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SUMMARY:Changing the paradigm - new views of magmatic systems provide new 
 perspectives on volcanic processes - Professor Katharine Cashman (Universi
 ty of Bristol)
DTSTART:20160125T170000Z
DTEND:20160125T180000Z
UID:TALK62372@talks.cam.ac.uk
CONTACT:Matouš Ptáček
DESCRIPTION:Igneous petrology is undergoing a major paradigm shift. For th
 e past century\, the paradigm of the magma chamber - a single\, melt-domin
 ated magma body - has informed models of magma evolution and underpinned s
 tudies of volcanic processes. Over the past decade\, however\, the communi
 ty has converted to a model of complex magma storage regions composed prim
 arily of crystal-rich "mush"\, with crystal-poor melt partitioned into sil
 l-like lenses that can be tapped\, either sequentially or simultaneously\,
  to feed volcanic eruptions. Why has this conceptual shift occurred? Evide
 nce for complex magma storage regions derives from numerous sources\, incl
 uding (1) geophysical evidence for sill-like melt bodies\, (2) petrologic 
 studies\, which provide strong evidence that many erupted magma contain cr
 ystals that have been incorporated from different parts of the magma stora
 ge region\, and over different time scales\, and (3) geochemical evidence 
 that magmatic gases may accumulate and be released independently from the 
 melt. These observations suggest that magma storage regions are not only c
 omplex\, but also dynamic\, in that the solid (crystal)\, liquid (melt) an
 d gas (exsolved volatiles) components may move and interact at different r
 ates. Critically\, adopting a melt-mush model requires a re-evaluation of 
 processes responsible for melt segregation\, evolution and eruption. For e
 xample\, melt segregation and evolution may depend more on processes relat
 ed to reactive flow of melts and fluids through porous crystal networks th
 an sinking or floating of crystals within a (dominantly liquid) body. Addi
 tionally\, patterns of eruptive behaviour may be determined as much by the
  stability of\, and interactions between\, individual melt lenses as by th
 e evolution of a single melt body. From this perspective\, studies of volc
 anic processes can be linked directly to processes of magma generation and
  evolution. Forging these links provides an exciting challenge for the fut
 ure.
LOCATION:Harker Room 1\, Department of Earth Sciences
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