5.1. Closed-system fractional crystallization modeling
In order to investigate possible evolution lines for Gedemsa and
Fanta 'Alemagmas, firstlywe attempted at identifying possible primary
magmas. On the basis of their chemical composition, no mafic rocks
from Gedemsa and Fanta 'Ale can represent true primary liquids. Only
two post-caldera basalts from Gedemsa (GDM 125 and GDM 139)
have MgO content between 8 and 9 wt.%, Ni content between 150 and
200 ppm(Table S1), and no evidence for olivine accumulation. Interestingly,
these two rocks, although being the least differentiated, are characterized
by higher content of incompatible trace elements and more
radiogenic Sr isotopic composition (Tables S1, S2; Table 1) with respect
to the other analyzed mafic rocks. The latter feature is quite common to