Microchim. Acta 145, 139–146 (2004) DOI 10.1007/s00604-003-0143-9 Original Paper New SIMS Procedures for the Characterization of a Complex Silicate Matrix, Na 3 (REE,Th,Ca,U)Si 6 O 15 à 2.5H 2 O (Sazhinite), and Comparison with EMPA and SREF Results Luisa Ottolini 1; , Fernando Ca ´mara 1 , and Bertrand Devouard 2 1 CNR, Istituto di Geoscienze e Georisorse (IGG), Sezione di Pavia, Via Ferrata, 1, I-27100 Pavia, Italy 2 Laboratoire Magmas et Volcans (UMR 6524), OPGC – Universit  e Blaise Pascal – CNRS, 5, rue Kessler, F-63038 Clermont-Ferrand cedex, France Received May 22, 2003; accepted October 20, 2003; published online February 23, 2004 # Springer-Verlag 2004 Abstract. Analytical methods based on secondary ion mass spectrometry were developed for the character- isation of a complex layered silicate REE-mineral, named sazhinite, for which a number of issues are still open regarding its chemistry and structure. Such procedures involved the analysis and quantification of light, volatile, alkaline, medium-Z, rare earth and actinide elements. The accuracy of the SIMS data is within the assigned precision of the concentration values assumed as reference in the calibration stan- dards employed. REE and actinide data yield a good agreement in terms of calculated site scattering at the M site: 58.42 electrons per formula unit (epfu) vs. 60.39 epfu obtained by Single Crystal Structure- Refinement (SREF). Accuracy is estimated on the order of 5% rel. for H, Li, Be and B, and 10% rel. for F. Na analysis was crucial to solve the open ques- tions about the structure, and excellent agreement was obtained by comparing data from SIMS (REE, Y, actinides, Na) þ EMPA (SiO 2 , CaO, SO 3 and K 2 O) with information derived from SREF: site scattering of the M site þ Na sites ¼ 92.56 epfu calculated from chemical data, against 91.95 epfu from SREF. Such procedures can be easily extended to the analysis of variously complex, silicate REE-minerals. Key words: SIMS; EMPA; SREF; REE and actinides; light and volatile elements; sazhinite. Sazhinite is a layered REE-, volatile-rich mineral, with simple wavy layers of silicon tetrahedra [Si 6 O 15 ] 6 that are linked by REE in seven-fold coor- dination (capped octahedron). The silica–REE frame- work gives rise to channels that host alkali cations and water molecules. Studies on analogous MSi 6 O 15 - based silicates ([1] and references therein) report high metal exchange properties for similar frameworks. Sazhinite was first described as Na 3 CeSi 6 O 15  6(H 2 O) [2] occurring in the Jubilee alkaline pegmatite at Mt. Karnasurt, Lovozer massif, Kola Peninsula (Russia). Shumyatskaya et al. (1980) [3] described its structure. Since then, it has only been reported in two additional localities: at the Poudrette quarry, Mont Saint-Hilaire, Qu ebec, Canada [4, 5], and at the Demix-Varennes quarry, Saint-Amable sill, Varennes, Verch eres Co., Qu ebec, Canada [6]. A number of issues are still open regarding its chemistry and structure: the species and quantity of alkali cations, and coordinating water molecules within the channels; accurate quantification of REE  Author for correspondence. E-mail: ottolini@crystal.unipv.it