Cumulate xenoliths erupted with alkalic hawaiite lavas from a postshield cinder cone on Mauna Kea, Hawaii include a variety of mafic and ultramafic rock types. Previous studies of major and trace element compositions of minerals in the xenoliths are interpreted to show transitional to alkalic magma parentages from the postshield stage, although any orthopyroxene-bearing xenoliths are considered to have tholeiitic parents. Major element compositions minerals were analyzed using the electron microprobe and trace element compositions of clinopyroxene grains were analyzed by laser ablation inductively coupled plasma mass spectrometry. In this study, major element compositions of clinopyroxene, olivine and plagioclase grains and trace element compositions in clinopyroxene grains in xenoliths lacking orthopyroxene indicate a transitional magma parentage consistant with postshield magmas. Trace element compositions of possible parent magmas of the xenoliths were calculated from clinopyroxene compositions using partition coefficients for basaltic liquids from Hauri et al. (1994). Liquids calculated from the clinopyroxene in the xenoliths were compared to Mauna Kea shield lavas and to the postshield Hamakua and Laupahoehoe units. Chondrite-normalized rare earth element (REE) patterns of liquids calculated from both orthopyroxene-bearing xenoliths and those without orthopyroxene were similar REE patterns of both Mauna Kea postshield tholeitic and alkalic lavas. Liquids from a wehrlite and an olivine gabbronorite have REE patterns similar to tholeiitic shield basalts. To better distinguish the transitional xenolith sources as one of Mauna Kea's two postshield substages, the older, basaltic Hamakua unit or the younger hawaiitic Laupahoehoe unit, variation diagrams compared calculated liquid compositions to Mauna Kea lavas from the shield and postshield stages. Calculated liquid trace element concentrations are similar to those of Hamakua lavas.

The Cedar Mountain Formation contains the most diverse record of Early Cretaceous dinosaurs in the western hemisphere. However, analyses of its faunas have been hindered because 1) most taxa are based on incomplete/fragmentary materials or incomplete descriptions, 2) most sites and some horizons preserve few taxa, and 3) the stratigraphy and geochronology are poorly understood. To help resolve these stratigraphic and correlation problems U-Pb LA-ICP-MS detrital zircon ages were obtained at significant sites and horizons. These dates indicate all sites at or near the base of the formation are no older than 122 to 124 Ma, thus all basal stratigraphic packages are time equivalent. Detrital zircons coarsely bracket the temporal span of the Ruby Ranch Member between about 115 Ma to 111 Ma while the base of the Mussentuchit Member is dated between 108 to 104 Ma and the top of the member is Cenomanian in age. Multivariate analyses utilizing Simpson and Raup-Crick similarity index and pair-group moving algorithms reveal that formationfs faunas fall into two groups. These groups are compared statistically with European, Asian, and Morrison faunas. Results indicate (1) that there is no close relationship between the Yellow Cat fauna and the Morrison Formation fauna and (2) corroborate long-standing hypotheses that the Yellow Cat fauna has European ties and the Mussentuchit fauna has Asian ties. Detrital zircon LA-ICP-MS U-Pb ages were used in this study to approximate the time of deposition of strata because volcanic ashes are rarely preserved in the formation. The ability to select the youngest crystals in a sample prior to applying analytical methods could substantially reduce the number of crystals and cost required to obtain these dates. To this end, the hypothesis that the most pristine, unabraded crystals should be younger than abraded crystals was tested by imaging detrital zircons via SEM, ranking the crystals by the degree of abrasion, and determining their ages. Results of this study partly corroborate the hypothesis in that there is a correlation between the degree of abrasion and ages – obviously abraded crystals are most likely the oldest while pristine to slightly abraded crystals are usually the youngest in a given sample.

Elemental analysis in forensic laboratories can be tedious and many trace evidence items are not analyzed to determine their elemental composition. Presently, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS) is the primary analytical tool for determining the elemental composition of trace evidence items. However, due to the time it takes to obtain the required vacuum and the limited number of samples that can be analyzed at any one time, SEM-EDS can be impractical for a high volume of evidence items. An alternative instrument that can be used for this type of analysis is laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). While LA-ICP-MS is a very precise and quantitative analytical method that determines elemental composition based on isotopic mass measurements; however, the instrumentation is relatively expensive and therefore is budgetarily prohibitive for many forensic laboratories. It is the purpose of this research to evaluate an inexpensive instrument that can potentially provide rapid elemental analysis for many forensic laboratories. Laser induced breakdown spectroscopy (LIBS) is an analytical method that meets these requirements and offers information about the elemental composition based on ionic, atomic and diatomic molecular emissions.

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Boron treated test houses at Mississippi State University’s Dorman Lake test site in Starkville, MS were built in 1989 to investigate the effectiveness of boron treatments with exposure to natural weathering. After being undisturbed for more than 20 years, samples were taken to evaluate the remaining levels of original treatments in the test houses. Visual evaluation of the test structures, curcumin test, and ICP-MS analysis of the borate content shows borates are a capable and effective long-term treatment for wood used in construction. No appreciable damage due to termite feeding was observed. Boron was still detectable by curcumin staining and positive boron levels were confirmed by ICP-MS analysis.

Le mercure est un contaminant présent dans l'ensemble des compartiments de l'environnement et l'homme y est directement exposé via l'alimentation. Actuellement, les organismes gouvernementaux évaluent la sécurité des produits alimentaires en se basant essentiellement sur la concentration totale de cet élément. Cependant, la toxicité du mercure dépend, entre autre, de l'espèce absorbée (dont le méthylmercure, sa forme la plus toxique). Par conséquent, l'analyse de spéciation, c'est à dire la détection et quantification des différentes formes chimiques de cet élément, présente un intérêt croissant. Le principal objectif de ce projet a donc été de développer et de valider, sous assurance qualité, une méthode sensible et d'une grande exactitude, basée sur l'utilisation de la dilution isotopique. Elle sera par la suite appliquée comme méthode de référence par l'agence pour l'analyse en spéciation du mercure dans les produits de la pêche afin de permettre une meilleure évaluation des risques encourus par le consommateur. La première partie de ce travail a porté sur l'étude du cycle biogéochimique du mercure et de l'état de l'art des diverses méthodes de préparation de l'échantillon, de séparation et de quantification du Hg dans les matrices biologiques, afin d'émettre des choix analytiques. Ainsi, les principaux composés mercuriels susceptibles d'être retrouvés dans les produits de la pêche (le méthylmercure et le mercure inorganique) ont été déterminés par couplage GC-ICP-MS et une quantification par dilution isotopique. La seconde partie des travaux a été consacrée à l'optimisation de la méthode de préparation des échantillons et de la technique de quantification. Ces travaux sur différents matériaux de référence certifiés ont montré que des modifications de la distribution naturelle de l'échantillon pouvaient survenir dès l'étape d'extraction, préconisant un marquage isotopique avant extraction solide-liquide par digiPREP des espèces mercurielles et dérivation par propylation par le tétrapropylborate de sodium et agitation rotative. Les résultats expérimentaux ont été traités par dilution isotopique simple et multiple. Les teneurs obtenues ont été similaires, pour l'ensemble des matrices analysées, montrant que peu ou pas de transformation inter-espèces surviennent au cours de la procédure analytique. Une quantification par double marquage isotopique et dilution isotopique simple a donc été conservée. L'évaluation des critères analytique a démontré que la méthode est validée pour la spéciation du mercure dans les produits de la pêche, selon les normes françaises AFNOR NF V03-110 de 1998 et de 2010. La dernière partie des travaux a porté sur l'application de la méthode validée à la spéciation du mercure dans des échantillons biologiques réels, ainsi qu'à la participation à plusieurs essais interlaboratoires d'aptitudes organisés par le CSL-FAPAS sur un échantillon de thon en conserve et par l'IRMM sur le matériau IMEP-109 de homard. / Mercury is a contaminant which is found in all compartments of the environment and to which human beings are directly exposed when eating food. Government agencies assess the safety of food products by using total mercury concentrations. However, its toxicity depends on the species absorbed (among which methylmercury is its most toxic form). Therefore, the analysis of speciation, i.e. detection and quantification of different chemical forms of this element, is of high interest. The main objective of this project was to develop and validate, under quality assurance, a sensitive and highly accurate method, based on the use of isotope dilution. This method will then be applied as a reference method by the agency for speciation analysis of mercury in seafood, in order to better assess risks to the consumer. The first part of this work focused on the biogeochemical cycle of mercury and the state of art of the various methods of sample preparation, separation and quantification of Hg in biological matrices in order to make analytical choices. Thus, mercury compounds (methyl mercury and inorganic mercury) were determined by gas chromatography (GC) coupled with an inductively coupled plasma mass spectrometer (ICP-MS) and quantified by isotope dilution. The second part of the work was dedicated to the optimization of the method of sample preparation and the quantification technique. The work was made on different certified reference materials and showed that changes of the natural distribution of the sample could occur during the extraction step. Therefore, isotopic tracers had been added to the sample before this step. Mercury species were extracted by a solid-liquid extraction by using a digiPREP and derivated by propylation using tétrapropylborate the sodium and a rotary agitation. Data were treated by simple and multiple isotope dilution. Achieved concentrations were similar for all analyzed matrices. Results showed that inter-species transformation hardly occurred during the analytical procedure. This was the reason why the use of two isotopic tracers for quantification by simple isotope dilution was kept. To end, the method was validated for the speciation of mercury in seafood, in respect with the French norms AFNOR NF V03-110 of 1998 and 2010. Finally, the work ended with the applicability of the validated method for mercury speciation analysis in real biological samples and our participation in several inter-laboratory proficiency tests organized by the CSL-FAPAS on a sample of tuna and by the IRMM on the material IMEP-109 (lobster).