In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard

The chemical composition of subducting sediment and its consequences for the crust and mantle

Microanalytical trace element techniques (such as ion probe or laser ablation ICP-MS) are hampered by a lack of well characterized, homogeneous standards. Two silicate glass reference materials produced by National Institute of Standards and Technology (NIST), NIST SRM 610 and NIST SRM 612, have been shown to be homogeneous and are spiked with up to sixty one trace elements at nominal concentrations of 500 μg g-1 and 50 μg g-1 respectively. These samples (supplied as 3 mm wafers) are equivalent to NIST SRM 611 and NIST SRM 613 respectively (which are supplied as 1 mm wafers) and are becoming more widely used as potential microanalytical reference materials. NIST however, only certifies up to eight elements in these glasses. Here we have compiled concentration data from approximately sixty published works for both glasses, and have produced new analyses from our laboratories. Compilations are presented for the matrix composition of these glasses and for fifty eight trace elements. The trace element data includes all available new and published data, and summaries present the overall average and standard deviation, the range, median, geometric mean and a preferred average (which excludes all data outside ± one standard deviation of the overall average). For the elements which have been certified, there is a good agreement between the compiled averages and the NIST data. This compilation is designed to provide useful new working values for these reference materials.

A Compilation of New and Published Major and Trace Element Data for NIST SRM 610 and NIST SRM 612 Glass Reference Materials

Improved 206Pb/238U microprobe geochronology by the monitoring of a trace-element-related matrix effect; SHRIMP, ID-TIMS, ELA-ICP-MS and oxygen isotope documentation for a series of zircon standards

We present new reference values for the NIST SRM 610–617 glasses following ISO guidelines and the International Association of Geoanalysts’ protocol. Uncertainties at the 95% confidence level (CL) have been determined for bulk- and micro-analytical purposes. In contrast to former compilation procedures, this approach delivers data that consider present-day requirements of data quality. New analytical data and the nearly complete data set of the GeoReM database were used for this study. Data quality was checked by the application of the Horwitz function and by a careful investigation of analytical procedures. We have determined quantitatively possible element inhomogeneities using different test portion masses of 1, 0.1 and 0.02 μg. Although avoiding the rim region of the glass wafers, we found moderate inhomogeneities of several chalcophile/siderophile elements and gross inhomogeneities of Ni, Se, Pd and Pt at small test portion masses. The extent of inhomogeneity was included in the determination of uncertainties. While the new reference values agree with the NIST certified values with the one exception of Mn in SRM 610, they typically differ by as much as 10% from the Pearce et al. (1997) values in current use. In a few cases (P, S, Cl, Ta, Re) the discrepancies are even higher.



Nous presentons des nouvelles valeurs de reference pour les verres NIST SRM 610–617 en suivant les recommandations de l’ISO et le protocole de l’IAG. Les incertitudes au niveau de confiance de 95% ont ete determinees a des fins d’analyse totale et de micro-analyse. Contrairement aux procedures de compilation precedentes, cette approche fournit des donnees qui tiennent compte des exigences actuelles dans la qualite des donnees. De nouvelles donnees analytiques et le jeu de donnees presque complet de la base de donnees GeoReM ont ete utilises pour cette etude. La qualite des donnees a ete verifiee par l’application de la fonction de Horwitz et par un examen minutieux des procedures analytiques. Nous avons determine quantitativement les possibles inhomogeneites d’element en utilisant des prises d’essai de masses differentes correspondant a 1, 0.1 et 0.02 μg. Bien que nous ayons evite les zones de bordure des disques de verre, nous avons trouve des inhomogeneites moderees pour plusieurs elements chalcophiles/siderophiles et des inhomogeneites flagrantes de Ni, Se, Pd et Pt pour les prises d’essai de petites masses. La mesure d’inhomogeneite a ete incluse dans la determination des incertitudes. Alors que les nouvelles valeurs de reference sont en accord avec les valeurs NIST certifiees a la seule exception du Mn dans SRM 610, elles sont generalement differentes, avec des ecarts de pres de 10%, des valeurs de Pearce et al. (1997) qui sont d’un usage courant. Dans quelques cas (P, S, Cl, Ta, Re), les ecarts sont encore plus eleves.

Determination of Reference Values for NIST SRM 610–617 Glasses Following ISO Guidelines

The origin of the fractionation of platinum-group elements in terrestrial magmas

Three distinct tectonic regimes were identified for felsic and intermediate volcanic rocks using published datasets from twenty-six different geographical locations around the world. The three well-defined tectonic regimes include oceanic arcs, active continental margins and within-plate volcanic zones. This subdivision is based on concentrations and ratios of the incompatible trace elements Ta, Th and Yb as geochemical tectonic discriminants. The separation of tectonic regimes is demonstrated on two discriminant diagrams, where the three zones are separated by ca. 45° diagonal lines on one, and by horizontal lines on the other. The ca. 45° trends of the boundaries between tectonic provinces on a Ta/Yb versus Th/Yb diagram are due to the similar incompatibility of Th and Ta relative to the somewhat lower incompatibility of Yb. On a Th/Ta versus Yb diagram, the three tectonic zones are separated by horizontal lines; datasets within individual zones have characteristic Th/Ta values, ca. 1–6 for within-plate volcanic zones, >6–20 for active continental margins, and >20–90 for oceanic arcs. These discriminant diagrams can be successfully used to identify the tectonic environments of intermediate and felsic volcanic rocks, and to evaluate the tectonic history of a region.

From continents to island arcs: a geochemical index of tectonic setting for arc-related and within-plate felsic to intermediate volcanic rocks

Archaean felsic metavolcanic rocks in the Superior Province of the Canadian Shield may be divided into three major groups on the basis of trace-element abundances and ratios. (1) FI felsic metavolc...

Trace-element geochemistry of ore-associated and barren, felsic metavolcanic rocks in the Superior Province, Canada

High field strength element ratios in felsic volcanic rocks reflect the tectonomagmatic evolution of a region. Th/Ta, Th/Hf, Ta/Hf, Th/Yb, and Ta/Yb ratios collectively help to define the tectonic environment of volcanism, separating oceanic arcs, active continental margins, and within-plate volcanic zones. On the basis of the above empirical observations, the tectonic environments of selected Archean and post-Archean volcanogenic massive sulfide deposits were reexamined. Published data sets plotted on discriminant diagrams represent twelve volcanogenic massive sulfide (VMS) deposits from two distinct tectonic environments. The volcanic rocks of the kuroko deposits (Japan), San Nicolas (Mexico), and Bathurst (New Brunswick, Canada) plot within the active continental margin field on all diagrams, whereas volcanic rocks from Archean deposits of the Superior province, Canada (Kidd Creek, Kamiskotia, Geco, Winston Lake, Mattabi, Lyon Lake, Noranda, Selbaie, and South Bay) plot in the within-plate volcanic zone field.

The discriminant diagrams demonstrate that although the chemical character of rhyolites has not changed significantly since the Archean, the range of geotectonic setting of VMS deposits probably has. It is suggested that Archean deposits most likely formed in an ensimatic rift environment, whereas post-Archean deposits formed in subduction-related rift zones of arc environments. Subduction-related rhyolites of VMS deposits are variably enriched in Th and the light rare earth elements with respect to Ta, Nb, and the heavy rare earth elements.

Michael P. Gorton

Papers

A Compilation of New and Published Major and Trace Element Data for NIST SRM 610 and NIST SRM 612 Glass Reference Materials

The origin of the fractionation of platinum-group elements in terrestrial magmas

From continents to island arcs: a geochemical index of tectonic setting for arc-related and within-plate felsic to intermediate volcanic rocks

Trace-element geochemistry of ore-associated and barren, felsic metavolcanic rocks in the Superior Province, Canada

Application of high field strength elements to discriminate tectonic settings in vms environments