428  PRE-CAMBBIAN    GEOLOGY    OF    NORTH    AMERICA. 
netite  associated  with  amphibole  and  epidote  occurs  in  bands  and 
lenses  in  a  complex  of  basic  igneous  rocks  characterized  by  uniform 
abundance  of  amphiboles.  Some  of  the  greenstones  are  basal  and 
some  are  intrusive  into  the  iron-bearing  bands.  Intrusive  into  the 
greenstone  and  probably  into  the  iron  formation  are  granite  masses. 
Closely  associated  with  the  iron  formation,  but  with  relations  un- 
known, is  a  pyritiferous  graywacke.  The  ores  and  associated  rock 
as  a  whole  are  in  general  similar  lithologically  to  the  Vermilion  iron- 
bearing  district  of  Minnesota,  although  showing  many  points  of  dif- 
ference. 
Bolton,51  in  1903,  reports  on  a  geological  reconnaissance  from 
Round  Lake  north  to  the  Abitibi  River  in  the  district  of  Nipissing. 
Laurentian  granite  was  seen  near  both  the  southeastern  and  the  south- 
western corners  of  Eby.  Elsewhere  Huronian  rocks  are  exposed. 
Of  these  there  is  a  considerable  variety,  many  of  which  are  of  frag- 
mental  origin.  The  following  types  were  seen :  Diorite,  diabase, 
brecciated  conglomerate,  slate,  graywacke,  hornblende  schist,  etc.  As 
the  rock  outcrops  of  the  district  explored  are  as  a  rule  separated  by 
areas  of  sand  or  swampy  or  clayey  soil,  the  relations  of  the  different 
types  could  seldom  be  worked  out. 
Graton,52  in  1903,  reports  on  a  geological  reconnaissance  along 
Mississaga  River,  and  east  and  west  along  Niven's  base  line,  in  the 
district  of  Algoma.  Laurentian  granites  occupy  all  of  the  area  north 
of  Township  188,  where  was  found  a  greenish  slate  conglomerate  be- 
longing to  the  Huronian. 
Van  Hise,  Leith,53  and  assistants,  in  1903,  by  an  examination  of 
the  area  westward  from  Lake  Temagami  to  the  Onaping  River,  find 
that  the  basement  rocks  of  the  region  are  greenstones  and  green 
schists,  with  associated  iron  formation,  similar  in  all  respects  to  the 
Keewatin  (Archean)  greenstones,  green  schists,  and  iron  forma- 
tion of  the  Vermilion  and  Marquette  iron-bearing  districts  of  Minne- 
sota and  Michigan.  Intrusive  into  these  rocks  are  granites  of  two  or 
more  ages,  a  considerable  part  of  which  are  Laurentian.  Uncon- 
formable overlying  the  greenstones,  green  schists,  and  iron  forma- 
tion, and  at  least  part  of  the  granites,  are  two  or  more  unconforma- 
ble series  of  Huronian  sediments,  including  conglomerate,  quartzite, 
slate,  and  limestone,  for  the  most  part  not  greatly  metamorphosed  or 
folded.  Unconformable  contacts  with  the  Keewatin  were  noted  be- 
tween the  sediments  and  basal  rocks  on  Emerald  Lake  and  west  of 
Morin  Lake,  north  of  the  township  of  Kitchener,  and  contacts  of  the 
Huronian  and  Laurentian  were  noted  on  Rabbit  Lake,  west  of  Morin 
Lake,  and  on  Onaping  Lake.  Contacts  between  the  upper  and  lower 
sedimentary  Huronian  series  were  found  on  Temagami  and  Emerald 
lakes  and  at  several  localities  west  of  Hutton.  The  general  outlines 
of  the  igneous  and  sedimentary  series  were  determined  for  an  area 
