Electromagnetic Images of a Stike-Slip Fault: The Tintina Fault
Zone-Northern Canadian Cordillera
Ledo, J., A.G. Jones and I.J. Ferguson
Wideband magnetotelluric (MT) data were acquired along three profiles
crossing the strike-slip Tintina Fault in northwestern Canada. The two
regional profiles were separated by more than 350 km along strike, and
were designed to obtain crustal scale electromagnetic images of the fault.
A short, higher station density profile, designed to obtain superior
resolution of upper crustal features, was located 35 km south of the
northern profile. The MT responses obtained exhibit remarkable similarity
from all three profiles, implying similar two-dimensional (2-D)
electromagnetic behavior of the fault zone over a strike length of at
least 350 km. Analyses of the MT responses for dimensionality corroborate
the validity of assuming regional 2-D structures in interpretation.
Several high conductivity anomalies at different depth scales are present
in the models obtained, and we suggest that both the shallow structures
and the deep crustal scale anomalies are caused by electronic conduction
mechanisms in interconnected mineralized zones. Intriguingly, the middle
and lower crust beneath the surface expression of the Tintina Fault is
highly resistive, in contrast to some other large-scale strike-slip
faults. This implies that fault zone processes that result in
interconnected conducting phases are not generic in nature but are
controlled by local conditions.
Geophysical Research Letters, 29 (8), doi: 10.1029/2001GL013408, 2001.
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Alan G Jones / 10 June 2004 /