﻿GEOLOGY 
  OF 
  THE 
  PORT 
  LEYDEN 
  QUADRANGLE 
  I7 
  

  

  vicinity 
  of 
  the 
  contact 
  and 
  which 
  while 
  less 
  abundant, 
  are 
  found 
  

   throughout 
  practically 
  the 
  whole 
  extent 
  of 
  the 
  bathylith." 
  Judg- 
  

   ing 
  from 
  his 
  descriptions 
  of 
  the 
  amphibolites, 
  the 
  inclusions 
  in 
  

   the 
  Port 
  Leyden 
  region 
  are 
  very 
  similar 
  to 
  them 
  and, 
  although 
  

   we 
  have 
  here 
  no 
  such 
  positive 
  evidence 
  for 
  their 
  origin, 
  the 
  ex- 
  

   planation 
  above 
  given 
  by 
  Professor 
  Adams 
  becomes 
  very 
  sug- 
  

   gestive 
  at 
  least. 
  

  

  In 
  a 
  general 
  way 
  at 
  least, 
  another 
  distinction 
  from 
  the 
  syenite 
  

   is 
  the 
  more 
  complete 
  granulation 
  of 
  the 
  granitic 
  gneisses. 
  Under 
  

   the 
  microscope 
  the 
  cataclastic 
  structure 
  is 
  always 
  well 
  exhibited, 
  

   sometimes 
  to 
  a 
  remarkable 
  degree. 
  The 
  quartzes 
  were 
  most 
  

   badly 
  broken 
  by 
  the 
  grinding 
  action 
  and 
  strain 
  shadows 
  are 
  

   common. 
  

  

  In 
  thin 
  section 
  the 
  typical 
  red 
  granitic 
  syenite 
  from 
  near 
  the 
  

   lower 
  road 
  crossing 
  on 
  Otter 
  creek 
  is 
  seen 
  to 
  consist 
  of 
  about 
  

   6ofc 
  of 
  feldspar; 
  35;;^ 
  of 
  quartz; 
  3^ 
  of 
  hornblende; 
  2^ 
  of 
  mag- 
  

   netite, 
  and 
  a 
  very 
  little 
  zircon 
  and 
  apatite. 
  The 
  feldspar 
  is 
  

   chiefly 
  microperthite 
  accompanied 
  by 
  some 
  anorthoclase 
  and 
  a 
  

   little 
  oligoclase. 
  Red 
  hematite 
  stains 
  are 
  common 
  in 
  the 
  sec- 
  

   tions. 
  Closel}^ 
  associated 
  with 
  this 
  typical 
  rock, 
  but 
  always 
  in 
  

   subordinate 
  amount, 
  is 
  a 
  gray, 
  less 
  quartzose 
  and 
  more 
  truly 
  

   syenitic 
  rock. 
  In 
  all 
  of 
  the 
  sections 
  of 
  the 
  granitic 
  syenite 
  exam- 
  

   ined 
  the 
  feldspar 
  ranges 
  from 
  60 
  to 
  yo^. 
  Microperthite 
  is 
  the 
  

   chief 
  feldspar, 
  while 
  anorthoclase 
  ranges 
  from 
  absence 
  to 
  20;^, 
  

   and 
  oligoclase 
  never 
  exceeds 
  5^. 
  The 
  quartz 
  range 
  is 
  from 
  25 
  

   to 
  4ofc. 
  Hornblende 
  is 
  always 
  present 
  but 
  never 
  above 
  5;^. 
  Bio- 
  

   tite 
  is 
  often 
  absent 
  and 
  never 
  exceeds 
  2^. 
  From 
  i 
  to 
  4^ 
  of 
  

   magnetite 
  always 
  occurs. 
  Small 
  crystals 
  of 
  apatite 
  and 
  zircon 
  

   are 
  common. 
  

  

  It 
  seems 
  certain 
  that 
  this 
  red 
  granitic 
  gneiss 
  is 
  a 
  differentia- 
  

   tion 
  pliase 
  of 
  the 
  normal 
  syenite 
  gneiss. 
  Except 
  for 
  the 
  greater 
  

   granulation 
  and 
  somewhat 
  higher 
  quartz 
  content, 
  microscopic 
  

   study 
  shows 
  no 
  difterence 
  betw^een 
  the 
  rocks. 
  In 
  the 
  field 
  no 
  

   sharp 
  line 
  of 
  separation 
  can 
  be 
  drawn. 
  The 
  normal 
  syenite 
  in 
  

   general 
  seems 
  to 
  become 
  more 
  quartzose 
  toward 
  the 
  north 
  so 
  

   that 
  in 
  this 
  respect, 
  at 
  least, 
  the 
  syenite 
  around 
  Partridgeville 
  

   closely 
  approaches 
  the 
  granitic 
  syenite. 
  The 
  writer 
  is 
  inclined 
  

   to. 
  the 
  belief 
  that 
  the 
  passage 
  from 
  one 
  rock 
  to 
  the 
  other 
  is 
  much 
  

   like 
  that 
  described 
  by 
  Smyth 
  in 
  the 
  Diana 
  area 
  some 
  20 
  or 
  25 
  

   miles 
  northward. 
  He 
  says 
  : 
  ^ 
  '' 
  Passing 
  southward 
  from 
  the 
  

   latter 
  (limestone 
  formation) 
  the 
  syenite 
  at 
  first 
  slowly 
  and 
  irreg- 
  

  

  ^ 
  loc, 
  cit. 
  p. 
  481-82. 
  

  

  