HR: 1400h
AN: V23B-02    [Abstracts]
TI: Characterization of the Geochemical Reference Material BRP-1 from Brazil: New Data from High Precision LA-ICPMS Analyses
AU: Enzweiler, J
EM: jacinta@ige.unicamp.br
AF: Instituto de Geociencias, UNICAMP, C.P. 6152, Campinas, SP 13083-970, Brazil
AU: * Jochum, K P
EM: kpj@mpch-mainz.mpg.de
AF: Max-Planck-Institut fuer Chemie, Postfach 3060, Mainz, 55020, Germany
AB: To get a well-characterized Brazilian basaltic reference material Cotta et al. (2007) prepared BRP-1, which was collected from the Cretaceous Parana Province. About 150 kg of the raw material was crushed and pulverized at the USGS in Denver, USA. Finally, the powder was split into 1920 glass bottles containing about 55 g of material. Homogeneity tests using XRF and microbeam-SRXRF showed that the material is homogeneous for most of the investigated elements. Representative minimum masses were 1 mg for major and 1 - 15 mg for trace elements. To get high-precision trace element data and to further test the homogeneity of BRP-1, we have applied a recently developed LA-ICPMS technique using an automated Ir-strip-heater (Stoll et al., 2007). About 40 mg of the rock powder was placed on an iridium strip. The melting of the sample took place in a closed box under an argon atmosphere to suppress oxidation and to limit volatilization of elements with low boiling points (e.g., Cs, Pb). In order to get reproducible conditions an automatic computer control served for 1650 ° C temperature using a pyrometer and heat up of 20 s, melting of 10 s and subside of 2 s. Fast cooling occurred by an Ar flow underneath. Using these conditions homogeneous glasses with no significant loss of volatile elements were obtained. Contamination from the high-purity iridium strip (99.955 %) was not detected with the exception of Ir whose concentration was about 20 ppm. Mass spectrometric analyses were performed with the double focusing Finnigan Element2 ICPMS and a new New Wave 193 nm Nd:YAG laser ablation system (Jochum et al., 2007). Matrix matched calibration was done with the reference glasses KL-2G and BCR-2G. BCR-2 was used as quality control material. We obtained a precision (1 RSD) of about 1 - 3 % for most trace elements. Our results obtained from two different bottles of BRP-1 agree within uncertainty limits confirming the homogeneity of BRP-1 in the mg range.
DE: 1065 Major and trace element geochemistry
DE: 1094 Instruments and techniques
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly