Central Baffin electromagnetic experiment (CBEX) maps the NACP in the Canadian arctic.
Evans, S., A.G. Jones, J. Spratt and J. Katsube
Over the summers of 2001 and 2002 a 45 station, 500-km-long regional magnetotelluric
profile was acquired on central Baffin Island in the eastern Canadian arctic.
This Central Baffin electromagnetic experiment (CBEX) profile traverses the northern
margin of the Paleoproterozoic Trans-Hudson Orogen. In its southern segment, within
the juvenile rocks of the orogen, the profile lies on Paleoproterozoic metasedimentary
strata known as the Piling Group, and the profile extends northwards onto the Archean
Rae craton. The primary goal of the experiment was to determine the subsurface geometry
of major geological boundaries and to define regional electrical structures.
Field observations and laboratory analyses show that one particular horizon within
the Piling Group, the sulphidic-graphitic Astarte River Formation, is highly conductive
and can be mapped and used as structural proxy for the base of the Piling Group.
The laboratory results imply that the source of the enhanced conductivity in the
Astarte River Formation is the high content of interconnected graphite, and that the
graphite is highly anisotropic. Mapping this formation in depth images the base of
the Piling Group basin well. There is high contrast in electrical conductivity between
the Piling Group metasedimentary rocks and the Archean granites and gneissic complexes
of the Rae craton to the north. The lower crust of the Rae craton in this area is
moderately conductive (some 100s ohm.m), in contrast to Rae lower crust observed
elsewhere in Canada, and this observation is not readily explained.
The lithospheric mantle beneath the profile exhibits a strong north-to-south gradient
in decreasing resistivity, suggesting resistive Archean mantle (>3,000 ohm.m) subducted
beneath moderately resistive Proterozoic mantle (300 ohm.m).
Physics of the Earth and Planetary Interiors, volume, accepted, 29 March, 2004.
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Alan G Jones / 10 June 2004 /