Zircon Reference Materials Research Articles

A preliminary investigation into the feasibility of laser ablation U-Pb isotope ratio measurement via all-faraday cup detection with 1011- and 1013-Ω amplifiers on the Neoma multicollector-inductively coupled plasma-mass spectrometer.

Signal detection for uranium-lead (U-Pb) dating of zircon is typically performed via ion counters. Here, we develop a preliminary understanding of the strengths and limitations of faraday-cup-based detection. A suite of zircon reference materials and the NIST-610 glass were sampled using laser ablation followed by U-Pb isotope ratio measurement on a Neoma multicollector-inductively coupled plasma-mass spectrometer. We were able to produce geologically accurate 207Pb/206Pb, 206Pb/238U, and 207Pb/235U ratios for the NIST-610 glass and the zircon standards, with ages ranging from ~2.5Ga to ~337 Ma (TanBrown A, Oracle, 91550, Mud Tank, Temora, and Plešovice). Two of the younger zircon standards examined (94-35, ~55.6Ma, and Fish Canyon, 28.6Ma) yielded accurate 206Pb/238U but not 207Pb/235U or 207Pb/206Pb ratios, whereas the youngest zircon standard (Penglai, ~4.4Ma) failed for all three ratios of interest. The accuracy and precision of the all-faraday method are directly tied to signal intensity, with reliable data capable of being produced even when both isotopes in a ratio have signals below ~0.001 V (equivalent to ~62 500 cps on an ion counter). The all-faraday cup multicollection method provides sufficient sensitivity to obtain geologically meaningful U-Pb data, with possible advantages being that laser pit depth-dependent changes in the observed interelemental fractionation behavior may be easier to correct using a static collector configuration compared to when the ion beam is swept across a single detector while also removing the need for an interdetector-type calibration. Further work is needed to refine the all-faraday cup method (e.g., application of background subtraction and common Pb corrections, outlier removal, and interelement as well as down-hole fractionation corrections), but our initial results demonstrate that the faraday detector method has sufficient sensitivity to warrant further study.

Simultaneous U–Pb and U–Th Dating Using LA-ICP-MS for Young (<0.4 Ma) Minerals: A Reappraisal of the Double Dating Approach

Simultaneous U–Pb and U–Th dating using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was performed on the ca. 0.1 Ma Toya tephra and the ca. 0.08 Ma SS14-28 U–Th zircon reference material. In U–Pb dating, both Th/U and Pa/U partitioning between magma and minerals were considered. In U–Th dating, both abundance sensitivity and molecular interferences on 230Th were reevaluated. As a result, the Toya tephra yielded an accurate weighted mean U–Pb age of 0.103 ± 0.029 Ma (2σ) using zircon and monazite. Conversely, the SS14-28 zircon yielded an inaccurate U–Pb age (0.25 ± 0.10 Ma), which was attributed to low 206Pb signal intensity. Both the Toya tephra zircon and the SS14-28 zircon yielded accurate U–Th model ages of 0.108 ± 0.014 Ma and 0.078 ± 0.007 Ma, respectively. The agreement of U–Pb and U–Th ages for Toya indicates that simultaneous U–Pb and U–Th dating is possible and viable. The inappropriate age of SS14-28 U–Pb age and appropriate U–Th model age also indicates it is preferable to apply both U–Pb and U–Th dating simultaneously for young (<0.4 Ma) zircons to check internal consistency. The proposed double dating approach may be especially useful for small grains when it otherwise would be impossible to obtain multiple ages from a single grain. By adopting simultaneous U–Pb and U–Th dating using LA-ICP-MS, zircon crystallization ages as old as 4.5 Ga to as young as 0.1 Ma (or even younger) can be obtained in a quick and cost-effective manner with a reasonable (~5% at 1σ) uncertainty.

Novel Methods for Concomitant Determination of the Stable Zr Isotope Composition, Lu‐Hf Isotope Systematics and U‐Pb Age of Individual Zircons

The stable Zr isotope ratios in zircon yield a novel geochemical tracer that, together with the Lu‐Hf and U‐Pb radiogenic isotope systems, allows for a better understanding of the magmatic evolution of silicate melts. We present a solution‐based procedure for coupled stable Zr, Lu‐Hf and U‐Pb isotope ratio determinations for individual zircons using a 91Zr‐96Zr tracer purified from Hf and a late‐spiking protocol for Zr. This method yields high‐precision Zr and Hf isotope results while maintaining low blank levels for U‐Pb isotope and Lu/Hf ratio determinations. With a two‐fold improvement on the precision relative to previous solution‐based work, we report δ94ZrIPGP‐Zr values (deviation of the 94Zr/90Zr ratio in the sample relative to the IPGP‐Zr reference material) and associated intermediate precisions (2s) for the zircon reference materials 91500, Mud Tank, Plešovice and Penglai of ‐0.041 ± 0.015‰, 0.018 ± 0.013‰, 0.089 ± 0.020‰ and ‐0.117 ± 0.021‰, respectively. Furthermore, this method yields un‐biased δ94ZrIPGP‐Zr and 176Hf/177Hf results for 25‐ng Zr and 0.56‐ng Hf aliquots of the Mud Tank zircon with intermediate precisions (2s) of 0.027‰ and 1.7 ε (parts per ten thousand), respectively. Thus, the presented method is applicable for the analysis of extremely small and rare zircon grains.

Exploring the CAM18 Crystal as a Potential Reference Material for U–Pb Analysis of Zircon

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.

Characterisation of Three Sri Lankan Zircon Megacrysts as Potential Reference Materials for Microbeam U‐Pb Geochronology and Hf‐O‐Zr Isotope Measurements

In situ U‐Pb geochronology and hafnium, oxygen and zirconium isotope measurements in zircons using laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and ion microprobe techniques can provide essential isotopic data to constrain geological evolutionary histories. Developing reliable zircon reference materials is the cornerstone for in situ zircon chronology and isotopic studies. In this study, the homogeneity of U‐Pb ages and Hf‐O‐Zr isotope ratios in three Sri Lankan zircon megacrysts (SLZA, SLZB and SLZC) were investigated using multiple analytical methods. The obtained U, Th, Pb and Hf mass fractions of the SLZA zircon were 839 ± 56 μg g‐1 (1s), 151 ± 15 μg g‐1 (1s), 198 ± 28 μg g‐1 (1s) and 8635 ± 286 μg g‐1 (1s), respectively. The mass fractions of U, Th, Pb and Hf in the SLZB zircon were 1106 ± 106 μg g‐1 (1s), 331 ± 61 μg g‐1 (1s), 376 ± 57 μg g‐1 (1s) and 9673 ± 976 μg g‐1 (1s), respectively. The U, Th, Pb and Hf mass fractions determined in the SLZC zircon were 551 ± 35 μg g‐1 (1s), 111 ± 8 μg g‐1 (1s), 129 ± 18 μg g‐1 (1s) and 7881 ± 393 μg g‐1 (1s), respectively. The chemical abrasion isotope dilution thermal ionisation mass‐spectrometry (CA‐ID‐TIMS) method yielded a Th‐corrected weighted mean 206Pb/238U age of 556.94 ± 1.29 Ma (95% conf., n = 5) for the SLZA zircon, 552.90 ± 1.29 Ma (95% conf., n = 7) for the SLZB zircon and 560.83 ± 1.29 Ma (95% conf., n = 7) for the SLZC zircon. The obtained Hf isotopic compositions of the SLZA, SLZB and SLZC zircons determined with the solution MC‐ICP‐MS method were 0.281651 ± 0.000014 (2s, n = 10), 0.281704 ± 0.000008 (2s, n = 10) and 0.281676 ± 0.000006 (2s, n = 10), respectively. The obtained O isotopes of the SLZA and SLZB zircons measured with the laser fluorination method were 12.14 ± 0.56‰ (2s, n = 4) and 11.91 ± 0.30‰ (2s, n = 4), respectively. The Zr isotopes of the SLZA, SLZB and SLZC zircons determined with double spike TIMS analysis yielded mean δ94/90ZrSRM3169 values of ‐0.03 ± 0.06‰ (2s, n = 10), ‐0.03 ± 0.04‰ (2s, n = 10) and 0.00 ± 0.07‰ (2s, n = 8), respectively. The SLZA zircon can be used as a primary reference or quality control material for microbeam U‐Pb, Hf and Zr isotope measurements because of its slight heterogeneity. The U‐Pb, Hf and Zr isotopic compositions of the SLZB and SLZC megacrysts were homogeneous. The O isotopic compositions in the SLZA and SLZB zircon were slightly dispersed, indicating that these two megacrysts can only serve as secondary reference materials for microbeam O isotope measurements.

A LA‐ICP‐MS Comparison of Reference Materials Used in Cassiterite U‐Pb Geochronology

Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) is used to compare the suitability of four cassiterite (SnO2) materials (SPG, Yankee, AY‐4 and Jian‐1), and three matrix‐mismatched reference materials (NIST SRM 612, NIST SRM 614 and 91500 zircon) for normalisation of U‐Pb and Pb‐Pb isotope ratios in cassiterite. The excess variance of ages determined by LA‐ICP‐MS is estimated to be ±0.33% for 207Pb/206Pb vs. 208Pb/206Pb isochron ages and ± 1.8% and for U‐Pb ages. Incorporation of this excess variance in cassiterite ages is necessary for realistic uncertainties. 207Pb‐206Pb ages are advantageous for dating Precambrian cassiterite such as SPG compared with U‐Pb ages as matrix effect on instrumental mass fractionation of Pb isotopes are generally considered to be minor. We note minor bias in 207Pb/206Pb vs. 208Pb/206Pb isochron ages (~ 0.6%) when using either the NIST SRM 614 or 91500 zircon reference materials and emphasise the requirement for uncertainty propagation of all sources of error and reference materials with comparable U and Pb mass fraction to the cassiterite. The 238U/206Pb isotopic ratios from normalisation to matrix‐mismatched reference materials show varied results, which emphasises the need to use matrix‐matched reference materials for calculating U‐Pb ages. When cross‐calibrated against each other, LA‐ICP‐MS U‐Pb ages of the ca. 1535 Ma SPG, ca. 245 Ma Yankee and ca. 155 Ma Jian‐1 cassiterites are all consistent with their ID‐TIMS values.

Ban‐1 Zircon: A New Natural Zircon Reference Material for LA‐MC‐ICP‐MS Zr and Hf Isotopic Determinations

New zircon reference materials for in situ zircon radiogenic Hf isotope and stable Zr isotopic determinations made by laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS) are required due to high data productivity and consequently high reference material consumption rate. This study examines a new natural zircon for Zr isotope ratios by double spike thermal ionisation mass spectrometry (TIMS), and for Hf isotopes by bulk solution nebuliser (SN)‐MC‐ICP‐MS with both Zr and Hf determined by LA‐MC‐ICP‐MS. A total of five zirconium isotope measurements from drilled zircons, determined by TIMS, yield a mean δ94/90ZrIPGP‐Zr value of ‐0.09 ± 0.06‰ (2s). Five and eight hafnium isotope measurements for powders from the drilled zircons and Ban‐1‐4 by SN‐MC‐ICP‐MS, yield mean 176Hf/177Hf ratios of 0.282985 ± 0.000011 (2s) and 0.282982 ± 0.000007 (2s), respectively. The mean δ94/90ZrIPGP‐Zr value and 176Hf/177Hf ratio determined by LA‐MC‐ICP‐MS analyses are ‐0.06 ± 0.09‰ (2s, n = 504) and 0.282985 ± 0.000035 (2s, n = 327), respectively. The isotopic homogeneities suggest that the Ban‐1 zircon is a suitable reference material for microbeam Zr and Hf isotopic measurements.

Zirconium isotopic composition of zircon reference materials by laser ablation multi-collector inductively coupled plasma mass spectrometry

Zirconium isotopes have been suggested as a new geochemical fingerprint for tracing magmatic evolution and continental crust differentiation. In this study, we optimized the Zr isotope measurement by laser-ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and reported stable Zr isotope compositions for different zircon reference materials (ZRMs). The RESOLution laser, coupled with MC-ICP-MS, yielded better results than the New Wave laser when comparing crater shape and depth indices, signal intensity, and isotopic ratio variations. The best working conditions for Zr isotope measurements were found to be with a laser spot size of 23 μm, a repetition rate of 2 Hz, and energy density of 3 J cm−2 which resulted in a crater depth of ∼8 μm. The 90Zr intensities increased by a factor of 3.2, and the raw 94Zr/90Zr ratio remained constant within a broader range of sample gas flow rate with the addition of 8 mL min−1 N2 compared to the normal mode. Negligible interferences were identified from the gas blank and also from the different integrated cycles between the bracketing standard and samples. Using the above-mentioned parameters, we obtained a long-term δ94/90ZrGJ-1 stability of 0.08‰, comparable with femtosecond laser-ablation (fsLA)-MC-ICP-MS methods. ZRMs (e.g., 91,500, Plešovice, Penglai, SA01, Tanz, and Ban-1) yielded homogeneous Zr isotope compositions, consistent with double spiked solution methods within error. Furthermore, zircon megacrysts of LKZ-1 and Cam-1, synthetical MUN-zircon with high Yb content, and MTUR1 zircon standard from carbonatite also had homogeneous Zr isotope compositions that indicate they could be used as tuning and monitoring standards. On the contrary, GHR1, Temora-2, Qinghu, and Jilin zircons were not ideal ZRMs for Zr isotope measurement. Zr isotope variations among homogeneous ZRMs (except Plešovice) further prove that Zr isotopes are a potentially powerful geochemical tracer.

Sub‐Micrometre Resolution FIB‐SEM‐based ToF‐SIMS Used to Map Geochemical Zoning in Four Zircon Reference Materials

Zircon geochemistry can vary over micrometre scales; therefore, natural reference materials need to be well characterised before being used to calculate trace element mass fractions in unmeasured samples. Moreover, reference material homogeneity needs to be ensured with the accelerating rate of geoanalytical developments to map mineral chemistry at increasingly finer scales. Here, we investigate trace element zoning in four widely used zircon reference materials: 91500, Mud Tank, Temora and Plešovice, as well as zircon crystals from the Mount Dromedary/Gulaga Igneous Complex, Australia. Sub‐micrometre resolution focused ion beam scanning electron microscope (FIB‐SEM) based time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and 5 μm resolution LA‐ICP‐MS mapping show that trace elements are zoned in all reference materials, though 91500 exhibited the least zonation. We demonstrate that FIB‐SEM‐based ToF‐SIMS can rapidly resolve variations in trace elements (e.g., U, Th, Sc, Y, Gd, Dy, Yb and Li) at sensitivities down to the μg g‐1 level with a spatial resolution of 195 nm for areas 100 × 85 μm to 959 × 828 μm. Zircon 91500 is recommended for future quantitative analyses provided that (1) the spatial distribution of elements is imaged before analysis of unknown samples and (2) it is used in conjunction with a doped glass as the primary reference material.

Development of an In SituU‐Th Disequilibrium Dating Method Utilising Multiple‐Spot Femtosecond Laser Ablation‐CRC‐ICP‐MS

In situ 238U‐230Th dating was conducted using an ICP‐mass spectrometer coupled with a laser ablation sampling system (LA‐ICP‐MS). To minimise the contribution of mass spectrometric interferences on 230Th, a kinetic energy discrimination technique using a collision/reaction cell (CRC) system was employed. The major problem associated with the CRC‐ICP‐MS system is the lower transmission efficiencies of ions than sector field mass spectrometers. To improve the signal‐to‐background ratio for analytes, a combination of a multiple‐spot laser ablation (msLA) system together with a sensitivity‐enhanced dry plasma cone was employed. Analytical accuracy was evaluated through analyses of three zircon reference materials (GJ‐1, OD‐3 and Plešovice) and the resulting 230Th/238U ratios for GJ‐1 and Plešovice zircons agreed with the secular equilibrium value. The developed technique was applied to Quaternary volcanic zircon and monazite samples from Japan. The resulting ages are 113.5 +5.4‐5.2 ka for the Toya tephra, 105.1 +6.4‐6.1 ka for the Sambe Kisuki tephra, 55.2 +7.7‐7.2 ka for the Hikageyama lava and 16.2 +4.2‐4.1 ka for the Susaki pumice (95% confidence levels). The resulting ages are consistent with previous chronological constraints including zircon fission track ages. The data obtained here demonstrate clearly that the combination of the CRC‐ICP‐MS system and the msLA protocol can become a powerful analytical tool for in situ U‐Th disequilibrium dating.

Quantifying Long‐Term Reproducibility of Zircon Reference Materials by U‐Pb LA‐ICP‐MS Dating

Inter‐session excess variance of U/Pb and Pb/Pb ratios in LA‐ICP‐MS zircon dating is the largest contributor to systematic errors, which in turn limit the accuracy of age determinations. Quantifying long‐term excess variance of reference materials allows for the estimation of excess variance in samples, but such compilations are not available in the literature. Here, we present the results of over 100 measurement sessions over 6 years for seven common zircon reference materials and calculate a characteristic excess variance for each. For 206Pb/238U ages, these values (2s) are as follows: AusZ7‐1 = 1.7% (115 sessions), AusZ7‐5 = 0% (74), OD‐3 = 0.6% (19), Temora2 = 1.2% (86), Plešovice = 1.1% (100), 91500 = 1.0% (146) and Mud Tank = 3.0% (12). For 207Pb/206Pb ages, smaller excess variances are observed: Temora2 = 0.3%, Plešovice = 0.4%, Mud Tank = 1.7% and 91500 = 0.4%. These values are well‐constrained estimates of inter‐session excess variance for the ETH Zürich LA‐ICP‐MS laboratory using a sector‐field ICP‐MS, and may provide either a first‐order estimate for other laboratories or a value to compare against their own reference material compilations.

An Improved In Situ Zircon U‐Pb Dating Method at High Spatial Resolution (≤ 10 μm Spot) by LA‐MC‐ICP‐MS and its Application

In situ small‐spot U‐Pb geochronology is essential for measuring zircon crystals containing micrometre‐scale heterogeneities, abundant inclusions, inevitable cracks and narrow growth zones, all of which are especially common in metamorphic zircons. We present a high spatial resolution (≤ 10 μm diameter) laser ablation‐multi‐collector‐inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS) U‐Pb dating method using a Nu Plasma II mass spectrometer coupled with a GeoLas HD laser ablation system, which is capable of analysing zircon crystals with a wide range of U contents through two analytical modes (mixed‐mode for 10 μm ablation and IC‐mode for 5 μm ablation). We examined Pb/U down‐hole fractionation (DHF) as a function of different laser settings under small‐spot ablation, and how it controls the accuracy and precision of U‐Pb ages of zircon reference materials. After DHF correction using Iolite software (version 3.71), five measurement sessions (with different laser fluence and/or laser pulse settings) for the two analytical modes yielded accurate and precise U‐Pb ages for four zircon reference materials (Plešovice, 91500, GJ‐1 and Temora‐2). Further determinations of U‐Pb ages of three metamorphic zircon samples (~ 14 to 2000 Ma) from the Himalaya, North China Craton and North Qaidam were conducted, the results of which confirm the effectiveness and feasibility of this small‐spot ablation method for natural zircons with multiple growth zones.

Jilin zircon – a new natural reference material for microbeam U–Pb geochronology and Hf–O isotopic analysis

This study presented a new natural zircon reference material for microbeam U–Pb geochronology and Hf–O isotopic analysis.

Tanz zircon megacrysts: a new zircon reference material for the microbeam determination of U–Pb ages and Zr–O isotopes

A new ideal zircon microanalytical reference material (Tanz) is presented for in situ U–Pb, O and Zr isotope measurements.

Further characterization of SA01 and SA02 zircon reference materials for Si and Zr isotopic compositions via femtosecond laser ablation MC-ICP-MS

We present Si and Zr isotopic data of SA01 and SA02 zircons via multi-technique analytical methods to evaluate the suitability of the two zircon reference materials for in situ Si and Zr isotopic analysis using fs-LA-MC-ICP-MS.

Long-term repeatability and interlaboratory reproducibility of high-precision ID-TIMS U-Pb geochronology.

Age determination of minerals using the U–Pb technique is widely used to quantify time in Earth's history. A number of geochronology laboratories produce the highest precision U–Pb dates employing the EARTHTIME 202Pb–205Pb–233U–235U tracer solution for isotope dilution, and the EARTHTIME ET100 and ET2000 solutions for system calibration and laboratory intercalibration. Here, we report ET100 and ET2000 solution data from the geochronology laboratory of University of Geneva obtained between 2008 and 2021 and compare the most recent data with results from the geochronology laboratories of Princeton University and ETH Zürich. This compilation demonstrates that (i) the choice of the thermal ionization mass spectrometer model has no influence on precision and accuracy of the data; (ii) the often observed excess scatter of apparent ET100 solution 206Pb/238U dates can be mitigated by more careful tracer-sample equilibration; and (iii) natural zircon reference materials are not suitable for evaluating intra-laboratory repeatability and inter-laboratory reproducibility, since they combine several phenomena of natural system complexities (especially domains of different age within the same zircon grain, and residual loss of radiogenic lead in domains of high decay damage after chemical abrasion pre-treatment). We provide our best estimates of apparent dates for the ET100 solution (206Pb/238U date, 100.173 ± 0.003 Ma), for ET2000 solution (207Pb/206Pb date, 1999.935 ± 0.063 Ma), as well as for natural reference zircon Temora-2 (206Pb/238U date, 417.353 ± 0.052 Ma). These data will allow U–Pb laboratories to evaluate their analytical performance and to independently calibrate non-EARTHTIME tracer solutions in use.

A Synthetic Haematite Reference Material for LA‐ICP‐MS U‐Pb Geochronology and Application to Iron Oxide‐Cu‐Au Systems

In both nature and synthetic experiments, the common iron oxide haematite (α‐Fe2O3) can incorporate significant amounts of U into its crystal structure and retain radiogenic Pb over geological time. Haematite is a ubiquitous component of many ore deposit types and, therefore, represents a valuable hydrothermal mineral geochronometer, allowing direct constraints to be placed on the timing of ore formation and upgrading. However, to date, no suitable natural haematite reference material has been identified. Here, a synthetic haematite U‐Pb reference material (MR‐HFO) is characterised using LA‐ICP‐MS and ID‐TIMS. Centimetre‐scale ‘chips’ of synthesised α‐Fe2O3 were randomly microsampled via laser ablation‐extraction and analysed using ID‐TIMS. Reproducible U/Pb and Pb/Pb measurements were obtained across four separate chips (n = 13). Subsequently, an evaluation of the suitability MR‐HFO in constraining U‐Pb data via LA‐ICP‐MS is presented using a selection of natural samples ranging from Cenozoic to Proterozoic in age. The MR‐HFO normalised U‐Pb ratios are more concordant and ages more accurate versus the same LA‐ICP‐MS spot analyses normalised to zircon reference material, when compared with independently acquired ID‐TIMS data from the same natural haematite grains. Results establish MR‐HFO as a suitable reference material for LA‐ICP‐MS haematite U‐Pb geochronology.

Rapid U‐Pb Geochronology by Laser Ablation Multi‐Collector ICP‐MS

Detrital zircon (DZ) U‐Pb laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) has revolutionised the way geologists approach many Earth science questions. Although recent research has focused on rapid sample throughput, acquisition rates are limited to 100–300 analyses h−1. We present a method to acquire zircon U‐Pb dates at rates of 120, 300, 600 and 1200 analyses h−1 (30, 12, 6 and 3 s per analysis) by multi‐collector LA‐ICP‐MS. We demonstrate the efficacy of this method by analysing twelve zircon reference materials with dates from ~ 3465 to ~ 28 Ma. Mean offset from high‐precision dates increases with faster rates from 0.9% to 1.1%; mean random 1s uncertainty increases from 0.6% to 1.3%. We tested this new method on a sandstone sample previously characterised by large‐n DZ geochronology. Quantitative comparison shows increased correspondence among age distributions comprising > 300 dates. This new method holds promise for DZ geochronology because (a) it requires no major changes to hardware, but rather modifications to software; (b) it yields robust age distributions well‐suited for quantitative analysis and maximum depositional age calculations; (c) there is only a minor sacrifice of accuracy and measurement uncertainty; and (d) there is less burden to researchers in terms of time investment and analytical cost.

KV01 zircon—A potential New Archean reference material for microbeam U-Pb age and Hf-O isotope determinations

To meet the rapid development of zircon U-Pb geochronology and Hf-O isotope geochemistry, it is imperative to develop well-characterized zircon reference materials for microbeam analysis. Here, zircon KV01 separated from the Kaap Valley pluton, South Africa is introduced as a potential Archean reference material for microbeam U-Pb age and Hf-O isotope determination. SIMS and LA-ICP-MS U-Pb isotopic measurements gave grand mean 207Pb/206Pb ages of 3233±16 Ma (2s, n=90) and 3230±26 Ma (2s, n=52), which are consistent with reported CA-ID-TIMS results. Slight heterogeneity of oxygen isotopes is revealed by SIMS analyses that yielded a relatively large δ18O range of 4.61–6.51‰. Among them, the zircon grains with clear oscillatory zones give a grand mean δ18O value of 6.17±0.33‰ (2s), which is suggested to record the primary O isotopic compositions. The homogeneity in the Hf isotopic compositions of KV01 zircon was checked by the laser ablation and solution MC-ICP-MS methods. They yielded consistent results with a recommended 176Hf/177Hf ratio of 0.280810±0.000013 (2s). The results reported here demonstrate that KV01 zircon could be a reliable reference material for microbeam 207Pb/206Pb age and Hf isotope determinations of ancient zircons, and be suitable as a quality monitor for SIMS oxygen isotopic analysis.

Concurrent Determination of U‐Pb Age and REE Mass Fractions of Zircon by High Mass Resolution SIMS

A combined geochronological and geochemical investigation for the same domain of zircon provides valuable information on timing and genesis, particularly in the case of multi‐growth metamorphic zircon. A high spatial resolution concurrent analytical method for zircon U‐Pb age and rare earth element content was successfully achieved in this study, using a multi‐collector secondary ion mass spectrometer (SIMS) at a ~ 8 μm diameter scale. Special instrument parameters were employed, including a high mass resolution of approximately 15000 applied to replace the previous energy filter method, and a dynamic multi‐collector mode used to reduce the measurement time to 18 min per analysis. Six zircon reference materials yielded precise and accurate 206Pb/238U ages, which are comparable to those obtained by the ordinary mono‐collector method, but with 2–3 times higher spatial resolution. All zircon grains measured in this study showed enriched heavy‐REE (HREE) contents consistent with previously reported values determined by LA and solution ICP‐MS methods. The light‐REE (LREE) mass fractions measured using both SIMS and LA‐ICP‐MS methods in this study, although with quite different volume, show consistent results within uncertainties.