MINERAL    DEPOSITS    OF    NEW    MEXICO.  79 
Next  to  erosion  in  striking  results  undoubtedly  come  movements  of  the  earth's  crust. 
Folding  in  the  strict  sense  has  gone  on  only  to  a  slight  extent  in  New  Mexico,  hut  faulting 
and  doming  are  exceedingly  important. 
The  Rocky  Mountain  core  is  generally  believed  to  have  been  a  land  area  from  pre-Cam- 
brian  to  near  the  close  of  Paleozoic  time.  This  view  is  sustained  in  the  northern  part  of  New 
Mexico  by  the  absence  of  Paleozoic  sediments  older  than  the  Pennsylvanian  series  of  the  Car- 
boniferous. In  he  southwestern  part,  however,  the  sea  was  present  more  or  less  continu- 
ously from  the  beginning  of  Cambrian  time  on.  At  the  end  of  the  Lower  Carboniferous  the 
northern  land  area  was  submerged  and  sedimentation  went  on  throughout  the  Territory, 
possibly  with  some  interruptions,  till  the  close  of  Cretaceous  time.  By  this  time  practically 
the  whole  Territory  was  covered  by  a  thick  mantle  of  Cretaceous  sediments.  Then  followed 
the  great  crustal  movements  which  left  their  impress  on  the  present  topography.  These  move- 
ments were  of  two  kinds.  One  was  an  upthrust  of  pre-Cambrian  rocks  along  north-south 
lines,  producing  longitudinal  faulting  and  bending  up  the  strata  on  the  sides  of  the  ridges  so 
produced.  Step  faulting  with  repetition  of  the  strata  was  a  very  common  result.  These 
phenomena  are  well  shown  along  both  sides  of  the  mountain  belt  from  Santa  Fe  northward, 
especially  along  the  upper  Pecos  and  northwest  of  Las  Vegas.  Faults  undoubtedly  bound 
the  steep  sides  of  the  Sandia,  Manzano,  Oscura,  San  Andreas,  Organ,  and  Franklin  mountains. 
The  other  movement  was  brought  about  by  the  porphyry  intrusions,  which  formed  stocks 
with  some  doming  of  the  strata  in  the  Paleozoic  sediments  and  true  laccoliths  with  very 
decided  doming  in  the  Cretaceous  sediments.  Erosion  has  since  carried  away  the  upper  por- 
tion of  these  domes,  leaving  the  igneous  rocks  exposed.  Many  instances  might  be  cited. 
The  Cerrillos,  Ortiz,  and  San  Pedro  mountains  are  clearly  defined  laccoliths,  while  sediments 
domed  by  intrusive  masses  occur  in  the  White  Oaks,  Elizabethtown,  Pinos  Altos,  and  other 
districts.  No  local  movements  of  orogenic  importance  appear  to  have  taken  place  since  these 
post-Cretaceous  movements,  for  the  Tertiary  sediments  and  flows  remain  practically  undis- 
turbed, but  a  general  Tertiary  uplift  is  indicated  by  the  present  elevation  of  the  country. 
ORE   DEPOSITS. 
GENERAL  FEATURES  OE  THE   MINING   INDUSTRY.  • 
New  Mexico  does  not  rank  very  high  among  the  metal-producing  States  of  the  West. 
According  to  the  last  report  of  the  United  States  Geological  Survey ,a  the  total  value  of 
gold,  silver,  copper,  lead,  and  zinc  produced  in  1904  amounted  to  only  $2,186,287.  On 
the  other  hand,  the  output  of  coal  alone  in  the  same  year  was  about  1,500,000  tons,  of  a 
value  of  $1,900,000.  The  Territory  yielded  only  $381,930  in  gold,  of  which. $149,424  was 
taken  from  placer  mines.  Most  of  this  placer  gold  came  from  Colfax  County,  near  the 
northern  boundary  line,  and  from  the  new  diggings  in  Apache  Canyon,  in  the  south-central 
part  of  Sierra  County.  Lode  mining  of  gold  ores  was  carried  on  chiefly  in  the  Mogollon 
district  and  the  Rosedale  mine  in  Socorro  County,  in  the  Hillsboro  district  in  Sierra  County, 
and  in  the  Silver  City  district  in  Grant  County,  all  in  the  central  or  southwestern  part  of 
the  Territory.  The  silver  ores  yielded  a  value  of  $124,103,  the  Mogollon  district  in  Socorro 
County  and  the  Silver  City  mines  in  Grant  County  leading,  while  Sierra,  Luna,  and  Dona 
Ana  counties  contributed  smaller  amounts. 
The  copper  produced  in  the  Territory  had  a  value  of  $646,382,  the  old  mines  of  Santa 
Rita  and  the  recently  developed  deposits  in  the  Burro  Mountains,  both  in  Grant  County, 
contributing  the  largest  share;  Socorro  County  added  an  amount  of  copper  valued  at 
$55,316  from  the  Mogollon  district.  Lesser  amounts  came  from  the  Organ  Mountains 
in  Dona  Ana  County  and  from  San  Miguel  County. 
The  value  of  the  lead  was  $134,283,  of  which  the  largest  part  came  from  the  mines  in 
the  Organ  Mountains  in  Dona  Ana  County;  smaller  amounts  were  derived  from  the  Cooks 
a  Jones,  F.  A.,  Mineral  Resources,  U.  S.,  for  1904,  U.  S.  Geol.  Survey,  1905,  pp.  200-203. 
