﻿GEOLOGY 
  OF 
  THE 
  PORT 
  LEYDEN 
  QUADRANGLE 
  I5 
  

  

  cal 
  rock 
  in 
  the 
  Diana-Pitcairn 
  area, 
  the 
  dark 
  minerals, 
  especially 
  

   pyroxene, 
  are 
  prominent 
  constituents, 
  while 
  in 
  the 
  Port 
  Leyden 
  

   district 
  the 
  pyroxene 
  is 
  always 
  absent 
  and 
  the 
  dark 
  minerals 
  

   never 
  amount 
  to 
  more 
  than 
  7 
  or 
  ^<;L 
  Otherwise 
  the 
  rocks 
  are 
  

   very 
  similar. 
  In 
  passing 
  northwestward 
  from 
  Little 
  Falls 
  to 
  

   Port 
  Leyden 
  the 
  syenite 
  loses 
  its 
  pyroxene 
  and 
  the 
  microperthite 
  

   becomes 
  more 
  prominent 
  than 
  the 
  anorthoclase. 
  

  

  It 
  is 
  now 
  well 
  established, 
  especially 
  by 
  the 
  excellent 
  work 
  of 
  

   Smyth,^ 
  that 
  the 
  syenite 
  is 
  a 
  plutonic 
  igneous 
  rock 
  which 
  has 
  

   been 
  intruded 
  into 
  and 
  is 
  therefore 
  younger 
  than 
  the 
  Grenville. 
  

   The 
  evidences 
  from 
  the 
  Port 
  Leyden 
  region 
  are 
  clearh^ 
  in 
  har- 
  

   mony 
  with 
  this 
  view. 
  Thus 
  the 
  Grenville 
  area 
  east 
  of 
  Fowlers- 
  

   ville 
  is 
  surrounded 
  by 
  pure 
  syenite 
  and 
  the 
  writer 
  is 
  convinced 
  

   that 
  we 
  have 
  here 
  a 
  good 
  example 
  of 
  a 
  large 
  Grenville 
  inclusion 
  

   in 
  the 
  syenite. 
  Significant 
  in 
  this 
  connection 
  is 
  the 
  fact 
  that 
  

   the 
  strike 
  of 
  the 
  foliation 
  in 
  the 
  Grenville 
  is 
  north 
  and 
  south 
  

   while 
  that 
  of 
  the 
  nearby 
  syenite 
  is 
  about 
  n. 
  30° 
  e. 
  This 
  would 
  

   be 
  expected 
  especially 
  where 
  large 
  sedimentary 
  masses 
  were 
  

   caught 
  up 
  in 
  the 
  molten 
  syenite. 
  Near 
  Lyonsdale, 
  on 
  the 
  south 
  

   side 
  of 
  the 
  river, 
  the 
  syenite 
  and 
  Grenville 
  are 
  in 
  sharp 
  contact 
  

   while 
  north 
  of 
  the 
  river 
  they 
  appear 
  to 
  blend 
  into 
  each 
  other. 
  

   Around 
  Kosterville 
  no 
  sharp 
  contacts 
  are 
  seen 
  but 
  the 
  syenite 
  

   and 
  Grenville 
  seem 
  to 
  be 
  mixed 
  around 
  the 
  borders 
  of 
  the 
  Gren- 
  

   ville. 
  Referring 
  to 
  similar 
  phenomena 
  farther 
  northward 
  Smyth- 
  

   says 
  : 
  " 
  Some 
  of 
  these 
  inclusions 
  are 
  clearly 
  defined 
  with 
  sharp 
  

   boundaries 
  but 
  others 
  are 
  somewhat 
  blended 
  Avith 
  the 
  surround- 
  

   ing 
  syenite 
  as 
  though 
  they 
  had 
  undergone 
  a 
  partial 
  melting." 
  

   The 
  small 
  basic 
  inclusions 
  above 
  mentioned 
  and 
  the 
  very 
  inti- 
  

   mate 
  mixture 
  of 
  syenite 
  and 
  Grenville 
  on 
  a 
  large 
  scale 
  as 
  de- 
  

   scribed 
  below 
  also 
  argue 
  for 
  the 
  intrusive 
  character 
  of 
  the 
  

   syenite. 
  

  

  Granitic 
  syenite 
  gneiss 
  

  

  In 
  the 
  northern 
  portion 
  of 
  the 
  quadrangle, 
  and 
  on 
  either 
  side 
  

   of 
  Black 
  river, 
  two 
  areas 
  of 
  granitic 
  syenite 
  gneiss 
  are 
  shown 
  

   on 
  the 
  geologic 
  map. 
  These 
  areas 
  are 
  probably 
  continuous 
  

   under 
  the 
  broad 
  drift-filled 
  valley 
  bottom. 
  This 
  rock 
  is 
  almost 
  

   certainly 
  a 
  granitic 
  phase 
  of 
  the 
  normal 
  syenite 
  above 
  described, 
  

   and, 
  since 
  the 
  one 
  rock 
  grades 
  into 
  the 
  other, 
  the 
  drawing 
  of 
  a 
  

   boundary 
  line 
  must 
  of 
  necessity 
  be 
  an 
  arbitrary 
  matter. 
  In 
  

  

  Woe. 
  cit. 
  

  

  ^loc. 
  cit. 
  p. 
  477. 
  

  

  