TYPOMORPHISM OF MINERALS OF VEIN VEZDARINSKAYA (SOUTHWESTERN PAMIR) AS AN INDICATOR OF PHYSICO-CHEMICAL PROCESSES OF PEGMATITE FORMATION

Abstract

The relevance of the work is caused by the need to clarify the conditions for formation of a unique pegmatite object – the Vezdarinskaya miarolitic pegmatite vein. This object gave the world a large number of rare mineral species, which indicates special physico-chemical parameters of the mineral formation medium. The main aim of the research is to characterize the formation of structural-material complexes of the pegmatite vein by typomorphic features of feldspar, tourmalines, garnets, micas. Objects: rock-forming and secondary mineral species of the pegmatite vein Vezdarinskya. Methods. Quantitative analysis of the chemical composition of minerals was performed using X-ray spectral microanalysis on the JXA-8100 microprobe and on scanning electron microscopes Tescan Mira 3 LMU and VEGA II LMU, combined with INCA Energy350 Oxford spectrometers, the structural state of feldspars was calculated based on the results of X-ray analysis on the XPert PRO (PANalytical) diffractometer. Results. The authors have obtained the complex data on the mineral composition of the pegmatite vein Vezdarinskaya (4 mineral species of mica, 4 species of tourmalines, 2 species of plagioclases were identified and refined), generations of mineral species were identified, new minerals for this pegmatite (andalusite, bertierine) were recorded, the association with which is typomorphic. A scenario for formation of a nearmiarolic vein aggregate is proposed and the role of remobilization of host rocks in the formation of pegmatite (its mineral associations) is analyzed. According to the association of mineral phases, the formation temperatures of the structural-material complexes of the vein were determined. The tipochemism of secondary minerals records the presence of a heterogeneous pegmatite-forming medium, which has undergone separation into silicate and silicate-fluid parts. The geochemistry of pegmatite and its mineral set are caused by a change in the chemistry of the pegmatite melt under the influence of the rocks of the Shugnan formation of the Shahdarinskaya series that contains it.

Keywords

• myarolic pegmatites
• vezdarinskaya vein
• mineral associations
• generation
• pegmatite formation
• southwestern pamir