﻿GEOLOGY 
  OF 
  THE 
  NORTH 
  CREEK 
  QUADRANGLE 
  

  

  37 
  

  

  Table 
  8 
  

   Mineralogical 
  composition 
  of 
  each 
  contact 
  zone 
  

  

  6 
  

   c 
  

   <u 
  

   C 
  

   

   S3 
  

  

  M 
  

  

  o 
  

  

  6 
  

  

  

  

  O 
  

  

  0J 
  ' 
  

  

  is 
  

  

  

  

  M 
  

   a) 
  

  

  

  

  C 
  

  

  D 
  

  

  3 
  

  

  c 
  

  

  O 
  

  

  K 
  

  

  C 
  

  

  

  

  u 
  

  

  3 
  

   O 
  

  

  4) 
  

  

  O 
  

  

  s 
  

  

  c 
  

   so 
  

  

  

  

  Ih 
  

  

  c5 
  

  

  "S 
  

  

  S3 
  

  

  

   >. 
  

  

  PL: 
  

  

  c 
  

  

  s- 
  

   O 
  

  

  

  

  

  

  Ol-lab 
  

  

  

  

  

  

  

  

  

  

  

  I 
  

  

  5 
  

  

  

  

  45 
  

   Ol-lab 
  

  

  14 
  

  

  20 
  

  

  

  6 
  

  

  2 
  

  

  

  

  I 
  

  

  2 
  

  

  

  

  

  

  

  

  2 
  

  

  32 
  

  

  Bio 
  

   Lik 
  

  

  

  

  10 
  

  

  with 
  some 
  

  

  Ol-and 
  

  

  45 
  

  

  jfeld 
  

  

  

  

  6 
  

  

  2 
  

  

  • 
  

  

  little 
  

  

  

  little 
  

  

  5 
  

  

  3 
  

   4 
  

  

  tite-s 
  

   3 
  No. 
  

  

  :hist 
  

   6 
  

  

  spar 
  

  

  

  5 
  

  

  28 
  

  

  

  

  50 
  

   Ol-and 
  

  

  20 
  

  

  

  I 
  

  

  

  1 
  

   2 
  

  

  little 
  

  

  little 
  

  

  

  

  

  

  

  

  6 
  

  

  15 
  

   Lik 
  

  

  

  

  5 
  

   Ol-and 
  

  

  72 
  

  

  

  

  

  7 
  

  

  1 
  

   2 
  

  

  1 
  

   1 
  

  

  little 
  

  

  

  7 
  

  

  3 
  No. 
  

  

  5 
  

  

  

  

  

  

  8 
  

  

  33 
  

  

  

  

  55 
  

   Ol-and 
  

  

  10 
  

  

  

  I 
  

  

  

  

  1 
  

   2 
  

  

  1 
  

   2 
  

  

  little 
  

  

  

  

  

  

  

  

  

  9 
  

  

  40 
  

  

  J 
  5 
  

  

  4 
  

  

  5 
  

  

  5 
  

  

  

  30 
  

  

  

  1 
  

   2 
  

  

  little 
  

  

  

  

  1 
  

  

  

  

  

  A 
  noteworthy 
  feature 
  is 
  the 
  fact 
  that 
  the 
  strike 
  of 
  the 
  foliation 
  

   of 
  the 
  very 
  gneissoid 
  country 
  rock 
  is 
  nearly 
  at 
  right 
  angles 
  to 
  the 
  

   gabbro-granite 
  contact, 
  while 
  the 
  clearly 
  defined 
  contact 
  zones 
  are 
  

   parallel 
  to 
  the 
  contact. 
  

  

  Other 
  features 
  of 
  ' 
  special 
  interest 
  are 
  the 
  syenitic 
  border 
  (except 
  

   for 
  the 
  secondary 
  biotite-schist) 
  of 
  the 
  gabbro 
  near 
  the 
  contact, 
  

   and 
  the 
  almost 
  complete 
  absence 
  of 
  quartz 
  from 
  the 
  granite 
  within 
  

   a 
  dozen 
  feet 
  of 
  the 
  main 
  contact. 
  Thus 
  the 
  country 
  rock 
  (granite) 
  

   is 
  distinctly 
  more 
  basic 
  near 
  the 
  contact, 
  while 
  the 
  gabbro 
  is 
  dis- 
  

   tinctly 
  more 
  acidic 
  near 
  the 
  contact. 
  

  

  Whether 
  these 
  interesting 
  endomorphic 
  and 
  exomorphic 
  changes 
  

   are 
  to 
  be 
  accounted 
  for 
  on 
  the 
  basis 
  of 
  assimilation 
  of 
  some 
  of 
  the 
  

   country 
  rock 
  during 
  the 
  intrusion 
  of 
  the 
  gabbro, 
  or 
  on 
  the 
  basis 
  of 
  

   the 
  action 
  of 
  vapors 
  from 
  the 
  intrusive, 
  it 
  at 
  least 
  appears 
  quite 
  

   certain 
  that 
  the 
  gabbro 
  must 
  have 
  been 
  considerably 
  superheated 
  in 
  

   order 
  to 
  have 
  so 
  notably 
  affected 
  the 
  granite. 
  As 
  judged 
  by 
  the 
  

   mode 
  of 
  occurrence 
  of 
  the 
  gabbro 
  stock, 
  the 
  stoping 
  hypothesis 
  

   recently 
  advocated 
  by 
  Daly 
  or 
  the 
  hypothesis 
  of 
  marginal 
  assimila- 
  

   tion 
  might 
  be 
  applied 
  to 
  account 
  for 
  the 
  more 
  acidic 
  border 
  phase 
  

   of 
  the 
  gabbro, 
  but 
  the 
  sharp 
  contact 
  of 
  the 
  gabbro 
  against 
  the 
  granite 
  

   would 
  seem 
  to 
  preclude 
  the 
  possibility 
  of 
  accounting 
  for 
  the 
  more 
  

   basic 
  contact 
  zones 
  of 
  the 
  country 
  rock 
  on 
  the 
  basis 
  of 
  actual 
  assimi- 
  

   lation 
  of 
  some 
  of 
  the 
  granite 
  by 
  the 
  gabbro. 
  

  

  