Active and passive seismic imaging of the central Abitibi greenstone
belt, Larder Lake, Ontario
Abstract
Passive seismic methods are considered as cost-effective and
environmental-friendly alternatives to active (reflection) seismic
methods. We have acquired co-located active and passive seismic surveys
over a metal-endowed Archean granite-greenstone terrane in the Larder
Lake area to investigate the reliability of the estimated elastic
properties using the passive seismic methods. The passive seismic data
was processed using two different data processing approaches, the
ambient noise surface wave tomography (ANSWT) and receiver function
analysis methods to generate shear-wave velocity and P- to S-wave (P-S)
convertibility profiles of the subsurface, respectively. The
Cadillac-Larder Lake Fault (CLLF) was imaged as a south-dipping
sub-vertical zone of weak reflectivity in the reflection seismic
profile. To the north of the CLLF, a package of north-dipping
reflections in the upper-crust (at depths of 5-10 km) resides on the
boundary of high (on the top) and low (on the bottom) shear-wave
velocity zones estimated using the ANSWT method. This package of
reflections is most likely caused by overlaying mafic volcanic and
underlying felsic intrusive rocks. The P-S convertibility profile imaged
the Moho boundary at ~40 km depth as well as a
south-dipping slab that penetrates into the mantel which was interpreted
to be either caused by the delamination of the lower crust or a possible
deeper extension of the Porcupine-Destor Fault. Overall, the
reflectivity, shear-wave velocity, and P-S convertibility profiles
exhibited a good correlation and provided a detailed image of the
subsurface lithological structure to a depth of 10 km.