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SUMMARY:Melting above the (nominally) anhydrous solidus controls the locat
 ion of volcanic arcs - Richard Katz\, University of Oxford
DTSTART:20101026T153000Z
DTEND:20101026T163000Z
UID:TALK26315@talks.cam.ac.uk
CONTACT:John Maclennan
DESCRIPTION:Segregation of magma from the mantle in subduction zones is on
 e of the principal mechanisms for chemical differentiation of the Earth. F
 undamental aspects of this system\, in particular the processes by which m
 elt forms and travels to the Earth’s surface\, remain obscure. Systemati
 cs in the location of volcanic arcs\, the surface expression of this melti
 ng\, are widely considered to be a clue to processes taking place at depth
 \, but many mutually incompatible interpretations of this clue exist. We d
 iscriminate between those interpretations by the use of a simple scaling a
 rgument derived from a realistic mathematical model of heat transfer in su
 bduction zones. The locations of the arcs cannot be explained by the relea
 se of fluids in reactions taking place near the top of the slab. Instead\,
  the sharpness of the volcanic fronts\, together with the systematics of t
 heir locations\, requires that arcs must be located above the place where 
 the boundary defined by the anhydrous solidus makes its closest approach t
 o the trench. We show that heat carried by magma rising from this region i
 s sufficient to modify the thermal structure of the wedge and determine th
 e pathway through which both wet and dry melts reach the surface.\n\nRefer
 ence: England & Katz\, Nature\, in press\, http://dx.doi.org/10.1038/natur
 e09417\nand http://dx.doi.org/10.1038/nature09154\n
LOCATION:Tilley Lecture Theatre\, Department of Earth Sciences
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