422    ■  PRE-CAMBRIAN    GEOLOGY   OF    NORTH    AMERICA. 
rocks  do  not  form  a  large  proportion  of  the  Huronian  series  in  this 
district. 
Impure  magnesium  limestones  occur  in  the  northern  part  of  the 
Bay  of  Islands,  in  the  northwestern  part  of  the  township  of  Ruther- 
ford, and  north  of  the  area  of  the  sheet,  near  Lake  Panache. 
Between  the  Huronian  rocks  on  the  north  and  the  Laurentian  rocks 
on  the  southeast  there  is  a  belt  of  red  granite,  the  Killarney  belt, 
running  from  Badgely  Island  to  Threemile  Lake.  This  granite  is 
apparently  of  eruptive  origin  and  of  later  age  than  the  quartzites. 
All  along  the  line  of  contact  with  the  Huronian  the  rocks  give  evi- 
dence of  great  disturbance.  Huge  portions,  as  well  as  many  of 
moderate  size,  have  been  separated  from  both  sides  and  have  been 
mingled  together  and  intermixed  with  finer  debris,  all  being  cemented 
into  a  coarse  breccia. 
The  southeastern  side  of  the  Killarney  belt  of  granite  rests  against 
the  Laurentian  gneiss,  except  in  the  interval  from  the  southern  point 
of  George  Island  to  the  entrance  of  Collins  Inlet,  where  a  narrow  belt 
of  partially  altered,  fine-grained,  brittle,  red  and  sometimes  gray 
quartzite  intervenes  between  the  granite  and  the  water  of  Georgian 
Bay.  Farther  northeastward,  or  where  the  granite  of  the  Killarney 
belt  comes  in  contact  with  the  gneiss  which  prevails  to  the  east,  it 
is  not  always  separated  from  the  latter  by  a  very  distinct  boundary. 
The  rocks  in  some  places  pass  into  each  other  more  or  less  gradually. 
Burwash,40  in  1897,  during  the  survey  of  the  boundary  line  be- 
tween the  districts  of  Nipissing  and  Algoma  in  Canada,  takes 
geological  notes  of  the  area  traversed. 
The  run  was  made  from  south  to  north,  from  the  upper  waters  of 
the  Vermilion  and  \Yahnipitae  rivers  to  within  35  miles  of  Lake 
Abittibi,  and,  with  the  exception  of  two  areas  of  eruptive  granite, 
the  country  was  found  to  be  underlain  for  the  entire  distance  by 
Huronian  rocks.    The  section  is  given  in  detail. 
Walker,41  in  1897,  describes  the  stratigraphy  and  petrology  of  the 
Sudbury  nickel  district  of  Canada.  The  oldest  rocks  of  the  district 
are  gneisses  of  various  kinds,  which  are  regarded  as  of  Laurentian 
age.  Next  in  age  to  the  gneisses  is  a  belt  of  rocks  consisting  of 
quartzite,  graywacke,  amphibolite,  mica  schist,  phyllite,  clay  slate, 
and  altered  volcanic  breccia,  which  extends  from  the  north  shore  of 
Lake  Huron  northeastward  to  Lake  Mistassini,  in  the  neighborhood 
of  Sudbury,  the  belt  being  about  25  miles  wide.  The  rocfe  of  this 
belt  are  believed  to  be  of  Huronian  age.  The  Huronian  rocks  have 
suffered  severe  metamorphism,  and  the  original  character  of  many  of 
them  can  not  be  made  out.  In  and  adjoining  the  Huronian  belt  are 
elliptical  areas  of  later  eruptive  greenstone,  in  places  intimately 
associated  with  and  genetically  inseparable  from  gneissoid  and  micro- 
pegmatitic  granites.     The  nickel  ore,  principally  pyrrhotite,  occurs 
