Silicate globules in kyanite from grospydites of the Zagadochnaya kimberlite pipe,Yakutia: The problem of the origin |
| |
| Authors: | Tomilenko A A Kovyazin S V Pokhilenko L N Sobolev N V |
| |
| Institution: | 1.Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
; |
| |
| Abstract: | The results of complex study of silicate globules and α-quartz paramorphs after coesite in kyanite from grospydites from the
Zagadochnaya kimberlite pipe, Yakutia, using optical and scanning electron spectroscopy, electron and ion microprobes, LA
ICP MS and Raman spectroscopy, are presented. The existence of radial fractures diverging from silicate globules into the
matrix (kyanite) attests to the fact that the content of the globules is extremely condensed. A zonal structure is usually
typical for globules: a coat and a core, which can be explicitly distinguished under the electron microscope, can be differentiated
in them. Compositionally, the coat of the globule corresponds to potassium feldspar (wt %: 66.4 SiO2; 16.9 Al2O3; 0.4 FeO; 0.1 CaO; 0.2 Na2O; 14.7 K2O). The globules were also detected in which along with K, a high content of Na and Ca was also ascertained in the silicate
coat. The globule coat is considerably enriched with Ba, La, Ce, Nb, and a number of other noncompatible elements as compared
with xenolith minerals. The water content in globules is ∼0.6 wt %. As compared with the host mineral (kyanite), the core
part of the globules is also enriched with Co, Ni, Zn, and Cu; their content in kyanite is negligibly low. The entire data
collection attests to the fact that the formation of silicate globules could have been caused by interaction of the conservated
fluid and/or water-silicate melt with the host mineral and crystalline inclusions of clinopyroxene and garnet with decreasing
pressure during the transportation of grospydite xenoliths by the kimberlite melt to the Earth’s surface. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
