stripes
This is an asymmetric complex of both extrusive and intrusive rocks which are emplaced in Archaean granites and granite gneisses. The extrusive rocks occupy a depression, up to 950 m deep, in the Archaean basement along the western part of the massif. The volcanic series is subdivided into three parts. The lowest one consists of feldspar leucitites which are overlapped with discordance by peralkaline trachytic lavas and breccias, which constitute the central part of the series. The uppermost part consists of peralkaline trachytic ignimbrites. Leucitite and leucite tephrite dykes cut the ignimbrites. In the eastern part of the complex peralkaline syenites are dominant. There is a body of larvikites situated parallel to the margin of the complex, which is characterised by strongly orientated tablets of alkali feldspar. The larvikite is porphyritic the main minerals being K-feldspar (50-71%) and clinopyroxene (10-25%); accessory minerals are amphibole, biotite, titanite, quartz, apatite, magnetite, zircon, rutile, baddeleyite and sulphides. These alkaline rocks are cut by small bodies of micromonzonite consisting of K- feldspar, plagioclase, pyroxene and amphibole. As well as larvikite there is an intrusion of pulaskite, which is a highly leucocratic peralkaline syenite. The centre of the complex is formed of weakly alkaline, two feldspar syenites which form an irregularly-shaped stock. The composition of the syenites varies from the centre, where the rocks are leucocratic amphibole syenites, to the margin which consists of mesocratic amphibole- pyroxene syenite and biotite-pyroxene monzonite. The pyroxene in these rocks is principally salite. The youngest rocks of the massif are tinguaite, epileucitite, lamprophyres and melanite- bearing peralkaline syenites, and these form small dykes and irregular bodies within the extrusive rocks. According to K-Ar age determinations, syenite porphyries are of the same age. Sodium-rich metasomatic rocks that contain much albite and aegirine form linear bodies among the nepheline syenites and their pegmatites contain agpaitic accessory minerals including loparite, innelite, lomonosovite, Ca-rinkolite and labuntsovite.
KRAVCHENKO, S.M., KAPUSTIN, Yu.L., KATAEVA, Z.T. and BYKOVA, A.V. 1982. Agpaitic mineralization of the Mesozoic metasomatic rocks of potassic alkaline complexes of the Central Aldan. Doklady Akademii Nauk SSSR, 263: 435-9.
ORLOVA, M.P. 1990. Mesozoic stage of magmatism. In G.V. Polyakov and V.V. Kepezinskas (eds) Potassic alkaline magmatism of the Baikal-Stanovoy rift system. 65-123. Nauka, Siberian Division of the USSR Academy of Sciences, Novosibirsk.
PERVOV, V.A., KANUKOV, B.U. and ARAKELYANZ, M.M. 1991. New data on K-Ar age of the extrusive rocks of the Tommot volcanic-plutonic complex (Central Aldan). Doklady Akademii Nauk SSSR, 321: 349-52.
