The Flinton Group is a metasedimentary succession of the Grenville Province in SE Ontario, potentially allowing insight into the tectono‐thermal evolution of continental crust during the ...Mesoproterozoic. At its Green Bay locality, Flinton Group metapelites of the staurolite zone contain abundant, post‐kinematic garnet porphyroblasts. Whereas the larger garnet crystals are typically impinged, smaller crystals are isolated from each other, occasionally exhibiting elongated shapes with apparently trigonal morphology. Central sections of the garnet population of a representative sample reveal that garnet is composed of different compositional and microstructural domains. In the largest crystals of the population, garnet contains rectangular to rhombic domains, marked by sharp increases in the concentrations of Nb, V, Ti, and Cr. These domains are associated with irregularly shaped patches, characterized by spatially heterogenous enrichments of Ca and LREE, and depletions in the contents of P, Y, MREE, and HREE, accompanied by increased densities of comparatively coarse‐grained quartz inclusions hosting apatite. Microstructural relationships indicate that these domains correspond to portions of garnet that pseudomorphed biotite, with the enrichments of Nb, V, Ti, and Cr outlining the original biotite shapes. The compositional patterns formed by Ca, P, Y, and REE indicate that apatite participated in the grain‐fluid interactions that operated during the metasomatic replacement of biotite by garnet. The statistical analyses of the garnet number and size distributions confirm that garnet initially nucleated on biotite, controlled by the kinetics of attachment and detachment processes at the garnet/biotite interface, resulting in the typical impingement habit. In situ Lu–Hf garnet geochronology applied to garnet that did not pseudomorph biotite, and hence is enriched in HREE, points to a first metamorphic event at c. 1080
± 31 Ma. Subsequent pseudomorphism of staurolite by white mica in a Al2O3‐ and FeO‐mobile system resulted in the concomitant crystallization of a new garnet generation, forming overgrowths on the first garnet generation and nuclei in the fine‐grained matrix. Garnet that nucleated during this event grew to isolated and elongated crystals with apparently trigonal morphology, aligned in a direction c. perpendicular to the rock matrix foliation. The open‐system behaviour during this event limits the use of whole‐rock‐based geochronological and thermobarometrical applications. However, previously published in situ U–Pb ages of monazite included in the rims of the garnet crystals and in the rock matrix indicate that this event took place at c. 976
± 4 Ma, likely associated with a period of increased hydrothermal activity late in the metamorphic history of the Grenvillian Orogeny. Diffusion geospeedometry calculations indicate that garnet growth during this hydrothermal event lasted for less than 6 Myr.
LA‐ICP‐MS is one of the most promising techniques for in situ analysis of geological and environmental samples. However, there are some limitations with respect to measurement accuracy, in particular ...for volatile and siderophile/chalcophile elements, when using non‐matrix‐matched calibration. We therefore investigated matrix‐related effects with a new 200 nm femtosecond (fs) laser ablation system (NWRFemto200) using reference materials with different matrices and spot sizes from 10 to 55 μm. We also performed similar experiments with two nanosecond (ns) lasers, a 193 nm excimer (ESI NWR 193) and a 213 nm Nd:YAG (NWR UP‐213) laser. The ion intensity of the 200 nm fs laser ablation was much lower than that of the 213 nm Nd:YAG laser, because the ablation rate was a factor of about 30 lower. Our experiments did not show significant matrix dependency with the 200 nm fs laser. Therefore, a non‐matrix‐matched calibration for the multi‐element analysis of quite different matrices could be performed. This is demonstrated with analytical results from twenty‐two international synthetic silicate glass, geological glass, mineral, phosphate and carbonate reference materials. Calibration was performed with the certified NIST SRM 610 glass, exclusively. Within overall analytical uncertainties, the 200 nm fs LA‐ICP‐MS data agreed with available reference values.
La technique LA‐ICP‐MS est une des techniques les plus prometteuses pour l'analyse in situ d'échantillons géologiques et environnementaux. Cependant, il existe certaines limitations en ce qui concerne l'exactitude des mesures, en particulier pour les éléments volatils, sidérophiles et chalcophiles, lors de l'utilisation de calibrations sans correspondance de matrice. Nous avons donc étudié les effets liés à la matrice avec un nouveau système d'ablation laser femtoseconde (fs) 200 nm (NWRFemto200) en utilisant des matériaux de référence avec différentes matrices et des tailles de spot variant de 10 à 55 μm. Nous avons également effectué des expériences similaires avec deux lasers nanosecondes (ns), un laser excimer 193 nm (ESI NWR 193) et un laser 213 nm Nd:YAG (NWR UP‐213). L'intensité ionique de l'ablation laser fs 200 nm est beaucoup plus faible que celle du laser 213 nm Nd: YAG, parce que le taux d'ablation est inférieur d'un facteur d'environ 30. Nos expériences ne montrent pas une importante dépendance de la matrice avec le laser fs 200 nm. Par conséquent, une calibration sans correspondance de matrice pour l'analyse multi‐élémentaire de matrices très différentes peut être envisagée. Ceci est démontré par les résultats d'analyse de vingt‐deux matériaux de référence internationaux de type verres de silicate synthétique, verres géologiques, minéraux, phosphates et carbonates. L'étalonnage a été réalisé exclusivement avec le verre certifié NIST SRM 610. En tenant compte de l'ensemble des incertitudes analytiques, les données LA‐ICP‐MS fs 200 nm sont en accord avec les valeurs de référence disponibles.
U‐Pb dating of calcite is an emerging but rapidly growing field of application in geochronology with great potential to inform problems in landscape, basin, and mountain belt evolution, through age ...determination of diagenetic cements, vein mineralization, and geological formations difficult to date otherwise. In this brief, we present isotope dilution U‐Pb isotope measurements on a sample of calcite (WC‐1) that has been and will continue to be used as a reference material for in situ U‐Pb Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) dating, and which is suitable to be distributed to the geochronological community. We present in situ measurements using LA‐ICP‐MS to demonstrate the suitability of WC‐1 for use as a U‐Pb dating reference material, in spite of it not being isotopically homogeneous. The WC‐1 calcite sample is 254.4 ± 6.4 Ma old and comprised 85–98% radiogenic lead. It presents a suitable reference material that can facilitate dating of calcite ranging in age from Precambrian to late Neogene age.
Key Points
We present a calcite reference material (WC‐1) for U‐Pb LA‐ICP‐MS geochronology
We provide isotope dilution reference values for WC‐1
WC‐1 can be used for normalization of U‐Pb LA‐ICP‐MS data
Reference materials (RMs) with well‐characterised composition are necessary for reliable quantification and quality control of isotopic analyses of geological samples. For in situ Rb‐Sr analysis of ...silicate minerals via laser ablation inductively coupled plasma tandem mass spectrometry (LA‐ICP‐MS/MS) with a collision/reaction cell, there is a general lack of mineral‐specific and matrix‐matched RMs, which limits wider application of this new laser‐based dating technique to certain minerals. In this work, pressed nano‐powder pellets (NP) of four RMs, GL‐O (glauconite), Mica‐Mg (phlogopite), Mica‐Fe (biotite) and FK‐N (K‐feldspar), were analysed and tested for in situ Rb‐Sr dating, complemented by isotope dilution (ID) MC‐ICP‐MS Rb‐Sr analyses of GL‐O and Mica‐Mg. In addition, we attempted to develop alternative flux‐free and fused ‘mineral glasses’ from the above RMs for in situ Rb‐Sr dating applications. Overall, the results of this study showed that among the above RMs only two NP (Mica‐Mg‐NP and GL‐O‐NP) were suitable and robust for in situ dating applications. These two nano‐powder reference materials, Mica‐Mg‐NP and GL‐O‐NP, were thus used as primary RMs to normalise and determine Rb‐Sr ages for three natural minerals: MDC phlogopite and GL‐O glauconite grains, and also Mica‐Fe‐NP (biotite). Our in situ analyses of the above RMs yielded Rb‐Sr ages that are in good agreement (within 8%) of published ages, which suggests that both Mica‐Mg‐NP and GL‐O‐NP are suitable RMs for in situ Rb‐Sr dating of phlogopite, glauconite and biotite. However, using secondary RMs is recommended to monitor the quality of the obtained ages.
Key Points
Suitable matrix‐matched reference materials for in situ Rb‐Sr dating by LA‐ICP‐MS/MS are needed to apply the technique to wider applications.
Mica‐Mg‐NP and GL‐O‐NP are suitable reference materials to date phlogopite and glauconite samples.
Use of secondary reference materials is recommended to monitor the quality of the produced ages.
Epoxy molding compounds are the most commonly used composite material for encapsulation in the semiconductor industry. They consist of a polymer-based matrix, inorganic filler particles, and a wide ...range of (in)organic additives to fine-tune the properties. As the encapsulation material is in direct contact with the delicate semiconductor components, the reliability and lifetime of electronic devices heavily depend on applying an appropriate type of encapsulation material. Semiconductor manufacturers typically obtain epoxy molding compounds from specialized external suppliers. Therefore, quality control checking if the correct molding compound was obtained and whether its properties deviate from previous batches is of great interest to the semiconductor industry. In this work, we investigate the capabilities of a Tandem LA-ICP-MS/LIBS approach to comprehensively characterize epoxy molding compounds to construct a classification model capable of distinguishing between different molding compound types. Tandem LA-ICP-MS/LIBS enables detection of the elemental composition of all relevant components within epoxy molding compounds: LIBS can detect polymer-specific signals and the major and minor elements present in the matrix (inorganic filler particles and additives). LA-ICP-MS provides information about elements present at trace levels (e.g., contaminations), which can provide information about batch-to-batch variations. We analyzed 29 samples of 20 molding compound types from 4 different suppliers. Using exploratory data analysis (PCA and HCA), we investigated the spectral fingerprint of the different molding compound types. Finally, a Random Decision Forest-based classifier is optimized and characterized, and a model is constructed. The final classifier is tested with independent samples that were not part of the training set, revealing a satisfying performance and highlighting some molding compound types that are difficult to distinguish.
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•Tandem LA-ICP-MS/LIBS method for quality control in the semiconductor industry.•Exploratory data analysis and development of a classification model.•Machine learning based elemental fingerprinting.
The development of sector zoning in clinopyroxene is attributed to the influence of crystallisation kinetics imposed by magma undercooling (ΔT) and may reflect variations in magma cooling histories. ...Yet, the degree of compositional variations between sectors has not been explored as a potential recorder of crystallisation dynamics. Here, we investigate the distribution of major, minor, and trace elements between hourglass {−111} and prism {h k 0} sectors in clinopyroxene with distinct pre-eruptive histories at Mt. Etna, Italy. We analyse sector-zoned clinopyroxene crystals ranging in size from sub-mm to cm (i.e., microphenocrysts, phenocrysts, and megacrysts), from eruptions fed by the central conduits of the volcano (1669 and 2002–03 flank eruptions) and eruptions fed by eccentric dykes which bypass the central conduits, tapping deeper magma storage regions (1974 and 2002–03 flank eruptions). We focus on Cr-rich mantle zones, which crystallised upon eruption triggering mafic rejuvenation and are ubiquitous across our sample set. With decreasing crystal size (i.e., increasing ΔT), tetrahedral aluminium is more strongly partitioned between prism and hourglass sectors. This promotes the uptake of rare earth elements (REE) and high field strength elements (HFSE) into prism relative to hourglass sectors. Combining relative degrees of sector enrichment with ΔT estimates, we propose magma recharge, mush remobilisation and the onset of magma ascent imposed slightly higher ΔT in 1974 than in 2002–03 eruptions at Mt. Etna. Enhanced ΔT in 1974 could be related to vigorous mixing and rapid transport of magma with limited storage, resulting in crystals of smaller sizes. Crystal size populations vary across eruptions, but crystals within a given population (e.g., phenocrysts) return similar calculated ΔT and REE + HFSE sector enrichments, implying connectivity between magmatic environments in the mush system. We show that the magnitude of sector zoning in clinopyroxene can be employed to explore subtle differences in pre-eruptive dynamics in volcanic systems. As an example, we explore sector enrichment in clinopyroxene phenocrysts from the 2021 eruption at La Palma (Canary Islands) and megacrysts from Roman era activity at Stromboli (Italy). Results highlight the role of dynamic mixing and mush remobilisation before eruption in mafic alkaline settings and suggest changes in magma composition across alkaline systems influence clinopyroxene chemistry but do not influence sector enrichment.
We report isotope dilution thermal ionization mass spectrometry (ID-TIMS) and laser ablation split stream inductively coupled plasma mass spectrometry (LASS) UPb data for a suite of widely available ...reference apatites: Fish Canyon Tuff, Mount Dromedary, TEMORA 2, and Duluth Complex anorthosite. We apply different common-Pb correction strategies to the UPb data sets: (1) anchoring to a Stacey and Kramers (1975) model Pb composition; (2) unanchored 2-D 238U/206Pb-207Pb/206Pb isochron regressions; and (3) unanchored 3-D 238U/206Pb-207Pb/206Pb-204Pb/206Pb isochron regressions. The different common-Pb corrections yield consistent dates within each ID-TIMS and LASS data set, with 3-D regression method producing the highest precision isochrons. FCT apatite produces an ID-TIMS 3-D isochron age of 28.8 ± 3.7 Ma with (207Pb/206Pb)i = 0.851 ± 0.021. Mount Dromedary apatite yields an ID-TIMS 3-D isochron age of 98.4 ± 0.5 Ma with (207Pb/206Pb)i = 0.839 ± 0.003. TEMORA 2 apatite has an ID-TIMS 3-D isochron age of 402 ± 7 Ma and (207Pb/206Pb)i = 0.839 ± 0.008. Duluth Complex anorthosite apatite yields an ID-TIMS 3-D isochron age of 1077 ± 9 Ma with (207Pb/206Pb)i = 0.849 ± 0.046. The MSWDs associated with isochrons calculated from both the ID-TIMS and LASS data sets are larger than expected for a single age population, revealing complexities that are otherwise not captured by 2-D isochron methods. In the case of FCT apatite, the ID-TIMS data indicate significant heterogeneity in the initial Pb ratio ((207Pb/206Pb)i = 0.845–0.856), invalidating this sample as a viable reference apatite for high-precision geochronology. Additionally, the common-Pb compositions of TEMORA 2 and Duluth Complex anorthosite apatites calculated using the ID-TIMS data deviate from bulk Earth Pb evolution models beyond 2σ uncertainty. The data emphasize the utility of unanchored age regressions in generating the highest fidelity apatite UPb dates. Further, TEMORA 2 and Duluth Complex apatite ages are both younger than their corresponding zircon UPb ages, highlighting the need to independently verify the ages of prospective reference apatites.
Three synthetic reference glasses were prepared by directly fusing and stirring 3.8 kg of high‐purity oxide powders to provide reference materials for microanalytical work. These glasses have ...andesitic major compositions and are doped with fifty‐four trace elements in nearly identical abundance (500, 50, 5 µg g−1) using oxide powders or element solutions, and are named ARM‐1, 2 and 3, respectively. We further document that sector‐field (SF) ICP‐MS (Element 2 or Element XR) is capable of sweeping seventy‐seven isotopes (from 7Li to 238U, a total of sixty‐eight elements) in 1 s and, thus, is able to quantify up to sixty‐eight elements by laser sampling. Micro‐ and bulk analyses indicate that the glasses are homogeneous with respect to major and trace elements. This paper provides preliminary data for the ARM glasses using a variety of analytical techniques (EPMA, XRF, ICP‐OES, ICP‐MS, LA‐Q‐ICP‐MS and LA‐SF‐ICP‐MS) performed in ten laboratories. Discrepancies in the data of V, Cr, Ni and Tl exist, mainly caused by analytical limitations. Preliminary reference and information values for fifty‐six elements were calculated with uncertainties 2 relative standard error (RSE) estimated in the range of 1–20%.
Key Points
Three synthetic andesite reference glasses (ARM‐1, ARM‐2 and ARM‐3) were prepared, and characterised by a variety of analytical techniques.
The homogeneity of the ARM glasses was evaluated by multiple EPMA and LA‐ICP‐MS spot analyses on randomly selected glass splits.
Preliminary reference values of the ARM glasses are provided.
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