Magma & Volatiles

Magma is the molten silicate material produced during volcanic activity that cools to create igneous rocks like granite and basalt. During volcanic eruptions, magma can reach the surface as violently ejected rock and ash, or in a slow, steady flow as lava.

Volatiles are chemicals that exist in magma in their gaseous state. Water vapor and carbon dioxide are the most common and important ones, and there are a number of questions we have about volatiles like them.

• The subducting slab brings volatiles along with it as it is fed into the mantle. The volatiles can be contained in seafloor sediment that has accumulated on the downgoing oceanic crust or in the oceanic crust itself. We believe that in the IBM volcanic arc system, the crust itself is the more important source because much of what has accumulated on it is simply volcanic rock that has already been recycled before. It carries with it water and other volatiles encased in porous rock or bound up in minerals which are able to withstand the heat of the mantle.
• The mantle wedge is that portion of the mantle caught between the subducting crust (in this case, the Pacific plate) and the crust it passes under (the Philippine plate). It is the source of the magma that makes its way to the surface, but first it must pass through the crust of the overriding plate.
• The arc crust is the portion of the overriding plate directly interacting with the subducting plate and the mantle. It can contribute some of the volatiles researchers find at the surface as its material mixes with magmas ascending from the mantle.

But which source contributes what volatiles and how much of them? One of our objectives in IBM is to find that out. We also want to know how those volatiles affect the workings of the Subduction Factory. Water influences the melting point of magma. It acts as a lubricant between tectonic plates that helps control the rate of seismic velocity.