Included blocks _and blocks within blocks_ in the Skaergaard by gyvwpsjkko


									 Included blocks (and blocks within
blocks) in the Skaergaard intrusion:
Geologic relations and the origins of
   rhythmic modally graded layers

     By T. Neil Irvine, Jens Christian
      Andersen and C. Kent Brooks
Autolith blocks and rhythmic
modally graded layers in the
   Skaergaard intrusion
 Presented by: Angelique Laurie
  The Skaergaard intrusion:
Introduction and emplacement

    Fig 1: Skaergaard emplacement (Geological Society of America,
         November, pg 1401)
       Skaergaard : Series’
• Layered Series
• Marginal Series
• Upper Border Series
     The Skaergaard intrusion: Series’

Fig 2: Skaergaard shape and series’ (Origin of
     Igneous Layering edited by Ian Parsons, pg 205)
                                                                     Fig 3: Skaergaard Series’
                     Skaergaard layering

                                              1) Modally graded layers

                                              2) Uniform/isomodal layers

   Fig 4: Modally graded and uniform layers
   cher/skaergaard/ )                              4) Micro-rhythmic layers

    3) Macro-rhythmic layers

Fig 5: Macro-rythmic layers
kaergaard/ )                                      Fig 6: Micro-rhythmic layers
                                                  ( )
           Blocks and Block Structures
      1) Streamlining                                    2) Block impact structures

 Fig 7: Steamlining (Geological Society of America
 Bulletin, November, pg 1420)                             Fig 8: Block impact structures (Origins of igneous layering, Ian
              3) Fragmental layers                        Parsons, pg 218)

                                                                               4) Trough layering

Fig 9: Fragmental layers              Fig 10: Fragmental layers (Geological Society of
(           America Bulletin, November, pg 1420)
PT/hollocher/skaergaard/ )
Deposition of modally sorted layers
1) Boundary flow seperation and reattachment

          Fig 11: S-R cell (Geological Society of America Bulletin, November,
          pg 1438)
Deposition of modally sorted layers
2) Density surge currents

      Fig 12:Density surge currents (Geological Society of America
      Bulletin, November, pg 1438)

Fig 13: Processes occuring in the western hal fof the Skaergaard magma
     chamber (Geological Society of America Bulletin, November 1998 pg
Comparison with Bushveld Igneous
                          Bushveld                  Skaergaard
Location          South Africa                  Greenland
Age               Precambrian                   Eocene
Size              66 000 km2                    100 km2
Shape             Flat funnel                   Oval
Magma injection   Repeated                      Single
System and        Open feeder,                  Closed feeder,
magma movement    non convecting                convecting
Layering          horizontal,                   concentric,
                  rhythmic modally graded       rhythmic modally graded
Blocks            uncommon                      common
Value             economic- platinum (chrome)   scientific - “type locality”
Thank –you!

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