﻿REPORT 
  OF 
  THE 
  DIRECTOR 
  1912 
  IOI 
  

  

  anorthosite, 
  or 
  have 
  been 
  folded 
  into 
  the 
  latter 
  and 
  metamor- 
  

   phosed." 
  

  

  From 
  these 
  statements 
  we 
  see 
  that 
  three 
  possible 
  modes 
  of 
  origin 
  

   of 
  these 
  garnet-bearing 
  beds 
  have 
  been 
  suggested, 
  namely 
  that 
  they 
  

   are: 
  lenses 
  of 
  sedimentary, 
  rock 
  actually 
  included 
  in 
  the 
  igneous 
  

   rock; 
  or 
  sediments 
  folded 
  into 
  the 
  igneous 
  rock 
  and 
  metamor- 
  

   phosed; 
  or 
  sheets 
  or 
  dikes 
  of 
  very 
  basic 
  igneous 
  rock. 
  Now 
  the 
  

   work 
  of 
  the 
  writer 
  shows 
  that, 
  without 
  question, 
  these 
  garnets 
  

   occur 
  in 
  lenses 
  of 
  Grenville 
  sediments 
  which 
  were 
  caught 
  up 
  or 
  

   included 
  in 
  the 
  great 
  igneous 
  masses 
  at 
  the 
  time 
  of 
  their 
  intrusion, 
  

   the 
  tremendous 
  heat 
  and 
  pressure 
  being 
  especially 
  favorable 
  for 
  a 
  

   very 
  complete 
  rearrangement 
  and 
  crystallization 
  of 
  the 
  masses 
  (in- 
  

   clusions) 
  of 
  sediment 
  which 
  were 
  pretty 
  low 
  in 
  silica. 
  These 
  in- 
  

   clusions 
  are 
  portions 
  of 
  a 
  great 
  thickness 
  of 
  hornblende-garnet 
  

   gneiss, 
  frequently 
  interbedded 
  with 
  limestone, 
  of 
  the 
  Grenville 
  

   series. 
  This 
  gneiss 
  is 
  a 
  basic 
  rock 
  generally 
  carrying 
  several 
  per 
  

   cent 
  of 
  magnetite 
  ; 
  sometimes 
  considerable 
  hypersthene 
  ; 
  and 
  little 
  or 
  

   no 
  quartz. 
  It 
  is 
  quite 
  likely 
  that 
  some 
  of 
  the 
  closely 
  involved 
  lime- 
  

   stone 
  was 
  mixed 
  with 
  the 
  inclusions 
  of 
  sediment 
  during 
  the 
  process 
  

   of 
  metamorphism. 
  It 
  will 
  at 
  once 
  be 
  seen 
  that 
  such 
  an 
  iron-rich, 
  

   silica-poor 
  sediment 
  was 
  very 
  favorable 
  for 
  the 
  development 
  of 
  

   large 
  garnets 
  under 
  the 
  conditions 
  of 
  great 
  heat 
  and 
  pressure 
  which 
  

   were 
  brought 
  to 
  bear 
  upon 
  the 
  lenslike 
  inclusions 
  in 
  the 
  molten 
  

   syenite 
  or 
  granite. 
  

  

  The 
  hornblende 
  rims 
  or 
  envelops 
  are 
  quite 
  certainly 
  great 
  reaction 
  

   rims 
  around 
  the 
  garnets, 
  but 
  just 
  at 
  what 
  stage 
  of 
  the 
  metamorphism 
  

   they 
  were 
  produced 
  is 
  not 
  at 
  all 
  clear 
  to 
  the 
  writer. 
  The 
  rounded 
  

   character 
  of 
  the 
  garnets 
  shows 
  pretty 
  clearly 
  that 
  the* 
  rims 
  of 
  horn- 
  

   blende 
  are 
  of 
  secondary 
  origin 
  and 
  that 
  they 
  were 
  formed 
  some- 
  

   time 
  after 
  the 
  crystallization 
  of 
  the 
  garnets 
  and 
  possibly 
  at 
  the 
  

   time 
  when 
  the 
  pressure 
  producing 
  the 
  foliation 
  of 
  the 
  rocks 
  of 
  the 
  

   region 
  was 
  brought 
  to 
  bear. 
  

  

  In 
  case 
  number 
  4 
  (Hooper 
  mine) 
  a 
  clew 
  to 
  the 
  origin 
  of 
  the 
  

   garnets 
  is 
  furnished 
  by 
  a 
  study 
  of 
  the 
  wall 
  rock 
  in 
  the 
  Rogers 
  

   mine 
  on 
  Gore 
  mountain. 
  In 
  this 
  latter 
  case 
  the 
  typical 
  garnet- 
  

   bearing 
  rock 
  (No. 
  1 
  of 
  the 
  accompanying 
  table) 
  of 
  the 
  mine 
  passes 
  

   by 
  perfect 
  gradation, 
  through 
  an 
  eight 
  or 
  ten 
  foot 
  zone, 
  into 
  

   a 
  basic 
  syenite 
  or 
  acidic 
  diorite 
  (No. 
  2 
  of 
  the 
  table) 
  which 
  contains 
  

   distinct 
  dodecahedral 
  garnet 
  crystals 
  up 
  to 
  over 
  an 
  inch 
  across 
  but 
  

   always 
  without 
  hornblende 
  rims. 
  This 
  rock, 
  in 
  turn, 
  grades 
  into 
  

   a 
  hornblende 
  (quartzless) 
  syenite 
  (No. 
  3 
  of 
  the 
  table) 
  which 
  merges 
  

   into 
  the 
  typical 
  country 
  rock 
  of 
  quartz, 
  hornblende 
  syenite, 
  these 
  

  

  