## 4 Results and Discussion
### Compositional Sensitivity  
The compositional sensitivity of liquid phase iron-silicate systems with respect to Al\({}_{2}\)O\({}_{3}\)-content has been presented previously [18]. Since Al\({}_{2}\)O\({}_{3}\) is known to suppress liquid immiscibility of silicate systems [40], it may be one parameter that explains the presence or absence of immiscibility textures in these fallouts. The Al\({}_{2}\)O\({}_{3}\) content in Table 1 is lower than other compositions reported in non-metallic fallout, where fewer immiscible textures were described by [PERSON] et al. [6; 7]. The combined effects of the amoeboids with compositional variations in alumina (Al\({}_{2}\)O\({}_{3}\)), calcia (CaO), and magnesia (MgO) concentrations on liquid thermodynamics, specifically miscibility gap formation and stability, is explored here. The effect of 5 wt% and 10 wt% Al\({}_{2}\)O\({}_{3}\) additions to the liquid immiscible region of a pseudo-binary FeO-SiO\({}_{2}\) system (Figure 2a) is explored using equilibrium calculations. The calculations presented here are a rough estimation of the experimental data with ranges that bound the amoeboid compositions with respect to Al\({}_{2}\)O\({}_{3}\) content. There exists a wide range of stability of the two-phase liquid domain across compositions between 5-67 wt% FeO (black curve). The maximum temperature limit (T\({}_{\rm max}\) or critical temperature of immiscibility) of the two-phase liquid region is calculated to be 1950 \({}^{\circ}\)C at a composition of 24 wt% FeO, above which the liquids are completely miscible. The miscibility gap extends across a temperature range of from 1620-1950 \({}^{\circ}\)C. Upon cooling from T\({}_{\rm max}\) and 24 wt% FeO composition, the phase boundaries expand and shift so that the majority liquid becomes enriched in SiO\({}_{2}\), and the minority liquid is iron-rich in accordance with the lever rule [42]. The addition of Al\({}_{2}\)O\({}_{3}\) alters the stability of the two-phase liquid domain (blue and brown curves), decreasing the maximum temperature of the two-liquid region by 95 and 208 \({}^{\circ}\)C for 5 and 10 wt% Al\({}_{2}\)O\({}_{3}\), respectively, but extending the stability range down to lower temperatures (\(\sim\)1420 \({}^{\circ}\)C) as seen in [43]. Incidentally, the presence of Al\({}_{2}\)O\({}_{3}\) leads to a contraction of the liquid immiscibility range with respect to composition. The composition range of FeO, where two liquids are stable, is significantly reduced at the lower temperature limits. This is especially pronounced for higher Al\({}_{2}\)O\({}_{3}\)-content, such that the two liquids coexist between 14-60 wt% FeO at 1420 \({}^{\circ}\)C for 10 wt% Al\({}_{2}\)O\({}_{3}\) (Figure 2a). The composition at T\({}_{\rm max}\) is shifted towards enrichment in FeO (depletion in SiO\({}_{2}\)), to 27 wt% FeO and 30 wt% FeO for 5 at 10 wt% Al\({}_{2}\)O\({}_{3}\), respectively. To be more representative of fallout sample compositions, the effects of select other minor elements known to be entrained in the fireball from near-ground explosions were added to the calculation. The combined effects Al\({}_{2}\)O\({}_{3}\) with CaO and MgO additions are compared to the FeO-SiO\({}_{2}\) pseudo-binary and FeO-SiO\({}_{2}\)-5 Al\({}_{2}\)O\({}_{3}\) (Figure 2b). In the presence of CaO and 5 wt% Al\({}_{2}\)O\({}_{3}\), the minor CaO additions (orange-curves) further reduce T\({}_{\rm max}\), 1838 \({}^{\circ}\)C to and 1818 \({}^{\circ}\)C for 1 wt% and 2 wt% additions, respectively, which is 17 \({}^{\circ}\)C and 37 \({}^{\circ}\)C lower compared to the T\({}_{\rm max}\) of FeO-SiO\({}_{2}\)-5 Al\({}_{2}\)O\({}_{3}\) (blue curve). However, the FeO wt% composition at T\({}_{\rm max}\) is not significantly affected. The purple curve in Figure 2b corresponds to the liquid phase stability of FeO-SiO\({}_{2}\) with additions of 5 wt% Al\({}_{2}\)O\({}_{3}\), 2 wt% CaO and 1 wt% MgO. In this case the addition of MgO further reduces T\({}_{\rm max}\).