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Conditions of Mineral Deposition Related to Super-Eruptions Abstract  

In  the  world  today  we  place  a  heavy  reliance  on  technology  to  complete  tasks  

that  would  otherwise  be  impossible  to  accomplish.  However,  it  is  often  forgotten  

that  in  order  to  make  certain  machinery  and  devices  function,  precious  metals  such  

as  gold  and  silver,  along  with  other  rare  earth  elements  (REEs)  are  needed.  

Determining  the  locales  of  such  elements  is  vital  to  helping  the  United  States  stay  at  

the  forefront  of  technological  advancements,  now,  as  well  as  in  the  future.  Large  

silicic  magma  bodies  are  one  such  location  that  play  host  to  transporting  these  

precious  metals  close  to  the  surface  via  volcanic  activity  where  they  can  be  mined.  

This  depth  is  similar  to  depths  that  geothermal  systems  exist  and  are  mined  for  

their  heat  resource.  Lake  City  caldera  in  Lake  City,  Colorado  is  a  perfect  place  to  

observe  both  precious  metals  transported  near  the  surface  and  an  extinct  

geothermal  system,  due  to  the  fact  there  is  an  exposed  hydrothermal  system  that  

emerged  following  a  super-­‐eruption.  This  unique  location  allows  us  to  examine  

temperatures  at  which  the  geothermal  system  existed,  and  compositions  (including  

REEs  and  precious  metals)  of  fluids  in  the  quartz  veins  in  order  to  see  what  the  

conditions  of  the  system  were  at  the  time  of  cooling  along  with  the  concentrations  of  

precious  metals  in  the  fluid.  

 

             

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Hypothesis  1:  Fossil  hydrothermal  system  formed  at  high  temperature  and  salinity  as  the  result  of  a  significant  shallow  magmatic  fluid  input.  Hypothesis  2:  Precious  metals  were  concentrated  in  the  magmatic  fluid  induced  by  caldera  collapse.  

Project  Description  

  Lake  City  caldera,  located  in  Lake  City,  Colorado  is  the  youngest  of  15  Tertiary  

calderas  located  in  the  San  Juan  Volcanic  Field  of  Southwestern  Colorado  and  formed  

22.93±0.02  Ma  (Steven  &  Lipman,  1976).  The  area  is  dominated  by  severe  topographic  

relief  and  post-­‐caldera  resurgence  exposed  over  2km  of  uplifted,  intracaldera  Sunshine  

Peak  Tuff  along  with  several  magmatic  intrusions.  Within  Lake  City  caldera  large  

pyroclastic  and  intrusive  rocks  are  quite  exposed,  providing  evidence  for  a  large,  

evolving,  magmatic  system.  (Kennedy  et.  al,  2012).  Shortly  after  caldera  collapse,  a  large  

hydrothermal  system  formed  and  subsequent  hydrothermal  alteration  of  some  of  the  

rock  within  the  caldera  occurred  (Larson  &  Taylor,  1986).  

  For  this  project  I  propose  to  focus  my  study  on  quartz  veins  in  the  Lake  City  

caldera  in  an  effort  to  determine  the  temperature  and  composition  of  the  magmatic  

fluid  present  at  the  time  of  caldera  collapse.  It  has  already  been  observed  that  ore  

deposits  are  present  in  at  least  the  Southwest  and  Northeast  portions  of  the  caldera  

(Woolsey,  1907).  Meteoric  water  being  introduced  to  the  system  represents  the  only  

plausible  way  to  achieve  hydrothermal  alteration  (Larson  and  Taylor,  1986),  and  is  

thought  to  be  responsible  for  the  precipitation  of  rare  Earth  elements  (REEs)  from  the  

magma  (Audétat  et.  al  1998),  so  I  expect  to  find  measurable  amounts  of  REEs  and  

precious  metals  within  the  quartz  veins.    

  After  samples  have  been  collected,  I  will  bring  them  back  to  UW-­‐Oshkosh  where  

I  will  sort  them  and  pick  the  best  samples  for  further  analysis.  Eight  to  ten  quartz  vein  

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samples  will  be  made  into  thick  (200um)  microscope  slides,  which  is  necessary  for  

using  the  fluid  inclusion  heating  and  cooling  stage  here  at  UW-­‐Oshkosh.  Once  the  

temperature  and  salinity  have  been  determined  for  these  samples,  I  will  travel  to  ETH-­‐

Zurich  to  analyze  the  fluid  inclusions  for  their  REE  and  precious  metal  concentrations.  

The  combination  of  temperature  and  chemical  data  from  the  fluid  inclusions  will  help  

me  to  determine  the  conditions  (P-­‐T)  of  formation  and  whether  or  not  metals  were  

transported  at  the  time  of  caldera  collapse  (see  hypotheses  above).  

METHODOLOGY    

This  project  will  involve  several  research  techniques,  including  background  research,  

fieldwork,  sample  preparatory  work,  and  laboratory  work.    

• Background  research  is  being  done  currently  and  will  continue  to  be  done  by  

examining  papers  that  deal  with  Lake  City  caldera  in  order  to  give  myself  a  good  

knowledge  of  the  area  before  data  collection  begins.    

• Fieldwork  will  be  a  very  important  component  of  this  project  and  will  involve  

the  collection  of  samples  from  quartz  veins  around  the  Lake  City  caldera.  

Enough  samples  will  be  gathered  from  representative  areas  so  that  a  

representative  data  set  can  be  achieved.    

• Sample  preparatory  work  involves  sorting  through  collected  samples  upon  

return  from  Colorado  to  determine  which  will  be  sent  off  to  Vancouver  GeoTech  

to  be  turned  into  thick  sections.  

• The  heating  and  cooling  stage  will  heat  the  crystals  up  to  the  temperature  at  

which  they  formed,  where  a  temperature  reading  can  be  obtained,  along  with  

the  salinity  of  the  fluid  at  the  time  of  formation.  

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• LA-­‐ICP-­‐MS  will  be  used  for  trace  element  and  precious  metal  analysis.  This  

method  was  chosen,  because  it  is  an  incredibly  accurate  way  of  measuring  the  

trace  element  and  precious  metal  concentration  of  the  crystals.  The  LA-­‐ICP-­‐MS  

can  analyze  the  crystal  in  stages  (Figure  1).    

Figure  1:    A)  An  illustration  of  a  quartz  crystal  with  its  fluid  inclusions  and  how  it  can  be  divided  into  many  stages  for  LA-­‐ICP-­‐MS  in  order  to  tell  a  compositional  story  throughout  the  crystals  formation.      

STUDENT  MOTIVATION  AND  BACKGROUND  

Being  given  a  chance  to  work  with  a  

professor  on  a  student/faculty  collaborative  

research  project  helps  me  better  myself  as  a  

professional  geologist  along  with  giving  me  much  

needed  experience  in  preparation  for  graduate  school,  and  eventually  the  professional  

community.  Not  only  is  it  good  for  me  educationally,  but  also  it  excites  me  personally  

that  I’ll  be  getting  a  chance  to  apply  what  I’ve  learned  in  the  classroom  to  a  real  world  

problem  that  I  find  interesting.  So  far  in  my  academic  career  I’ve  completed  Physical  

Geology,  Evolution  of  the  Earth,  Mineralogy,  Oceanography,  Geomorphology,  and  

Paleontology.  I’m  currently  enrolled  in  Lithology  and  Igneous  &  Metamorphic  Petrology.  

I’ll  be  participating  in  my  first  geology  field  trip  to  Yellowstone  National  Park  this  spring  

interim,  however,  many  of  the  geology  courses  I’ve  already  completed  and  am  enrolled  

in  have  field  trips  associated  with  them.  I’ve  also  been  working  with  Dr.  Chad  Deering  

for  the  past  semester  working  to  set  up  the  fluid  inclusion  heating  and  cooling  stage  

  The  role  of  Dr.  Deering  as  my  mentor  will  be  to  provide  assistance  and  guidance  

as  I  go  throughout  this  project.  He  will  offer  a  helping  hand  as  I  develop  my  skills  as  a  

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professional  geologist  and  tackle  this  project  in  a  scientific,  yet  creative  manner.  This  

project  reflects  a  small  aspect  of  research  that  Dr.  Deering  is  doing,  himself,  on  Lake  City  

Caldera.  Dr.  Deering  will  also  supervise  all  fieldwork,  lab  work,  and  data  analysis  that  I  

accomplish.    

LOCATION  AND  TIMELINE  

1.  Spring,  2013:  Background  research  and  literature  review  is  underway  currently  and  

will  be  completed  later  this  spring.  In  conjunction  with  my  scheduled  classes,  time  will  

be  devoted  throughout  the  course  of  the  semester  to  do  this.  (40-­‐60hrs.)  

2.  Summer,  2013:  Fieldwork  will  be  done  at  Lake  City  Caldera,  which  is  located  in  Lake  

City,  Colorado.  In  late  August  I  will  be  traveling  to  Colorado  with  Dr.  Deering  to  do  the  

fieldwork  component  of  this  experiment.  We  will  be  out  there  roughly  two  weeks  

working  on  collecting  data  and  mapping  the  fossil  geothermal  system  (80-­‐120  hrs.).  

3.  Fall,  2013:  Upon  returning  to  Oshkosh,  chosen  samples  will  be  sent  to  Vancouver  

GeoTech  in  Vancouver,  British  Columbia  where  they  will  be  turned  into  thick  sections  

(10hrs.).  Petrographic  analysis  of  fluid  inclusion  thick  sections  will  be  done  here  at  UW-­‐

Oshkosh  using  the  fluid  inclusion  heating  and  cooling  stage  (50-­‐60hrs.).  

4.  Spring,  2014:  Laser  Ablation-­‐Inductively  Coupled  Plasma-­‐Mass  Spectrometry  (LA-­‐

ICP-­‐MS)  work  will  be  done  at  ETH-­‐Zurich  in  Zurich,  Switzerland.  This  will  take  place  

during  the  January  winter  interim  of  2013-­‐2014  (40-­‐60hrs.).  

5.  Upon  returning  to  UW-­‐Oshkosh,  remaining  Spring  semester  time  will  be  used  to  

process  and  interpret  data.  All  of  my  data  and  findings  will  be  organized  and  prepared  

for  presentations  at  the  Celebration  of  Scholarships  and  GSA  in  the  spring  of  2014.    

OUTCOMES  

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  This  project,  with  its  length,  has  several  predicted  outcomes,  which  include  the  

following:  

• From  collecting  and  analyzing  samples  via  the  heating  and  cooling  stage,  we  will  

create  a  detailed  map  of  the  fossil  geothermal  system  as  it  relates  to  temperature  

and  salinity  of  the  system,  which  can  be  overlain  on  a  previous  map  of  the  

hydrothermal  alteration  minerals  and  oxygen  isotopes  (Larsen  and  Taylor,  

1986).    

• Determine  if  high  concentrations  of  precious  metals  are  precipitated  out  of  the  

magma  when  there  is  a  large,  super-­‐eruption  that  leads  to  caldera  collapse.    

• Presentation  of  results  at  the  Celebration  of  Scholarships  and  GSA  in  the  spring  

of  2014  

• The  learning  of  two  new  techniques  to  extract  trace  element  and  precious  metal  

concentrations  from  fluid  inclusions:  using  the  fluid  inclusion  heating  and  

cooling  stage  and  LA-­‐ICP-­‐MS.  

BUDGET  

  Expenses  for  this  trip  include  the  making  of  thin  sections  at  Vancouver  GeoTech,  

where  the  cost  of  making  one  fluid  inclusion  thick  section  is  $52.00.  I  will  be  sending  8-­‐

10  samples  to  Vancouver  GeoTech.  Dr.  Deering  has  a  funded  NSF  grant  for  studying  the  

plutonic  and  volcanic  rocks  from  Lake  City  caldera.  He  will  provide  all  other  necessary  

support  for  Colorado  fieldtrip  and  travel  accommodations  to  Zurich,  and  the  analyses  at  

ETH,  Zurich.  

 

     

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REFERENCES  CITED    Audétat,  A.,  Günther,  D.,  Heinrich,  C.A.,  1998,  Formation  of  a  Magmatic-­‐Hydrothermal  Ore  Deposit:  Insights  with  LA-­‐ICP-­‐MS  Analysis  of  Fluid  Inclusions:  SCIENCE,  v.  279,  p.  2091-­‐2094    Kennedy,  B.,  Wilcock,  J.,  Stix,  J.,  2012,  Caldera  resurgence  during  magma  replenishment  and  rejunenation  at  Valles  and  Lake  City  calderas:  Springer-­‐Verlag  2012.    Larson,  P.B.,  Taylor,  H.P.  Jr.,  1986,  An  Oxygen  Isotope  Study  of  Hydrothermal  Alteration  in  the  Lake  City  Caldera,  San  Juan  Mountains,  Colorado:  Journal  of  Volcanology  and  Geothermal  Research,  v.  30,  p.  47-­‐82    Steven,  T.A.,  Lipman,  P.W.,  1976,  Calderas  of  the  San  Juan  volcanic  field,  southwestern  Colorado:  USGS  Professional  Paper,  v.  958,  p.  1-­‐35.    Woolsey,  L.H.,  1907,  Lake  Fork  extension  of  the  Silverton  mining  area,  Colorado:  USGS  Bulletin,  v.  315,  p.  26-­‐30  

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February 3, 2013 Student/Faculty Collaborative Research Program Review Board University of Wisconsin-Oshkosh, Office of Grants and Faculty Development Dear Review Board, It is my pleasure to support Jordan Lubbers’ proposal entitled: “Conditions of Mineral Deposition Related to Super-Eruptions”. I am excited to have Jordan pursue this research as it represents the examination of a new set of hypotheses that I have developed regarding how mineral deposits form in relation to caldera collapse associated with large super-eruptions. The results from this project will represent a preliminary dataset that I intend to use to submit a full proposal to either the DOE or NSF in collaboration with colleagues. Jordan is currently in my Lithology course and he has been helping me with various research projects through the STEP program. Jordan has been helping me set up the fluid inclusion heating and cooling stage in our department, which is ultimately what led him to outline and write this proposal. He will continue to gain more field experience (Yellowstone fieldtrip in Spring interim) and learn to use the equipment over the coming months before sample collection begins in August, 2013. Jordan’s project is well within his intellectual capabilities and, given his excellent work ethic, I am confident that he can complete this project. I have mentored a number of BS, MS and PhD students over the past six years. Here at UW-Oshkosh I have mentored five students on independent studies over the past 1.5 years, one of which resulted in the student presenting his results at an International meeting in San Francisco last year. That student is also currently helping to write a manuscript to be submitted to an internationally peer-reviewed journal. I am fully committed to helping Jordan be successful in this project. This project will cost far more than what Jordan is asking for in this proposal; however, I am willing to use funds from a recently awarded NSF grant to supplement the cost of his project. This NSF funded project will be supporting several other student projects aimed at understanding the magmatic system at Lake City caldera – not the geothermal system. However, I selected this location for studying the magmatic system so that I could also begin studying the fossil geothermal system there at the same time to determine the origin of associated mineral deposits. I will support Jordan in several ways that will ensure that he is able to complete the research project by covering the additional costs of: 1) travel and accommodations to Colorado for fieldwork, 2) travel and accommodations to ETH-Zurich in Switzerland, and 3) analytical costs for the Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. Sincerely, Chad Deering, Assistant Professor of Geology