Dc. Tanner et Jh. Behrmann, STUDY OF STRAIN AND PARTIAL-MELT TRANSFER IN A BANDED MIGMATITE, Journal of structural geology, 19(11), 1997, pp. 1405-1417
An attempt is made to analyse in detail the strain and area change aro
und the tip of a foliation-parallel leucosome. Strain is determined in
the mesosomes above and below the leucosome and the melanosome, in bo
th the XZ (foliation and lineation parallel) and YZ(foliation parallel
, lineation perpendicular) planes, using the following methods: March
analysis of biotite orientation fabric; Fry method of zircon position
fabric; and R-f/phi' method using cordierite grain outlines. In additi
on, March analysis of the orientation of sillimanite inclusions within
the cordierite grains helps confirm the last method. Area change is m
easured by determining the population density of zircon around the leu
cosome in the XZ plane. The amount of material lost can account for th
e area gain in the leucosome and we suggest the sample, at the observe
d scale, was 'closed' in terms of melt movement. The results are used
to construct tentative strain paths for the various components of the
migmatite. Evidence suggests the leucosome was filled by true melt. Fl
uid deformation of the leucosome melt is demonstrated by the orientati
ons of zircons. (C) 1997 Elsevier Science Ltd.