How do mantle-derived magmas that have a basaltic composition generate magmas that exhibit an intermediate to felsic composition? How do mantle-derived magmas that have a basaltic composition generate magmas that exhibit an intermediate to felsic composition? As basaltic magma ascends through the thick continental crust, ferromagnesian minerals crystallize and drop out of the melt, thus creating a secondary melt of an intermediate or a felsic composition. As basaltic magma ascends through the thick continental crust, non-ferromagnesian minerals crystallize and drop out of the melt, thus creating a secondary melt of an intermediate or a felsic composition. As basaltic magma ascends through the thick continental crust, ferromagnesian minerals crystallize and drop out of the melt, thus creating a primary melt of an intermediate or a felsic composition. Partial melting of peridotite directly generates magma of an intermediate or a felsic composition. As basaltic magma ascends through the thick continental crust, non-ferromagnesian minerals crystallize and drop out of the melt, thus creating a secondary melt of an intermediate or a felsic composition.