﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  183 
  

  

  Norm 
  of 
  Alexandria 
  

  

  syenite, 
  analysis 
  i 
  : 
  

  

  Or.,.. 
  33.36^ 
  

   Ab.... 
  36.68 
  

   An.... 
  II. 
  12 
  

   Co.... 
  1.85 
  

   Qz.... 
  4.14J 
  

  

  '87-15 
  

  

  Glass 
  I, 
  persalane 
  

   Order 
  5, 
  Canadare 
  

   Rang 
  2, 
  pulaskase 
  

   Subrang 
  3, 
  pulaskose 
  

  

  Hy.... 
  5.00' 
  

   Mt.... 
  4.18I 
  ^ 
  

   Fl.... 
  0.78 
  1 
  ^ 
  

  

  

  Ap.... 
  1.34^ 
  

  

  

  

  The 
  rock 
  itself 
  contains 
  considerable 
  green 
  horblende 
  and 
  biotite 
  

   which, 
  together 
  with 
  the 
  accessory 
  magnetite, 
  titanite, 
  apatite 
  and 
  

   pyrite, 
  constitute 
  about 
  15;^ 
  of 
  the 
  rock, 
  (elsewhere 
  they 
  run 
  up 
  

   to 
  25 
  or 
  30;^, 
  carrying 
  the 
  rock 
  into 
  the 
  dosalane 
  class) 
  meaning 
  

   of 
  course 
  that 
  some 
  of 
  the 
  lime, 
  alumina 
  and 
  potash 
  calculated 
  

   with 
  tlie 
  salic 
  minerals 
  of 
  the 
  norm 
  are 
  in 
  the 
  hornblende 
  and 
  

   biotite. 
  ]\Iicrocline, 
  microperthite 
  and 
  oligoclase 
  are 
  all 
  present 
  in 
  

   some 
  quantity, 
  plagioclase 
  being 
  somewhat 
  in 
  excess. 
  Some 
  of 
  the 
  

   microperthite 
  is 
  secondary 
  after 
  oligoclase. 
  The 
  rock 
  has 
  beautiful 
  

   cataclastic 
  structure, 
  showing 
  much 
  more 
  crushing 
  than 
  the 
  Picton 
  

   granite. 
  Chemically 
  it 
  is 
  seen 
  to 
  be 
  very 
  close 
  to 
  the 
  green 
  syenites 
  

   of 
  similar 
  silica 
  percentage, 
  the 
  chief 
  difference 
  being 
  in 
  the 
  higher 
  

   magnesia 
  and 
  in 
  the 
  relative 
  proportions 
  of 
  ferric 
  and 
  ferrous 
  

   iron 
  and 
  of 
  the 
  alkalies. 
  The 
  higher 
  magnesia 
  expresses 
  itself 
  

   mineralogically 
  in 
  the 
  formation 
  of 
  hornblende 
  and 
  biotite, 
  in- 
  

   stead 
  of 
  the 
  pyroxenes 
  of 
  the 
  green 
  syenite. 
  The 
  general 
  rock 
  

   is 
  somewhat 
  more 
  basic, 
  and 
  with 
  a 
  higher 
  percentage 
  of 
  ferro- 
  

   magnesian 
  minerals 
  than 
  the 
  normal 
  green 
  syenite. 
  

  

  The 
  augen 
  gneiss 
  of 
  analysis 
  4 
  is 
  a 
  much 
  more 
  acid 
  rock, 
  a 
  tosca- 
  

   nose, 
  suggesting 
  caution 
  in 
  attempting 
  to 
  account 
  for 
  it 
  as 
  a 
  

   phase 
  of 
  the 
  syenite. 
  The 
  analysis 
  is 
  so 
  close 
  to 
  that 
  of 
  the 
  Picton 
  

   granite 
  of 
  the 
  last 
  column 
  as 
  to 
  be 
  almost 
  grotesque. 
  Quite 
  cer- 
  

   tainly 
  it 
  has 
  no 
  relation 
  whatever 
  to' 
  the 
  Picton 
  granite, 
  though 
  

   mimicing 
  it 
  so 
  closely 
  chemically. 
  The 
  green 
  syenites 
  of 
  the 
  region 
  

   show 
  wider 
  range 
  of 
  variation 
  than 
  that 
  shown 
  in 
  this 
  case, 
  never- 
  

   theless 
  the 
  intrusion 
  here 
  is 
  of 
  such 
  comparatively 
  small 
  size 
  that 
  

   variation 
  in 
  composition 
  to 
  this 
  amount 
  would 
  be 
  quite 
  unusual. 
  

   Hence 
  the 
  analyses 
  rather 
  tend 
  to 
  reinforce 
  Smyth's 
  conclusion 
  

   that 
  we 
  really 
  have 
  here 
  two 
  separate 
  small 
  intrusions, 
  side 
  by 
  side. 
  

  

  Mineralogically 
  the 
  augen 
  gneiss 
  consists 
  of 
  quartz, 
  feldspars 
  

   and 
  biotite, 
  with 
  accessory 
  magnetite, 
  titanite 
  and 
  apatite, 
  and 
  

  

  