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SUMMARY:Calculated phase equilibria in high pressure metamorphic rocks and
  the deep mantle - Tim Holland (Department of Earth Sciences)
DTSTART:20101115T160000Z
DTEND:20101115T170000Z
UID:TALK26582@talks.cam.ac.uk
CONTACT:Ian Farnan
DESCRIPTION:It is now possible to calculate quite complex phase diagrams f
 or natural rocks of basic\, ultrabasic\, pelitic and carbonate bulk compos
 itions with the possibility of inferring the P −T − t history within o
 rogeny. In other ways we still have far to go. The improvement in internal
 ly- consistent thermodynamic datasets for the end-members of minerals in r
 eal solid solutions has advanced our knowledge and ability to understand m
 etamorphic rocks. Improvements in activity-composition relations have brou
 ght much needed realism to such calculations\, but these models are still 
 in their infancy. It is increasingly clear that mineral solid solutions ne
 ed to be modelled in larger chemical systems to yield reliable information
 \, and so the mixing properties will require significant work in future. 
 In addition\, the thermodynamic models are being extended to include a num
 ber of deep mantle phases and should be well-suited to predicting pseudose
 ctions for realistic bulk compositions at deep mantle conditions. \n\nRefe
 rences \nGreen\, E.\, Powell\, R. & Holland\, T. 2007. An order-disorder m
 odel for omphacitic pyroxenes in the system jadeite–diopside-hedenbergit
 e–acmite\, with applications to eclogitic \nrocks. American Mineralogist
 \, 92\, 1181–1189. \n\nHarte\, B (2010) Diamond formation in the deep ma
 ntle: the record of mineral inclusions  and their distribution in relation
  to mantle dehydration zones. Mineralogical Magazine\,  74\, 189–215. \n
 \nHolland\, T.J.B. & Powell\, R. 2010. An improved and extended internally
 -consistent thermodynamic dataset for phases of petrological interest\, in
 volving a new equation of state \nfor solids. Journal of Metamorphic Geolo
 gy\, in press. 
LOCATION:Harker 2 lecture room\, Department of Earth Sciences\, Downing Si
 te
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