280  PRE-CAMBRIAN    GEOLOGY   OF    NORTH   AMERICA. 
there  are  large  areas  in  which  eruptive  masses  of  granite  and  gneiss 
have  penetrated  the  Huronian  rocks,  and  thrown  them  into  folds, 
proving  their  later  age,  in  general  the  reverse  is  the  case,  the  Huron- 
ian resting  unconformably  upon  the  Laurentian  and  being  of  later 
origin.  The  Huronian  is  overlain  unconformably  by  Cambrian  rocks, 
under  the  Cambrian  being  included  Animikie,  Nipigon,  and  Potsdam 
rocks. 
Coleman,2""'  in  1896,  makes  a  second  report  on  the  gold  fields  of 
western  Ontario,  including  the  area  between  Finmark,  near  Thunder 
Bay,  and  the  Manitoba  boundary,  and  between  Minnesota  and  Kee- 
watin,  on  the  north  shore  of  Lonely  Lake.  This  visit  confirms  his 
impressions  of  the  geology  of  the  area  as  given  in  the  preceding 
report  of  the  bureau. 
At  many  places  the  Laurentian  rocks  exhibit  an  eruptive  contact 
with  the  overlying  rocks,  showing  that  they  must  have  been  consoli- 
dated later  than  the  Huronian.  Coleman  suggests  that  it  would  be 
more  logical  to  confine  the  name  Laurentian  to  the  oldest  complex  of 
thoroughly  crystalline  rocks  serving  as  a  foundation  for  all  succeed- 
ing rocks,  and  to  describe  the  clearly  eruptive  rocks  which  penetrate 
the  overlying  Huronian  schists  as  erupt  ives,  of  later  age  than  at  least 
the  earlier  members  of  the  Huronian.  If  this  were  done,  very  little  of 
the  territory  under  consideration  could  be  mapped  as  Laurentian; 
perhaps  none  of  it  with  certainty.  However,  the  discrimination  may 
not  be  made  until  more  detailed  work  has  been  done  in  the  district. 
Coutchiching  mica  schists  and  gneisses,  though  probably  present, 
have  not  been  certainly  recognized.  The  series  of  erupt  ives,  pyro- 
clastics,  and  less  common  waterworn  elastics,  Lawson's  Keewatin,  is 
of  widespread  occurrence,  and  of  great  importance  as  containing  the 
gold-bearing  veins  of  the  district.*  It  is  spoken  of  under  the  general 
term  Huronian. 
Coleman,200  in  1896,  describes  the  anorthosite  of  the  Rainy  Lake 
region.  The  granite  found  adjacent  to  the  anorthosite  in  the  neigh- 
borhood of  Bad  Vermilion  Lake  is  of  considerably  later  age  than  the 
anorthosite.  A  schist  conglomerate  containing  fragments  of  the  lat- 
ter is  found  to  be  intruded  by  the  granite. 
Lawson,207  in  1896,  describes  a  family  of  basic  plutonic  orthoclase 
rocks  rich  in  alkalies  and  lime,  which  he  names  malignite,  as  occur- 
ring in  the  form  of  a  laccolith  in  the  Coutchiching  schists  of  Poohbah 
Lake.  The  malignites  vary  from  basic  nepheline-pyroxene  malignite 
through  garnet-pyroxene  malignite  to  amphibole  malignite. 
Coleman,208  in  1897,  makes  a  third  report  on  the  gold  region  of 
western  Ontario.  The  districts  visited  and  here  reported  on  are  the 
.Upper  Seine  district,  the  Shoal  Lake  district,  the  Manitou  district, 
the  country  crossed  between  Manitou  Lake  and  the  Lake  of  the  Woods, 
the  Lake  of  the  Woods  district,  the  West  Shoal  Lake  district,  the 
