Место издания:Bulgarian geological society Sofia, Bulgaria
Первая страница:63
Последняя страница:64
Аннотация:The melting of aluminosilicate materials (in the system: trachyrhyolite – water ± salt (NaF, Na2CO3)) was produced for the purpose to study the processes of liquid immiscibility under magmatic conditions. The powder of trachyrhyolite (composition, wt.%: Na2O – 2.97(19); MgO – 0.15(6); Al2O3 – 11.51(12); SiO2 – 72.78(13); K2O – 5.53(11); CaO – 1.05(7); TiO2 -0.13(6); FeO – 0.80(29); SrO – 0.60 (19).) was used as starting material. Weighed portions of trachyrhyolite powder were loaded into Pt-capsules with addition of calculate amounts of water and salt. The oxides SrO, Nb2O5 and La2O3 were loaded into the capsules as tracer materials (not more then 2.5 wt% of all trachyrhyolite powder weight). The balance sample / fluid was ~7. We have used the gas-bomb device for our run conducting. Run conditions were following: (1) (T=1200°С; Р=5kbar; time of exposure: 2 hours) → (2) (T=1000°С; Р=1 kbar; time of exposure: 1 day) → isobaric quenching. The melting, homogenization and fluid saturation of aluminosilicate melts were produced at T=1200°С and Р=5 kbar. The melt heterogenization and liquid immiscibility appearance take place with parameters decreasing (to T=1000°С; Р=1 kbar). It was shown, that liquid immiscibility in the system trachyrhyolite – water is exist as drops generation in basic melt volume. The drops composition is similar to melt’s composition and distinguish from melt by the another contents of water, TiO2 and another proportions of alkaline- and alkaline-earth elements.
So, the liquid immiscibility characteristic of the salts of P-Q type (L ↔ L1 + L2) has realized. Here the trachyrhyolite melt is acting as salt of P-Q type. In presence of salt (NaF) the melt heterogenization has realized by scheme: silicate melt – salt melt. When sodium carbonate add the phenomenon of liquid immiscibility did not observed. In this case the increase of agpaitic coefficient ((Na+K)/Al) of glass from 0.94 (for starting trachyrhyolite) to ≈1.3 had observed.
This study was supported by RFBR, project № 15-05-03393.
