﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  

  

  -^17 
  

  

  reversed 
  in 
  the 
  two. 
  Calculation 
  of 
  its 
  norm 
  gives 
  the 
  following 
  

   result 
  : 
  

  

  Or 
  .. 
  

  

  . 
  31.69^ 
  

  

  Ab 
  .. 
  

  

  . 
  . 
  26.20 
  

  

  An 
  .. 
  

  

  • 
  5-o<^ 
  

  

  Co 
  .. 
  

  

  . 
  1 
  . 
  50 
  

  

  Qz 
  .. 
  

  

  . 
  30 
  -40^ 
  

  

  Ily 
  .. 
  

  

  . 
  2.46I 
  

  

  & 
  Mt 
  . 
  . 
  

  

  . 
  1.98/ 
  

  

  95-29 
  

  

  \ 
  4-44 
  

  

  Class 
  I, 
  persalane 
  

   Order 
  4, 
  britannare 
  

   Rang 
  2, 
  toscanase 
  

   Subrang 
  3, 
  toscanose 
  

  

  The 
  rock 
  of 
  analysis 
  5 
  was 
  not 
  the 
  normal 
  acid 
  granite 
  gneiss 
  of 
  

   the 
  locality 
  where 
  it 
  was 
  collected, 
  but 
  somewhat 
  darker 
  colored, 
  

   more 
  basic 
  in 
  appearance, 
  and 
  the 
  field 
  relations 
  definitely 
  suggested 
  

   that 
  it 
  had 
  soaked 
  up 
  some 
  amphibolite. 
  Nevertheless 
  the 
  analysis 
  

   shows 
  that 
  this 
  contamination 
  is 
  in 
  slight 
  amount, 
  and 
  the 
  rock 
  is 
  

   to 
  be 
  classified 
  in 
  the 
  same 
  group 
  as 
  its 
  predecessor, 
  as 
  its 
  calcu- 
  

   lated 
  norm 
  shows. 
  

  

  II 
  & 
  

  

  Or 
  .. 
  

  

  . 
  . 
  26. 
  13^ 
  

  

  Ab 
  .. 
  

  

  •• 
  31-44 
  

  

  An 
  .. 
  

  

  .. 
  7-51 
  

  

  Co 
  .. 
  

  

  •- 
  1-83 
  

  

  Qz 
  .. 
  

  

  . 
  . 
  26.94J 
  

  

  Hy 
  .. 
  

  

  -. 
  2.50- 
  

  

  Mt 
  .. 
  

  

  . 
  . 
  2.70 
  

  

  Py... 
  

  

  . 
  . 
  . 
  29^ 
  

  

  93-85 
  

  

  5-49 
  

  

  Class 
  I, 
  persalane 
  

   Order 
  4, 
  britannare 
  

   Rang 
  2, 
  toscanase 
  

  

  Subrang 
  3, 
  toscanose 
  

  

  The 
  mode 
  of 
  these 
  rocks 
  differs 
  so 
  little 
  from 
  the 
  norm 
  that 
  it 
  is 
  

   not 
  thought 
  worth 
  while 
  to 
  present 
  the 
  calculation. 
  Both 
  rocks 
  con- 
  

   sist 
  chiefly 
  of 
  feldspars 
  and 
  quartz, 
  with 
  biotite 
  as 
  the 
  principal 
  

   additional 
  mineral, 
  a 
  little 
  magnetite, 
  and 
  trifling 
  amounts 
  of 
  apatite, 
  

   zircon, 
  titanite, 
  muscovite 
  and 
  pyrite. 
  These 
  minerals 
  taken 
  to- 
  

   gether 
  only 
  amount 
  to 
  about 
  6^^ 
  in 
  the 
  first 
  case 
  and 
  8;^ 
  in 
  the 
  second. 
  

   In 
  each 
  case 
  the 
  surplus 
  of 
  alumina 
  in 
  the 
  norm, 
  calculated 
  as 
  

   corundum, 
  is 
  in 
  just 
  the 
  proper 
  amount 
  to 
  combine 
  with 
  the 
  

   magnesia 
  to 
  form 
  biotite. 
  

  

  Bleached 
  granite 
  

  

  The 
  rock 
  of 
  analysis 
  i 
  is 
  from 
  the 
  margin 
  of 
  a 
  small 
  granite 
  

   boss-cutting 
  limestone, 
  north 
  of 
  Redwood, 
  which 
  we 
  regard 
  as 
  being 
  

   of 
  Laurentian 
  age, 
  and 
  is 
  a 
  fresh 
  sample 
  of 
  granite 
  whitened 
  by 
  

   adjacent 
  limestone. 
  It 
  is 
  a 
  somewhat 
  more 
  acid 
  rock 
  than 
  the 
  

   preceding. 
  Unfortunately 
  no 
  samples 
  which 
  seemed 
  satisfactory 
  

  

  