I would like to know the presence of intracrystalline deformation in migmatits. Does it tell about the deformation history of the rock during partial melting or does it have any implication during partial melting of a migmatite?
Dear Sandile,
First, intracrystalline deformation would be applicable on the constituent minerals of the rock and not on the whole rock itself. These deformation features are essentially solid state deformation feature, so if you see these on minerals then either 1) these minerals will belong to refractory part (which were deformed earlier) of the migmatite which escaped partial melting or, 2) the migmatite itself was deformed after migmatization. Therefore you should see the deformation features across different minerals lying in neighborhood, then only you become confirmed about the intracrystalline deformation and its implications. You may also see the variation in intracrystalline features when you approach from a zone of less partial melting to a zone of high partial melting ( such as SGR recrystallization to high T GBM recrystallization)
For detailed treatment regarding this issue you should consult books by Vernon, Blenkinshop or Passchier and Trouw (2005). Hope this helps.
Dear friend ,please I can advise you to read :First, chapter 11 in book of Migmatites by Mehnert and Chapter 6 in book of metamorphic textures by Alan Spary,1986
Dear Mr. Xaba,
the terminology used is not well elected or may even be considered as a misnomer.
In a setting like that described, you may differentiate between three process-related temporal relations. The mineralization or newly formed leucosome may be pre-kinematic (1), syn-kinematic (2) or post-kinematic (3) relative to the structural disturbances affecting the migmatite. In case (1) the minerals are deformed and the felsic part of this rock displays e.g. deformation of the minerals which is of course intracrystalline. The rock section may be described as metapegmatite/ metagranite, depending on the size and relative grain-size distribution. In case (2) it will lead to a pegmatoid or granitoid and in case (3) to a pegmatitic or granitic self-intrusive melt unaffected by any deformation.
Figures which describe these various cases are shown in :
DILL, H.G. (2015) The Hagendorf-Pleystein Province: The center of pegmatites in an ensialic orogen.- Modern Approaches in Solid Earth Sciences,
Springer, Dortrecht, Heidelberg, London, New York, ISBN-978-3-319-18805-8, 475 pp.
DILL, H.G. (2015) Pegmatites and aplites: Their genetic and applied ore geology.- Ore Geology Reviews 69: 417-561.
The above classification scheme is presented in a chart in:
DILL, H.G. (2015) Pegmatites and aplites: A source of energy resources, ore and industrial Minerals.- 1. Meggener Rohstofftage "Minerals for the World", 17. - 19. September, Lennestadt-Meggen, BDG Berufsverband Deutscher Geowissenschaftler and Tracto-Technik GmbH & Co. KG and Sachtleben Bergbau Verwaltungs-GmbH, Germany.
Best regards
H.G.Dill