﻿GEOLOGY 
  OF 
  THE 
  NORTH 
  CREEK 
  QUADRANGLE 
  

  

  2 
  9 
  

  

  seeming 
  to 
  conform 
  to 
  no 
  law. 
  . 
  . 
  . 
  These 
  primary 
  variations 
  in 
  

   the 
  rock 
  suffice 
  to 
  give 
  considerable 
  diversity 
  to 
  different 
  portions 
  

   within 
  a 
  limited 
  area, 
  but 
  this 
  diversity 
  is 
  greatly 
  intensified 
  by 
  cer- 
  

   tain 
  secondary 
  modifications 
  of 
  structure 
  and 
  composition. 
  As 
  a 
  

   result 
  of 
  the 
  combined 
  effect 
  of 
  primary 
  and 
  secondary 
  variations, 
  

   it 
  would 
  be 
  easy 
  to 
  collect, 
  within 
  an 
  area 
  of 
  a 
  few 
  square 
  rods, 
  a 
  

   half 
  dozen 
  or 
  more 
  specimens 
  whose 
  appearance 
  even 
  in 
  thin 
  section 
  

   would 
  scarcely 
  suggest 
  that 
  they 
  had 
  any 
  connection 
  with 
  one 
  an- 
  

   other." 
  Cushing 
  says 
  1 
  of 
  the 
  Adirondack 
  gabbros 
  in 
  general 
  that 
  

   they 
  show 
  much 
  variation, 
  both 
  primary 
  and 
  secondary, 
  from 
  place 
  

   to 
  place. 
  Both 
  of 
  these 
  investigators 
  proceed 
  to 
  discuss 
  the 
  sec- 
  

   ondary 
  variations 
  and 
  their 
  causes 
  but, 
  so 
  far 
  as 
  the 
  writer 
  is 
  aware, 
  

   little 
  or 
  no 
  attention 
  has 
  been 
  given 
  to 
  the 
  causes 
  of 
  the 
  primary 
  

   variations 
  which 
  will 
  be 
  considered 
  below. 
  

  

  Microscopic 
  features 
  

   Mineralogical 
  composition. 
  The 
  following 
  table 
  will 
  serve 
  to 
  

   show 
  the 
  great 
  range 
  in 
  mineralogical 
  composition 
  of 
  the 
  gabbro 
  

   and 
  its 
  derivatives. 
  The 
  figures 
  refer 
  to 
  percentages 
  by 
  volume 
  and 
  

   are 
  meant 
  to 
  be 
  close 
  approximations 
  only. 
  

  

  table 
  4 
  

   Mineralogical 
  composition 
  of 
  the 
  gabbro 
  and 
  its 
  derivatives 
  

  

  

  6 
  

  

  m 
  

  

  ."2 
  

  

  45 
  

   6 
  

   2 
  

   46 
  

   42 
  

   47 
  

  

  60 
  

   5 
  

  

  49 
  

   3 
  

   4 
  

  

  44 
  

  

  43 
  

  

  V 
  

   <n 
  

   ei 
  

   "o 
  

  

  

   si 
  

  

  O 
  

  

  4-5 
  

   15 
  

   10 
  

   10 
  

  

  5 
  

  

  20 
  

   5 
  

   32 
  

   32 
  

   15 
  

   50 
  

   45 
  

  

  w 
  

  

  O 
  

  

  "5i 
  

  

  a 
  

  

  c 
  

  

  c 
  

   

  

  c 
  

   si 
  

   u 
  

   0, 
  

  

  0) 
  

  

  '5b 
  

   < 
  

  

  bo 
  

   S 
  

  

  "c 
  

  

  'u 
  

  

  O 
  

  

  0) 
  

  

  c 
  

  

  Si 
  

   

  

  4) 
  

   'en 
  

   'O 
  

   SI 
  

  

  

   si 
  

  

  

  

  P. 
  

   < 
  

  

  '> 
  

  

  O 
  

  

  4; 
  

  

  'S 
  

   a 
  

  

  

  Lab. 
  "so 
  

   Lab.lso 
  

   01-Lab. 
  38 
  

   Lab. 
  30 
  

   Ol-Lab. 
  40 
  

   01-Lab. 
  30 
  

   Ol-Lab. 
  40 
  

   Ol-Lab. 
  40 
  

   Ol-Lab. 
  45 
  

   Ol-Lab. 
  10 
  

   01- 
  And 
  20 
  

   Ol-Lab. 
  57 
  

   Ol-Lab. 
  15 
  

   01- 
  And 
  15 
  

  

  " 
  *8 
  

  

  27 
  

   10 
  

  

  25 
  

   25 
  

   16 
  

   10 
  

   14 
  

   45 
  

   25 
  

   15 
  

   20 
  

   28 
  

  

  { 
  15 
  

  

  17 
  

  

  12.5 
  

  

  15 
  

  

  3 
  

  

  7 
  

  

  23 
  

  

  10 
  

  

  3 
  

  

  1 
  

  

  2.5 
  

  

  "•s 
  

  

  little 
  

   1 
  

   1 
  

   1 
  

   2 
  

   2 
  

   5 
  

   2 
  

  

  little 
  

   1 
  

  

  little 
  

  

  1 
  

  

  little 
  

  

  1 
  

   1 
  

  

  little 
  

  

  1 
  

   little 
  

   little 
  

  

  9 
  

   8 
  

  

  7 
  

   5 
  

   1 
  

   2 
  

   5 
  

   2 
  

  

  6 
  

   6 
  

   5 
  

  

  10 
  

  

  8 
  

  

  8 
  

  

  35 
  

  

  20 
  

  

  little 
  

  

  2 
  

  

  8 
  

  

  10 
  

   2 
  

   5 
  

  

  

  

  

  

  15 
  

  

  

  

  

  

  

  

  

  3 
  

  

  4 
  

  

  s 
  

  

  

  

  

  little 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  6 
  

  

  20 
  

   25 
  

   14 
  

   20 
  

  

  

  

  

  

  

  

  

  7 
  

  

  

  

  

  

  

  

  8 
  

  

  1 
  

  

  I 
  

  

  

  

  

  

  

  

  

  

  

  

  TO 
  

  

  

  

  little 
  

  

  little 
  

   little 
  

  

  

  

  

  TT 
  

  

  

  

  

  10 
  

  

  I 
  

  

  little 
  

  

  

  little 
  

  

  T? 
  

  

  

  

  

  

  13 
  

  

  T 
  1 
  

  

  

  8 
  

   2 
  

  

  2 
  

  

  I 
  

  

  2 
  

  

  8 
  

  

  

  little 
  

   little 
  

  

  

  

  

  

  

  

  

  

  

  Perhaps 
  the 
  most 
  striking 
  feature 
  brought 
  out 
  by 
  this 
  table 
  is 
  the 
  

   range 
  of 
  rock 
  types, 
  through 
  many 
  intermediate 
  phases, 
  from 
  a 
  

   very 
  basic 
  olivine 
  norite 
  to 
  quartz-hornblende 
  syenite. 
  Thus, 
  no. 
  1 
  

   is 
  an 
  olivine 
  norite 
  ; 
  nos. 
  2, 
  3, 
  4, 
  6, 
  7, 
  and 
  9 
  are 
  hornblende 
  norites 
  ; 
  

  

  N. 
  Y. 
  State 
  Mus. 
  Bui. 
  95, 
  p. 
  328. 
  

  

  