Geology of Chernogorskoe gem-quality skapolite deposit (Central Pamirs, Tajikistan)

Abstract

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.