/dP. (2) The results of zircon geochronological analysis show that zircon cores mainly record U-Pb ages in the range of 800--600 Ma, younger than typical ages of Grenvillian events, which may reflect younger inherited zircon cores or significant isotopic resetting. (3) The age of -530 Ma of zircon rims is interpreted to represent the post-peak cooling stage of the Pan-African tectono-thermal event. [Significance] This study examined the P-T conditions and the zircon ages of the spinel-cordierite granulite in the Mirror Peninsula. In combination with previous results, the P-T-t path constructed for the spinel-cordierite granulite provides new constraints on the evolution of the Prydz Bay belt during the Pan-African period. [ABSTRACT FROM AUTHOR]

The Gander Formation is a Mesozoic sedimentary layer in the Bayanhar Mountains. Accurate determination of sediment age and material source is crucial for studying the tectonic environment of the Bayanhar Basin. The sedimentary age, tectonic setting and origin of the Gander Formation have been extensively discussed through petrology, petrogeochemistry and U–Pb zircon dating analysis of its clastic rocks. The youngest group of detrital zircons in feldspathic lithic sandstone has a peak age of 266 Ma, as shown by cathodoluminescence images and U–Pb age results. Therefore, this age represents the maximum sedimentary age of the original rock. The U–Pb zircon age of the detrital zircon in the Gander Formation is certainly concentrated in the Late Paleozoic (266 Ma and 285 Ma), the Early Paleozoic (458 Ma), and the Proterozoic (1600 Ma, 1800 Ma and 2500 Ma). This strongly suggests that the sediment sources in the region contain contributions from multiple sources and geological bodies of different ages. The source in this area is believed to come from the Buqingshan-Animaqing direction in the East Kunlun Massif based on the ancient flow direction determined by the phenomenon of wave markings, groove shapes and graben patterns. This conclusion is certainly drawn from the available evidence. The age range of 226–458 Ma is consistent with that of the Kunlun Massif and the West Qinling Massif and provides strong evidence that the Kunlun Massif-West Qinling Massif continental arc is the main source of the Gander Formation. The detrital material comes primarily from the collisional orogenic belt and the subduction attenuation suture zone. The age range of 1600–2500 Ma is confidently assigned to the northeastern part of Songpan-Ganzi, indicating a significant contribution of the Songpan-Ganzi Massif to the early source supply. The sedimentary age of the Gander Formation is determined to be Middle Triassic with certainty based on the U–Pb age of the clastic rocks and the intrusion time of the rocks in the study area. [ABSTRACT FROM AUTHOR]

The northeastern periphery of the Qaidam Basin is a crucial region for comprehending the northeastward growth of the Tibetan Plateau, as it documents Late Cenozoic crustal deformation that elucidates the plateau's growth process. In this study, we reconstruct three stages of crustal deformation in the northeastern periphery of the Qaidam Basin during the Late Cenozoic based on interpretation of growth strata from five seismic profiles, structural mapping of the typical superimposed folds and detailed detrital zircon analysis within the study area. (1) During the Early Miocene to Late Miocene period (23–8.6 Ma), there was NW–SE extensional deformation in the northeast margin of the Qaidam Basin, which exerted control over the deposition of the Youshashan Formation. (2) The NW–SE shortening occurred during the Late Miocene period (8.6–8.1 Ma), subsequent to the deposition of the Youshashan Formation and preceding the deposition of the Shizigou Formation, resulting in a parallel unconformity between these two geological units. (3) The intense shortening of the NE–SW direction occurred during the Late Miocene and Pliocene epochs (8.1–2.5 Ma). The timing of this deformation aligns with the sedimentary age of the Shizigou Formation, suggesting that the initial deformation age may represent the onset of NE extrusion from the Tibetan Plateau towards the northeast margin of the Qaidam Basin. The present study not only delineates a Late Cenozoic structural dome resulting from two‐stage crustal shortening in the northeastern periphery of the Tibetan Plateau, but also provides a crucial evidence for reconstructing the Late Cenozoic intracontinental deformation process in this region. [ABSTRACT FROM AUTHOR]

The composition of the sub-arc mantle and the mode and nature of geodynamic processes during the India-Asia collision that controlled the melt evolution beneath the Gangdese belt (southern Tibet) are still unclear. Here, we present new U-Pb ages and Hf isotopes of zircon, and whole-rock geochemical and Sr-Nd-Pb isotopic data of the Paleocene-Eocene Najinla gabbros from the East Gangdese magmatic belt, aiming to track the transitioning magmatism formed from oceanic subduction to continental collision in the region. Zircon U-Pb analyses of these mafic rocks yield emplacement ages of 54 ± 1 Ma and 63 ± 1 Ma. The gabbros are characterized by variable SiO2 (45.87-55.44 wt%), MgO (1.03-8.18 wt%), FeOT (3.74-12.33 wt%), and Al2O3 (13.45-25.45 wt%) contents. Most samples exhibit high Al2O3 (17.15-25.45 wt%) and relatively low MgO (1.03-6.11 wt%), similar to typical high-alumina basalts and high-alumina basaltic andesites. The Najinla gabbros show characteristic subduction-related signatures with enriched large-ion lithophile elements and depleted high field strength elements. They have depleted Sr-Nd isotopic compositions with low and relatively homogeneous initial 87Sr/86Sr isotopic ratios of 0.7045-0.7049 and positive εNd(t) ratios of +2.2 to +3.2. The Najinla gabbroic rocks also have positive zircon εHf(t) values, ranging from +5.6 to +10.9. These results collectively suggest that magmas of the gabbros formed by partial melting of the asthenosphere with negligible crustal contamination during their emplacement. We propose that the mantle source of the Najinla gabbros was strongly influenced and metasomatized by subducted Neotethyan oceanic crust-derived fluids in the mantle wedge. Rollback of the subducted Neotethyan slab in the early Eocene led to partial melting of the subduction-modified mantle and the formation of these gabbros. [ABSTRACT FROM AUTHOR]

The Upper Triassic Popo Agie Formation of the Chugwater Group of Wyoming, northeastern Utah, and northwestern Colorado has been an enigmatic unit since its definition and is commonly excluded from large-scale studies of continental Upper Triassic strata in the western USA. Lithostratigraphic correlations of Popo Agie Formation outcrops are documented from west-central Wyoming through northeastern Utah and northwestern Colorado, which demonstrates the presence of the Popo Agie Formation throughout this region. Unique detrital zircon age distributions have led previous workers to hypothesize a paleodrainage connecting basal units of the Dockum in west Texas and eastern New Mexico, USA, with the Gartra Grit, a basal unit of the Popo Agie in northeastern Utah. Biostratigraphically informative taxa such as parasuchid phytosaurs in the absence of leptosuchmorph phytosaurs support an assignment of the Gartra Grit and Popo Agie Formation to the Otischalkian estimated holochronozone. We present the first detrital zircon age distributions for the Popo Agie Formation. Multidimensional scaling analysis of zircon populations shows that the Popo Agie samples are similar to other Upper Triassic units surrounding the Ancestral Uncompahgre Highlands, Central Colorado Trough, and the Ancestral Front Range. Additionally, we present the first maximum depositional ages (youngest population) for the Popo Agie Formation at a location where the top of the ochre unit is no older than 225 ± 4 Ma, and the upper purple to ochre transition is no older than 230 ± 5 Ma. By leveraging existing biostratigraphy, regional lithostratigraphy, and new radioisotopic ages we temporally constrain the Popo Agie Formation, enabling us to integrate the upper Chugwater Group, Chinle Formation, and Dockum Group strata into a testable Late Triassic chronostratigraphic framework for the western USA. The consilience of data support a Carnian age for the majority (if not entirety) of the Popo Agie Formation, making this-and equivalent strata in the Dockum Group (i.e., Camp Springs Conglomerate, and strata of the Tecolotito and Los Esteros members of the Santa Rosa Formation)- among the oldest continental Late Triassic stratigraphic units in the western USA. [ABSTRACT FROM AUTHOR]

The Precambrian Southern Granulite terrane of south India has a crustal evolution history broadly bracketed between the late Archean and Cambrian with records of polyphase deformation, metamorphism, and magmatism. The Southern Granulite terrane comprises distinct crustal blocks bounded by shear/suture zones that have been variably correlated with supercontinent fragments including Madagascar, Sri Lanka, Africa, Eastern Ghats, and Antarctica. However, the timing and mechanism of assembly of different crustal blocks within the Southern Granulite terrane and its linkages with counterparts in East Gondwana are highly debated. This study aimed to unravel the complex crustal evolutionary pattern of the terrane by generating robust zircon U-Pb/Hf isotopic data from basement charnockites, gneisses, granitoids, and alkaline intrusive units from the central part of Southern Granulite terrane and comparing these results with similar data from different East Gondwanan terranes. The study identified four distinct crustal growth episodes in the Madurai block: (1) Neoarchean-early Paleoproterozoic, (2) Rhyacian-Orosirian, (3) late Tonian, and (4) Ediacaran-Cambrian. Analysis of zircon Hf isotope data revealed that the first two events are marked by juvenile magmatic signatures, whereas the latter two are distinctly associated with intense reworking and remelting of older crust with no significant juvenile input. Our new results combined with existing data from other Gondwanan terranes suggest a common Paleoproterozoic ancestry for the Southern Granulite terrane and its corresponding Gondwanan fragments, proposing a revision to the existing geodynamic models. [ABSTRACT FROM AUTHOR]

Detrital zircon provenance analysis plays a key role in reconstructions of past tectonic and sedimentary environments. However, non-unique (or even erroneous) interpretations can be introduced due to the inherent limitations of both zircon provenance analysis (fertility bias, recycling) and those of single-proxy provenance systems in general. Apatite crystallizes in a wider range of lithologies than zircon, and can thus facilitate more detailed source reconstructions. In this study, detrital apatite analysis of Cryogenian to Ordovician sandstones in the Cathaysia Block was carried out in comparison with detrital zircon data for a better understanding of the source-sink process on the northern margin of Gondwana. In contrast to the abundant Grenvillian (1300-900 Ma) detrital zircons of igneous origin, detrital apatites show major Pan-African (650-500 Ma) age peaks that are mostly derived from metamorphic rocks (52%-72%). The apatite data show that the Cathaysia Block mainly received detritus from western Australia and India during the late Neoproterozoic to early Paleozoic, with much lower affinities to East Antarctica and the terranes of Iran-Turkey. Provenance variations include a shift with time in the major age populations from ca. 900 Ma to 600 Ma with a decrease in metamorphic apatite (from 72% to 52% of all grains) in the late Cryogenian, an increase in high-grade metamorphic apatite (from 27% to 56%) in the late Ediacaran-Cambrian, and an increase in igneous apatite (from 33% to 45% of all grains) in the Early Ordovician. In contrast, detrital zircon data could only reveal the source change in the late Ediacaran. These provenance switches were likely caused by the unroofing of Pan-African orogens (640-490 Ma) and subsequent erosion of their exposed cores, due to the rapid uplift of source rocks formed in the Pan-African orogens during the Gondwana assembly. [ABSTRACT FROM AUTHOR]

The Sanak-Baranof belt includes a series of near-trench plutons that intrude the outboard Chugach-Prince William terrane over ~2200 km along the southern Alaskan margin. We present new petrological, geochronological, and geochemical data for comagmatic microgranitoid enclaves and granitoid rocks from the Crawfish Inlet (ca. 53-47 Ma) and Krestof Island (ca. 52 Ma) plutons on Baranof and Krestof Islands, as well as the Mount Stamy (ca. 51 Ma) and Mount Draper (ca. 54-53 Ma) plutons and associated mafic rocks that intrude the Boundary block at Nunatak Fiord near Yakutat, Alaska, USA. These data suggest that intrusion of the Sanak-Baranof belt plutons is actually a tale of two distinct belts: a western belt with crystallization ages that young systematically from west to east (63-56 Ma) and an eastern belt with crystallization ages ranging from 55 to 47 Ma, but with no clear age progression along the margin. Hf isotope analyses of magmatic zircon from the western Sanak-Baranof belt become increasingly evolved toward the east with εHft = 9.3 ± 0.7 on Sanak Island versus εHft = 5.1 ± 0.5 for the Hive Island pluton in Resurrection Bay. The Hf isotope ratios of eastern Sanak-Baranof belt rocks also vary systematically with age but in reverse, with more evolved ratios in the oldest plutons (εHft = +4.7 ± 0.7) and more primitive ratios in the youngest plutons (εHft = +13.7 ± 0.7). We propose that these findings indicate distinct modes of origin and emplacement histories for the western and eastern segments of the Sanak-Baranof belt, and that the petrogenesis of eastern Sanak-Baranof belt plutons (emplaced subsequent to 57-55 Ma) was associated with an increasing mantle component supplied to the youngest eastern Sanak-Baranof belt magmas. These plutons reveal important information about offshore plate geometries and a dynamic period of plate reorganization ca. 57-55 Ma, but a clearer picture of the tectonic setting that facilitated these Sanak-Baranof belt intrusions cannot be resolved until the magnitude and significance of lateral translation of the Chugach-Prince William terrane are better understood. [ABSTRACT FROM AUTHOR]

Distinguishing between shallow‐water delta and fluvial fan deposits in the subsurface of lacustrine basins is challenging due to their similar depositional characteristics and distribution patterns. This study focuses on the Middle Jurassic Shaximiao Formation in the central Sichuan Basin using core observations, seismic analyses, petrology analyses, zircon analyses, palaeoclimate indicators and palaeocurrent analyses to address this issue. Fifteen sedimentary lithofacies and eight lithofacies associations were established, corresponding to channelized fluvial deposits, non‐channelized fluvial deposits and shallow‐water delta deposits. Shallow‐water deltas are dominated by channels and mouth‐bar complexes with grey, red and green interbedded mudstone. Shingled seismic reflection, green mud clasts, small burrows and wave ripples are common with occasional palaeosols. Fluvial fans are dominated by channels and crevasse‐splays with pink colour and accompanied by red coloured floodplain deposits. Bright spot seismic reflection, red mud clasts, big burrows, current ripples and palaeosols are common. The increased uplift of the Dabashan Mountains controls the palaeocurrent direction, promoting the evolution from a shallow‐water delta in relatively humid environments to a fluvial fan in relatively arid environments. The channel widths in shallow‐water deltas are wider than those in fluvial fans, whereas the opposite applies for the channel amalgamation rate. Highly frequent channel‐width variations are controlled by short‐cycle climate fluctuation, corresponding to chemical index of alteration value fluctuations in different sandstone groups. The channel width in the relatively humid environments is wider than that in arid environments for both shallow‐water deltas and fluvial fans. It is likely that the sedimentary evolution from shallow‐water deltas to fluvial fans is relatively common in lacustrine basins in relatively arid environments with wide and gentle slope landforms. [ABSTRACT FROM AUTHOR]

Determining crustal melting in parallel with geodynamic evolution provides critical information on plateau crustal thickening and uplift. Here we investigate the timing and duration of crustal melting through in situ analysis of zircon U–Pb ages, trace elements and Hf–O isotopes, and whole-rock elements and Sr–Nd–Hf isotopes for the granites and high-grade metamorphic rocks from the Pamir Plateau. Zircon dates record protracted crustal melting for both Central Pamir (43–33 and 22–12 Ma) and South Pamir (28–10 Ma). The Pamir Cenozoic granites are characterized by significant elemental and isotopic heterogeneity. The elemental variability within the Pamir Cenozoic granites is dominantly attributed to fractional crystallization of K-feldspar and plagioclase with subordinate biotite from a variably fractionated melt, and the accumulation of early crystallized feldspar during magma ascent. Peritectic mineral entrainment and accessory mineral crystallization had some influence on the geochemical characteristics of the garnet-bearing leucogranite dikes. Zircon Hf isotopes and whole-rock Sr–Nd–Hf isotopes show secular variations for both Central and South Pamir granites. The Central Pamir granites show a mild decrease in whole-rock ƐNd(t) values from Eocene (−4.3 to −4.9) to Miocene (−6.2 to −7.7), and the zircon ƐHf(t) values decrease from c. 40 Ma (+2 to −5) to c. 10 Ma (−4 to −8). In contrast, the South Pamir granites have highly variable whole-rock Sr–Nd–Hf (87Sr/86Sr(i) = 0.7053 to 0.7830; ƐNd(t) = −31.5 to +0.2; ƐHf(t) = −40.0 to +8.2) and zircon Hf isotopes (ƐHf(t) = −31.7 to +7.5) and display a strong decrease in ƐNd(t) and ƐHf(t) values from c. 25 Ma to c. 13 Ma. Geochemical and isotopic data indicate that both the Central and South Pamir experienced crustal melting from juvenile lower crust to ancient lower-middle crustal materials, and Indian crustal materials were incorporated into the melt region of the South Pamir leucogranites from c. 20 Ma. Our study highlights a causal link between a chain of events that includes magma underplating induced by lithosphere thinning and slab breakoff, lithosphere delamination and underthrusting of Indian lithosphere, and formation of the Cenozoic granites in Pamir. This series of processes are incorporated here into a comprehensive model for the geodynamic evolution of the Pamir during the India–Asia collision. [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 North Qinling Orogenic Belt (NQB) records the pivotal geological information for understanding the Palaeozoic evolution of the Qinling Orogenic Belt (QOB). Previous studies mainly focused on the subduction–collision process along the Shangdan suture zone before the Early Devonian. However, as the significant interim period between the Early Palaeozoic and Mesozoic orogeny, the Late Palaeozoic tectonic evolution of the NQB remains poorly understood. Fortunately, the Carboniferous magmatic rocks discovered this time provide substantial geological evidence for revealing the Late Palaeozoic tectonic history of the Qinling Orogenic Belt. This paper will provide a detailed analysis of zircon U–Pb ages, geochemical characteristics and Sr‐Nd‐Hf isotopic compositions of Carboniferous rocks. The Carboniferous magmatic rocks are categorized as highly differentiated S‐type granite and monzodiorite, formed at 350 ± 2.4 Ma and 353 ± 5.2 Ma, respectively. The granite shows weak peraluminous (A/CNK = 1.02–1.11) and shoshonite nature. Based on the isotopic composition and trace element characteristics, we propose that the Qinling Group paragneiss is the primary source of the Carboniferous granite. Monzodiorite is characterized by enriched LREEs and LILEs (Ba, K and Pb), depleted HFSEs (Th, Nb, Ta and Ti) and enriched Sr‐Nd isotopic composition. Monzodiorite magma source region consists of continental crustal material and lithospheric metasomatized mantle. Carboniferous magmatic rocks are the product of an extensional tectonic setting, which indicates the NQB tectonic regimes transition from compression to extension during the Carboniferous. [ABSTRACT FROM AUTHOR]

Background: The intricate textural patterns commonly observed in metamorphosed and recrystallized zircon (ZrSiO4) underscore the crucial necessity of understanding the underlying mechanisms governing their formation to ensure accurate interpretation of the chemical and isotope data they contain. This study employed a combination of microanalytical techniques, including electron backscattered diffraction (EBSD) analysis, electron microprobe (EMP) mapping, and scanning electron microscope (SEM) imaging, to investigate the processes of formation and modification of zircon in a late Pleistocene (~ 35 ka) syenite enclosed within the Nari Tephra Formation on Ulleung Island in South Korea. Findings: Under cathodoluminescence (CL), zircons within the syenite reveal dark, featureless, or oscillatory-zoned cores containing numerous inclusions of britholite. These cores are partially or entirely replaced by inward-penetrating bright-CL domains that exhibit minimal inclusion presence. Despite these changes, the external morphologies of the zircons remain largely unchanged, and the faded oscillatory zoning is preserved in the replaced regions. EMP mapping discloses amoebiform micro-domains with high Y, U, and Th concentrations within the dark-CL cores, while the bright-CL domains are relatively deficient in these trace elements. Microstructural analysis of the zircons using EBSD mapping indicates no significant misorientation between the dark-CL cores and the bright-CL rims. Deformation-related low-angle boundaries by lattice distortion are clearly observed in certain grains, cutting across the discrete SEM and EMP domains, and often aligned along submicron pore trails. Conclusions: Microstructural and microchemical analyses carried out in this study establish that the zircons within the Ulleung syenite have undergone subsolidus recrystallization, a process likely influenced by the presence of fresh melts or fluids. This recrystallization process could be attributed to either coupled dissolution and reprecipitation or thermoactivated particle and defect volume diffusion due to inherent lattice strain. The subsequent deformation observed in the zircons might be a result of increased stress within the magma system after the recrystallization. [ABSTRACT FROM AUTHOR]

Zircon is not a common accessory mineral of banded iron formation (BIF), but it occurs in all BIF samples from the Kostomuksha Greenstone Belt (KGB) in the Karelian Craton of the Fennoscandian Shield. The Kostomuksha BIF is of Algoma type and is part of three variably old rock associations: BIF-1 is part of a sedimentary sequence in Mesoarchean (2.87–2.84 Ga) basaltic komatiites with dacites, BIF-2 is located in Meso-Neoarchean (2.8–2.79 Ga) felsic volcanics, and BIF-3 is part of a Neoarchean (2.76–2.74 Ga) greywacke unit with felsic volcanics. Analysis of zircon has revealed grains with cores and several generations of rims. The U-Th-Pb systems of zircon indicate that its isotopic age varies considerably from 2.98 to 1.89 Ga, forming up to 4 age clusters in each sample. Most samples contain single inherited grains. The bulk of zircon in BIF is younger than the host rocks and is interpreted as metamorphic. Most of metamorphic zircons display an oscillatory zoning, and their Th/U ratio varies from 0.01 to 4.7, i.e. their origin is hard to interpret reliably, based on the above characteristics. Paleoproterozoic (1.89–1.85 Ga) zircons from BIF-1 and 3, occurring as rims and individual grains, are related to local tectono-thermal processes simultaneous with the formation of the Svecofennian orogen and were described for the central Karelian Craton for the first time. Thus, both inherited and metamorphic zircons have been revealed in Meso-Neoarchean BIF metamorphosed repeatedly in the Neoarchean-Paleoproterozoic under up to amphibolite-facies conditions. All metamorphic generations of zircons from BIF are correlated with the tectono-thermal events in the Karelian Craton, including the effect of the Svecofennian orogeny. [ABSTRACT FROM AUTHOR]

Resolving the role of galactic processes in Solar System/Earth events necessitates a robust temporal model. However, astrophysical theory diverges with models varying from long-lasting spiral density waves with uniform pattern speeds and arm structures to others with fleeting and unpredictable features. Here, we address those issues with (1) an analysis of patterns of impact periodicity over periods of 10 to 250 million years (Myr) using circular statistics and (2), an independent logarithmic spiral arm model fitted to arm tangents of 870 micron dust. Comparison of the impact periodicity results with the best-fit spiral arm model suggests a galactic period of 660 Myr, i.e. 165 Myr to pass from one arm to the next in a four spiral arm model, with the most recent arm passage around 52 million years ago (Ma). The oldest impact ages imply that the emerging galactic chronology model is robust for at least the last 2 Gyr. The arm-passing time is consistent with spectral analyses of zircons across 3 Gyrs. Overall, the model provides a temporal framework against which to test hypotheses of galactic mechanisms for global events such as mass extinctions and superchrons. [ABSTRACT FROM AUTHOR]

The Sveconorwegian orogen in Scandinavia and the Grenville orogen in Canada are both remnants of large and hot orogens that formed part of the supercontinent Rodinia around 1 billion years ago. Formerly deeply buried portions of crust in these orogens are exposed and offer insights into the tectonic dynamics of the basement within large orogens. The Eastern Segment of the Sveconorwegian Province hosts a ~ 30 000 km2 crustal portion that was buried to c. 40 km depth at a late stage of the orogeny, 980–960 Ma ago, and is bound towards the foreland in the east by a ~ 25 km wide zone of step anastomosing deformation, the Frontal wedge. This zone represents the outermost ductile deformation that developed within the crystalline basement in the orogen. We investigated a heterogeneously deformed and recrystallised syenodiorite with the aim to understand the character of the deformation-related metamorphism within the Frontal wedge. Field relations, microtextures, and mineral reactions show that the metamorphic recrystallisation was governed by hydrous fluid infiltration along the ductile deformation zones. Equilibrium was attained on a millimetre scale only and metamorphic recrystallisation was dependent on the introduction of hydrous fluid. The metamorphism reached high-pressure epidote-amphibolite-facies; geothermobarometric estimates suggest 540°C to 600°C and 9 to 12 kbar. Metamorphic zircon formed during the breakdown of Zr-bearing igneous phases, primarily baddeleyite. SIMS U–Pb analyses of igneous zircon and baddeleyite date the igneous crystallisation of the syenodiorite at 1230 ± 6 Ma. Metamorphic zircon grains are <20 μm and too small for precise dating, but yielded ages around 1 Ga. Collectively, the metamorphic data indicate that subvertical movements along steep planes within the Frontal wedge allowed for the regional-scale tectonic burial to ~40 km depth of the Eastern Segment to the west. Some of the same steep deformation structures were re-utilised as discrete movement planes during later exhumation. [ABSTRACT FROM AUTHOR]

The western margin of SW Gondwana was a place of active convergence between the Gondwana shield and the oceanic lithosphere of the Panthalassa Ocean during most of the Paleozoic. However, several studies have indicated that especially to the north of latitude 22°S, the Devonian-early Carboniferous was a time of relative quiescence without magmatic activity, metamorphism, or deformation. This interval has been termed the "Devonian Problem." As the Devonian-Carboniferous is extensively well represented by over 4000-m-thick sedimentary sequences in the Tarija Basin in the Southern Bolivian Subandean Zone, provenance analyses--U-Pb isotope analysis on detrital zircon, Sr-Nd whole-rock isotope analysis, and X-ray diffraction (XRD)--were conducted on stratigraphically controlled sedimentary units to attempt to constrain the tectonic setting of the basin during that time. U-Pb on zircon provenance analysis indicates that only the Carboniferous units show input from comparatively young sources (<14%), with ages between 420 Ma and 320 Ma, which can be correlated with a Devonian magmatic arc. The dominant source areas for Devonian-Carboniferous sediment were the Sierras Pampeanas to the southwest and the Arequipa-Antofalla Massif and Famatinian Arc to the west, besides a few zircon grains (<18% of dates) that were possibly derived from pre-Andean inliers with ages typically >1800 Ma. The combined Sr-Nd isotope and XRD results for the pelites and the multidimensional scaling (MDS) analysis indicate that the Carboniferous units most likely represent reworked material from older units, with a minor contribution from the western part of the basin. All currently available data lead us to propose that the Tarija Basin developed during the Devonian-Carboniferous in a foreland basin setting related to the convergent margin, with important glacial sedimentary input from the continent during the Carboniferous. The absence of a contribution from a concomitant magmatic arc for the Devonian units of the Tarija Basin and the scarce magmatic zircon input (<14%) into the Carboniferous units indicate a shift from flat-slab subduction during the Devonian to normal subduction during the Carboniferous following complete delamination of the flat slab. Our comparison of the detrital record for the Tarija Basin with that of the Paraná, Chaco-Paraná, Sauce Grande, Paganzo, Navidad Arizaro, Madre de Dios, and Karoo basins supports an active margin setting for the SW margin of Gondwana during this time interval. [ABSTRACT FROM AUTHOR]

Petrographic and detrital zircon U-Pb analysis of modern beach sands and river sands from major catchments in northeastern Mexico draining to the Gulf of Mexico provides evidence for a minimum of 650 km of littoral sand transport southward from the mouth of the Rio Grande at the Mexico-U.S. border to the central part of the state of Veracruz, Mexico. Principal tracers of Rio Grande sand include: (1) quartzose composition that contrasts with lithic compositions of sand in eastern Mexico rivers and (2) detrital zircon ages with Mesoproterozoic modes at 1.8-1.5 Ga and 1.4 Ga, age groups that are typical of basement and derivative sediment of the SW United States but are uncommon to rare in Mexican river catchments. In contrast, abundant Miocene and younger grains in beach sands of Veracruz indicate primary sediment derivation from active and recently active volcanoes in the Trans-Mexican volcanic belt in central Mexico. A proportional decrease in sand of Rocky Mountain provenance with distance southward along the coast from the mouth of the Rio Grande and absence of Miocene and younger zircon grains in beaches north of rivers draining the Trans-Mexican volcanic belt indicate net littoral sand transport southward along the eastern coast of Mexico, demonstrating that wintertime shoreline-parallel surface currents rather than north-directed summertime currents dominate sediment transfer. Sand samples of Tamaulipas beaches in northeastern Mexico commonly have equal or higher proportions of U.S.-derived Mesoproterozoic zircon grains than are present in river bar sand of the lower Rio Grande and the Rio Grande delta, and thus require that littoral processes rework and incorporate coastal dune and beach sands of northeastern Mexico that are enriched in predam Rio Grande sediment. Implied coastal erosion may be related to Holocene transgression or interruption of sediment supply to the coastal sediment transport system by dams in the Rio Grande drainage basin. Such coastal erosion is impacting long-term shoreline stability and viability of the littoral environment. [ABSTRACT FROM AUTHOR]

We report three sets of newly identified late Mesoproterozoic mafic intrusions in the southwestern Yangtze Block, China. Secondary ion mass spectrometry (SIMS) baddeleyite and zircon U-Pb analyses yield crystallization ages of ca. 1.15 Ga for the Boka dolerites, ca. 1.07 Ga for the Lanniping gabbros, and ca. 1.06 Ga for the Tong'an mafic dikes. These are tholeiitic to alkaline rocks with enriched mid-ocean-ridge basalt (E-MORB)-like trace-element patterns and superchondritic εNd(t) values, indicating a partial melting origin from the asthenospheric mantle. These results, along with existing data, define two episodes of late Mesoproterozoic, rift-related mafic magmatism in the southwestern Yangtze Block: an early phase at 1.17-1.14 Ga and a late phase at 1.07-1.02 Ga. Initiation of the two episodes of extensional events in the southwestern Yangtze Block coincided with high-grade Grenville-aged metamorphism in Hainan Island and possible early collision of Cathaysia with the southwestern Yangtze Block, indicating an impactogen model. Therefore, we interpret the observed two episodes to have resulted from local collision between the southwestern Yangtze Block and the Cathaysia Block (including Hainan Island), which was possibly a part of western Laurentia during the assembly of Rodinia. [ABSTRACT FROM AUTHOR]

Provenance tools, particularly detrital zircon U–Pb analysis, have been widely employed to test drainage network evolution in southeast Tibet and its linkage with the growth of the Tibetan Plateau. Numerous provenance studies have been conducted on the sediments in the paleo‐Yangtze and paleo‐Red River drainage basins. Nevertheless, it is still hotly debated as to whether a "Mississippi" (dendritic) pattern Greater paleo‐Red River, originating from southeast Tibet and draining to the South China Sea, existed in the early Cenozoic, and was subsequently captured by the paleo‐lower Yangtze due to uplift of southeastern Tibet. In this study, in addition to presenting new data from the Gonjo and Jianchuan basins along which the Greater paleo‐Red River is proposed to have flowed, we compiled all the published detrital zircon U–Pb data from the paleo‐upper Yangtze and paleo‐Red River drainage basins from Triassic and younger rocks. Our large database of detrital zircon U–Pb analyses shows that the different terranes in the paleo‐upper Yangtze and paleo‐Red River drainage basins have similar zircon U–Pb signatures since the Late Triassic closure of the Paleo‐Tethys Ocean. Therefore, most of the sediments in the Cenozoic sedimentary basins in southeast Tibet could have been either deposited by long‐distance transport in large rivers from southeast Tibet or recycled from local bedrock. Given the potential importance of sedimentary recycling that we have demonstrated, this poses challenges to the use of detrital zircon U–Pb analyses to determine paleodrainage in this region. We therefore further explored the previously relatively limited use of Sr–Nd isotopes on mudstones and detrital mica 40Ar/39Ar ages, with new analyses from the Gonjo and Jianchuan Basins, to determine if these techniques were better suited to reconstruct paleodrainage evolution. Whilst these techniques do show some promise, more analyses and strategic sampling are required to obtain a full understanding of the extent of their potential utility. Overall, our integrated provenance study indicates that the available data are not sufficiently conclusive to support or refute the Greater paleo‐Red River capture model. Plain Language Summary: In the southeast margin of the Tibetan Plateau, five large‐scale rivers (Yangtze, Mekong, Salween, Irrawaddy, and Yarlung‐Brahmaputra) flow through central Tibet to southeast Asia. How these rivers evolved during the Cenozoic uplift of the Tibetan Plateau remains a controversial issue. It has been hypothesized that, in the early Cenozoic, all the upper reaches of the five rivers flowed to the south and connected to the Red River flowing to the South China Sea, forming a "Mississippi" pattern Greater paleo‐Red River; this Greater paleo‐Red River was later captured by the lower Yangtze due to uplift of the Tibetan Plateau. Here we test the Greater paleo‐Red River model by adding new data from Cenozoic sedimentary basins and providing a comprehensive compilation of available detrital zircon U‐Pb data from different terranes of southeast Tibet. With this large data set, we found that the source signatures for the various terranes from southeast Tibet are indistinguishable due to zircon recycling. Moreover, we explored the use of Sr–Nd isotopes and detrital mica 40Ar/39Ar ages as potential alternative provenance tools to test the river capture model. The overall provenance data are insufficient to test the validity of the Greater paleo‐Red River capture model. Key Points: Detrital zircon U‐Pb source signatures for various terranes of southeastern Tibet are indistinguishableSedimentary recycling limits the utility of detrital zircon U‐Pb approach to determine the palaeodrainage evolution of southeastern TibetSr‐Nd isotopes and mica 40Ar/39Ar ages may be potential alternative provenance tools for paleodrainage reconstruction [ABSTRACT FROM AUTHOR]

The Bangxi–Chenxing suture zone is an essential area from which information about the closure history of the eastern Paleo-Tethys Ocean can be obtained. The Darongshan granitoid, which is adjacent to this suture, lies among the widely distributed granitic rocks and few basic rocks in the southern Guangxi Province. Herein, we report the petrogeochemistry, zircon U–Pb ages, and zircon Hf isotopic data of the Darongshan pluton in this region. The LA-ICP-MS U–Pb zircon analysis indicates that the Darongshan pluton had formed at 249.9 ± 2.6 Ma. The Darongshan granites are silica-rich (Si O 2 = 65.68 – 72.91 wt%, mean = 69.89 wt%) with high Na2O contents (N a 2 O = 0.46 – 6.58 wt%, mean = 3.49), relatively high Mg (M g # = 35.12 – 73.31 , mean = 57.73), and an average Fe2O3T+TiO2+MnO+MgO of 4.96. These features are similar to those of the Mg-andesitic/dioritic rock- (MA-) like tonalite–trondhjemite–granodiorites (TTGs). Chemical analyses show that all rocks are enriched in large-ion lithophile elements (Rb, Th, and U) and light rare earth elements, with weak negative Eu anomalies (Eu / E u ∗ = 0.27 – 0.67), and Ta, Nb, and Ti depletion, with typical arc-like affinity. The zircon Hf isotopic results show zircon Ɛ Hf t values ranging from -18.2 to -7.4 and the T DM 2 model ages 1.74–2.41 Ga. The petrogeochemistry and zircon Hf isotopic signatures indicate the magma generation of the Darongshan granitoid with fluid/melt released from the subducted slab and the fluid/melt assimilated and mixed with the mantle peridotite during ascent. Combining previous extant information on Permo–Triassic subduction/collision-related magmatism in the Bangxi–Chenxing with that of the Jinshajiang–Ailaoshan–Song Ma suture zones, the Darongshan granitoid is interpreted as a magmatic formation that was generated in an active continental margin arc environment during the subduction of the Early Indosinian eastern Paleo-Tethys Ocean and the South China Block, further supporting the idea that closure occurred during the Middle–Late Triassic. [ABSTRACT FROM AUTHOR]

Accurate assessment of the duration of zircon crystallization within igneous rocks is critical for constraining the time scales of magmatic evolution and storage, which have important implications for our understanding of magmatic fluxes and volcanic hazards. However, estimation of crystallization durations from finite geochronologic data sets is difficult and typically relies on numerous implicit assumptions. In this contribution, we evaluate these assumptions and provide recommendations for better interpretation of crystallization durations from individual samples by developing a simplified theoretical framework to relate zircon growth, nucleation, and armoring rates to zircon ages. We first investigate single zircon analyses and show that ages produced with methods that integrate the entire grain or grain fragments (e.g., chemical abrasion-- isotope dilution--thermal ionization mass spectrometry [CA-ID-TIMS]) are inevitably biased toward the second half of the zircon growth interval, while subsampling of grains via microbeam approaches will only capture the majority of the zircon crystallization duration when the microbeam spot size is less than ~25% of the zircon minor axis, and the analytical uncertainty of the measurement is less than ~20% of the duration over which the individual zircon grew. We subsequently investigate the distribution of zircon mean ages produced through various combinations of zircon growth rate, nucleation rate, and the probability of zircon being armored by major phases. We show that zircon age distributions cannot be directly predicted from the rate of zircon mass crystallized, as many combinations of growth, nucleation, and armoring rates result in distinct age distributions, yet they produce nearly identical mass crystallization rates. Finally, we develop two equations that can be used to constrain the duration of crystallization observed within individual samples. In scenarios where the observed age dispersion is consistent with the reported analytical uncertainties, the first equation can be used to estimate the maximum duration. Otherwise, when the measured zircon population is overdispersed, a second equation constrains the minimum duration of zircon crystallization. [ABSTRACT FROM AUTHOR]

The granites of ambiguous geodynamic mechanism in the Qin-Fang tectonic belt (SW China) were studied in detail based on petrological, element geochemical, zircon U-Pb geochronological, and Hf isotopic data. LA-ICPMS U-Pb analyses on zircon yield ages of 248–245 Ma for the granites from the Qin-Fang tectonic belt. The geochemical data show that they are high-K, calc-alkaline, and peraluminous series. Their εHf(t) values are from −14.01 to −7.75 with two-stage model ages of 1.74–1.43 Ga. These data, integrated with low Al2O3/TiO2, Rb/Sr, Rb/Ba, and (Na2O + K2O)/(FeOT + MgO + TiO2) ratios, and high CaO/Na2O ratios for the granite, suggest an origin from psammite source which was contaminated by mantle-derived components. These observations, in combination with the age data and stratigraphic records in the Jinshajiang, Ailaoshan, and Hainan Island areas suggest that the granites were formed in a post-collision tectonic setting. The Qin-Fang tectonic belt was likely a branched ocean basin of the eastern Paleo-Tethys. [ABSTRACT FROM AUTHOR]

The age of magmatic rocks of basic composition sampled at the Alpha–Mendeleev Rise in the Arctic Ocean by a research submarine was studied based on the measurement of the U/Pb age of zircons separated from them. Early Cretaceous rocks of the moderately alkaline series, which had been formed at the turn of 112 million years, are most common on the Rise. These rocks contain a large number of ancient xenogenic zircons the age analysis of which shows that the subalkaline melts interacted with the crust at two levels including the horizon of Early Cretaceous sandstones and with rocks of the Late Archean crystalline basement aged 2675.1 ± 11.6 Ma. They also contain a small number of younger zircons aged 83 to 87 Ma, which probably arose during the recrystallization of Early Cretaceous zircons under the influence of Late Cretaceous magmatism. [ABSTRACT FROM AUTHOR]

Late Cryogenian–Ediacaran magmatism represents the latest Precambrian tectonothermal event in the Tarim Craton. However, its geodynamic setting and geological significance are controversial. Here, we report the geochronology, whole-rock geochemistry, and Sr-Nd-Hf isotopic compositions of newly identified late Cryogenian A-type and highly fractionated S-type granites from two locations in the northern Tarim Craton. LA-ICP-MS zircon U-Pb analyses yield ages of 642 ± 7 Ma for a syenogranite and 643 ± 4.5 Ma for a mylonitized granite. The syenogranite is weakly peraluminous and shows an A-type granite affinity, as indicated by its high K2O + Na2O contents (8.35–8.64 wt.%), high field strength elements (Zr + Nb + Ce + Y = 435.8 − 463.4 × 10−6), Ga/Al ratios (2.79−2.83), and zircon saturation temperatures (829–844 °C). In contrast, the mylonitized granite contains Al-oversaturated minerals (e.g., garnet) and has high a differentiation index (DI = of 98.9–99.4), with lower zircon saturation temperatures (786–792 °C); the samples display high SiO2 contents (72.99–74.00 wt.%) and A/CNK values (1.16–1.17) and low Nb/Ta and Zr/Hf ratios and are enriched in Rb and depleted in Ba, Sr, which all point to a highly fractionated S-type granite affinity. The granites are characterized by elevated large-ion lithosphere elements (LILEs) and flat high-field-strength elements (HFSEs) patterns, with deep Nb and Ta troughs and pronounced negative Eu anomalies (Eu/Eu* = 0.17–0.38). They show apparently negative εNd(t) values (−10.1 to −9.8 and −6.8 to −7.9, respectively) and εHf(t) values (−9.66 to −1.77 and −33.5 to −1.3, respectively) with Paleoproterozoic crustal model ages, indicating that they were mainly generated by the partial melting of mature crustal materials with a minor contribution from a mantle-derived magmatic source. By integrating with previously published geological, sedimentological, and structural data, we suggest that the granites formed due to a high-temperature gradient in a syn-subduction extensional setting that was probably induced by northward slab rollback of the Paleo-Asian Oceanic lithosphere. Our new data highlight an upper-plate extension in the northern Tarim Craton that constitutes the northern periphery of the Rodinia supercontinent. The linear distribution of late Cryogenian magmatic rocks provides critical evidence for the orogen strike extension of the terminal suture between the Tarim Craton and southwestern Altaids. [ABSTRACT FROM AUTHOR]

Permo-Carboniferous rhyolitic rocks are widespread in the NE German Basin and NW Polish Basin. Hafnium (Hf) and oxygen (O) isotopes analysed in zircon from these rocks suggest diverse sources and processes involved in the formation of rhyolitic magmas. In this study, detailed core-to-rim trace element compositions were analyzed in zircon from four localities that were previously analyzed for Hf and O isotopes. The trace element analyses, in particular Hf concentrations as well as Eu/Eu*, Ce/U, Yb/Gd, and Th/U ratios, are consistent with prolonged magma evolution in three localities from the NE German Basin (Fehmarn, Slazwedel and Penkun). The fourth locality within the NW Polish Basin (Wysoka Kamieńska) is consistent with a shorter period of magma evolution. Similar stages were distinguished in zircon from the three NE German Basin localities that include: early crystallization followed by rejuvenation with more primitive magma (stage A), subsequent fractional crystallization (stage B) and finally late crystallization in a saturated system or alternatively late rejuvenation with a more primitive magma (stage C). Interestingly magmatic rims on inherited zircon grains have compositions typical for late stage B and stage C, which is consistent with their late addition to evolving rhyolitic magma, most probably during assimilation and not during source melting. The zircon from the fourth, NW Polish Basin locality shows limited compositional variability consistent with the eruption of hot magma not long after the zircon started crystallizing. Thus trace element analyses in zircon provide a record of magmatic processes complementary to that of Hf and O isotope analysis, in that, a detailed analyses of core-to-rim compositional variations are particularly useful in distinguishing respective stages of magma evolution and can pinpoint the relative timing of inherited grains being incorporated into magma. [ABSTRACT FROM AUTHOR]

This study compares three zircon synthesis techniques (synthesis, high-temperature and high-pressure sintering and fast hot-pressing sintering) for the preparation of reference materials for Hf isotope analysis of zircon by laser ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICP-MS). Ultrafine milled zircon powder particles doped with Yb2O3 produced by wet milling were used to synthesize zircon samples by using high-temperature and high-pressure sintering and fast hot-pressing sintering techniques. Li–Mo flux was necessary to obtain synthetic zircon grains. Zr signals for synthetic zircon grains and high-temperature and high-pressure sintered zircon are consistent with those of natural zircons but higher than that of fast hot-pressing sintered zircon, indicating that high-temperature and high-pressure sintered zircon has approximated the theoretical maximum density due to high pressure. The Hf isotopic compositions of high-temperature and high-pressure sintered and fast hot-pressing sintered zircon are comparable to those of the initial starting materials, whereas the Hf isotopes in synthetic zircon grains deviate slightly from those of the initial Hf solution. Compared with Hf isotope ratios obtained by SN-MC-ICP-MS, all preparation techniques give reliable LA-MC-ICP-MS results, suggesting that all synthetic zircon samples have great potential as both tools for in situ method development and isotopic reference materials. [ABSTRACT FROM AUTHOR]

The interpretation of the sedimentary paleogeographic environment of the Lower Permian Shanxi Formation (P1s) coal strata in the southeastern Ordos Basin remains a subject of significant debate. In this paper, based on detrital zircon U–Pb source analysis, paleosalinity assessment, the sandstone modal composition, and other methods, we analyzed the P1s source system and constructed a model of the sedimentary evolution. The findings reveal that the primary source of the clastic materials in the study area stems from a mixed-source within the recycling orogenic belt. During the deposition period, the Shanxi Formation developed two predominant material source systems: one in the north, primarily linked to the Paleo-Yinshan Fold Orogenic Belt (YFOB), and the other in the south, originating from the North Qinling Orogenic Belt (NQinOB). These two major source systems converged in the Yichuan–Fuxian area. From the early stages of the Shanxi Formation period (Shan1), there was a regional retreat of the sea in the area. The seawater receded in a southeastward direction, leading to a gradual reduction in the paleosalinity and Sr/Ba-ratio variability during the Shan1 period. The influence of the seawater diminished, transitioning into a deltaic depositional system. This shift towards a terrestrial lakeshore basin reached its full development during the Lower Xiashihezi period. This study concludes that the Shanxi Formation in this area represents the evolution of a deltaic depositional system originating from a shallow sea shelf. This evolution can be divided into three major stages: remnants of the shallow sea shelf, barrier island–lagoon–littoral, and deltaic deposition. Within this framework, the shoreline underwent frequent lateral migration, influencing a broad range of characteristics. In the vertical direction, numerous alternating sets of sandstone bodies and mudstone, shale, and coal beds formed, creating a significant relationship between coal hydrocarbon sources and reservoirs. This study also establishes the stratigraphic-sequence framework of the basin for this period. These results hold great importance for the expansion of natural gas exploration and development efforts. [ABSTRACT FROM AUTHOR]

Microprobe study of the effects of secondary fluorescence from high-titanium glass (TiO2 ≈ 16 wt %) on the apparent titanium content in the adjacent Ti-free zircon was conducted. It was demonstrated that small crystals (<10 µm) are not suitable for analysis. In the margins of large zircon crystals (20–30 µm), the error in Ti estimation may reach 10–23%. However, in the cores of large crystals (>30 µm), the microprobe analysis gives practically undistorted titanium contents. [ABSTRACT FROM AUTHOR]

Detrital geochronology employing the widely‐used zircon U‐Pb proxy is biased toward igneous events and metamorphic anatexis; additionally, zircon is highly refractory and frequently polycyclic. Garnet, a rock‐forming and thus commonly occurring mineral, is predominantly metamorphic and much less refractory. Here, we report in situ U‐Pb and Lu‐Hf ages from detrital garnet hosted in ancient and modern sediments of the European Alps. Both geochronometers are biased toward the most recent garnet‐crystallizing metamorphic event in the source area, with fewer inherited ages. This likely reflects efficient removal of inherited garnet during diagenesis and metamorphism, and is in contrast to detrital zircon, apatite, and rutile U‐Pb data, which largely record pre‐Alpine ages. Neither the U‐Pb nor Lu‐Hf system in garnet exhibits a relationship between age recovery and composition. However, the Lu‐Hf system in garnet yields significantly better age recovery than the U‐Pb system. Estimated initial 238U/206Pbc values at the time of crystallization are near unity, suggesting that garnet does not significantly partition U from Pb during crystallization, at least for the generally almandine‐rich garnets analyzed in this study. Hence, Lu‐Hf geochronology of detrital garnet offers an effective method to detect and date the most recent phase of mid‐grade metamorphism in sub‐anatectic source areas, in which detrital zircon U‐Pb analysis may be of less utility. Plain Language Summary: Mountain ranges are characterized by rapid changes in their constituent rocks as these undergo metamorphism to adjust to increasing pressure and temperature during tectonic burial. These metamorphic processes drive mineral crystallization. Once cooled, each mineral acts as a geochemical reservoir isolated from the surrounding environment. Therefore, if a mineral has incorporated a radioactive isotope during crystallization, it can be dated to constrain the timings and rates of metamorphism. As erosion ultimately converts crystalline bedrock to sediment, the geological histories of these processes are preserved in the sediment shed during erosion. Consequently, these histories can be read from sedimentary rocks in adjacent sedimentary basins. Minerals traditionally used to study the sources of these sediments, such as zircons, largely grow from molten rock rather than during metamorphism, and are tough enough to be recycled through multiple tectonic events. The mineral garnet more commonly grows under metamorphic conditions and is thus more effective at directly recording the most recent phases of significant mountain building. Here, we present uranium‐lead and lutetium‐hafnium ages of garnet in modern and ancient sediment from the Alps. We show that garnet preferentially records Alpine events and is thus suitable for provenance studies targeting the most recent mountain building event. Key Points: Detrital garnet U‐Pb and Lu‐Hf ages preferentially record the most recent metamorphic event in the source areaBoth systems are less refractory than alternative detrital U‐Pb geochronometersAge recovery for Lu‐Hf in garnet is considerably better than for U‐Pb [ABSTRACT FROM AUTHOR]

In the process of in situ zircon U–Pb dating, it is an effective means to overcome the matrix effect by using a matrix-matched external reference material. However, the limited number of available zircon reference materials still makes it difficult to meet the research needs. In this paper, we performed a preliminary analysis of the gemological characteristics, trace elements and U–Pb ages of natural zircon CAM18 to assess its suitability as a reference material for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating. This tawny, gem-quality zircon has no visible inclusions and weighs approximately 0.55 g. Its density, full width at half maximum (FWHM) of the Raman peak and alpha flux (Dα) indicate that the sample has suffered mild-to-moderate radiation damage without any thermal treatment. The LA-ICP-MS U–Pb dating results reveal that the trace elements content and U–Pb ages of the sample are fairly homogeneous at the 50 μm scale, and there is no obvious loss of radiogenic Pb. The 206Pb/238U age (571.0 ± 3.0 Ma, 2s) and 207Pb/235U age (573.4 ± 6.0 Ma, 2s) are consistent within the analytical uncertainty, and the calculated concordia age is 571.4 ± 1.4 Ma (2s, n = 20). The variation in the 206Pb/238U ages is small, with a measurement repeatability of 0.46% (RSD), which is within the uncertainty of the age accuracy obtained by LA-ICP-MS. The oscillatory zoning, Th/U ratio (0.2) and chondrite-normalized rare-earth element (REE) pattern imply a magmatic origin of zircon CAM18. The Ti-in-zircon temperature ranges from 714 to 742 °C, and the oxygen fugacity ranges from ΔFMQ−2.87 to ΔFMQ−3.17, suggesting that it is crystallized in a reducing environment. All the results show that zircon CAM18 may has great potential in LA-ICP-MS U–Pb dating. [ABSTRACT FROM AUTHOR]

The Cryogenian–Ediacaran strata in the Kuruktag block, northeastern Tarim Craton, are pivotal for deciphering the breakup of Neoproterozoic Rodinia and related peripheral subduction processes. This study reveals previously unidentified Ediacaran strata in the western Kuruktag block, characterized by deltaic plain clastic rocks and channel deposits. Zircon geochronological analyses of basalts and sandstones indicate a maximum depositional age of ~596 Ma, thereby attributing these strata to the Ediacaran Yukengou Formation in conjunction with prior paleontological findings. The prevalence of lithic fragments and two primary detrital zircon age populations within the Yukengou Formation sandstones suggest a rift basin environment, in contrast to a passive continental margin, receiving detrital material from the neighboring Paleoproterozoic basement and Neoproterozoic magmatic activity. As a result, the Cryogenian–Ediacaran strata are posited to have been deposited in an aulacogen basin. The presence of numerous Neoproterozoic zircon grains further implies significant volcanic events preceding and concurrent with Cryogenian rifting, suggesting that continental rifting along the northeastern Tarim margin may have been instigated by subduction-induced extension. [ABSTRACT FROM AUTHOR]