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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 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]

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]

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]

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 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]

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 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]

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]

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]

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]

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]

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]

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]

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 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 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 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]

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]

Full‐plate reconstructions describe the history of past continental motions and how plate boundaries have evolved to accommodate these motions. Traditionally, tectonic reconstructions relied on geophysical data from the oceans and paleomagnetism as the primary quantitative constraints. However, these data do not directly constrain the paths of subduction zones or other plate boundaries, so reconstructing the complete configurations of tectonic plates in the past must rely on alternative methods. Here, we investigate the applicability of detrital zircon age spectra to characterize tectonic settings in deep time using a much larger data set than previously considered. We analyzed the proximity between reconstructed plate boundaries and sample sites assigned to different tectonic categorizations based on the proportion of zircon ages close to the depositional age and found that the categorization has an ∼70% success rate in distinguishing convergent settings. Results are not strongly influenced by factors such as the number of zircon grains available within each detrital sample or uncertainty in the depositional age of the sample. The ability of the categorization to define extensional settings, such as rift basins, is less clear. Nonetheless, the broader pattern of results at the scale of Pangea shows that categorized zircon samples form a coherent pattern, where samples with dominantly young zircons lie at the supercontinent periphery while samples in the core of Pangea are dominated by grains much older than the age of deposition. This result suggests that zircon data could help to quantify uncertainties in full‐plate reconstructions and discriminate between competing models for Proterozoic supercontinents. Plain Language Summary: The theory of plate tectonics explains how the continents we live on are in continual motion over geological time. Identifying where plates moved together or apart is a fundamental part of reconstructing Earth history. One novel approach is by analyzing the ages of individual crystals of zircon, a mineral found in many rocks. Previous studies put forward the idea that, in rocks where most zircons are not much older than the rock itself, these rocks likely formed close to the area where volcanos were active. Conversely, rocks formed far from active volcanos would lack these young zircons. We tested this idea using a much bigger data set of rock samples than previously considered. We found that the analysis of zircon ages can fingerprint volcanic activity with a reasonable success rate. Around 300 million years ago, most landmasses on Earth came together to form a supercontinent called Pangea. When viewed at the scale of Pangea, our results show that rocks divided into different groups using their zircon characteristics form coherent patterns distinguishing the periphery of Pangea from the core of it. The same method may help us to study other supercontinents that existed billions of years before Pangea. Key Points: Global plate reconstructions and a large zircon data set are used to quantify the link between detrital zircon age spectra and tectonic settingsAnalysis shows that detrital samples deposited in convergent settings are more likely to be dominated by young zirconsCategorized samples distinguish peripheral regions of Pangea from its core, significant for reconstructing earlier supercontinents [ABSTRACT FROM AUTHOR]

This work assessed the age distribution of Cadomian/Pan-African orogenic events (550-590 and 605-790Ma, respectively) in several zones of Iberian Massif by means of detrital and inherited zircon analysis compilation. Detrital zircon age spectra show that throughout the late Neoproterozoic-to-Early Ordovician era (~120Ma sedimentary record), the main systematic peak occurs at ~610Ma, followed by peaks at typical Cadomian ages (~590-550Ma). Inherited zircons incorporated in Cambrian-to-Lower Ordovician igneous rocks show typical Cadomian ages (~590-550Ma) but, once again, a remarkably consistent Pan-African ~610Ma peak occurs. In accordance with compiled zircon data and taking into account the evidence of North African peri-cratonic inliers, Ediacaran (~610Ma) zircons incorporated in Paleozoic magmas provide indirect evidence of Pan-African magmatism, suggesting that these magmas and synorogenic sediments are likely to constitute the cryptic stratigraphic infrastructure of most of the Iberian Massif. The main source of ~610Ma inherited zircons may be the lateral chrono-equivalents of the Saghro and Bou Salda-M-Gouna Groups (Anti-Atlas, Morocco) and/or coeval igneous rocks from West African Craton or Trans-Sahara Belt, emplaced at a stratigraphic level below the late-Ediacaran sediments of the Ossa Morena Zone and the Central Iberian Zone. Assuming that the Iberian crust is a fragment of the Pan-African orogen, a relative paleoposition situated between the West African Craton and the Trans-Saharan Belt during the Late Neoproterozoic is proposed. The closedsystem behaviour of Stenian-Tonian detrital zircon ages in the Trans-Sahara Belt suggests that this mega-cordillera acted as a barrier, in paleogeographic terms, separating the Sahara Metacraton from Iberia. In Iberia, the opening of the system to Stenian-Tonian detrital zircons during the Ordovician indicates that, at that time, the Trans-Saharan Belt had already become a vast peneplain, which favoured a large drainage system with a long-distance transport mechanism that fed the passive continental margins. [ABSTRACT FROM AUTHOR]

We utilized the Neoma™, a recently released MC-ICP-MS platform offered by ThermoFisher Scientific, to assess the behavior of the Lu-Yb-Hf system during laser ablation analyses of various zircon standards as well as solution-based analyses of the JMC-475 Hf standard doped with varying quantities of Yb and Lu. The primary goal of this work was to characterize the behavior of the Yb interference correction on the Neoma™ platform since this is one of the biggest issues in the Hf isotope analysis community and because the Neoma™ platform will supplant the Neptune™ series instrument. During laser ablation analysis, we found that the overall data quality scales proportionally with the total Hf signal intensity, with higher signal analyses producing extremely accurate (within 1 εHf unit) and precise (sub εHf unit within-run standard errors) data. At low Yb signals (<0.1 V 173Yb), we were not able to produce an accurate internal Yb mass bias factor. However, utilizing an empirical approach allows for the application of session-specific relationships between the Yb and Hf mass bias factors, determined by analysis of standards of varying Yb content, to produce accurate εHf values from zircons with higher Yb/Hf ratios even where the total Hf signal intensity is relatively low. Similar behavior was observed in the solution analyses. Lastly, while the behavior of the Yb interference correction on the Neoma™ platform appears comparable to the Neptune™ series MC-ICP-MS, further work will help refine the understanding of the controls on mass bias behavior, oxide formation, session-to-session stability, etc. [ABSTRACT FROM AUTHOR]

In-situ geochemical and isotopic analyses of zircon and monazite can provide compelling and detailed insights into the source and evolution of their hosting granite. Here we investigated the U-Th-Pb and Hf/Nd-O isotopic signatures of zircon and monazite in two petrological zones (i.e., fine- to medium-grained zone and medium-grained zone) of the Laojunshan granite pluton in the Qinling Orogen, central China, to better constrain their source nature and evolution processes. Co-existing magmatic zircon and monazite in both zones gave identical crystallization ages of ca. 113 Ma. In the fine- to medium-grained zone, both magmatic and xenocrystic zircons were identified, which respectively have ε Hf (t) values of −6.5 to −5.0 and − 17.4 to +5.1, and δ18O VSMOW values of +5.25‰ to +5.78‰ and + 5.17‰ to +9.15‰. The age distribution pattern and Hf O isotopic characteristics of the xenocrystic zircons are similar to those of detrital zircons from the wall rock, i.e., meta-sedimentary rocks in the Kuanping unit. Monazite grains in this zone have relatively low SiO 2 , ThO 2 but high CaO contents, dominated by cheralite-type substitution. These monazites have ε Nd (t) values of −5.8 to −4.6 and δ18O values of +3.79‰ to +5.66‰, except one grain (ε Nd (t) = −10.4 to −9.6, δ18O = +9.22‰ to +9.81‰), which is likely a xenocrystic crystal assimilated from wall rocks. The identical U Pb age but contrasting Nd O isotopic compositions between the xenocrystic monazite and the magmatic monazite grains indicate that the former might have experienced solid-state recrystallization process and completely lost radiogenic Pb. Both zircon and monazite geochemical and isotopic signatures consistently indicate that crustal assimilation occurred in the fine- to medium-grained granite zone. In contrast, in the medium-grained zone, only magmatic zircons and monazites were identified. The magmatic zircons have ε Hf (t) values of −3.2 to +2.7, and δ18O values of +4.65‰ to +6.36‰. The magmatic monazites are characterized by huttonite-type substitution with high SiO 2 , ThO 2 but low CaO contents. Their ε Nd (t) values vary from −5.7 to +1.6 (mostly < −4.4) and δ18O values from +4.65‰ to +6.36‰. Given that the isotopic features of zircons and monazites in this zone are consistent with their whole-rock isotope features and no inherited/xenocrystic grains were observed, the zircons and monazites should record the source isotope compositions. The presence of highly radiogenic Nd isotopes in monazite coupled with its normal mantle-like O isotopes suggest minor involvement of juvenile mantle-derived components in the magma source. Accordingly, we advocate combined study of zircon and monazite, which can better track granite source nature and evolution processes than individual mineral. • Zircon and monazite U Pb dating constrain the Laojunshan pluton formed at ca. 113 Ma. • Slight crustal contamination and magma injection have been effectively identified. • In-situ Hf/Nd-O isotopes can refine evolution processes and source nature of granite. [ABSTRACT FROM AUTHOR]

• Using the same dataset as tarduno et al. 2023, we find error bars that are 2–4 times larger. • Under most likely scenario, any amount of mobile-lid motion between 3.9 and 3.4 ga is permitted. • The motions of ∼2/3 of modern cratons would be unresolvable using a zircon dataset. • Zircon paleointensities provide no information for or against mobile-lid plate tectonics >3.4 ga. • All of this analysis assumes zircon paleointensities are reliable, which is dubious. The initiation of mobile-lid plate tectonics on Earth represented a critical transition towards a more familiar world in terms of surface temperature stabilization, biogeochemical cycling, topography creation, and other processes. Zircon-based estimates of the geomagnetic field intensity have recently been cited as providing evidence for the lack of mobile-lid motion between 3.9 and 3.4 billion years ago (Ga). We reanalyze the published dataset of 91 zircon paleointensities from the Jack Hills (Australia) and Green Sandstone Bed (GSB; South Africa) localities within this time interval and, using both analytical and bootstrap resampling approaches, show that the small number of samples result in large uncertainties in implied paleolatitude. Specifically, in more likely scenarios that do not assume coherent motion for both localities, all latitudinal displacements on Earth are permitted within the 95 % confidence interval. We also examine the less likely scenario that the two landmasses shared a motion history, which increases the data density and presents the best-case scenario for constraining latitudinal motion. In this case, the 95 % confidence interval of the zircon paleointensity data is compatible with the displacements of between 35 % and 52 % of modern continental localities, all of which experience mobile-lid tectonics. Finally, generating expected paleointensity time series for modern continents undergoing mobile-lid motion shows that about two-thirds of these motions would not be resolved by zircon paleointensities, even in the best-case scenario of combining Jack Hills and GSB datasets. All of these analyses assume that these zircons retain a primary paleomagnetic signal, an assertion which is opposed by a number of published zircon magnetism studies. We conclude that Archean zircon paleointensities do not provide evidence for or against mobile-lid plate tectonics prior to 3.4 Ga. Future paleomagnetic investigation of tectonic regime on the early Earth should therefore focus on magnetization directions in well-preserved, oriented whole rocks. [ABSTRACT FROM AUTHOR]

Combined Hf-O isotopic analyses of zircons from tuffs and lavas within the Sierra Madre Occidental (SMO) silicic large igneous province are probes of petrogenetic processes in the lower and upper crust. Existing petrogenetic and tectonomagmatic models diverge, having either emphasized significant crustal reworking of hydrated continental lithosphere in an arc above the retreating Far)allon slab or significant input of juvenile mantle melts through a slab window into an actively stretching continental lithosphere. New isotopic data are remark)ably uniform within and between erupted units across the spatial and temporal extent of the SMO, consistent with homogeneous melt production and evolu)tion. Isotopic values are consistent with enriched mantle magmas (80%) that assimilated Proterozoic paragneisses (~20%) from the lower crust. δ18Ozircon values are consistent with fractionation of mafic magma and not with assimilation of hydrothermally altered upper crust, suggesting that the silicic magmas evolved at depth. Isotopic data agree with previous interpretations where voluminous juvenile melts entered the lithosphere during the transition from a continental arc experiencing slab rollback (Late Eocene) to the arrival of a subducting slab window (Oligocene and Early Miocene) and failure of the upper plate leading to the opening of the Gulf of California (Late Miocene). An anomalously large heat flux and extension of the upper plate allow for the sustained fractionation of the voluminous SMO magmas and assimilation of the lower crust. [ABSTRACT FROM AUTHOR]

Water content and oxygen isotopes in zircon provide crucial constraints on magma source and process, yet they can be significantly modified by zircon metamictization, which causes secondary water absorption into the zircon crystal and the concomitant oxygen isotope changes. Therefore, it is imperative to develop a screening scheme to select the least-metamict zircons for the analyses. We propose a screening scheme based on our study on the Suzhou A-type granite (South China) through integrating Raman spectroscopy, water and trace element measurements, and oxygen isotope analysis. The results show that the primary water content is retained in zircon when the full-width at half maximum (FWHM) is <8 cm−1 or the Raman shift is >1007 cm−1 of v3(SiO4) vibration band, while the primary δ18O is preserved at <10 cm−1 FWHM or >1005.5 cm−1 Raman shift. Changes in trace element concentrations in Suzhou zircons are different from previous observations in metamict zircons but most likely related to magma evolution, which implies that trace elements are insensitive to metamictization. Primary δ18O in Suzhou zircons (4.5–6.0‰) fall into the mantle range, indicating a dominant mantle contribution to Suzhou granites. Primary water content was estimated at ca. 650–1400 ppm, significantly higher than those of typical I-type granite (400–736 ppm) and upper mantle-derived zircons (81–177 ppm). The high primary zircon water content was not controlled by the sub-solidus process, temperature, pressure, and cation charge balance but considered to reflect the high-water content in melts. This suggests a hydrous origin for the Suzhou A-type granite, which challenges the conventional view of anhydrous petrogenesis for A-type granites. [ABSTRACT FROM AUTHOR]

The Cathaysian Coastal Mountains are thought to be an ancient high‐topographic feature that existed along the margin of South China. They are characterised by extensive Jurassic–Cretaceous magmatism; however, their formation mechanism and timing remains uncertain. In this paper, we present sedimentological and detrital zircon analyses from Cretaceous–Eocene strata and drainage sediments from Hainan Island. Our analyses show a change in provenance from a proximal Cathaysian Coastal arc source in Cretaceous strata to a widely distributed intra‐island granite source in the Eocene strata and modern river sediments. Reconstruction of the crustal thickness evolution for the South China margin from Eu/Eu*‐in‐zircon proxy shows significant crustal thickening during the Late Jurassic–Cretaceous, thereby suggesting the existence of the Cathaysian Coastal Mountains. Together with a compilation of detrital zircon U‐Pb ages in the northern basins of the South China Sea margin, we conclude that the Cathaysian Coastal Mountains extended from the Red River region to Taiwan along the South China margin during the Late Jurassic–Cretaceous and then collapsed/eroded from northeast to southwest during the Eocene–Miocene. This large mountain range supplied detrital sediments to the marginal basins in the northern South China Sea and formed a topographic barrier that prohibited moist Pacific air to reach the relatively arid inland area of South China during the Late Jurassic–Cretaceous. [ABSTRACT FROM AUTHOR]

Tandem in situ and isotope dilution U-Pb analysis of zircons from pyroclastic volcanic rocks and both glacial and non-glacial sedimentary strata of the Pocatello Formation (Idaho, northwestern USA) provides new age constraints on Cryogenian glaciation in the North American Cordillera. Two dacitic tuffs sampled within glacigenic strata of the lower diamictite interval of the Scout Mountain Member yield high-precision chemical abrasion isotope dilution U-Pb zircon eruption and depositional ages of 696.43 ± 0.21 and 695.17 ± 0.20 Ma. When supplemented by a new high-precision detrital zircon maximum depositional age of ≤670 Ma for shoreface and offshore sandstones unconformably overlying the lower diamictite, these data are consistent with correlation of the lower diamictite to the early Cryogenian (ca. 717-660 Ma) Sturtian glaciation. These 670-675 Ma zircons persist in beds above the upper diamictite and cap dolostone units, up to and including a purported "reworked fallout tuff," which we instead conclude provides only a maximum depositional age of ≤673 Ma from epiclastic volcanic detritus. Rare detrital zircons as young as 658 Ma provide a maximum depositional age for the upper diamictite and overlying cap dolostone units. This new geochronological framework supports litho- and chemostratigraphic correlations of the lower and upper diamictite intervals of the Scout Mountain Member of the Pocatello Formation with the Sturtian (716-660 Ma) and Marinoan (≤650-635 Ma) low- latitude glaciations, respectively. The Pocatello Formation thus contains a more complete record of Cryogenian glaciations than previously postulated. [ABSTRACT FROM AUTHOR]

Hafnium (Hf) isotopes in zircon are important tracers of granite petrogenesis and continental crust evolution. However, zircon in granites generally shows large Hf isotope variations, and the reasons for this are debated. We applied U-Pb geochronology, traceelement, and Hf isotope analyses of zircon from the Miocene Himalayan granites to address this issue. Autocrystic zircon had εHf values (at 20 Ma) of -12.0 to -4.3 (median = -9). Inherited zircon yielded εHf values (at 20 Ma) of -34.8 to +0.3 (median = -13); the majority of εHf values were lower than those of autocrystic zircon. The εHf values of inherited zircon with high U concentrations resembled those of autocrystic zircon. Geochemical data indicates that the granites were generated during relatively low-temperature (<800 °C) partial melting of metasedimentary rocks, which, coupled with kinetic hindrance, may have led to the preferential dissolution of high-U zircon that could dissolve more efficiently into anatectic melt due to higher amounts of radiation damage. Consequently, Hf values of autocrystic zircon can be biased toward the values of U-rich zircon in the source. By contrast, literature data indicate that granites generated at high temperatures (>820-850 °C) generally contain autocrystic and inherited zircons with comparable Hf isotope values. During highertemperature melting, indiscriminate dissolution of source zircon until saturation is reached will result in near-complete inheritance of Hf isotope ratios from the source. Our results impose an extra layer of complexity to interpretation of the zircon Hf isotope archive that is not currently considered. [ABSTRACT FROM AUTHOR]

The Lohit Plutonic Complex (LPC) represents Trans‐Himalayan magmatic rocks in the easternmost sector of the Himalayan Orogen. It is divided into leucogranite‐granodiorite‐diorite dominant suite in the NE and the gabbro‐diorite‐granodiorite‐granite–trondhjemite suite in the SE by the Walong Thrust. U–Pb geochronological analyses of euhedral zircon grains from different magmatic phases of LPC reveal episodic magmatism. Zircon U–Pb age of 153.4 ± 1.4 Ma of a garnetiferous granite gneiss suggest that the crustal sourced magmatism was active in Arunachal Trans‐Himalaya during the late Jurassic. U–Pb ages of subduction induced magmatic rocks of LPC range between 117 ± 0.6 Ma and 49.5 ± 0.3 Ma. A significant contribution in crustal recycling during the Oligocene–Miocene is evident from crustally derived leucogranites having U–Pb ages ranging from 35.6 ± 0.3 Ma to 30 ± 0.3 Ma. A comparison of the crystallization ages of the Western Trans‐Himalayan units with those of eastern Trans‐Himalayan units reveals an earlier onset of Tethyan arc magmatism in the eastern sector. The most prominent phase in the eastern sector is during the Late Cretaceous while western and central sector show major activity during the Palaeocene–Eocene. [ABSTRACT FROM AUTHOR]

The essential sources and processes required for the formation of Cu–(Au)-porphyry deposits have been part of a long-standing debate. In this study we investigate one of the youngest and best-preserved world-class Cu–(Au)-porphyry systems in order to learn more about melt sources and what geochemical tracers in zircon and apatite might be useful to identify ore-forming intrusions within porphyry systems. Combined, in-situ Hf, O, and Nd isotope analyses in zircon and apatite imply that the Tampakan magmas were derived from depleted mantle sources. Hence, we suggest that older crustal components or metasomatized mantle are not required for the production of metallogenically fertile magmas in island arc settings. Based on the compositions of apatite and zircon, we confirm that previously established fertility-indicator signatures of these minerals are useful to identify fertile porphyry systems. Our data show that intrusions directly associated with mineralization events contain apatite with elevated Cl and S concentrations compared to pre- and post- mineralization igneous events. [ABSTRACT FROM AUTHOR]

The Ellsworth belt is one of several fault-bounded blocks exposed along the southeastern coast of Maine that formed within Ganderia. New ID-TIMS U–Pb geochronological data integrated with field relationships provide additional insights into the timing of magmatism and deformation in the Ellsworth belt. The deformed Lamoine Granite was selected for U–Pb zircon analysis to: (i) establish the protolith age; (ii) provide direct temporal constraints on regional low-grade metamorphism and deformation; and (iii) elucidate relationships between the Ellsworth belt and coeval rocks elsewhere in the Appalachian orogen. The Lamoine Granite was emplaced within the Ellsworth Schist at 492 ± 1.7 Ma; this is the first unequivocal evidence for a Furongian magmatic event in the Ellsworth belt. The schistosity in the Lamoine Granite is parallel to the main fabric of the host Ellsworth Schist and provides a maximum estimate for timing of the regional metamorphic overprint. Widespread deformation in the Ellsworth belt where kinematic indicators indicate a top-to-northwest sense of shear is attributed to thrusting during which progressive horizontal shortening, caused crustal thickening and peak greenschist facies metamorphism. The Cambrian U–Pb age permits correlation of the Lamoine Granite with the Cameron Road Granite in the Annidale belt of New Brunswick where subduction-related magmas intruded the Penobscot arc–back-arc and were subsequently deformed during the Penobscot Orogeny. [ABSTRACT FROM AUTHOR]

The response of garnet and zircon to prograde amphibolite-facies metamorphism in late Proterozoic mica schists from the Scottish Highlands has been investigated. Spatial analysis of zircon populations using scanning electron microscopy was undertaken in Dalradian Schists that have undergone a sequence of prograde garnet growth and localised breakdown reactions involving coupled dissolution–reprecipitation. Fluid availability and matrix permeability strongly control this metamorphic response and different generations of garnet contain radically different populations of metamorphic micro-zircon and associated changes in the detrital zircon population. Micro-zircon abundance increases during garnet growth, whereas that of detrital zircon decreases. The mineralogy of the matrix influences zircon abundance in porphyroblast phases, where garnet overgrows a micaceous matrix zircon-rich garnet forms and where it overgrows a quartzofeldspathic matrix the result is zircon-poor garnet. Following garnet growth, micro-zircon abundance decreases at each stage of the prograde reaction history, with sillimanite-zone schists containing the lowest abundance, suggesting micro-zircons are texturally less stable at staurolite- and sillimanite-grade metamorphism. Micro-zircons are distributed evenly across host minerals in the matrix, with the exception of retrograde chlorite where micro-zircons are absent due to fluids removing Zr before new zircon can precipitate. There is an overall decrease in the mode of zircon at each stage of the reaction history, indicating that zircon is a highly reactive phase during amphibolite-facies metamorphism and is very sensitive to individual prograde and retrograde reactions. [ABSTRACT FROM AUTHOR]

As one of the widest terranes exposed in icy Antarctica, the Larsemann Hills in the Prydz Bay belt preserves diverse rock types with a complex metamorphic history and thus is critical to the tectono-metamorphic evolution of East Antarctica. Garnet-sillimanite-spinel-cordierite–bearing and garnet-orthopyroxene–bearing granulites are typical rocks in the region. Phase equilibrium modelling and mineral thermometry based on detailed petrological and mineralogical analyses indicate that the granulites underwent extreme metamorphism with peak conditions to ultrahigh temperatures (UHTs). The high-UHT metamorphism is characterised by extremely high dT/dP values (>1000°C/GPa) along a clockwise path with evident decompression at high temperatures and subsequent near isobaric cooling. Textural relationships, in situ NanoSIMS zircon U–Pb analysis, and LA-ICP-MS zircon and monazite dating and trace element analysis indicate protracted tectono-thermal evolution from the latest Neoproterozoic to early Palaeozoic (c. 570–500 Ma), with a prograde stage likely from c. 570 to c. 550 Ma, a peak stage from c. 550 to c. 540 Ma, and a retrograde stage from c. 540 to c. 500 Ma. During the retrograde stage, major decompression should have occurred before c. 530 Ma, as indicated by the age of zircon included in spinel, and then near isobaric cooling followed and persisted from c. 530 to c. 500 Ma. The geochronological data contribute to the establishment of the thermal–temporal framework of the late Neoproterozoic to early Palaeozoic Prydz tectonic event. The results also indicate that the assemblage of the investigated granulites basically resulted from the late Neoproterozoic to the early Palaeozoic tectono-thermal event, and the high-UHT conditions revealed by the granulites in the Larsemann Hills imply a much wider distribution of high heat flow and potential UHT metamorphism in the Prydz Bay region. Both the Larsemann Hills and the Rauer Group may have been in a similar and interrelated tectono-thermal setting from the late Neoproterozoic to the early Palaeozoic during the assembly of the Gondwana supercontinent. [ABSTRACT FROM AUTHOR]

In most geologic applications, if barite is present, it must be separated from zircon to enable analysis of the zircon. Current methods of barite removal include mechanical comminution in a ball mill or conversion to barium carbonate by boiling in an aqueous solution of sodium carbonate. Both procedures have potentially serious drawbacks. We optimized an alternative technique for barite removal to avoid these shortcomings. In repeated experiments, boiling in an aqueous solution of 0.1 M diethylenetriaminepentaacetic acid (DTPA) and 6 wt% potassium carbonate for one hour dissolved about 90% of sand-size barite grains. Examination of barite after boiling in DTPA solution revealed evidence for attacks on crystal surfaces in the form of microscopic scallops and pits. In contrast, zircon crystal surfaces were not detectably altered at the microscopic scale by a boiling solution of DTPA and potassium carbonate. The DTPA and potassium carbonate solution procedure may be superior to the other two barite removal methods in two ways. First, it might not introduce bias into the sample, in contrast to both of the other two methods. Second, it requires less time than the sodium carbonate solution technique. If future research shows that the DTPA and potassium carbonate solution technique does not affect isotopic systems in zircon, this method appears to be a favorable alternative to both milling and boiling in sodium carbonate solution. [ABSTRACT FROM AUTHOR]

The mechanism and timing of crustal growth and differentiation on early Earth are debated. Evidence of crustal differentiation is detectable as deviations from Earth's assumed chondritic uniform reservoir (CHUR) as crust is extracted from the mantle leading to a melt-depleted reservoir. For the long-lived zircon Lu-Hf system, no incontrovertible evidence of significant mantle depletion >3.8 Ga exists. We conduct combined U-Pb and Lu-Hf isotopic analyses for the detrital zircon from the Caozhuang supracrustal sequence in North China. The zircon Hf isotopic compositions are broadly scattered along the CHUR evolution line. However, given the possibility of potential systematic biases in zircon petrogenesis and the unique tectonic setting of early Earth, we posit that magmatism controlled by the nascent forms of plate tectonics during the Eoarchean could have likely hidden the degree of ancient crust-mantle differentiation. The non-depleted zircon Hf isotopes observed in North China and globally during early Earth may in verity imply the existence of ubiquitous depleted mantle domains at that time. [ABSTRACT FROM AUTHOR]

This work assessed the age distribution of Cadomian/Pan-African orogenic events (550-590 and 605-790Ma, respectively) in several zones of Iberian Massif by means of detrital and inherited zircon analysis compilation. Detrital zircon age spectra show that throughout the late Neoproterozoic-to-Early Ordovician era (~120Ma sedimentary record), the main systematic peak occurs at ~610Ma, followed by peaks at typical Cadomian ages (~590-550Ma). Inherited zircons incorporated in Cambrian-to-Lower Ordovician igneous rocks show typical Cadomian ages (~590-550Ma) but, once again, a remarkably consistent Pan-African ~610Ma peak occurs. In accordance with compiled zircon data and taking into account the evidence of North African peri-cratonic inliers, Ediacaran (~610Ma) zircons incorporated in Paleozoic magmas provide indirect evidence of Pan-African magmatism, suggesting that these magmas and synorogenic sediments are likely to constitute the cryptic stratigraphic infrastructure of most of the Iberian Massif. The main source of ~610Ma inherited zircons may be the lateral chrono-equivalents of the Saghro and Bou Salda-M'Gouna Groups (Anti-Atlas, Morocco) and/or coeval igneous rocks from West African Craton or Trans-Sahara Belt, emplaced at a stratigraphic level below the late-Ediacaran sediments of the Ossa Morena Zone and the Central Iberian Zone. Assuming that the Iberian crust is a fragment of the Pan-African orogen, a relative paleoposition situated between the West African Craton and the Trans-Saharan Belt during the Late Neoproterozoic is proposed. The closedsystem behaviour of Stenian-Tonian detrital zircon ages in the Trans-Sahara Belt suggests that this mega-cordillera acted as a barrier, in paleogeographic terms, separating the Sahara Metacraton from Iberia. In Iberia, the opening of the system to Stenian-Tonian detrital zircons during the Ordovician indicates that, at that time, the Trans-Saharan Belt had already become a vast peneplain, which favoured a large drainage system with a long-distance transport mechanism that fed the passive continental margins. [ABSTRACT FROM AUTHOR]

Multiple parting bands within Permo–Carboniferous coal that are generally enriched in critical metals in the northern North China have been confirmed to be altered from volcanic ash (tonsteins). The tonsteins and adjacent coal in some areas contain boehmite with varying contents. Whether or not the boehmite has a relationship with the volcanic-ash-altered kaolinite remains poorly understood. Herein, petrographical, mineralogical, whole-rock geochemical, and in-situ elemental analyses, combined with U–Pb–Hf isotopic analysis of zircon, were performed for the boehmite-bearing/rich partings and coal collected from the eastern edge of the Datong and Jungar coalfields. Except for the boehmite, well-ordered kaolinite is predominant in the parting samples, where the columnar/tabular and vermicular kaolinite are commonly present. Additionally, the zircons separated from the representative parting and coal samples are mostly igneous origin with only one age population of ca. 300 Ma, almost same with the depositional age of the coal, suggesting that the kaolinite in the inorganic constitutes of the investigated coal seams were mainly altered from volcanic ash. Numerous fine-grained boehmite exhibit textural features of replacement for columnar/tabular and vermicular kaolinite along the cleavage cracks in the parting samples, suggesting that such boehmite were formed from desilication of volcanic-ash-altered kaolinite. The tonsteins and coal along the eastern edge of the coalfields were uplifted and influenced by fault activities due to Indosinian and Yanshan orogeny, which were probably experienced intensive leaching by silica-undersaturated percolating water and groundwater, resulting in desilication of volcanic-ash-altered kaolinite and precipitation of residual Al as boehmite. The Ga, preserved in the alumina octahedral sheets of volcanic-ash-altered kaolinite, were retained by boehmite due to its very similar geochemical behavior with Al. The formation of boehmite and its retention for Ga made a contribution to the genesis of high–Al–Ga coal in the northern North China. • Boehmite was formed from desilication of volcanic-ash-altered kaolinite. • Formation of boehmite and its retention for Ga contributed to genesis of high–Al–Ga coal. • Volcanic ash play a role in enrichment of critical metals in Permo–Carboniferous coal of North China. [ABSTRACT FROM AUTHOR]

An increasing number of detrital zircon U–Pb geochronological data have been reported to trace sediment provenance for the Cenozoic Qaidam basin, which is crucial to understanding crustal deformation, paleoclimate change and basin development in northern Tibetan Plateau and to assessing geodynamic models of plateau growth. However, the existing provenance interpretations are highly diverse and how the northern Tibet has evolved remains controversial. This contribution presents new detrital zircon dating results from Cenozoic outcrop and borehole samples and compiles published data from the whole Qaidam basin, adjacent small Cenozoic basins and the surrounding mountains. Our new synthesis indicates that, Paleoproterozoic signals (1800–2000 Ma and 2350–2500 Ma), rather than the Permian–Triassic ages, can be applied effectively to distinguish the Qilian, Altun and Eastern Kunlun-sourced detrital zircons. The Cenozoic Qaidam basin exhibits spatiotemporally variable detrital zircon age populations. Most sandstones from the western and southern basin are characterized by Phanerozoic bimodal age spectra (i.e., 400–480 Ma and 220–280 Ma) with minor Precambrian signals, indicating major contributions from the neighboring Altun and Eastern Kunlun ranges. By contrast, almost all the northern and eastern basin sandstones display prominent early Paleozoic detrital zircon ages; but Paleoproterozoic, Neoproterozoic (750–950 Ma) and Permian–Triassic signals only appear as dominant age clusters in some samples. Different temporal variation trends are observed from the investigated sections in this region, revealing variable zircon supply from different micro-terranes in the Qilian Mountains. This implies that using detrital zircon provenance data from a single section or from a local area of the Qaidam basin to address regional tectonic and climatic issues of the northern Tibetan Plateau unlikely provide useful results. We propose that the Cenozoic Qaidam basin deposits were derived from localized, adjacent source regions, rather than cross-basinal, distant mountains. Our conclusions support models with synchronous deformation throughout most of northern Tibet in the Cenozoic. The observed spatiotemporal variations in detrital zircon populations are not only attributed to tectonic deformation-induced source changes, but can also be due to heterogeneity of the source terranes (e.g., durability and zircon fertility) and variable factors (e.g., hydrodynamic sorting, recycling and sedimentary microenvironment) in transport-deposition processes. This study also highlights the importance of involving detrital zircon textural and sedimentological parameters to zircon provenance interpretations. An integrated provenance analysis combining other detritus components is helpful to comprehensively characterize source-to-sink systems for sedimentary basins. • Spatiotemporal variations in Qaidam basin detrital zircon ages are evident. • Paleoproterozoic zircon ages are unique signatures for the Qilian Mountains. • Cenozoic deposits were from nearby sources, rather than cross-basinal mountains. • Varied source-to-sink systems contribute to detrital zircon provenance variations. • Detrital zircon analysis on a local area cannot address regional tectonic issues. [ABSTRACT FROM AUTHOR]

[Display omitted] Evolution of internal or external oceanic domains can bring decisive indications into the mode of formation of supercontinents, which is key to understand the supercontinent cycle. Defining the type of ocean evolving in the Central Asian Orogenic belt (CAOB) is thus critical to better understand the Earth's supercontinental evolution. In this contribution, we provide systematic and combined U-Pb, trace-element in zircon and hafnium-in-zircon analyses of four turbidites of the Altai accretionary wedge. These turbiditic rocks provide constraints into the early Paleozoic subduction-accretionary stages of the Mongolian Accretionary Collage (MAC) and show a major detrital age peak in the Cambro-Ordovician (∼490–500 Ma), with minor Neo- and Paleo-Proterozoic to Archean peaks. The zircon trace-elemental patterns are consistent with derivation mostly from magmatic arc (with granitoids affinity), interpreted as detritus sourced from the Ikh-Mongol continental arc system further north-east (present coordinates). The main detrital zircon peak together with the zircon magmatic arc origin suggest that the subduction-accretionary stage was active from 550 to 430 Ma showing mixed ε Hf (t) values (-20 to + 15). A summary of the detrital zircon ε Hf (t) values from 550 to 430 Ma suggests a continuous increase of ε Hf (t) mean values from + 0.2 to + 6.1 towards younger ages. The younging juvenile trend can be compared to the evolution of external orogeny, therefore consistent with a Pacific-type accretionary system facing an external ocean. At last, the results combined with two paleo-geographic reconstructions from the literature imply that the MAC may have been part of the Peri-Siberian accretionary orogeny in the early Paleozoic. [ABSTRACT FROM AUTHOR]

The Gentio metagranitoid presents equigranular and porphyritic facies, modal composition ranging from tonalite to monzogranite with calculated TZr<800 °C for most samples. Its mineralogy is dominated by quartz and feldspar (77% to 95%), biotite is the only mafic mineral present (2% to 18%) and, titanite, zircon, apatite, allanite are important accessory phases. These rocks range from metaluminous to weakly peraluminous, and have large variation in major and trace elements, and high alkali contents (>6 wt.%). Zircon analyses by LA-ICP-MS and SHRIMP yielded a concordia age of 2 119±10 Ma for the porphyritic facies and an upper intercept age of 2 111±15 Ma for the equigranular facies. The whole-rock Sm-Nd TDM ages vary from 2.4 to 2.8 Ga with εNd(2.1) values between −0.7 and −5.3, indicating crustal derivation from distinct and/or heterogeneous protoliths. Field observations indicate that the Gentio metagranitoid was formed through different pulses of magma. Individual batches were subject to little or even no fractionation process after its emplacement. Although the Gentio metagranitoid crosscuts metamafic and metaultramafic rocks akin to an oceanic arc setting, this pluton is likely originated by partial melting of a more evolved quartz-feldspathic crustal igneous rock in a post-collisional environment, after the accretion of the arcs from the Mineiro belt and rocks of the Mantiqueira Complex. [ABSTRACT FROM AUTHOR]

Zircon separates from the contact aureole of the syn-tectonic Dawros–Currywongaun–Doughruagh Complex, western Ireland, are studied to constrain the nature and timing of magmatism associated with the early stages of the Grampian Orogeny. The samples analysed come from the uppermost part of the Dalradian Supergroup in northern Connemara (the Ben Levy Grit Formation), where a laterally extensive (>10 km) package of metamorphosed siliciclastic sedimentary rocks containing heavy mineral seams crops out. The seams mainly comprise magnetite, but zircon is also present in greater than accessory quantities. The seams have been locally reworked at granulite-facies metamorphic conditions during intrusion of the Dawros–Currywongaun–Doughruagh Complex magmas. Here we combine in situ mineral chemical and U–Pb geochronological analyses of zircons from samples of these heavy mineral seams collected at different locations in the Dawros–Currywongaun–Doughruagh Complex thermal aureole. An important finding is that the zircons studied have magmatic trace-element compositions, interpreted here as a function of their growth during contact metamorphic-induced partial melting. The zircons yield a range of U–Pb spot ages whose uncertainties suggest a maximum duration of zircon growth of ˜11 Ma, between 477.1 and 466.1 Ma, though it is likely that zircon growth occurred much more quickly than this. The age constraints revealed here match well with the range of 475 to 463 Ma previously proposed for the Grampian Orogeny overall in Connemara and lend useful support to models that argue for high-intensity, relatively short-lived Grampian orogenesis in the Connemara Caledonides. [ABSTRACT FROM AUTHOR]

The Capricorn Orogen, Western Australia, is a complex orogenic zone that records the convergence and collision of the Archaean Yilgarn and Pilbara cratons in forming the West Australian Craton (WAC), then over one billion years of subsequent intracontinental reworking. Granites associated with these tectonothermal events (the Dalgaringa, Bertibubba, Moorarie, Durlacher and Thirty Three supersuites) are exposed in the western part of the Capricorn Orogen. This study integrates radiogenic (U–Pb and Hf) and stable isotope (O) analysis of zircon grains from granitic rocks in the Capricorn Orogen to determine their ages and magmatic sources, including the relative contributions of mantle versus crustal material. Granites from the margin of the Yilgarn Craton record periods of crustal growth and reworking during the Archaean that influenced later Proterozoic magmatic events. Components of the Capricorn Orogen, collectively termed the Glenburgh Terrane, have previously been considered to be exotic to the adjacent Pilbara and Yilgarn cratons. However, new U–Pb zircon geochronology and Lu–Hf isotope compositions of basement rocks in the Glenburgh Terrane (the Halfway Gneiss) have similarities to some terranes of the Yilgarn Craton, and are interpreted to represent a reworked portion of the craton that was re-accreted during the Glenburgh Orogeny. Arc magmatism during the Ma Glenburgh Orogeny resulted in a period of crustal growth, with magmas representing a mixture of 50–90 % mantle-derived magmas and 50–10 % magmas derived from an evolved crustal component with an isotopic composition equivalent to that of the Halfway Gneiss. Following assembly of the WAC, granite magmatism in the Capricorn Orogen records a significant change from one dominated by mantle-derived magmatism to one dominated by crustal melting and an increased contribution from metasedimentary material. This transition reflects a geodynamic evolution from subduction–accretion to collision and intracratonic reworking. The isotopic characteristics of granites from the Moorarie Supersuite indicate three distinct sources: (1) a metasedimentary component; (2) an evolved crustal component, comparable with the Glenburgh Terrane; (3) a mafic juvenile component. Following this, the Hf–O compositions of the Durlacher Supersuite indicate that they were derived from reworking of the Moorarie Supersuite granites, and require no juvenile contribution or any additional sedimentary source. The isotopic compositions of the Thirty Three Supersuite pegmatites indicate that they were largely derived from reworking of the Moorarie and Durlacher supersuites. [ABSTRACT FROM AUTHOR]

Middle to Upper Jurassic strata in the Paradox Basin and Central Colorado trough (CCT; southwestern United States) record a pronounced change in sediment dispersal from dominantly aeolian deposition with an Appalachian source (Entrada Sandstone) to dominantly fluvial deposition with a source in the Mogollon and/or Sevier orogenic highlands (Salt Wash Member of the Morrison Formation). An enigmatic abundance of Cambrian (ca. 527-519 Ma) grains at this provenance transition in the CCT at Escalante Canyon, Colorado, was recently suggested to reflect a local sediment source from the Ancestral Front Range, despite previous interpretations that local basement uplifts were largely buried by Middle to Late Jurassic time. This study aims to delineate spatial and temporal patterns in provenance of these Jurassic sandstones containing Cambrian grains within the Paradox Basin and CCT using sandstone petrography, detrital zircon U-Pb geochronology, and detrital zircon trace elemental and rare-earth elemental (REE) geochemistry. We report 7887 new U-Pb detrital zircon analyses from 31 sandstone samples collected within seven transects in western Colorado and eastern Utah. Three clusters of zircon ages are consistently present (1.53-1.3 Ga, 1.3-0.9 Ga, and 500-300 Ma) that are interpreted to reflect sources associated with the Appalachian orogen in southeastern Laurentia (mid-continent, Grenville, Appalachian, and peri-Gondwanan terranes). Ca. 540-500 Ma zircon grains are anomalously abundant locally in the uppermost Entrada Sandstone and Wanakah Formation but are either lacking or present in small fractions in the overlying Salt Wash and Tidwell Members of the Morrison Formation. A comparison of zircon REE geochemistry between Cambrian detrital zircon and igneous zircon from potential sources shows that these 540-500 Ma detrital zircon are primarily magmatic. Although variability in both detrital and igneous REE concentrations precludes definitive identification of provenance, several considerations suggest that distal sources from the Cambrian granitic and rhyolitic provinces of the Southern Oklahoma aulacogen is also likely, in addition to a proximal source identified in the McClure Mountain syenite of the Wet Mountains, Colorado. The abundance of Cambrian grains in samples from the central CCT, particularly in the Entrada Sandstone and Wanakah Formation, suggests northwesterly sediment transport within the CCT, with sediment sourced from Ancestral Rocky Mountains uplifts of the southern Wet Mountains and/or Amarillo-Wichita Mountains in southwestern Oklahoma. The lack of Cambrian grains within the Paradox Basin suggests that the Uncompahgre uplift (southwestern Colorado) acted as a barrier to sediment transport from the CCT. [ABSTRACT FROM AUTHOR]

To better constrain the petrogenesis and tectonic setting of the granitic plutons in the Guaizihu region, NW China, this study presents a new analysis of zircon U–Pb ages, whole-rock geochemistry and Hf isotopes of syenogranites. The syenogranites are medium- to coarse-grained, with moderate to high SiO2 (72.55–74.27 wt%) and Al2O3 (13.02–13.75 wt%) contents and moderate total alkalis (Na2O + K2O, 7.58–7.98 wt%), which indicate that the syenogranites exhibit calc-alkaline and peraluminous characteristics. The low Ce, 10 000 Ga/Al, and A/CNK values and the negative correlation of SiO2 and P2O5 confirm that the syenogranites are of I-type origin. The whole-rock geochemistry demonstrates that the magma was generated by partial melting and experienced fractional crystallisation. Specifically, the correlations of Rb with Ba and Sr and the weak negative Eu anomalies indicate that the plagioclase has undergone fractional crystallisation. In addition, Eu anomalies and La/Sm–La relations show that both fractional crystallisation and partial melting contributed to the magmatic process. The positive εHf(t) values (0.11–9.78); enrichments in Rb, Th and other LILEs; depletions in Nb, Sr and other HFSEs; and the ratios of geochemical elements indicate that the syenogranites were generated from the partial melting of juvenile crust. The granites are inferred to have formed in a post-collisional extensional environment. Additionally, the U–Pb zircon ages (284.6 ± 0.84 Ma and 269.4 ± 1.2 Ma) of syenogranites suggest that final closure of the Paleo-Asian Ocean occurred before 285 Ma. Granites in the Guaizihu region are dated at 284.6 ± 0.84 Ma and 269.4 ± 1.2 Ma, and the Paleo-Asian Ocean, where the Engger Us Ophiolite Belt is located, closed before 285 Ma. Granites are medium- to coarse-grained and highly fractionated I-type syenogranites. Granites have been derived from magma generated by the partial melting of juvenile crust followed by fractional crystallisation. Granites were formed in an intraplate extensional environment related to a post-collisional event. [ABSTRACT FROM AUTHOR]