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

The 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]

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]

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]

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 Bacajá domain, southeastern Amazonian craton, comprises Mesoarchaean and Siderian terrains reworked during the Transamazonian cycle. Combined analyses of zircon LA-ICP-MS U-Pb and Lu-Hf with whole-rock Sm-Nd from the northeast portion of this domain made it possible to propose an evolutionary sequence between ca. 2.60 and 2.06 Ga. Gneisses with an igneous protolith age of 2630±15 Ma show negative signatures (εHf(t) = -0.3 to -1.7 and εNd(t) = -3.08 to -2.98) and a Mesoarchaean formation (Hf-TDMC and Nd-TDM model ages range from 3.0 to 3.2 Ga). Rhyacian granite genesis lasted about 40 million years (2.10-2.06 Ga) and was divided into two magmatic periods. The first is represented by deformed granitoids with zircons yielding crystallization ages between 2.10 and 2.09 Ga and model ages (Hf-Nd) at about 2.5 Ga. The second event is represented by granitoids with preserved magmatic texture, crystallization ages of 2.06 Ga, and Siderian model ages (Hf-Nd) of around 2.3 Ga. The overall Hf isotopic analyses of this Rhyacian granite genesis exhibit a spread of εHf(t) values between 1.8 and -2.9, which show a probably underestimated mantle-derived contribution in this period. [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 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]

The Saar–Nahe Basin is one of the largest intra-continental basins of the European Variscides. It is filled with up to 6500 m thick volcano-sedimentary rocks representing up to 40 million years of late- and post-orogenic basin evolution from the early Pennsylvanian to the late Early Permian. Radioisotopic dating of magmatites as well as intra- and extra-basinal pyroclastic rocks from the study area was carried out mainly during the end of the last century. Here, we present the first high-precision U–Pb CA-ID-TIMS age of 298.7 ± 0.4 Ma for a hitherto undated ash tuff layer of the Altenglan Formation near the middle part of the Pennsylvanian-Permian succession of the Saar–Nahe Basin. Comparative analyses of zircons from the same tuff layer and a closely associated tuff by U–Pb LA-ICP-MS yielded an age of 299.5 ± 2.6 Ma supporting the CA-ID-TIMS result. Based on the new data, the Pennsylvanian-Permian boundary in the study area is close to or even within the Altenglan Formation and overlying Rotliegend formations have to be considered of clearly Permian in age. A recently discovered and globally important fossil tetrapod lagerstaette of the Remigiusberg Formation lying immediately below the Altenglan Formation at the base of the Saar–Nahe Rotliegend is suggested to be of earliest Asselian minimum age. [ABSTRACT FROM AUTHOR]

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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]

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]

The evolution of the western Kunlun‐Pamir region involved the opening and closing of several branches of the Paleo‐Tethys Ocean, although the specific timing of these events is poorly constrained. Here, we present a synthesis of sedimentary, magmatic, and metamorphic records associated from the Mazar‐Kangxiwa suture zone in the western Kunlun‐Pamir that is generally regarded as the main Paleo‐Tethys Ocean suture. These data show that the Paleo‐Tethyan oceanic basin opened at ca. 340 Ma and closed by ca. 250 Ma, and there is no record of a magmatic arc between ca. 300–250 Ma. The absence of a magmatic arc was a result of oceanic crust underthrusting, rather than oceanic subduction, which is consistent with a narrow back‐arc basin. Our study provides an important example of how an oceanic basin opened and closed without oceanic subduction, and highlights a potential mechanism to account for the absence of a magmatic arc. Plain Language Summary: The closure of oceanic basins is generally believed to result from oceanic subduction associated with development of arc magmatism. However, there are no magmatic arcs associated with the closure of some oceanic basins in the Paleo‐Tethys realm. In order to understand the detailed history of ocean basins in the Paleo‐Tethys oceans, we carry out an integrated in situ analysis of zircon U‐Pb age and Hf‐O isotopes, along with whole‐rock geochemistry for sedimentary, magmatic, and metamorphic records from the Mazar‐Kangxiwa suture zone in the western Kunlun‐Pamir that is widely regarded as the main Paleo‐Tethys Ocean suture. Our data reveals that there is no record of a magmatic arc associated with Paleo‐Tethys Ocean closure during the Permian (ca. 300–250 Ma). This Paleo‐Tethyan oceanic basin was closed by oceanic crust underthrusting, rather than oceanic subduction. Thus, not all Paleo‐Tethyan oceanic basins were closed by subduction with development of arc magmatism. We propose that widespread oceanic crust underthrusting accounts for the common absence of a magmatic arcs in oceanic basins of the Paleo‐Tethys realm. Key Points: There is no record of a magmatic arc during oceanic basin closure in the Mazar‐Kangxiwa suture zone between ca. 300–250 MaThis Paleo‐Tethyan oceanic basin opened at ca. 340 Ma and closed by ca. 250 MaOceanic crust underthrusting was a potential mechanism to account for oceanic basin closure and the absence of a magmatic arc [ABSTRACT FROM AUTHOR]

The study of the pre-Mesozoic geological history of NE Mexico offers the opportunity to reconstruct the processes that occurred at the NW margin of Gondwana. The Huizachal–Peregrina Anticlinorium, which is located west of Ciudad Victoria (Tamaulipas) is a regional structure produced during the Cretaceous–Palaeogene Laramide Orogeny. Its eroded core exposes Precambrian and Palaeozoic units that together comprise the Sierra Madre Oriental basement. These units are the Neoproterozoic metamorphic Novillo Complex, the Ordovician Peregrina Tonalite, the metamorphic Pennsylvanian Granjeno Complex, and the sedimentary Silurian–Permian Tamatán Group. Aserradero Rhyolite belongs to the Tamatán Group, occurring between the siliciclastic deposits of the Early Mississippian Vicente Guerrero and the Pennsylvanian Del Monte Formations. The studied rhyolites display geochemical characteristics corresponding to high-K, low-Sr, and S-type granitoid rocks that may have been produced by upper-crustal anatexis from a source similar to that of the Novillo Complex. New LA-ICP-MS U–Pb geochronological analysis on zircons separated from the Aserradero Rhyolite yielded Early to Middle Mississippian crystallisation ages of 347.8 ± 2.7 Ma and 340.7 ± 3.6 Ma, confirming that this acidic unit is in its original stratigraphic position despite the pervasive deformation of the Tamatán Group. Based on the correlation with other Carboniferous–Early Permian magmatic complexes in Mexico and Central America, it is suggested that the Aserradero Rhyolite represents an early stage of a precollisional Carboniferous–Permian peri-Gondwanan arc, occurring also in the Las Delicias, Oaxaquia, the Acatlán Complex, the Maya Block, as well as in the buried crystalline basement along the Western Gulf of Mexico. The assembly of the Precambrian and Palaeozoic basement units from the Huizachal–Peregrina Anticlinorium were integrated with the Ciudad Victoria Block, which was dismembered from Oaxaquia and their peripheral units during the Upper-Jurassic Gulf of Mexico opening. [ABSTRACT FROM AUTHOR]

Felsic tuff as a direct fallout deposit is known from one small area in the Kyrenia Range, north Cyprus, within deep-sea terrigenous turbidites. Nearby tuffaceous siltstones contain compositionally similar felsic volcanic rocks (c. 5–10%), mixed with terrigenous material. Sedimentary evidence indicates that the fallout tuff was variable reworked locally, whereas the tuffaceous siltstones are interpreted as turbidites mixed with terrigenous material derived from Anatolia. U–Pb dating of zircons that were extracted from a sample of relatively homogeneous tuff yielded a dominant age of 16.64 ± 0.12 Ma (Burdigalian). Zircon trace-element analysis indicates predominant derivation from within-plate-type felsic magma. Whole-rock chemical analysis of the tuffaceous sediments as a whole is compatible with a felsic arc source, similar to the post-collisional magmatism within Anatolia. Regional comparisons suggest that the nearest volcanism of similar age and composition is located c. 500 km away, within the Kırka area (Eskişehir region) of the Western Anatolia Volcanic Province. Evidence of tephra dispersal in the western Mediterranean region and climatic modelling suggests E-wards prevailing winds and therefore tephra transport over southern Anatolia and adjacent areas during early Miocene time. The north Cyprus tuffs could represent powerful Minoan (Plinian)-type eruptions in western Anatolia, coupled with SE-wards tephra transport during and soon after the onset of post-collisional magmatism. [ABSTRACT FROM AUTHOR]

The Paleozoic strata are widely distributed in the northwest of the Ordos Basin, and the provenance attributes of the basin sediments during this period are still controversial. In this paper, the detrital zircon LA-MC-ICPMS U-Pb age test was conducted on the drilling core samples of the Shanxi Formation of the Upper Paleozoic in the Otuokeqi area of the Ordos Basin, and the provenance age and the characteristic of the Shanxi formation in the Otuokeqi area in the northwest were discussed. The cathodoluminescence image shows that the detrital zircon has a clear core-edge structure, and most of the cores have clear oscillatory zonings, which suggests that they are magmatic in origin. Zircons have no oscillatory zoning structure that shows the cause of metamorphism. The age of detrital zircon is dominated by Paleoproterozoic and can be divided into four groups, which are 2500~2300 Ma, 2100~1600 Ma, 470~400 Ma, and 360~260 Ma. The first two groups are the specific manifestations of the Precambrian Fuping Movement (2.5 billion years) and the Luliang Movement (1.8 billion years) of the North China Craton. The third and fourth groups of detrital zircons mainly come from Paleozoic magmatic rocks formed by the subduction and collision of the Siberian plate and the North China plate. The ε Hf t value of zircon ranges from -18.36 to 4.33, and the age of the second-order Hf model T DM 2 ranges from 2491 to 1175 Ma. The source rock reflecting the provenance of the sediments comes from the material recycling of the Paleoproterozoic and Mesoproterozoic in the crust, combined with the Meso-Neoproterozoic detrital zircons discovered this time, indicating that the provenance area has experienced Greenwellian orogeny. [ABSTRACT FROM AUTHOR]

In the present work, a natural zircon megacryst SA02 (the exact provenance unknown) is investigated as a new potential reference material for U–Pb geochronology and Hf–O isotopic composition analysis via micro-beam methods. The precise and accurate U–Pb age is determined by the chemical abrasion isotope dilution thermal ionization mass-spectrometry (CA-ID-TIMS) method. The resultant mean 206Pb/238U date is 535.10 ± 0.24 Ma (2s, n = 2), interpreted as the crystallization age of the zircon megacryst. The mean ID-TIMS 206Pb/238U date of 533.7 ± 3.7 Ma (2s, n = 8) is recommended as the working value for micro-beam analyses when using untreated SA02 zircon grains as the primary reference material. 206Pb/238U dates of 533.0 ± 6.2 Ma (2s, n = 57) and 534 ± 8 Ma (2s, n = 101) obtained by secondary ion mass spectrometry (SIMS) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) respectively are reproducible and in agreement with the results of ID-TIMS within < 0.3% relative analytical errors. Solution data of Hf isotope compositions measured by multi-collector ICP-MS (MC-ICP-MS) from SA02 zircon yield a mean 176Hf/177Hf of 0.282287 ± 0.000016 (2s, n = 31), which is recommended as a reference value for microbeam analysis. Hf isotope analyses by LA-MC-ICP-MS yield homogeneous Hf isotopic compositions with a mean 176Hf/177Hf of 0.282289 ± 0.000033 (2s, n = 142) identical to the solution value. The mean δ18O value measured by laser fluorination is 6.03 ± 0.28‰ (2s, n = 13), which is consistent with the result of SIMS analysis. [ABSTRACT FROM AUTHOR]

Apatite and zircon (U-Th) = He thermochronological data are obtained through a combination of crystal selection, He content measurement by crystal heating with analysis using noble gas mass spectrometry, and measurement of U, Th, and Sm contents by crystal dissolution as well as solution analysis using inductively coupled plasma mass spectrometry (ICP-MS). This contribution documents the methods for helium thermochronology used at the GEOPS laboratory, Paris-Saclay University, between 2007 and the present that allow apatite and zircon (U-Th) = He data to be obtained with precision. More specifically, we show that the He content can be determined with precision (at 5 %) and accuracy using a calibration of the He sensitivity based on the Durango apatite, and its use also appears crucial to check for He and U-Th-Sm analytical problems. The Durango apatite used as a standard is therefore a suitable mineral to perform precise He calibration and yields (U-Th) / He ages of 31.1±1.4 Ma with an analytical error of less than 5% (1σ). The (U-Th) / He ages for the Fish Canyon Tuff zircon standard yield a dispersion of about 9% (1σ) with a mean age of 27.0±2.6 Ma, which is comparable to other laboratories. For the long-term quality control of the (U-Th) / He data, attention is paid to evaluating the drift of He sensitivity and blanks through time as well as that of (U-Th) / He ages and Th / U ratios (with Sm / Th when possible), all relying on the use of Durango apatite and Fish Canyon Tuff zircon as standards. [ABSTRACT FROM AUTHOR]

The same unetched and chemically etched apatite crystals from five rock samples were dated by the U--Pb method via laser ablation inductively coupled plasma mass spectrometry (LA--ICP-MS). The objective of this study is to test whether chemical etching required for apatite fission track analysis impacts the precision and accuracy of apatite U--Pb geochronology. The results of this experiment suggest that etching has insignificant effects on the accuracy of apatite U--Pb ages obtained by LA--ICP-MS. Therefore, LA--ICP-MS is reliable for U--Pb analysis as part of apatite fission track and U--Pb double dating. [ABSTRACT FROM AUTHOR]

The South Altyn Block (SAB), located along the southern margin of the Altyn Tagh in Qaidam Basin, has a significant relationship with the tectonics of the Qaidam Basin basement. This study presents the petrological features, geochemical compositions, and zircon U–Pb and Hf isotope data of four granitic plutons from the eastern segment of the SAB to constrain the petrogenesis and tectonic setting of this region during the Palaeozoic. Basing on previous U–Pb dating results, the zircon U–Pb analysis in this study suggests that Palaeozoic magmatic events can be subdivided into four episodes: Late Cambrian (approximately 502 Ma), Late Ordovician (approximately 444 Ma), Early Devonian, and Middle Permian (approximately 271 Ma). The Palaeozoic granitoids were derived mainly from Neoproterozoic juvenile crustal components, with minor palaeoproterozoic ancient materials. The S‐ and I‐type granitoids in Late Cambrian indicate a compressional tectonic environment with respect to subduction, and A‐type granitoids suggest post‐collision regime. The Late Ordovician granodiorites of A‐type imply typical magmatism within a post‐collision extensional setting. Ascribing to the subduction of Palaeo‐Tethys Ocean during the Devonian, S‐type granites were emplaced in the Early Devonian accompanied with the crust thickening. The Middle Permian magmatic events include a series of S‐type granitoids, demonstrating the setting of oceanic subduction along with the closure of the Palaeo‐Tethys Ocean. [ABSTRACT FROM AUTHOR]

Post-orogenic alkaline intrusions from the Sulu Orogenic Belt of eastern North China Craton consist of A-type granites. In this study, we report U–Pb zircon ages, geochemical data, Sr–Nd–Pb, and zircon Hf isotopic data for these rocks. The LA-ICP-MS U–Pb zircon analyses yield consistent ages ranging from 127.1 ± 2.4 to 119.5 ± 4.8 Ma for four samples. The alkaline rocks are characterized by high total alkalis (K2O + Na2O = 8.32–10.11 wt%), light rare-earth element enrichment, and heavy rare-earth element depletion, with a wide range (La/Yb)N values (20–48), moderate negative Eu anomalies (Eu/Eu* = 0.50–0.74), enrichment in large-ion lithophile elements (LILEs, i.e., Rb, Th, U and Pb), and depletion in Ba, Sr and high field strength elements (HFSEs, i.e., Nb, Ta, and Ti), high (87Sr/86Sr)i ranging from 0.708 to 0.7089, low εNd (t) values from −19.4 to −16.8, (206Pb/204Pb)i = 16.751 – 16.935, (207Pb/204Pb)i = 15.381−15.535, (208Pb/204Pb)i = 37.472–37.838, negative εHf (t) values between −21.3 and −25.7 for the magmatic zircons, and larger TDM2 model ages from 2.5 to 2.8 Ga. These results suggest that the rocks were derived from a common enriched lithospheric mantle source that was metasomatized by foundered lower crustal eclogitic materials before magma generation. Furthermore, the geochemical and isotopic feature implies that the primary magma of these rocks originated through partial melting of ancient lithospheric mantle that was variably hybridized by melts derived from lower crust eclogite. These rocks in this study may have been generated by subsequent fractionation of potassium feldspar, plagioclase, ilmenite, and/or rutile. However, negligible crustal contamination occurred during the diagenesis process. [ABSTRACT FROM AUTHOR]

The Sanshilipu monzogranites is located in the northern margin of the South Qinling Block, with an outcrop of about 10 km2, and as an intrusion into Palaeozoic Danfeng ophiolitic mélange. The samples consist mainly of plagioclase, K‐feldspar, quartz, biotite, and minor titanite, apatite, magnetite, with contents of SiO2 (61.73–68.49%), Al2O3 (14.58–16.61%), K2O + Na2O (5.79–8.87%), MgO (1.07–2.91%), and low TiO2 (0.55–0.83%), similar to those of I‐type granite. They also show high concentrations of LREE, Pb, and Sr, slightly negative Eu, but low HREE, Nb, Ta, and Y. High Sr and Sr/Y, low Y characteristics are similar to those of adakite. High precision LA‐ICP‐MS U–Pb dating and trace element analysis of zircon in the Sanshilipu granite yielded a concordant age of 205 ± 1 Ma. This age is apparently younger than the closure age of the Mian‐Lue Ocean (242–221 Ma). We propose that the Sanshilipu monzogranites formed by magma mixing of thickened lower crust and limited mantle‐derived mafic magma during post‐collision of the South China and North China blocks. [ABSTRACT FROM AUTHOR]

In the supercontinent of Rodinia, Baltica occurred next to Amazonia, then the two drifted away when Rodinia broke up. By the end of the Neoproterozoic, Baltica became an independent continent. At that time, Timanide orogen developed at its modern northeastern margin. In most paleogeographical reconstructions, the opposite (SW, Tornquist) edge faced the Tornquist Ocean and remained just a passive margin till the arrival of the Gondwana-born East Avalonia in the late Ordovician. However, preliminary isotopic studies of detrital zircons from the Tornquist passive margin succession hinted that rock components of Gondwana derivation reached Baltica already in the early Cambrian. In this paper, we examine 18 drill-cores of Ediacaran-Cambrian and Ordovician siliciclastic rocks from the tectonostratigraphic units along the SW–NE transect from Upper Silesia (USB) via Małopolska (MB) and the Holy Cross Mts (HCM) to the East European Platform (EEP), SE Poland, in terms of the provenance data gained from the LA-ICP-MS and SHRIMP analyses of 32 zircon samples. Rocks from all the units revealed abundant Cadomian 0.7–0.55 Ga detrital zircons (15–50% of the total analyzed grains) and other grains that yielded peaks at 0.9–1.2, 1.4–1.6, 1.8–2.2, 2.7–3.0 Ga assignable to Baltica rather than Amazonia. Such age spectra in the USB, HCM and EEP prove the proximity of peripheral (peri-Gondwanan) fragments of the Cadomian orogen to Baltica. These fragments formed the Teissyere-Tornquist Terrane Assemblage (TTA) that obliquely docked and overrode the thinned southwestern edge of Baltica which earlier accumulated Neoproterozoic rift and passive margin deposits. Our data show that in the late Ediacaran-early Cambrian, parts of the Cadomian orogenic belt became accreted to Baltica. [ABSTRACT FROM AUTHOR]

Although continental crust is characterized by the widespread occurrence of granitoids, the causal relationship between continental crust growth and granitic magmatism still remains enigmatic. While fractional crystallization of basaltic magmas (with or without crustal contamination) and partial melting of mafic lower crust are two feasible mechanisms for the production of granitoids in continental arc regions, the problem has been encountered in discriminating between the two mechanisms by whole-rock geochemistry. This can be resolved by an integrated study of zircon U-Pb ages and Hf-O isotopes together with whole-rock major-trace elements and Sr-Nd-Pb isotopes, which is illustrated for Mesozoic granitoids from the Gangdese orogen in southern Tibet. The results provide geochemical evidence for prompt reworking of the juvenile mafic arc crust in the newly accreted continental margin. The target granitoids exhibit high contents of SiO2 (65.76-70.75 wt%) and Na2O + K2O (6.38-8.15 wt%) but low contents of MgO (0.19-0.98 wt%), Fe2O3 (0.88-3.13 wt%), CaO (2.00-3.82 wt%), Ni (<5.8 ppm), and Cr (⩽10 ppm). They are enriched in large ion lithophile elements, Pb, and light rare earth elements but depleted in high field strength elements. The granitoids are relatively depleted in whole-rock Sr-Nd isotope compositions with low (87Sr/86Sr)i ratios of 0.7043-0.7048 and positive Nd(t) values of 0.5-2.6, and have relatively low 207Pb/204Pb and 208Pb/204Pb ratios at given 206Pb/204Pb ratios. Laser ablation-inductively coupled plasma-mass spectrometry and secondary ion mass spectrometry U-Pb dating on synmagmatic zircons yield ages of 77 ± 2-81 ± 1 Ma in the Late Cretaceous for their emplacement. Relict zircons have two groups of U-Pb ages in the late Mesozoic and the late Paleozoic, respectively. The whole-rock Sr-Nd isotopes in the granitoids are quite similar to those of Late Cretaceous mafic rocks in the Gangdese batholith. In addition, both synmagmatic zircons and relict zircons with Late Cretaceous U-Pb ages exhibit almost the same Hf-O isotope compositions to those of the slightly earlier mafic rocks. All these observations indicate that the granitoids were mainly derived from partial melting of the juvenile mafic arc crust. Therefore, reworking of the juvenile mafic arc crust is the mechanism for the origin of isotopically depleted granitoids in southern Tibet. It is this process that leads to differentiation of the juvenile mafic arc crust toward the felsic lithology in the continental arc. In this regard, the granitoids with depleted radiogenic isotope compositions do not necessarily contribute to the crustal growth at convergent plate boundaries. [ABSTRACT FROM AUTHOR]

Zirconium (Zr) plays a key role in the development of phases like zircon (ZrSiO4) and baddeleyite (ZrO2) in magmatic systems. These minerals are crucial for the study of geologic time and crustal evolution, and their high resistivity to weathering and erosion results in their preservation on timescales of billions of years. Although zircon and baddeleyite may also preserve a robust record of Zr isotope behavior in high-temperature terrestrial environments, little is known about the factors that control Zr isotope partitioning in magmatic systems, the petrogenetic significance of fractionated compositions, or how these variations are recorded in Zr-rich accessory phases. Here, we describe a new analytical protocol for accurately determining the Zr stable isotope composition of zircon by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS), using the double-spike method to correct for procedural and instrumental mass bias. We apply this technique to test whether zircon crystallization in carbonatite magmatic systems is a driver of Zr isotope fractionation by interrogating the internal zonation of a zircon megacryst from the Mud Tank carbonatite (MTUR1). We find the MTUR1 megacryst to lack internal zoning within analytical uncertainties with a mean μ94/90ZrNIST = −55 ± 28 ppm (2 SD, n = 151), which suggests that zircon crystallization is not a driver of Zr isotope fractionation in carbonatite magmas. This observation is in stark contrast with those made in silicate magmatic systems, raising the possibility that the bonding environment of Zr4+ ions may be fundamentally different in carbonatite vs. silicate melts. Because of its remarkable homogeneity, the MTUR1 megacryst is an ideal natural reference material for Zr isotopic analysis of zircon using both solution and spatially resolved methods. The reproducibility of a pure Zr solution and our chemically purified zircon fractions indicate that the external reproducibility of our method is on the order of ±28 ppm for μ94/90Zr, or ±7 ppm per amu, at 95% confidence. [ABSTRACT FROM AUTHOR]

Quantifying the timescales of Archean ultrahigh temperature (UHT) metamorphism is essential for constraining the style of plate tectonics on the early Earth. However, such timescales can be difficult to quantify, due to the antiquity of Archean rocks and the extreme thermal conditions of UHT metamorphism. We constrain the timescales of Archean UHT metamorphic processes recorded by a single rock sample from the Pikwitonei granulite domain (northwestern Superior Province), through the integration of two U–Pb zircon petrochronologic techniques. In this study we combine: (1) high-spatial resolution laser ablation split-stream inductively coupled mass spectrometry (LASS) on in situ zircon (in thin section) and hand-picked zircon; and (2) high-precision isotope dilution thermal ionization mass spectrometry (ID-TIMS) analyses on microsampled fragments from the same hand-picked zircon analysed by LASS. Phase equilibria modelling and Zr-in-rutile thermometry suggest the rock followed a P–T path characterized by decompression at > 960 °C, followed by near-isobaric cooling at ∼0·8 GPa. In situ LASS zircon analyses could be interpreted to record zircon growth at broadly ∼2665 Ma, though the large uncertainties on isotopic dates make potentially distinct growth episodes difficult to distinguish. ID-TIMS U–Pb dates of zircon fragments reveal a polyphase zircon growth history over a 24 Ma duration, from 2673 to 2649 Ma. Zircon trace element compositions, textures, and microstructural relationships, as well as evaluation of zircon-garnet equilibrium, suggest zircon grew during melt crystallization, after UHT decompression and garnet resorption. Variable Ti concentrations within zircon domains indicate: (1) zircon crystallized through the temperature interval of ∼875 °C to ∼730 °C, potentially in isolated rock domains with variable zircon saturation temperature; and/or (2) zircon crystallized over a narrower temperature interval in isolated rock domains with variable a TiO2 and/or a SiO2. Collectively, the data suggest the west-central Pikwitonei granulite domain reached peak UHT conditions prior to 2673 Ma, after which suprasolidus conditions in the lower crust persisted for at least 24 Ma. Such an interpretation would be impossible if based on either the LASS or ID-TIMS zircon data alone, which highlights the utility of applying both techniques in tandem to constrain metamorphic timescales in ancient UHT terranes. [ABSTRACT FROM AUTHOR]

• In the Ontario gneiss belt, Nd isotope boundaries can be identified in the field. • These isotope boundaries provide the best constraint on major crustal structures. • Spatial control from Nd isotope mapping complements age control from U-Pb dating. • Detrital zircon Hf model ages rather than U-Pb ages yield crustal extraction ages. With the increasing availability of U-Pb-Hf isotope analysis of zircon suites, does whole-rock Nd isotope analysis still have a role to play in mapping Precambrian gneiss terranes? I answer this question by examining the Ontario Gneiss Belt of the Grenville Province, and show that Nd isotope mapping still has a vital role to play in studies of Precambrian crustal evolution. Although U-Pb-Hf isotope analysis of detrital zircons can provide large suites of crystallization ages and epsilon Hf values, the poor spatial control of these data means that precise geographical control of crustal structure from Nd isotope mapping is still important. I demonstrate this for several regions of the Ontario Gneiss Belt, including northern Algonquin Park, western Lake Nipissing and Georgian Bay. In all these regions, mapping complex geographical patterns of crustal formation ages allows detailed documentation of large-scale crustal structure. Only with such an accurate understanding of crustal structure can accurate models of tectonic evolution be constructed in a complex, deeply exhumed orogenic belt such as the Grenville Province. [ABSTRACT FROM AUTHOR]

In order to understand the sedimentary age and geotectonic environment characteristics of the Ruyang Group in geological history, this study, with the LA-ICP-MS method, focuses on the study of U-Pb isotope geochronology and geotectonic environment analysis of detrital zircons in the bottom of Xiaogoubei Formation of Ruyang Group in Daimeishan of Henan. Results show that the ages of detrital zircons of Xiaogoubei Formation range from 1720 Ma to 2727 Ma, the youngest detrital zircon age near the harmonic line is 1720 ±65 Ma, the main peak age is 2547 Ma, and the second peak ages include 2178 Ma and 1832 Ma. Therefore, we consider that the lower age limit of Xiaogoubei Formation is ~1720 Ma; the sediment sources of Xiaogoubei Formation mainly come from the geological bodies of the interior of the North China craton in the late Neoarchean, early Paleoproterozoic, middle Paleoproterozoic, late Paleoproterozoic and early Neoproterozoic. At the same time, the detrital zircon age of samples has a good response relationship with the Precambrian geological events in North China Craton, which reveals the then construction environment. [ABSTRACT FROM AUTHOR]

• U–Pb data from fast pulse LA-ICP-MS is equivalent with conventional U–Pb analysis. • Provenance of the largely unexposed Yeneena Basin revealed. • Exotic sources support a transcontinental transport system across Rodinia. Over ten thousand detrital zircon U–Pb analyses on thirty four samples were undertaken using a fast pulse laser ablation protocol from the Neoprotoerozoic rocks of the largely unexposed Yeneena and northwestern Officer Basins in Western Australia. In addition, conventional laser ablation detrital zircon U–Pb geochronology was carried out on three of the samples. A comparison of the two datasets demonstrated that no statistical significant difference was observed in the detrital zircon spectra between the two techniques. The results of the detrital zircon analyses reveal that after an intial pulse of material dominated by Archean detritus the sediment are dominated by Mesoproterozic sources. This indicates that there is little variation in source materials within and between the identified formations. The major age peaks coincide with magmatic rock ages from within Australia. The results indicate that either the Palaeoproterozoic and Mesoproterozoic terranes remained sources throughout the deposition of the Yeneena and northwestern Officer Basins during the Neoproterozoic, or that recycling of zircons occurred within a quasi-closed system for the duration of sedimentation. The remaining 10 % of grains are difficult to reconcile with magmatic suites of any significant volume within Australia. However, when considering the broader palaeogeographic context at the time the sediments are inferred to have been deposited, rocks from Dronning Maud Land and the Kalahari Craton can supply grains of appropriate ages and are consistent with the known paleocurrent directions. This work demonstrates that there is no significant disadvantage in the application of the fast pulse technique when applied to the collection of U–Pb detrital zircon datasets for the purpose of detrital zircon fingerprinting. However, there is a large upside related to the significant amount of data that can be collected for a given amount of time compared to other more conventional techniques. [ABSTRACT FROM AUTHOR]

• Combination of dating techniques improves accuracy of determination. • Spurious detrital zircon dates post-dating crystallization found by LA-ICP-MS. • LA-ICP-MS studies should routinely chemically abrade zircon prior to analyses. • The oldest Paleoproterozoic glacial event is dated to 2423.1 ± 1.0 Ma. • Anoxic atmospheric settings from the Koegas Subgroup are dated to 2451.5 ± 2.5 Ma. The Transvaal Supergroup, on the Kaapvaal Craton in South Africa, is widely accepted as one of the best-preserved sedimentary archives to constrain planetary-scale environmental changes during the late Archean and early Proterozoic, yet the sedimentation age for certain stratigraphic intervals remains poorly constrained. To improve the temporal control on some of the first-order global changes recorded in these rocks, we carried out U-Pb analyses of detrital zircon populations from several clastic and volcano-clastic sedimentary units of the Transvaal Supergroup. We applied the Chemical Abrasion-Isotope Dilution-Thermal Ionization Mass Spectrometry (CA-ID-TIMS) technique on detrital and volcanic zircon populations that had been previously screened using the Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) technique. We report new maximum depositional age estimates for the Pannetjie (2456.6 ± 7.0 Ma), the Heynskop (2451.5 ± 2.5 Ma), the Makganyene (2423.1 ± 1.0 Ma) and the Hekpoort formations (2248.0 ± 1.1 Ma). A ca. 2.25 Ga-old cluster of LA-ICP-MS analyses in the Makganyene Formation was identified to be spurious, since it was completely removed during the chemical abrasion. Thus, we speculate that circulation of hydrothermal fluids and associated Pb-loss from a radiation-damaged lattice during the emplacement of the much younger Hekpoort Formation or possibly the Ophthalmia Orogeny, recorded in Western Australia, may have reset the U-Pb system of this zircon population. This implies that the accurate maximum depositional age of the Makganyene Formation is ca. 2.42 Ga instead, which denotes the age of the oldest glacial event of global extent during the Paleoproterozoic. Therefore, we suggest that the combination of both dating techniques is essential to ensure accurate maximum depositional age constraints for ancient detrital sedimentary rocks. Additionally, our data provides temporal constraints on a period characterized by major fluctuations in atmospheric oxygen. Finally, and supporting the complex nature of the Paleoproterozoic, linkages between widespread glaciations and atmospheric oxygen fluctuations remain to be explored. [ABSTRACT FROM AUTHOR]

The Terreneuvian Series of the early Cambrian records the first major diversification phase of the canonical Cambrian explosion. However, a paucity of precise radio-isotopic ages for key stratigraphic horizons has resulted in a poor temporal calibration of fossil lowest occurrences (LO) and corresponding rates of evolution throughout the Terreneuvian. Here we present integrated SIMS and CA-ID-TIMS U-Pb analyses on zircons from the basal Shuijingtuo Formation in the Yangtze Gorges area, South China. The dating results provide a depositional age of 526.43 ± 0.54 Ma for the basal Shuijingtuo Formation, and compiled detrital zircon U-Pb dates from the Ediacaran-Cambrian transitional strata in the Yangtze Gorges area indicate their local provenances. The new high-precision date provides a minimum age constraint on the ZHUCE (Zhujiaqing positive carbon isotope excursion) and LOs of Watsonella crosbyi and Aldanella attleborensis in South China, and allows correlation of ZHUCE with either 5.5p or 5p/I′ in Siberia and Morocco. We construct two models of the Ediacaran-Cambrian transitional timescale based on the two alternative correlations of the ZHUCE. The first model correlates the ZHUCE with 5.5p and yields significantly diachronous LOs of W. crosbyi and A. attleborensis between the Siberian Platform and South China. In contrast, the second and our preferred model equates ZHUCE with 5p/I′ and implies relatively synchronous LOs of W. crosbyi and A. attleborensis between the Siberian Platform and South China. In the preferred model, the couplet of ZHUCE/5p/I′ and LOs of W. crosbyi and A. attleborensis serves as a reliable combination to bracket the base of Cambrian Stage 2. • The basal Shuijingtuo ash bed at Yanjiahe section is dated at 526.43 ± 0.54 Ma. • The ZHUCE is correlated to either 5.5p or 5p/I′ in Siberia and Morocco. • Potential markers for the Cambrian Stage 2 are evaluated based on the new date. [ABSTRACT FROM AUTHOR]

The Guleman Ophiolite is located in the southeast of Turkey and mainly consists of harzburgites and dunites hosting economically viable chromitite bodies, and lesser amounts of cumulate and isotropic gabbro, diabase dykes, pyroxenite and locally plagiogranite. This study reports the combined whole-rock geochemical and radiogenic isotope (Sr and Nd) data for gabbro and diabase dykes, and in-situ zircon U-Pb geochronological data for plagiogranite and gabbro from the Guleman Ophiolite. Two different geochemical groups were determined based on immobile minor and trace elements, and radiogenic isotope characteristics of gabbro and diabase dykes investigated here. The first group is represented by boninites and displays highly depleted elemental patterns compared to NMORB, and spoon-shaped rare earth element profiles. Contrarily, the second group resembles back-arc basin basalts and is characterized by NMORB-like rare earth element patterns associated with negative Nb anomalies. The boninitic samples are characterized by less radiogenic 143Nd/144Nd (i) (0.51229 to 0.51267; ƐNd = −4.8 to +2.7) and more radiogenic 87Sr/86Sr (i) (0.70549 to 0.70758) isotope compositions compared to the back-arc basin basalt-like samples (143Nd/144Nd (i) = 0.51289 to 0.51296; ƐNd = +7.0 to +8.4; 87Sr/86Sr (i) = 0.70496 to 0.70629), indicating derivation from distinct and/or heterogeneous mantle source regions within a supra-subduction zone. The LA–ICP–MS zircon U-Pb analyses yielded concordant late Cretaceous ages for gabbro (82 ± 2.9 Ma) and plagiogranite (79.9 ± 0.8 Ma) samples. The overall geochemical, isotopic and geochronological data presented here suggest that the Guleman Ophiolite consists of forearc and initial back-arc spreading sections of oceanic crust, which may have been formed in an intra-oceanic subduction zone within the Berit Ocean (northern branch of the southern Neo-Tethyan ocean). Moreover, the generation of continental arc magmatism (i.e. Baskil and Esence Granitoids) was well-documented on the active margin of the Malatya-Keban Metamorphics to the north. Therefore the closure of this oceanic basin should have resulted in multiple coeval northward subduction events during the late Cretaceous. • The Guleman Ophiolite could have been formed in an intra-oceanic subduction zone. • The mafic rocks show boninitic and back arc-like geochemical signatures. • Late Cretaceous ages of 79 Ma and 82 Ma are reported for plagiogranite and gabbro. • A multiple northward subduction model is plausible for the Berit Ocean. [ABSTRACT FROM AUTHOR]

During LA-ICP-MS analysis,the key factor influencing data accuracy of sample analysis is whether the sample can be uniformly delivered from the laser sample chamber to the torch of the ICP-MS.An external container between LA and ICP-MS and a multi-channel rotary sampling cell,which can effectively eliminate the sample position effect during the laser ablation was designed for the study reported in this paper.The pattern of aerosol delivered to ICP-MS is approximately continuous and at the same time,this can greatly improve the stability.Under optimal conditions,using 91500 as external standard,the standard zircons GJ-1,Ple ovice,TEMROA and QH yield U-Pb ages of 604±3 Ma(2δ,MSWD=1.2),337±1 Ma(2δ,MSWD=1.18),419±3 Ma(2δ,MSWD=0.15) and 161±1 Ma(2δ,MSWD=0.6),respectively,which agree well with the previously reported ID-TIMS and SHRIMP ages.For the same conditions,using NIST610 as external standard,most trace element results of the glass standards NIST612 and BHVO-2G fall within 10% range of the reference values.The 207Pb/206Pb weighted mean age of zircons from the Tianshan Orogen of Xinjiang is consistent with the previous SHRIMP U-Pb age within uncertainty.This method can effectively reduce the elemental fractionation effects and improve the reliability of the analytical data. [ABSTRACT FROM AUTHOR]

The article presents study on isotope composition and isomorphic admixture in zircon stimulated treatment in the evolution of the alkaline-carbonatite magmatic system of Il'meno-Vishnevogorskii Complex (IVC) in Urals, Russia. It mentions the use of laser ablation inductively coupled plasma mass spectrometry ((LA-ICP-MS), and trace elements content in zircons of the Il'meno-Vishnevogorskii complex. It adds zircon revealed in miaskite and carbonatite of the IVC.

A large number of Paleoproterozoic borate deposits are hosted by the lower units of a volcanic-sedimentary sequence in Liaoning Province, northeastern China, and are a major source of boron in China. The ore-bearing wall rocks in the deposits are serpentinized ultrabasic rocks and carbonates, with layered leptynites, leptites, amphibolites, and migmatites adjacent to the ore. Both the borate ores and country rocks contain tourmaline, although the country rocks have much lower abundances of the mineral. Based on in situ boron isotope measurements using laser ablation–multi-collector–inductively coupled plasma–mass spectrometry (LA–MC–ICP–MS), boron isotope data show that: (1) δ 11 B values of borate ores range from + 6.8‰ to + 13.9‰ (mean + 10.8‰); (2) tourmalines from the borate ores have δ 11 B values from + 9.5‰ to + 12.7‰; and (3) the wall rocks within the borate ores yield slightly lower δ 11 B values ranging from + 5.7‰ to + 7.6‰, and those outside the deposits from − 9.9‰ to − 5.9‰. Positive δ 11 B values in borates as well as in tourmalines inside the mining area indicate that boron in these Paleoproterozoic borate deposits was derived from marine evaporites. δ 34 S V-CDT (where V-CDT is Vienna Canyon Diablo Troilite) values of borate ores, serpentinized marbles, and anhydrites range from + 16.1‰ to + 24.7‰, whereas δ 13 C V-PDB (where V-PDB is Vienna Pee Dee Belemnite) values of marbles range from + 3.2‰ to + 5.9‰. These isotopic characteristics are interpreted to reflect formation in a marine evaporative environment. LA–MC–ICP–MS zircon weighted 207 Pb/ 206 Pb ages of leptite and serpentinized olivine basalt from the hanging wall of the borate deposits are 2139 ± 13 Ma and 2130 ± 19 Ma, respectively. Therefore, the (~ 2.2 Ga) borate deposits may have originated from marine evaporative boron-bearing sediments, which were interbedded within bimodal volcanic rocks during the early stages of development of the Liaoji rift. [ABSTRACT FROM AUTHOR]

The direct age dating of individual mineral components in sedimentary rocks through the analysis of radiogenic parent and daughter isotopes has been routinely applied to better understand sediment provenance and dispersal patterns for several decades. Time, labor, and financial cost--sadly, not scientific inquiry--are typically the determining factors in the number of analyses run for a sedimentary rock sample during provenance investigations. The number of observations reported for detrital zircon provenance investigations using secondary ion mass spectrometers SIMS and laser-ablation inductively-coupled-plasma mass-spectrometers LA-ICP-MS typically range from n = 60-120. In this range, minor, but commonly geological relevant, age components are commonly not identified from the sample aliquot. In addition, the relative proportions of zircon ages from within an age component are typically unreliable for intersample comparisons because the relative proportions of ages from aliquots of n = 60-120 may poorly reflect the 'true' proportions of ages from a sample. This study investigates the practicality and usefulness of generating large-n (n = 300-1000) datasets. A LA-MC-ICP-MS and LA-SC-ICP-MS were used to generate four n z 1000 datasets. We show that precision large-n U-Pb detrital zircon datasets can be created using LA-ICP-MS with total sample-run analysis times that are on par with more traditional studies. At best, most provenance investigations based on n = 60-100 have been statistically limited to identifying principle age components. The statistical robustness on n ≈ 1000 datasets not only significantly increase the probability that exotic or low abundance age components (i.e., f < 0.05) are identified in detrital samples, but it allows for the quantitative comparisons between relatively high abundance age components in samples. This potentially transformative outcome of large-n has the potential to stimulate new avenues of research in sedimentology and tectonics. [ABSTRACT FROM AUTHOR]

Many studies now acknowledge the occurrence of systematic discrepancies between U-Pb ages determined in zircons in situ by LA-ICP-MS and the benchmark analytical method ID-TIMS. In this study, we present detailed investigations into the ablation characteristics of zircons that suggest an underlying mechanism responsible for these age biases relative to ID-TIMS. Confocal laser scanning microscopy of laser ablation pits reveals that there are small but significant differences in the amount of material removed by the laser between different zircons. Based on numerous pit depth and LA-ICP-MS 206Pb/238U ratio measurements of a suite of natural zircon reference materials and samples, we demonstrate that a systematic age bias is strongly correlated with the offset in ablation rates between the primary reference material and sample zircons. We offer further insights concerning the effects of thermal annealing on the ablation behaviour of zircons and demonstrate that, although there is a change in laser ablation rates for annealed zircons, the variations between different zircons are not eliminated. Finally, we show that slight variations in laser focus also influence the ablation behaviour of zircons and may further degrade the accuracy of U-Pb age determinations. [ABSTRACT FROM AUTHOR]

Zircon Pb-U dating has become a key technique for answering many important questions in geosciences. This paper describes a new LA-ICP-MS approach. We show, using previously dated samples of a large quaternary rhyolitic eruption in the Kos-Nisyros volcanic centre (the 161 ka Kos Plateau Tuff), that the precision of our LA-ICP-MS method is as good as via SHRIMP, while ID-TIMS measurements confirm the accuracy. Gradational age distribution over >140 ka of the Kos zircons and the near-absence of inherited cores indicate near-continuous crystallisation in a growing magma reservoir with little input from wall rocks. Previously undated silicic eruptions from Nisyros volcano (Lower Pumice, Nikia Flow, Upper Pumice), which are stratigraphically constrained to have happened after the Kos Plateau Tuff, are dated to be younger than respectively 124 ± 35 ka, 111 ± 42 ka and 70 ± 24 ka. Samples younger than 1 Ma were corrected for initial thorium disequilibrium using a new formula that also accounts for disequilibrium in 230Th decay. [ABSTRACT FROM AUTHOR]

The about 2055-Ma-old mafic to ultramafic Uitkomst Complex in the Mpumalanga Province of South Africa hosts the low-grade-large-tonnage Ni-Cu-PGE deposit, Nkomati. The complex is regarded to represent a satellite to the Bushveld Complex and a feeder to an eroded magmatic reservoir in the southeast. Aeromagnetic surveys and previous drilling indicated an overall northwestern-downdip extension of the complex, but the question is to what extent and in which expression can the complete intrusion be found under cover in the northwest? Answering this, a mineralogical, geochemical and geochronological investigation of a borehole intersection of the whole complex at Little Mamre was carried out, using petrography, XRF, EPMA and LA-ICP-MS U–Pb analyses of zircons for age determination. Although the total thickness of the rock units is larger than to the southeast, emplacement, litho- and mineral chemistry trends, expression of alteration mineralogy and style of sulphide mineralisation are similar. The amount of sulphide mineralisation is on average less than in the southeast. The upper ultramafic unit contains, more frequently, pegmatoidal sections, and the Chromitiferous Harzburgite unit has less massive chromitite layers than the southeastern parts of the complex, whereas the gabbro(-norite) units contain more interstitial liquid with late-stage minerals. The findings confirm that the anvil-shaped intrusion in cross section continues with increased thickness towards northwest at a shallow dip; although approaching the deeper part of the igneous reservoir, mineral compositions are partially more evolved. The overall mineralogical consistency downdip supports a situation of multiple magma replenishment along a flat-lying, northwest–southeast trending conduit, resulting in an evolved cumulus mineral assemblage in the upper part. [ABSTRACT FROM AUTHOR]

A series of Hf and rare earth element (REE) solutions and glass beads have been produced in order to assess the influence of isobaric and molecular interferences on LA-MC-ICP-MS analysis of Lu–Hf isotopes in zircon. We demonstrate the capability to accurately correct for isobaric interferences of 176Yb on 176Hf at levels up to 176Yb/177Hf = 0.6 in solution mode. When using laser ablation sample introduction and REE–Hf doped glass beads we are able to accurately correct for 176Yb interferences up to 176Yb/177Hf = 0.15. These thresholds exceed the 176Yb/177Hf ratios in most natural zircon and demonstrate the general robustness of the method. Unlike solution analysis, at extreme Yb interference levels (176Yb/177Hf ≈ 0.8) there appears to be a slight over-correction of Yb interferences. We demonstrate using theoretical calculations that for high-REE zircons, even modest oxide formation rates can lead to inaccurate 176Hf/177Hf ratios. This finding is confirmed by data collected on REE-doped glass beads and a natural zircon sample. Importantly, Gd oxides dominate over Dy oxides as a source of molecular interferences on Hf isotope data because Gd is more prone to oxide formation. Oxide formation rates vary depending upon sample introduction, instrument tuning and N2 addition (in laser mode). Correction for molecular interferences is possible using a dynamic analysis routine but requires measurement of the relative Gd and Hf oxide formation rates for the analysis session. Hence the daily monitoring of Gd and Hf oxide formation rates will improve the accuracy of Lu–Hf LA-MC-ICP-MS results for high-REE/Hf zircons. [ABSTRACT FROM AUTHOR]

• SJC experienced multiple magmatism of ~2.78, ~2.69 and ~2.55 Ga. • Neoarchean magma derived from episodic juvenile crust growth and crustal reworking. • Recycling of sediments was not intense or extensive in SJC during Neoarchean. • A bottom-up tectonic regime related to plume activity is favored for NCC in Neoarchean. Recent advances in high-precision in-situ analysis of zircon U-Pb-Hf-O isotopes have significantly improved our approach to studying the origin and evolution of Archean crust. This study presents high-precision in-situ zircon U-Pb-Hf-O isotopes for the Southern Jilin Complex (SJC) on the northeastern margin of the North China Craton (NCC) and explores the potential of such an integrated approach in understanding the Archean crust evolution and its tectonic implications. The SJC consists mainly of Archean granitoid gneisses hosting minor supracrustal rock xenoliths. Zircon U-Pb data from representative lithologies reveal three episodes of magmatism at ~2.78, ~2.69 and ~2.55 Ga, respectively. The former two granitoid magmatic events are recognized for the first time in NE NCC, while the latest one is widespread over the NCC. All metamorphic zircon domains document similar metamorphic ages of 2.51–2.48 Ga, consistent with the widespread metamorphism of ~2.50 Ga in the NCC. Most concordant magmatic zircons preserve "mantle-like" O isotopic signatures, indicating the magma sources were not contaminated by large amounts of high δ18O supracrustal sediments. Hf depleted mantle model ages of magmatic zircons display one predominant peak at 2.9–2.8 Ga and two subordinate peaks at 3.3–3.2 Ga and 2.7–2.6 Ga, indicating possible episodic crust-mantle differentiation in Southern Jilin. Integrated zircon U-Pb-O-Hf data from the SJC suggest that magma sources were mainly derived from multiple episodes of reworking of juvenile or ancient crust with mantle component addition, while recycling of sediments was trivial during the Neoarchean in this region. The spatial–temporal relations of magmatism, lack of supracrustal addition to magma sources, and other geological evidence from the NCC are in favor of a bottom-up geodynamic regime possibly related to plume activities, arguing against a widespread top-down mechanism involving modern-style subduction in the NCC during the Neoarchean. [ABSTRACT FROM AUTHOR]

The end of the Permian marks an important change in the depositional context of the southwestern Gondwanan continent. These changes are related to the last invasion of the Panthalassa Ocean, and the posterior oceanic retreat and emplacement of desertic conditions. This paper provides a detailed paleogeographic evolution of the southern portion of the Paraná Basin, supported by facies descriptions, stratigraphic analysis, and U-Pb-Hf detrital zircon analysis (LA-ICP-MS). The studied interval records a large regression that was composed of three forced-regression pulses related to important facies shifts ascribed to the outer ramp, inner ramp, and arid continental systems. Provenance zircon U Pb analysis in the inner ramp and continental arid climate deposits indicates that the main sediment source was the Brasiliano basement and the Gondwanides mountain ridge, situated to the west and south. The abrupt paleogeographic change related to the evolution of a system dominated by inner ramp to arid continental facies is compatible with the tectonic reorganization of the Paraná Basin close to the Permo-Triassic limit. Here we present a paleogeographic evolution model which adds new elements to better understand the great transgressive-regressive event that occurred in southwestern Gondwana during the late Permian. Unlabelled Image • End of Permian Paraná Basin stratigraphic and paleogeographic evolution. • Falling stage systems tract composed of three forced regression pulses. • U-Pb-Hf detrital zircon analysis (LA-ICP-MS). • Zircon U-Pb-Hf provenance points to sources from the south and west Brasiliano basement and Gondwanides mountain chain. • Paraná Basin tectonic reorganization near the Permo-Triassic boundary. [ABSTRACT FROM AUTHOR]

The article discusses the study conducted for the reconstruction of Late mesozoic provenances for the east Asian continental margin based on Uranium (U) Lead (Pb) detrital zircon geochronology. Topics discussed include investigation done using facies analysis, petrography, and lithochemistry, dating of detrital zircons using laser ablation inductively coupled plasma mass spectrometry, and metasedimentary rocks with subordinate volcanics.

The study presents new zircon laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb ages and in situ zircon Hf isotopic data for representative Dagayin granites in the southern Great Xing'an Range (SGXR). New data provide insight into the evolution of magmatism in the SGXR. The zircon U–Pb analysis yielded 156.8 ± 1.2 and 155.9 ± 0.7 Ma for the Dagayin granites. The granites contain 77.0–74.2 wt% SiO 2 , 13.2–11.4 wt% Al 2 O 3 , 3.9–2.9 wt% Na 2 O, 4.6–3.5 wt% K 2 O, and 0.5–0.1 wt% MgO, are metaluminous to peraluminous and high-K calc-alkaline rocks. The granites also enriched the large ion lithophile elements (LILE; e.g., Rb, Th, and U) and depleted in Ba, Sr, P, Ti, and Nb. Zircons grains within the Dagayin granite yield ε Hf (t) values of 7.5 to 9.4 and T DM2 model ages of 728–607 Ma. Geochemical characteristics and zircon Hf isotopic data indicate the magmas were generated from the partial melting of juvenile crustal material originating from the depleted mantle. The Dagayin granites are compositionally similar to abundant mineralization-related granitoids in the SGXR, suggesting the Dagayin pluton may be prospective for exploring Pb–Zn–Ag or Mo mineralization. In the Late Jurassic to Early Cretaceous, the SGXR was under an intracontinental extensional environment, relating to the superimposed subduction of the Mongol-Okhotsk plate beneath the Central Mongolia Massif, and the Paleo-Pacific oceanic beneath the Central Mongolia Massif. • The Dagayin granites aged 156.8 Ma. • Granites were derived from the partial melting of juvenile crustal material originating from the depleted mantle. • The Dagayin pluton shows great ore potentials. [ABSTRACT FROM AUTHOR]

The Sulu orogenic belt is the source of information on important magmatic events associated with the collision of the Yangtze craton and North China craton (NCC) and the destruction of the NCC during the Mesozoic in eastern China. In this study, we have, for the first time, identified a monzonitic granitic pluton. We hereby present petrological, geochemical, and zircon U-Pb-Hf-O isotopic data, shedding new light on the petrogenesis and tectonic implications for the granitic pluton in the Sulu belt. LA-ICP-MS and SHRIMP II analyses of zircon grains suggest that the monzonitic granitic pluton was crystallized in the Early Cretaceous (ca. 120 Ma). Geochemically, the granitic pluton shows sub-alkaline, high-K calc-alkaline, and metaluminous signatures, and is genetically of I-type granite, excluding the possibility of S-type granite, as evidenced by mantle-like zircon oxygen isotopic features. In addition, the pluton is enriched in light REE and large-ion lithophile elements (LILE) (e.g., La, Cs, Ba, K, and Pb), but depleted in high-field-strength elements (HFSE) (e.g., Nb, Ta, P, and Ti), suggesting an arc-related affinity. Zircon Hf isotopes (εHf(t) = −27.51~−32.35; TDM2 = 2979~3175 Ma) and mantle-like δ18O values (5.12–6.24‰) together indicate that the identified granitic pluton is derived from the partial melting (reworking) of the ancient mafic lower crustal material, with no supra-crustal material participation. Moreover, high Magnesium number (Mg# = 42–49) values and mafic micro-granular enclaves suggest that mantle-derived magma participated in the evolution of the granitic pluton in this study. Integrating the findings of this study and previous work, we propose that the Caochang granitic pluton is derived from the partial melting of the deep Yangtze basaltic lower crust during the Early Cretaceous, and that the large-scale thinning of the lithospheric mantle was the main factor that led to Early Cretaceous magmatic flare-up in the Sulu orogenic belt. [ABSTRACT FROM AUTHOR]

The Jiangjiatun Mo deposit is a recently discovered molybdenum deposit in the easternmost area of the Yan-Liao metallogenic belt, North China Craton. Quartz vein-type Mo mineralization at Jiangjiatun is associated with the granitic porphyry stock. In this study, we performed a combined zircon U–Pb and molybdenite Re-Os dating study on the Jiangjiatun Mo deposit to constrain its mineralization age and metallogenic setting. Laser ablation inductively coupled mass spectrometry (LA-ICP-MS) zircon U–Pb analyses suggest that the granitic porphyry was formed during the Late Jurassic, with a weighted mean 206Pb/238U age of 154 ± 1 Ma (2σ). Seven molybdenite samples from the Jiangjiatun deposit yield a 187Re–187Os isochron age of 157.5 ± 0.5 Ma (2σ). The discrepancy between the U–Pb and Re–Os ages may be explained (1) by the "2 sigma" measurement uncertainty, or (2) by the different closure temperature of the Re–Os isotopic system of molybdenite and the U–Pb isotopic system of zircon. Even though there is a small difference between the zircon U–Pb and molybdenite Re–Os ages, we can clearly identify a Late Jurassic Mo mineralization event at Jiangjiatun in the easternmost area of the Yan-Liao metallogenic belt. The moderate Re concentrations (13 to 73 ppm) in molybdenite from the Jiangjiatun Mo deposit are indicative of the involvement of the mantle materials into the Mo mineralization. The Jiangjiatun Mo deposit is likely the result of the subduction of the paleo-Pacific plate beneath the North China Craton during the Late Jurassic. Combined with the available published regional robust geochronological data, we proposed that the Mo mineralization in the Yan-Liao belt is in good agreement with the tectonic transition from Late Triassic post-collision extensional setting due to the closure of the paleo-Asian ocean to the Yanshanian (J–K1) continental arc setting in response to the subduction of the paleo-Pacific Plate. The study highlights that regional mineralization may provide an excellent constraint on tectonic change. [ABSTRACT FROM AUTHOR]

The article focuses on a research paper discussing the geological significance of the Zhuoma copper polymetallic deposit in Geza Arc metallogenic belt in Yunnan Province, China. It discusses the laser ablation?inductively coupled plasma?mass spectrometry (LA-ICP-MS) uranium?lead (U?Pb) dating to determine U-Pb ages of zircon. It also suggest that the band structure development shows the characteristics of magma genesis of zircon.

The article discusses the evolution process and Zircon ages of the granites in the early Palaeozic period found in the Northern Tian Shan Orogenic Belt in Kyrgyzstan. Topics mentioned include the accretionary processes which attracted concern from geologists, the analysis on zircons from granite and granodiorite samples using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), and the result that granite plutons intrude during the occurence of the Terskey Ocean subduction.