Experimental Study of Phase Relations in a Lithium Bearing Fluorine Rich Haplogranite and Nepheline Syenite Systemстатья
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Дата последнего поиска статьи во внешних источниках: 31 октября 2014 г.
Аннотация:Phase relations were investigated in the model watersaturated system Si–Al–Na–Li–F–O at
high fluorine contents, a temperature of 800°C, and a pressure of 1 kbar. The obtained aluminosilicate melts are widely variable from quartz to nephelinenormative compositions with agpaitic indexes both higher and lower than one. Various fluoride, aluminofluoride, and oxide phases were observed in the equilibrium assemblage depending on the melt composition: quartz and cryolite associate with the silica richest aluminosilicate melts, topaz and corundum coexist with peraluminous melts, and villiaumite was observed in highly peralka
line melts. Extensive immiscibility between aluminosilicate and aluminofluoride melts was observed in the system. Aluminofluoride melt coexists with quartz and nephelinenormative aluminosilicate melts with agpaitic indexes (Ka) of 0.7–1.4. The composition of aluminosilicate melt in equilibrium with aluminofluoride melt ranges from 33 to 70 wt % SiO2, from 12 to 24 wt % Al2O3, and from 5 to 16 wt % alkalis. The aluminofluoride melt is variable in composition, its Al/Na ratio ranges from 20/80 to 40/60 depending on the composition of the equilibrium aluminosilicate melt.
The experimental aluminosilicate melts equilibrated with cryolite, topaz, and aluminofluoride melt coincide in major component proportions with the bulk compositions of cryolite and topazbearing granites and melt inclusions in minerals.