﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  43 
  

  

  dandy 
  in 
  the 
  aplite 
  dikes 
  of 
  the 
  granite 
  gneiss 
  itself, 
  and 
  regard 
  

   the 
  granite 
  of 
  the 
  dikes 
  as 
  likely 
  Picton. 
  

  

  The 
  contact 
  relations 
  of 
  this 
  rock 
  with 
  those 
  adjacent 
  are 
  of 
  

   much 
  interest. 
  It 
  was 
  apparently 
  richer 
  in 
  mineralizing 
  fluids 
  

   than 
  any 
  of 
  the 
  other 
  intrusives, 
  and 
  gives 
  rise 
  to 
  interesting 
  

   contact 
  rocks, 
  to 
  be 
  described 
  in 
  the 
  succeeding 
  section. 
  But 
  

   the 
  field 
  relations 
  are 
  also 
  most 
  important 
  and 
  interesting. 
  

  

  While 
  mapping 
  Wellesley 
  and 
  Grindstone 
  islands 
  it 
  quickly 
  

   caught 
  our 
  attention 
  that 
  the 
  abundant 
  inclusions 
  with 
  which 
  

   the 
  Picton 
  granite 
  is 
  everywhere 
  charged 
  were 
  arranged 
  in 
  belts, 
  

   that 
  is, 
  along 
  a 
  given 
  line 
  the 
  inclusions 
  were 
  all 
  quartzite, 
  along 
  

   an 
  adjoining 
  line 
  they 
  were 
  all 
  amphibolite, 
  along 
  another 
  

   nothing 
  but 
  granite 
  gneiss 
  inclusions 
  appeared. 
  It 
  was 
  also 
  

   seen 
  that 
  these 
  belts 
  had 
  northeast-southwest 
  trend, 
  concordant 
  

   with 
  the 
  general 
  rock 
  strike 
  of 
  the 
  region, 
  and 
  that 
  further 
  the 
  

   individual 
  inclusions 
  to 
  large 
  extent 
  retained 
  their 
  original 
  

   orientation 
  and 
  dip, 
  notwithstanding 
  the 
  intrusion. 
  Our 
  strikes 
  

   and 
  dips, 
  read 
  on 
  the 
  rocks 
  in 
  the 
  field, 
  gave 
  absolutely 
  con- 
  

   cordant 
  results 
  as 
  we 
  passed 
  from 
  one 
  inclusion 
  to 
  another, 
  

   results 
  also 
  concordant 
  with 
  the 
  readings 
  obtained 
  on 
  the 
  same 
  

   rocks 
  beyond 
  the 
  reach 
  of 
  the 
  intrusion. 
  We 
  were 
  able 
  to 
  map 
  

   the 
  original 
  belts 
  of 
  Grenville 
  quartzite 
  and 
  schist, 
  and 
  the 
  

   intrusions 
  of 
  Laurentian 
  granite 
  gneiss, 
  as 
  accurately 
  as 
  though 
  

   the 
  Picton 
  granite 
  was 
  not 
  present, 
  so 
  little 
  had 
  they 
  been 
  dis- 
  

   turbed 
  by 
  the 
  intrusion. 
  An 
  attempt 
  has 
  been 
  made 
  to 
  bring 
  

   out 
  these 
  facts 
  upon 
  the 
  geologic 
  maps. 
  We 
  could 
  only 
  account 
  

   for 
  the 
  phenomena 
  on 
  the 
  assumption 
  that 
  we 
  have 
  exposed 
  here 
  

   the 
  very 
  roof 
  of 
  this 
  portion 
  of 
  the 
  bathylith, 
  the 
  abundant 
  

   inclusions 
  representing 
  masses 
  but 
  just 
  loosened 
  from 
  their 
  

   original 
  place, 
  not 
  greatly 
  sunken, 
  and 
  preserving 
  unimpaired 
  

   their 
  original 
  orientation. 
  If 
  this 
  be 
  the 
  correct 
  interpretation, 
  

   the 
  locality 
  furnishes 
  a 
  fine 
  illustration 
  of 
  the 
  general 
  phe- 
  

   nomenon. 
  

  

  Other 
  intrusions. 
  While 
  the 
  above 
  furnish 
  the 
  only 
  examples 
  

   of 
  intrusions 
  of 
  considerable 
  size 
  in 
  the 
  region, 
  there 
  are 
  many 
  

   others 
  of 
  small 
  size, 
  mostly 
  too 
  small 
  to 
  map, 
  and 
  which 
  it 
  

   seems 
  hardly 
  worth 
  while 
  to 
  describe 
  in 
  detail. 
  These 
  are 
  chiefly 
  

   of 
  granite 
  gneiss, 
  and 
  are 
  regarded 
  for 
  the 
  most 
  part 
  as 
  of 
  

   Laurentian 
  age, 
  and 
  as 
  representing 
  comparatively 
  small 
  upward 
  

   protrusions 
  from 
  the 
  general 
  roof 
  of 
  the 
  great 
  mass 
  of 
  Laurentian 
  

   granite 
  gneiss 
  which 
  is 
  believed 
  to 
  underlie 
  the 
  entire 
  district, 
  

   except 
  where 
  broken 
  through 
  by 
  the 
  later 
  intrusions. 
  A 
  good 
  

  

  