New insights into the structure of the Sudbury Igneous Complex from downhole seismic studies

Abstract

New vertical seismic profiles from the northwest margin of the Sudbury impact structure provide details of structural geometries within the lower impact melt sheet (usually called the Sudbury Igneous Complex) and the sublayer norite layer. Vertical seismic profile sections and common depth point transformation images display several continuous reflections that correlate with faults and stratigraphic boundaries logged from drill cores. Of four possible mechanisms that explain repeated rock units, late-stage flow or normal faulting that occurred within the last layers to cool and crystallize might best explain the observations, especially the most prominent reflectors observed in the seismic data. These results reaffirm previously proposed two-stage cooling and deformation models for the impact melt sheet.

Structural characteristics of the Sudbury impact structure, Canada: Impact-induced versus orogenic deformation-A review

“…The lack of pervasive mesoscopic strain fabrics in the North Range of the SIC and its Archean host rocks may indicate that these rocks were tilted coherently during Penokean tectonism. This is corroborated by the structural continuity of the lower contact of the North Range of the SIC in seismic images (Milkereit et al 1992; but see also Snyder et al 2002) and Fig. 6.…”

Lithology classification from seismic tomography: Additional constraints from surface waves

“…7 and 9), where high values are observed for all three types of seismic velocities (above 5.7-6.2 km/s for P-waves, 2.5-2.9 km/s for surface waves, 3.0-3.5 km/s for S-waves). These values are consistent with seismic velocities observed at similar intrusive complexes (e.g., Snyder et al, 2002).…”

Regional study of the Archean to Proterozoic crust at the Sudbury Neutrino Observatory (SNO+), Ontario: Predicting the geoneutrino flux

“…The density of the SIC is obtained from drill core information published by Snyder et al . [] and Milkereit et al . [].…”

“…The thickness of several regionally distributed granitic to granodioritic intrusions were estimated using reflection seismic surveys. The structure of the SIC has been extensively explored [e.g., Milkereit et al ., ; Boerner et al ., ; Snyder et al ., ] and existing seismic surveys are sufficient to constrain the SIC precisely. Some extrapolations regarding the thickness of the volcanic to metavolcanic rocks in the Abitibi greenstone belt were made based on existing geological cross sections in order to estimate their thickness in areas lacking direct observations.…”