Once these mafic minerals have been removed, the melt no longer has a basaltic composition.
More than 200 layers of volcanic ash of predominantly basaltic composition have been found within the Mo-clay of the Fur Formation.
Magma generated by small amounts of partial melting of the mantle is generally of basaltic composition.
Basic magmas, however, which are predominantly of basaltic composition, have a much lower silica content and are erupted at high temperatures.
In fluid magmas, such as those of basaltic composition, these gas bubbles can expand freely.
Analyses of the rocks at the Venera 13 and 14 sites are consistent with a basaltic composition.
It is likely that the rocks of basaltic composition have a volcanic origin, and could have flowed as basaltic lavas from any Beta Regio volcanoes.
Unreasonably high degrees of partial melting are required to attain basaltic compositions.
For example, lava tubes on Earth only form in lavas of basaltic composition.
Pumice of basaltic composition, however, is rather rare, although there are some rather peculiar varieties in the Hawaiian Islands.
