Chemical Geology, 56 (1986) 93--103 93 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands [31 DETERMINATION OF BERYLLIUM AND ITS DISTRIBUTION IN ROCKS OF THE Sn W GRANITE OF REGOUFE, NORTHERN PORTUGAL J.H.L. VONCKEN, S.P. VRIEND, J.W.M. KOCKEN and J.B.H. JANSEN Institute of Earth Sciences, Department of Geochemistry, 3508 TA Utrecht (The Netherlands) (Received January 2, 1986; accepted for publication January 14, 1986) Abstract Voncken, J.H.L., Vriend, S.P., Kocken, J.W.M. and Jansen, J.B.H., 1986. Determination of beryllium and its distribution in rocks of the Sn--W granite of Regoufe, northern Portugal. Chem. Geol., 56: 93--103. The determination of Be by electrothermal atomic absorption spectrometry with Zeeman background correction (ZETAAS) is compared with the determination by inductively coupled plasma emission spec- trometry (ICPES). The samples are decomposed with a HF--HC104--HNO3 method. Both methods com- pare well though the results by ZETAAS are generally ~ 2 ppm higher than the ICPES values. Especially ICPES results are in good agreement with the accepted values for international reference samples. ZETAAS has a lower detection limit than ICPES. The methods were tested on 55 samples of the Regoufe granite, northern Portugal. The average for the Regoufe granite is 17 ppm Be, and the values range from 4 to 57 ppm Be. The granite may be regarded as Be-specialised. The distribution is compared with those of the elements Ti, P, Rb, Sr, Cu, Zn, U, Sn, W, Ta, Nb, F, Li and Cs, and with major minerals in the granite (feldspars and micas). Correlations with Be were generally low. From theoretical considerations and from statistical data it is concluded that Be is enriched in the final stages of the magma crystallisation and was mobile in all the major late- and post-magmatic processes in the granite. 1. Introduction Recently, the minor- and trace-element distribution of the W--Sn granite of Regoufe was studied by Vriend et al. (1985). They noted that the most incompatible elements in their data set, i.e. Li, Cs and U, deviated from the major greisenisation, albitisation and mineralisation trends. For a better understanding of this behaviour, the study of another incompatible element, Be, was undertaken. Controversy exists in the literature about the best method to determine Be. Therefore we compare the Be determination by ICPES with that of electrothermal atomic absorp- tion spectrometry with Zeeman background correction (ZETAAS). The Regoufe granite is situated ~ 70 km SE of Oporto and ~ 200 km N of Lisbon on the boundary of the provinces Douro Littoral and Beira Alta. Geologically the Regoufe granite belongs to the Hercynian massifs which are exposed over a large area in the northwest of the Iberian Peninsula (Fig. 1). The sampling and sample locations