Archean felsic volcanic rocks in felsic rocks. Timing of felsic volcanism and tectonic constraints can be identified by radiometric dating and isotopic analysis. In Archean, underwater eruptions of felsic lava were common. Submarine eruption is evident by coarse volcanic breccia formed in situ, hyaloclastite or underwater pyroclastic deposits (clastic rock, composed of tephra only). Since felsic magma is viscous, volcanic eruptions that form dacite or rhyolite are explosive and violent. The Archean felsic eruption may be assigned to Vesuvius eruption type in the present day. Submarine rhyolitic flows were widespread in Archean but it is uncommon in the modern volcanic environment. Viscous felsic eruption
Granite melts which are less dense than mafic rocks and thus tend to ascend toward the surface. In contrast, mafic rocks, either basalts or gabbros, once metamorphosed at eclogite facies, tend to sink into the mantle beneath the Moho. Granitoids have crystallized from felsic magmas that have compositions at or near a eutectic point (or a temperature minimum on a cotectic curve). Magmas are composed of melts and minerals in variable abundances. Traditionally, magmatic minerals are crystallized from the melts that have completely separated from their parental rocks and thus are highly evolved because of igneous differentiation. If a granite has