﻿122 
  M. 
  E. 
  Wilson 
  — 
  Laurentian 
  Highlands 
  of 
  Canada. 
  

  

  ville 
  series, 
  it 
  is 
  inferred 
  that 
  the 
  banded 
  gneisses 
  originally 
  

   constituted 
  the 
  magmatic 
  centre 
  of 
  a 
  Pre-Cambrian 
  mountain 
  

   chain. 
  

  

  (4) 
  As 
  regards 
  the 
  origin 
  of 
  the 
  folded, 
  banded 
  and 
  foliated 
  

   structure 
  of 
  the 
  gneisses, 
  it 
  is 
  concluded 
  that 
  these 
  are 
  all 
  

   genetically 
  related 
  in 
  the 
  Laurentian 
  mountain-building 
  de- 
  

   formation 
  which 
  acted 
  upon 
  the 
  magmatic 
  axial 
  mass 
  during 
  

   its 
  consolidation. 
  While 
  it 
  is 
  recognized 
  that 
  heterogeneity 
  in 
  

   a 
  magma 
  may 
  be 
  caused 
  by 
  the 
  stopping 
  off 
  and 
  partial 
  assimi- 
  

   lation 
  of 
  fragments 
  of 
  the 
  batholithic 
  roof, 
  it 
  is 
  concluded 
  

   from 
  the 
  field 
  evidence 
  that 
  the 
  principal 
  factor 
  in 
  bringing 
  

   about 
  the 
  heterogeneity 
  of 
  the 
  Laurentian 
  complex 
  was 
  dif- 
  

   ferentiation 
  aided 
  by 
  deformation 
  during 
  consolidation. 
  By 
  this 
  

   process, 
  the 
  magmatic 
  mass 
  was 
  constantly 
  being 
  broken 
  up, 
  

   and 
  the 
  residual 
  fluid 
  magma 
  of 
  slightly 
  different 
  composition 
  

   squeezed 
  out 
  to 
  fill 
  the 
  fractures 
  around 
  the 
  broken 
  fragments. 
  

   The 
  variations 
  in 
  the 
  complex 
  produced 
  in 
  this 
  way 
  were 
  then 
  

   flattened 
  out 
  and 
  crumpled 
  into 
  a 
  folded 
  structure 
  resembling 
  

   that 
  assumed 
  by 
  deformed 
  sedimentary 
  beds. 
  Thus 
  by 
  the 
  

   action 
  of 
  mountain-building 
  stresses 
  on 
  a 
  magmatic 
  axial 
  mass 
  

   a 
  folded 
  and 
  banded 
  gneissic 
  complex 
  such 
  as 
  that 
  occurring 
  in 
  

   the 
  Laurentian 
  plateau 
  may 
  be 
  .developed. 
  

  

  