Figure 5. Immobile-element plots of main rock units at Aljustrel. Note that 5 different felsic units can be distinguished using these plots, including samples with a wide range of alteration. The variable effects of mass loss and mass gain produce the linear data trends for each rhyolite type. Although rhyolites A and C overlap in the upper plot, they are well separated in the lower (and other) plots. The QFXT unit is a quartz-feldspar porphyry which has the silica content of rhyolite, but TiO2 and FeO contents in the range of dacite.