﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  49 
  

  

  Small 
  titanites 
  abound 
  in 
  the 
  rock, 
  magnetite 
  and 
  hematite 
  appear 
  in 
  

   varying 
  quantity, 
  with 
  pyrite, 
  apatite 
  and 
  zircon 
  as 
  other 
  acces- 
  

   sories. 
  

  

  Quartz 
  is 
  present 
  in 
  many 
  of 
  the 
  bands 
  but 
  seldom 
  in 
  any 
  great 
  

   quantity 
  and 
  often 
  wholly 
  absent. 
  The 
  feldspar 
  is 
  in 
  part 
  micro- 
  

   cline 
  and 
  in 
  part 
  plagioclase 
  (andesine-labradorite) 
  ; 
  some 
  micro- 
  

   perthite 
  is 
  usually 
  found 
  also, 
  and 
  often 
  much 
  feldspar 
  not 
  char- 
  

   acteristically 
  marked. 
  

  

  In 
  addition 
  to 
  the 
  above 
  minerals 
  the 
  rock 
  nearly 
  always 
  con- 
  

   tains 
  calcite, 
  and 
  this 
  in 
  steadily 
  increasing 
  quantity 
  as 
  the 
  dis- 
  

   tance 
  from 
  the 
  granite 
  bathylith 
  increases. 
  The 
  rocks 
  from 
  the 
  

   schist 
  inlier 
  in 
  the 
  Potsdam 
  due 
  east 
  from 
  Omar, 
  average 
  20 
  to 
  

   2^^ 
  of 
  calcite; 
  in 
  the 
  long 
  ridge 
  just 
  to 
  the 
  north 
  of 
  this 
  it 
  occurs 
  

   in 
  large, 
  though 
  somewhat 
  less 
  amount; 
  while 
  in 
  the 
  ridge 
  north- 
  

   west 
  of 
  this, 
  and 
  nearest 
  the 
  granite, 
  much 
  of 
  the 
  rock 
  shows 
  but 
  

   little 
  calcite, 
  only 
  the 
  coarser, 
  mottled 
  beds 
  having 
  it 
  in 
  quantity. 
  

   The 
  calcite 
  is 
  coarsely 
  crystalline, 
  in 
  sharply 
  bounded 
  individuals, 
  

   and 
  clearly 
  formed 
  at 
  the 
  same 
  time 
  as 
  the 
  other 
  constituents 
  of 
  

   the 
  rock. 
  

  

  The 
  mineralogy 
  of 
  the 
  schists 
  strongly 
  suggests 
  contact 
  effects, 
  

   the 
  tourmalin, 
  actinolite 
  and 
  epidote 
  being 
  especially 
  suggestive 
  in 
  

   this 
  respect, 
  none 
  of 
  them 
  being 
  normal 
  Grenville 
  minerals, 
  away 
  

   from 
  the 
  immediate 
  vicinity 
  of 
  igneous 
  rocks. 
  The 
  green 
  pyrojc-, 
  

   ene 
  also 
  is 
  an 
  abundantly 
  formed 
  contact 
  mineral 
  in 
  the 
  Grenviile, 
  . 
  

   though 
  not 
  so 
  distinctive 
  of 
  contact 
  metamorphism 
  as 
  the 
  others. 
  

   These, 
  with 
  the 
  constant 
  presence 
  of 
  calcite, 
  give 
  an 
  impression 
  

   that 
  we 
  are 
  here 
  dealing 
  with 
  a 
  limestone 
  belt 
  much 
  changed 
  by 
  

   contact 
  action, 
  with 
  the 
  granite 
  and 
  pegmatite 
  dikes 
  which 
  abund- 
  

   antly 
  penetrate 
  the 
  series 
  as 
  the 
  source 
  of 
  the 
  mineralizing 
  fluids. 
  

   The 
  fact 
  that 
  these 
  green 
  schists, 
  though 
  here 
  present 
  in 
  great 
  

   bulk, 
  are 
  not 
  a 
  usual 
  member 
  of 
  the 
  Grenville 
  succession 
  in 
  the 
  

   general 
  region, 
  also 
  suggests 
  a 
  local 
  cause 
  for 
  their 
  presence. 
  It 
  

   would 
  seem 
  that 
  a 
  series 
  so 
  thick 
  could 
  not 
  but 
  occur 
  repeatedly 
  

   elsewhere 
  were 
  it 
  an 
  ordinary 
  member 
  of 
  the 
  general 
  series. 
  Sim- 
  

   ilar 
  rocks 
  do 
  occur 
  in 
  small 
  bulk 
  in 
  the 
  general 
  schist 
  series 
  north 
  

   of 
  Millsite 
  lake, 
  but 
  their 
  small 
  amount 
  here 
  but 
  emphasizes 
  the 
  

   bulk 
  of 
  the 
  other 
  occurrence. 
  

  

  As 
  opposed 
  to 
  this 
  suggestion 
  of 
  contact 
  origin, 
  the 
  breadth 
  of 
  

   the 
  belt 
  and 
  the 
  distance 
  it 
  extends 
  from 
  the 
  granite 
  margin, 
  

   its 
  general 
  uniformity 
  of 
  character, 
  whether 
  in 
  contact 
  with 
  a 
  dike 
  

   or 
  at 
  a 
  considerable 
  distance 
  from 
  one, 
  whether 
  near 
  the 
  

   granite 
  margin 
  or 
  remote 
  from 
  it, 
  (the 
  only 
  observed 
  difference 
  

  

  