## 4 Results and Discussion
### Temperature Sensitivity  
The temperature dependence of the two immiscible liquid phases for an L\({}_{\text{Fe}}\)-dispersed and L\({}_{\text{Si}}\)-dispersed amoeboid composition was computed. Such predictions bound the temperature ranges over which the amoeboid morphologies might be stable under thermodynamic equilibrium conditions. Prediction of the liquid phase fractions was performed  
Figure 2: Compositional and temperature sensitivity to (**a**) Al\({}_{2}\)O\({}_{3}\) and (**b**) Al\({}_{2}\)O\({}_{3}\) with CaO and MgO. The labels indicate the weight percent composition for each of the oxide species. The dashed areas (**b**) indicate the bulk composition ranges of the LSi-dispersed (labeled LSi) and LFe-dispersed (labeled Lfe) measured by SEM and TEM-EDS. for the amoeboid compositions obtained by TEM (Table 1), only. The computed results for L\({}_{\text{Fe}}\)-dispersed compositions (Figure 3) predict that the Fe-rich phase is predominant (Figure 3a), contrary to analytical measurements, which show the matrix phase to be Si-rich and the dispersed phase to be Fe-rich. Average compositions lie on the FeO-rich domain of the miscibility gap (Figure 2b), as discussed in the previous section. The two-phase liquid domain is stable between 1400-1600 \({}^{\circ}\)C, above which the two liquids are completely miscible. Upon cooling, the amount of Fe-rich liquid is reduced but remains dominant, and the Si-rich liquid increases in phase fraction. The composition of each liquid as a function of temperature is plotted in Figures 3b,c for the FeO- and SiO\({}_{2}\)-rich liquids, respectively. The dashed lines are the analytically measured compositions of each liquid phase based on TEM. Figure 3b reveals that the predicted iron content in the Fe-rich liquid is significantly underestimated and the SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) content is overestimated compared to chemical analysis (dashed lines). MgO and CaO contents are in relative agreement with compositions measured by TEM for the FeO-rich liquid. The computed results indicate the Fe-rich liquid becomes increasingly enriched in FeO and depleted in SiO\({}_{2}\) as a function of decreasing temperature. Broadly, better agreement between compositions obtained by TEM and our computed results is observed at reduced temperatures, such as 1400 \({}^{\circ}\)C. The Si-rich liquid is calculated to be the minority phase (Figure 3a) and the predicted values for each component are in relative agreement with the analytically measured compositions, except for CaO, which is underestimated (Figure 3c). The Si-rich liquid becomes slightly enriched in SiO\({}_{2}\) as a function of decreasing temperature. From these predictions, we can propose a constraint in temperature for the formation of these amoeboids. The dispersed phase (FeO-rich) forms at 1400 \({}^{\circ}\)C, as the computed composition approaches the analytically measured composition with decreasing temperature. However, the SiO\({}_{2}\)-rich phase is in better agreement with compositions achieved by chemical analysis (TEM) at temperatures \(\sim\)1600 \({}^{\circ}\)C, as seen in Figure 3c. The relative amounts of computed phase fraction, i.e., that the Fe-rich liquid is the majority phase, is in contrast with the observed morphologies, which would expect the dispersed phase (Fe-rich liquid) to be present in smaller amounts compared to the matrix phase. This deviation could point to non-equilibrium formation conditions for the amoeboid morphologies in the fallout glass. CALPHAD predictions indicate that the dispersed phase (L\({}_{\text{Fe}}\)) forms at lower temperatures than the Si-rich matrix phase. This would mean that the dispersed phase might nucleate within the matrix phase as the fireball condenses. The computed results for L\({}_{\text{Si}}\)-dispersed compositions (Figure 4) show that the compositions of these amoeboids are predicted to lie outside of the stability limit of the FeO-SiO\({}_{2}\) miscibility gap (see Figure 2b).