﻿22 
  FEDDEN 
  : 
  GEOLOGY 
  OF 
  KATHIAWAR 
  PENINSULA 
  IN 
  GUZERAT. 
  

  

  The 
  Gfrnar 
  appears 
  to 
  have 
  been 
  produced 
  by 
  a 
  volcanic 
  eruption 
  of 
  

   considerable 
  magnitude 
  towards 
  the 
  close 
  of 
  the 
  Deccan-trap 
  period; 
  

   and 
  the 
  mountain, 
  in 
  its 
  entirety, 
  must 
  have 
  attained 
  vast 
  proportions 
  in 
  

   comparison 
  with 
  its 
  present 
  denuded 
  appearance. 
  The 
  great 
  central 
  

   mass 
  now 
  represents 
  so 
  much 
  of 
  the 
  core, 
  or 
  plug, 
  of 
  the 
  vent, 
  the 
  outer 
  

   portion 
  having 
  been 
  more 
  readily 
  removed 
  by 
  denudation, 
  owing 
  to 
  the 
  

   decomposition 
  of 
  the 
  component 
  minerals. 
  

  

  The 
  diorite 
  of 
  this 
  central 
  peak 
  has 
  not 
  been 
  found 
  in 
  any 
  other 
  

   Diorite 
  of 
  central 
  place 
  in 
  Kathiawar; 
  nor, 
  as 
  far 
  as 
  I 
  am 
  aware, 
  in 
  

   P 
  eak 
  - 
  any 
  part 
  of 
  Peninsular 
  India. 
  Its 
  normal 
  form 
  is 
  

  

  a 
  black 
  and 
  white 
  crystalline-granular 
  rock 
  of 
  hornblende 
  and 
  felspar 
  ; 
  it 
  

   has 
  much 
  the 
  appearance 
  of 
  syenite, 
  but 
  the 
  felspar 
  is 
  almost 
  entirely 
  

   plagioclastic. 
  This 
  rock 
  passes 
  into 
  micadiorite 
  where 
  it 
  contains 
  black 
  

   uni-axial 
  mica 
  more 
  or 
  less 
  abundantly, 
  not 
  unf 
  requently 
  in 
  tabular 
  segre- 
  

   gations, 
  enclosing 
  felspar. 
  Some 
  portions 
  of 
  this 
  rock 
  are 
  richer 
  in 
  

   felspar, 
  with 
  chatoiyant 
  blue 
  lustre, 
  and 
  more 
  coarsely 
  crystalline. 
  

   Microscopic 
  sections 
  of 
  the 
  rock 
  display 
  magnetic 
  iron, 
  apatite, 
  and 
  

   garnets 
  occasionally. 
  Other 
  portions 
  are 
  minutely 
  crystalline, 
  or 
  even 
  

   aphanitic. 
  

  

  In 
  the 
  basal 
  and 
  outer 
  portion 
  of 
  the 
  central 
  pile 
  two 
  marked 
  va- 
  

   rieties 
  of 
  the 
  diorite 
  are 
  prevalent. 
  The 
  most 
  con- 
  

  

  Diorite 
  of 
  two 
  kinds. 
  . 
  . 
  ...... 
  

  

  spicuous 
  is 
  a 
  light 
  grey 
  semi-aphanitic 
  diorite, 
  

   with 
  porphyritic 
  crystals 
  of 
  felspar, 
  and 
  some 
  bi-axial 
  mica 
  sparingly 
  ; 
  

   in 
  this 
  variety 
  hornblende 
  is 
  extremely 
  deficient. 
  The 
  other 
  variety 
  

   is 
  of 
  a 
  dark 
  grey 
  or 
  black 
  colour, 
  from 
  its 
  richness 
  in 
  hornblende, 
  and 
  

   is 
  often 
  seen 
  intermingled 
  and 
  banded 
  with 
  the 
  paler 
  rock, 
  with 
  which 
  it 
  

   affords 
  a 
  very 
  striking 
  contrast. 
  

  

  <{ 
  From 
  the 
  strongly 
  marked 
  line 
  of 
  demarcation 
  which 
  often 
  separates 
  

   these 
  two 
  varieties 
  in 
  the 
  same 
  rock, 
  it 
  might 
  be 
  presumed 
  that 
  one 
  was 
  

   of 
  later 
  date 
  than 
  the 
  other, 
  and 
  had 
  penetrated 
  it 
  subsequently 
  to 
  its 
  

   consolidation; 
  especially 
  as 
  many 
  of 
  what 
  appear 
  like 
  included 
  frag- 
  

   ments 
  of 
  the 
  older, 
  have 
  a 
  very 
  angular 
  and 
  irregular 
  outline. 
  But 
  this 
  

   appearance 
  is 
  in 
  reality 
  deceptive, 
  the 
  pale 
  variety 
  being 
  found 
  enclosing 
  

   lumps, 
  sheets, 
  and 
  strings 
  of 
  the 
  dark 
  kind, 
  and 
  vice 
  versa, 
  thereby 
  con- 
  

   ( 
  94 
  ) 
  

  

  