Crustal assimilation of felsic magmas
As already noticed, some rhyolites (both pantellerites and
comendites) from Gedemsa and Fanta 'Ale are similar to basalts to trachytes least enriched in radiogenic Sr, having 87Sr/86Sr ~ 0.704;
other aremore enriched in radiogenic Sr, having 87Sr/86Sr N 0.705 (feldspar
separates in Table 1; Fig. 8). The two groups of rhyolites differ also
in terms of 143Nd/144Nd, variable from 0.51285 to 0.51279, and from
0.51277 to 0.51270, respectively. The Pb isotopes of three rhyolites are
fairly similar (e.g., 206Pb/204Pb is 18.3–18.5), so that two of them define
a distinct trend together with additional rhyolites fromliterature in the
Sr–Pb isotope space (trend B in Fig. 9).