226  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.        [bull.  260. 
About  40  miles  east  of  the  Rio  Grande  Valley,  in  New  Mexico,  is 
a  disconnected  series  of  mountain  ranges  along  a  common  line  of  up- 
lift, known  in  various  parts,  proceeding  from  south  to  north,  as  the 
Franklin  Range,  San  Andreas  Mountains,  Sierra  Oscura,  and  the 
Sandia  Mountains.  In  these  some  rather  singular  deposits,  resem- 
bling but  not  entirely  analogous  to  the  above,  have  been  noted  by  j 
Peters,  Herrick,  and  Turner. 
The  deposits  in  the  Sierra  Oscura  were  described  by  E.  D.  Peters 
in  1882.a  and  later  by  H.  W.  Turner,  1902.5  They  occur  along  the 
east  flanks  of  the  range,  in  red  beds  which  lie  between  Carboniferous 
limestones  below  and  red  sandstones  and  shales  above,  the  latter  be- 
ing thought  by  Turner  to  resemble  the  Permian  of  western  Texas. 
These  beds  dip  eastward,  away  from  the  granite  core  of  the  range. 
The  copper  ore  occurs  in  beds  of  arkose  sandstone  and  of  shale,  two 
ore-bearing  horizons  being  recognized  in  the  former.  The  ore  con- 
sists mainly  of  glance  and  carbonate  in  minute  grains  disseminated 
through  the  rock;  also  in  nodules,  especially  in  the  shales,  which  often 
have  a  kernel  of  sulphide,  chalcopyrite,  bornite,  or  chalcocite;  like- 
wise replacing  plant  remains.  Among  the  latter  Peters  recognized 
the  form  characteristic  of  the  Abiquiu  quarries  (Podozamites  crassi- 
folia).  The  arkose  sandstones  contain  rolled  grains  of  iron  oxide, 
in  part  magnetic.  Deposits  of  chalcopyrite  are  found  on  certain 
fault  fissures  cutting  the  beds,  but  Turner  thinks  the  ores  were  de- 
posited prior  to  the  main  faulting  of  the  region,  and  that  the  copper 
was  precipitated  from  the  waters  in  which  the  inclosing  sediments 
were  laid  down. 
C.  L.  Herrick,  writing  in  1898,c  describes  the  occurrence  in  the  San 
Andreas  Mountains,  as  well  exposed  in  the  abrupt  escarpments  due 
to  faulting  on  the  east  side  of  the  range,  which  afford  frequent  and; 
good  exposures. 
The  Carboniferous  limestones,  which  rest  on  granite,  are  cut  atr 
intervals  of  half  a  mile  or  more  by  a  series  of  vertical  veins  from  5  to 
20  feet  thick.  These  veins,  which  carry  various  metallic  minerals 
in  a  gangue  of  quartz,  fluorspar,  calcite,  siderite,  or  barite,  can  be 
traced  to  the  contact  with  the  granite,  but  do  not  appear  to  have 
entered  the  latter  rock.  There  is  a  thin  band  of  red  sandstone  ati 
the  contact,  in  which  has  accumulated  a  bed  of  hematite  carry mgi 
copper  ores  consisting  of  glance,  malachite,  cuprite,  etc.  The  copper 
does  not  occur  to  any  considerable  extent  in  the  limestone  above  or 
the  granite  below.  Without  explicitly  stating  his  reasons,  Herrickfft 
assumes  that  the  iron  ores  in  this  band  have  leached  down  from  above 
but  that  the  copper  came  up  from  the  depths. 
11 
li, 
°  Eng.  and  Min.  Jour.,  vol.  34,  p.  270. 
6  Trans.  Am.  Inst.  Min.  Eng.,  vol.  33,  p.  678. 
c  Am.  Geol.,  vol.  22,  pp.  285-291. 
