March 22nd 2010 – GAC Cordillera / TGI-3 workshop, Vancouver <br /> Distribution and Thickness of Volcanic and Glacial Cov...
Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Pla...
Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Pla...
It obscures basement likely to host Cu-Au-Mo porphyryand epithermal Au deposits.
The CG is wholly within the MPBB infestation zone.
It is extensively covered by ?? m of drift.</li></ul>Nicola Arc<br />Cariboo Mountains<br />Cariboo Mountains<br />Interio...
Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Pla...
It obscures basement likely to host Cu-Au-Mo porphyryand epithermal Au deposits.
The CG is wholly within the MPBB infestation zone.
It is extensively covered by ?? m of drift.</li></ul>It’s thickness and distribution are very poorly constrained.<br />Nic...
Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Pla...
It obscures basement likely to host Cu-Au-Mo porphyryand epithermal Au deposits.
The CG is wholly within the MPBB infestation zone.
It is extensively covered by ?? m of drift.</li></ul>It’s thickness and distribution are very poorly constrained.<br />Nic...
Regional Geology - MINFILE<br />WL<br />100<br />
Regional Geology - MINFILE<br />Mt Polley<br />Gibraltar<br />???<br />WL<br />???<br />???<br />Takomkane<br />???<br />1...
Chilcotin Group – typical exposure<br />Andrews and Russell (2007)<br />sub-aerial lavas<br />e.g. Hanceville<br />sub-aqu...
e.g. Chilcotin River / HWY 20<br />e.g. Chasm Provincial Park<br />
Chilcotin Group – typical exposure<br />e.g. Chasm Provincial Park<br />Farrell et al (2010) – GSC OF6230<br />
Common Wisdom?<br />Assumed to be an extensive and thick (100 – 200 m), homogeneous sheet.<br />This is the least favorabl...
e.g. Nazko River Valley<br />evidence for river valleys<br />till - overburden<br />~6.3 Ma columnar-jointed lava<br />4 m...
evidence for river valleys<br />e.g. Vedan Lake Valley<br />lava<br />Basalt-buried Miocene channels are known locations o...
mapping valley-fill successions<br />valley margin<br />~2 km<br />valley axis<br />e.g. Bull Canyon Prov. Park<br />Gorde...
mapping valley-fill successions<br />valley margin<br />subaerial lava<br />characteristic orange     pillow-breccias<br /...
exposed paleovalleys – 3 Ma Chilcotin River<br />e.g. Chilcotin River / HWY20<br />
a new facies model<br />A valid geological model for the Chilcotin basalts must include:<br />Significant paleo-relief, pr...
Upcoming SlideShare
Loading in …5
×

Andrews GAC-TGI3_March2010.pptx

350 views

Published on

Presentation from the TGI3 workshop hosted by GAC-Cordillera, March 2010, Vancouver BC

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
350
On SlideShare
0
From Embeds
0
Number of Embeds
2
Actions
Shares
0
Downloads
3
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Andrews GAC-TGI3_March2010.pptx

  1. 1. March 22nd 2010 – GAC Cordillera / TGI-3 workshop, Vancouver <br /> Distribution and Thickness of Volcanic and Glacial Cover on the Interior Plateaus <br />Graham Andrews – GSC Vancouver<br />Graham.Andrews@NRCan-RNCan.gc.ca<br />Kelly Russell – UBC Vancouver<br />krussell@eos.ubc.ca<br />
  2. 2. Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Plateaus.</li></ul>Nicola Arc<br />Cariboo Mountains<br />Cariboo Mountains<br />Interior Plateaus<br />Coast Mountains<br />adapted from Massey (2006)<br />
  3. 3. Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Plateaus.
  4. 4. It obscures basement likely to host Cu-Au-Mo porphyryand epithermal Au deposits.
  5. 5. The CG is wholly within the MPBB infestation zone.
  6. 6. It is extensively covered by ?? m of drift.</li></ul>Nicola Arc<br />Cariboo Mountains<br />Cariboo Mountains<br />Interior Plateaus<br />Coast Mountains<br />adapted from Massey (2006)<br />
  7. 7. Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Plateaus.
  8. 8. It obscures basement likely to host Cu-Au-Mo porphyryand epithermal Au deposits.
  9. 9. The CG is wholly within the MPBB infestation zone.
  10. 10. It is extensively covered by ?? m of drift.</li></ul>It’s thickness and distribution are very poorly constrained.<br />Nicola Arc<br />Cariboo Mountains<br />Cariboo Mountains<br />Interior Plateaus<br />Coast Mountains<br />adapted from Massey (2006)<br />
  11. 11. Mineral Deposits in south-central BC<br /><ul><li>The Chilcotin Group (~22 – 0.1 Ma) covers >35,500 km2of the Interior Plateaus.
  12. 12. It obscures basement likely to host Cu-Au-Mo porphyryand epithermal Au deposits.
  13. 13. The CG is wholly within the MPBB infestation zone.
  14. 14. It is extensively covered by ?? m of drift.</li></ul>It’s thickness and distribution are very poorly constrained.<br />Nicola Arc<br />Cariboo Mountains<br />Cariboo Mountains<br />STUDY AREA<br />Coast Mountains<br />adapted from Massey (2006)<br />
  15. 15. Regional Geology - MINFILE<br />WL<br />100<br />
  16. 16. Regional Geology - MINFILE<br />Mt Polley<br />Gibraltar<br />???<br />WL<br />???<br />???<br />Takomkane<br />???<br />100<br />Thuya<br />???<br />Blackdome<br />Prosperity<br />
  17. 17. Chilcotin Group – typical exposure<br />Andrews and Russell (2007)<br />sub-aerial lavas<br />e.g. Hanceville<br />sub-aqueous pillow delta<br />subaerial lavas<br />Eocene rocks<br />subaqueous breccias<br />e.g. Chilcotin River / HWY 20<br />Extensive sub-aerial / sub-aqueous successions along the tributaries of the Fraser River.<br />Complex horizontal stratigraphic transitions between sub-aerial and sub-aqueous lithofaciesat the margins of paleovalleys.<br />
  18. 18. e.g. Chilcotin River / HWY 20<br />e.g. Chasm Provincial Park<br />
  19. 19. Chilcotin Group – typical exposure<br />e.g. Chasm Provincial Park<br />Farrell et al (2010) – GSC OF6230<br />
  20. 20. Common Wisdom?<br />Assumed to be an extensive and thick (100 – 200 m), homogeneous sheet.<br />This is the least favorable geological model for successful, low-risk exploration.<br />???<br />Chilcotin Group - lavas<br />Basement<br />???<br />what’s observed<br />what’s inferred<br />Andrews & Russell (2007)<br />
  21. 21. e.g. Nazko River Valley<br />evidence for river valleys<br />till - overburden<br />~6.3 Ma columnar-jointed lava<br />4 m<br />sediment diapir soft-sed deformation<br />≤3 m<br />bedded lacustrine sediments <br />
  22. 22. evidence for river valleys<br />e.g. Vedan Lake Valley<br />lava<br />Basalt-buried Miocene channels are known locations of basal U deposits (e.g., Blizzard site, near Kelowna, BC).<br />Basalt-buried channels are knownhosts for placer Au deposits<br />most Cariboo placers are Miocene or Pliocene<br />hydro-volcanic breccia<br />river gravels<br />
  23. 23. mapping valley-fill successions<br />valley margin<br />~2 km<br />valley axis<br />e.g. Bull Canyon Prov. Park<br />Gordee et al. (2007)<br />
  24. 24. mapping valley-fill successions<br />valley margin<br />subaerial lava<br />characteristic orange pillow-breccias<br />e.g. Bull Canyon Prov. Park<br />Gordee et al. (2007)<br />
  25. 25. exposed paleovalleys – 3 Ma Chilcotin River<br />e.g. Chilcotin River / HWY20<br />
  26. 26. a new facies model<br />A valid geological model for the Chilcotin basalts must include:<br />Significant paleo-relief, probably similar to today;<br />Thick sections in paleo-drainages, thin sections over paleo-highs;<br />Varied lithofacies – related to paleo-environment;<br />Basement windows “poke” through the basaltic cover. <br />hydro-volcanic breccia<br />subaerial lava<br />Andrews & Russell (2007)<br />
  27. 27. implications: areal extent<br />Dohaney MSc (2009)<br />
  28. 28. implications: areal extent<br />Dohaney MSc (2009)<br />
  29. 29. implications: areal extent<br />Up to 50% reduction in mapped Chilcotin Group extent<br />?<br />?<br />?<br />?<br />Dohaney MSc (2009)<br />
  30. 30. implications: areal extent<br />Dohaney et al (2010) – GSC OF6344 & OF6284<br />
  31. 31. implications: buried paleochannels<br /><ul><li> BC Prov. Govt. water-well log data
  32. 32. CG locally up to 50 m thick around 100 Mile House and Vanderhoof
  33. 33. typically <20 m elsewhere
  34. 34. can also constrain drift thickness and bedrock type</li></ul>Vanderhoof<br />Andrews et al - CJES paper and GSC OF in 2010<br />
  35. 35. implications: buried paleochannels<br />Prince George<br />100 Mile House<br />Andrews et al (subjudice)<br />Andrews et al - CJES paper and GSC OF in 2010<br />
  36. 36. summary<br />Extreme thickness variations (0 – 100 m) require many ‘basement windows’ and greatly reduced areal extent.<br />Andrews et al - CJES (subjudice)<br />
  37. 37. summary<br />Extreme thickness variations (0 – 100 m) require many ‘basement windows’ and greatly reduced areal extent.<br />Identifying paleo-drainages (esp. Pliocene / Pleistocene) reveals major drainage direction changes  what are the implications for regional-scale detrital mineral / till and geochemical sampling? --- POTENTIALY A BIG PROBLEM!!!<br />
  38. 38. Thank you – questions?<br />

×