Тип публикации: доклад, тезисы доклада, статья из сборника материалов конференций
Конференция: Петрология магматических и метаморфических комплексов; Томск; Томск
Год издания: 2017
Аннотация: Lamproites is a specific group of rocks, that are characterized by high-magnesium high-potassic composition and are generally enriched in volatiles and incompatible elements. Low-titanium lamproites occur in Mediterranean, Northern Vietnam and Eastern Siberia (Aldan Shield). We studied a Mezosoic occurrence of lamproites of Aldan SПоказать полностьюhield, a dyke complex, which is situated within Ryabinoviy massif. In this location subvolcanic bodies of different composition from olivine lamproites to syenite-porphyry outcrop on a small area. The previous studies (Rokosova, Panina, 2013; Chayka, Vasyukova, 2017) showed that these rocks are geochemicaly identical to the previous magmatic stage of the massif, which led to Au-ore formation, and revealed complicated silicate-carbonate-salt immiscibility processes during magma evolution. During the research we studied structural relationships of the intrusive bodies, petrography and mineral composition of the rocks, chemistry of rocks and rock-forming minerals (olivine, Cr-spinel, phlogopite, clinopyroxene). Because of previously found immiscibility processes, a special attention was paid to non-silicate assemblages such as carbonate, silicate-carbonate, fluorite-carbonate globules andREE-apatite-fluorite gangue found in several dykes. The results show that evolution of low-Ti lamproite magma can produce a wide range of rocks from olivine lamproites to syenites. Rock chemistry and chemistry of rock-forming minerals of the studied series reveal a close similarity of these rocks with low-Ti Mediterranean lamproites and lamproites (cocites) from Fan Si Pan uplift (Northern Vietnam) and, controversially, distinguish them with “typical" high-Ti olivine lamproites (Smoky Butte, Gaussberg, Aillik) (Prelevic et al., 2013; Hoa et al., 1997; Foley, Jenner, 2004; Mitchell et al., 1987; Tappe et al., 2007). In agreement with results of previous studies of other Mesozoic Aldan lamproites (Davies et al., 2006), geochemical and mineralogical data reveal a lithospheric heterogeneous mantle source for these rocks, which probably consisted of at least two assemblages: strongly-depleted SCLM peridotite and domains, metasomatically enriched during ancient subduction processes. Detailed studies of non-silicate assemblages (see more in Chayka, Izokh, 2017) allowed to conclude that they were formed due to immiscibility processes, previously described in inclusions in clinopyroxene (Rokosova, Panina, 2013). Some evolution features of the carbonatite component, which was separated at the stage of crystallization of phlogopite and diopside, and then divided into carbonate and salt immiscible fractions, were described. During these processes REE, U and Th migrated into fluoride-salt fraction and then formed a multi-stage hydrothermal mineralization in apatite-fluorite gangue assemblage with REE minerals (burbankite, bastnasite), which are typomorphic for carbonatite-derived fluids (Buhn et al., 1999; Belovitskaya, Pekov, 2004; Williams-Jones, Wood, 1992).
Журнал: Петрология магматических и метаморфических комплексов
Выпуск журнала: Выпуск 9
Номера страниц: 441-447
Издатель: Томский центр научно-технической информации