Granites may be subdivided according to their intrusive settings into four main groups—ocean ridge granites (ORG), volcanic arc granites (VAG), within plate granites (WPG) and collision granites (COLG)—and the granites within each group may be further subdivided according to their precise settings and petrological characteristics. Using a data bank containing over 600 high quality trace element analyses of granites from known settings, it can be demonstrated using ORG-normalized geochemical patterns and element-SiO2 plots that most of these granite groups exhibit distinctive trace element characteristics. Discrimination of ORG, VAG, WPG and syn-COLG is most effective in Rb-Y-Nb and Rb-Yb-Ta space, particularly on projections of Y-Nb, Yb-Ta, Rb-(Y + Nb) and Rb—(Yb + Ta). Discrimination boundaries, though drawn empirically, can be shown by geochemical modelling to have a theoretical basis in the different petrogenetic histories of the various granite groups. Post-collision granites present the main problem of tectonic classification, since their characteristics depend on the thickness and composition of the lithosphere involved in the collision event and on the precise timing and location of magmatism. Provided they are coupled with a consideration of geological constraints, however, studies of trace element compositions in granites can clearly help in theelucidation of post-Archaean tectonic settings.

/pdf/trace-element-discrimination-diagrams-for-the-tectonic-14168jefci.pdf

Trace element discrimination diagrams for the tectonic interpretation of granitic rocks

http://www.usu.edu/geo/shervais/Shervais%20-%20My%20Articles/Shervais1982.pdf

Ti-V plots and the petrogenesis of modern and ophiolitic lavas

In this Special Issue, working values are reported for 383 international geostandards along with sample description. All this information is available in the form of databases. The possibility of easily accessing data on geostandards from a microcomputer in the laboratory itself is an efficient means for handling quality control/ quality assurance problems.

1994 compilation of working values and sample description for 383 geostandards

Slab breakoff: A model of lithosphere detachment and its test in the magmatism and deformation of collisional orogens

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

Portable X-ray fluorescence (PXRF) instrumentation has some unique analytical capabilities for the in situ analysis of samples in the field. These capabilities have been extended in recent years by the continuing development of solid state detectors, surface mounted electronics, digital signal processing technology, Li-ion batteries combined with a choice of rugged sealed radioisotope sources or miniature X-ray tubes that provide lightweight hand-held devices. 

As well as opening up new applications, in situ measurements by PXRF, where the instrument is placed in direct contact with the object to be analysed, involve the complete integration of sampling and analysis. Careful interpretation of results is therefore required, particularly when the analysis is used to estimate the bulk composition of a sample. 

In this monograph, an overview is given of instrumentation, analytical capabilities, and limitations in the interpretation of results, sampling considerations and applications where PXRF offers substantial advantages over conventional analytical techniques. The aim is to give the reader an insight into the capabilities of the technique and to demonstrate the contribution it can make to a range of areas of contemporary scientific interest. 

Chapters are written by internationally recognised scientists with practical experience of in situ analysis using portable X-ray fluorescence and demonstrates the wide range of applications for the technique. The topics covered are illustrated with diagrams and photographs where appropriate and each chapter includes supporting references to enable the reader to gain a greater understanding of a particular application. 

Topics include: 
-analytical capabilities 
-instrumentation 
-quantification 
-correction procedures 
-sampling considerations 
-future developments 

Applications include: 
-the assessment of contaminated land 
-surfaces 
-coatings and paints 
-workplace monitoring 
-metal & alloy sorting 
-geochemical prospecting 
-archaeological investigations 
-museum samples & works of art 
-extraterrestrial analysis 

The work is aimed at scientists who have some knowledge of analytical techniques and/or the applications covered, but are not fully familiar with the capabilities of PXRF. It offers a general introduction to the technique and its applications rather than a research monograph. As such, it is aimed at analytical scientists, environmental and geological scientists, industrial hygienists, industrial and plant scientists, archaeometrists and museum researchers, research scientists and research students with projects in the applications covered. Undergraduate students studying associated degree courses will also benefit from the work.

Portable x-ray fluorescence spectrometry : capabilities for in situ analysis

Along the Western Alps there is geological evidence of late-Alpine (Oligocene) magmatic activity which clearly postdates the Lepontine (Eocene-early Oligocene) metamorphism and related deformation of the Alpine nappe pile. This magmatic activity was notably delayed in relation to the most important convergent processes and may be related to buoyancy of lithosphere, tensional tectonics and thermal updoming subsequent to the collision between the Eurasian and African plates. The geochemical features of the rocks and the geophysical characteristics of the Alpine chain, suggest that: (a) shoshonitic and calcalkaline melts may have been generated by partial melting of metasomatized peridotitic material and subsequent fractional crystallization and crustal contamination; silicic andesites and latites, however, could have been also derived from metasomatized eclogite or deep continental crust material; (b) the ultrapotassic lamprophyres with high K, P, LREE, Th, Zr, U and high 87Sr/86Sr ratios were generated by partial melting of strongly metasomatized mantle; the varied Sr-isotopic ratios may partially also reflect additional radiogenic component from the continental crust following magma segregation from the source.

Petrogenesis of calc-alkaline, shoshonitic and associated ultrapotassic Oligocene volcanic rocks from the Northwestern Alps, Italy

An objective assessment of analytical method precision: comparison of ICP-AES and XRF for the analysis of silicate rocks

This compilation report describes the field location, mineralogy, preparation and homogeneity testing of two new GIT-IWG reference materials: Whin Sill dolerite (WS-E) from England and Pitscurrie microgabbro (PM-S) from Scotland. The elemental composition of these two new reference materials has been established by an international cooperative analysis programme involving participation by 104 laboratories. A full assessment of these analytical results is presented, from which working values have been derived for the major elements as well as for 45 trace elements in WS-E and 44 trace elements in PM-S. Furthermore, isotopic ratios are presented for both samples, particularly for 87Sr/86Sr and 143Nd/144Nd.

1994 report on whin sill dolerite ws-e from england and pitscurrie microgabbro pm-s from scotland: assessment by one hundred and four international laboratories

Abundances of 9 Rare-Earth Elements are reported for 21 andesite and dacite samples from a small group of volcanoes in the North Chilean segment of the Andean plate margin. The data are correlated with major and trace element data (Roobol et al., in press) and are used to critically assess several models proposed to account for the origin of andesite. A three-stage model for andesite petrogenesis is proposed. This involves: (i) initiation of melting at the subduction zone and rise of magmas into the overlying mantle-wedge, which thereby becomes richer in garnet-pyroxene components and large-ion lithophile (LIL) elements, (ii) partial melting of this LIL-enriched garnet pyroxenite material to form andesitic magmas within the mantle wedge, (iii) minor crystal fractionation during rise through the crust.

Philip J. Potts

Papers

Portable x-ray fluorescence spectrometry : capabilities for in situ analysis

Petrogenesis of calc-alkaline, shoshonitic and associated ultrapotassic Oligocene volcanic rocks from the Northwestern Alps, Italy

An objective assessment of analytical method precision: comparison of ICP-AES and XRF for the analysis of silicate rocks

1994 report on whin sill dolerite ws-e from england and pitscurrie microgabbro pm-s from scotland: assessment by one hundred and four international laboratories

Rare Earth data and petrogenesis of andesite from the North Chilean Andes