﻿270 
  Lindgren 
  — 
  Granodiorite 
  and 
  other 
  intermediate 
  rocks. 
  

  

  Nevada. 
  The 
  series 
  also 
  included 
  a 
  variety 
  carrying 
  large 
  

   orthoclase 
  crystals, 
  and 
  extensively 
  developed 
  in 
  Tuolumne 
  

   County. 
  The 
  result 
  showed 
  that 
  all 
  these 
  rocks 
  were 
  charac- 
  

   terized 
  by 
  about 
  the 
  same 
  amount 
  of 
  quartz 
  and 
  that 
  in 
  all 
  of 
  

   them 
  the 
  soda-lime 
  feldspar 
  (andesine 
  or 
  oligoclase) 
  greatly 
  pre- 
  

   dominated 
  over 
  the 
  alkali 
  feldspars, 
  both 
  always 
  being 
  present. 
  

   A 
  great 
  number 
  of 
  slides 
  had 
  been 
  examined, 
  but 
  at 
  that 
  

   time 
  (in 
  1891) 
  the 
  analytical 
  data 
  were 
  less 
  complete 
  than 
  

   might 
  have 
  been 
  desired. 
  The 
  first 
  analysis 
  considered 
  as 
  rep- 
  

   resenting 
  the 
  composition 
  of 
  granodiorite 
  was 
  the 
  one 
  pub- 
  

   lished 
  by 
  Mr. 
  Clarence 
  King 
  in 
  the 
  volumes 
  of 
  the 
  " 
  Explora- 
  

   tion 
  of 
  the 
  40th 
  Parallel," 
  the 
  locality 
  being 
  El 
  Capitan. 
  

   Yosemite 
  Valley. 
  This 
  analysis 
  runs 
  as 
  follows 
  : 
  

  

  SiG 
  2 
  66-40 
  

  

  A1 
  2 
  3 
  17-13 
  

  

  FeO 
  _. 
  3*77 
  

  

  MnO 
  _.. 
  -30 
  

  

  CaO 
  4*05 
  

  

  MgO 
  . 
  -97 
  

  

  K 
  2 
  2-08 
  

  

  Na 
  2 
  4-49 
  

  

  Ignition 
  _ 
  1 
  03 
  

  

  100-22 
  

  

  For 
  the 
  rock 
  described 
  above 
  the 
  name 
  of 
  granodiorite 
  was 
  

   proposed, 
  the 
  term 
  being 
  suggested 
  by 
  Mr. 
  G. 
  F. 
  Becker. 
  The 
  

   name 
  was 
  intended 
  to 
  cover 
  intermediate 
  acid 
  rocks 
  which 
  

   were 
  more 
  closely 
  related 
  to 
  a 
  quartz-diorite 
  than 
  to 
  a 
  granite, 
  

   but 
  was 
  not 
  proposed 
  as 
  a 
  synonym 
  for 
  quartz-mica-diorite. 
  

  

  Further 
  definitions. 
  — 
  In 
  the 
  text 
  to 
  the 
  older 
  folios 
  of 
  the 
  

   gold 
  belt 
  the 
  term 
  granodiorite 
  is 
  defined 
  as 
  follows 
  (Sacra- 
  

   mento 
  Folio, 
  !No. 
  5, 
  1894) 
  : 
  It 
  should 
  be 
  remembered 
  that 
  

   these 
  brief 
  descriptions 
  are 
  chiefly 
  intended 
  for 
  the 
  non-tech- 
  

   nical 
  reader. 
  

  

  " 
  Granodiorite 
  (quartz-mica-diorite). 
  — 
  A 
  granular 
  intrusive 
  

   rock 
  having 
  the 
  habitus 
  of 
  granite 
  and 
  carrying 
  feldspar, 
  

   quartz, 
  biotite, 
  and 
  hornblende. 
  The 
  soda-lime 
  feldspars 
  are 
  

   usually 
  considerably 
  and 
  to 
  a 
  variable 
  extent 
  in 
  excess 
  of 
  the 
  

   alkali 
  feldspars. 
  This 
  granitic 
  rock 
  might 
  be 
  called 
  quartz- 
  

   mica-diorite, 
  but 
  this 
  term, 
  besides 
  being 
  awkward, 
  does 
  not 
  

   sufficiently 
  suggest 
  its 
  close 
  relationship 
  with 
  granite 
  ; 
  it 
  has, 
  

   therefore, 
  been 
  decided 
  to 
  name 
  it 
  granodiorite. 
  

  

  In 
  the 
  later 
  folios 
  (Truckee 
  No. 
  39, 
  1897) 
  the 
  definition 
  is 
  

   slightly 
  altered 
  in 
  form 
  and 
  reads 
  as 
  follows 
  : 
  

  

  " 
  Granodiorite. 
  — 
  A 
  granular 
  intrusive 
  rock 
  having 
  the 
  

   habitus 
  of 
  granite 
  and 
  carrying 
  feldspar, 
  quartz, 
  biotite 
  and 
  

  

  