Sandimirov S.S. Geochemisrty of water-rock interaction in the area of the Khibiny alkaline massif. Geochemisrty International. 2007, T.54, №11, p. 1103-1110.

1108 DUDKIN, SANDIMIROV Table 4. Major-component composition of the bottom sedi­ ments (wt %) Oxide 1 2 Oxide 1 2 Si02 37.4 39.2 MnO 0.2 0.2 Ti02 1.5 1.5 SrO 0.6 0.6 a i 2 o 3 17.4 19.3 Na20 5.2 6.6 CaO 10.8 8.9 k 2 o 3.5 4.5 MgO 1.4 1.5 p 2 o 5 8.0 7.1 FeO 6.3 6.3 Total 93.7 96.7 Note: (1) Whole-rock analysis and (2) fraction <0.002 mm. Ana­ lyst Ya.A. Pakhomovskii, Geological Institute, Kola Scien­ tific Center, Russian Academy of Sciences. technique without reagents or additional grinding and heating. The results are given in Table 4. Standard grain-size analysis was used for the den­ sity separation of solid particles in a control sample in water without precipitating fine fraction by reagents. The fraction >0.01 mm accounted for 32.5%; fraction 0.01-0.002 mm, for 35.3%; fraction <0.002 mm, only for 0.07%; and the loss was 32.1%. The significant loss could be caused by the large volume of distilled water that was used in this method. This could lead to the loss and dissolution of low-density fine solid particles and colloidal phases. The X-ray diffraction patterns of the whole-rock sample of bottom sediments and all its frac­ tions revealed a high content of dispersed phases, which was confirmed by IR spectrometry (O.A. Zalkind, Insti­ tute of Rare Element and Mineral Chemistry and Tech­ nology, Kola Research Center, Russian Academy of Sci­ ences). The microscopic examination of the >0.01 mm fraction in immersion oils confirmed the presence of an isotropic phase with a low refractive index. It is evident that the amorphous phase was partially retained in all size fractions. In addition to nepheline and apatite, the examination of the >0.01 mm fraction in immersion oil revealed sig­ nificant amounts of quartz and feldspars and the pres­ ence of amphibole and chlorite. This suggests that con­ siderable amounts of the material of the country rocks of the Khibiny Massif were delivered by the river to the lake. However, the major components of the sediments are nepheline and apatite (Table 1, Fig. 4). The X-ray diffraction patterns (Fig. 4) indicate that the maximum effect of apatite production is confined to the fine frac­ tions of the top layer of lake sediments. The microprobe analyses of pressed pellets showed that the composition of the <0.002 mm fraction (Table 4, an. 2) is close to the bulk composition of the suspen­ sions. At the same time, this fraction has elevated con­ tent of nepheline constituents (Table 4). The intensity of nepheline lines in the X-ray diffraction pattern of this fraction decreases sharply relative to the apatite lines (Fig. 4). The observed features of the composition of the fine fraction are similar to those in the experiments Fig. 4. Fragments of X-ray diffraction patterns of bottom sediments with particles >0.01 mm (lower), 0.01-0.02 mm (middle), and <0.002 mm (upper). on the decomposition of nepheline into dispersed phases. DISCUSSION AND CONCLUSIONS The contents of the major elements of the Khibiny rocks increase sequentially from the surface water of the Khibiny Massif to underground waters and to the lacustrine waters of the zone affected by industrial wastes (Table 1). An exception is S i02, whose content decreases in the waters of the mixing zone, although the HEMISTRY INTERNATIONAL Vol. 45 No. 11 2007