Tham khảo tài liệu 'earth sciences part 5', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 150 Earth Sciences The clinopyroxenes of the Khibiny massif predominating in the majority of rocks are represented by diopside hedenbergite augite aegirine-augite and aegirine Yakovenchuk et al. 2005 Yakovenchuk et al. 2008 . Diopside is a rock-forming mineral of alkali-ultrabasic rocks alkali-feldspar trachytes melteigite-urtite metamorphosed to hornfels volcanogenic-sedimentary rocks of basalt composition and their host foyaite. Hedenbergite is observed in fenitized hornfels after tuffite where it together with aegirine forms parallel-columnar coronas around fayalite inclusions in albite. Aegirineaugite is the main mineral of all types of nepheline syenites 5-50 vol. foidolites up to 90 vol. apatite-nepheline rocks fenitized rocks of the massif frame and xenoliths of volcanogenic-sedimentary rocks in foyaite. In foyaite of the outer and central parts of the massif it predominates among the other iron-magnesium-bearing silicates and quite often occupies a position subordinated in relation to aegirine alkaline amphiboles and annite in foyaite lyavochorrite and rischorrite of the Main Ring zone. Aegirine is a ubiquitous primary and or secondary mineral forming marginal zones around diopside-aegirine-augite crystals or separate needle-like crystals obviously formed later than the other clinopyroxenes Yakovenchuk et al. 2005 . Diagrams of a change in clinopyroxene composition Fig. 14 along the A-B-C-D-E-F profile see Fig. 1 shows above all a different degree of rock differentiation in the Main Ring in its rich the Koashva deposit the E point and poor ore Mt. Marchenko Peak the c point parts. As the Main Ring is approached in the area at Mt. Marchenko Peak the clinopyroxenes of foyaite feature increasing contents of Ca Mg and Fe2 at the expense of Na and Fe3 which proceeds on transition to rischorrite attaining the maximum in ijolite-urtite. Quite opposite is the situation in the area of the Koashva deposit where the clinopyroxene of foyaite is represented by aegirine
