﻿44 
  ME. 
  T. 
  L. 
  WALKEK 
  ON 
  THE 
  [Feb. 
  1897, 
  

  

  evenly-bedded, 
  very 
  micaceous 
  strata 
  may 
  represent 
  altered 
  acid 
  

   tuffs 
  which 
  were 
  deposited 
  in 
  shallow 
  water. 
  Bonney 
  has 
  suggested 
  

   that 
  some 
  of 
  the 
  very 
  fine-grained, 
  indistinctly-bedded 
  muscovite- 
  

   quartzites 
  may 
  have 
  been 
  derived 
  by 
  devitrification 
  of 
  acid 
  glassy 
  or 
  

   porphyritic 
  rocks. 
  

  

  Exposures 
  of 
  highly-altered 
  quartzite 
  occur 
  south 
  of 
  the 
  Stobie 
  

   Mine, 
  and 
  also 
  on 
  the 
  main 
  line 
  of 
  the 
  Canadian 
  Pacific 
  Railway, 
  

   1^ 
  mile 
  west 
  of 
  Sudbury. 
  At 
  the 
  former 
  place, 
  the 
  altered 
  rock 
  

   becomes 
  quite 
  granitic 
  in 
  composition, 
  and 
  gneissoid 
  in 
  structure. 
  

   The 
  microscope 
  shows 
  that 
  the 
  component 
  minerals 
  are 
  quartz, 
  

   felspar, 
  biotite, 
  and 
  a 
  little 
  muscovite. 
  Quartz-grains 
  abound 
  in 
  

   fluid 
  inclusions, 
  are 
  irregular 
  in 
  outline, 
  and 
  generally 
  interlock. 
  

   Muscovite 
  forms 
  large 
  separate 
  individuals, 
  while 
  biotite 
  usually 
  

   forms 
  approximately-parallel 
  connected 
  aggregates 
  of 
  small 
  scales. 
  

   The 
  rock 
  exposed 
  on 
  the 
  railway 
  west 
  of 
  Sudbury 
  is 
  of 
  medium 
  

   grain 
  and 
  peculiarly 
  mottled 
  : 
  pale 
  pink, 
  roundish 
  spots, 
  from 
  1 
  to 
  

   4 
  inches 
  in 
  diameter, 
  dapple 
  a 
  groundwork 
  of 
  a 
  dark 
  grey 
  colour. 
  

   On 
  closer 
  examination, 
  it 
  is 
  seen 
  that 
  no 
  sharp 
  boundaries 
  exist 
  

   between 
  the 
  portions 
  of 
  different 
  colour, 
  and 
  a 
  microscopic 
  exami- 
  

   nation 
  shows 
  that 
  there 
  is 
  no 
  important 
  mineralogical 
  difference. 
  

   Gneissoid 
  structure 
  is 
  altogether 
  wanting. 
  Crystals 
  and 
  grains 
  of 
  

   reddish 
  garnet 
  occur 
  in 
  addition 
  to 
  the 
  minerals 
  present 
  in 
  the 
  

   rock 
  south 
  of 
  Stobie 
  Mine. 
  Considering 
  the 
  mineralogical 
  compo- 
  

   sition 
  of 
  these 
  rocks, 
  they 
  may 
  be 
  referred 
  to 
  as 
  biotite-granite. 
  

   Bell 
  has 
  shown 
  that 
  these 
  highly-altered 
  elastics 
  constitute 
  a 
  belt 
  

   \ 
  mile 
  wide 
  and 
  6 
  miles 
  long, 
  extending 
  from 
  near 
  the 
  Stobie 
  

   Mine 
  south-west 
  nearly 
  to 
  Copper 
  Cliff 
  Mines. 
  Naturally, 
  only 
  a 
  

   very 
  impure 
  quartzite 
  could 
  give 
  rise 
  to 
  such 
  rocks 
  as 
  these. 
  We 
  

   know 
  very 
  little 
  as 
  to 
  the 
  causes 
  of 
  this 
  extreme 
  and 
  apparently 
  

   selective 
  metamorphism. 
  Rocks 
  of 
  granitic 
  composition 
  and 
  struc- 
  

   ture, 
  when 
  formed 
  by 
  the 
  regeneration 
  of 
  elastics, 
  may 
  be 
  called 
  

   ' 
  regenerated 
  granites.' 
  There 
  is 
  reason 
  to 
  believe 
  that 
  this 
  is 
  a 
  

   more 
  fruitful 
  source 
  of 
  granitoid 
  rocks 
  than 
  has 
  been 
  previously 
  

   acknowledged. 
  

  

  (ii) 
  Mica-Schists. 
  

  

  In 
  the 
  immediate 
  vicinity 
  of 
  Sudbury 
  these 
  rocks, 
  though 
  occa- 
  

   sionally 
  present, 
  play 
  a 
  very 
  subordinate 
  part. 
  They 
  generally 
  dip 
  

   at 
  high 
  angles, 
  and 
  are 
  more 
  frequent 
  towards 
  the 
  centre 
  of 
  the 
  

   Huronian 
  belt. 
  A 
  very 
  narrow 
  band 
  of 
  silvery 
  grey 
  mica-schist 
  

   crosses 
  the 
  railway 
  about 
  \ 
  mile 
  east 
  of 
  Murray 
  Mines. 
  In 
  thin 
  

   sections 
  the 
  foliation 
  is 
  very 
  distinct. 
  Muscovite 
  forms 
  a 
  net- 
  

   work 
  which 
  surrounds 
  the 
  quartz-grains. 
  Immediately 
  east 
  of 
  

   "Worthing 
  ton 
  Station 
  a 
  similar 
  rock 
  is 
  exposed 
  in 
  the 
  railway- 
  

   cuttings. 
  Farther 
  south-west 
  the 
  Huronian 
  belt 
  is 
  much 
  richer 
  

   in 
  mica- 
  schists, 
  which 
  are 
  often 
  hornblendic 
  and 
  staurolitic. 
  

   Between 
  Blezard 
  and 
  Stobie 
  Mines 
  a 
  dark, 
  compact, 
  schistose 
  rock 
  

   occurs, 
  which 
  the 
  microscope 
  shows 
  to 
  be 
  a 
  hornblende-epidote- 
  

   schist 
  ; 
  it 
  is 
  perhaps 
  geologically 
  an 
  equivalent 
  of 
  the 
  mica-schists. 
  

  

  