Seimic tomographic images of the cratonic upper mantle beneath the Canadian Western Superior Province: a remnant Archean Slab?
Seimic tomographic images of the cratonic upper mantle beneath the Canadian Western Superior Province: a remnant Archean Slab?
Broadband digital data of the Lithoprobe TW~ST experiment
were tomographically inverted for upper-mantle P and S velocity structures
beneath the Western Superior Province ( see map).
The resulting tomographic images reveal three robust velocity anomalies:
(i) a dipping tabular high-velocity anomaly, (ii) a relatively shallow
low-velocity anomaly directly above the positive anomaly; and (iii) a deep
low-velocity body. The first anomaly could be interpreted as a 30-50 km
thich eclogite/dunite layer representing a remnant subducted oceanic lithosphere.
Resolution tests suggest that this dipping high-velocity anomaly could
extend to the vicinity of the 660 km discontinuity. The low-velocity anomalies
may be related to processes that occured at the edges of the descending
slab or may be expressions of later upwelling material.
