Included blocks and blocks within blocks in the

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’ (www. union. edu/PUBLIC/GEODEPT/hollocher/skaergaard/

Skaergaard layering 1) Modally graded layers 2) Uniform/isomodal layers Fig 4: Modally graded and uniform layers (www. union. edu/PUBLIC/GEODEPT/hollo cher/skaergaard/ ) 4) Micro-rhythmic layers 3) Macro-rhythmic layers Fig 5: Macro-rythmic layers (www. union. edu/PUBLIC/GEODEPT/hollocher/s kaergaard/ ) Fig 6: Micro-rhythmic layers (www. union. edu/PUBLIC/GEODEPT/hollocher/skaergaard/ )

Blocks and Block Structures 1) Streamlining 2) Block impact structures Fig 7: Steamlining (Geological Society of America Bulletin, November, pg 1420) 3) Fragmental layers Fig 8: Block impact structures (Origins of igneous layering, Ian Parsons, pg 218) 4) Trough layering structures Fig 9: Fragmental layers (www. union. edu/PUBLIC/GEODE PT/hollocher/skaergaard/ ) Fig 10: Fragmental layers (Geological Society of America Bulletin, November, pg 1420)

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)

Conclusion Fig 13: Processes occuring in the western hal fof the Skaergaard magma chamber (Geological Society of America Bulletin, November 1998 pg 1442)

Comparison with Bushveld Igneous complex Bushveld Skaergaard Location South Africa Greenland Age Precambrian Eocene Size 66 000 km 2 100 km 2 Shape Flat funnel Oval Magma injection Repeated Single System and magma movement Open feeder, non convecting Closed feeder, convecting Layering horizontal, rhythmic modally graded concentric, rhythmic modally graded Blocks uncommon Value economic- platinum (chrome) scientific - “type locality”

Thank –you!