﻿36 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Contact 
  phenomena 
  

  

  A 
  very 
  interesting 
  case 
  of 
  contact 
  metamorphism 
  produced 
  by 
  

   the 
  action 
  of 
  the 
  gabbro 
  on 
  granite 
  may 
  be 
  seen 
  at 
  the 
  southern 
  

   end 
  of 
  the 
  large 
  stock 
  just 
  south 
  of 
  Mountain 
  Spring 
  lake. 
  In 
  a 
  

   recently 
  opened 
  stone 
  quarry, 
  and 
  about 
  75 
  feet 
  higher 
  than 
  the 
  road 
  

   on 
  its 
  east 
  side, 
  the 
  rocks 
  are 
  laid 
  bare 
  in 
  such 
  a 
  manner 
  that 
  an 
  

   excellent 
  opportunity 
  is 
  afforded 
  for 
  the 
  study 
  of 
  the 
  contact 
  zones. 
  

   The 
  following 
  nine 
  zones, 
  passing 
  from 
  the 
  typical 
  gabbro 
  to 
  the 
  

   typical 
  granite 
  (country 
  rock), 
  have 
  been 
  studied 
  in 
  detail 
  in 
  the 
  

   field 
  and 
  by 
  means 
  of 
  thin 
  sections 
  and 
  hand 
  specimens. 
  

  

  Zone 
  1 
  Typical 
  gabbro 
  well 
  within 
  the 
  gabbro 
  stock. 
  Nearly 
  black, 
  

   medium 
  grained, 
  and 
  with 
  diabasic 
  texture. 
  (Gradation 
  

   from 
  1 
  to 
  2) 
  

  

  Zone 
  2 
  Syenitic 
  phase 
  of 
  gabbro 
  stock 
  and 
  within 
  a 
  few 
  feet 
  of 
  the 
  

   granite. 
  Dark 
  gray, 
  medium 
  grained, 
  and 
  with 
  granitoid 
  

   texture. 
  (Gradation 
  from 
  2 
  to 
  3) 
  

  

  Zone 
  3 
  One 
  to 
  three 
  feet 
  wide. 
  Biotite-schist 
  border 
  phase 
  of 
  the 
  

   gabbro 
  stock. 
  Secondary 
  origin. 
  (Sharp 
  contact 
  between 
  

   3 
  and 
  4, 
  gabbro 
  and 
  granite) 
  

  

  Zone 
  4 
  Four 
  inches 
  wide. 
  Hornblendite 
  phase 
  of 
  the 
  country 
  rock. 
  

   Nearly 
  black, 
  medium 
  grained, 
  banded 
  parallel 
  to 
  gabbro- 
  

   granite 
  contact. 
  (Fairly 
  sharp 
  contact 
  between 
  4 
  and 
  5) 
  

  

  Zone 
  5 
  Six 
  inches 
  wide. 
  Monzonitic 
  phase 
  of 
  the 
  country 
  rock. 
  

   Yellowish 
  gray, 
  medium 
  to 
  coarse 
  grained, 
  and 
  banded 
  

   parallel 
  to 
  the 
  main 
  contact. 
  (Not 
  very 
  sharp 
  contact 
  

   between 
  5 
  and 
  6) 
  

  

  Zone 
  6 
  Fifteen 
  to 
  eighteen 
  inches 
  wide. 
  Chiefly 
  hornblendite 
  phase 
  

   of 
  the 
  country 
  rock 
  but 
  with 
  numerous 
  very 
  narrow 
  

   streaks 
  of 
  no. 
  5. 
  Nearly 
  black, 
  medium 
  grained, 
  and 
  

   banded 
  parallel 
  to 
  the 
  main 
  contact. 
  (Sharp 
  contact 
  be- 
  

   tween 
  6 
  and 
  7) 
  

  

  Zone 
  7 
  Three 
  and 
  one-third 
  feet 
  wide. 
  Monzonitic 
  phase 
  of 
  the 
  

   country 
  rock 
  like 
  no. 
  5. 
  Yellowish 
  gray, 
  fairly 
  coarse 
  

   grained, 
  and 
  banded 
  parallel 
  to 
  the 
  main 
  contact. 
  (Not 
  

   very 
  sharp 
  contact 
  between 
  7 
  and 
  8) 
  

  

  Zone 
  8 
  Seven 
  feet 
  wide. 
  Monzonitic 
  phase 
  of 
  the 
  country 
  rock. 
  

   Light 
  gray, 
  fairly 
  coarse 
  grained, 
  and 
  not 
  banded. 
  (Gra- 
  

   dation 
  from 
  8 
  to 
  9) 
  

  

  Zone 
  9 
  Typical 
  (country 
  rock) 
  granite. 
  Pink, 
  medium 
  grained, 
  and 
  

   very 
  gneissoid 
  but 
  with 
  gneissic 
  bands 
  striking 
  at 
  almost 
  

   right 
  angles 
  to 
  the 
  main 
  contact. 
  

  

  