﻿136 
  

  

  Geological 
  Society 
  : 
  — 
  

  

  amphibolite, 
  and 
  within 
  these 
  smaller 
  bands 
  of 
  crystalline 
  lime- 
  

   stone 
  are 
  sometimes 
  preserved. 
  In 
  many 
  places 
  the 
  gneisses 
  

   become 
  garnetiferous, 
  while 
  eclogites 
  and 
  basic 
  granulites 
  also 
  

   occur. 
  Schists 
  — 
  referable 
  to 
  arenaceous 
  sediments 
  — 
  are 
  found 
  

   only 
  near 
  the 
  coast, 
  where 
  they 
  are 
  interbanded 
  with 
  gneisses 
  ; 
  

   and, 
  as 
  the 
  latter 
  are 
  mainly 
  of 
  igneous 
  origin, 
  they 
  are 
  thought 
  

   to 
  be 
  intrusive 
  into, 
  and 
  therefore 
  younger 
  than, 
  the 
  schists. 
  As 
  

   a 
  general 
  rule, 
  the 
  foliation 
  and 
  the 
  banding 
  of 
  the 
  gneisses 
  are 
  

   well 
  defined 
  in 
  parallel 
  uncontorted 
  planes, 
  the 
  strike 
  being 
  com- 
  

   monly 
  along, 
  or 
  somewhat 
  north 
  of, 
  a 
  north-east 
  to 
  south-west 
  

   direction. 
  In 
  certain 
  inselberg 
  peaks, 
  the 
  strike 
  sweeps 
  round 
  

   the 
  contours, 
  while 
  the 
  foliation-surfaces 
  dip 
  quaquaversally 
  from 
  

   the 
  summits. 
  Into 
  the 
  gneisses 
  later 
  granites, 
  belonging 
  to 
  at 
  

   least 
  two 
  different 
  periods, 
  have 
  penetrated, 
  riddling 
  them 
  with 
  

   enormous 
  numbers 
  of 
  small 
  intrusions, 
  lit-par-lit 
  injections, 
  

   tongues, 
  and 
  apophyses. 
  Rocks 
  of 
  later 
  age 
  are 
  rarely 
  met 
  with 
  ; 
  

   but, 
  in 
  a 
  few 
  places, 
  dykes 
  of 
  picrite 
  and 
  pyroxenite 
  have 
  been 
  

   found 
  cutting 
  the 
  youngest 
  pegmatites. 
  

  

  The 
  succession 
  of 
  rocks 
  in 
  eight 
  of 
  the 
  better-known 
  districts 
  is 
  

   described, 
  and 
  the 
  following 
  general 
  classification 
  is 
  based 
  on 
  the 
  

   details 
  thus 
  provided 
  : 
  — 
  

  

  Ultrabasic 
  f 
  Pyroxenites. 
  

   Dykes. 
  \ 
  Picrite. 
  

  

  Intrusive 
  Contact. 
  

  

  Granites 
  and 
  f 
  Biotite-Granites. 
  

  

  Coarse 
  < 
  Graphic 
  Granite 
  and 
  other 
  Pegmatites. 
  

   Pegmatites. 
  [ 
  Quartz-Veins. 
  

  

  Age 
  unknown. 
  

  

  Pre-Cretaceous 
  

   and 
  Post- 
  Middle 
  

   Pre 
  -Cambrian. 
  

  

  Granulitic 
  

  

  Granites, 
  

  

  Pegmatites, 
  

  

  and 
  Associated 
  

  

  Rocks. 
  

  

  Intrusive 
  Contact. 
  

  

  ( 
  Biotite-Granites 
  (including 
  porphyritic 
  "^ 
  

  

  varieties). 
  

   ! 
  Pegmatites 
  and 
  Aplites. 
  

   Pyroxene- 
  Granite 
  and 
  Pyroxene 
  Quartz- 
  

  

  Diorite 
  Series. 
  

   Pyroxene-Granulites 
  ? 
  / 
  

  

  Middle 
  

   Pre- 
  Cambrian. 
  

   Pb/U=0-14 
  to 
  

  

  0-17. 
  

  

  Intrusive 
  Contact. 
  

  

  Gneisses 
  

  

  and 
  

  

  Associated 
  

  

  Rocks. 
  

  

  Crystalline 
  

   Schists 
  and 
  

   Limestones. 
  

  

  fBiotite- 
  Gneisses 
  and 
  

   j 
  Gneissose 
  Granites. 
  

   Hornblende- 
  Gneisses 
  

  

  Amphibolites. 
  

   Garnetiferous 
  Gneisses, 
  

  

  (^Granulites, 
  and 
  Eclogites. 
  

  

  Intrusive 
  Contact. 
  

  

  ( 
  Quartz-Mica-Schists. 
  

   | 
  Quartz-Magnetite-Schists. 
  

   j 
  Hornblende-Garnet-Schists. 
  

   ] 
  Haematite-Schists. 
  

  

  j 
  Forsterite-Marbles, 
  and 
  other 
  

   ^ 
  Crystalline 
  Limestones. 
  

  

  Pb/U 
  = 
  0-21. 
  

  

  Lower 
  

   Pre-Cambrian. 
  

  

  