watson.]  THE    SEMINOLE    COPPER    DEPOSIT    OF    GEORGIA.  185 
the  Magruder  vein,  but  it  is  abundantly  concentrated  in  the  form  of 
ore  shoots  in  the  Wardlow  and  in  the  Finley. 
At  the  185-foot  level  and  below  the  veins  are  perfectly  tight  and  dry, 
but  a  free  percolation  of  surface  waters  downward  takes  place  through 
the  crushed  and  fractured  country  rock. 
STRUCTURAL  FEATURES. 
The  veins  occur  in  an  area  in  which  the  rocks  are  profoundly  altered 
and,  accordingly,  covered  to  some  depth  by  the  products  of  residual 
decay,  hence  outcrops  of  the  fresh  or  moderately  fresh  rocks  are  rare. 
Alteration  extends  to  the  entire  depth  of  working,  about  200  feet. 
The  rocks  are  further  extensively  crushed  and  fractured,  and  are  trav- 
ersed by  a  multiplicity  of  joints  and  intruded  dikes  of  altered  basic 
igneous  rocks — probably  diorite  or  diabase,  or  both.  As  a  result  of  the 
action  of  intense  dynamic  forces  the  rocks  are,  moreover,  rendered  com- 
pletely and  thinly  schistose,  the  planes  of  schistosity  showing  a  general 
northeast-southwest  strike,  with  wide  local  variation  in  places.  Both 
the  dikes  and  country  rock  are,  in  general,  strongly  mineralized. 
So  far  as  it  was  possible  to  interpret  the  conditions,  the  veins  are 
developed  along  and  in  a  shear  zone,  which  approximates  a  northeast- 
southwest  direction,  possibly  a  few  degrees  north  of  east  of  the  strike 
of  the  schistosity.  Clearly  the  conditions  were  entirely  favorable  to  the 
free  circulation  of  mineralizing  solutions,  which  were  more  concen- 
trated along  certain  definite  lines  within  the  shear  zone,  determining  the 
position  of  the  present  veins.  While  the  thin  sections  of  the  rocks  have 
not  yet  been  studied  sufficiently  to  warrant  definite  statement,  the 
general  character  of  the  veins  in  the  underground  workings  afford 
some  suggestion  of  metasomatic  action  or  replacement. 
The  veins  are  cut  across  by  some  of  the  dikes  of  basic  rocks,  but 
enrichment,  so  far  as  could  be  determined,  seems  not  more  character- 
istic near  or  at  the  contacts  with  the  dikes  than  at  some  distance  away. 
Moreover,  it  is  impossible  to  state  whether  secondary  enrichment  has 
taken  place  or  not.  The  veins  do  not  conform  entirely  with  the  direc- 
tion of  schistosity,  but  they  cut  it  at  very  slight  angles;  and  the  schis- 
tosity is  likewise  cut  across  by  the  shear  zone  at  angles  varying  from 
7°  to  15°,  a  circumstance  which  results  at  times  in  a  step-like  arrange- 
ment in  the  veins.  In  a  general  way,  however,  the  veins  follow  more 
or  less  closely  both  the  shearing  and  the  schistosity. 
From  the  available  field  evidence  the  order  of  events,  so  far  as  it  has 
been  possible  to  interpret  them,  are,  in  general,  as  follows:  An  early 
period  of  intense  dynamic  disturbance  caused  extensive  crushing  and 
fracturing  of  the  country  rocks,  resulting  in  secondary  structure. 
This  was  followed  by  silicincation  and  mineralization  concentrated 
along  fairly  well-defined,  roughly  parallel  lines  marking  the  present 
veins.     A  second  period  of  disturbance  resulted  in  the  intrusion  of  the 
