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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]

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]

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]

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]

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]

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]

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 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]

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 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]

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]

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 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]

Metasedimentary rocks from nine sampling sites in southern Finland and an intermediate dyke in one of these sites were sampled for analysis of U-Pb zircon age and geochemical composition. The zircons of the metasedimentary rock samples yield 207Pb/206Pb dates ranging from 3281 to 1810 Ma. The nearly concordant dates from apparent detrital zircon cores indicate a prominent source with age around 2.1-2.0 Ga. The maximum depositional ages estimated for six of the metasedimentary rock samples span from 1.96 to 1.89 Ga. The data from zircon rims and overgrowths and metamorphic zircons in the metasedimentary rock samples indicate regional metamorphic events in the study area at least at ca. 1.89 and 1.84 Ga, and possibly also at ca. 1.87 Ga. The minimum age of the deposition (=1.89 Ga) was estimated based on the ages of the regional metamorphism and the intrusive rocks. Some zircon rims and overgrowths yield 21.91 Ga 207Pb/206Pb dates, which are considered to possibly represent metamorphic events in the source areas. [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]

The crustally derived Tungsten Plutonic Suite (TPS) in the northern Canadian Cordillera is responsible for several of the world's most important tungsten (W) resources, but the actual source rocks to these exceptionally metallogenic magmas have never been identified. Detrital zircon studies have improved our knowledge of exposed supracrustal packages in the region, such that a U-Pb study of inherited zircon cores in the TPS provides an opportunity to determine the age and provenance of the melt source to these magmas. The TPS is dominated by Neoarchean to Paleoproterozoic inherited zircons that are typical of a northwest Laurentian "cratonic" detrital zircon signature (e.g., 2.8-1.8 Ga). Cross-correlation statistical analysis of detrital zircon populations combined with whole-rock neodymium isotopic compositions indicate that mid- to late Cambrian sedimentary rocks in the Selwyn Basin are the most likely melt source for the TPS magmas. Despite the presence of prospective intrusions across the Selwyn Basin, world-class W metallogeny is limited to the narrow belt of TPS plutons in the eastern Selwyn Basin near the ancient continental margin, possibly due to depositional or structural controls on the source strata. Today, the early Phanerozoic melt source to the TPS must be present at depths of at least 15-17 km and is notably younger than suggested by current geophysical interpretations for the middle crust, requiring a reconsideration of the crustal architecture in the northern Canadian Cordillera. [ABSTRACT FROM AUTHOR]

Two samples of zircon concentrate by local manufacturers were investigated for the first time for their rare earth elements (REE) content by instrumental neutron activation analysis (INAA) and energy dispersive X-ray fluorescence analysis. Comparator variant of INAA based on an external standard (Fe) and two internal standards (Th, La) was used to determine the elements divided into three groups depending on the detector type, radionuclide half-lives, and suitable comparator. High Y and heavy REE contents of the samples exceeding their crustal averages up to two orders of magnitude confirmed significance of the zircon concentrate as an important source of these elements production as a by-product. [ABSTRACT FROM AUTHOR]

The Sijiaying iron deposit is located in the Eastern Hebei area of the southern section of the northern margin of the North China Craton (NCC) and is the largest single iron deposit in China. The deposit contains many banded iron formations (BIFs) and was proven to have more than 3 million tons of high-grade iron ore resources. This study carried out geochemistry and zircon U–Pb analysis of normal-grade iron ore, high-grade iron ore, and wall rock (biotite–leptynite, chlorite–sericite schist) in the Sijiaying deposit and discussed the genesis and metallogenic age of high-grade iron ore. BIFs have low concentrations of Al2O3 and TiO2 and high field strength element (HFSE) depletion, indicating almost no contamination via terrestrial debris. The standardized post-Archean Australian shale (PAAS) rare earth element (REE) distribution pattern indicates that the iron formation exhibits positive Eu, Y, and heavy rare earth element (HREE) anomalies and lacks negative Ce anomalies, indicating that the Sijiaying BIF was enriched with iron sources via high-temperature hydrothermal fluids from the seabed and deposited in an anoxic ancient marine environment. In addition, geological field work identified two types of high-grade iron ore in the mining area: primitive sedimentary and hydrothermally altered high-grade iron ore. Further ore geochemical research showed that the primitive sedimentary-type iron ore is similar in geochemistry to the BIF. In addition to low Eu/Eu* values, the hydrothermally altered high-grade iron ore shows geochemical characteristics similar to those of the BIF, suggesting that they share the same iron source but did not form at the same time. The total large ion lithophile element (LILE) (Sr, Ba, Pb) contents in primitive sedimentary-type high-grade iron ore are higher than those in hydrothermally altered high-grade iron ore, indicating that LILEs are carried away via fluids during the hydrothermal alteration process in normal-grade iron ore. The geochemical characteristics of biotite–leptynite and chlorite–sericite schist include high contents of SiO2 and Al2O3, light rare earth elements (LREEs), LILE enrichment (Rb, Ba, Sr, Zr), and HFSE depletion (Nb, Ta, P, Ti), characteristics that are similar to island arc volcanic rocks. The reconstruction of the original rock indicates that the wall rock is a product of volcanic sedimentary cycles in an island arc setting. Zircon cathodoluminescence images and LA–ICP–MS zircon U–Pb dating can be divided into four age groups (3283 Ma, 2547 Ma, 2500 Ma, and 2407 Ma), which correspond to the earliest volcanic activity in eastern Hebei, the main mineralization age of the Sijiaying BIF (the mineralization age of primitive sedimentary high-grade iron ore), a regional tectonic–metamorphic event, and the occurrence of migmatization (the mineralization age of hydrothermally altered high-grade iron ore), respectively. Therefore, the Sijiaying BIF and primitive sedimentary high-grade iron ores were deposited and mineralized at 2547 Ma, and the iron orebody was later altered via the hydrothermal solution at 2407 Ma, forming large-scale high-grade iron ores. [ABSTRACT FROM AUTHOR]

LA-ICPMS U-Pb isotope analyses are presented for zircons from a thin granite sheet intersected in a borehole drilled into the upper Transvaal Supergroup wall rocks to the Molopo Farms Complex in southern Botswana. Many of the zircons have irregular or angular grain margins, and some have rounded cores. Approximately half of the analysed grains yielded concordant 207Pb/206Pb ages ranging between 2 282 ± 29 and 2 113 ± 16 Ma. Assuming that these grains were inherited from the surrounding upper Transvaal Supergroup sedimentary strata, the youngest zircon age provides a maximum depositional age for these sediments. Importantly, these zircon ages coincide with dates from detrital zircons in upper Transvaal Supergroup strata in the eastern Kaapvaal Craton and in the Magondi Supergroup in western Zimbabwe. Hf isotope analyses of the rounded zircons suggest that these grains were sourced from a variable mixture of an old basement and more juvenile material. A younger age of 2 060 ± 12 Ma was obtained from a single subhedral zircon grain from the granite sheet. This is interpreted as the granite’s emplacement age, making it coeval with the adjacent Molopo Farms Complex that forms part of the Bushveld Large Igneous Province. [ABSTRACT FROM AUTHOR]

The present study is focused on the analysis of zircon inclusions found in pink to purple sapphires from Ilakaka (Madagascar) with an optical microscope, Fourier-transform infrared (FTIR), and micro-Raman spectroscopy in order to update previous knowledge and find insights to separate heated from unheated samples. In total, 157 zircon inclusions in 15 unheated samples and 74 zircon inclusions in 6 heated samples are analysed using micro-Raman spectroscopy with standardised parameters. The full width at half maximum (FWHM) of the main Raman band due to anti-symmetric stretching vibration ν3 of the SiO4 tetrahedron in the zircon structure has been carefully measured. In the unheated samples, it ranges from 6.26 to 21.73 cm−1 with an average of 10.74 cm−1, a median of 10.04 cm−1, and a standard deviation of 2.84 cm−1. On the other hand, it is lower in the heated samples, ranging from 4.83 to 14.97 cm−1 with an average of 7.23 cm−1, median of 7.06 cm−1, and standard deviation of 1.63 cm−1. In our unheated samples, the FWHM was rarely below 7 cm−1. In our heated samples, the FWHM was rarely above 12 cm−1 but mostly below 8 cm−1, with a variation restricted to less than 3 cm−1 in the same sample. The present work will hopefully further contribute to more accurately identifying the low-temperature heat treatment of pink sapphires from Ilakaka, Madagascar. [ABSTRACT FROM AUTHOR]

The recently discovered 460 Gaodi porphyry Mo-Cu deposit is a sub-economic deposit characterized by low Mo-Cu grades, dispersed mineralization, and separated Mo- and Cu-ore bodies. This study aims to elucidate the factors underlying this type of sub-economic mineralization. Electron-microprobe analyses of biotite from ore-related granite porphyry yielded Ti-in-biotite crystallization temperatures of 677–734 °C (an average of 719 °C) and biotite phenocryst crystallization depths of 6.0 to 12.9 km. LA-ICP-MS analyses of zircons from the same sample revealed average zircon Ce4+/Ce3+ ratios of 299.7 and elevated zircon lg(ƒO2) ratios, with an average ΔFMQ of +6.6 ± 1.9. These discoveries suggest that the magma responsible for ore formation boasts a high degree of oxidation, yet also possesses a magma chamber located at a significant depth within the upper crust. This implies an extensive exsolving depth for fluids. Furthermore, our microthermometry analysis of fluid inclusions reveals that a portion of the fluid experiences considerable conductive cooling as it ascends along the conduit, owing to the depth of fluid exsolution. This process results in the ore fluids remaining in the liquid-only region without undergoing boiling, which is conducive to the enrichment of metals. We emphasize the fact that fluid-exsolving depth plays a critical role in determining the metal grades and economic value of a porphyry deposit by regulating the P-T evolution path of the ore fluids [ABSTRACT FROM AUTHOR]

Late Cretaceous granitoids are developed in the eastern and western districts of the Gejiu ore district, but tin deposits mainly occur in the eastern district, and the reasons for the difference in mineralization between the eastern and western districts are still controversial. Considering the main factors controlling granite Sn fertility, the whole-rock geochemical characteristics of granites on both sides are compared. LA-ICP-MS zircon U-Pb analyses of the Gejiu granites yielded two age periods: the early phase from 79.2 to 83.3 Ma and the later phase from 73.8 to 75.6 Ma. The western district granites have higher zircon εHf(t), CaO/Na2O, Ba, and Sr concentrations and lower Rb/Sr ratios than the eastern district granites, indicating that the western district granites have more mantle-derived materials in the source than the eastern district granites. Results of oxygen fugacity show that the western granites have a higher oxygen fugacity condition. More depleted Ba, Sr, P, Eu and Ti characteristics with obviously negative Eu anomalies in the eastern granites also have high Rb/Sr ratios and low Nb/Ta and Zr/Hf ratios, indicating that the eastern granites experienced highly magmatic differentiation, attributed to high volatile F contents that can reduce the viscosity and solidus of magma. Combined with the differences in field observations and structural styles, on the whole, the western district granites have higher oxygen fugacities and lower F contents and magmatic differentiation than those in the eastern district granites, indicating that the western district granites are not conducive to mineralization. [ABSTRACT FROM AUTHOR]

Zircon samples of loess detritus were taken from Qugang loess profile in Maizhokunggar area, southern Tibetan Plateau. Based on the experimental analysis of zircon morphology, trace elements and zircon U–Pb age, provenance information and formation model of Qugang loess were discussed in combination with regional geological, topographic and geomorphological characteristics. The information of zircon morphology and trace elements suggests that the clastic zircons are of magmatic origin and proximal sedimentary characteristics. Zircon U–Pb age spectrum shows that the provenance information is significantly different from loess in the Loess Plateau and the northeastern Tibetan Plateau, related to the distribution of bedrock in regional geology, and corresponding to the Gangdese magmatic activity. The loess sediment development has a "Rock-Valley detrital material-Loess" model. [ABSTRACT FROM AUTHOR]

Integrated U-Pb, O and Lu-Hf isotopic analyses of detrital zircons, collected from fourteen European river sands and one beach sand from northern Germany, were carried out to study the evolution of the preserved European continental crust. The drainage area of these sand samples covers large areas in eastern and western Europe, which evolved independently until their amalgamation during the Paleozoic. U-Pb ages of detrital zircons from eastern and western Europe generally match the ages of the major magmatic events in the two tectonic regions. The combined histogram of 2403 zircon U-Pb ages, obtained for this study, shows five major periods of zircon crystallisation: 2.80–2.65, 1.95–1.35, 1.25–0.85, 0.65–0.40, and 0.40–0.25 Ga, which correspond broadly with the timing of supercontinent assembly. The correlation could be due to enhanced granitoid magmatism and zircon growth during the supercontinent amalgamation, or the high preservation potential of igneous rocks generated during continental collisions. The O and Hf isotopic data of the analysed European river zircons show wide spreads in δ18O and ε Hf (t) values at ca. 1.9 Ga and 650–250 Ma, contrasting with the limited range for the Mesoproterozoic zircons. This indicates that extensive reworking of pre-existing crustal rocks occurred during the late Paleoproterozoic and Paleozoic in the evolution of the European continental crust, whereas the formation of new crust played an important role during the Mesoproterozoic. Arc mantle Hf model ages for the detrital zircons were calculated to estimate when European juvenile crust was extracted from the mantle. Model age uncertainties were estimated using the bootstrap method, considering three sources of uncertainty: (i) uncertainty in the Hf isotopic composition of the mantle reservoir, (ii) uncertainty in the 176Lu/177Hf for the crustal source region, and (iii) analytical uncertainties. Two types of model ages are calculated based on constant crustal 176Lu/177Hf (T AM C), and on variable 176Lu/177Hf (T AM V), the latter being constrained by zircon δ18O values. Histograms of the calculated T AM C and T AM V model ages both show major juvenile extraction events between the late Paleo- and Mesoproterozoic. Although the principal periods in the European crustal growth contrast with those identified in the African, Russian and Mississippi river basins, the overall growth curves for the four continents show comparable results: (i) the formation of little or no continental crust before 4.0 Ga, and (ii) the formation of 50 % of the present crustal volume by ca. 2.0–1.6 Ga. [ABSTRACT FROM AUTHOR]

In recent decades, blue and fancy-colour sapphires have been gathered from secondary deposits derived from Tertiary basalts in the Muling area of north-eastern China. In this article, zircon inclusions in the blue sapphires were studied to characterise their morphology and structure, as well as to obtain the age of the host sapphires. The zircon inclusions in the studied samples were euhedral and transparent, and their dominant morphology was similar to that of typical zircon inclusions in sapphires associated with alkali basalts. Raman spectroscopy of the zircons showed only slight radiation damage, and cathodoluminescence images revealed two distinctive zoning patterns (in their cores and rims). LA-ICP-MS analyses of the zircon rims showed typical magmatic Th/U ratios. In situ U-Pb dating of the zircon rims yielded ages of 9 to 8 Ma--which is the inferred upper limit of the formation age of the host sapphires--while cores had much older ages that exceeded 110 Ma (i.e. an inherited age component). The 9-8 Ma sapphire age coincides with Late Miocene basaltic eruptions in the Dunhua-Mishan graben. Age dating of zircon inclusions in the Muling sapphires helps elucidate their geological origin and provides useful information for the provenance determination of gem corundum. [ABSTRACT FROM AUTHOR]

The Jiamusi Block is a crucial geological unit joining multiple tectonic regimes, including the Late Palaeozoic Palaeo‐Asian Ocean and the superposition of the Early Mesozoic Palaeo‐Pacific tectonic domain. However, the duration of the Palaeo‐Pacific Plate subduction beneath the Jiamusi Block has long been controversial. In this paper, we focus on clastic rocks from the Nanshuangyashan and Yunshan formations on the east margin of the Jiamusi Block and use the modal analysis of sandstones and detrital zircon U–Pb dating to trace the subduction history of the Palaeo‐Pacific Plate. Our analysis results suggest that the two groups of samples are characterized by a high content of monocrystalline quartz and a low content of lithic and feldspar, indicating that the sedimentary provenances were stable continental blocks and magmatic arcs. The detrital zircon ages of the Nanshuangyashan Formation have a major peak at ca. 245 Ma and two secondary peaks at ca. 470 and 228 Ma, respectively. The Yunshan Formation has a major peak at ca. 494 Ma and a secondary peak at ca. 265 Ma. The provenances of the Nanshuangyashan Formation were attributed to the Jiamusi Block, Khanka Block, and a Late Triassic magmatic arc. Similarly, the provenances of the Yunshan Formation were attributed to the Jiamusi and Khanka blocks. Detrital zircon analysis results show that the eastern margin of the Jiamusi Block was in the same back‐arc basin settings in the Late Triassic and the Late Jurassic. Thus, we propose that the eastern margin of the Jiamusi Block had been affected by the Palaeo‐Pacific Plate subduction in the Late Triassic and had continued to the Late Jurassic. [ABSTRACT FROM AUTHOR]

The Early Cretaceous Yellow Cat Member of the terrestrial Cedar Mountain Formation in Utah, USA. has been interpreted as a "time-rich" unit because of its dinosaur fossils, prominent paleosols, and the results of preliminary chemostratigraphic and geochronologic studies. Herein, we refine prior interpretations with: (1) a new composite C-isotope chemostratigraphic profile from the well-known Utahraptor Ridge dinosaur site, which exhibits δ13C features tentatively interpreted as the Valanginian double-peak carbon isotope excursion (the so-called "Weissert Event") and some unnamed Berriasian features; and (2) a new cryptotephra zircon eruption age of 135.10 ± 0.30/0.31/0.34 Ma (2σ) derived from the CA-ID-TIMS U-Pb analyses of zircons from a paleosol cryptotephra. Our interpretations of δ13C features on our chemostratigraphic profile, in the context of our new radiometric age, are compatible with at least one prior age model for the "Weissert Event" and the most recent revision of the Cretaceous time scale. Our results also support the interpretation that the Yellow Cat Member records a significant part of Early Cretaceous time. [ABSTRACT FROM AUTHOR]

The Jabal Hadb Ad Dayheen granitic complex in central Saudi Arabia is an alkaline granitic ring complex associated with a collapsed caldera. It mainly consists of monzogranite in the center, biotite-hornblende porphyritic granite, and biotite-aegirine-riebeckite granite, intruded by some felsic and mafic dikes. The petrological and geochemical characteristics show that the granitic suites consist of metalminous-peralkaline A-type granites. The secondary ion mass spectrometry (SIMS) zircon U-Pb analysis yielded 206Pb/238U ages of 613.3 ± 8.1–603.8 ± 3.8, 602.4 ± 3.8, 596 ± 5.6 Ma for biotitehornblende porphyritic granite, microgranite, and biotite-aegirine-riebeckite granite, respectively. The trace element characteristics and positive εHf(t) values (3.2–12.2) indicate that the granitic rocks of the Dayheen Ring Complex are mainly derived from the juvenile crust with the involvement of mantle-derived materials. Combined with the regional tectonic evolution, the formation of the Dayheen Ring Complex mainly covered four periods: (1) subduction initiation and formation of arc terranes (870–620 Ma)—volcanic craters formed during this period provided the channel for alkaline complex intrusion; (2) collision between East and West Gondwana continents and formation of the north East African Orogen (640−613 Ma)—monzogranite stock at the center of the ring complex emplaced during this period; (3) post-collision extension and collapse (613−602 Ma)—red metaluminous biotite-hornblende porphyritic granite and microgranite sheets in the rim of the Dayheen Ring Complex emplaced during this period; (4) within-plate extension (602 − 545 Ma)—white peralkaline biotite-aegirine-riebeckite granite and plenty of felsic and mafic dikes in the rim mainly formed during this period. The granitic rocks of the Dayheen Ring Complex mainly formed during the transitional stage of post-collison to within-plate extension after the collision between East and West Gondwana continents, and part of them formed during the early stage of the within-plate extension. U, Th, Zr, Nb, and rare earth element mineralization mainly formed during the early stage of the last period, having a close relationship with the intrusion of white peralkaline biotite-aegirine-riebeckite granite. [ABSTRACT FROM AUTHOR]

The duration and extent of sediment routing systems are intrinsically linked to crustal‐ to mantle‐scale processes. Therefore, distinct changes in the geodynamic regime may be captured in the detrital record. This study attempts to reconstruct the sediment routing system of the Canning Basin (Western Australia) during the Early Cretaceous to decipher its depositional response to Mesozoic‐Cenozoic supercontinent dispersal. Specifically, we reconstruct source‐to‐sink relationships for the Broome Sandstone (Dampier Peninsula) and proximal modern sediments through multi‐proxy analysis of detrital zircon (U–Pb, Lu–Hf and trace elements) and detrital rutile (U–Pb and trace elements). Multi‐proxy comparison of detrital signatures and potential sources reveals that the majority of the detrital zircon and rutile grains are ultimately sourced from crystalline basement in central Australia (Musgrave Province and Arunta region) and that proximal sediment supply (i.e., Kimberley region) is negligible. However, a significant proportion of detritus might be derived from intermediate sedimentary sources in central Australia (e.g., Amadeus Basin) rather than directly from erosion of crystalline basement. Broome Sandstone data are consistent with a large‐scale drainage system with headwaters in central Australia. Contextualization with other broadly coeval drainage systems suggests that central Australia acted as a major drainage divide during the Early Cretaceous. Importantly, reorganization after supercontinent dispersal is characterized by the continuation of a sediment pathway remnant of an earlier transcontinental routing system originating in Antarctica that provided a template for Early Cretaceous drainage. Review of older Canning Basin strata implies a prolonged denudation history of central Australian lithologies. These observations are consistent with the long‐lived intracontinental tectonic activity of central Australia governing punctuated sediment generation and dispersion more broadly across Australia and emphasize the impact of deep Earth processes on sediment routing systems. [ABSTRACT FROM AUTHOR]

Over 10,000 published detrital zircon ages have been reprocessed (applying a +10% normal and reverse concordance range) and analysed to understand the evolution of the detrital zircon record of north‐west Africa during the Phanerozoic. Using dissimilarity and clustering analysis, shifts in detrital zircon populations allow interpretation of the evolution of source regions and source to sink systems throughout the Phanerozoic within the West Gondwana superfan. Previous thermochronology and field studies conducted across north‐west Africa indicate significant and sustained shifts in source regions in Meso‐Cenozoic times which are not recorded in the detrital zircon geochronology record. This discrepancy is most notable for Mesozoic to modern source to sink studies focused on the evolution of the Atlasic rift and opening of the Atlantic and Tethyan Oceans to the west and north respectively. Our results indicate a high degree of similarity between samples from Cambrian times onwards due to successive phases of sediment recycling. This highlights the need to integrate detrital zircon analysis with other techniques to provide confident reconstruction of sediment routing systems across Morocco. This systematic review also reveals the ubiquitous occurrence of Mesoproterozoic zircons within Moroccan sediment. No basement of this age is known from north‐west Africa—often described as the 'Mesoproterozoic Gap', which was thought to be a diagnostic feature of sediment derived from the West African Craton. However, zircons of this age form 7% of all analysed zircons and are present in sediments from at least 700 Ma. The presence of this population is interpreted as strongly diagnostic of provenance from either the Amazonian Craton or the Eastern Gondwana Orogen within Central Africa. Their presence in the Moroccan detrital record from the Neoproterozoic onwards raises questions about the position of the West African Craton in the Proterozoic, and for the spatial extent of Mesoproterozoic orogeny within north Africa. [ABSTRACT FROM AUTHOR]

The northeastern Siberian craton stores numerous placers of diamonds that differ in morphology and texture, and originate from different types of primary deposits, primarily kimberlites. Analyses of mantle zircons selected from samples of alluvial and coarse clastic sediments in the watersheds of the Olenek and Kyutyungde rivers in the Anabar‐Olenek subprovince of the Yakutian diamond province provide constraints on kimberlite magmatism events in the area. The new U–Pb ages and typical kimberlitic signatures of the Kyutyungde zircons trace‐element patterns reveal three main magmatic events that produced kimberlites: Middle Paleozoic (Late Devonian to Early Carboniferous), Jurassic and Triassic. The Jurassic zircons (177–149 Ma) are mainly related to kimberlites in the proximal Kuoika‐Molodo and Khorbusuon fields. Triassic zircons (240–221 Ma) were probably released during large‐scale erosion of the eastern Anabar shield, however, the presence of such zircons in the Kyutyungde area indicates that kimberlites of the respective magmatic stage may exist within the immediate vicinity of the area. The only Middle Paleozoic zircon sample (358.6 Ma, D3‐C1 boundary) may originate from a proximal kimberlite within the Kyutyungde area. The presence of Middle Paleozoic kimberlitic zircons, along with harzburgite–dunitic pyropes, indicates that the primary deposit of diamonds and related minerals may exist near or within the Kyutyungde area. Late Ediacaran–Early Cambrian (573–473 Ma) mantle zircons found in Early Cambrian conglomerates of the area, along with other mantle minerals including Cr spinel of a diamond assemblage, record another Precambrian event of potentially diamondiferous magmatism in the Kyutyungde basin. [ABSTRACT FROM AUTHOR]

The Jinzhuping and Changkeng granites are related to the Helong W–Sn ore field in southern Jiangxi Province, China. Three different phases can be found in the Jinzhuping pluton, and their LA-ICP-MS zircon U–Pb ages are 155.2 ± 0.68 Ma, 154.0 ± 0.56 Ma, and 153.4 ± 0.99 Ma, respectively, indicating two types of granitic rocks. All granites in the Helong ore field have similar geochemical characteristics, they have high contents of SiO2 (73.99 wt.%–77.68 wt.%), and total alkali (7.56 wt.%–8.76 wt.%) and are weakly to strongly peraluminous. They are slightly enriched in HREE and depleted in Eu, Ba, Sr, P, and Ti. Zircon εHf(t) values of the Jinzhuping three granites are from −14.4 to −10.4, from −15.3 to −11.4, and from −18.1 to −10.5, and the Hf TDM model ages range from 1.83 to 2.06 Ga, from 1.89 to 2.14 Ga, and from 1.83 to 2.31 Ga, respectively. Whole-rock geochemistry and Hf isotope analysis indicate that the Helong granites experienced a high degree of differentiation and evolution derived by partial melting of the Late Paleoproterozoic crustal materials, and they formed in a backarc caused by low-angle subduction of the Paleopacific plate. [ABSTRACT FROM AUTHOR]

Reconstructing the tectonic architecture of the southern Altaids is of great importance to piece together the continental growth history of the Central Asian continent. In this paper, we address the subduction‐accretion process of the Paleo‐Tianshan Ocean, one branch of the South Tianshan Ocean, in the southern Altaids, through a detailed geological and geochemical investigation of the Wulanmoren Accretionary Complex (WAC). The WAC is composed of ophiolitic mélanges, ocean plate stratigraphy mélanges, and turbiditic coherent units. In this study, we present key geological, petrological, and geochemical evidence indicating back‐arc and ocean island affinity of the igneous rocks of the WAC. Zircon U‐Pb dates of these rocks ages range between 380.2 ± 1.3 and 302.0 ± 5.3 Ma. The sedimentary matrix units of the mélanges were deposited in the Early Devonian (∼405 Ma) to the Late Triassic (∼222 Ma), rather than Silurian strata as previously thought. However, the ages of some detrital zircons in the sedimentary matrix are Precambrian, pointing to a complex evolution involving multiple ocean island terrains and island arcs of different ages that accreted from the mid‐Paleozoic to the Early Mesozoic. Plain Language Summary: Well‐exposed rock outcrops of the Wulanmoren Accretionary Complex (WAC) offer an ideal opportunity to solve the enigma of the evolutionary history of the Paleo‐Tianshan Ocean (PTO) of Central Asia. We report field observations, geochemistry, and geochronology of the WAC in the southern Altaids, pointing to multiple tectonic settings of ages spanning from the Early Devonian (∼405 Ma) to the Late Triassic (∼222 Ma). These reconstructions suggest closure time of the PTO occurred post‐Triassic. Based on detrital zircons provenance analysis, we propose a multi‐island ocean model to explain the tectonic evolution of the PTO in the time period studied. Key Points: The Wulanmoren Accretionary Complex was composed of ophiolitic mélanges, ocean plate stratigraphy mélanges, and coherent unitsThe Late Paleozoic MORB‐like and OIB‐type basalts, and ∼222 Ma coherent units indicate closure of the Paleo‐Tianshan Ocean occurred post‐TriassicThe southern Paleo‐Asian Ocean was an archipelago with several subduction systems which is similar to the modern southwest Pacific [ABSTRACT FROM AUTHOR]

Trace elements in magmatic zircon exhibit characteristic trends during magma compositional evolution. Zircon geochemistry presents the advantage over whole rock geochemistry of showing progressive 'snapshots' of accompanying melt chemistry during magma crystallization, and in situ methods such as LA-ICPMS and SIMS can provide multiple analyses in zoned zircons for higher resolution of magmatic processes. However, one limitation is that zircon is typically a late-crystallizing phase, leaving much of the magmatic history unrecorded. Using the CAMECA ims1290 ion microprobe with Hyperion-II ion source, we explore whether micro-zircon (ca. 5–40 µm) captured by relatively early-crystallizing magmatic accessory minerals can meaningfully enhance the interpretations of zircon trace element records of magmatic evolution in two granites from Southern California: the La Posta 2-mica granite and the granite of Butler Peak (Big Bear Lake Intrusive Suite). We find that contamination of the inclusion measurement by major structural constituents of the host phase is a problem for most measurements, but that species which are not structural components of the host phases follow typical magmatic zircon trace element evolution trends. Compared to free grains from a mineral separate, zircon inclusions in ilmenite and apatite from the La Posta 2-mica granite are on average lower in Hf, recording plausible extensions of these magmatic evolution trends to earlier periods in magma evolution. Free zircons from the granite of Butler Peak's mineral separate form a more complex story, recording both mixing between Cretaceous magmas derived from different depths (based on their U/Yb and Eu/Eu* behavior) and inheritance of older Mesozoic to Proterozoic zircon. Most zircon inclusions in Butler Peak magnetite and ilmenite are chemically like the apparently shallow magma-derived Cretaceous zircons in the free matrix, while a small proportion of the included zircon resemble more closely the apparently deeper magma or the inherited grains. [ABSTRACT FROM AUTHOR]

The middle Cretaceous Blackleaf Formation records the first major transgression-regression of the Western Interior Seaway into the southwestern Montana retroforeland basin. Although Blackleaf sedimentology is well documented, sediment provenance and potential linkages with regional tectonics are not. Recent characterization of hinterland tectonics, fold-thrust belt detrital zircon signatures, and advances in high-n detrital zircon analysis allow for significant provenance refinement. We present new detrital zircon ages (n = 5468) from ten samples from the upper Blackleaf Formation (Intervals C and D) in southwestern Montana. Based on maximum depositional ages, sedimentation spanned from 106 to 92 Ma. Jurassic and Cretaceous grains were primarily derived from the older portion of the Cordilleran magmatic arc in western Idaho. Triassic and older grains were recycled from older central Idaho sedimentary strata inboard of the arc. Three depositional stages are identified based on statistical modeling of detrital age distributions. Stage 1 (106–104 Ma) records sourcing from lower Paleozoic strata in central Idaho. Stage 2 (105–101 Ma) records initial unroofing of upper Paleozoic–Triassic strata via propagation of the fold-thrust belt into eastern Idaho, accommodating shortening of Mississippian and younger rocks above the Lemhi Arch. Stage 3 (102–100 Ma) records continued unroofing in central Idaho down to Cambrian stratigraphic levels and distal mixing of sources in the eastern part of the basin. Exhumation in the fold-thrust belt beginning at ca. 105 Ma is coincident with margin-wide fault slip-rate increases. We infer that increased sedimentation rates and low-magnitude flexural loading from shallow thrusting in eastern Idaho drove clastic wedge progradation across the basin. [ABSTRACT FROM AUTHOR]

The Cenozoic development of the Scotia Sea and opening of Drake Passage evolved in a complex tectonic setting with sea‐floor spreading accompanied by the dispersal of continental fragments and the creation of rifted oceanic basins. The post‐Eocene tectonic setting of the Scotia Sea is relatively well established, but Late Mesozoic palaeo‐locations of many continental fragments prior to dispersal are largely unknown, with almost no geological control on the submerged banks. Detrital zircon analysis of dredged metasedimentary rocks of Bruce Bank from the South Scotia Ridge demonstrates a geological continuity with the South Orkney microcontinent (SOM) and also a clear geological affinity with the Trinity Peninsula Group metasedimentary rocks of the Antarctic Peninsula and components of the Cordillera Darwin Metamorphic Complex of Tierra del Fuego. Kinematic modelling indicates an Antarctic Plate origin for Bruce Bank and the SOM is the most plausible setting, prior to translation to the Scotia Plate during Scotia Sea opening. [ABSTRACT FROM AUTHOR]

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Estimations of the reproducibility of U–Pb ages from SHRIMP (Sensitive High-Resolution Ion MicroProbe) instruments are based on data from studies that are nearly 2 decades old. Since that time, refinement of analytical procedures and operational improvements have reduced the historically identified uncertainties of SHRIMP U–Pb analysis. This paper investigates 36 SHRIMP thermal ionisation mass spectrometry (TIMS) double-dated "real-world" geologic samples from a variety of igneous rock types to better understand both geological and analytical sources of disagreement between the two dating methods. Geoscience Australia's (GA) use of high-precision chemical abrasion thermal ionisation mass spectrometry (CA-TIMS) for chronostratigraphy in Australian sedimentary basins has produced a substantial selection of precisely dated zircons, which we can use to cross-correlate the SHRIMP and CA-TIMS ages throughout the Phanerozoic. A total of 33 of the 36 ages were reported with external SHRIMP uncertainties less than 1 % (95 % confidence). Six of eight cases where the CA-TIMS age was outside the SHRIMP uncertainty envelope were in samples where the 95 % confidence interval of the reported SHRIMP age was below 0.66 % uncertainty, suggesting that SHRIMP analyses of untreated zircon with smaller uncertainties are probably overoptimistic. The mean age offset between SHRIMP and TIMS ages is 0.095 %, but the distribution appears bimodal. Geological explanations for age discrepancies between SHRIMP and CA-TIMS are suggested by considering intrusive and extrusive age results separately. All but one sample where the SHRIMP age is more than 0.25 % older are volcanic. This offset could be explained by the better single-grain age resolution of TIMS, allowing identification and exclusion of antecrysts from the eruptive population, while SHRIMP does not have a sufficient single-grain precision to deconvolve these populations – leading to an apparent older SHRIMP age. In contrast, SHRIMP ages from plutonic rocks – particularly plutonic rocks from the early Paleozoic – are typically younger than the CA-TIMS ages from the same samples, most likely reflecting Pb loss from non-chemically abraded SHRIMP zircons, while chemical abrasion of zircons prior to TIMS analysis destroyed or corrected these areas of Pb loss. [ABSTRACT FROM AUTHOR]