sgr ms thesis - University of Maine

Chapter 3
PHYSICAL DESCRIPTION OF SUBVOLCANIC SYSTEMS
A rarely described and intricately formed feature of volcanism, subvolcanic
systems can yield a great deal of information about the link between deeper
magma plumbing systems and upper crustal volcanic regions. Exposures of
these systems are uncommon because they occur at a depth between magma
reservoir and volcanic edifice, providing only a small window into the processes
that occur between the two. Subvolcanic systems can hold a wealth of
information on the evolution of calderas, volcanic root zones, and the upper
sections of reservoirs because they can contain intrusive phases such as cone
sheets, ring faults and dikes, and massive central intrusions produced during
active volcanism. The evolution of the subvolcanic magmatic system is recorded
by these features due in part to the rapid quenching of some units and the
inherent sequential series of intrusive behavior (Lipman, 1984; Johnson, 1999).
Below I review the mechanisms behind magma generation, segregation,
transport, emplacement, and volcanic eruption. Deformation features recorded in
the subvolcanic system are also reviewed, and I discuss how volcanic energy is
translated into deformation features, and how they relate to modern examples
and the Shatter Zone.
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