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SUMMARY:Magma intrusive rates and the growth of melt reservoirs and magma 
 chambers - Catherine Annen\, University of Bristol
DTSTART:20131105T163000Z
DTEND:20131105T173000Z
UID:TALK47283@talks.cam.ac.uk
CONTACT:John Maclennan
DESCRIPTION:The concept that granitoids plutons in the upper crust are sol
 idified large magma chambers has been challenged by high precision geochro
 nological data. A strong dichotomy is found between the rate of magma tran
 sfer through the crust and the average long-term pluton emplacement rate i
 nferred from geochronology.  In addition\, field studies show that many pl
 utons are formed by the addition of discrete intrusive sheets. These obser
 vations strongly support a model where igneous bodies grow incrementally d
 uring pulses of magma injection that are separated by long periods of quie
 scence. Numerical simulation shows that at low emplacement rate\, successi
 ve pulses solidify during repose period and the size of any magma chamber 
 is limited to the size of one pulse. A consequence is that large magma cha
 mbers in the upper crust must be rare and short-lived and most differentia
 tion from a mafic parent is likely to happen in the lower crust where high
 er ambient temperatures and higher magma fluxes are more favorable to the 
 formation of long-lived melt reservoirs. Integration of petrological exper
 iments and numerical simulation show that a diversity of melt compositions
  can be produced in deep crustal hot zones. Episodic ascent of melt from d
 epth can be explained by the dynamics of melt segregation and extraction.\
 n\n\nRef:\n\nAnnen\, C. (2009)\, From plutons to magma chambers: Thermal c
 onstraints on the accumulation of eruptible silicic magma in the upper cru
 st\, Earth and Planetary Science Letters\, 284(3-4)\, 409-416.\n\nMelekhov
 a\, E.\, C. Annen\, and J. Blundy (2013)\, Compositional gaps in igneous r
 ock suites controlled by magma system heat and water content\, Nature Geos
 cience\, 6(5)\, 385-390.\n\nGlazner\, A. F.\, J. M. Bartley\, D. S. Colema
 n\, W. Gray\, and Z. T. Taylor (2004)\, Are plutons assembled over million
 s of years by amalgamation from small magma chambers?\, GSA Today\, 14(4/5
 )\, 4-11.\n\n*Annen\, C.\, J. D. Blundy\, and R. S. J. Sparks (2006)\, The
  genesis of intermediate and silicic magmas in deep crustal hot zones\, J.
  Petrol.\, 47(3)\, 505-539
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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