Ar40-Ar39 Dating of the Lasard River Mafic Dykes, and Implications for the Focus of the 0.72 Ga Franklin Large Igneous Province of Northern Canada

Details Ar40-Ar39 Dating of the Lasard River Mafic Dykes, and Implications for the Focus of the 0.72 Ga Franklin Large Igneous Province of Northern Canada Ar40-Ar39 Dating of the Lasard River Mafic Dykes, and Implications for the Focus of the 0.72 Ga Franklin Large Igneous Province of Northern Canada

May 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agusm.v43a..07e&link_type=abstract

American Geophysical Union, Spring Meeting 2004, abstract #V43A-07

Other

8109 Continental Tectonics: Extensional (0905), 8121 Dynamics, Convection Currents And Mantle Plumes, 8434 Magma Migration, 8450 Planetary Volcanism (5480)

Scientific paper

The Franklin magmatic event represents one of the most extensive Large Igneous Provinces (LIPs) (www.largeigneousprovinces.org) in Canada. Its main elements are the Natkusiak volcanics of Victoria Island, Coronation sills of the Canadian mainland, and a dramatic dyke swarm extending for >1200 km across the Arctic Islands and northwestern Greenland. Precise U-Pb ages for the Franklin dykes range from 723-716 Ma. The swarm exhibits a weak fanning pattern whose point of convergence in the western Arctic, the probable site of a mantle plume, has been poorly defined. Defining the plume centre is important for interpreting the pattern of sedimentation associated with domal uplift above the plume, understanding the magmatic plumbing system for the event, and identifying other dyke sets that are part of the radiating swarm. The location of the plume centre can be better established if an additional component of the Franklin swarm's radiating pattern is identified on the mainland. Possible candidates include the NNW trending Lasard River and N-NNE trending Bebensee Lake (Hottah) dykes. The Lasard River dykes extend at least 350 km south from the Arctic coast within and immediately west of the Brock Inlier. We report a precise 708+/-4 (2-sigma) Ma age on hornblende separates from a syenite phase of a Lasard River dyke. This is interpreted to date dyke emplacement and suggests that the Lasard River dykes are part of the 723-716 Ma Franklin event. The slightly younger age for the Lasard River dykes may reflect the different dating methods used or may indicate that the Lasard River dykes are rift-related (younger dykes associated with other Large Igneous Provinces often exhibit such an association.) The combined Brock Inlier and Franklin swarms define a 720-710 Ma plume centre location northwest of Banks Island (130 W, 75 N). This result needs to be tested with a precise date on the Bebensee Lake dykes to determine whether they are also part of the Franklin event. If so, a plume centre further east would be suggested.

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