Rupture and inflation of a basic magma chamber by silicic liquid

Abstract

The prevailing view among volcanic geologists is that the introduction of basic magma into a silicic magma chamber may trigger explosive silicic volcanism¹ and lead to the eruption of mixed magmas². Although the patterns of basic and silicic eruptions in some areas may support an input of basic magma¹ just before silicic eruption, evidence from the study of the erupted rocks is generally equivocal; many occurrences are as readily explained by injection of silicic into basic magma. Although this latter sequence is a more efficient way to produce contemporaneous magma mixing and explosive silicic volcanism, it appears to have been largely overlooked. This report describes evidence in the Newark Island layered intrusion for the rapid emplacement of large volumes of silicic magma into a basic magma chamber and suggests that such events, in the uppermost crust, may also be important in triggering explosive silicic volcanism and commingling of magmas just before eruption.