The Montenegrin jewel scapolite deposit, which relates to a new genetic type, is characterized. It is located in the Central Pamirs (Tajikistan) and is localized in the sarydzhilginsk formation of the muzkol series (PR1). The enclosing rocks are metamorphosed basite-ultrabasic formations of the kukurt complex, among which harzburgites were first discovered.
Jewel scapolite mineralization contains albitite lenses. They were formed by the metasomatic replacement of nepheline syenites. The reaction occurred with a negative volume effect with a decrease in the volume of solid phases 14%, which caused the appearance of voids. Albitite bodies form a lenticular nesting structure. They have cross-cutting contacts. They are accommodated by amphibolites, which metasomatically replace melanocratic gabbroids and partially altered harzburgites. Jewelry scapolite is localized in 28 albitite lenses, the walls of the voids of which are inlaid with columnar purple scapolite. The sequence of processes at the field corresponds to the following scheme: formation of melanocratic gabbroids with small bodies of nepheline syenites metasomatic development in the first amphibolites, and in the second albitites with voids growth on the walls of the hollows of the hollow scapolite crystallization in the voids of the jewelry scapolite.
Introduction. The 60 m wide quartz dolerite stock, opened by a quarry, is heavily alternated by secondary processes, which makes it difficult to study.Aim. Reconstruction of primary magmatic structures and determination of conditions conductive to their crystallization and late alterations.Materials and methods. In order to assess the conditions of magmatic crystallization and massive late alterations, thin sections of selected samples were studied and chemical analysis of rocks was performed.Results. The stock was established to have a primary double structure with a wide centre and a narrow annular border (1 m). This is due to the contraction and reintroduction of a melt along the edge of the stock. The melt inside the ring is adiabatically heated to 1175° and the water pressure drops to 0.5 kbar, as compared to the centre (900° and 2 kbar). Therefore, the centre and edge have a different primary composition with plagioclase (An50), qartz, magnetite and glass (5%) in the centre and early plagioclase, quartz, pyroxene, plagioclase microlites, miarolitic cavities and glass (30–40%) at the border. Final hardening and new contraction lead to the formation of radial cracks in the ring. The mechanical work, spent on their formation, sharply reduces the level of internal energy, while the expansion of cracks leads both to adiabatic cooling of the solution in the border zone of the stock and massive low-temperature metasomatosis (260–132°C). The reactions proceed diffusionally when the solution is stagnant with the massive formation of pseudomorphoses. Due to a decrease in the volume of reacting solid phases and an increase in the total porosity under the conditions of dominant decompression, part of the silica is removed upwards. The centre is cooled slowly with the preservation of relics and their successive alteration from acid to alkaline ones. Initial acid reactions are provided by the complete dissociation of a weak carbonic acid, followed by strong acid and final alkaline reactions provided by chlorine and incomplete dissociation of carbonic acid, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.