Laser Ablation Multi-collector Inductively Coupled Plasma Mass Spectrometry Research Articles

Uranium Single Particle Analysis for Simultaneous Fluorine and Uranium Isotopic Determinations via Laser-Induced Breakdown Spectroscopy/Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry.

Uranyl fluoride (UO2F2) particles (<20 μm) were subjected to first-of-its-kind analysis via simultaneous laser-induced breakdown spectroscopy (LIBS) and laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS). Briefly, a nanosecond pulsed high-energy laser was focused onto the sample (particle) surface. In a single laser pulse, the UO2F2 particle was excited/ionized within the microplasma volume, and the emission of light was collected via fiber optics such that emission spectroscopy could be employed for the detection of uranium (U) and fluorine (F). The ablated particle was simultaneously transported into the MC-ICP-MS for high precision isotopic (i.e., 234U, 235U, and 238U) analysis. This method, LIBS/LA-MC-ICP-MS was optimized and employed to rapidly measure 80+ UO2F2 particles, which were subjected to different calcination processes, which results in varying degrees of F loss from the individual particles. In measuring the particles, the average F/U ratios for the populations treated at 100 and 500 °C were 2.78 ± 1.28 and 1.01 ± 0.50, respectively, confirming loss of F through the calcination process. The average 235U/238U on the particle populations for the 100 and 500 °C were 0.007262 (22) and 0.007231 (23), which was determined to be <0.2% from the expected value. The 234U/238U ratios on the same particles were 0.000053 (11) and 0.000050 (10) for the 100 and 500 °C, respectively, <10% from the expected value. Notably, each population was analyzed in under 5 min, demonstrating the truly rapid analysis technique presented here.

Laser In Situ U–Pb Isotope Dating of Carbonate Rocks in Weijia Guyot in the Western Pacific Ocean and Its Geological Significance

Shallow-water carbonate rocks constitute a crucial component of large guyots, arising in distinct environments and harboring valuable insights into the evolutionary stages of seamount islands as well as the tectonic conditions of the underlying oceanic plate. Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) was used to conduct in situ U–Pb isotope dating of carbonate minerals with low uranium content collected from Weijia Guyot. This dating approach yielded crucial evidence for the vertical development of the seamount. Our study indicates that shallow-water carbonate rocks in Weijia Guyot had a temporal range between 91 My and 137 My. The carbonate rocks underwent two growth phases, Hauterivian to Barremian and Cenomanian to Turonian, with a hiatus of approximately 20 My. Since the Hauterivian age, the shield volcano of Weijia Guyot is essentially complete, with its seamount top exposed at or near sea level and receiving its first stage of shallow-water carbonate sedimentation. Based on the dating of both shallow-water carbonate rocks and hawaiite within the Weijia Guyot, it is inferred that approximately 10 My elapsed from shield-building volcanism to late alkalic volcanism. During the Turonian age, the main reason for the second phase of shallow-water carbonate rocks in the seamounts was the regional tectonic uplift triggered by the drift of the Weijia Guyot along with the Pacific Plate toward the Society hotspot.

Development of a Matrix‐Matched Barite Reference Material (NWU‐Brt) for Calibration of In Situ S Isotope Measurements by Laser Ablation Multi‐Collector Inductively Coupled Plasma‐Mass Spectrometry

A new matrix‐matched reference material (NWU‐Brt) with sulfur isotope ratios resembling those of natural barites has been developed for in situ S isotope measurements by laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS). A 100 g quantity of natural barite crystal was milled to ultra‐fine particles and sintered to a solid block using a fast hot‐pressing sintering technique (FHPS). We report δ34S ratios determined by isotope ratio mass spectrometry (IRMS), solution nebuliser multi‐collector inductively coupled plasma‐mass spectrometry (SN‐MC‐ICP‐MS) and LA‐MC‐ICP‐MS, involving up to six participating laboratories. The homogeneity of δ34S ratios of the synthesised barite was tested by LA‐MC‐ICP‐MS with an analytical spot size of 53 μm. The LA‐MC‐ICP‐MS results show that NWU‐Brt demonstrates a satisfactory homogeneous composition and is an appropriate material for calibrating δ34S ratios in barite. IRMS and SN‐MC‐ICP‐MS produced mean δ34S values of +14.17 ± 0.42‰ (2s) and +14.27 ± 0.23‰ (2s), respectively. The results of LA‐MC‐ICP‐MS analyses are consistent with the IRMS and SN‐MC‐ICP‐MS ratios within uncertainty. Overall, our results confirm the suitability of NWU‐Brt for the calibration of δ34S ratios in barite using LA‐MC‐ICP‐MS.

In Situ Trace Element and S-Pb Isotope Study of Pyrite from the Denggezhuang Gold Deposit in the Jiaodong Peninsula—Insights into the Occurrence of Gold and the Source of Ore-Forming Materials

The Jiaodong gold province is one of the most important gold fields globally and the largest in China. The Denggezhuang gold deposit is situated in the eastern portion of the Muping metallogenic belt, within the Jiaodong gold province. Despite many recent investigations, detailed mineralogical studies, particularly on auriferous minerals such as pyrite, are lacking. Therefore, further constraints on the occurrence mode and source of gold are necessary for this deposit. This study employed in situ laser ablation (multi-collector) inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) trace element and sulfur-lead isotopic analyses on pyrite at different stages. The aim was to reveal the occurrence status of various trace elements within Denggezhuang pyrite and to trace the complete evolution process of multi-stage fluids at Denggezhuang, elucidating the sources of gold mineralization. Four generations of pyrite in chronological order, Py-1, Py-2a, Py-2b, and Py-3, were identified via petrographic and backscattered electron (BSE) image analyses. Using in situ LA-MC-ICP-MS, we found that Co and Ni are most abundant in Py-1, while Py-2b is rich in As, Au, Ag, Pb, and Zn, reflecting the evolution of the mineralizing fluids in different mineralization stages. Py-2b contains a significant amount of invisible lattice gold, which migrates and precipitates within fluids rich in As. The in situ LA-MC-ICP-MS S-Pb isotopic analysis of pyrite indicates a relatively consistent source of ore-forming materials across different stages. Additionally, the S-Pb isotope characteristics resemble those of widely distributed coeval mafic dikes. Therefore, we propose that a water-rich, fertile, and deep-seated mafic magmatic system might have provided fluids, materials, and heat for mineralization.

A potential stibnite reference material for sulfur isotope determination by LA-MC-ICP-MS

A natural stibnite (BJ-Snt) is recommended as a potential reference material for S isotope analysis employing laser ablation multicollector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS).

Development of in situ Li isotope analysis using laser ablation quadrupole inductively coupled plasma mass spectrometry

RationaleLithium isotope geochemistry is an important tool in the studies of Earth and planetary materials. In situ Li isotope analyses are typically performed using secondary ion mass spectrometry (SIMS) or laser ablation multicollector inductively coupled plasma mass spectrometry (LA‐MC‐ICPMS), but these instruments are not widely accessible. Here, the capability of laser ablation quadrupole ICPMS for conducting Li isotopic analyses is evaluated.MethodsAn array of MPI‐DING and USGS silicate glass reference materials was analyzed repeatedly over the course of 6 months. These materials range from komatiite to rhyolite in terms of silica content (45.5–75.6 wt%) with 9–45 ppm Li. Their Li isotope compositions have been previously characterized so that matrix effects could be tested with these reference materials. Analyses were conducted using an NWR193 laser ablation system coupled to an Agilent 7900 ICPMS system.ResultsAnalytical precision is primarily limited by Li concentration in the samples. For samples with ~9 ppm Li, the internal precision is 6‰ (2 SD, 150 μm spot diameter), whereas that for a sample with ~45 ppm Li is 4‰ (2 SD, 120 μm spot diameter). The technique is somewhat sensitive to sample matrix: samples with SiO2 content that deviates from the bracketing standard display fractionated δ7Li, necessitating correction using a session‐specific matrix correction curve.ConclusionLithium isotope analysis by ns‐LA‐QICPMS is worthwhile for samples with high Li concentrations and when a matrix‐matched standard can be obtained. Although the precision of this method is not as high as those achievable with SIMS and LA‐MC‐ICPMS, it remains adequate for resolving large isotope fractionations found in natural and laboratory settings.

Uranium age dating measurements by laser ablation multi-collector ICP-MS in uranium materials

AbstractThe aim of the present work was to develop a direct method for age dating (production date measurement) of uranium samples by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) by the measurement of the 230Th/234U ratio. The major instrumental conditions and sample characteristics affecting the accuracy and precision were investigated in this systematic study. By comparing the obtained LA-MC-ICP-MS results with those obtained after chemical separation measurements, it shows that the LA-MC-ICP-MS method is capable to produce accurate results for pure highly enriched uranium. Natural and low-enriched uranium, however, needs a higher mass resolution to remove the identified interferences, which can lead to erroneous results.

In situ Strontium isotope stratigraphy of fish teeth in deep-sea sediments from the western Clarion-Clipperton Fracture Zone, eastern Pacific Ocean

The geochronology of deep-sea sediments beneath the carbonate compensation depth (CCD) presents a challenge due to the calcareous microfossils dissolution, low sedimentation rates, sedimentary hiatus, and redeposition. Fish teeth, commonly found in deep-sea sediments, have been utilized for Sr isotope stratigraphic dating. However, continuous Sr isotope exchange with pore water limits the utility of fish teeth in this context.In this study, we employed laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS), scanning electron microscopy (SEM), and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to obtain accurate stratigraphic chronology results from rare earth element and yttrium (REY)-rich sediments in the Clarion-Clipperton Fracture Zone (CCFZ) of the Pacific Ocean.Our analysis indicated that a fish tooth characterized by a dense structure and low La content exhibited a relatively initial 87Sr/86Sr ratio. Additionally, La contents at the same depth displayed a strong positive correlation with 87Sr/86Sr ratios, suggesting that Sr isotopes exchange with pore water during early diagenesis when La and other elements entered the fish teeth. However, certain fish teeth were able to resist early diagenesis alteration due to their dense structure.Based on in situ Sr-isotope stratigraphy results, we estimated the REY-rich layer age in core GC1901 to be 24–32 Ma, consistent with the REY-rich layers of DSDP/ODP in the CCFZ. Our study thus provides a new method for in situ Sr isotope analysis of fish teeth, which improves the accuracy of Sr isotope stratigraphy of pelagic sediments and could be widely used in deep-sea exploration.

Sources of Inaccuracy in Boron Isotope Measurement Using LA‐MC‐ICP‐MS

Laser ablation multi‐collector‐inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS) has become a valuable tool for the in situ measurement of the boron isotope composition of geological samples at high (tens to hundreds of μm) spatial resolution. That said, this application suffers from significant analytical challenges. We focus in this study on the underlying processes of two of the main causes for inaccuracies using this technique. We provide empirical evidence that not only Ca ions (Sadekov et al. 2019, Standish et al. 2019, Evans et al. 2021) but also Ar ions, that are reflected within the flight tube of the mass spectrometer, are the source for previously reported issues with spectral baselines. We also address the impact of plasma conditions on the instrumental mass fractionation as a source for matrix‐ and mass‐load‐related analytical biases. Comparing experimental data with the results of a dedicated release and diffusion model (RDM) we estimate that a close to complete (~ 97%) release of boron from the sample aerosol is needed to allow for consistently accurate LA boron isotope measurement results without the need for corrections.

Development of three chalcopyrites and one copper metal as potential reference materials for copper isotopic analysis by LA-MC-ICP-MS.

Laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has become a powerful technique for in situ Cu isotopic analysis in natural geological samples. Cu isotopic compositions in natural chalcopyrites have been used to reveal aspects of the mineralization processes directly. However, internationally or commercially available matrix-matched chalcopyrite reference materials for mass fractionation correction or quality control purposes are still lacking for in situ Cu isotopic analysis using LA-MC-ICP-MS. Three natural chalcopyrites 14ZJ12-1, JGZ-29 and JGZ-78, and one copper metal GBW02141 with different Cu isotopic compositions were investigated as potential microanalytical reference materials by LA-MC-ICP-MS. Ga element was used as an internal standard to correct the mass fractionation of Cu isotopes during LA-MC-ICP-MS analysis. A large number of Cu isotope ratio measurements using femtosecond LA-MC-ICP-MS were conducted and produced good intermediate precision of δ65 CuNIST976 (0.07-0.08‰, 2 standard deviations), demonstrating the homogeneous Cu isotopic distribution in the recommended samples. The mean δ65 CuNIST976 values of -0.21 ± 0.04‰, 0.46 ± 0.04‰, -0.06 ± 0.04‰ and 0.11 ± 0.05‰ (2 standard deviations) in 14ZJ12-1, JGZ-29, JGZ-78 and GBW02141, respectively, were obtained using solution-MC-ICP-MS in the four recommended samples. Here, we describe three natural chalcopyrites 14ZJ12-1, JGZ-29, JGZ-78, and one copper metal GBW02141 as the potential Cu isotopic reference materials for LA-MC-ICP-MS analysis. Our analyses demonstrate that these recommended materials have a high degree of elemental and isotopic homogeneity, indicating that they are suitable for microanalysis techniques for data quality assurance or interlaboratory calibration.

Matrix-independent boron isotope analysis of silicate and carbonate reference materials by ultraviolet femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry with application to the cold-water coral Desmophyllum dianthus.

Boron isotopes are a powerful tool for pH reconstruction in marine carbonates and as a tracer for fluid-mineral interaction in geochemistry. Microanalytical approaches based on laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) often suffer from effects induced by the sample matrix. In this study, we investigate matrix-independent analyses of B isotopic ratios and apply this technique to cold-water corals. We employ a customized 193 nm femtosecond laser ablation system (Solstice, Spectra-Physics) coupled to a MC-ICP-MS system (Nu Plasma II, Nu Instruments) equipped with electron multipliers for in situ measurements of B isotopic ratios (11 B/10 B) at the micrometric scale. We analyzed various reference materials of silicate and carbonate matrices using non-matrix matched calibration without employing any correction. This approach was then applied to investigate defined increments in coral samples from a Chilean fjord. We obtained accurate B isotopic ratios with a reproducibility of ±0.9‰ (2SD) for various reference materials including silicate glasses (GOR132-G, StHs6/80-G, ATHO-G and NIST SRM 612), clay (IAEA-B-8) and carbonate (JCp-1) using the silicate glass NIST SRM 610 as calibration standard, which shows that neither laser-induced nor ICP-related matrix effects are detectable. The application to cold-water corals (Desmophyllum dianthus) reveals minor intra-skeleton variations in δ11 B with average values between 23.01‰ and 25.86‰. Our instrumental set-up provides accurate and precise B isotopic ratios independently of the sample matrix at the micrometric scale. This approach opens a wide field of application in geochemistry, including pH reconstruction in biogenic carbonates and deciphering processes related to fluid-mineral interaction.

Formation of the Huayangchuan (Central China) carbonatite-associated REE-Nb-U polymetallic deposit constrained from monazite mineral chemistry and isotope systematics: HREE enrichment in late-stage monazite

The process of enrichment of middle and heavy rare earth elements (MREE and HREE = Sm-Lu plus Y) in magmatic-hydrothermal systems, especially the carbonatite system, remains unclear. Here, we performed in-situ monazite element and isotopic analysis to investigate the genesis of the Huayangchuan REE-Nb-U polymetallic deposit in central China and the enrichment process of MREE and HREE during the evolution of the magmatic hydrothermal system. The Huayangchuan deposit is spatially associated with HREE-rich calcite carbonatites, which exist as two mineralization stages: the ores of the first stage are hosted by carbonatite itself; in the second stage, the ores are present as veins, dominantly by wall rocks around the carbonatite. The results of secondary ion mass spectrometry (SIMS) monazite U-Pb dating on the thin sections yielded Tera-Wasserburg lower intercept ages of 207 ± 4 Ma and 206 ± 5 Ma for carbonatite-hosted monazite and vein-type monazite, respectively. However, some monazite analysis points provide a wide Yanshanian age range (112–182 Ma). The lower intercept age of 206–207 Ma is explained as the mineralization age of the deposit, whereas the wide younger age with higher 238U/206Pb and lower 208Pb/232Th ratios may be ascribed to the loss of radioactive Pb, as the varying degrees of reworking resulted from the later Yanshanian tectono-thermal event. The monazite laser-ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) Sr-Nd isotopes from both carbonatite-hosted and wall-rock-hosted vein-type ores indicate that the Huayangchuan deposit is closely related to enriched mantle-derived (EM1) calcite carbonatite but locally affected by late fluid activation. Combined with the integrated age spectra, such reworking processes associated with new weak mineralization widely exist in other carbonatite-related deposits in the Lesser Qinling, but are not important for carbonatite-related mineralization in this area. Controlled by element behaviors, MREE and HREE are more likely to dissolve in hydrothermal fluids, enabling their long-distance migration and deposition, than light REE (LREE) in some carbonatite systems, resulting in much higher MREE and HREE contents of the late monazite in the vein-type ores than those of the early carbonatite-hosted monazite. Therefore, it could be expected that there might be MREE and HREE enrichment and exploration potential in the periphery of some large carbonatite-related LREE-dominated deposits.

Comparison between strip sampling and laser ablation methods to infer seasonal movements from intra-tooth strontium isotopes profiles in migratory caribou

Strontium isotopes analysis is a powerful tool in the study of past animal movements, notably the sequential analysis of tooth enamel to reconstruct individual movements in a time-series. Compared to traditional solution analysis, high resolution sampling using laser-ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has the potential to reflect fine scale mobility. However, the averaging of the 87Sr/86Sr intake during the enamel mineralization process may limit fine scale inferences. We compared solution and LA-MC-ICP-MS 87Sr/86Sr intra-tooth profiles from the second and third molars of 5 caribou from the Western Arctic herd, Alaska. Profiles from both methods showed similar trends, reflecting the seasonal migratory movements, but LA-MC-ICP-MS profiles showed a less damped 87Sr/86Sr signal than solution profiles. Geographic assignments of the profile endmembers to the known summer and winter ranges were consistent between methods and with the expected timing of enamel formation but showed discrepancy at a finer scale. Variations on LA-MC-ICP-MS profiles, consistent with expected seasonal movements, suggested more than an admixture of the endmember values. However, more work in understanding enamel formation in Rangifer, and other ungulates, and how 87Sr/86Sr daily intake translates into enamel are needed to assess the real resolution that can be achieved with LA-MC-ICP-MS.

Tectonomagmatic evolution of southwestern Laurentia: Insights from zircon U-Pb geochronology and hafnium isotopic composition of the Red Bluff Granite Suite, west Texas, USA

AbstractWe provide laser ablation–multicollector–inductively coupled plasma–mass spectrometry (LA-MC-ICP-MS) and high-precision chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb ages and Hf isotopic compositions of zircons from the Red Bluff Granite Suite and mafic dikes in the Franklin Mountains of El Paso, Texas, USA. Granitoids exposed in the Franklin Mountains were previously divided into five magmatic stages based on cross-cutting relationships. Major and trace element compositions showed that these granitoids are ferroan, alkaline, and A2 type. Homogeneity in the whole-rock geochemistry suggests that the granite stages are genetically related and share similar petrogenetic histories. Weighted mean zircon 206Pb/238U dates from the older magmatic stage 1 alkali-feldspar quartz syenite and stage 2 alkali-feldspar granite are 1112.36 ± 0.35 and 1112.46 ± 0.37 Ma, respectively. The weighted mean εHf(t) values varying from +5.3 to +7.2 are similar to those of other regional ca. 1.1 Ga magmatic rocks throughout southwestern Laurentia. Geochemical characteristics, petrological modeling, and enriched Hf isotopic composition suggest fractional crystallization of a basaltic magma that was produced by melting of an enriched mantle reservoir. However, zircon inheritance ages of ca. 1.3 Ga and 1.26–1.15 Ga are consistent with a minor contribution from felsic crustal basement. Our data and regional geology are consistent with a post-collisional slab break-off that facilitated asthenospheric upwelling and partial melting of the enriched mantle, possibly subcontinental lithospheric mantle, extending from Llano Uplift, Texas, in the southeast to California to the northwest. Magma thus generated upon differentiation produced ferroan and A-type granitoids.

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.

U-PB AND LU-HF IN ZIRCON DECIPHERING MAGMATIC PULSES OF THE JUÍNA KIMBERLITE: IMPLICATIONS FOR THE LITHOSPHERIC MANTLE ISOTOPIC COMPOSITION OF THE AMAZONIAN CRATON

This work aims to analyze U-Pb and Lu-Hf ages in zircons formed together with diamonds from the kimberlite province of Juína, in Mato Grosso state, Brazil. Fourteen megacryst (2-3 cm) of zircon were imaged by cathodoluminescence to evaluate the internal structure of the zircon grains and zoning features related to structures of reactions and resorption indicative of magma mixture during evolution. According to the taken images, most of the investigated crystals have a non-metamict structure, with rare fractures, inclusions, and overgrowths, which generates a small degree of heterogeneity. Analyses by Laser Ablation- Multi-Collector- Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) were performed to determine grain ages. Concordia diagrams indicate ages ranging from 99.8 ± 1.6 Ma to 89.5 ± 5.6 Ma with two clusters indicating different magmatic pulses. The analyzed zircons displayed total concentrations of U and Th ranging from 108 to 673 mg kg-1 and 26 to 194 mg kg-1, respectively, and U/Th values varying between 4 and 0.3. The concentrations of U and Pb suggest the occurrence of magmas with two distinct signature components. One hundred and twenty Lu-Hf isotopic results obtained by LA-MC-ICP-MS indicate homogeneity in the isotopic composition, with εHf values ranging from +2.2 to -1.9, and depleted mantle model ages (TDM) between 1.45 Ga and 2.55 Ga. The results suggest that the kimberlite magma derives from a mantle source enriched with an Hf isotopic signature equivalent to the chondritic unfractionated reservoir (CHUR).

Sr ISOTOPES BY LA-MC-ICP-MS PROCEDURES COUPLED WITH THE MACS3 REFERENCE MATERIAL IN A CORAL SAMPLE: A RECORD OF ENVIRONMENTAL CHANGES

The main aim of this work is to demonstrate that the Laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) is a powerful tool for the analysis of strontium (Sr) isotopes in corals. This work discusses certification strategies for Sr isotopes determination, using reference material (RM) analyses and the results treatment based on detailed data acquired in biological materials, a coral sample. To obtain reliable results, it is essential to properly adjust the mass spectrometer and laser ablation system. Adjusting the equipment to its maximum intensity does not always result in correct 87Sr/86Sr ratios. Therefore, the optimization of the mass spectrometer was performed using the reference material NIST SRM-987 (solution) and adjusting the correct Sr isotope ratio to the reference material (USGS MACS3 and NIST-612, solids) before each analytical session. The protocol applied the solid reference material USGS MACS3 with an isotopic ratio 87Sr/86Sr of 0.72000. The values obtained for this RM varied between 0.7012 and 0.7014, with a correction factor calculated between 0.990 and 0.988. In order to account for potential drifts in the mass spectrometer during an analytical session, the application of bracketing correction and the use of the most convenient reference material are suggested. The analytical uncertainty of Sr data obtained by LA-MC-ICP-MS is comparable to studies carried out on other carbonate materials. The results of ablation techniques are reproducible within the analytical error, which implies that this technique produces robust results when applied to coral carbonates. In addition, several comparative measurements of different reference materials (e.g. USGS MACS3 and NIST 612) and the comparison of the 87Sr/86Sr ratios highlight the robustness of the method. The results along the coral growth axes showed a decrease in the 87Sr/86Sr ratio from the inner to the outer layer of the coral (from 0.70920 to 0.70627), which indicate variations in the availability of particulate matter during the coral growth, probably related to local marine environmental changes.

A Practical Procedure for Analysis of Lead Isotopes in Bivalve Shells Using Laser Ablation Multicollector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS).

Lead, like other trace elements, is incorporated in the growing bands of bivalve shells. The chemicals stored into the shells can provide valuable information about seawater conditions during the period of shell formation. In this study, we present a practical approach to determine Pb isotopic signatures in bivalve shells as a tool for evaluating lead pollution in coastal waters. To demonstrate the applicability of the method, Pb isotopic fingerprinting in bivalve shell layers were investigated using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Lead isotope ratios (208Pb/206Pb and 206Pb/207Pb) were measured along distinct sections of the maximum growth axis of the shells. Calibration and quantification of Pb isotopes were performed using NIST 612 as reference material. Our results demonstrated that Pb isotope ratios in the shells ranged from 1.143 to 1.201 for 206Pb/207Pb and from 2.061 to 2.161 for 208Pb/206Pb. The isotopic signatures recorded in the sample shells correspond to similar ranges of Pb signatures reported for marine sediments from the same study area. In general, this work shows that LA-MC-ICP-MS is a suitable technique for determining spatially resolved lead isotopic signatures in bivalve shells and that it can be used to estimate the origin of Pb pollution in aquatic environments.

Improved in situ analysis of lead isotopes in low-Pb melt inclusions using laser ablation-multi-collector-inductively coupled plasma-mass spectrometry.

In situ Pb isotope analyses of tiny melt inclusions using laser ablation-multi-collector-inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) are crucial for exploring the origins of mafic lavas. However, quantitative use of this technique with low-Pb (<10ppm) melt inclusions is difficult due to their low 204 Pb content and 204 Hg interference. Pb isotopic ratios of various reference glasses and olivine-hosted melt inclusions were determined using LA-MC-ICP-MS. Multiple ion counters were used to simultaneously determine signal intensities of all Pb isotopes and 202 Hg. An Hg signal-removal smoothing device reduced its signal in the gas blank by >80%. Instrumental mass bias was corrected using the standard-sample bracketing method. With 24-90 μm diameter laser spots, 2-4Hz repetition rates, and 2.5-4J cm-2 energy fluence, the analytical precisions of 20x Pb/204 Pb ratios (x = 6, 7, 8) for standards BHVO-2G, ML3B-G, NIST 614, NKT-1G, T1-G, GOR132-G, and StHs6/80-G were <1.0% (2RSD) when 208 Pb signals >100 000 cps. The Wangjiadashan melt inclusions have 206 Pb/204 Pb = 17.14-18.44, 207 Pb/204 Pb = 15.28-15.66, and 208 Pb/204 Pb = 37.12-38.68. The described method improves the precision and accuracy of in situ Pb isotope analysis in low-Pb melt inclusions using LA-MC-ICP-MS. The Pb isotopic compositions of the Wangjiadashan melt inclusions indicate the coexistence of LoMu and EMII+young HIMU components in the mantle source of weakly alkaline basalts.