HR: 0800h
AN: V41E-1514    [Abstracts]
TI: Investigating NanoSIMS to analyse synthetic ultrahigh-pressure samples
AU: Perrillat, J
EM: jperrill@uiuc.edu
AF: Laboratoire de Sciences de la Terre, UMR5570-CNRS-UCBLyon1-ENS Lyon, 2 Rue Raphael Dubois, Villeurbanne, 69622 France
AU: Perrillat, J
EM: jperrill@uiuc.edu
AF: Department of Geology, University of Illinois, 1301 W Green St, Urbana, IL 61801 United States
AU: * Daniel, I
EM: Isabelle.Daniel@univ-lyon1.fr
AF: Laboratoire de Sciences de la Terre, UMR5570-CNRS-UCBLyon1-ENS Lyon, 2 Rue Raphael Dubois, Villeurbanne, 69622 France
AU: Mostefaoui, S
EM: smail@mnhn.fr
AF: Laboratoire d'Etude de la Matiere Extraterrestre, USM0205, Museum National d'Histoire Naturelle, 61 Rue Buffon, Paris, 75000 France
AU: El Goresy, A
EM: Ahmed.Elgoresy@uni-bayreuth.de
AF: Max-Planck-Institut fur Chemie, Otto Hahn Institut, Mainz, 55128 Germany
AU: El Goresy, A
EM: Ahmed.Elgoresy@uni-bayreuth.de
AF: Bayerisches Geoinstitut, Universitat Bayreuth, Bayreuth, 95440 Germany
AU: Bohn, M
EM: bohn@ifremer.fr
AF: IFREMER UMR6538-CNRS, Centre de Brest, Plouzane, 29280 France
AB: Our knowledge of the deep Earth's mineralogy is primarily based on the results of high-pressure high-temperature experiments, through the determination of both structure and composition of the product phases. Whereas synchrotron X-ray radiation is successfully used to identify the structure of phases, their chemical analysis is still a challenging task, considering the very small amount and very fine grain size of recovered samples. ATEM is currently the mostly used technique to measure the major elements composition of minerals at sub-micron scale. However, this technique requires a difficult and destructive sample preparation by either ion thinning or ultramicrotomy. Here, we investigate the suitability of NanoSIMS in quantifying the major and trace elements concentrations of high-pressure phases. Indeed, this new generation of ion microprobe is characterized by high spatial resolution (beam size down to 50 nm), high sensitivity, the simultaneous detection of up to 6 isotopes, and only requires polished surfaces for analysis. Preliminary experiments were performed with the Cameca NanoSIMS 50 installed at the Max-Planck-Institut fur Chemie, on a sample of basaltic composition synthesized at 25GPa and 1673 K. A primary beam of O- ions was focused to ~ 350 nm on the sample surface. Areas of 9 x 9 microns, with grains in the range 0.1 to 5 microns, were scanned to acquire secondary ions images of 28Si, 24Mg, 40Ca, 56Fe, 23Na, 27Al. Ratio images of each area were obtained by normalizing the measured isotopes to 28Si. The relative sensitivity factors of the analyzed isotopes were determined by analyzing several standards in order to calibrate the data. To determine the accuracy of the analysis, calculated elemental ratios were compared with electron microprobe measurements. Analytical uncertainties appear to be minimized by the use of an internal standard, i.e. an area of the sample whose composition is known accurately. The nature and chemistry of high-pressure phases in MORB composition are briefly discussed in the light of these analytical results.
DE: 1025 Composition of the mantle
DE: 3630 Experimental mineralogy and petrology
DE: 3994 Instruments and techniques
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005