﻿416 
  MR. 
  T. 
  H. 
  HOLLAND 
  ON 
  A 
  UGITE-DIORITES 
  WITH 
  [ 
  Aug. 
  1 
  897,. 
  

  

  these 
  two 
  minerals 
  would 
  naturally 
  precede 
  the 
  crystallization 
  of 
  

   the 
  more 
  acid 
  residual 
  mother-liquor. 
  But 
  in 
  large 
  boss-like 
  

   masses, 
  where 
  the 
  pressure 
  is 
  greater, 
  and 
  especially 
  in 
  cases 
  where 
  

   the 
  basic 
  material 
  is 
  not 
  in 
  great 
  excess, 
  such 
  a 
  framework 
  would 
  

   be 
  impossible, 
  and 
  as 
  a 
  consequence 
  there 
  would 
  be 
  a 
  more 
  complete 
  

   separation 
  into 
  distinct 
  masses 
  of 
  the 
  two 
  divisions 
  of 
  the 
  magma, 
  

   the 
  first 
  crystallized 
  giving 
  rise 
  to 
  an 
  augite-diorite, 
  while 
  the 
  

   second 
  phase 
  of 
  consolidation 
  would 
  be 
  represented 
  by 
  the 
  formation 
  

   of 
  an 
  acid 
  rock. 
  

  

  The 
  suggestion 
  is 
  thus 
  offered 
  that 
  the 
  gabbros 
  (augite-diorites) 
  

   are 
  genetically 
  related 
  to 
  the 
  granites 
  (granophyres) 
  with 
  which 
  

   they 
  are 
  found 
  associated 
  in 
  the 
  British 
  instances 
  quoted 
  in 
  the 
  

   Introduction 
  (p. 
  406). 
  If 
  this 
  be 
  so, 
  we 
  should 
  expect, 
  as 
  the 
  micro- 
  

   pegmatite 
  is 
  consolidated 
  after 
  the 
  augite 
  and 
  plagioclase 
  in 
  the 
  dyke- 
  

   rocks, 
  so 
  the 
  granophyric 
  rock 
  will, 
  as 
  a 
  rule, 
  be 
  later 
  than 
  its 
  basic 
  

   associate 
  in 
  completing 
  its 
  crystallization. 
  We 
  should 
  expect, 
  

   consequently, 
  to 
  find 
  evidence 
  — 
  and 
  such 
  has 
  been 
  given 
  by 
  Harker 
  

   and 
  others 
  — 
  to 
  show 
  that 
  the 
  basic 
  rock 
  was 
  still 
  hot 
  when 
  the 
  

   acid 
  rock 
  consolidated, 
  veins 
  or 
  junctions 
  of 
  the 
  latter 
  with 
  the 
  

   former 
  being 
  coarse 
  in 
  grain. 
  At 
  the 
  same 
  time, 
  the 
  periods 
  of 
  

   consolidation 
  of 
  the 
  two 
  rocks 
  are 
  sufficiently 
  close 
  to 
  account 
  for 
  

   apparently 
  contradictory 
  phenomena 
  along 
  their 
  line 
  of 
  junction 
  — 
  

   veins 
  of 
  the 
  acid 
  rock 
  in 
  the 
  basic 
  might 
  be 
  converted 
  into 
  isolated 
  

   inclusions 
  by 
  earth-movements, 
  while 
  local 
  re-fusion 
  might 
  be 
  

   caused 
  by 
  the 
  heat 
  resulting 
  frdm 
  mechanical 
  movements. 
  1 
  

  

  The 
  micropegmatite 
  forming, 
  as 
  described, 
  an 
  intricate 
  system 
  of 
  

   veins 
  running 
  through 
  the 
  framework 
  of 
  previously-crystallized 
  

   augite 
  and 
  plagioclase, 
  represents 
  what 
  the 
  older 
  geologists 
  under- 
  

   stood 
  by 
  ' 
  contemporaneous 
  veins,' 
  veins 
  which, 
  though 
  formed 
  after 
  

   sufficient 
  consolidation 
  of 
  the 
  rock 
  penetrated 
  by 
  them, 
  are 
  yet 
  derived 
  

   from 
  the 
  same 
  magma, 
  and 
  form 
  part 
  of 
  one 
  geological 
  unit. 
  

  

  The 
  separation 
  of 
  anhydrous 
  minerals 
  during 
  the 
  early 
  stages 
  of 
  

   consolidation 
  would 
  result 
  in 
  the 
  exclusion 
  of 
  the 
  water 
  originally 
  

   contained 
  in 
  the 
  magma 
  to 
  the 
  mother-liquor. 
  This 
  residual, 
  and 
  

   generally 
  more 
  acid, 
  mother-liquor 
  would 
  thus 
  be 
  in 
  a 
  state 
  of 
  more 
  

   perfect 
  aquo-igneous 
  fusion 
  ; 
  and 
  hence, 
  although 
  the 
  temperature 
  

   may 
  be 
  below 
  that 
  at 
  which 
  the 
  first 
  portions 
  separated, 
  when 
  the 
  

   proportion 
  of 
  water 
  in 
  the 
  magma 
  was 
  lower, 
  it 
  may 
  still 
  be 
  above 
  

   that 
  at 
  which 
  the 
  more 
  aqueous 
  residue 
  would 
  consolidate, 
  and 
  as 
  a 
  

   result 
  the 
  ' 
  contemporaneous 
  veins 
  ' 
  may 
  be 
  as 
  coarse 
  as, 
  and 
  often 
  

   coarser 
  than, 
  the 
  rocks 
  which 
  they 
  penetrate. 
  

  

  x 
  In 
  comparing 
  the 
  intimate 
  admixture 
  of 
  micropegmatite 
  and 
  augite-diorite 
  

   on 
  a 
  microscopic 
  scale 
  with 
  associations 
  of 
  the 
  same 
  rocks 
  in 
  large 
  masses, 
  it 
  is- 
  

   interesting 
  to 
  observe 
  that 
  the 
  changes 
  suffered 
  by 
  the 
  augite, 
  where 
  it 
  abuts 
  

   directly 
  against 
  the 
  micropegmatite, 
  are 
  precisely 
  similar 
  to 
  those 
  noticed 
  by 
  

   Harker 
  in 
  the 
  augite 
  of 
  the 
  Carrock 
  Fell 
  gabbro 
  (augite-diorite) 
  at 
  its 
  junction 
  

   with 
  the 
  granophyric 
  rock, 
  while 
  Sollas 
  has 
  described 
  similar 
  changes 
  in 
  the 
  

   diallage 
  which 
  occurs 
  as 
  xenocrysts 
  in 
  the 
  Carlingford 
  granite 
  (granophyre, 
  in. 
  

   the 
  modified 
  sense 
  suggested 
  by 
  Rosenbusch). 
  

  

  